One of the research challenges in cellular networks is the design of an efficient model that can reduce call
blocking probability and improve the quality of service (QoS) provided to mobile users. Blocking occurs
when a new call cannot be admitted into the network due to channel unavailability caused by limited
capacity or when an ongoing call cannot be continued as it moves from one base station to another due to
mobility of the user. The proposed model computes the steady state probability and resource occupancy
distribution, traffic distribution, intra-cell and inter-cell interferences from mobile users. Previously
proposed models are reviewed through which the present model is built for use in emerging wireless
networks so as to obtain improved QoS performance. The developed model is validated through simulations
in MATLAB and its equations implemented using Java Programming Language. The results obtained
indicate reduced call blocking probability below threshold.
QoS Based Capacity Enhancement for WCDMA Network with Coding SchemeVLSICS Design
The wide-band code division multiple access (WCDMA) based 3G and beyond cellular mobile wireless networks are expected to provide a diverse range of multimedia services to mobile users with guaranteed quality of service (QoS). To serve diverse quality of service requirements of these networks it necessitates new radio resource management strategies for effective utilization of network resources with coding schemes. Call admission control CAC) is a significant component in wireless networks to guarantee quality of service requirements and also to enhance the network resilience. In this paper capacity enhancement for WCDMA network with convolutional coding scheme is discussed and compared with block code and without coding scheme to achieve a better balance between resource utilization and quality of service provisioning. The model of this network is valid for the real-time (RT) and non-real-time (NRT) services having different data rate. Simulation results demonstrate the effectiveness of the network using convolutional code in terms of capacity enhancement and QoS of the voice and video services.
EFFICIENT UTILIZATION OF CHANNELS USING DYNAMIC GUARD CHANNEL ALLOCATION WITH...cscpconf
User mobility in wireless data networks is increasing because of technological advances and the
desire for voice and multimedia applications. These applications, however, require fast handoffs
between base stations to maintain the quality of the connections. In this paper, the authors
describe the use of novel and efficient data structure which dynamically allocates guard channel
for handoffs and introduces the concept of channel borrowing strategy. The proposed scheme
allocates the guard channels for handoff requests dynamically, based on the traffic load for
certain time period. A new originating call in the cell coverage area also uses these guard
channels if they are unused. Our basic idea is to allow Guard channels to be shared between new calls and handoff calls. This approach maximizes the channel utilization. The simulation results prove that the channel borrowing scheme improves the overall throughput.
This is a presentation I did at the pre-Master studies at Ain shams University. It\'s about algorithms and techniques of call admission when a mobile node moves among cell in a wireless network.
Reducing handoff delay by adaptive thresholdijistjournal
In wireless networks data are sent and received with impressive speed and ease. Mobile WiMAX is a
broadband wireless solution that enables coverage of mobile and fixed broadband networks with flexible
network architecture. Devised as a truly broadband access solution, the WiMAX technology offers
promising features in terms of high bandwidth, extended coverage area and low cost. Despite having
many advantages, WiMAX faces major research issues like QoS based bandwidth allocation, Roaming,
Internetworking with other technologies, security and handoff. Handoff occurs when a mobile user goes
from one cell to another without interruption of ongoing session. Many approaches have been proposed
for reducing handoff delay. In this paper, we propose a new approach by which a critical area, an area
far away from serving base station but still inside the coverage of serving base station, is found. And then
overlapping area between serving base stations and neighboring base station are found and tabulated.
According to the size of overlapping area, different weights are assigned where handoff threshold is
changed adaptively to reduce handoff delay.
Performance evaluation of interference aware topology power and flow control ...IJECEIAES
Multi-Radio Multi-Channel Wireless Mesh Network (MRMC-WMN) has been considered as one of the key technology for the enhancement of network performance. It is used in a number of real-time applications such as disaster management system, transportation system and health care system. MRMC-WMN is a multi-hop network and allows simultaneous data transfer by using multiple radio interfaces. All the radio interfaces are typically assigned with different channels to reduce the effect of co-channel interference. In MRMC-WMN, when two nodes transmit at the same channel in the range of each other, generates co-channel interference and degrades the network throughput. Co-channel interference badly affects the capacity of each link that reduces the overall network performance. Thus, the important task of channel assignment algorithm is to reduce the co-channel interference and enhance the network performance. In this paper, the problem of channel assignment has been addressed for MRMC-WMN. We have proposed an Interference Aware, Topology, Power and Flow Control (ITPFC) Channel Assignment algorithm for MRMC-WMN. This algorithm assignes the suitable channels to nodes, which provides better link capacity and reduces the co-channel interference. In the previous work performance of the proposed algorithm has been evaluated for a network of 30 nodes. The aim of this paper is to further evaluate the performance of proposed channel assignment algorithm for 40 and 50 nodes network. The results obtained from these networks show the consistent performance in terms of throughput, delay, packet loss and number of channels used per node as compared to LACA, FCPRA and IATC Channel Assignment algorithms.
QoS Based Capacity Enhancement for WCDMA Network with Coding SchemeVLSICS Design
The wide-band code division multiple access (WCDMA) based 3G and beyond cellular mobile wireless networks are expected to provide a diverse range of multimedia services to mobile users with guaranteed quality of service (QoS). To serve diverse quality of service requirements of these networks it necessitates new radio resource management strategies for effective utilization of network resources with coding schemes. Call admission control CAC) is a significant component in wireless networks to guarantee quality of service requirements and also to enhance the network resilience. In this paper capacity enhancement for WCDMA network with convolutional coding scheme is discussed and compared with block code and without coding scheme to achieve a better balance between resource utilization and quality of service provisioning. The model of this network is valid for the real-time (RT) and non-real-time (NRT) services having different data rate. Simulation results demonstrate the effectiveness of the network using convolutional code in terms of capacity enhancement and QoS of the voice and video services.
EFFICIENT UTILIZATION OF CHANNELS USING DYNAMIC GUARD CHANNEL ALLOCATION WITH...cscpconf
User mobility in wireless data networks is increasing because of technological advances and the
desire for voice and multimedia applications. These applications, however, require fast handoffs
between base stations to maintain the quality of the connections. In this paper, the authors
describe the use of novel and efficient data structure which dynamically allocates guard channel
for handoffs and introduces the concept of channel borrowing strategy. The proposed scheme
allocates the guard channels for handoff requests dynamically, based on the traffic load for
certain time period. A new originating call in the cell coverage area also uses these guard
channels if they are unused. Our basic idea is to allow Guard channels to be shared between new calls and handoff calls. This approach maximizes the channel utilization. The simulation results prove that the channel borrowing scheme improves the overall throughput.
This is a presentation I did at the pre-Master studies at Ain shams University. It\'s about algorithms and techniques of call admission when a mobile node moves among cell in a wireless network.
Reducing handoff delay by adaptive thresholdijistjournal
In wireless networks data are sent and received with impressive speed and ease. Mobile WiMAX is a
broadband wireless solution that enables coverage of mobile and fixed broadband networks with flexible
network architecture. Devised as a truly broadband access solution, the WiMAX technology offers
promising features in terms of high bandwidth, extended coverage area and low cost. Despite having
many advantages, WiMAX faces major research issues like QoS based bandwidth allocation, Roaming,
Internetworking with other technologies, security and handoff. Handoff occurs when a mobile user goes
from one cell to another without interruption of ongoing session. Many approaches have been proposed
for reducing handoff delay. In this paper, we propose a new approach by which a critical area, an area
far away from serving base station but still inside the coverage of serving base station, is found. And then
overlapping area between serving base stations and neighboring base station are found and tabulated.
According to the size of overlapping area, different weights are assigned where handoff threshold is
changed adaptively to reduce handoff delay.
Performance evaluation of interference aware topology power and flow control ...IJECEIAES
Multi-Radio Multi-Channel Wireless Mesh Network (MRMC-WMN) has been considered as one of the key technology for the enhancement of network performance. It is used in a number of real-time applications such as disaster management system, transportation system and health care system. MRMC-WMN is a multi-hop network and allows simultaneous data transfer by using multiple radio interfaces. All the radio interfaces are typically assigned with different channels to reduce the effect of co-channel interference. In MRMC-WMN, when two nodes transmit at the same channel in the range of each other, generates co-channel interference and degrades the network throughput. Co-channel interference badly affects the capacity of each link that reduces the overall network performance. Thus, the important task of channel assignment algorithm is to reduce the co-channel interference and enhance the network performance. In this paper, the problem of channel assignment has been addressed for MRMC-WMN. We have proposed an Interference Aware, Topology, Power and Flow Control (ITPFC) Channel Assignment algorithm for MRMC-WMN. This algorithm assignes the suitable channels to nodes, which provides better link capacity and reduces the co-channel interference. In the previous work performance of the proposed algorithm has been evaluated for a network of 30 nodes. The aim of this paper is to further evaluate the performance of proposed channel assignment algorithm for 40 and 50 nodes network. The results obtained from these networks show the consistent performance in terms of throughput, delay, packet loss and number of channels used per node as compared to LACA, FCPRA and IATC Channel Assignment algorithms.
Research Inventy : International Journal of Engineering and Scienceinventy
Research Inventy : International Journal of Engineering and Science is published by the group of young academic and industrial researchers with 12 Issues per year. It is an online as well as print version open access journal that provides rapid publication (monthly) of articles in all areas of the subject such as: civil, mechanical, chemical, electronic and computer engineering as well as production and information technology. The Journal welcomes the submission of manuscripts that meet the general criteria of significance and scientific excellence. Papers will be published by rapid process within 20 days after acceptance and peer review process takes only 7 days. All articles published in Research Inventy will be peer-reviewed.
A novel optimal small cells deployment for next-generation cellular networks IJECEIAES
Small-cell-deployments have pulled cellular operators to boost coverage and capacity in high-demand areas (for example, downtown hot spots). The location of these small cells (SCs) should be determined in order to achieve successful deployments. In this paper, we propose a new approach that optimizes small cells deployment in cellular networks to achieve three objectives: reduce the total cost of network installation, balancing the allocation of resources, i.e. placement of each SC and their transmitted power, and providing optimal coverage area with a lower amount of interference between adjacent stations. An accurate formula was obtained to determine the optimum number of SC deployment (NSC). Finally, we derive a mathematical expression to calculate the critical-handoff-point (CHP) for neighboring wireless stations.
MULTI-CRITERIA HANDOVER DECISION FOR HETEROGENEOUS NETWORKS: CARRIER AGGREGAT...IJCNCJournal
Carrier aggregation and integration of heterogeneous networks allow the mobile user equipment to benefit from wider bandwidth and radio coverage of different access technologies. However, these technologies have increased handoff scenario probability through user equipment’s mobility, leading to high outage probability and low throughput. Handover is an important aspect of mobility management which allows users to migrate from one cell to another without losing connections. But no lone access technology meets the requirements of providing seamless communication without loss and delay. Therefore, high-quality service continuity and reliable user equipment access to network anywhere and at any time require the
design of an appropriate handover decision algorithm. In this paper, a multi-criteria based handover decision-making algorithm is proposed to evade loss of communication and provide better performance to the system. It adaptively makes handover decisions based on different decision criteria (load, availability of resources, and the handover scenario type) in addition to signal interference to noise ratio. The multicriteria handover decision making algorithm-based method chooses among the cells that satisfy the requirements for the handover. As compared to some existing handover decision algorithms, simulation result shows that this algorithm improves system performance in terms of handover failure by 93%, 72%,
and 58%; radio link failure reduction by 77%, 43%, and 22%; and handover ping–pong by 81%, 59%, and 36% over the conventional received signal strength, received wireless transmission line, and multiinfluence factor hand over decisions respectively.
LINK-LEVEL PERFORMANCE EVALUATION OF RELAY-BASED WIMAX NETWORKijwmn
Relay technology promises appreciable network throughput and coverage enhancement which is required
for high speed wireless cellular systems to function to their optimum. This paper is focused on analysing
the link performance of a relay-based WiMAX network under varying conditions. Comparison is made
between relay and direct link communication in terms of BER (Bit Error Rate), spectral efficiency and
capacity. Effect of multipath fading and user speed on performance are investigated as well. The entire
study involves a hypothetical view as well as MATLAB simulations to predict the benefit of relay
deployment. This is aimed at solving pertinent issues such as coverage holes and cell edge problems which
are associated with traditional non-relay based cellular networks.
