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.
3GPP has introduced LTE Femtocells to manipulate the traffic for indoor users and to minimize
the charge on the Macro cells. A key mechanism in the LTE traffic handling is the packet
scheduler which is in charge of allocating resources to active flows in both the frequency and
time dimension. So several scheduling algorithms need to be analyzed for femtocells networks.
In this paper we introduce a performance analysis of three distinct scheduling algorithms of
mixed type of traffic flows in LTE femtocells networks. The particularly study is evaluated in
terms of throughput, packet loss ratio, fairness index and spectral efficiency.
Long-Term Evolution (LTE), an emerging and promising fourth generation mobile technology, is expected
to offer ubiquitous broadband access to the mobile subscribers. In this paper, the performance of Frame
Level Scheduler (FLS), Exponential (EXP) rule, Logarithmic (LOG) rule and Maximum-Largest Weighted
Delay First (M-LWDF) packet scheduling algorithms has been studied in the downlink 3GPP LTE cellular
network. To this aim, a single cell with interference scenario has been considered. The performance
evaluation is made by varying the number of UEs ranging from 10 to 50 (Case 1) and user speed in the
range of [3, 120] km/h (Case 2). Results show that while the number of UEs and user speed increases, the
performance of the considered scheduling schemes degrades and in both case FLS outperforms other three
schemes in terms of several performance indexes such as average throughput, packet loss ratio (PLR),
packet delay and fairness index.
Abstract— Scheduler is the backbone of intelligence in a LTE network. Scheduler will often have clashing needs that can make its design very complex and non-trivial.
The overall system throughput needs to be maintained at the best possible value without sacrificing the cell edge user experience.
In this paper, authors compared different scheduler designs for voice and packet services. They explained the role of configuration parameters through simulations. These parameters control the tradeoff between the sector throughput and the fairness in system through. They explained a possible scheduler implementation.
ADAPTIVE HANDOVER HYSTERESIS AND CALL ADMISSION CONTROL FOR MOBILE RELAY NODESIJCNCJournal
The aim of equipping a wireless network with a mobile relay node is to support broadband wireless communications for vehicular users and their devices. The high mobility of vehicular users, possibly at a very high velocity in the area in which two cells overlap, could cause the network to suffer from a reduced handover success rate and, hence, increased radio link failure. The combined impact of these problems is service interruptions to vehicular users. Thus, the handover schemes are crucial in solving these problems. In this work, we first present the adaptive handover hysteresis scheme for the wireless network with mobile relay nodes in the high-speed train scenario. Specifically, our proposed adaptive hysteresis scheme is based on the velocity of the train. Second, the handover call dropping probability is reduced by introducing a modified call admission control scheme to support radio resource reservation for handover calls that prioritizes handover calls of mobile relay over the other calls. The proposed solution in which adaptive parameter is combined with call admission control is evaluated by system level simulation. Our simulation results illustrate an increased handover success rate and reduced radio link failures.
REALIZATION OF TRANSMITTER AND RECEIVER ARCHITECTURE FOR DOWNLINK CHANNELS IN...VLSICS Design
Long Term Evolution (LTE), the next generation of radio technologies designed to increase the capacity and speed of mobile networks. The future communication systems require much higher peak rate for the air interface but very short processing delay. This paper mainly focuses on to improve the processing speed and capability and decrease the processing delay of the downlink channels using the parallel processing technique. This paper proposes Parallel Processing Architecture for both transmitter and receiver for Downlink channels in 3GPP-LTE. The Processing steps include Scrambling, Modulation, Layer mapping, Precoding and Mapping to the REs in transmitter side. Similarly demapping from the REs, Decoding and Detection, Delayer mapping and Descrambling in Receiver side. Simulation is performed by using modelsim and Implementation is achieved using Plan Ahead tool and virtex 5 FPGA.Implemented results are discussed in terms of RTL design, FPGA editor, power estimation and resource estimation.
Some of the key driving forces behind the transition from the UMTS based cellular system to the Long Term Evolution Advanced (LTE-A) are to improve the mean and the cell-edge throughput, improve the user fairness, and improve the quality of service (QoS) satisfaction for all users. In the latter system, relays appear as one of the most prominent enabler for improving the cell-edge user experience while increasing the system’s fairness.
In this white paper, we present the basics of relay deployments in LTE-A networks. Moreover, we analyze resource allocation problem for Relay Nodes (RN) deployments and present some of the solutions for improvement in system resource usage and QoS satisfaction. Afterwards, we introduce the capabilities of NOMOR’s LTE-A system level simulator and evaluate the performance of LTE-A relay systems under the described solutions.
3GPP has introduced LTE Femtocells to manipulate the traffic for indoor users and to minimize
the charge on the Macro cells. A key mechanism in the LTE traffic handling is the packet
scheduler which is in charge of allocating resources to active flows in both the frequency and
time dimension. So several scheduling algorithms need to be analyzed for femtocells networks.
In this paper we introduce a performance analysis of three distinct scheduling algorithms of
mixed type of traffic flows in LTE femtocells networks. The particularly study is evaluated in
terms of throughput, packet loss ratio, fairness index and spectral efficiency.
Long-Term Evolution (LTE), an emerging and promising fourth generation mobile technology, is expected
to offer ubiquitous broadband access to the mobile subscribers. In this paper, the performance of Frame
Level Scheduler (FLS), Exponential (EXP) rule, Logarithmic (LOG) rule and Maximum-Largest Weighted
Delay First (M-LWDF) packet scheduling algorithms has been studied in the downlink 3GPP LTE cellular
network. To this aim, a single cell with interference scenario has been considered. The performance
evaluation is made by varying the number of UEs ranging from 10 to 50 (Case 1) and user speed in the
range of [3, 120] km/h (Case 2). Results show that while the number of UEs and user speed increases, the
performance of the considered scheduling schemes degrades and in both case FLS outperforms other three
schemes in terms of several performance indexes such as average throughput, packet loss ratio (PLR),
packet delay and fairness index.
Abstract— Scheduler is the backbone of intelligence in a LTE network. Scheduler will often have clashing needs that can make its design very complex and non-trivial.
The overall system throughput needs to be maintained at the best possible value without sacrificing the cell edge user experience.
In this paper, authors compared different scheduler designs for voice and packet services. They explained the role of configuration parameters through simulations. These parameters control the tradeoff between the sector throughput and the fairness in system through. They explained a possible scheduler implementation.
ADAPTIVE HANDOVER HYSTERESIS AND CALL ADMISSION CONTROL FOR MOBILE RELAY NODESIJCNCJournal
The aim of equipping a wireless network with a mobile relay node is to support broadband wireless communications for vehicular users and their devices. The high mobility of vehicular users, possibly at a very high velocity in the area in which two cells overlap, could cause the network to suffer from a reduced handover success rate and, hence, increased radio link failure. The combined impact of these problems is service interruptions to vehicular users. Thus, the handover schemes are crucial in solving these problems. In this work, we first present the adaptive handover hysteresis scheme for the wireless network with mobile relay nodes in the high-speed train scenario. Specifically, our proposed adaptive hysteresis scheme is based on the velocity of the train. Second, the handover call dropping probability is reduced by introducing a modified call admission control scheme to support radio resource reservation for handover calls that prioritizes handover calls of mobile relay over the other calls. The proposed solution in which adaptive parameter is combined with call admission control is evaluated by system level simulation. Our simulation results illustrate an increased handover success rate and reduced radio link failures.
