This document discusses efficient channel assignment schemes in 802.11 wireless local area networks (WLANs) to reduce co-channel interference and improve network performance. It reviews several channel assignment algorithms including Least Congested Channel Search (LCCS), Dynamic Channel Assignment, Peer Assisted Channel Assignment for Home Wireless LANs (PACA), channel hopping approaches, and measurement-based algorithms. It also discusses using integer linear programming (ILP) and different mathematical formulations to model the channel assignment problem and minimize interference between access points in a WLAN.
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.
A 3 – 14 GHZ LOW NOISE AMPLIFIER FOR ULTRA WIDE BAND APPLICATIONSVLSICS Design
This paper presents an ultra wide band (UWB) low noise amplifier (LNA) with very high gain, better input matching, low noise figure, better linearity and low power consumption. A dual source degenerated resistive current reuse is used as an input stage and a cascode stage with shunt-series peaking is used to enhance the bandwidth and reverse isolation. The proposed LNA achieves a peak power gain of 20.92 dB at 9 GHz while achieving a gain greater than 20.3 dB over 3 – 14 GHz bandwidth. The achieved noise figure is in the range of 3.72 – 4.78 dB, while the input matching and the output matching are kept below – 9 dB and –10 dB respectively. The reverse isolation is below –52 dB throughout the entire band. This LNA ensures better linearity with an IIP3 of 4 dBm at 9 GHz with very low power consumption of 5.876 mW at 1 V supply.
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.
Downlink beamforming and admissin control for spectrum sharing cognitive radi...acijjournal
n this paper, to detect the moving objects between frames in compressed video and to obtain the bes
t
compression video
and the noiseless video. We describe a video in which frames by classifying
macroblocks (MB), and describe motion estimation (ME), motion vector field (MV) and motion
compensation (MC). we propose to classify Macroblocks of each video frame into different
classes and use
this class information to describe the frame content based on the motion vector. MB class informatio
n
video applications such as shot change detection, motion discontinuity detection, Outlier rejection
for
global motion estimation. To reduc
e the noise and to improve the clarity of the compressed video by using
contrast limited adaptive histogram equalization (CLAHE) Algorithm
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.
A 3 – 14 GHZ LOW NOISE AMPLIFIER FOR ULTRA WIDE BAND APPLICATIONSVLSICS Design
This paper presents an ultra wide band (UWB) low noise amplifier (LNA) with very high gain, better input matching, low noise figure, better linearity and low power consumption. A dual source degenerated resistive current reuse is used as an input stage and a cascode stage with shunt-series peaking is used to enhance the bandwidth and reverse isolation. The proposed LNA achieves a peak power gain of 20.92 dB at 9 GHz while achieving a gain greater than 20.3 dB over 3 – 14 GHz bandwidth. The achieved noise figure is in the range of 3.72 – 4.78 dB, while the input matching and the output matching are kept below – 9 dB and –10 dB respectively. The reverse isolation is below –52 dB throughout the entire band. This LNA ensures better linearity with an IIP3 of 4 dBm at 9 GHz with very low power consumption of 5.876 mW at 1 V supply.
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.
Downlink beamforming and admissin control for spectrum sharing cognitive radi...acijjournal
n this paper, to detect the moving objects between frames in compressed video and to obtain the bes
t
compression video
and the noiseless video. We describe a video in which frames by classifying
macroblocks (MB), and describe motion estimation (ME), motion vector field (MV) and motion
compensation (MC). we propose to classify Macroblocks of each video frame into different
classes and use
this class information to describe the frame content based on the motion vector. MB class informatio
n
video applications such as shot change detection, motion discontinuity detection, Outlier rejection
for
global motion estimation. To reduc
e the noise and to improve the clarity of the compressed video by using
contrast limited adaptive histogram equalization (CLAHE) Algorithm
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
IACR: an interference-aware channel reservation for wireless sensor networksIJECEIAES
In battery-based wireless sensor networks, energy-efficient operation is one of the most important factors. Especially, in order to improve energy efficiency in wireless sensor networks, various studies on low power operation have been actively conducted in the MAC layer. In recent years, mutual interference among various radio technologies using the same radio frequency band has become a serious problem. Wi-Fi, ZigBee, and Bluetooth use the same frequency band of 2.4GHz at the same time, which causes various signal interference problems. In this paper, we propose a novel channel reservation scheme, called IACR, to improve the energy efficiency of wireless sensor networks in an environment where interference occurs between various wireless technologies. The proposed scheme inserts a PN code into a long preamble for exchanging transmission status information between a transmitting node and a receiving node, thereby improving the transmission success probability while receiving less influence on transmission of other radio technologies. We performed an event-driven simulation and an experiment to measure the signal detection rate. As a result, it can be seen that the proposed technique reduces the packet drop rate by 15% and increases the discoverable distance of the control packet for channel reservation.
In pursuit of high transmission capacity, people have been tried many ways. For
example, they pave more cables or use the TDM (time domain multiplexer) to
improve the transmission capacity. But in these traditional ways, signals could
become weaker in power through the fiber link. And the further they are transmitted,
the weaker the signals will be until they can not be detected. With the advanced of
technology, optical amplifier which is a better solution to improve the transmission
capacity came around. It can strengthen the attenuated signals and even can bring
them back to the original level. And now it is mainly applied in DWDM technology
so that DWDM technology can support long-haul transmission.
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.
An approach to control inter cellular interference using load matrix in multi...eSAT Journals
Abstract
This paper deals with reduction of inter cellular interference in Multi-carrier communication systems. In the past, Load Matrix(LM) is proposed to allocate power to different users in a network based upon Signal to noise plus interference ratio (SNIR) so as to reduce inter cellular interference and is observed for single carrier systems. In Multi carrier systems the SNIR is affected distinctly in each carrier thus a single SNIR for power allocation is not optimal. In this paper, to obtain the optimization of power allocation in Multi-Carrier system, Load Matrix coding with bifurcated SNIR (LM-BFSNIR) is proposed. Using this approach it is observed that inter cellular interference is reduced better when compared to a single carrier system evaluated over a 3GPP-LTE standard.
Keywords−Power allocation, Inter cellular interference, Multi-Carrier mobile Communication system.
Improving The Performance Of Multiuser OFDM Wireless System With UWB ChannelIJTET Journal
The multi user OFDM system can be used to produce a highly flexible and effective communication
system. In the existing multi user OFDM system, resource allocation to each user is the major problem. Also the existing
multi user OFDM system uses frequency diversity technique that requires sparse bandwidth and multiple receivers
improving the complexity. In order to increase the system performance, the proposed system allows multiple user data to
be multiplexed together to form a single OFDM symbol where the resources are allocated equally to all users. The
proposed multiuser OFDM system achieves double the capacity and better performance in terms of Signal-to-Noise Ratio
and Bit Error Rate of a single user OFDM system and the UWB channel is used to securely transmit the data through the
channel. Also, the proposed system reduces the receiver complexity by using polarization diversity to receive the
multipath components for multiple users.