A small vessel detection using a co-located multi-frequency FMCW MIMO radar IJECEIAES
Small vessels detection is a known issue due to its low radar cross section (RCS). An existing shore-based vessel tracking radar is for long-distance commercial vessels detection. Meanwhile, a vessel-mounted radar system known for its reliability has a limitation due to its single radar coverage. The paper presented a co-located frequency modulated continuous waveform (FMCW) maritime radar for small vessel detection utilising a multiple-input multiple-output (MIMO) configuration. The radar behaviour is numerically simulated for detecting a Swerling 1 target which resembles small maritime’s vessels. The simulated MIMO configuration comprised two transmitting and receiving nodes. The proposal is to utilize a multi-frequency FMCW MIMO configuration in a maritime environment by applying the spectrum averaging (SA) to fuse MIMO received signals for range and velocity estimation. The analysis was summarised and displayed in terms of estimation error performance, probability of error and average error. The simulation outcomes an improvement of 2.2 dB for a static target, and 0.1 dB for a moving target, in resulting the 20% probability of range error with the MIMO setup. A moving vessel's effect was observed to degrade the range error estimation performance between 0.6 to 2.7 dB. Meanwhile, the proposed method was proven to improve the 20% probability of velocity error by 1.75 dB. The impact of multi-frequency MIMO was also observed to produce better average error performance.
Wimax technology has reshaped the framework of broadband wireless internet
service. It provides the internet service to unconnected or detached areas such as east South
Africa, rural areas of America and Asia region. Full duplex helpers employed with one of
the relay stations selection and indexing method that is Randomized Distributed Space Time
are used to expand the coverage area of primary Wimax station. The basic problem was
identified at cell edge due to weather conditions (rain, fog), insertion of destruction because
of multiple paths in the same communication channel and due to interference created by
other users in that communication. It is impractical task for the receiver station to decode
the transmitted signal successfully at the cell edges, which increases the high packet loss and
retransmissions. But Wimax is a outstanding technology which is used for improving the
quality of internet service and also it offers various services like Voice over Internet
Protocol, Video conferencing and Multimedia broadcast etc where a little delay in packet
transmission can cause a big loss in the communication. Even setup and initialization of
another Wimax station nearer to each other is not a good alternate, where any mobile
station can easily handover to another base station if it gets a strong signal from other one.
But in rural areas, for few numbers of customers, installation of base station nearer to each
other is costlier task. In this review article, we present a scheme using R-DSTC technique to
choose and select helpers (relay nodes) randomly to expand the coverage area and help to
mobile station as a helper to provide secure communication with base station. In this work,
we use full duplex helpers for better utilization of bandwidth.
Call Admission Control Scheme With Multimedia Scheduling Service in WiMAX Net...Waqas Tariq
WiMAX network introduces a multimedia data scheduling service with different quality of service (QoS) requirements. Transmission opportunities are scheduled by the service according to the types of traffic data for the different connections or users. In the paper, we first propose a uniform definition of QoS level for the multimedia data types in the service. The QoS level of a connection are determined by the type of data of the connection and its allocated resources. Based on these QoS levels, we propose a call admission control (CAC) scheme for the entry admission of a new connection without degrading the network performance and the QoS of ongoing connections. The key idea of this scheme is to regulate the arriving traffic of the network such that the network can work at an optimal point, given under a heavy load traffic. Taking advantage of the simulation experiments, we confirm the fact that the proposed scheme can achieve better trade-off between the overall performance of network system and the QoS level of individual connection.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
RESOURCE ALLOCATION TECHNIQUE USING LOAD MATRIX METHOD IN WIRELESS CELLULAR S...cscpconf
An efficient resource allocation is one of the greatest challenges in wireless cellular
communication. The resource allocation schemes avoid wastage of resources by allocating
resources to a mobile terminal over a short period of time, providing quality of service over
wireless networks is the most stressing point for service providers. In general a high degree of
sharing is efficient, but requires service protection mechanisms to guarantee the QoS for all
services. In this paper we address the multi cell interference on overall radio resource
utilization and propose a new strategy for resource allocation in multi cell systems. we also
propose a joint management of interference within and between cells for allocation of radio
resources , Simulation results are showing that there is a significant improvement in the resource utilization so that overall network performance.
CROSS-LAYER RESOURCE ALLOCATION SCHEME UNDER HETEROGENEOUS CONSTRAINTS FOR NE...IJNSA Journal
In the next generation wireless networks, the growing demand for new wireless applications is accompanied with high expectations for better quality of service (QoS) fulfillment especially for multimedia applications. Furthermore, the coexistence of future unlicensed users with existing licensed users is becoming a challenging task in the next generation communication systems to overcome the underutilization of the spectrum. A QoS and interference aware resource allocation is thus of special interest in order to respond to the heterogeneous constraints of the next generation networks. In this work, we address the issue of resource allocation under heterogeneous constraints for unlicensed multiband ultra-wideband (UWB) systems in the context of Future Home Networks, i.e. the wireless personal area network (WPAN). The problem is first studied analytically using a heterogeneous constrained optimization problem formulation. After studying the characteristics of the optimal solution, we propose a low-complexity suboptimal algorithm based on a cross-layer approach that combines information provided by the PHY and MAC layers. While the PHY layer is responsible for providing the channel quality of the unlicensed UWB users as well as their interference power that they cause on licensed users, the MAC layer is responsible for classifying the unlicensed users using a two-class based approach that guarantees for multimedia services a high-priority level compared to other services. Combined in an efficient and simple way, the PHY and MAC information present the key elements of the aimed resource allocation. Simulation results demonstrate that the proposed scheme provides a good tradeoff between the QoS satisfaction of the unlicensed applications with hard QoS requirements and the limitation of the interference affecting the licensed users.
Quality of Service in bandwidth adapted hybrid UMTS/WLAN interworking networkTELKOMNIKA JOURNAL
Integration of Universal Mobile Telecommunications System (UMTS) and Wireless Local Area Network (WLAN) result in ubiquitous connection for end users. In the integrated network, ensuring the quality of service to users and enhancing capacity of network are prominent issues. Bandwidth adaptation technique is one of the solutions to overcome these issues. Bandwidth adaptation based on per flow and per class schemes were proposed for loosely coupled interworking network. In this paper, hybrid coupled UMTS and WLAN interworking network is analyzed with bandwidth adaptation based on per flow and per class schemes and the performances have been compared. Simulation result shows that the proposed hybrid coupled interworking network with bandwidth adaptation based on per class scheme performs better with enhanced quality of service and network capacity.
A CELLULAR BONDING AND ADAPTIVE LOAD BALANCING BASED MULTI-SIM GATEWAY FOR MO...pijans
As it is well known, the QoS(quality of service) provided by mobile Internet access point devices is far from
the QoS level offered by the common ADSL modem-router due to several reasons: in fact, mobile Internet
access networks are not designed to support real-time data traffic because of several drawbacks
concerning the wireless medium such as resource sharing, traffic congestion, radio link coverage etc.,
which impact directly such parameters as delay, jitter, and packet loss rate that are strictly connected to
the quality of user experience. The main scope of the present paper is to introduce a dual USIM HSPA
gateway for ad hoc and sensors networks thanks to which it will be possible to guarantee a QoS suitable
for a series of network-centric application such as real-time communications and monitoring, video
surveillance, real-time sensor networks, telemedicine, vehicular and mobile sensor networks and so on. The
main idea is to exploit multiple radio access networks in order to enhance the available end-to-end
bandwidth and the perceived quality of experience. The scope has been reached by combining multiple
radio access with dynamic load balancing and the VPN (virtual private network) bond technique.
MULTI USER DETECTOR IN CDMA USING ELLIPTIC CURVE CRYPTOGRAPHYVLSICS Design
Code division multiple access (CDMA) is used in various radio communication techniques due to its advantages. In CDMA one of the most important processes is multi user detection (MUD). There are numerous methods for MUD in CDMA, but in most of the methods, they identify the exact user but the interference signal is high. One of the methods used for MUD in CDM A is elliptic curve cryptography (ECC). Normally, the multi user detector in CDMA using elliptic curve cryptography is performed by using one prime field. In ECC method the exact user is identified and also interference signal reduces comparing with other techniques. To reduce the interference signal to very low, here propose a new technique for MUD in CDMA using ECC. The proposed technique uses multiple prime numbers for key generation. By generating key using different prime numbers using ECC, the bit error rate was very low. The results shows the performance of the proposed for reduce in bit error rate for MUD in CDMA.
Modelling and QoS-Achieving Solution in full-duplex Cellular SystemsIJCNCJournal
The global bandwidth scarcity and the ever-growing demand for fast wireless services have motivated the quest for new techniques that enhance the spectral efficiency (SE) of wireless systems. Most conventional SE increasing methods (e.g., adaptive modulation and coding) have already been exhausted. Single-channel full-duplex (SCFD) communication is a new attractive approach in which each node may simultaneously receive and transmit over the same frequency channel, and thus, it has the potential to double the current SE figures. In this paper, we derive a model for the signal-to-interference-plus-noise ratio (SINR) in a SCFD-based cellular system with imperfect self-interference cancellation. Furthermore, given a set of uplink and downlink quality of service requirements, we answer the following two fundamental questions. First, is this set achievable in the SCFD-based cellular system? Second, if the given set is achievable, what is the optimal achieving policy? To that end, we provide a unified model for the SCFD-based cellular system, and give insights in the matrix of interference channel gains. Simulation results suggest that depending on the locations of the users, a combination of full-duplex and half-duplex modes over the whole network is more favourable policy
MULTI-HOP BANDWIDTH MANAGEMENT PROTOCOL FOR MOBILE AD HOC NETWORKSIJMIT JOURNAL
An admission control scheme should play the role of a coordinator for flows in a data communication network, to provide the guarantees as the medium is shared. The nodes of a wired network can monitor the medium to know the available bandwidth at any point of time. But, in wireless ad hoc networks, a node must consume the bandwidth of neighboring nodes, during a communication. Hence, the consumption of bandwidth by a flow and the availability of resources to any wireless node strictly depend upon the neighboring nodes within its transmission range. We present a scalable and efficient admission control scheme, Multi-hop Bandwidth Management Protocol (MBMP), to support the QoS requirements
in multi-hop ad hoc networks. We simulate several options to design MBMP and compare the performances of these options through mathematical analysis and simulation results, and compare its effectiveness with the existing admission control schemes through extensive simulations.
A Cooperative Approach to Extend Cellular Coverage via D2D Architecture based...IJCNCJournal
The access part of all cellular network’s generation suffers from common concerns related to dead spots (zones that are not covered by the network) and hot spots (zones where the number of users is higher compared to network resources). During the last decade, lots of research proposals have tried to overcome cellular problems through multi-hop D2D architecture, which is a new paradigm allowing the direct communication between devices in cellular network to enhance network performances and improve user QoS. In this paper, we propose a multi-hop D2D architecture based on the OLSR protocol to extend cellular coverage. Cell-OLSR, which is the proposed adaptation of OLSR for our architecture, allows the exchange of cellular parameters between nodes to choose the best proxy device to forward data to the cellular base station (BS).
SELECTION OF SPECTRUM SENSING METHOD TO ENHANCE QOS IN COGNITIVE RADIO NETWORKSijwmn
The massively increasing number of wireless communication devices has led to considerable growths in
radio traffic density, resulting in a predictable shortage of the available spectrum. To address this potential
shortage, the Cognitive Radio (CR) technology offers promising solutions that aim to improve the spectrum
utilization. The operation of CR relies on detecting the so-called spectrum holes, i.e., the frequency bands
when they are unoccupied by their licensed operators. The unlicensed users are then allowed to
communicate using these spectrum holes. Consequently, the performance of CR is highly dependent on the
employed spectrum sensing methods. Several sensing methods are already available or literarily proposed.
However, no individual method can accommodate all possible CR operation scenarios. Hence, it is fair to
ascertain that the performance of a CR device can be improved if it is capable of supporting several
sensing methods. Then it should be able to effectively select the most suitable method. In this paper, several
spectrum sensing methods are compared and analyzed, aiming to identify their advantages and
shortcomings in different CR operating conditions. Furthermore, it identifies the factors that need to be
considered while selecting a proper sensing method from the catalog of available methods.
Design and analysis of high gain diode predistortionijwmn
This paper presents the design and analysis of a high gain, broadband Schottky and PIN diode based RF
pre-distortion linearizer for TWTA. The circuit is using ABCD matrix approach. The simulation is
performed using Agilent ADS software. We have proposed a new linearizer circuit which can achieve a
high gain compared to existing linearizer designs.