REALIZATION OF TRANSMITTER AND RECEIVER ARCHITECTURE FOR DOWNLINK CHANNELS IN...VLSICS Design
Long Term Evolution (LTE), the next generation of radio technologies designed to increase the capacity and speed of mobile networks. The future communication systems require much higher peak rate for the air interface but very short processing delay. This paper mainly focuses on to improve the processing speed and capability and decrease the processing delay of the downlink channels using the parallel processing technique. This paper proposes Parallel Processing Architecture for both transmitter and receiver for Downlink channels in 3GPP-LTE. The Processing steps include Scrambling, Modulation, Layer mapping, Precoding and Mapping to the REs in transmitter side. Similarly demapping from the REs, Decoding and Detection, Delayer mapping and Descrambling in Receiver side. Simulation is performed by using modelsim and Implementation is achieved using Plan Ahead tool and virtex 5 FPGA.Implemented results are discussed in terms of RTL design, FPGA editor, power estimation and resource estimation.
Some of the key driving forces behind the transition from the UMTS based cellular system to the Long Term Evolution Advanced (LTE-A) are to improve the mean and the cell-edge throughput, improve the user fairness, and improve the quality of service (QoS) satisfaction for all users. In the latter system, relays appear as one of the most prominent enabler for improving the cell-edge user experience while increasing the system’s fairness.
In this white paper, we present the basics of relay deployments in LTE-A networks. Moreover, we analyze resource allocation problem for Relay Nodes (RN) deployments and present some of the solutions for improvement in system resource usage and QoS satisfaction. Afterwards, we introduce the capabilities of NOMOR’s LTE-A system level simulator and evaluate the performance of LTE-A relay systems under the described solutions.
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.
Multi-layer heterogeneous network layout including small cell base stations are considered to be the key to further enhancements of the spectral efficiency achieved in mobile communication networks. It has been recognized that inter-cell interference has become the limiting factor when trying to achieve not only high average user satisfaction, but a high degree of satisfaction for as many users as possible. Therefore, inter-cell interference coordination (ICIC) lies in the focus of researchers defining next generation mobile communication standards, such as LTE-A.
Building upon [1], this paper provides an overview over the background calling for ICIC in heterogeneous LTE-A networks. It outlines techniques standardized in Rel. 10 of LTE-A, discusses them showing their benefits and limitations by means of system-level simulations and motivates the importance of self optimizing network (SON) procedures for ICIC in LTE-A.
Rm literature survey_on_scheduling_and_resource_allocation_for_ieee_80211ax_p...RESHAN FARAZ
IEEE 8021.11 is the standard defined for WLAN(Wireless Local Area Network). It first
came into the picture in 1997 which offer a speed of 2Mbit/s. After that we have different
versions, 802.11b having speed 11Mbit/s, 802.11a/g having 54 Mbit/s, 802.11n having 600
Mbit/s, and even above Gbit/s rates in the latest 802.11ac. These speeds can be achieved
by means of different modulation and coding scheme, wider channel and adaptation of
Multiple Input Multiple Output (MIMO) technologies[7]. The 802.11ax will provide outstanding average throughput in the dense environment. Many clients connect with the
Access Point (AP) simultaneously using the Orthogonal frequency-division multiple access
(OFDMA) where AP divides the entire frequency band into multiple subsets of orthogonal
sub carrier called as Resource Unit (RU),These RUs are assigned to different user to transit
in parallel which make 802.11ax different from all other versions of 802.11 so we need some
scheduling and resource allocation mechanism to utilize the features of 802.11ax. Before
going to scheduling and resource allocation, let us discuss some features of 802.11ax
Heterogeneous LTE Networks and Inter-Cell Interference Coordination - Dec 201...Eiko Seidel
Initial deployments of LTE networks are based on so-called homogeneous networks consisting of base stations providing basic coverage, called macro base stations. The concept of heterogeneous networks has recently attracted considerable attention to optimize performance particularly for unequal user or traffic distribution. Here, the layer of planned high-power macro eNBs is overlaid with layers of lower-power pico or femto eNBs that are deployed in a less well planed or even entirely uncoordinated manner. Such deployments can achieve significantly improved overall capacity and cell-edge performance and are often seen as the second phase in LTE network deployment.
This paper discusses the concept of heterogeneous networks as compared to homogeneous networks. It demonstrates the need for inter-cell interference coordination (ICIC) and outlines some ICIC methods that are feasible with release 8 /9 of the LTE standard. System-level simulation results illustrate the benefits of the various features discussed in the following.
Evaluation of 5G Data Duplication for URLLC - Nomor Reseach GmbHEiko Seidel
As you might know Data Duplication can be used in combination of Carrier Aggregation or Dual Connectivity to increase reliability for services such as URLLC. Enclosed a paper of my colleague Dr. Volker Pauli with 5G system/protocol level simulation results for different scenarios for a CU/DU split architecture. Packet loss rates of 10-5 are feasible for URLLC within restricted service areas.
A DDRESSING T HE M ULTICHANNEL S ELECTION , S CHEDULING A ND C OORDINATION...pijans
We discuss a new multichannel coordination and sche
duling challenge called the Multichannel Scheduling
Cost (MSC). It is caused by the inability of the co
ntrol channel to schedule simultaneous transmission
s
resulting in data channels lying idle and their ban
dwidth underutilized. As a result, wasted bandwidth
increases as the number of data channels increases.
To address this challenge, a cyclic scheduling
Algorithm (CSA) is proposed. It employs one dedicat
ed signaling channel and 4 data channels. It is
premised on a proactive channel reservation scheme
which reduces the idleness of channels. The scheme
ensures that data channels are reserved while they
are still busy. The data channels are reserved whil
e
their remaining transmission duration is equal to t
he virtual carrier sensing duration. This gives the
next
pair sufficient time to reserve the current data ch
annel before it becomes available, limiting the MSC
to the
first cycle. The simulation results show a performa
nce benefit of the CSA scheme in addressing the eff
ects
of the MSC
Energy Efficient LEACH protocol for Wireless Sensor Network (I-LEACH)ijsrd.com
in the wireless sensor networks (WSNs), the sensor nodes (called motes) are usually scattered in a sensor field an area in which the sensor nodes are deployed. These motes are small in size and have limited processing power, memory and battery life. In WSNs, conservation of energy, which is directly related to network life time, is considered relatively more important souse of energy efficient routing algorithms is one of the ways to reduce the energy conservation. In general, routing algorithms in WSNs can be divided into flat, hierarchical and location based routing. There are two reasons behind the hierarchical routing Low Energy Adaptive Clustering Hierarchy (LEACH) protocol be in explored. One, the sensor networks are dense and a lot of redundancy is involved in communication. Second, in order to increase the scalability of the sensor network keeping in mind the security aspects of communication. Cluster based routing holds great promise for many to one and one to many communication paradigms that are pre valentines or networks.