Improvement of crankshaft MAC protocol for wireless sensor networks: a simula...IJECEIAES
Due to the dramatic growth in the use of Wireless Sensor Network (WSN) applications ranging from environment and habitat monitoring to tracking and surveillance, network research in WSN protocols has been very active in the last decade. With battery-powered sensors operating in unattended environments, energy conservation becomes the key technique for improving WSN lifetimes. WSN Medium Access Control (MAC) protocols address energy awareness and reduced duty cycles. The focus of this study is to investigate, through simulation, the effect of variations in various factors that influence the performance results of WSNs. Using MiXiM framework with OMNeT++ simulator, this simulation study proposes modifications in Crankshaft MAC protocol in order to improve its performance. The impact of duration and number of slots, degree of connectivity among the nodes, mobility speed and mobility update interval and also, the impact of sending data packets without preambles are investigated. Based on the simulation results, an improved version of the Crankshaft protocol for WSN is suggested and a comparative study of the performances of the original and improved protocol is presented. The results clearly indicate the superiority of the improved protocol over its original version.
Dynamic resource allocation for opportunistic software-defined IoT networks: s...IJECEIAES
Several wireless technologies have recently emerged to enable efficient and scalable Internet-of-Things (IoT) networking. Cognitive radio (CR) technology, enabled by software-defined radios, is considered one of the main IoT-enabling technologies that can provide opportunistic wireless access to a large number of connected IoT devices. An important challenge in this domain is how to dynamically enable IoT transmissions while achieving efficient spectrum usage with a minimum total power consumption under interference and traffic demand uncertainty. Toward this end, we propose a dynamic bandwidth/channel/power allocation algorithm that aims at maximizing the overall network’s throughput while selecting the set of power resulting in the minimum total transmission power. This problem can be formulated as a two-stage binary linear stochastic programming. Because the interference over different channels is a continuous random variable and noting that the interference statistics are highly correlated, a suboptimal sampling solution is proposed. Our proposed algorithm is an adaptive algorithm that is to be periodically conducted over time to consider the changes of the channel and interference conditions. Numerical results indicate that our proposed algorithm significantly increases the number of simultaneous IoT transmissions compared to a typical algorithm, and hence, the achieved throughput is improved.
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.
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.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
IACR: an interference-aware channel reservation for wireless sensor networksIJECEIAES
In battery-based wireless sensor networks, energy-efficient operation is one of the most important factors. Especially, in order to improve energy efficiency in wireless sensor networks, various studies on low power operation have been actively conducted in the MAC layer. In recent years, mutual interference among various radio technologies using the same radio frequency band has become a serious problem. Wi-Fi, ZigBee, and Bluetooth use the same frequency band of 2.4GHz at the same time, which causes various signal interference problems. In this paper, we propose a novel channel reservation scheme, called IACR, to improve the energy efficiency of wireless sensor networks in an environment where interference occurs between various wireless technologies. The proposed scheme inserts a PN code into a long preamble for exchanging transmission status information between a transmitting node and a receiving node, thereby improving the transmission success probability while receiving less influence on transmission of other radio technologies. We performed an event-driven simulation and an experiment to measure the signal detection rate. As a result, it can be seen that the proposed technique reduces the packet drop rate by 15% and increases the discoverable distance of the control packet for channel reservation.
In pursuit of high transmission capacity, people have been tried many ways. For
example, they pave more cables or use the TDM (time domain multiplexer) to
improve the transmission capacity. But in these traditional ways, signals could
become weaker in power through the fiber link. And the further they are transmitted,
the weaker the signals will be until they can not be detected. With the advanced of
technology, optical amplifier which is a better solution to improve the transmission
capacity came around. It can strengthen the attenuated signals and even can bring
them back to the original level. And now it is mainly applied in DWDM technology
so that DWDM technology can support long-haul transmission.
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.
An approach to control inter cellular interference using load matrix in multi...eSAT Journals
Abstract
This paper deals with reduction of inter cellular interference in Multi-carrier communication systems. In the past, Load Matrix(LM) is proposed to allocate power to different users in a network based upon Signal to noise plus interference ratio (SNIR) so as to reduce inter cellular interference and is observed for single carrier systems. In Multi carrier systems the SNIR is affected distinctly in each carrier thus a single SNIR for power allocation is not optimal. In this paper, to obtain the optimization of power allocation in Multi-Carrier system, Load Matrix coding with bifurcated SNIR (LM-BFSNIR) is proposed. Using this approach it is observed that inter cellular interference is reduced better when compared to a single carrier system evaluated over a 3GPP-LTE standard.
Keywords−Power allocation, Inter cellular interference, Multi-Carrier mobile Communication system.
Improving The Performance Of Multiuser OFDM Wireless System With UWB ChannelIJTET Journal
The multi user OFDM system can be used to produce a highly flexible and effective communication
system. In the existing multi user OFDM system, resource allocation to each user is the major problem. Also the existing
multi user OFDM system uses frequency diversity technique that requires sparse bandwidth and multiple receivers
improving the complexity. In order to increase the system performance, the proposed system allows multiple user data to
be multiplexed together to form a single OFDM symbol where the resources are allocated equally to all users. The
proposed multiuser OFDM system achieves double the capacity and better performance in terms of Signal-to-Noise Ratio
and Bit Error Rate of a single user OFDM system and the UWB channel is used to securely transmit the data through the
channel. Also, the proposed system reduces the receiver complexity by using polarization diversity to receive the
multipath components for multiple users.
Improvement of crankshaft MAC protocol for wireless sensor networks: a simula...IJECEIAES
Due to the dramatic growth in the use of Wireless Sensor Network (WSN) applications ranging from environment and habitat monitoring to tracking and surveillance, network research in WSN protocols has been very active in the last decade. With battery-powered sensors operating in unattended environments, energy conservation becomes the key technique for improving WSN lifetimes. WSN Medium Access Control (MAC) protocols address energy awareness and reduced duty cycles. The focus of this study is to investigate, through simulation, the effect of variations in various factors that influence the performance results of WSNs. Using MiXiM framework with OMNeT++ simulator, this simulation study proposes modifications in Crankshaft MAC protocol in order to improve its performance. The impact of duration and number of slots, degree of connectivity among the nodes, mobility speed and mobility update interval and also, the impact of sending data packets without preambles are investigated. Based on the simulation results, an improved version of the Crankshaft protocol for WSN is suggested and a comparative study of the performances of the original and improved protocol is presented. The results clearly indicate the superiority of the improved protocol over its original version.
Dynamic resource allocation for opportunistic software-defined IoT networks: s...IJECEIAES
Several wireless technologies have recently emerged to enable efficient and scalable Internet-of-Things (IoT) networking. Cognitive radio (CR) technology, enabled by software-defined radios, is considered one of the main IoT-enabling technologies that can provide opportunistic wireless access to a large number of connected IoT devices. An important challenge in this domain is how to dynamically enable IoT transmissions while achieving efficient spectrum usage with a minimum total power consumption under interference and traffic demand uncertainty. Toward this end, we propose a dynamic bandwidth/channel/power allocation algorithm that aims at maximizing the overall network’s throughput while selecting the set of power resulting in the minimum total transmission power. This problem can be formulated as a two-stage binary linear stochastic programming. Because the interference over different channels is a continuous random variable and noting that the interference statistics are highly correlated, a suboptimal sampling solution is proposed. Our proposed algorithm is an adaptive algorithm that is to be periodically conducted over time to consider the changes of the channel and interference conditions. Numerical results indicate that our proposed algorithm significantly increases the number of simultaneous IoT transmissions compared to a typical algorithm, and hence, the achieved throughput is improved.