ROUTING PROTOCOLS FOR DELAY TOLERANT NETWORKS: SURVEY AND PERFORMANCE EVALUATIONijwmn
Delay Tolerant Networking (DTN) is a promising technology that aims to provide efficient communication
between devices in a network with no guaranteed continuous connectivity. Most existing routing schemes
for DTNs exploit the advantage of message replication to achieve high message delivery rate. However,
these schemes commonly suffer from large communication overhead due to the lack of efficient mechanisms
to control message replication. In this paper we give a brief survey on routing protocols designed for
DTNs, and evaluate the performance of several representative routing protocols including Epidemic, Spray
and Wait, PRoPHET, and 3R through extensive trace-driven simulations. Another objective of this work is
to evaluate the security strength of different routing schemes under common DTN attacks such as the black
hole attack. The results and analysis presented in this paper can provide useful guidance on the design and
selection of routing protocols for given delay-tolerant applications.
DISCRETE COSINETRANSFORM-II FOR REDUCTION IN PEAK TO AVERAGE POWER RATIO OF O...ijwmn
Orthogonal frequency Division multiplexing (OFDM) is the most familiar word in telecommunication
and wireless communication systems as it provides enhanced spectral efficiency than Frequency division
multiplexing (FDM).Although it is sustaining an orthogonal relation betweencarriers but high peak to
average power ratio (PAPR) is one of the main disadvantages of OFDM system.Various PAPR reduction
techniques have been used, including techniques based on companding. Incompanding, -Law
companding has potential to reduce the PAPR of OFDMsignals. -Law Companding technique
preserves the dynamic range of samples at low amplitudes.A new method named as precoding which is
having less complexity compared to the other power reduction techniques is proposed to reduce PAPR.
This paper put forward combination of two existing techniques namely -Law Companding Transform
and Discrete Cosine Transform-II precoding technique. The simulation results show that, the proposed
combinedscheme gives better result for PAPR Reduction and results in no distortion.
Research Inventy : International Journal of Engineering and Scienceinventy
Research Inventy : International Journal of Engineering and Science is published by the group of young academic and industrial researchers with 12 Issues per year. It is an online as well as print version open access journal that provides rapid publication (monthly) of articles in all areas of the subject such as: civil, mechanical, chemical, electronic and computer engineering as well as production and information technology. The Journal welcomes the submission of manuscripts that meet the general criteria of significance and scientific excellence. Papers will be published by rapid process within 20 days after acceptance and peer review process takes only 7 days. All articles published in Research Inventy will be peer-reviewed.
A novel optimal small cells deployment for next-generation cellular networks IJECEIAES
Small-cell-deployments have pulled cellular operators to boost coverage and capacity in high-demand areas (for example, downtown hot spots). The location of these small cells (SCs) should be determined in order to achieve successful deployments. In this paper, we propose a new approach that optimizes small cells deployment in cellular networks to achieve three objectives: reduce the total cost of network installation, balancing the allocation of resources, i.e. placement of each SC and their transmitted power, and providing optimal coverage area with a lower amount of interference between adjacent stations. An accurate formula was obtained to determine the optimum number of SC deployment (NSC). Finally, we derive a mathematical expression to calculate the critical-handoff-point (CHP) for neighboring wireless stations.
MULTI-CRITERIA HANDOVER DECISION FOR HETEROGENEOUS NETWORKS: CARRIER AGGREGAT...IJCNCJournal
Carrier aggregation and integration of heterogeneous networks allow the mobile user equipment to benefit from wider bandwidth and radio coverage of different access technologies. However, these technologies have increased handoff scenario probability through user equipment’s mobility, leading to high outage probability and low throughput. Handover is an important aspect of mobility management which allows users to migrate from one cell to another without losing connections. But no lone access technology meets the requirements of providing seamless communication without loss and delay. Therefore, high-quality service continuity and reliable user equipment access to network anywhere and at any time require the
design of an appropriate handover decision algorithm. In this paper, a multi-criteria based handover decision-making algorithm is proposed to evade loss of communication and provide better performance to the system. It adaptively makes handover decisions based on different decision criteria (load, availability of resources, and the handover scenario type) in addition to signal interference to noise ratio. The multicriteria handover decision making algorithm-based method chooses among the cells that satisfy the requirements for the handover. As compared to some existing handover decision algorithms, simulation result shows that this algorithm improves system performance in terms of handover failure by 93%, 72%,
and 58%; radio link failure reduction by 77%, 43%, and 22%; and handover ping–pong by 81%, 59%, and 36% over the conventional received signal strength, received wireless transmission line, and multiinfluence factor hand over decisions respectively.
LINK-LEVEL PERFORMANCE EVALUATION OF RELAY-BASED WIMAX NETWORKijwmn
Relay technology promises appreciable network throughput and coverage enhancement which is required
for high speed wireless cellular systems to function to their optimum. This paper is focused on analysing
the link performance of a relay-based WiMAX network under varying conditions. Comparison is made
between relay and direct link communication in terms of BER (Bit Error Rate), spectral efficiency and
capacity. Effect of multipath fading and user speed on performance are investigated as well. The entire
study involves a hypothetical view as well as MATLAB simulations to predict the benefit of relay
deployment. This is aimed at solving pertinent issues such as coverage holes and cell edge problems which
are associated with traditional non-relay based cellular networks.
A small vessel detection using a co-located multi-frequency FMCW MIMO radar IJECEIAES
Small vessels detection is a known issue due to its low radar cross section (RCS). An existing shore-based vessel tracking radar is for long-distance commercial vessels detection. Meanwhile, a vessel-mounted radar system known for its reliability has a limitation due to its single radar coverage. The paper presented a co-located frequency modulated continuous waveform (FMCW) maritime radar for small vessel detection utilising a multiple-input multiple-output (MIMO) configuration. The radar behaviour is numerically simulated for detecting a Swerling 1 target which resembles small maritime’s vessels. The simulated MIMO configuration comprised two transmitting and receiving nodes. The proposal is to utilize a multi-frequency FMCW MIMO configuration in a maritime environment by applying the spectrum averaging (SA) to fuse MIMO received signals for range and velocity estimation. The analysis was summarised and displayed in terms of estimation error performance, probability of error and average error. The simulation outcomes an improvement of 2.2 dB for a static target, and 0.1 dB for a moving target, in resulting the 20% probability of range error with the MIMO setup. A moving vessel's effect was observed to degrade the range error estimation performance between 0.6 to 2.7 dB. Meanwhile, the proposed method was proven to improve the 20% probability of velocity error by 1.75 dB. The impact of multi-frequency MIMO was also observed to produce better average error performance.
Wimax technology has reshaped the framework of broadband wireless internet
service. It provides the internet service to unconnected or detached areas such as east South
Africa, rural areas of America and Asia region. Full duplex helpers employed with one of
the relay stations selection and indexing method that is Randomized Distributed Space Time
are used to expand the coverage area of primary Wimax station. The basic problem was
identified at cell edge due to weather conditions (rain, fog), insertion of destruction because
of multiple paths in the same communication channel and due to interference created by
other users in that communication. It is impractical task for the receiver station to decode
the transmitted signal successfully at the cell edges, which increases the high packet loss and
retransmissions. But Wimax is a outstanding technology which is used for improving the
quality of internet service and also it offers various services like Voice over Internet
Protocol, Video conferencing and Multimedia broadcast etc where a little delay in packet
transmission can cause a big loss in the communication. Even setup and initialization of
another Wimax station nearer to each other is not a good alternate, where any mobile
station can easily handover to another base station if it gets a strong signal from other one.
But in rural areas, for few numbers of customers, installation of base station nearer to each
other is costlier task. In this review article, we present a scheme using R-DSTC technique to
choose and select helpers (relay nodes) randomly to expand the coverage area and help to
mobile station as a helper to provide secure communication with base station. In this work,
we use full duplex helpers for better utilization of bandwidth.
Call Admission Control Scheme With Multimedia Scheduling Service in WiMAX Net...Waqas Tariq
WiMAX network introduces a multimedia data scheduling service with different quality of service (QoS) requirements. Transmission opportunities are scheduled by the service according to the types of traffic data for the different connections or users. In the paper, we first propose a uniform definition of QoS level for the multimedia data types in the service. The QoS level of a connection are determined by the type of data of the connection and its allocated resources. Based on these QoS levels, we propose a call admission control (CAC) scheme for the entry admission of a new connection without degrading the network performance and the QoS of ongoing connections. The key idea of this scheme is to regulate the arriving traffic of the network such that the network can work at an optimal point, given under a heavy load traffic. Taking advantage of the simulation experiments, we confirm the fact that the proposed scheme can achieve better trade-off between the overall performance of network system and the QoS level of individual connection.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
RESOURCE ALLOCATION TECHNIQUE USING LOAD MATRIX METHOD IN WIRELESS CELLULAR S...cscpconf
An efficient resource allocation is one of the greatest challenges in wireless cellular
communication. The resource allocation schemes avoid wastage of resources by allocating
resources to a mobile terminal over a short period of time, providing quality of service over
wireless networks is the most stressing point for service providers. In general a high degree of
sharing is efficient, but requires service protection mechanisms to guarantee the QoS for all
services. In this paper we address the multi cell interference on overall radio resource
utilization and propose a new strategy for resource allocation in multi cell systems. we also
propose a joint management of interference within and between cells for allocation of radio
resources , Simulation results are showing that there is a significant improvement in the resource utilization so that overall network performance.
CROSS-LAYER RESOURCE ALLOCATION SCHEME UNDER HETEROGENEOUS CONSTRAINTS FOR NE...IJNSA Journal
In the next generation wireless networks, the growing demand for new wireless applications is accompanied with high expectations for better quality of service (QoS) fulfillment especially for multimedia applications. Furthermore, the coexistence of future unlicensed users with existing licensed users is becoming a challenging task in the next generation communication systems to overcome the underutilization of the spectrum. A QoS and interference aware resource allocation is thus of special interest in order to respond to the heterogeneous constraints of the next generation networks. In this work, we address the issue of resource allocation under heterogeneous constraints for unlicensed multiband ultra-wideband (UWB) systems in the context of Future Home Networks, i.e. the wireless personal area network (WPAN). The problem is first studied analytically using a heterogeneous constrained optimization problem formulation. After studying the characteristics of the optimal solution, we propose a low-complexity suboptimal algorithm based on a cross-layer approach that combines information provided by the PHY and MAC layers. While the PHY layer is responsible for providing the channel quality of the unlicensed UWB users as well as their interference power that they cause on licensed users, the MAC layer is responsible for classifying the unlicensed users using a two-class based approach that guarantees for multimedia services a high-priority level compared to other services. Combined in an efficient and simple way, the PHY and MAC information present the key elements of the aimed resource allocation. Simulation results demonstrate that the proposed scheme provides a good tradeoff between the QoS satisfaction of the unlicensed applications with hard QoS requirements and the limitation of the interference affecting the licensed users.
Quality of Service in bandwidth adapted hybrid UMTS/WLAN interworking networkTELKOMNIKA JOURNAL
Integration of Universal Mobile Telecommunications System (UMTS) and Wireless Local Area Network (WLAN) result in ubiquitous connection for end users. In the integrated network, ensuring the quality of service to users and enhancing capacity of network are prominent issues. Bandwidth adaptation technique is one of the solutions to overcome these issues. Bandwidth adaptation based on per flow and per class schemes were proposed for loosely coupled interworking network. In this paper, hybrid coupled UMTS and WLAN interworking network is analyzed with bandwidth adaptation based on per flow and per class schemes and the performances have been compared. Simulation result shows that the proposed hybrid coupled interworking network with bandwidth adaptation based on per class scheme performs better with enhanced quality of service and network capacity.
A CELLULAR BONDING AND ADAPTIVE LOAD BALANCING BASED MULTI-SIM GATEWAY FOR MO...pijans
As it is well known, the QoS(quality of service) provided by mobile Internet access point devices is far from
the QoS level offered by the common ADSL modem-router due to several reasons: in fact, mobile Internet
access networks are not designed to support real-time data traffic because of several drawbacks
concerning the wireless medium such as resource sharing, traffic congestion, radio link coverage etc.,
which impact directly such parameters as delay, jitter, and packet loss rate that are strictly connected to
the quality of user experience. The main scope of the present paper is to introduce a dual USIM HSPA
gateway for ad hoc and sensors networks thanks to which it will be possible to guarantee a QoS suitable
for a series of network-centric application such as real-time communications and monitoring, video
surveillance, real-time sensor networks, telemedicine, vehicular and mobile sensor networks and so on. The
main idea is to exploit multiple radio access networks in order to enhance the available end-to-end
bandwidth and the perceived quality of experience. The scope has been reached by combining multiple
radio access with dynamic load balancing and the VPN (virtual private network) bond technique.