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.
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 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.
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.
Multi-layer heterogeneous network layout including small cell base stations are considered to be the key to further enhancements of the spectral efficiency achieved in mobile communication networks. It has been recognized that inter-cell interference has become the limiting factor when trying to achieve not only high average user satisfaction, but a high degree of satisfaction for as many users as possible. Therefore, inter-cell interference coordination (ICIC) lies in the focus of researchers defining next generation mobile communication standards, such as LTE-A.
Building upon [1], this paper provides an overview over the background calling for ICIC in heterogeneous LTE-A networks. It outlines techniques standardized in Rel. 10 of LTE-A, discusses them showing their benefits and limitations by means of system-level simulations and motivates the importance of self optimizing network (SON) procedures for ICIC in LTE-A.
Rm literature survey_on_scheduling_and_resource_allocation_for_ieee_80211ax_p...RESHAN FARAZ
IEEE 8021.11 is the standard defined for WLAN(Wireless Local Area Network). It first
came into the picture in 1997 which offer a speed of 2Mbit/s. After that we have different
versions, 802.11b having speed 11Mbit/s, 802.11a/g having 54 Mbit/s, 802.11n having 600
Mbit/s, and even above Gbit/s rates in the latest 802.11ac. These speeds can be achieved
by means of different modulation and coding scheme, wider channel and adaptation of
Multiple Input Multiple Output (MIMO) technologies[7]. The 802.11ax will provide outstanding average throughput in the dense environment. Many clients connect with the
Access Point (AP) simultaneously using the Orthogonal frequency-division multiple access
(OFDMA) where AP divides the entire frequency band into multiple subsets of orthogonal
sub carrier called as Resource Unit (RU),These RUs are assigned to different user to transit
in parallel which make 802.11ax different from all other versions of 802.11 so we need some
scheduling and resource allocation mechanism to utilize the features of 802.11ax. Before
going to scheduling and resource allocation, let us discuss some features of 802.11ax
Heterogeneous LTE Networks and Inter-Cell Interference Coordination - Dec 201...Eiko Seidel
Initial deployments of LTE networks are based on so-called homogeneous networks consisting of base stations providing basic coverage, called macro base stations. The concept of heterogeneous networks has recently attracted considerable attention to optimize performance particularly for unequal user or traffic distribution. Here, the layer of planned high-power macro eNBs is overlaid with layers of lower-power pico or femto eNBs that are deployed in a less well planed or even entirely uncoordinated manner. Such deployments can achieve significantly improved overall capacity and cell-edge performance and are often seen as the second phase in LTE network deployment.
This paper discusses the concept of heterogeneous networks as compared to homogeneous networks. It demonstrates the need for inter-cell interference coordination (ICIC) and outlines some ICIC methods that are feasible with release 8 /9 of the LTE standard. System-level simulation results illustrate the benefits of the various features discussed in the following.
Evaluation of 5G Data Duplication for URLLC - Nomor Reseach GmbHEiko Seidel
As you might know Data Duplication can be used in combination of Carrier Aggregation or Dual Connectivity to increase reliability for services such as URLLC. Enclosed a paper of my colleague Dr. Volker Pauli with 5G system/protocol level simulation results for different scenarios for a CU/DU split architecture. Packet loss rates of 10-5 are feasible for URLLC within restricted service areas.
A DDRESSING T HE M ULTICHANNEL S ELECTION , S CHEDULING A ND C OORDINATION...pijans
We discuss a new multichannel coordination and sche
duling challenge called the Multichannel Scheduling
Cost (MSC). It is caused by the inability of the co
ntrol channel to schedule simultaneous transmission
s
resulting in data channels lying idle and their ban
dwidth underutilized. As a result, wasted bandwidth
increases as the number of data channels increases.
To address this challenge, a cyclic scheduling
Algorithm (CSA) is proposed. It employs one dedicat
ed signaling channel and 4 data channels. It is
premised on a proactive channel reservation scheme
which reduces the idleness of channels. The scheme
ensures that data channels are reserved while they
are still busy. The data channels are reserved whil
e
their remaining transmission duration is equal to t
he virtual carrier sensing duration. This gives the
next
pair sufficient time to reserve the current data ch
annel before it becomes available, limiting the MSC
to the
first cycle. The simulation results show a performa
nce benefit of the CSA scheme in addressing the eff
ects
of the MSC
Energy Efficient LEACH protocol for Wireless Sensor Network (I-LEACH)ijsrd.com
in the wireless sensor networks (WSNs), the sensor nodes (called motes) are usually scattered in a sensor field an area in which the sensor nodes are deployed. These motes are small in size and have limited processing power, memory and battery life. In WSNs, conservation of energy, which is directly related to network life time, is considered relatively more important souse of energy efficient routing algorithms is one of the ways to reduce the energy conservation. In general, routing algorithms in WSNs can be divided into flat, hierarchical and location based routing. There are two reasons behind the hierarchical routing Low Energy Adaptive Clustering Hierarchy (LEACH) protocol be in explored. One, the sensor networks are dense and a lot of redundancy is involved in communication. Second, in order to increase the scalability of the sensor network keeping in mind the security aspects of communication. Cluster based routing holds great promise for many to one and one to many communication paradigms that are pre valentines or networks.
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.
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 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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
An efficient model for reducing soft blocking probability in wireless cellula...ijwmn
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.
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
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.
Macro with pico cells (hetnets) system behaviour using well known scheduling ...ijwmn
This paper demonstrates the concept of using Heterogeneous networks (HetNets) to improve Long Term Evolution (LTE) system by introducing the LTE Advance (LTE-A). The type of HetNets that has been chosen for this study is Macro with Pico cells. Comparing the system performance with and without Pico cells has clearly illustrated using three well-known scheduling algorithms (Proportional Fair PF, Maximum Largest Weighted Delay First MLWDF and Exponential/Proportional Fair EXP/PF). The system is judged based on throughput, Packet Loss Ratio PLR, delay and fairness.. A simulation platform called LTE-Sim has been used to collect the data and produce the paper’s outcomes and graphs. The results prove that adding Pico cells enhances the overall system performance. From the simulation outcomes, the overall system performance is as follows: throughput is duplicated or tripled based on the number of users, the PLR is almost quartered, the delay is nearly reduced ten times (PF case) and changed to be a half (MLWDF/EXP cases), and the fairness stays closer to value of 1. It is considered an efficient and cost effective way to increase the throughput, coverage and reduce the latency.