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.
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.
6 Reasons Why Building a Personal Brand Can Land You Your Dream JobKayla Joy Mele
Companies these days want to know if you can go 'digital'. Resume's can show what you have done in words, why not share a hands-on experience? In 16 slides I share with you why you should have a personal brand and portfolio site and how to get started.
L'Agence Aisne Tourisme et Orange Labs Networks ont signé un partenariat permettant de mesurer la fréquentation touristique à partir des flux téléphoniques. Première restitution avec l'événement 'Circuit historique de Laon et de l'Aisne'.
155 missions d'accompagnement des professionnels du tourisme menées en 2015 par les équipes de l'Agence Aisne Tourisme. Découvrez-les en parcourant l'infographie.
INTERFERENCE-AWARE CHANNEL ASSIGNMENT FOR MAXIMIZING THROUGHPUT IN WMN pijans
Wireless Mesh network (WMN) is dynamically self-organizing and self-configured, with the nodes in the
network automatically establishing an ad-hoc network and maintaining the mesh connectivity. The ability
to use multiple-radios and multiple channels can be cashed to increase aggregate throughput of wireless
mesh network. Thus the efficient use of available interfaces and channels without interference becomes
the key factor. In this paper we propose interference aware clustered based channel assignment schemes
which minimizes the interference and increases throughput. In our proposed scheme we have given
priority to minimize interference from nearby mesh nodes in interference range than maximizing channel
diversity. We simulated our proposed work using NS-3 and results show that our scheme improves
network performance than BFSCA and Distributed Greedy CA.
A Study on Access Point Selection Algorithms in Wireless Mesh NetworksEswar Publications
In IEEE 802.11 based wireless mesh network (WMN), a mesh client often finds multiple access points (AP) to associate with. How to select the best AP is the open research problem. The traditional AP selection method defined by IEEE 802.11 standard is based on received signal strength. This method is proven inefficient as it does not consider many important factors such as channel conditions, AP load, etc. Many alternate solutions have been proposed so far in the literature, but they are all focused on wireless local area network (WLAN) environment. As there are significant differences between WLAN and WMN, all these proposed association mechanisms must be redesigned to fit into WMN environment. This paper studies the AP selection problem in the context of WMN. We critically analyze the existing work and identify technical challenges involved in AP selection problem. This paper also provides directions to design the metrics of AP selection method in WMN.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
A Survey of Various Routing and Channel Assignment Strategies for MR-MC WMNsijsrd.com
One fundamental problem of WMNs with a limited number of radio interfaces and orthogonal channels is that the performance degrades significantly as the network size grows. This results from increased interference between nodes and diminished spatial reuse over the network. A WMN node needs to share a common channel with each of its neighbours in the communication range, requiring it to set up a virtual link. Moreover, to reduce network interference, a node should minimize the number of neighbours that it shares a common channel with. The objective of a channel assignment strategy is to ensure efficient utilization of the available channels (e.g., by minimizing interference) while maximizing connectivity in the network. However, since these two requirements are conflicting with each other, the goal is to achieve a balance between these two. The major constraints which need to be satisfied by a channel assignment scheme include fixed number of channels in the network, limited number of radios in mesh nodes, common channel between two communicating nodes, and limited channel capacity. Also, a channel assignment scheme should take the amount of traffic load supported by each mesh node into consideration.
A Proximity based Retransmission Scheme for Power Line Ad-hoc LAN ijdpsjournal
Power line as an alternative for data transmission is being explored, and also being used to a certain extent. But from the data transfer point of view, power line, as a channel is highly dynamic and hence not quite suitable. To covert the office or home wiring system to a Local Area Network (LAN), adaptive
changes are to be made to the existing protocols. In this paper, a slotted transmission scheme is suggested, in which usable timeslots are found out by physically sensing the media. Common usable timeslots for the sender-receiver pair are used for communication. But these will not ensure safe packet
delivery since packets may be corrupted on the way during propagation from sender to receiver. Therefore, we also suggest a proximity based retransmission scheme where each machine in the LAN, buffers good packet and machines close to the receiver retransmit on receiving a NACK.
Characterizing wi fi-link_in_open_outdoor_netwoSalah Amean
long distance wifi is really an important concept to deliver internet to remote places in developed countries as well as the poor and developing countries.
Channel Allocation and Routing in Wireless Mesh Networks: A survey and qualit...ijwmn
In order to avoid transmission's collisions and improve network performances in wireless mesh networks (WMNs), a reliable and efficient medium access control (MAC) protocol and a good channel allocation are needed. Allowing multiple channels use in the same network is often presented as a possible way to improve the network capacity. As IEEE 802.11, IEEE 802.15 and IEEE 802.16 standards provide more than one channel, thus a trivial way to improve the network performances is to allow transmission on multiple channels in each network node. A lot of research work have been conducted in the area of multi-channel allocation in order to improve the aggregate bandwidth of the hole network. In this paper, we focus our attention on the proposals for solving the channel allocation problem for Multi-Transceiver per node in the backbone level using the IEEE 802.11s technology. We classify these proposals into three categories. The first one consists on channel allocation proposals done at the MAC level independently to the other layers. The second one consists on a channel allocation approaches done by a modified MAC collaborating with upper layers. Finally, the third category concerns channel allocation methods implemented in a new layer resulting from a common-layer design between MAC and Network layer. For each category, the existing multi-channel protocols and their channel allocation approaches are identified. A qualitative comparison is conducted according to the advantages that they present, the limitations and problems they are facing, and the performances they are claiming to offer.
Capacity Improvement of Cellular System Using Fractional Frequency Reuse (FFR)IJEEE
Today wireless communication is mostly used rather than wired communication, due to remote location reach ability, less fault occurrence, less time to commissioning and low cost etc. But wireless network has less frequency spectrum to cover the whole world. To improve the capacity of cellular system in a limited spectrum without major technological changes, frequency is reused in cells. But it offers interferences mostly for cell edge users. To solve the problem of spectral congestion and user capacity, fractional frequency reuse is used. This paper gives idea about different frequency reuse factors, fractional frequency reuse and super cell with sectoring to improve the capacity of cellular system.
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.