MULTI USER DETECTOR IN CDMA USING ELLIPTIC CURVE CRYPTOGRAPHYVLSICS Design
Code division multiple access (CDMA) is used in various radio communication techniques due to its advantages. In CDMA one of the most important processes is multi user detection (MUD). There are numerous methods for MUD in CDMA, but in most of the methods, they identify the exact user but the interference signal is high. One of the methods used for MUD in CDM A is elliptic curve cryptography (ECC). Normally, the multi user detector in CDMA using elliptic curve cryptography is performed by using one prime field. In ECC method the exact user is identified and also interference signal reduces comparing with other techniques. To reduce the interference signal to very low, here propose a new technique for MUD in CDMA using ECC. The proposed technique uses multiple prime numbers for key generation. By generating key using different prime numbers using ECC, the bit error rate was very low. The results shows the performance of the proposed for reduce in bit error rate for MUD in CDMA.
Modelling and QoS-Achieving Solution in full-duplex Cellular SystemsIJCNCJournal
The global bandwidth scarcity and the ever-growing demand for fast wireless services have motivated the quest for new techniques that enhance the spectral efficiency (SE) of wireless systems. Most conventional SE increasing methods (e.g., adaptive modulation and coding) have already been exhausted. Single-channel full-duplex (SCFD) communication is a new attractive approach in which each node may simultaneously receive and transmit over the same frequency channel, and thus, it has the potential to double the current SE figures. In this paper, we derive a model for the signal-to-interference-plus-noise ratio (SINR) in a SCFD-based cellular system with imperfect self-interference cancellation. Furthermore, given a set of uplink and downlink quality of service requirements, we answer the following two fundamental questions. First, is this set achievable in the SCFD-based cellular system? Second, if the given set is achievable, what is the optimal achieving policy? To that end, we provide a unified model for the SCFD-based cellular system, and give insights in the matrix of interference channel gains. Simulation results suggest that depending on the locations of the users, a combination of full-duplex and half-duplex modes over the whole network is more favourable policy
MULTI-HOP BANDWIDTH MANAGEMENT PROTOCOL FOR MOBILE AD HOC NETWORKSIJMIT JOURNAL
An admission control scheme should play the role of a coordinator for flows in a data communication network, to provide the guarantees as the medium is shared. The nodes of a wired network can monitor the medium to know the available bandwidth at any point of time. But, in wireless ad hoc networks, a node must consume the bandwidth of neighboring nodes, during a communication. Hence, the consumption of bandwidth by a flow and the availability of resources to any wireless node strictly depend upon the neighboring nodes within its transmission range. We present a scalable and efficient admission control scheme, Multi-hop Bandwidth Management Protocol (MBMP), to support the QoS requirements
in multi-hop ad hoc networks. We simulate several options to design MBMP and compare the performances of these options through mathematical analysis and simulation results, and compare its effectiveness with the existing admission control schemes through extensive simulations.
A Cooperative Approach to Extend Cellular Coverage via D2D Architecture based...IJCNCJournal
The access part of all cellular network’s generation suffers from common concerns related to dead spots (zones that are not covered by the network) and hot spots (zones where the number of users is higher compared to network resources). During the last decade, lots of research proposals have tried to overcome cellular problems through multi-hop D2D architecture, which is a new paradigm allowing the direct communication between devices in cellular network to enhance network performances and improve user QoS. In this paper, we propose a multi-hop D2D architecture based on the OLSR protocol to extend cellular coverage. Cell-OLSR, which is the proposed adaptation of OLSR for our architecture, allows the exchange of cellular parameters between nodes to choose the best proxy device to forward data to the cellular base station (BS).
SELECTION OF SPECTRUM SENSING METHOD TO ENHANCE QOS IN COGNITIVE RADIO NETWORKSijwmn
The massively increasing number of wireless communication devices has led to considerable growths in
radio traffic density, resulting in a predictable shortage of the available spectrum. To address this potential
shortage, the Cognitive Radio (CR) technology offers promising solutions that aim to improve the spectrum
utilization. The operation of CR relies on detecting the so-called spectrum holes, i.e., the frequency bands
when they are unoccupied by their licensed operators. The unlicensed users are then allowed to
communicate using these spectrum holes. Consequently, the performance of CR is highly dependent on the
employed spectrum sensing methods. Several sensing methods are already available or literarily proposed.
However, no individual method can accommodate all possible CR operation scenarios. Hence, it is fair to
ascertain that the performance of a CR device can be improved if it is capable of supporting several
sensing methods. Then it should be able to effectively select the most suitable method. In this paper, several
spectrum sensing methods are compared and analyzed, aiming to identify their advantages and
shortcomings in different CR operating conditions. Furthermore, it identifies the factors that need to be
considered while selecting a proper sensing method from the catalog of available methods.
Design and analysis of high gain diode predistortionijwmn
This paper presents the design and analysis of a high gain, broadband Schottky and PIN diode based RF
pre-distortion linearizer for TWTA. The circuit is using ABCD matrix approach. The simulation is
performed using Agilent ADS software. We have proposed a new linearizer circuit which can achieve a
high gain compared to existing linearizer designs.
ROUTING PROTOCOLS FOR DELAY TOLERANT NETWORKS: SURVEY AND PERFORMANCE EVALUATIONijwmn
Delay Tolerant Networking (DTN) is a promising technology that aims to provide efficient communication
between devices in a network with no guaranteed continuous connectivity. Most existing routing schemes
for DTNs exploit the advantage of message replication to achieve high message delivery rate. However,
these schemes commonly suffer from large communication overhead due to the lack of efficient mechanisms
to control message replication. In this paper we give a brief survey on routing protocols designed for
DTNs, and evaluate the performance of several representative routing protocols including Epidemic, Spray
and Wait, PRoPHET, and 3R through extensive trace-driven simulations. Another objective of this work is
to evaluate the security strength of different routing schemes under common DTN attacks such as the black
hole attack. The results and analysis presented in this paper can provide useful guidance on the design and
selection of routing protocols for given delay-tolerant applications.
DISCRETE COSINETRANSFORM-II FOR REDUCTION IN PEAK TO AVERAGE POWER RATIO OF O...ijwmn
Orthogonal frequency Division multiplexing (OFDM) is the most familiar word in telecommunication
and wireless communication systems as it provides enhanced spectral efficiency than Frequency division
multiplexing (FDM).Although it is sustaining an orthogonal relation betweencarriers but high peak to
average power ratio (PAPR) is one of the main disadvantages of OFDM system.Various PAPR reduction
techniques have been used, including techniques based on companding. Incompanding, -Law
companding has potential to reduce the PAPR of OFDMsignals. -Law Companding technique
preserves the dynamic range of samples at low amplitudes.A new method named as precoding which is
having less complexity compared to the other power reduction techniques is proposed to reduce PAPR.
This paper put forward combination of two existing techniques namely -Law Companding Transform
and Discrete Cosine Transform-II precoding technique. The simulation results show that, the proposed
combinedscheme gives better result for PAPR Reduction and results in no distortion.
DYNAMIC OPTIMIZATION OF OVERLAP-AND-ADD LENGTH OVER MIMO MBOFDM SYSTEM BASED ...ijwmn
An important role performed by Zero Padding (ZP) in multi-band OFDM (MB-OFDM) System. This role
show for low-complexity in résistance against multipath interference by reducing inter-carrier interference
(ICI) and eliminating the inter-symbol interference (ISI) Also, zero-padded suffix can be used to eliminate
ripples in the power spectral density in order to conform to FCC requirements. At the receiver of MB-OFDM system needs to use of a technique called as overlap-and-add (OLA). Which maintain the circular convolution property and take the multipath energy of the channel.In this paper, we proposed a method of performing overlap-and-add length for zero padded suffixes. Then,we studied the effect of this method, dynamic optimization of overlap-and-add (OLA) equalization, on the performance of MIMO MBOFDM system on Bit Error Rate (BER) with AWGN channel and SalehValenzuela (S-V) Multipath channel Model.In the dynamic optimization OLA, the Length of ZP depends on length of channel impulse response (CIR).
These measures, based on SNR, insert the ZP according to the measurement.Dynamic optimization of length of ZP improves the Performance of MIMO MBOFDM system. In fact wedeveloped a technique to select the length of ZP as function of SNR and CIR estimate. In our simulation
this technique improve to 0.6 dB at BER=10-2 with a multipath channels CM4
A Grouped System Architecture for Smart Grids Based AMI Communications Over LTE ijwmn
A smart grid based Advanced Metering Infrastructure (AMI), is a technology that enables the utilities to
monitor and control the electricity consumption through a set of various smart meters (SMs) connected via
a two way communication infrastructure. One of the key challenges for smart grids is how to connect a
large number of devices. On the other hand, 4G Long Term Evolution (LTE), the latest standard for mobile
communications, was developed to provide stable service performance and higher data rates for a large
number of mobile users. Therefore, LTE is considered a promising solution for wide area connectivity for
SMs. In this paper, a grouped hierarchal architecture for SMs communications over LTE is introduced.
Then, an efficient grouped scheduling technique is proposed for SMs transmissions over LTE. The
proposed architecture efficiently solves the overload problem due to AMI traffic and guarantees a full
monitoring and control for energy consumption. The results of our suggested solution showed that LTE can
serve better for smart grids based AMI with particular grouping and scheduling scheme. In addition, the
presented technique can able to be used in urban areas having high density of SMs.
Cube satellite missions perform innovative scientific experiments on a low cost developmental platform but
have an inherent limitation of size and space. This restricts the total available solar power that can be
harnessed and as a result, the radio links operate on stringent power budgets. For improving the available
margins for communication in such satellites, it is desirable to improve upon the antenna system
performance at the ground station used for the establishment of the links with the satellite. This can be
achieved by improving the forward gain, the forward to backward ratio and the directivity of the antenna.
This paper describes the electrical simulations and the performance evaluation of the one unit, two unit and
four unit circularly polarized crossed Yagi-Uda antenna array designed for communication with amateur
radio (HAM) satellites operating over the 434 MHz to 438 MHz Amateur UHF band. The electro-magnetic
model has been developed using the 4NEC2 software. The simulations have been validated with the
practical field testing performed for estimating the SWR, antenna gain, the forward to backward ratio and
radiation pattern for the antenna system.
Performance evaluation of different spectrum sensing techniques for realistic...ijwmn
In this paper, the performance assessment of five different detection techniques from spectrum sensing
perspective in cognitive radio networks is proposed and implemented using the realistic implementation
oriented model (R-model) with signal processing operations. The performance assessment of the different
sensing techniques in the existence of unknown or imprecisely known impulsive noise levels is done by
considering the signal detection in cognitive radio networks under a non-parametric multisensory detection
scenario. The examination focuses on performance comparison of basic spectrum sensing mechanisms as,
energy detection (ED) and cyclostationary feature detection (CSFD) along with the eigenvalue-based
detection methods namely, Maximum-minimum eigenvalue detection (MMED), Roy’s largest Root Test
(RLRT) which requires knowledge of the noise variance and Generalized Likelihood Ratio Test (GLRT)
which can be implemented as a test of the largest eigenvalues vs. Maximum-likelihood estimates a noise
variance. From simulation results it is observed that the detection performance of the GLRT method is
better than the other techniques in realistic implementation oriented model.
Wireless sensor nodes are usually deployed in not easily accessible places to provide solution to a wide
range of application such as environmental, medical and structural monitoring. They are spatially
distributed and as a result are usually powered from batteries. Due to the limitation in providing power
with batteries, which must be manually replaced when they are depleted, and location constraints in
wireless sensor network causes a major setback on performance and lifetime of WSNs. This difficulty in
battery replacement and cost led to a growing interest in energy harvesting. The current practice in energy
harvesting for sensor networks is based on practical and simulation approach. The evaluation and
validation of the WSN systems is mostly done using simulation and practical implementation. Simulation is
widely used especially for its great advantage in evaluating network systems. Its disadvantages such as the
long time taken to simulate and not being economical as it implements data without proper analysis of all
that is involved ,wasting useful resources cannot be ignored. In most times, the energy scavenged is directly
wired to the sensor nodes. We, therefore, argue that simulation – based and practical implementation of
WSN energy harvesting system should be further strengthened through mathematical analysis and design
procedures. In this work, we designed and modeled the energy harvesting system for wireless sensor nodes
based on the input and output parameters of the energy sources and sensor nodes. We also introduced the
use of supercapacitor as buffer and intermittent source for the sensor node. The model was further tested in
a Matlab environment, and found to yield a very good approach for system design.
Long term evolution (LTE) is replacing the 3G services slowly but steadily and become a preferred choice
for data for human to human (H2H) services and now it is becoming preferred choice for voice also. In
some developed countries the traditional 2G services gradually decommissioned from the service and
getting replaced with LTE for all H2H services. LTE provided high downlink and uplink bandwidth
capacity and is one of the technology like mobile ad hoc network (MANET) and vehicular ad hoc network
(VANET) being used as the backbone communication infrastructure for vehicle networking applications.