B ENCHMARKING OF C ELL T HROUGHPUT U SING P ROPORTIONAL F AIR S CHEDULE...ijwmn
The proportional fair (PF) scheduling algorithm com
promises between cell throughput and fairness. Many
research findings have been published by various re
searchers about PF algorithm based on mathematical
model and simulations. In this paper we have taken
the practical route to analyse the algorithm based
on
three types of subscription. In this benchmarking s
tudy, the user subscriptions are differentiated as
Gold,
Silver and Bronze schemes and they are provisioned
with certain throughputs. Apart from subscriptions
plans, the channel condition also plays a major rol
e in determining the throughput. So in order to ens
ure
fairness among different subscriptions even in the
bad channel conditions and to deliver the provision
ed
throughputs certain priorities are attached with th
e subscriptions. As per the subscription plans Gold
subscribers are assigned with 50% of the speed offe
red by the network as maximum based on CAT3 speed
(100 Mbps in DL and 50 Mbps in UL), Silver is assig
ned with 25% of the max speed and Bronze is
assigned with 12% of the max speed. The priorities
assigned to subscribers determines the fairness in
the
unfavourable channel conditions - Bronze (high), Si
lver and Gold (medium). In this paper, an
benchmarking tests have been performed with all of
three types of subscribers for nearly two hours in
the
live single cell network without any heterogeneous
cells influencing it. Furthermore, the results are
compared with the simulation results.
PERFORMANCE ANALYSIS OF RESOURCE SCHEDULING IN LTE FEMTOCELLS NETWORKScscpconf
3GPP has introduced LTE Femtocells to manipulate the traffic for indoor users and to minimize the charge on the Macro cells. A key mechanism in the LTE traffic handling is the packet
scheduler which is in charge of allocating resources to active flows in both the frequency and time dimension. So several scheduling algorithms need to be analyzed for femtocells networks. In this paper we introduce a performance analysis of three distinct scheduling algorithms of mixed type of traffic flows in LTE femtocells networks. The particularly study is evaluated in terms of throughput, packet loss ratio, fairness index and spectral efficiency.
QOS-B ASED P ERFORMANCE E VALUATION OF C HANNEL -A WARE /QOS-A WARE S CHEDULI...csandit
Long Term Evolution (LTE) is defined by the Third G
eneration Partnership Project (3GPP)
standards as Release 8/9. The LTE supports at max 2
0 MHz channel bandwidth for a carrier.
The number of LTE users and their applications are
increasing, which increases the demand on
the system BW. A new feature of the LTE-Advanced (L
TE-A) which is defined in the 3GPP
standards as Release 10/11 is called Carrier Aggreg
ation (CA), this feature allows the network
to aggregate more carriers in-order to provide a hi
gher bandwidth. Carrier Aggregation has
three main cases: Intra-band contiguous, Intra-band
non-contiguous, Inter-band contiguous.
The main contribution of this paper was in implemen
ting the Intra-band contiguous case by
modifying the LTE-Sim-5, then evaluating the Qualit
y of Service (QoS) performance of the
Modified Largest Weighted Delay First (MLWDF), the
Exponential Rule (Exp-Rule), and the
Logarithmic Rule (Log-Rule) scheduling algorithms
Implementation of Pipelined Architecture for Physical Downlink Channels of 3G...josephjonse
LTE (Long Term Evolution) is a high data rate, low latency and packet optimized radio access technology designed to support roaming Internet access via cell phones and handheld devices in 3G and 4G networks. This paper mainly focuses on to improve the processing speed and decrease the maximum delay of the downlink channels using the pipelined buffer controlled technique. This paper proposes Pipelined buffer controlled Architecture for both transmitter and receiver for Physical Downlink channels of 3GPP-LTE. The transmitter architecture comprises Bit Scrambling, Modulation mapping, Layer mapping, Precoding and Resource element mapping modules. The receiver architecture comprises Demapping from resource elements, Decoding, Comparing and Detection, Delayer mapping and Descrambling modules as described in LTE specifications. In addition to these, buffers are included in both transmitter and receiver architectures. Modelsim is used for simulation, synthesis and implementation are achieved using PlanAhead13.2 tool on Virtex-5, xc5vlx50tff1136-1 device board is used. Implemented results are discussed in terms of RTL design, FPGA editor, Power estimation and Resource estimation.
Survey on scheduling and radio resources allocation in lteijngnjournal
This paper focuses on an essential task of the enhanced NodeB eNodeB element in LTE architecture, the
Radio Resource Manager RRM, which aims to accept or reject requests for connection to the network
based on some constraints and ensuring optimal distribution of radio resources between Users Equipments
UEs. Its main functionalities include Admission Control AC and Packet Scheduling PS.
This paper will center mainly on the PS part of the RRM task, which performs the radio resource
allocation in both uplink and downlink directions. Several approaches and algorithms have been proposed
in the literature to address this need (allocate resources efficiently), the diversity and multitude of
algorithms is related to the factors considered for the optimal management of radio resource, specifically,
the traffic type and the QoS (Quality of Service) requested by the UE.
In this article, an art’s state of the radio resource allocation strategies and a detailed study of several
scheduling algorithms proposed for LTE (uplink and downlink) are made. Therefore, we offer our
evaluation and criticism.
Exponential MLWDF (EXP-MLWDF) Downlink Scheduling Algorithm Evaluated in LTE ...IJECEIAES
Nowadays, with the advent of smartphones, most of people started to make voice and video conference calls continuously even in a high mobility scenario, the bandwidth requirements have increased considerably, which can cause network congestion phenomena. To avoid network congestion problems and to support high mobility scenario, 3GPP has developed a new cellular standard based packet switching, termed LTE (Long Term Evolution). The purpose of this paper is to evaluate the performance of the new proposed algorithm, named Exponential Modified Largest Weighted Delay First „EXP-MLWDF‟, for high mobility scenario and with the presence of a large number of active users, in comparison with the wellknown algorithms such as a proportional fair algorithm (PF), Exponential Proportional Fairness (EXP/PF), Logarithm Rule (LOG-Rule), Exponential Rule (EXP-Rule) and Modified Largest Weighted Delay First (MLWDF). The performance evaluation is conducted in terms of system throughput, delay and PLR. Finally, it will be concluded that the proposed scheduler satisfies the quality of service (QoS) requirements of the real-time traffic in terms of packet loss ratio (PLR), average throughput and packet delay. Because of the traffic evolution, some key issues related to scheduling strategies that will be considered in the future requirements are discussed in this article.