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
Performance and interference analysis of 802.11 g wireless networkijwmn
This paper mainly presents Access Point s’ (APs’) p
erformance and co-channel, adjacent channel
interference according to 802.11g standard. Firstly
, our study illustrates the performance of one AP,
including its coverage performance, load-carrying p
roperties and fairness. Next we propose the details
about co-channel, adjacent channel interference whi
ch should be paid attention to in deploying network
services. Then, performance analyses are evaluated
by simulation and real test for a dense wireless
network. Our contribution is that the co-channel, a
djacent channel interference analysis, the simulati
on
and test results can be the basis offered to networ
k operators
Maintaining Data Confidentiality in Association Rule Mining in Distributed En...IJSRD
The data in real world applications is distributed at multiple locations, and the owner of the databases may be different people. Thus to perform mining task, the data needs to be kept at central location which causes threat to the privacy of corporate data. Hence the key challenge is to applying mining on distributed source data with preserving privacy of corporate data. The system addresses the problem of incrementally mining frequent itemsets in dynamic environment. The assumption made here is that, after initial mining the source undergoes into small changes in each time. The privacy of data should not be threatened by an adversary i.e. the miner and target database owner should not be able to recover original data from transformed data.
Performance and Emission characteristics of a Single Cylinder Four Stroke Die...IJSRD
The current trends in CI engine are to use Water-diesel emulsion as alternative fuel. It can be employed directly to the existing CI Engine system with no additional modifications. This system helps in reduction of NOx as well as PM, which in turn improve the combustion efficiency of the engine. However there are still investigations have to be done. The current work mainly concentrated on diesel engine run on water-diesel emulsions and its effect on engine performance and emissions were studied. The various loads were applied on a constant speed diesel engine run on water-diesel emulsions of varying ratios of 0.2:1, 0.3:1. 0.4:1 and 0.5:1. Emission and performance characteristics were measured and were compared with base diesel operation. The emissions like NOx and smoke density were found to decrease greatly and brake thermal efficiency was found to increase at high loads. Smoke level was 4.2 BSU and 3 BSU for base diesel and water diesel emulsion of 0.4. The ignition delay was found to increase with water diesel emulsions. This also increased the maximum rate of pressure rise and peak pressure. The engine was found to run rough with water-diesel emulsions. The optimal water-diesel ratio was found to be 0.4:1 by weight. HC and CO emissions were found to increase with water diesel emulsions.
Preclusion of High and Low Pressure In Boiler by Using LABVIEWIJSRD
Pressure is an important physical parameter to be controlled in process boiler, heat exchanger, nuclear reactor and steam carrying pipeline. In the article the issue has been face in boiler operation due to pressure is handled. In boiler, the problem is due to maximum and minimum range of pressure. Due to the issues there is a chance to causes the hazop. To avoid such the problem the high and low pressure in boiler has to control. In the paper such the problem has sorted out by implementing ON-OFF control. Here the proposed control action for pressure control is implemented with the help of LabVIEW (Laboratory Virtual Instrument Engineering Workbench) software and NI ELVIS hardware. In the idea the boiler’s low range and high is monitored and controlled valve desirably. And also the high range and low range of pressure in the boiler is signified to plant operator by alarm signal.
Prevention and Detection of Man in the Middle Attack on AODV ProtocolIJSRD
In this paper it is discuss about AODV protocol and security attacks and man in the middle attack in detail. AODV Protocol is use to find route and very important protocol for communication in wireless network. So AODV protocol should be Secured and it is a big challenge. There are various attacks that occur on it. Here in this paper it discussed about the detection and preventions of man-in-the-middle attack in detail.
Comparative Analysis of PAPR Reduction Techniques in OFDM Using Precoding Tec...IJSRD
In this modern era, Orthogonal Frequency Division Multiplexing (OFDM) has been proved to be an explicit promising technique for wired and wireless systems because of its several advantages like high spectral efficiency, robustness against frequency selective fading, relatively simple receiver implementation etc. Besides having a number of advantages OFDM suffers from few disadvantages like high Peak to Average Power Ratio (PAPR), Intercarrier Interference (ICI), Intersymbol Interference (ISI) etc. These detrimental effects, if not compensated properly and timely, can result in system performance degradation. This paper mainly concentrates on reduction of PAPR.A comparisons have been made between various precoding techniques against conventional OFDM.
Evaluation the Effect of Machining Parameters on MRR of Mild SteelIJSRD
Today’s life is totally based on Internet. Now a days people cannot imagine life without Internet. Information and communication technology plays vital role in today’s online networked society. In today’s life, we are very close to the online social networks. Online social networks are used for posting and sharing information across various social networking sites. But user’s privacy is not maintained by online social networks. For maintaining users sensitive information’s privacy online social networks provides little or no support. For filtering unwanted messages we propose a system using machine learning (ML). Using machine learning in soft classifier content based filtering performed. In proposed system filtering rules (FR’s) are provided for content independent filtering.. Blacklists are used for more flexibility by which filtering choices are increased. Proposed system provides security to the Online Social Networks.
Filter unwanted messages from walls and blocking nonlegitimate user in osnIJSRD
Today’s life is totally based on Internet. Now a days people cannot imagine life without Internet. Information and communication technology plays vital role in today’s online networked society. In today’s life, we are very close to the online social networks. Online social networks are used for posting and sharing information across various social networking sites. But user’s privacy is not maintained by online social networks. For maintaining users sensitive information’s privacy online social networks provides little or no support. For filtering unwanted messages we propose a system using machine learning (ML). Using machine learning in soft classifier content based filtering performed. In proposed system filtering rules (FR’s) are provided for content independent filtering.. Blacklists are used for more flexibility by which filtering choices are increased. Proposed system provides security to the Online Social Networks.
Keystroke Dynamics Authentication with Project Management SystemIJSRD
Generally user authentication is done using username and password that is called as login process. This login process is not more secure because, however a login session is still unprotected to impersonator when the user leaves his computer without logging off. Keystroke dynamics methods can be made useful to verify a user by extracting some typing features then, after the authentication process has successfully ended. From the last decade several studies proposed the use of keystroke dynamics as a behavioral biometric tool to verify users. We propose a new method, for representing the keystroke patterns by joining similar pairs of consecutive keystrokes. The above proposed method is used to consider clustering the di-graphs which are based on their temporal features. In this project, authentication system is provide to project management system that make more Secure management system without acknowledging unauthorized user. The Project Management System addresses the management of software projects. It provides the framework for organizing and managing resources in such a way that these resources deliver all the work required to complete a software project within defined scope, time and cost constraints. The system applies only to the management of software projects and is a tool that facilitates decision making.
Diagnosing lungs cancer Using Neural NetworksIJSRD
Artificial Neural Networks is the new technology. It is the branch of Artificial Intelligence and also it is an accepted new technology. Now a days Neural Networks Plays a Vital role in Medicine, Particularly in some fields such as cardiology, oncology etc. And also it has many applications in many areas like Science and Technology, Education, Business, Business and Manufacturing, etc. Neural Networks is most useful for making the decision more Effective. In this Paper, by the use of Neural Networks how the severe disease Lungs Cancer has been diagnosed more effectively. This Paper discussed about how the Lungs cancer can be identified effectively in earlier stages and diagnosed using Neural Networks and some devices. The Neural Networks has been successfully applied in Carcinogenesis. The main aim of this research is by the use of Neural Networks the Carcinogenesis can be diagnosed more cost-effective, easy to use techniques and methods. This Paper discussed about how the Lungs cancer can be identified effectively in earlier stages and diagnosed using Neural Networks and some devices. Sputum Cytology is used to detect the Lungs Cancer in Early stages.