When Compared to VANET and MANET, LTE provides wide area of coverage and excellent infrastructure
facilities for vehicle networking. This helps in transmitting the vehicle information to the operator and
downloading certain information into the vehicle nodes (VNs) from the operators server. As per the ETSI
publications the number of machine to machine communication (MTC) devices are expected to touch 50
billion by 2020 and this will surpass H2H communication. With growing congestion in the LTE network,
accessing the network for any request from VN especially during peak hour is a big challenge because of
the congestion in random access channel (RACH). In this paper we will analyse this RACH congestion
problem with the data from the live network. Lot of algorithms are proposed for resolving the RACH
congestion on the basis of simulation results so we would like to present some practical data from the live
network to this issue to understand the extent RACH congestion issue in the real time scenario.
Performance of the IEEE 802.15.4a UWB System using Two Pulse Shaping Techniqu...ijwmn
In Cognitive radio (CR) applications Ultra-wideband (UWB) impulse radio (IR) signals can be designed
such as they can co-exist with licensed primary users. The pulse shape should be adjusted such that the
power spectral characteristics not only meet the Federal Communications Commission (FCC) constrains,
but also mitigate multiple narrow-band interference at the locations of existing primary users. In this
paper, the Parks-McClellan (PM) Algorithm and the Eigen Value Decomposition (EVD) approach for
UWB impulse radio waveform shaping are considered. The power spectral density (PSD) and the bit-errorrate
(BER) performance of the two methods are compared in the presence of single and double narrowband
interference (NBI). The interference rejection capabilities of the two methods are evaluated and
compared for different interference and additive noise levels. In particular, the simulations consider the
coexistence of practical IEEE 802.15.4a UWB systems with both IEEE 802.11 wireless LAN systems
operating at 5.2 GHz and radio location services operating at 8.5 GHz.
The delivering of both good quality of service (QoS) and Grade of Service (GoS) in any competitive mobile
communication environment is a major factor to reducing subscribers’ churn rate. Therefore, it is
important for wireless mobile network operators to ensure stability and efficiency by delivering a
consistent, reliable and high-quality end user (subscriber) satisfaction. This can only be achieve by
conducting a regular network performance monitoring and optimisation as it directly impacts the quality of
the offered services and hence user satisfaction. In this paper, we present the results of network
performance evaluation and optimisation of a GSM network on cell cluster-basis, in Asaba region, South
East Nigeria. We employ a combination of essential key performance indicators such as dropped call rate,
call setup success rate and outage call rate to examine overall QoS and GoS performance of the GSM
network. Our results after network optimisation showed significant performance improvement in terms of
call drop rate, call set up success rate, and call block rate across. Specifically, the end user satisfaction
rate has increased from 94.45%, 87.74%, and 92.85% to 99.05%, 95.38% and 99.03% respectively across
the three GSM cell clusters. The GoS is reduced from 3.33%, 6.60% and 2.38% to 0.00%, 3.70% and
0.00% respectively. Furthermore, ESA, which correspond end points service availability, has improved
from 94.44%, 93.40% and 97.62% to 100%, 96.30% and 100% respectively. In addition, the average
throughput has improved from 73.74kbits/s, 85.06kbits/s and 87.54kbits/s to 77.07kbits/s, 92.38kbits/s and
102kbits/s respectively across the three GSM cell clusters.
EFFECTS OF FILTERS ON THE PERFORMANCE OF DVB-T RECEIVERijwmn
Digital Video Broadcasting-Terrestrial (DVB-T) is an international standard for digital television
services. Orthogonal Frequency Division Multiplexing (OFDM) is the core of this technology. OFDM
based system like DVB-T can handle multipath fading and hence it can minimize Inter Symbol
Interference (ISI). DVB-T has some limitations too namely large dynamic range of the signals and
sensitivity to frequency error. In order to overcome these limitations DVB-T receivers should be optimally
designed. In this paper we address the issues related to optimal DVB-T receiver design. There of several
signal processing units in a DVB-T receiver. A low-pass filter is one of them. In this paper, we consider
some classic filters namely Butterworth, Chebyshev, and elliptic in the DVB-T receiver. The effects of
different filters on the performances of DVB-T receiver have been investigated and compared in this
paper under AWGN channel condition
S URVEY OF L TE D OWNLINK S CHEDULERS A LGORITHMS IN O PEN A CCESS S IM...ijwmn
he LTE/LTE-A has become a catchphrase for research
and lot of research are being conducted and
carried out in LTE in various issues by various peo
ple. New tools are developed and introduced in the
market to interpret the results of the new algorith
ms proposed by various people. Some tools are open
access which are free to use but some tools are pro
duced by the companies which are not open access. I
n
this paper some of the open access simulation tools
like LTE-Sim and NS-3 are analyzed and LTE downlin
k
scheduler algorithms are simulated using those tool
s. In LTE systems, the downlink scheduler is an
important component for radio resource management;
hence in the context of LTE simulation, a study
between the downlink scheduler models between the s
imulators are performed.
Performance analysis and implementation for nonbinary quasi cyclic ldpc decod...ijwmn
Non-binary low-density parity check (NB-LDPC) codes are an extension of binary LDPC codes with
significantly better performance. Although various kinds of low-complexity iterative decoding algorithms
have been proposed, there is a big challenge for VLSI implementation of NBLDPC decoders due to its high
complexity and long latency. In this brief, highly efficient check node processing scheme, which the
processing delay greatly reduced, including Min-Max decoding algorithm and check node unit are
proposed. Compare with previous works, less than 52% could be reduced for the latency of check node
unit. In addition, the efficiency of the presented techniques is design to demonstrate for the (620, 310) NBQC-
LDPC decoder.
A novel energy efficient routing algorithm for wireless sensor networks using...ijwmn
There are numerous applications for wireless sensor networks which are inevitable now a day in our daily
life. Majority of such applications which use wireless sensor networks will be in areas where the direct
human intervention is impossible. So the limited energy available in such sensors is a threat for prolonging
the life of the entire network. The need of energy efficiency in wireless sensor networks is a hot research
topic in which lot of new strategies for improvement in energy efficiency has been sought after. As
communication process consumes more energy, an energy efficient routing strategy can probably reduce
the energy consumption to a great extend. This paper gives an overview of the different routing techniques
in which mobile sinks are used to facilitate the routing process which can effectively reduce the energy use.
A new routing strategy with mobile sinks and a static sink is proposed and is compared based on the
matrices life time and average energy of the nodes with the existing Shortest Hop path (SH) algorithm. The
simulation results shows the proposed algorithm is more energy efficient than the existing one.
A COGNITIVE RADIO SCHEME FOR DYNAMIC RESOURCE ALLOCATION BASED ON QOEijwmn
This paper introduces a cognitive radio scheme based on quality of experience (QoE). QoE involves the
mobile end user’s preferences. Considering QoE can lead to an improved cognitive radio resource
management strategy. The cognitive radio scheme aims to manage the traffic flow in dynamic systems; it is
a new way of thinking about dynamic resource management in cellular systems. The Use of the cognitive
radio techniques in cellular systems will improve the resource assignment in wireless communication. The
cognitive radio is a self-aware communication system that aims to use the resource assignment in an
efficient way. The proposed algorithm is very successful at handling the call-blocking rate based on QoS
and QoE.
Efficient management of bandwidth in wireless networks is a critical factor for a successful communication system. Special features of wireless networks such user mobility and growth of wireless applications and their high bandwidth intensity create a major challenge to utilize bandwidth resources optimally. In this research, we propose a model for an adaptable network bandwidth management method that combines bandwidth reservation and bandwidth adaptation to reduce call blocking and dropping probabilities. The model is an integer program that determines whether or not to accept new calls and decides how to allocate bandwidth optimally in a way to maximize user satisfaction. The results of a simulation study show that the proposed method outperforms an existing method with respect to key performance measures such as call blocking and dropping probabilities and call time survivability. This survivability indicator is a new measure that is introduced for the first time in this paper. We also present a second tradeoff model to allow the network manager to control call dropping probability. The results of a second simulation study show that network users are better off if a zero call dropping policy is adopted as proposed in the first model.
THE EFFECT OF ACCEPTED HANDOFF SIGNAL QUALITY ON THE QUEUED COMBINED GUARD ...ijwmn
The effect of handoff call signal strength on the performance of the combined guard channels and mobile
assisted handoff with handoff queueing is studied. If a handoff call arrives and it has an acceptable signal
quality, and there are not enough channels for its service, it is queued in a finite buffer. If during its dwell
time in the queue, enough channels become available, it is immediately serviced, otherwise if its dwell time
is completed, and no channels are available for its service it is dropped. Two customer types, narrowband
(voice calls) and wideband (data, video and media) are considered. Matrix algorithmic techniques are
used to solve the balance equations to calculate the different performance measures of the system. The
results indicate that when the handoff calls with good signal strength have higher probability of being
accepted, the blocking probability of new calls of both types increase much more than for the handoff call
dropping. Average channel utilization is also increased. Increasing the size of the queue, led to further
reduction in the handoff call dropping and increase in the bandwidth utilization. When both the probability
of accepting a handoff call with good quality and the queue size is increased, the blocking probability of
new calls is not affected while the handoff call dropping in reduced. In all cases, it is noticed that the
handoff call dropping of wideband calls is less than the handoff call dropping of narrowband calls.
The Effect of Accepted Handoff Signal Quality on the Queued Combined Guard Ch...ijwmn
The effect of handoff call signal strength on the performance of the combined guard channels and mobile assisted handoff with handoff queueing is studied. If a handoff call arrives and it has an acceptable signal quality, and there are not enough channels for its service, it is queued in a finite buffer. If during its dwell time in the queue, enough channels become available, it is immediately serviced, otherwise if its dwell time is completed, and no channels are available for its service it is dropped. Two customer types, narrowband (voice calls) and wideband (data, video and media) are considered. Matrix algorithmic techniques are used to solve the balance equations to calculate the different performance measures of the system. The results indicate that when the handoff calls with good signal strength have higher probability of being accepted, the blocking probability of new calls of both types increase much more than for the handoff call dropping. Average channel utilization is also increased. Increasing the size of the queue, led to further reduction in the handoff call dropping and increase in the bandwidth utilization. When both the probability of accepting a handoff call with good quality and the queue size is increased, the blocking probability of new calls is not affected while the handoff call dropping in reduced. In all cases, it is noticed that the handoff call dropping of wideband calls is less than the handoff call dropping of narrowband calls.
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The wide-band code division multiple access (WCDMA) based 3G and beyond cellular mobile wireless networks are expected to provide a diverse range of multimedia services to mobile users with guaranteed quality of service (QoS). To serve diverse quality of service requirements of these networks it necessitates new radio resource management strategies for effective utilization of network resources with coding schemes. Call admission control (CAC) is a significant component in wireless networks to guarantee quality of service requirements and also to enhance the network resilience. In this paper capacity enhancement for WCDMA network with convolutional coding scheme is discussed and compared with block code and without coding scheme to achieve a better balance between resource utilization and quality of service provisioning. The model of this network is valid for the real-time (RT) and non-real-time (NRT) services having different data rate. Simulation results demonstrate the effectiveness of the network using convolutional code in terms of capacity enhancement and QoS of the voice and video services.
Quality of service improvement, Handoff Prioritization and Channel utilizatio...IJERA Editor
In this paper Call admission control (CAC) is a significant component in wireless networks to promise quality of service requirements and also to improve the network flexibility. The reliability is measured in terms of quality of service (QoS) and grade of service (GoS). GoS is a call‐level factor, which comprises of a new call blocking probability and handoff call blocking probability. So a robust Call Admission and Power Control Mechanism are desired. An admission control method considering the quality of service (QoS) requirements is accountable for deciding whether an incoming call/connection can be accepted or not. One major challenge in designing a CAC creates due to the fact that the cellular network has to service two major types of calls: new calls and handoff calls. The QoS performances related to these two types of calls are generally measured by new call blocking probability and handoff call dropping probability. Our work advance the dropping and handoff loss probabilities and present a coherent framework for comparative studies of presented approaches, but also helps future researches and developments of new call admission policies.