A downlink scheduler supporting real time services in LTE cellular networksUniversity of Piraeus
The wide spread of real-time services in wireless networks demands scheduling mechanisms supporting strict Quality of Service (QoS) requirements. Nevertheless, the specifications of the LTE standard for mobile connectivity defined by the 3rd Generation Partnership Project (3GPP) does not impose any specific scheduler for the proper allocation of resources to services. Therefore, several LTE schedulers have been proposed in the literature meeting the QoS requirements of modern services. In this paper a QoS aware scheduler for the LTE downlink is proposed namely the FLS-Advanced (FLSA) aiming at prioritizing real-time traffic. The proposed scheduler has been built on three distinct levels assigning the available radio resources to services according to their requirements. Based on simulation results, the FLSA outperforms in terms of packet loss ratio, attainable throughput and fairness the performance of existing schedulers including PF, MLWDF, EXP/PF, FLS, EXP RULE and LOG RULE.
The 3GPP Long Term Evolution Advanced (LTE-A) standard specifies a set of pioneer features such as relay nodes and carrier aggregation. At the same time, the Software Defined Networks (SDN) have become an emerging technology which provides centralized control and programmability to modern networks. In the current communication environment, cloud computing could combine the advantages of both technologies in order to create a novel cloud assisted Software Defined LTEA architecture with relay nodes. Moreover, due to the increased requirements of modern services, the optimal resource allocation is a necessity. In such a context, this paper describes a QoS aware cross carrier scheduler for downlink flows, aiming at the optimization of system resources allocation. The proposed scheduler is evaluated against the PF, MLWDF, EXP/PF, EXP RULE, LOG RULE, FLS and FLSA schedulers in a cloud assisted Software Defined LTE-A topology with relay nodes. Simulation results show that the proposed scheduler improves the real time services performance while at the same time maintains an acceptable performance for best effort flows.
Dynamic bandwidth allocation scheme in lr pon with performance modelling and ...IJCNCJournal
We consider models of telecommunication systems that incorporate probability, dense real-time and data.
We present a new formal abstraction method for computing minimum and maximum reachability
probabilities for such models. Our approach uses strictly local formal abstract steps to reduce both the size
of abstract specifications generated and the complexity of operations needed, in comparison to previous
approaches of this kind. A selection of large case studies are implemented the techniques and evaluate,
which include some infinite-state probabilistic real time models, demonstrating improvements over existing
tools in several cases. The capacity of metro and access networks are extended the reach and split ratio of
the conventional Long - Reach Passive Optical Networks (LR-PONs). The efficient solutions of LR-PONs
are appeared in feeder distances around 100km and high split ratios up to 1000-way . Among many
existing approaches, one of the most effective options to improve network performance in LR-PONs are the
multi-thread based dynamic bandwidth allocation (DBA) scheme where several bandwidth allocation
processes are performed in parallel is considered. Without proper intercommunication between the
overlapped threads, multi-thread DBA may lose efficiency and even perform worse than the conventional
single thread algorithm. Real Time Probabilistic Systems are used to evaluate a typical PON systems
performance. This approach is more convenient, flexible, and lower cost than the former simulation method,
which do not need develop special hardware and software tools. Moreover, how changes in performance
depend on changes in the particular modes can be easily analysis by supplying ranges for parameter values.
The proposed algorithm with traditional DBA is compared, and shows its advantage on average packet
delay. The key parameters of the algorithm are analysed and optimized, such as initiating and tuning
multiple threads, inter -thread scheduling, and fairness among users. The algorithms advantage in
numerical results are decreased the average packet delay and improve network throughput under varying
offered loads.
Machine Learning Based Session Drop Prediction in LTE Networks and its SON As...Ericsson
Abnormal bearer session release (i.e. bearer session drop) in cellular telecommunication networks may seriously impact the quality of experience of mobile users. The latest mobile technologies enable high granularity real-time reporting of all conditions of individual sessions, which gives rise to use data analytics methods to process and monetize this data for network optimization. One such example for analytics is Machine Learning (ML) to predict session drops well before the end of session.
MODELING, IMPLEMENTATION AND PERFORMANCE ANALYSIS OF MOBILITY LOAD BALANCING ...IJCNCJournal
We propose in this paper a simulation implementation of Self-Organizing Networks (SON) optimization
related to mobility load balancing (MLB) for LTE systems using ns-3 [1]. The implementation is achieved
toward two MLB algorithms dynamically adjusting handover (HO) parameters based on the Reference
Signal Received Power (RSRP) measurements. Such adjustments are done with respect to loads of both an
overloaded cell and its cells’ neighbours having enough available resources enabling to achieve load
balancing. Numerical investigations through selected key performance indicators (KPIs) of the proposed
MLB algorithms when compared with another HO algorithm (already implemented in ns-3) based on A3
event [2] highlight the significant MLB gains provided in terms global network throughput, packet loss rate
and the number of successful HO without incurring significant overhead.
Recital Study of Various Congestion Control Protocols in wireless networkiosrjce
IOSR Journal of Computer Engineering (IOSR-JCE) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of computer engineering and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in computer technology. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
LTE Network is the common mobile technology these days around the world and all service providers seek to how improve the network capacity and deliver the best performance in terms of delivered data rates and coverage area. LTE network consists of many protocols that work together to establish network connectivity, these protocols add variable headers that contains many control information that the network needs to operate. At the same time these headers decrease the effective capacity of the network, so there is a need to optimize the overhead size that used in various channels. The study will illustrate the different overheads that effect on the network capacity and investigate the effect of different values on achieving the best network capacity.
Performing Network Simulators of TCP with E2E Network Model over UMTS NetworksAM Publications,India
Wireless links losses result in poor TCP throughput since losses are perceived as congestion by TCP with the evolution of 3G technologies like Universal Mobile Telecommunication System (UMTS), the usage of TCP has become more popular for a reliable end-to-end (e2e) data delivery. However, TCP was initially designed for wired networks and therefore it suffers performance degradation due to the radio signal getting affected by fading, shadowing and interference. There are many strategies proposed by the research community on how to improve the performance of TCP over wireless links such as introducing link-layer retransmission, explicitly notifying the sender of network conditions or using new variants of TCP. As UMTS network coverage and availability are currently experiencing rapid growth, optimization of various internal components of its wireless network is very important. One of the optimization is the introduction of High Speed Downlink Packet Access (HSDPA). This architecture not only allows higher data rates but also more reliable data transfer by the introduction of Hybrid ARQ (HARQ). With this enhancement to the UMTS network, it becomes vital to see the performance of TCP in such a network. Therefore in this thesis, we try to evaluate two aspects of UMTS networks: first, the impact of HSDPA parameters like scheduling algorithm and RLC/MAC-hs buffer size on overall performance of TCP and second, to study the behaviour of two categories of TCP rate and flow control: loss based and delay based. Our simulation shows that delay based TCP tends to perform better than loss based TCP in our selected scenarios. The simulations are performed using the network simulator NS-2 with an e2e network model for enhanced UMTS (EURANE).