A Survey on Sentiment Analysis and Opinion MiningIJSRD
In Today’s world, the social media has given web users a place for expressing and sharing their thoughts and opinions on different topics or events. For this purpose, the opinion mining has gained the importance. Sentiment classification and Opinion Mining is the study of people’s opinion, emotions, attitude towards the product, services, etc. Sentiment Analysis and Opinion Mining are the two interchangeable terms. There are various approaches and techniques exist for Sentiment Analysis like Naïve Bayes, Decision Trees, Support Vector Machines, Random Forests, Maximum Entropy, etc. Opinion mining is a useful and beneficial way to scientific surveys, political polls, market research and business intelligence, etc. This paper presents a literature review of various techniques used for opinion mining and sentiment analysis.
A Defect Prediction Model for Software Product based on ANFISIJSRD
Artificial intelligence techniques are day by day getting involvement in all the classification and prediction based process like environmental monitoring, stock exchange conditions, biomedical diagnosis, software engineering etc. However still there are yet to be simplify the challenges of selecting training criteria for design of artificial intelligence models used for prediction of results. This work focus on the defect prediction mechanism development using software metric data of KC1.We have taken subtractive clustering approach for generation of fuzzy inference system (FIS).The FIS rules are generated at different radius of influence of input attribute vectors and the developed rules are further modified by ANFIS technique to obtain the prediction of number of defects in software project using fuzzy logic system.
Experimental Investigation of Granulated Blast Furnace Slag ond Quarry Dust a...IJSRD
In this experimental work ninety nine cubes has been prepared having dimension 70.7x70.7x70.7 mm are cast as per IS:4031 (2000). In this experimental investigation cement mortar mix 1:3 by volume were selected for 0%, 20%, 40%, 60%, 80% and 100% partially replacement of natural sand (NS) by Granulated blast furnace slag (GBFS) and quarry dust (QD) [3 cubes on each parameter respectively] for W/C ratio of 0.55 respectively. All the cubes were tested under compressive testing machine. To compare the average compressive strength of natural sand (NS) with granulated blast furnace slag (GBFS) and quarry dust (QD).
Product Quality Analysis based on online ReviewsIJSRD
Customers satisfaction is the most important criteria before buying any product. Technology today has grown to such an extent that every smallest possible query is found on internet. An individual can express his reviews towards a product through Internet. This allows others to have a brief idea about the product before buying one for them. In this paper, we take into account all the challenges and limitations encountered while reading the online reviews and time being consumed in understanding quality of the product from the reviews. We include several methods and algorithms that help the consumer to understand the Quality of the product in better way.
Solving Fuzzy Matrix Games Defuzzificated by Trapezoidal Parabolic Fuzzy NumbersIJSRD
The matrix game theory gives a mathematical background for dealing with competitive or antagonistic situations arise in many parts of real life. Matrix games have been extensively studied and successfully applied to many fields such as economics, business, management and e-commerce as well as advertising. This paper deals with two-person matrix games whose elements of pay-off matrix are fuzzy numbers. Then the corresponding matrix game has been converted into crisp game using defuzzification techniques. The value of the matrix game for each player is obtained by solving corresponding crisp game problems using the existing method. Finally, to illustrate the proposed methodology, a practical and realistic numerical example has been applied for different defuzzification methods and the obtained results have been compared
Study of Clustering of Data Base in Education Sector Using Data MiningIJSRD
Data mining is a technology used in different disciplines to search for significant relationships among variables in n number of data sets. Data mining is frequently used in all types’ areas as well as applications. In this paper the application of data mining is attached with the field of education. The relationship between student’s university entrance examination results and their success was studied using cluster analysis and k-means algorithm techniques.
Fault Tolerance in Big Data Processing Using Heartbeat Messages and Data Repl...IJSRD
Big data is a popular term used to define the exponential evolution and availability of data, includes both structured and unstructured data. The volatile progression of demands on big data processing imposes heavy burden on computation, communication and storage in geographically distributed data centers. Hence it is necessary to minimize the cost of big data processing, which also includes fault tolerance cost. Big Data processing involves two types of faults: node failure and data loss. Both the faults can be recovered using heartbeat messages. Here heartbeat messages acts as an acknowledgement messages between two servers. This paper depicts about the study of node failure and recovery, data replication and heartbeat messages.
Investigation of Effect of Process Parameters on Maximum Temperature during F...IJSRD
In case of friction stir welding, the maximum temperature along the weld line within appropriate range at tool workpiece interface is responsible for quality of welded joint. Through this paper, an attempt is made to establish a relationship between the input process parameters and the maximum temperature along the weld line during friction stir welding of aluminium alloy AA-7075. The design of pre-experimental simulation has been performed in accordance with full factorial technique. The simulation of friction stir welding has been performed by varying input parameters, tool rotational speed and welding speed. The analysis of variance (ANOVA) is used to investigate the effect of input parameters on maximum temperature during friction stir welding. A correlation was established between input parameters and maximum temperature by multiple regression lines. This study indicates that the tool rotational speed is the main input parameter that has high statistical influence on maximum temperature along the weld line during friction stir welding of aluminium alloy AA-7075.
Review Paper on Computer Aided Design & Analysis of Rotor Shaft of a RotavatorIJSRD
The intent of this paper is to study the various forces and stress acting on a rotor shaft of a standard rotavator which is subjected to transient loading. The standard models of rotavator, having a progressive cutting sequence was considered for the study and analysis. The study was extended to various available models having different cutting blade arrangement. The study was carried on different papers and identifies the various forces acting on a Rotor shaft of a rotavator. The positions of the torque and forces applied are varied according to the model considered. The response was obtained by considering the angle of twist and equivalent stress on the rotor shaft. This paper presented a methodology for conducting transient analysis of rotor shaft of a rotavator,
A Survey on Data Mining Techniques for Crime Hotspots PredictionIJSRD
A crime is an act which is against the laws of a country or region. The technique which is used to find areas on a map which have high crime intensity is known as crime hotspot prediction. The technique uses the crime data which includes the area with crime rate and predict the future location with high crime intensity. The motivation of crime hotspot prediction is to raise people’s awareness regarding the dangerous location in certain time period. It can help for police resource allocation for creating a safe environment. The paper presents survey of different types of data mining techniques for crime hotspots prediction.
Acetabularia Information For Class 9 .docxvaibhavrinwa19
Acetabularia acetabulum is a single-celled green alga that in its vegetative state is morphologically differentiated into a basal rhizoid and an axially elongated stalk, which bears whorls of branching hairs. The single diploid nucleus resides in the rhizoid.
Operation “Blue Star” is the only event in the history of Independent India where the state went into war with its own people. Even after about 40 years it is not clear if it was culmination of states anger over people of the region, a political game of power or start of dictatorial chapter in the democratic setup.
The people of Punjab felt alienated from main stream due to denial of their just demands during a long democratic struggle since independence. As it happen all over the word, it led to militant struggle with great loss of lives of military, police and civilian personnel. Killing of Indira Gandhi and massacre of innocent Sikhs in Delhi and other India cities was also associated with this movement.