Reduce the probability of blocking for handoff and calls in cellular systems ...TELKOMNIKA JOURNAL
In cellular systems the high probability of blocking represents a big problem for users, the proposed solution by reducing the blocking probability and investigation cellular systems by method channels assignment. The aim from apaper is studying the effect the channel assignment on the value of blocking probability. The results showed that the fixe channeld assignment gives a large probability of blocking for high loads, while (FCA) reduce probability of blocking for handoff and calls according to cluster size. The cellular system representation in the case of (DCA), in (3-cell reuse) and (7-cell reuse), the results showed the first best way to reduce blocking probability and lead to reduce to approximately zero when loads that are less than 200%. Increasing the cluster size causes to reduce blocking probability. The results showed that the probability blocking for handoff less than from probability of blocking for new calls.
Performance analysis of economic model and radio resource management in heter...IJCNCJournal
Radio resource management (RRM) is the system level control of co-channel interference and other radio
transmission characteristics in wireless communication systems. In this paper we first analyze a utility
function based access selection (UFAS) method. Then we investigate a radio resource management and
network selection scheme in heterogeneous wireless network. We propose an economic model to allocate
radio resources for Code Division Multiple Access (CDMA) Networks and Wireless local Area (WLAN)
networks. Moreover we formulate and solve the optimization problem in WLAN and CDMA networks and
simulate those equations using MATLAB. Simulated results show that the proposed scheme can achieve
more number of users and more social welfare which outperform the utility function based access selection
method.
Enhanced Seamless Handoff Using Multiple Access Points in Wireless Local Area...IJERA Editor
The Mobility in wireless cellular communication systems is its backbone so as to enhance the quality of service and maintain the continuous service. Handoff is an important task in maintaining the continuity of call in cellular systems and its failure can result in ongoing call termination. In cellular mobile networks, the coverage region is divided into smaller cells in order to achieve high system capacity. Each cell has a Base-Station (BS), which provides the service to the Mobile Terminals (MTs), i.e. users equipped with phones, within its region. Before a mobile user can communicate with other user(s) in the network, a group of the frequency bands or channels should usually be assigned. The MTs is free to move across cells. When the mobile user crossing a cell boundary or by deterioration in quality of the signal in the current channel, handoff process is initiated. The scope of this project is to design 802.11 handoff schemes to solve the handoff problems in closely-spaced WLANs.The major problem in multiple WLANs are so many users trying to use same access point(AP), and interferences from nearby WLAN. The better hand off scheme based on signal strength and velocity of the nodes is proposed. The simulation results show that the proposed handoff scheme significantly reduces packet losses compared with existing handoff schemes.
Enhanced Seamless Handoff Using Multiple Access Points in Wireless Local Area...IJERA Editor
The Mobility in wireless cellular communication systems is its backbone so as to enhance the quality of service and maintain the continuous service. Handoff is an important task in maintaining the continuity of call in cellular systems and its failure can result in ongoing call termination. In cellular mobile networks, the coverage region is divided into smaller cells in order to achieve high system capacity. Each cell has a Base-Station (BS), which provides the service to the Mobile Terminals (MTs), i.e. users equipped with phones, within its region. Before a mobile user can communicate with other user(s) in the network, a group of the frequency bands or channels should usually be assigned. The MTs is free to move across cells. When the mobile user crossing a cell boundary or by deterioration in quality of the signal in the current channel, handoff process is initiated. The scope of this project is to design 802.11 handoff schemes to solve the handoff problems in closely-spaced WLANs.The major problem in multiple WLANs are so many users trying to use same access point(AP), and interferences from nearby WLAN. The better hand off scheme based on signal strength and velocity of the nodes is proposed. The simulation results show that the proposed handoff scheme significantly reduces packet losses compared with existing handoff schemes.
17 9253 denial of impedance for mobile cellular (edit ari)IAESIJEECS
Wireless network broadly utilized today incorporate, cell system, remote cross section system (WMNs), remote neighbourhood and individual zone system. The expanding interest for these systems has transformed range into a valuable asset. Consequently, there is dependably a requirement for techniques to pack more bits/Hz. In this paper, we list the purposes behind this far reaching doubt, and talk about how present and future patterns will expand the need and reasonability of multiuser collectors for both the uplink, where numerous offbeat clients will be all the while identified, and the downlink, where clients will be planned and generally orthogonal zed, yet the portable handset will in any case need to adapt to a couple of predominant meddling base stations. New results for impedance wiping out beneficiaries that utilization traditional front finishes are appeared to ease a large number of the deficiencies of earlier systems, especially for the testing uplink. This paper gives a diagram of key late research leaps forward on obstruction cancelation, and highlights framework level contemplations for future multiuser recipients.
PERFORMANCE ENHANCEMENT OF DYNAMIC CHANNEL ALLOCATION IN CELLULAR MOBILE NETW...ijcseit
In cellular mobile communication system the existing dynamic channel allocation scheme suffer from
high blocking probability and forced termination probability. To mitigate this problem, in this paper we
evaluated the performance of dynamic channel allocation scheme based on carrier-to-noise interference
ratio. In our system model, uplink power strength from a call-initiating user to the base station is
examined. This power is provided by the carrier-to-noise ratio (C/N). The channel search is conducted in
the repeated channel numbers of that cell based on the carrier-to-noise ratio so that this system provides
the low blocking probability and initiates large number of calls in dynamic channel allocation
environment. We have presented the momentous performance in blocking probability and forced
termination probability through this research.
Managing Instantly Dense Hot Spot Regions in Wireless Cellular Communication ...Eswar Publications
In a wireless communication cellular network, call activity can be more intensive in some regions than others. These high-traffic regions are called hot spot regions. In typical deployments of wireless cellular networks, traffic hot spots can arise from the non-uniform geographic distribution of the mobile users, and the heavy-tailed nature of their network usage patterns. These hot spots of activity can degrade system performance, by increasing network utilization, wireless interference, call blocking, and even call dropping from failed handoffs for mobile users. In this paper, a hierarchical cellular communication wireless network is characterized by overlapping the service area for managing the new calls users having different mobility speed. The overlapping property of the hierarchical-network provides the advantages that share the traffic load to improve the performance of wireless
cellular networks in the highly populated area where both slow speed users and high speed users are available.
Picocells are created that are underlaid to two-tier networks for handling the slow or staying speed visitor (outside registered) users. The hierarchical-networks with picocells, microcells and macrocells provide the secondary resource, which provide the services to new calls as well as handoff calls with guard channels by overflow the slow speed visitor users in picocells, slow speed local users in macrocell by sharing the frequency in
vertical as well as in horizontal directions. The picocell is installed on four wheeler vehicle may be moved at any place as per necessity and may be utilized to create picocell to handle the load of hot spot area. Such kind of picocell is known as Portable-Picocell (P-Picocell/ P2cell). The call loss probability of new calls is developed through numerical analysis. The proposed schemes are compared with the existing schemes of CAC. Results show that new proposed schemes are more efficient and handle more visitor calls by redirecting calls and sharing of load in P2cell.
Dynamic Topology Re-Configuration in Multihop Cellular Networks Using Sequent...IJERA Editor
Cellular communications has experienced explosive growth in the past two decades. Today millions of people around the world use cellular phones. Cellular phones allow a person to make or receive a call from almost anywhere. Likewise, a person is allowed to continue the phone conversation while on the move. Cellular communications is supported by an infrastructure called a cellular network, which integrates cellular phones into the public switched telephone network. The cellular network has gone through three generations.The first generation of cellular networks is analog in nature. To accommodate more cellular phone subscribers, digital TDMA (time division multiple access) and CDMA (code division multiple access) technologies are used in the second generation (2G) to increase the network capacity. With digital technologies, digitized voice can be coded and encrypted. Therefore, the 2G cellular network is also more secure. The third generation (3G) integrates cellular phones into the Internet world by providing highspeed packet-switching data transmission in addition to circuit-switching voice transmission. The 3G cellular networks have been deployed in some parts of Asia, Europe, and the United States since 2002 and will be widely deployed in the coming years. The high increase in traffic and data rate for future generations of mobile communication systems, with simultaneous requirement for reduced power consumption, makes Multihop Cellular Networks (MCNs) an attractive technology. To exploit the potentials of MCNs a new network paradigm is proposed in this paper. In addition, a novel sequential genetic algorithm (SGA) is proposed as a heuristic approximation to reconfigure the optimum relaying topology as the network traffic changes. Network coding is used to combine the uplink and downlink transmissions, and incorporate it into the optimum bidirectional relaying with ICI awareness. Numerical results have shown that the algorithms suggested in this thesis provide significant improvement with respect to the existing results, and are expected to have significant impact in the analysis and design of future cellular networks.
Performance Analysis of Wireless Networks With MDQOSIJERA Editor
In Wireless/Mobile networks various kinds of encoding schemes were used for transmission of data over a bandwidth. The desired quality and generated traffic varies with the requirement with this bandwidth. A generic video telephony may require more than 40 kbps whereas a low motion video telephony may require about 25 kbps for data transmission. From the designing point of view these requirements demands for an alternative resource planning, especially for bandwidth allocation in wireless networks. In wireless network where bandwidth is a scare resource, the system may need to block incoming user if all of the bandwidth has been used to provide highest quality of service to existing users. However this bandwidth resource planning may be unacceptable for larger application. A degradable approach to multiple users can be made on bandwidth allocation to reduce the blocking probability without degrading the quality of service to existing users.
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An efficient model for reducing soft blocking probability in wireless cellular networks
1. International Journal of Wireless & Mobile Networks (IJWMN) Vol. 6, No. 4, August 2014
AN EFFICIENT MODEL FOR REDUCING
SOFT BLOCKING PROBABILITY IN
WIRELESS CELLULAR NETWORKS
Edem E. Williams1 and Daniel E. Asuquo2
1Department of Mathematics/Statistics and Computer Science
University of Calabar, PMB 1115, Calabar-Nigeria
2Department of Computer Science
University of Uyo, PMB 1017, Uyo-Nigeria
ABSTRACT
One of the research challenges in cellular networks is the design of an efficient model that can reduce call
blocking probability and improve the quality of service (QoS) provided to mobile users. Blocking occurs
when a new call cannot be admitted into the network due to channel unavailability caused by limited
capacity or when an ongoing call cannot be continued as it moves from one base station to another due to
mobility of the user. The proposed model computes the steady state probability and resource occupancy
distribution, traffic distribution, intra-cell and inter-cell interferences from mobile users. Previously
proposed models are reviewed through which the present model is built for use in emerging wireless
networks so as to obtain improved QoS performance. The developed model is validated through simulations
in MATLAB and its equations implemented using Java Programming Language. The results obtained
indicate reduced call blocking probability below threshold.
KEYWORDS
Call Blocking Probability Reduction, Cellular Networks, Quality of Service & Computer Simulations
1. INTRODUCTION
In cellular mobile networks, call blocking can occur as either new call blocking or handoff call
blocking. The former refers to blocking of a new call request due to lack of available channel
while the later refers to blocking of a call in the new cell as the mobile moves from its originating
base station (BS) to a new BS. Ideally, during handoff or handover, the distributed mobile
transceivers move from cell to cell during an ongoing continuous communication and switching
from one cell frequency to a different cell frequency is done electronically without interruption
and without a BS operator or manual switching. Typically, a new channel is automatically
selected for the mobile unit on the new BS which will serve it. The mobile unit then automatically
switches from the current channel to the new channel and communication continues. The two
kinds of arriving calls to a cell site are shown in figure 1. Call blocking probability is one of the
quality of service (QoS) parameters for performance evaluation in wireless cellular networks.
According to [1], for better QoS it is desirable to reduce the call blocking probability. Call
blocking is perceived negatively by users because it results to degradation in required QoS and
developing an efficient model to reduce its probability in cellular networks is a growing research
aimed at improving overall cellular system performance.
DOI : 10.5121/ijwmn.2014.6407 85
2. International Journal of Wireless & Mobile Networks (IJWMN) Vol. 6, No. 4, August 2014
86
Figure 1: The two kinds of arriving calls to a cell site
The existing Visafone network suffers more of call blocking causing more calls to be rejected due
to channel unavailability, as shown in figure 2. It indicates that only a few of its BSs within the
region under study were able to carry traffic load beyond 400 Erlang per cell. This is definitely
not a good characteristic of a reliable and efficient network. The key Performance Indicators
(KPIs) usually measured by the regulatory bodies or commissions include Call Setup Success
Rate (CSSR), Call Completion Rate (CCR), Standalone Dedicated Control Channel and
Handover Success Rate (SDCCH), Call Data Rate (CDR) and Traffic Channel Congestion with or
without Handover (TCHCon). The network operators could be rated on excellent, good,
improvement, fluctuation, poor, slight decay and mostly steady below threshold on the KPIs. It is
important to note that a rating of improvement does not mean the target key performance
indicator is met. Rather, it means that the trend to reach the threshold is progressing towards the
set target of the indicator, taking into consideration the challenges the operators are facing daily.