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S URVEY OF L TE D OWNLINK S CHEDULERS A LGORITHMS IN O PEN A CCESS S IMULATION T OOLS N S -3 AND L TE -S IM
1. International Journal of Wireless & Mobile Networks (IJWMN) Vol. 7, No. 2, April 2015
DOI : 10.5121/ijwmn.2015.7201 1
SURVEY OF LTE DOWNLINK SCHEDULERS
ALGORITHMS IN OPEN ACCESS SIMULATION
TOOLS NS-3 AND LTE-SIM
Ramprasad Subramanian, Pantha Ghosal, Shouman Barua, Shiqi Xing, Sinhlam
Cong, Haider Al Kim and Kumbesan Sandrasegaran
Centre for Real-time Information Networks,School of Computing and Communications,
Faculty of Engineering and Information,Technology, University of Technology Sydney,
Sydney, Australia
ABSTRACT
The 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 people. New tools are developed and introduced in the
market to interpret the results of the new algorithms proposed by various people. Some tools are open
access which are free to use but some tools are produced by the companies which are not open access. In
this paper some of the open access simulation tools like LTE-Sim and NS-3 are analyzed and LTE downlink
scheduler algorithms are simulated using those tools. 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 simulators are performed.
KEYWORDS
Round robin (RR), Proportional fair (PF), Maximum throughput scheduler (MT), Throughput to average
scheduler (TTA), Blind equal throughput scheduler (BET), Token bank fair queue scheduler (TBFQ),
Priority set scheduler (PS).
1.INTRODUCTION
LTE evolved from the earlier 3GPP system known as Universal Mobile Telecommunication
System (UMTS), which in turn was evolved from Global System for Mobile Communication
(GSM). In 2004, 3GPP started the work on LTE. The main aim was to deliver high data rates
with low latency. In the new architecture the circuit switched (CS) core was replaced by packet
switched (PS) core, which takes care of voice and data traffic unlike its predecessor (UMTS) the
voice functions was handled by CS core and data is handled by PS core. The main motive of the
research in LTE is to deliver a peak data rate of 100 Mbps in downlink 50 Mbps in uplink. But
the expectation of the data rates specified above was exceeded in the final system, which
delivered the peak data rate of 300 Mbps in downlink and 75 Mbps in the uplink. In LTE, the
communication is available in different frequency bands, of different sizes. Furthermore, the LTE
can use both the paired and un-paired bands for the communication. In paired, the same
frequency is used in both the uplink and downlink but whereas in unpaired, the uplink and
downlink uses different frequency bands. In LTE downlink transmissions, frame length of 10 ms
are used and grouped by radio transmission. Then each radio frame is created by 10 subframes of
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1ms duration. Therefore both the uplink and downlink uses ten subframes. Thereafter the
subframes are divided into the two slots with the duration 0.5 ms for each part.
2. SCHEDULING IN LTE
The physical layer resources for uplink and downlink shared channel (UL-SCH and DL-SCH) are
allocated by the evolved node (eNB). The resources that are allocated for the uplink shared
channel and downlink shared channel contains of physical resources blocks (PRB) and
modulation coding scheme (MCS). The bit rate is determined by MCS and the capacity is
determined by PRBs. These allocation of MCS and PRBs are done for one or more TTIs and the
duration for each interval for TTI is one subframe (1ms). The downlink control channel is carried
by LTE PDCCH (physical downlink control channel). DCI has all the information about
allocation of RBs, power control command, uplink grant and MCS to be used etc. The DCI
messages are scheduled for every TTI for users to increases the control overhead during high
traffic scenarios. The control overhead becomes a blockage in the case where the limited
resources is used for control information and this may result in the degradation of quality of
service (QoS). So in-order to maintain a middle path and to prevail over this problem an concept
called persistent scheduling is introduced, in this scheme the idle and non-idle periods are pre-
assigned by control overhead of the user specific RBs over a time sequence. The user know about
the allocation of TTI/RB in advance and apart from that, the eNB is also aware of this pre-
assignment in advance, when and where it should decode PDSCH (Physical Downlink Shared
Channel), without any additional PDCCH overhead. Major disadvantage of the persistent
scheduling is that due to various factors like user mobility, channel quality, doppler effect and
interference etc the TTI/RB cannot be persistent in real time due. So in order to correctly decode
at the receiver an average RB requires multiple transmission. For this reason, the research is
going on in the semi persistent scheduling is ongoing.
In semi persistent signalling, the control signalling is greatly reduced and in this scheduling every
allocation is not signalled and this will ultimately reduce the signalling load. For example in voice
over IP (VoIP) application, if each frame in the downlink that has the duration for every 10 ms to
20 ms is signalled then this will greatly increase the overall signalling load and it will consume
more bandwidth. Semi-persistent scheduling allows to setup an ongoing allocation that persists
until it is changed. Both uplink and downlink can be provisioned with semi-persistent schedules.
2.1 DOWNLINK SCHEDULING
The cell radio network temporary (C-RNTI) information is obtained by the PDCCH, and this is a
dynamic UE identifier and this is used as an indicator that indicates the impending downlink
resource has been demultiplexed by the MAC and passed on to upper layers and is now scheduled
for the UE. The recurrence of the semi-persistent scheduling is provisioned by the radio resource
control (RRC). The usage of the scrambling codes denotes the scheduling schemes nature that is
dynamic or semi-persistent for the C-RNTI on PDCCH. The PDCCH uses very low bandwidth
because it will not carry lot of information unlike the downlink DL-SCH.
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Figure. 1.Dynamic Scheduling (Freescale semiconductor et al.,)
The semi persistent scheduling information is included in Figure 2 from the Figure 1. Here, the
semi persistence is provisioned by the RRC. This illustration shows a four-TTI example. When
the first time it occurs there is signalling on the downlink PDCCH but after that, for every four
TTIs transmission occurs without any signalling on the control channel. The dynamic scheduling
is used for other purposes and this remains the same until it is changed by some other indication
propagated in the control channel.
Figure. 2.Dynamic Scheduling (Freescale semiconductor et al.,)
2.2 DOWNLINK SCHEDULING WITH HARQ
Figure 3 is an incremental figure of the scheme specified in Figure 2. In Figure 2, the C-RNTI is
carried by PDCCH and this adds to the downlink scheduling with HARQ. This indicates that the
next downlink resource is scheduled for this UE.
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Figure. 3. Downlink Scheduling with HARQ(Freescale semiconductor et al.,)
In Figure 4 the ACK/NACK process that is specified is added to Figure 3 and HARQ process
generates an ACK or NACK, which is sent on layer 1 or 2 (L1/L2) control channel (PUCCH) on
the subframe n+4, on the every downlink transport block. Here in this situation if there is a
negative acknowledgement, so a subframe needs to be transmitted again using HARQ. The
retransmission is signalled dynamically and it is downlinked, then it is decoded and sent to upper
layers. Again in the final, the subframe has to be again acknowledged. The process becomes
intricate when both acknowledgements and semipersistent scheduling are involved.