Instructions for Submissions thorugh G- Classroom.pptxJheel Barad
This presentation provides a briefing on how to upload submissions and documents in Google Classroom. It was prepared as part of an orientation for new Sainik School in-service teacher trainees. As a training officer, my goal is to ensure that you are comfortable and proficient with this essential tool for managing assignments and fostering student engagement.
How to Make a Field invisible in Odoo 17Celine George
It is possible to hide or invisible some fields in odoo. Commonly using “invisible” attribute in the field definition to invisible the fields. This slide will show how to make a field invisible in odoo 17.
Read| The latest issue of The Challenger is here! We are thrilled to announce that our school paper has qualified for the NATIONAL SCHOOLS PRESS CONFERENCE (NSPC) 2024. Thank you for your unwavering support and trust. Dive into the stories that made us stand out!
Francesca Gottschalk - How can education support child empowerment.pptxEduSkills OECD
Francesca Gottschalk from the OECD’s Centre for Educational Research and Innovation presents at the Ask an Expert Webinar: How can education support child empowerment?
Digital Tools and AI for Teaching Learning and Research
Efficient Channel Assignment Schemes In 802.11 WLAN
1. IJSRD - International Journal for Scientific Research & Development| Vol. 3, Issue 10, 2015 | ISSN (online): 2321-0613
All rights reserved by www.ijsrd.com 73
Efficient Channel Assignment Schemes in 802.11 WLAN
Prof. Gundale A.S1
Ms. Akki P.M2
1,2
Department of Electronics Engineering
1,2
Walchand Institute of Technology, Sholapur, Maharashtra, India
Abstract— A wireless local area network (LAN) is a flexible
data communications system implemented as an extension
to, or as an alternative for, a wired LAN. Wireless Local
Area Networks (WLANs) are having tremendous growth &
becoming increasingly popular. The planning of wireless
local area network (WLAN) infrastructures that supply large
buildings or areas requires the consideration of many
aspects (coverage, different traffic densities, interference,
cost minimization, network throughput) and therefore is a
difficult task if done manually. The performance of WLAN
can be greatly improved by efficient channel assignment.
This paper presents a survey on efficient channel assignment
algorithms in WLAN’s. The survey is concluded with
various research issues open for further study.
Key words: WLANs, LCCS, PACA
I. INTRODUCTION
Communication has become very important for exchanging
information between people from and to anywhere at any
time. We have different types of networks for
communication. They are wired and wireless. Our
concentration is on wireless networks. The wireless local
area network or WLAN was originally intended to provide
local area network connections where premises wiring
systems were inadequate to support conventional wired
LAN. Due to use of the unlicensed frequency spectrum &
the inexpensive network equipment has encouraged the
deployment of WLANs. The increase in deployment of
access points (APs) has led researchers to develop channel
assignment algorithms in order to reduce co-channel and
adjacent channel interferences from neighbouring APs,
which causes an overall throughput degradation of the
network. As the number of WLANs is increasing the co-
channel interference is also increasing. Wireless Local Area
Networks (WLANs) are subjected to interference because of
their working in Unlicensed Spectrum. For smaller scenarios
with only a few access points (AP) to be installed, no
complex network planning is needed. However, network
solutions supplying larger areas like public hot-spots,
university campus, office buildings etc. need much more
sophisticated planning. Wireless Local Area Networks
(WLANs) are subjected to interference because of their
working in Unlicensed Spectrum. Channel management
strategies are methods of combining the transmission
characteristics of a wireless channel so as to achieve a
certain level of communication performance. Intelligent
channel management strategies will consider efficient
methods of exploiting the transmission characteristics; these
strategies will ensure that a group of access points (APs), are
assigned channels so as to maximize channel reuse and
minimize interference, i.e. to improve efficiency. Due to the
number of features available in 802.11n, there is a need to
develop a comprehensive channel management strategy that
can address each feature available in 802.11n wireless
technologies so as to maximize gains in channel capacity.
Channel allocation schemes can be divided in general into
Fixed Channel Allocation schemes, Dynamic Channel
Allocation schemes, and Hybrid Channel Allocation
schemes.
1) WLAN Can Configure In Two Basic Modes:
1) Peer-to Peer (Ad-hoc) mode: This mode consists of
two or more clients are equipped with wireless network
adapter with no connection to wired network.
2) Client/Server (infrastructure networking): This mode
offer fully distributed data connectivity. This mode
generally consists of multiple stations liked with
central hub.
2) IEEE 802.11 Channels:
There are two unlicensed frequency bands available for
802.11 WLANS
1) 2.4 GHz Industrial, Scientific, and Medical (ISM)
band, and
2) 5 GHz Unlicensed National Information Infrastructure
(UNII) band.
The 802.11a specification today specifies 4
channels for the UNII1 band, 4 channels for the UNII@
band, and 4 channels for the UNII3 band.
These channels are spaced at 20MHz apart and are
considered non- interfering, however they do have a slight
overlap in frequency spectrum. It is possible to use adjacent
channels in adjacent cell coverage, but it is recommended
when possible to separate adjacent cell channels by at least 1
channel. Fig 1 shows the channel scheme for the 802.11
bands.
Fig. 1: 802.11 Channel Allocations
A. Overlapping Channel Interference:
802.11b/g networks operate between 2.4 GHz and 2.5 GHz.
In 802.11b/g, transmissions between APs and demand
clusters do not use a single frequency. Instead, the
frequencies are divided into 14 channels, and use a
modulation technique, direct sequence spread spectrum, to
spread the transmission over multiple channels for effective
uses of the frequency spectrum. Channel 1 is assigned to
2.412 GHz. There is 5MHz separation between the channels.
Thus, channel 14 is assigned to 2.484 GHz. In the United
States, channels 1-11 are used. Europe uses channels 1-13.
Japan uses channels 1-14. An 802.11b/g signal occupies
approximately 30 MHz of the frequency spectrum. As a
result, an 802.11b/g signal overlaps with several adjacent
channel frequencies. Use of overlapping channels degrades
network throughput. Interference in 802.11b causes APs and
stations to send frames over and over again to increase the
2. Efficient Channel Assignment Schemes in 802.11 WLAN
(IJSRD/Vol. 3/Issue 10/2015/014)
All rights reserved by www.ijsrd.com 74
odds of successful transmission. Typically, if devices were
to send one copy of a frame, data is transmitted at 11 Mbps
(54 Mbps for 802.11g). However, if the efficiency were to
drop to 50%, for instance, because of interference, the
devices would still be transmitting at 11 Mbps, but it would
be duplicating each frame, making the effective throughput
5.5 Mbps. Therefore, 802.11 networks will have a
significant decrease in network performance because of
interference.
B. Overlapping Channel Interference Factor:
An overlapping channel interference factor, wij, to be the
relative percentage increase in interference as a result of two
APs i and j using overlapping channels. Thus overlapping
channels assigned to APs must be chosen carefully. The
overlapping channel interference factor is defined as:
{
⃓
Where Fi is the channel assigned to AP i. Fi
belongs to the set of available channels. c is the overlapping
channel factor. In 802.11b/g, c is 1/5 where 5 is the
maximum number of overlapping channels.