It is therefore important that the operators continue working towards meeting the set target by
adopting improved architectures despite challenges faced in infrastructure, upgrade, and service
delivery.
Carried traffic Vs Days
1200.00
1000.00
800.00
600.00
400.00
200.00
0.00
Day1
Day3
Day5
Day7
Day9
Day11
Day13
Day15
Day17
Day19
Day21
Day23
Day25
Day27
Day29
Figure 2: Visafone BS’s Carried Traffic Load for 30 days
Erlang Traffic per cell
Several proposed models or techniques for reducing call blocking probability exist in literature
either for reducing new call blocking [2], or reducing handoff blocking [3,4,5] or reducing both
[6, 7, 8]. Whatever the case, there is a tradeoff between reducing handoff probability and new call
blocking probability. A proposed method which attempts to optimally reduce handoff failures in
mobile networks without significant increase in blocking probability of originating calls within a
cell is highly desirable. However, call blocking model could either be said to be hard or soft. In
hard call blocking models, the blocking probability is evaluated with fixed-valued parameters
regardless of the channel and traffic conditions. In a Code Division Multiple Access (CDMA)-
based network, the interference-limited nature makes it difficult to achieve accurate admission
3. International Journal of Wireless & Mobile Networks (IJWMN) Vol. 6, No. 4, August 2014
control. Because of the co-channel interference, the amount of resources (power, bandwidth)
required by each user is dependent on the number of users in the system, their geographical
locations, and physical channel conditions. In soft blocking models, the blocking probability is
evaluated taking note of interference nature of the CDMA network. This work develops and
implements a soft blocking probability reducing model for new call request in the uplink of a
CDMA cellular network. A well established CDMA network named Visafone is studied in the
South-South Zone of Nigeria’s Niger Delta region.
The rest of this paper is organized as follows: section 2 reviews existing literature on call
blocking probability estimation for both hard and soft blocking while section 3 presents the
system design for the proposed model for reducing soft blocking probability with the developed
algorithm. In section 4, the pseudo code for the developed algorithm is presented, the model’s
accuracy is validated through computer simulations in MATLAB and the equations implemented
in Java. Section 5 presents the simulation results and conclusion giving direction for future
works.
2. LITERATURE REVIEW
In a wireless network composed of several BSs serving some mobile users, user’s power is
limited to some given maximal value. The same frequency spectrum is available to all BSs (i.e.,
the frequency reuse factor is unity, 1). For a CDMA network, the interference of single user
detection is regarded as noise. MSs and BSs are both assumed to be uniformly and randomly
distributed on an infinite plane, but with different terminal densities (coverage areas). Blocking
occurs in a network when due to limited capacity at least one link on the route is not able to admit
a new call. Thus, such a user will not be able to subscribe to a particular channel. The following
section discusses the two types of call blocking for CDMA BSs.
2.1 Hard Call Blocking
Hard blocking occurs when arriving calls to a network are blocked due to lack of available
channels irrespective of the traffic characteristic and channel conditions [2, 5].
2.1.1 Erlang-B Model
The Erlang-B formula in equation (1) is used to compute hard blocking as a function of the
number of available channels and the offered load. The equation is based on analytical probability
theory and can be used when the following assumptions are satisfied.
87
i. All call attempts are Poisson distributed with exponential service time
ii. Blocked calls are cleared (BCC) in the system and that the caller tries again later
4. (1)
In equation (2.3), = probability of blocking,
= offered traffic in Erlang,
= number of channels in the cell, and
i = number of busy channels
Thus, there is no queuing and no retry for unsuccessful calls with the Erlang-B model.
2.1.2 Extended Erlang B Model
The Extended Erlang B Model uses the same formula and assumptions as Erlang-B model except
that a percentage of callers retry their calls until they are serviced. This model is commonly used
5. International Journal of Wireless Mobile Networks (IJWMN) Vol. 6, No. 4, August 2014
for standalone trunk groups with a retry probability such as a MODEM pool. The model is as
expressed in equation (2).
88
=
(2)
Where, k is the number of busy channels, N is the number of servers (trunks), A is the traffic
density in Erlang, and is the blocking probability.
The Extended Erlang B traffic model is used by telephone system designers to estimate the
number of lines required for public switch telephone network connections (trunks) or private wire
connections and takes into account the additional traffic load caused by blocked callers
immediately trying to call again if their calls are blocked. It therefore, allows retry of
unsuccessful calls and assumes infinite population of callers (sources). This traffic model may be
used where no overflow facilities are available from the trunk group being designed.
2.1.3 Erlang-C Model
In the Erlang C Model, the system is designed around the queuing theory. The caller makes one
call and is held in a queue until answered, so the formula expresses the waiting probability. Just
as the Erlang B formula, Erlang C assumes an infinite population of sources, which jointly offer
traffic of A Erlangs to N servers. However, if all the servers are busy when a request arrives from
a source, the request is queued. An unlimited number of requests may be held in the queue in this
way simultaneously.
This formula calculates the probability of queuing offered traffic, assuming that blocked calls stay
in the system until they can be handled. This formula is used to determine the number of agents or
customer service representatives needed to staff a call centre a specified desired probability of
queuing. The blocking probability or the delay probability (waiting probability) is given in
equation 3.
6. (3)
where,
A is the total traffic offered in units of erlangs
N is the number of servers; i is the number of busy servers
PW is the probability that a customer has to wait for service
It is assumed that the call arrivals can be modeled by a Poisson process and that call holding times
are described by a negative exponential distribution. A common use for Erlang C is modeling and
dimensioning call center agents in a call center environment. It can also be used to determine
bandwidth needs on data transmission circuits.
2.1.4 Engset Formula
The Engset formula is used to determine the probability of congestion occurring within a
telephony circuit group. It deals with a finite population of S sources rather than the infinite
population of sources that Erlang assumes. The formula requires that the user knows the expected
peak traffic, the number of sources (callers) and the number of circuits in the network.
Engset's formula given in equation (4) is similar to the Erlang-B formula; however one major
difference is that the Erlang's equation assumes an infinite source of calls, yielding a Poisson
arrival process, while Engset specifies a finite number of callers. Thus Engset's equation should
7. International Journal of Wireless Mobile Networks (IJWMN) Vol. 6, No. 4, August 2014
be used when the source population is small. But for population sources greater than 200 users,
extensions or customers, it becomes similar to Erlang-B model [9, 10].
=
89
!
$ (4)
!
#
where,
A = offered traffic intensity in Erlangs, from all sources
S = number of sources of traffic
N = number of circuits in group
Pb = probability of blocking or congestion
In the traditional flat cellular networks, the Erlang-B model is generally used to describe the
limitation in physical resources independent of the quality experienced on the radio interface (i.e.
hard blocking). With the increasing complexity of CDMA cellular networks, the required
assumptions are no more valid and the Erlang-B formula is found to overestimate the capacity.
Thus, to properly account for the quality of service experienced at the BS, soft blocking should be
modeled and evaluated.
2.2 Soft Call Blocking
Soft blocking is related to the amount of interference in a network. There may be plenty of
channels available at a BS but since there are many users in the same cell already, the interference
level is such that adding an additional user would increase the interference above a predetermined
threshold. The call is therefore denied. Modeling soft blocking due to interference is important
and is considered a major aspect of this paper.
In [11], three explicit analytical models (single random trials (SRT), repeated random trials
(RRT), and least busy fit (LBF)) were developed for evaluating the request blocking probability
of movie files in video-on-demand (VoD) systems under three server selection schemes. The
authors reported that the choice of server selection schemes can significantly affect the blocking
probability performance of the system, and validated the accuracy of the analytical models
through simulation.
A rapid and accurate method for evaluating the quality of service (QoS) perceived by the users in
the uplink of wireless cellular networks was proposed in [2]. In doing so, the author aimed at
accounting for the dynamics induced by the arrivals and the departures of users. The evaluated
QoS was in terms of the blocking probability for streaming users and the throughput for elastic
calls. The blocking probability of streaming users was evaluated using the Kaufman-Roberts
algorithm as in [12, 13], whereas the throughput of elastic calls was evaluated using a multi-class
processor sharing model. The research in [14] modeled soft blocking in multi-cell CDMA
systems as an independent birth and death process at each cell. The model predicts the
distribution of the number of calls connected to a base station.
In [15], the authors presented an analytical model for the estimation of the blocking probability as
a function of the offered traffic per user in a cellular environment, where capacity is determined
by hard blocking and the average number of users per cell is small. Using statistical model, they
concluded that the number of mobiles audible to a base station with the strongest signal has a
Poisson distribution, which mean is given in terms of the mean densities of mobile and base
stations and the parameters of the attenuation law. The model does not represent a tool for
detailed network planning.
In [16], the outage probability is considered a performance measure for real-time traffic in
wireless networks. They observed that the blocking and outage probabilities do not have closed-form
expressions as they strongly depend on the traffic characteristics (call duration, bit rate
requirement, etc.), the radio conditions (fading, shadowing, noise, interference, etc.), the
8. International Journal of Wireless Mobile Networks (IJWMN) Vol. 6, No. 4, August 2014
considered admission and outage policies. They assumed that the admission and outage policies
satisfy a certain monotonicity property. Their results are applied to the uplink and the downlink of
CDMA networks. In [17], a wireless network with beam-forming capabilities at the receiver is
considered. They derived the blocking probabilities for calls in the system, under different traffic
policies. For a set of co-channel transmitters, their success probabilities for being captured by
separate antenna beams are computed. These success probabilities are taken into account in the
queuing model of the system. Their analytical and numerical results show that adaptive beam-forming
at the receiver reduces the blocking probability of calls and increases the total carried
traffic of the system.
In [18], a new resource-dimensioning concept based on both the allowable noise-rise and traffic
statistics is presented. The soft blocking probability based on outage probability and the
assumption of the Poisson arrival and exponential services time are first derived, with a consistent
view on traffic dimensioning. The relationship between outage probability, soft blocking
probability and hard blocking probability is discussed. The authors in [19] focused on the call
blocking probabilities calculation in a WCDMA cell with fixed number of channels and finite
number of traffic sources. They proposed the use of the Engset Multi-rate Loss Model (EnMLM)
in the uplink direction, which incorporates local blockings. The call admission depends on the
availability of the required channels. To analyze the system, they formulated an aggregate one-dimensional
90
Markov chain.
The work in [4] studied the QoS in terms of blocking and dropping probabilities, but the
interference between the users was not taken into account explicitly. The work in [20] studied the
QoS in wireless local area and sensor networks whereas this work focuses on wireless cellular
networks. Certain models for soft blocking evaluation assumes that there is a constant number of
users in the cell, power control is perfect, and each user requires the same signal bit energy to
noise spectral density %. From the above review, it appears studies on soft blocking have not
considered interference under imperfect power control which this work considers by extending
the Kaufman-Roberts algorithm under the assumption that in reality, none of these assumptions
holds. The reason is that the number of active users in a cell is Poisson distributed with mean
arrival and exponential service time ' (. Furthermore, due to voice activity, each user is ON with
probability, ) and OFF with probability * + ) and each user requires a different % to
achieve a desired bit error rate or communication signal quality.
3. PROPOSED MODEL FOR REDUCING CALL BLOCKING
PROBABILITY
In CDMA systems, signals of each MS can be modeled as interfering noise for the others, leading
to degradation in service. Adopting imperfect power control in CDMA wireless networks is to
regulate the transmission power levels of MS such that each user obtains a satisfactory QoS. This
goal is more precisely stated as to achieve a certain SINR regardless of channel conditions while
minimizing the interference and battery usage, and hence improving the overall performance.
Modeling the uplink system interference involves taking into consideration the cell model, path
loss model, power control, and simulation parameters. The proposed system design is shown in
figure 3 and implemented in six algorithmic stages. The stages are:
(i) modeling the state of a cell
(ii) Computation of total uplink interference
(iii) Computation and comparison of maximum effective cell load with threshold
(iv) Computation of soft blocking probability when cell load threshold is exceeded
(v) Blocking or accepting new call based on computed probability
(vi) Storage of generated results and updated system parameters
9. International Journal of Wireless Mobile Networks (IJWMN) Vol. 6, No. 4, August 2014
91
Figure 3: Proposed System Design for Soft Blocking Probability Evaluation
Stage1: Modeling the State of a Cell
Cell Model: In our model, each cell blocks newly arriving calls with a state dependent probability
illustrated using Markov Chain in figure 3. The state of a cell is the number of users currently in
that cell. Other cells simply contribute interference which causes blocking with some probability,
which is assumed to depend on the state , of the current cell. We model the state of a cell as
a birth and death process and showed that the arrival rate is thinned by the blocking probability,
'* +
!, while the departure rate is ,-.