Figure. 4.ACK/NACK Process in Downlink Scheduling (Freescale semiconductor et al.,)
3. FRAMEWORK
Several LTE downlink algorithms have proposed by various researchers in academia and industry
and in future several algorithms would be proposed and these algorithms would focus on several
QoS aspects. So in order to provide a valid reference to the researchers in future who are working
in this area an attempt is made to survey some of the models available in open access simulation
tools like LTE-Sim and NS-3. In various forums there are lot of ongoing discussions about what
simulation tools can be used for generating various downlink scheduling algorithms. So an
attempt has been made to survey these two open access tools so that this paper will be a guide to
future researchers.
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There are couple of algorithms NS-3 can support [1-2] and made available to the research
community. Initially NS-3 came up with two scheduling algorithms namely Round robin (RR)
and Proportional fair (PF). But more scheduling algorithms were needed for the research
community. So in-order to make the NS-3 more powerful and useful to the research community,
other algorithms like maximum throughput (MT), throughput to average (TTA), blind equal
throughput (BET), token bank fair queue (TBFQ) and priority set (PSS) algorithms were added to
the NS-3 repository[5]. These scheduling algorithms does the radio resource allocation either by
time domain approach (TD) or frequency domain approach (FD). In the Time domain approach
the LTE system assigns all the system resources to one UE during the particular transmission
interval. In frequency domain the resource is allocated to UE based on frequency and time
domains.
4. NS-3 DOWNLINK SCHEDULING ALORITHMS
4.1 ROUND ROBIN (RR)
This is one of the first algorithm that was supported by NS-3 and it is the simplest algorithm. This
algorithm works like a ration where the time slots are assigned to every process in a equal share
in the round robin fashion and in this algorithm all the process are handled without any priority.
This algorithm is starvation free. The excess flows will be allocated in a circular fashion in
another subframes, since it cannot be allocated in the same subframe. The MCS will be decided
depending upon the received channel quality indicator (CQI) for each users.
4. 2 PROPORTIONAL FAIR (PF)
In this algorithm, when the UE has high channel quality compared to the average channel
condition with respect to the time, the resources are allocated to the UE[7]. with respect to the
time. The PF can explained mathematically as:
Let users are denoted as ; let subframe index can be defined as , and the resource blocks can
be defined as be the resource block index; let modulation coding sequence (MCS) is defined as
for the user and on the resource block and let be the TB size in bits for
that can serve and often it is the case where a number of resource blocks is used. The
achievable rat that is represented as in bit/s for can be specified as the below equation
(1) user on resource block at subframe is defined as
(1)
where, the TTI duration of the can be the TTI duration. Each user is assigned with the resource
block at the start of the every subframe . In detail, the index to which RB is assigned at
time is determined as
(2)
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where can be denoted as the past throughput performance professed by the user . As per
the above scheduling algorithm, a user can be assigned to various RBGs, that can be adjacent or
non adjacent which depends on the present channel condition and the past performance on
throughput . At the end of the subframe the past throughput performance can be
determined by using the following exponential moving average approach:
(3)
where is represented as time constant (in number of subframes) of the exponential moving
average, and the actual throughput can be denoted as achieved by the user in the
subframe . is measured as the following procedure. First we determine the MCS
actually used by user :
(4)
then we determine the total number of RBs allocated to user :
(5)
where indicates the cardinality of the set; finally,
(6)
4.3 MAXIMUM THROUGHPUT SCHEDULER (MT)
As the names suggests, the main idea of this algorithm is to provide the maximum throughput to a
eNB [3][6]. In this algorithm, the RBG is assigned to each individual UE so as to attain maximum
data rate in the current TTI.
Let the users can be denoted as ; and can be defined as the subframe index, and can be
specified as the resource block index; let can be defined as th MCS usable by user on
the resource block and let can be defined as the TB size in bits for the case where a
number of resource blocks is used. The achievable rate can be defined as in bit/s for
the user on the resource block at the subframe can be defined as
(7)
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where can be specified as the TTI duration. At the beginning of the every subframe , every
user is assigned with the RB. In detail, the index to which RB is assigned at time is
determined as
(8)
When in the case of multiple UEs with the same achievable rate, the present implementation
always selects the first UE that is created in the script. Even though MT can provide maximum
cell throughput but it cannot provide the fairness to UEs that are in experiencing poor channel
condition.
4.4 THROUGHPUT TO AVERAGE SCHEDULER (TTA)
This scheduler algorithm can be assumed as an intermediate between MT and PF[3][6]. The
metrics used in this algorithm can be calculated as follows:
(9)
Here, the achievable rate can be denoted as in bit/s for user on resource block at
subframe The calculation methodology is already discussed in the MT and PF. Meanwhile,
in bit/s denotes the achievable rate for th
user at subframe . The difference in those two
different achievable rates is how to get MCS. For , MCS can be calculated by sub-band
CQI while can be calculated by wideband CQI. TTA scheduler can only be implemented
in frequency domain (FD) because the achievable rate of particular RBG is only related to FD
scheduling.
4.5 BLIND EQUAL THROUGHPUT SCHEDULER (BET)
As the name suggest, this algorithm does not take the channel condition into consideration for
resource allocation, BET provides equal resource to all the UEs in the same eNB[3][6]. Unlike
Mt and TTA, this algorithm is a channel unaware scheduling algorithm. This algorithm uses
wideband CQI in the scheduling decision in both frequency domain BET and time domain BET.
The scheduling decision by BET can be best explained by as follows:
(10)
where the past performance on throughput can be denoted as by the user and that can be
calculated by the similar method as in PF scheduler. In the time domain flavour of the algorithm,
the blind average throughput (TD-BET) scheduler selects the UE with highest priority metric and
the it allocates all the RBGs to this UE. On the other hand, in the frequency domain flavour of the
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blind average throughput (FD-BET), every TTI, the scheduler selects the UE with the lowest
average throughput in the past (largest priority metric). After this the scheduler, then assigns one
RBG to this UE, it then calculates the expected throughput of this UE and uses this to compare
with past average throughput with other UEs. This UE will be assigned with the RBG by
the scheduler until the expected throughput is better than the past throughput of all UE.
Then the same method will be used by the scheduler to allocate RBG for a new UE which has the
lowest past average throughput and this happens until all RBGs are allocated to UEs. The
principle idea behind this algorithm is that, in every TTI, the scheduler tries to achieve the equal
throughput among all the UEs in the best possible way.
4.6 TOKEN BANK FAIR QUEUE SCHEDULER (TBFQ)
This algorithm is designed from leaky bucket mechanism and this TBFQ [4] is a downlink based
QoS aware scheduler algorithm. The traffic flow of this scheduler is denoted as follows
ݐ : packet arrival rate (byte/sec)
ݎ : token generation rate (byte/sec)
: token pool size (byte)
ܧ : This is the counter that records the number of token borrowed from or given to the token
bank by flow i.
ܧcan be smaller than zero.
Each K bytes of data consumes k number of tokens. Apart from this, this algorithm in order to
balance the traffic between different flows, it maintains a shared token bank. If rate ݎ the token
generation is bigger than rate ݐ the packet arrival, then the tokens overflowing from token pool
are added to the token bank, and ܧ cab be increased by the same amount. Otherwise, the flow i
needs to withdraw the tokens from the token bank based on the priority metric and ܧis decreased.