For instance, if channel 1 is assigned to AP i and
channel 1 is also assigned to AP j, the overlapping channel
interference factor between AP i and AP j, wij , is 1.0 or
100%. If channel 5 is assigned to AP j, wij is 0.2 or 20%. If
channels 6 or higher is assigned to AP j, wij is 0 or 0%,
which means there is no interference between AP i and AP j.
II. PROBLEM DEFINITION
The popularity of WLAN is increasing day by day. WLAN
takes help of access point to forward the message. The
increase in deployment of access points (APs) leads to co-
channel interference from neighbouring APs degrading the
network throughput on way to improve performance of
WLAN is to reduce co-channel interference the co-channel
interference can be reduced by efficient channel assignment
III. CHANNEL ASSIGNMENT SCHEMES
A. Least Congested Channel Search:
In LCCS [1] every AP finds channel with least number of
clients associated with it and switches to a channel with
least number of clients .For this every AP scans each
channel for beacons published by neighboring APs. Beacon
is a management frame in IEEE 802.11 based WLANs
containing information such as number of clients associated
with each AP, traffic information etc. Based on this an AP
comes to know the number of APs and the total number of
clients associated with each channel. Then it switches to
channel with least number of clients.
1) Limitations of LCCS:
It cannot detect interference in some situations. For example
as shown in Fig 2., AP1 and AP2 are not within
transmission ranges of each other but clients associated with
them interfere. This situation is called hidden interference
problem which is not detected by LCCS.
Fig. 2: Hidden Interference Problem
B. Dynamic Channel Assignment Algorithm
Channels should be assigned to each AP in such a way that
minimizes interference between APs. The closer the
overlapping frequencies, the higher the interference.
dynamic channel assignment problem using the following
variables is defined as follows:
Ai is the set of neighboring APs to AP i.
c is the overlapping channel factor.
dij is the distance between AP i and AP j.
Fi is the channel assigned to AP i.
Iij is the interference that AP j causes on AP i.
K is the total number of available channels. 802.11b/g
has 11 channels.
Loss is a function that captures the attenuation loss
based on the propagation model used.
m is a pathloss exponent
Pi is the transmit power of AP i.
Qi is the cardinality of Ai.
wij is the overlapping channel interference factor
between AP i and AP j
The dynamic channel assignment problem is given as:
Min ∑
subject to
=
{
⃓
For j ∈ Ai,
For Fi ∈ {1, ...,K}.
Each AP would periodically (or when the amount
of interference is above a threshold) run the above given
dynamic channel assignment problem. Each AP would in
turn pick its own channel that would minimize that amount
of interference it receives from its neighbors.
C. GDCA Algorithm
GDCA algorithm focuses on Channel Assignment (CA)
problem. This mechanism for channel assignment on multi-
radios, i.e., forming grid-loops via Minimum Spanning Tree
(MST) and forming group channel, which provides a novel
mechanism to the Multi-Radio Multi- Channel Wireless
Mesh Networks (MRMC-WMN) for assigning channels to
different loops and the related maintenance and renewing.
Channel Assignment in a MRMC-WMN environment
recognizes efficient channel utilization and minimizes
intervention but limited number of channels accessible to
the network [2].
3. Efficient Channel Assignment Schemes in 802.11 WLAN
(IJSRD/Vol. 3/Issue 10/2015/014)
All rights reserved by www.ijsrd.com 75
D. PACA (Peer Assisted Channel Assignment for Home
Wireless LANs):
PACA [3] is scalable as it is completely distributed. Each
AP collects the local information from its peers to do
channel assignment. PACA is an algorithm which helps AP
continuously gathers channels information and switches [9]
channel when a better channel is needed. When a client in
network becomes idle, i.e., it has no communication with the
AP, it enters a process called channel utilization query
process, which is shown in Algorithm. When the client
enters the process, it randomly selects a channel (including
its current operating channel) and switches to that channel to
gather the channel utilization information.
E. Channel Hopping Approach
In [4], a distributed channel assignment algorithm based on
the concept of channel hopping is specifically proposed for
an uncoordinated WLAN. In particular, each AP is assigned
a unique sequence of channels, and hops through this
sequence over time so as to average out the throughputs of
all APs in a long run. Each AP is within the transmission
ranges of three other APs. Each AP hops to the next channel
at the end of each time slot. Suppose that only three non-
overlapping channels, namely,1, 6 and 11, are available for
assignment, and that each AP always has data to transmit.
The goal is to average out the throughputs of all APs in a
long run.
F. Measurement Based Algorithms
The three proposed algorithms on Measurement based all
have an iterative nature and weighted interference is a
metric is used to capture the overall interference in the cell..
At each point in time (predefined, randomly chosen, or
determined at runtime), say every 1, 2, or 5 minutes, one
iteration of channel switching takes place where one or more
APs switch their frequency channels according to
mechanisms that are specific to the proposed algorithms,
while other APs stay on their current channels. The channel
switching time in hardware is several milliseconds and is
thus negligible as compared to the interval between two
iterations. APs and clients measure and average their in-situ
interference between very two successive iterations.
Iterations keep taking place on different AP(s) until the
channel allocations converge. Below we describe the
different conditions of the three algorithms that a
representative AP am can switch from channel k = fm to k’
= f’m . The denotes a vector of channels selected by APs
after the representative AP am moves from channel fm to
f’m .
1) The No-Coord Algorithm:
If am switches from its current channel fm to f’m only if the
weighted interference on the new channel f’m is lower, i.e.,
the following condition holds:
No-Coord Condition:
) >
This algorithm is denoted No-Coord, because am
makes a greedy channel selection without coordination with
other APs.
2) The Local-Coord Algorithm:
This algorithm is denoted Local-Coord, since am needs to
locally coordinate with the APs indexed by Gm;k(f) and
Gm;k’ (f) via wired backbone network for the channel
switching.
3) The Global-Coord Algorithms
In this algorithm, AP will switch to a new channel only if
the sum interference on the new channel is lower (after am
switches there) than the sum interference on its current
channel, i.e. the following condition holds.
Global-Coord Condition:
∑ ∑
This algorithm requires global coordination among
APs using a central network controller that communicate
with all APs, and is thus denoted Global-Coord.
G. ILP Approach
In [9], the problems of channel assignment and AP
placement are solved. Instantaneously by using Integer
Linear Programming (ILP).The methodology considers not
only radio coverage but also load balancing between APs
because the authors argue that the number of active wireless
clients connected to the Aps affects network performance.