Stage 2: Computation of Total Uplink Interference
CDMA systems consider soft blocking taking note of interference from mobiles in own cell and
other cells. Therefore in the uplink, the interference experienced by a certain mobile is related to
the load distribution within the network. The total interference is computed considering own-cell
10. International Journal of Wireless Mobile Networks (IJWMN) Vol. 6, No. 4, August 2014
interference, other-cell interference, and interference due to an empty system referred to as
thermal noise i.e .//01 2 .3 4 ./567 4 . This is represented in figure 3 in the hexagonal 3-
cell structure. The more users are active at the BS, the larger is the multi-access interference at the
BS and the higher are the transmit powers required by mobiles to fulfill their %
requirements.
SINR Calculation: The signal-to-interference-noise ratio 8.9 of each and every connection in
the uplink depends on the power emitted by mobile users, own-cell interference .3, other-cell
interference ./567, thermal noise #, and multi user detection factor, : as given in equation 5.
8.9; 2
92
=?@AB?@CDEF
(5)
where the received signal, 8= + GHIJ + K/L + K7L, and is the transmit signal power, K/L
is the transmitting antenna gain, K7L is the receiving antenna gain and J is the path loss
propagation (attenuation) model from MS-BS.
Path Loss Model: Considering a BS antenna height MNof 15metres and log-normally
distributed shadowing (logF) with standard deviation of 10dB, the path loss is calculated based on
equation (6) as in [21] as follows:
J 2 OP* + O Q *PRMN STUV + *WSTUMN+21Q STUX 4 WP (6)
J = *YZW 4 [Z STUV 4 STU] 2 *[ZW 4 [Z STUV (7)
where V is the MS-BS separation in kilometers.
Users connect to the BS per cell and each mobile connecting to one BS only at any given time.
The ,/5 mobile transmits with a nonnegative uplink power level of P ^
^ _0L `
, where
_0Lis a sufficiently large upper-bound imposed for technical reasons. The received power at the
a/5 BS, b
1 , is the attenuated version of the transmitted power level, b
1 2 N
1
, where the
quantity N
1 P c N
1 c * represents the slow-varying channel gain (excluding any fading).
Stage 3: Computation and Comparison of Maximum Effective Cell load with Threshold
Power Model: When a call arrives to the cell, the noise rise is estimated and if it exceeds a
maximum predefined threshold, the call is blocked and lost. Noise rise is the ratio of total
received power at the BS, .//01, to the thermal noise power, given in equation (8) as:
9=?C@Cde
@
=?@AB?@CDEF@
@
(8)
The cell load f, is defined as the ratio of the received power from all active users to the total
received power as given in equation (9). The cell load threshold must not be exceeded for call
admission at any given state of the cell.
f= ?@AB?@CDEF
?@AB?@CDEF@
(9)
The noise rise is related to the cell load given in equation (10) as follows:
9=
?C@Cde
@
?@AB?@CDEF@
=
@
=
=
@
g@ABhg@CDEFh@
=
=
= g@CDEFh@
g@ABhg@CDEFh@
=
=
=3
(10)
Thus, instead of using noise rise, the cell load can be used to determine call admission.
11. International Journal of Wireless Mobile Networks (IJWMN) Vol. 6, No. 4, August 2014
93
Stage 4: Computation of Soft Blocking Probability when Cell load Threshold is Exceeded
Simulation Model: In CDMA network, the cell load, f is interpreted as shared resource and the
load per cell (loading factor), J as resource requirement. The application of the Kaufman-
Roberts algorithm postulates a discrete shared resource and discrete service requirements. Thus,
in order to calculate the new call blocking probabilities of different service classes, we make
discrete the loading factor and the cell load by introducing a cell load unit i of which f_0L is an
integer multiple. This will help us determine the system state probabilities. Thus, the resulting
capacity and resource requirements are:
j =
3kdl
m
and n = round
m
Since a state corresponds to the resources occupied when all users are active. We denote by
o 2f3i as the number of occupied resources by the active users and introduce a random
variable for the number of occupied resources. Still assuming no local blocking occurs, the
probability pqr that c resources are occupied in state r (bandwidth occupancy) is computed
from equation (11):
pq,=
, s
= tup + vwq, + vw 4 * + upq, + vwx (11)
for , 2 *yzy ,_0L and o ^ ,, where ,_0L is the highest reachable system state.
The resource occupancy distribution is computed according to equation (11). So, using the
theorem of total probability we derive the local blocking probability (blocking factor) as in [8] as:
y,=
pq,
{# yo (12)
Again, we denote by,, the probability that the system is in state , or the probability that state
, is reached by a new call of service | or the probability that state , is reached from state , + n as
follows:
,=
}
7=~y
7€
F
13. (13)
where,
},=‚
*yXƒn, 2 P
}, + n * + y, + n s
= „
7
Xƒn, 2 *yzy j
Py…a†…
‡ (14)
This probability depends on }, + n and y, + n which are known for all states owith
o c ,. „,ny},, y,are the parameters of the model with infinite number of sources. Still
observing the steady state probabilities given in equation (14), we obtain the total (soft) blocking
probability for a service-class | as the sum of all state probabilities , multiplied with the
blocking probabilities y,, for all reachable states as shown in equation (15):
=
kdl y,
# ˆ, (15)
14. International Journal of Wireless Mobile Networks (IJWMN) Vol. 6, No. 4, August 2014
94
Stage 5: Blocking or Accepting New Call based on Computed Probability
The developed model is aimed at enhancing the acceptance of more user calls into the system to
improve overall utilization of scare network resources. Thus, a call is blocked when the blocking
probability value is greater than the predefined threshold of 0.01given in [15] or at worst 0.02,
otherwise, it is accepted, assigned a channel with needed QoS requirement and the channel
released on call completion.
In [22], an intelligent CAC scheme was developed where fuzzy logic technique was adopted in
the admission decision. Calls admissions were termed strongly accepted, weakly accepted,
weakly rejected and strongly rejected depending on the output value of the multi-criteria
parameters in the input to the call admission controller. Their results show the capability of fuzzy
logic to improve system performance by accepting more user calls.
Stage 6: Storage of Generated Results and Updated System Parameters
At this stage, the result obtained from the computed soft blocking probability which is used to
determine the acceptance or blocking of the new call is stored. Similarly, system parameters
generated are also stored in the database so that the next state of a cell can be determined from
parameters from the previous state. The objective is to improve battery live, reduce inter-cell
interference, maintain desired service quality, and maximize utilization of network resource for
improved system performance.
4. MODEL IMPLEMENTATION
Figure 4 shows the pseudo code for the developed algorithm. The model was validated through
simulations in MATLAB and its equations were implemented in Java programming language.
The results obtained are as shown in figures 5-7 for the three performance measures listed below.
Table 1 indicates the simulation parameters.
Performance Measure 1 (‰vs. „ at different 9 values): The impact of data rates on soft
blocking for given offered load.
Performance Measure 2 (‰vs. „ at different % values): The impact of signal energy
per bit to noise spectral density for given offered load.
Performance Measure 3 (‰vs. „ at different ./567 values): The impact of other-cell
interference on soft blocking for given offered load.
In figure 5, the developed system accepts input parameters and runs numbers of simulations for
performance measure 1(i.e. model 1). The result obtained indicates that at different traffic data
rates for given offered load to the system, the soft blocking probability values are higher for
services that require higher data rates and vice versa. Nevertheless, the overall performance of the
system is improved as the soft blocking probability values obtained are less than 0.02 showing
significant reduction.
In figure 6, the system evaluates the impact of each user’s signal energy per bit to noise spectral
density % on soft blocking since in reality, it value cannot be fixed for all service classes in a
CDMA network. This parameter is sometimes used to ascertain the user’s QoS requirement. For
different values of % input for performance measure 2 (i.e. model 2), the soft blocking
probability is reduced significantly indicating that more user calls are admitted into the system for
resource sharing.
In figure 7, the impact of other-cell interference ./567 on soft blocking probability is simulated
for given traffic load considering performance measure 3 (i.e. model 3). The results indicate that
though the soft blocking probability values obtained are higher for higher values of ./567
15. International Journal of Wireless Mobile Networks (IJWMN) Vol. 6, No. 4, August 2014
indicating the negative effect of inter-cell interference on CDMA networks, the values are
significantly reduced thus allowing lower blocking rates.
95
01 while (connection request is from a new user) {
02 do
03 initiate new call request;
04 if (.//01 ^ ._0L c ./5)
05 accept new call request;
06 elseif (f 4 J ^ f_0L)
07 accept new call request;
08 else
09 { compute ‰|;
10 if ‰| ^‘’“”
11 accept new call request;
12 else
Fig. 2: Pseudo code for the Developed Algorithm
13 Block new call request; } }
14 Ignore connection request; // it’s a handoff request
15 End
Figure 4: Pseudo code for the developed algorithm
Table 1: Simulation parameters
Parameter Value
Chip rate, W 5MHz
BS thermal noise, -174dBm
Data rate, 9 144Kbps,253Kbps,384Kbps
Voice activity factor, u 0.65, 1
Signal bit energy over noise spectral density, % 3 - 7dB
Multi user detection factor, : 0.78
Transmitting antenna gain, K/L 11dBi
BS antenna height, MN 15m, omnidirectional
MS transmitted power signal 21-30dBm
Maximum cell load, f_0L 0.8
Values of other-cell interference, ./567 Š…=‹Œ - 6…=ŽŒ
Offered load, „ 0.2 – 2.0 Erlang
Loading factor, J 0.05, 0.1, 0.15, 0.2, 0.25
Maximum number of states, ,_0L 4
Number of service class, | 3
16. International Journal of Wireless Mobile Networks (IJWMN) Vol. 6, No. 4, August 2014
96
Figure 5: Soft blocking results for performance measure 1
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0
0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
Offered load (Erlang)
Figure 6a: Soft blocking results for performance measure 2 in MATLAB
Blocking probability
3dB
5dB
6dB
17. International Journal of Wireless Mobile Networks (IJWMN) Vol. 6, No. 4, August 2014
97
Figure 6b: Soft blocking results for performance measure 2 in JAVA
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0
Iother = 4e-18
Iother = 2e-18
0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
Offered load (Erlang)
Blocking probability
Figure 7a: Soft blocking results for performance measure 3 in MATLAB
Figure 7b: Soft blocking results for performance measure 3 in JAVA
18. International Journal of Wireless Mobile Networks (IJWMN) Vol. 6, No. 4, August 2014
5. CONCLUSION
We started from the verification that call blocking perceived negatively by users in mobile
cellular networks actually exist at an alarming rate in a well established CDMA network -
Visafone in the region under study. As a solution, we developed a model for soft blocking
probability evaluation by extending the Kaufman-Roberts algorithm which allows an efficient
approximation of the blocking probabilities. We validate our results by simulation and show that
the approximation yields accurate results even for large other-cell interferences and low user
activities. Moreover, the impact of the model’s parameters on soft blocking probability has been
studied. This work showed that an efficient and fair resource management is possible for
supporting traffic with strict QoS requirements. The results are particularly useful for operators
who aim to predict the QoS of their networks for several combinations of the parameters (for
dimensioning, prediction or optimization).
The imperfect power control framework considered addresses three main issues while ensuring
that MSs achieve their QoS targets. First, it reduces the overall interference from neighboring
cells, which is important for frequency reuse in multi-cell CDMA network. Second, it reduces the
battery usage of MSs according to their individual preferences. Third, it mitigates the near-far
problem by ensuring that MSs closest to the BS do not overpower the system at the detriment of
those farther away.
98
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Authors
Dr Edem Williams is an Associate Professor of Computer Science at University of
Calabar, Nigeria. He is also a Visiting Professor at Computer Science Department,
University of Port Harcourt, Nigeria. He holds a PhD in Computer Science from
University of Lagos, Nigeria, MSc in Computer Science from Manchester University and
BSc in Computer Science from Obafemi Awolowo University, Ile-Ife, Nigeria. He is a
member of IEEE, NCS and CPN. His research interest includes Artificial Intelligence,
Database Management, Data Communications and Networks.
Daniel Asuquo received BSc in Computer Science from University of Calabar, Nigeria
in 2002 and MSc in Computer Science from University of Ibadan, Nigeria in 2007. He is
a lecturer in the department of Computer Science, University of Uyo, Nigeria. His
research interest includes Wireless Communications and Mobile Networks, Web
programming, Software Engineering, and Object-Oriented Programming. He is a member
of Computer Professionals and Registration Council of Nigeria (CPN) and an associate
member of Nigeria Computer Society (NCS).