That is, traffic congestion at the APs degrades the network
performance such as throughput. The basic idea is therefore
to distribute clients to the Aps in a WLAN such that
congestion at APs is minimized. Correspondingly, the
throughput is maximized. A floor plan is assumed to consist
of traffic demand points, each of which is given an expected
traffic demand volume. A set of AP candidate locations is
also given. If a signal from the AP to the demand point is
above a certain threshold, an edge is drawn between a traffic
demand point and a particular AP. Similarly, an edge is
drawn between two APs, whenever they are within a co-
channel interference distance defined as a transmission
range at which, if assigned the same channel, these two APs
can interfere to some extent with one another. The objective
is to minimize the maximum channel utilization at each AP,
while keeping a certain level of traffic demand satisfied at
each demand point. Each demand point is assigned to
exactly one AP. If at least one demand point is assigned to
an AP that AP will be included in the solution set. If an edge
exists between two APs, each AP will be assigned a
different non-overlapping channel. As mentioned earlier, the
goal is to distribute clients throughout the network such that
the overall network throughput tis maximized. This requires
an accurate network layout containing the descriptions of
demand points with estimated traffic, client distribution, and
received signal levels at each demand location. In general,
since such a network layout is very dynamic, new
assignment of demand points to APs and Channels to APs
are necessary.
H. Channel Assignment Algorithms
In IEEE 802.11 b/g WLAN, there exists 14 Channels. Only
11 channels are used in the US. Each channel spreads over
22 MHz due to the Direct Sequence Spread Spectrum
(DSSS) technique employed by IEEE 802.11b/g. The
overlapping channel interference factor wjk is defined as
follows:
4. Efficient Channel Assignment Schemes in 802.11 WLAN
(IJSRD/Vol. 3/Issue 10/2015/014)
All rights reserved by www.ijsrd.com 76
where Chj is the channel assigned to APj, Chk is
the channel assigned to APk and c is the no overlapping
portion of two adjacent channels, expressed as a fraction of
the frequency spectrum of a channel.
1) Channel Assignment Algorithm 1
The mathematical formulation of the first channel
assignment algorithm, based on minimizing interference
between APs, is given by the following
NLIP formulation:
Min
For all j
Subject to
For k ∈ Aj ,
For j ∈{1, …, M} ,
For Chj, Chk ∈{1, …, K}.
This algorithm minimizes the total interference at each AP.
2) Channel Assignment Algorithm 2
The mathematical-programming formulation of the second
channel assignment algorithm, based on maximizing the SIR
for the users, is given below as
subject to wjk= max (0, 1– |Chj – Chk| × c)
For j, k ∈{1,...,M},
For i ∈ {1,...,N},
For Chj, Chk ∈ {1,...,K}.
The total SIR refers to the sum of all SIR values at
the individual users in the network. This algorithm is used to
maximize the SIR’s for the users.
IV. CLASSIFICATION OF VARIOUS CHANNEL ASSIGNMENT
TECHNIQUES IN IEEE 802.11
For channel assignment various aspects are considered:
1) How often channel assignment is triggered (static or
adaptive),
2) To which type of deployment a channel assignment is
applicable (uncoordinated or centrally managed),
3) The type of frequency channels used (overlapping or
non- overlapping channels),
4) The procedure in obtaining channel assignment
solutions (heuristic or integer linear programming).
The main challenge would be how to capture the
network dynamics as much as possible while maintaining
the complexity of implementation of channel assignment
algorithm at a practical level. Furthermore, when WLANs
are deployed in an uncoordinated fashion by different
network administrators, the scalability of the
implementation of channel assignment algorithms becomes
even more important issue. In such scenarios, a channel
assignment scheme of choice should be cooperative and
Scalable enough to orchestrate channel switching across the
entire network without creating significant interference to
the neighbors. Being aware of the neighboring networks
located in different administrative domains, the scheme
should also be able to interact and exchange necessary
information with its neighbors in order to allocate
appropriate channels to the APs.
V. CONCLUSION
Channel assignment is one mechanism to improve the
performance of WLANs. In this survey we have discussed
several existing channel assignment schemes applicable to
either centrally managed or uncoordinated environments.
This paper mainly provides an overview of the various
channel assignment strategies used for WLANs. A lot of
work is being carried out in this area. Adaptive techniques
which consider network dynamics are considered. Ways of
continually monitoring network dynamics are being worked
on. Channel assignment can then be performed at a
particular location during a particular period of time based
on the prediction as well as the application requirements.
REFERENCES
[1] M. Achanta, “Method and Apparatus for Least
congested Channel Scan for Wireless Access Points,”
US Patent No. 20060072602, Apr. 2006.
[2] Yan Xia, Yingzhi Zeng, Zhenghu Gong, “A
Distributed Channel Assignment Mechanism for
Multi-radio Multi-Channel Wireless Mesh Networks”
JOURNAOF NETWORKS, VOL. 6, NO. 2,
FEBRUARY 2011.
[3] C.Wong S.-H. Gary Chan Jiancong Chen “PACA:
Peer-Assisted Channel Assignment for Home Wireless
LANs” Department of Computer Science The Hong
Kong University of Science and Technology Clear
Water Bay, Kowloon, Hong Kong, 2006
[4] A.Mishra and V. Shrivastava, D. Agrawal, S. Banerjee,
and S. Ganguly, “Distributed Channel Management in
Uncoordinated Wireless Environments inProc.
International Conference on Mobile Computing and
Networking, pp. 170–181, 2006.
[5] Lee, Y., Kim, K., Choi, Y. (2002). Optimization of AP
placement and Channel Assignment in Wireless LANs.
LCN 2002. 27th Annual IEEE Conference on Local
Computer Networks, pp. 831-836.
[6] Y. Lee, K. Kim, and Y. Choi, “Optimization of AP
Placement and Channel Assignment in Wireless
LANs,” in Proc. 27th Annual IEEE Conf. Local
Computer Networks, pp. 831–836, Nov. 2002
[7] Eisenblätter, A., Geerdes, H. F., & Siomina, I. (2007).
Integrated Access Point Placement and Channel
Assignment for Wireless LANs in an Indoor Office
Environment. 8th IEEE Intl. Symposium on a World of
Wireless, Mobile and Multimedia Networks
5. Efficient Channel Assignment Schemes in 802.11 WLAN
(IJSRD/Vol. 3/Issue 10/2015/014)
All rights reserved by www.ijsrd.com 77
[8] J. K. Chen, G. D. Veciana, and T. S. Rappaport,
“Improved Measurement-based Frequency Allocation
Algorithms for Wireless Networks,” in Proc. IEEE
GLOBECOM’07, Washington, DC, USA, Nov. 2007.
[9] P. Wertz, M. Sauter, F. Landstorfer, G.Wolfle, and R.
Hoppe, “Automatic Optimization Algorithms for the
Planning of Wireless Local AreaNetworks,” in Proc.
IEEE Vehicular Technology Conference, vol. 4, pp.
3010–3014, Sep. 2004.
[10]J. Park, S. Park, P. Cho, and K. Cho, “Analysis of
spectrum channel assignment for IEEE 802.11b
wireless lan,” The 5th International Symposium on
Wireless Personal Multimedia Communications, vol. 3,
pp. 1073–1077, October 2002.
[11]I. Papanikos, M. Logothetis, "A Study on Dynamic
Load Balance for IEEE 802.11b Wireless LAN," Proc.
8th International Conference on Advances in
Communication & Control, COMCON 8, Rethymna,
Crete, Greece, June 2001.