Obviously, the user that contributes more for the token bank also has the highest priority to
borrow the tokens; on the other hand, the vice versa also applies, that is the user who borrows
more tokens from bank has the lowest priority to continue to withdraw tokens. Therefore, in the
case of many users that are having the similar token generation rate, traffic rate and token pool
size, suffers with higher interference and has more opportunity to borrow tokens from bank.
Apart from this, this algorithm can also control the traffic by limiting the token generate rate to
limit the throughput. Additionally, this algorithm can also maintain the following three
parameters for each flow:
• Debt limit ݀: if ܧ is less than certain threshold, user ݅ cannot borrow tokens further from
the token bank. This mechanism is designed for preventing the malicious UE to borrow too many
number of tokens.
• Credit limit ܿ: this can be defined as the maximum number of tokens that a UE i can
borrow from the token bank at one time.
• Credit threshold :ܥ This can be defined as, once when ܧ reaches the debt limit, UE i can
store ܥ tokens to the bank in order to further borrow tokens from the token bank.
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4.7 PRIORITY SET SCHEDULER (PS)
This is another QoS aware scheduler algorithms that combines both the frequency domain (TD)
and time domain (FD) packet scheduling algorithms into one scheduler algorithm [3]. The
fairness among the UE is controlled by defining a specified target bit rate (TBR). In the TD, the
UE with non empty RLC buffer is selected by the scheduler and then they are divided into two
sets based on the TBR:
set 1: UEs with the past throughput average is lesser than TBR; TD scheduler calculates its
priority met- ric
ଵ
(t) following the BET.
ଵ
(t) =
ଵ
்(௧)
(11)
set 2: UEs with the past throughput average is larger (or equal) than TBR; TD scheduler
calculates its priority metric p2k(t) following the proportional fair (PF)approach:
ଶ
(t) =
ோ(,௧)
்(௧)
(12)
Here, the achievable data rate ܴ(݇, )ݐ for the UE ݆ at time the k−th RBG and ܶ()ݐ is the average
past throughput of the UE ݆ and at the time .ݐ The UEs that are belonging to the set 1 can be
considered with a higher priority than the UEs in set 2. This algorithm selects the ܰ݉ݔݑ UEs
with the highest metric in the two sets and forward those UEs to FD scheduler.
5.SIMULATION RESULTS OF VARIOUS SHCEDULING SCHEMES
IN NS-3
In the previous sections various scheduling algorithms has be defined theoretically and in this
section we validate the scheduler and comparison would be made to validate the performance
with some theoretical reference scenarios. The decision of validating against theoretical
performance is mainly motivated by the lack of equivalent measurements from real LTE
deployments that could be used for the same purpose. A particular set of scenarios are chosen
with the simple assumptions so that it becomes possible to determine the theoretical performance
of the scheduling and verify the accuracy of the implementations of the scheduler. We also note
that, because of to these simplifying assumptions made, these scenarios might not be necessarily
represent of real world conditions and deployments; in fact, the large scale simulation involving
real time network conditions are beyond the scope of this paper, and are therefore these
conditions are left for future study. For each well throughout scenarios, the reference throughput
from each UE is calculated and this in turn cross verified with the obtained throughput to check
whether this matches with the reference throughput within a given tolerance (equal to 10% of the
throughput in this paper).
The simulation parameters values that are common to all the considered scenarios are given in the
table 1. Since the phenomena of fading is not considered and the UEs are assumed to be
stationary and it is configured as stationary nodes, because of this consideration each UE will
have the same SINR for the entire whole simulation. In other words, both wideband and sub-band
CQIs of UEs are assumed to be constants and their values are related to the distance between UE
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and eNB. The minimum allocation unit in the entire simulation is RBG and that contains two
RBGs in the test cases. It is also stressed that the bitmap allocation is coded in allocation type 0.
In addition, we also use varying traffic patterns for QoS unaware and QoS aware schedulers.
Specifically, the schedulers like MT, TTA and BET, are QoS unaware schedulers, it assumed that
the RLC buffer for each UE is saturated always by using the ns-3 RLC saturation mode
(RLC/SM) model. In this way, the simulation can fully reflect the RBG allocation behaviour of
different scheduling algorithms. On the other hand, for the algorithms like TBFQ and PSS, the
UDP traffics with different constant bit rates are generated in order to evaluate the unique feature
of QoS aware schedulers.
All the schedulers that has been mentioned in this paper has been tested for two basic scenarios
and they are:
• scenario I: In this scenario it is assumed that all the UEs are separated at the same distance to
the eNB so that all the UEs can have same CQI both wideband and sub-band.
• scenario II: In this scenario, the UE are planned to have different distance to the eNB in order to
have different CQI both wideband and sub-band.
The simulation time for all test cases for all the schedulers is 1 seconds in order to decrease the
overall testing time in ns-3. This choice is acceptable due to the stationary UE and standard CQI
throughout the simulation, which results in a very short union of time for the performance of the
scheduling algorithms. In this section, we use TYX to indicate the UE reference throughput for
any particular scheduler X and in scenario Y . At the end of the each test result the number of
UEs are represented as ܰ. We would like to stress that the validation of the schedulers is mainly
focused on the resources in the magnitude of throughput statistics for all the algorithms, based on
the assigned have policies and resources in terms of bitrates and this work aims at verifying their
correct design. The more realistic scenarios and conditions are left for future work and for future
work apart from the scenarios we are also planning to take the conditions like delay, jitter,
fairness etc will also be considered.
Distance between
the eNB and UE
(Km)
UE throughput
(KB/s)
Reference
throughput
UE
throughput
(KB/s)
FD-MT
throughput
UE throughput
(KB/s)
TD-MT
throughput
UE throughput
(KB/s)
TTA
throughput
0 2250 2250 2250 2250
5 1750 1750 1750 1750
10 800 800 800 800
15 500 500 500 500
20 200 200 200 200
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6. LTE-Sim OPEN ACCESS SIMULATION TOOL FOR LTE
To the best of the knowledge and unlike the other open source simulators, LTE-Sim has complete
LTE protocol stack, multi-cell environments with uplink flows and realistic applications. LTE-
Sim is written in C++ and is a well-known object oriented plat and it is a event driven simulator.
The four main modules of LTE-Sim as defined in [8] are: a) the Simulator, b) the Network
Manager, c) the Flows manager and d) the Frame Manager. Now we will elaborate each
functionalities: the simulator performs the function of starting - scheduling - running and stops
every events, Frame Manager defines the LTE frame structure (starting and stopping of Sub-
frames), the Network Manager creates each node and devices (eNB, Femtocell-Picocell, UE),
manages positioning, Bandwidth and user mobility etc and the Flow Manager generates and
handles applications such as VoIP, Video. Separate class is created for each network in the LTE
architecture in this simulator i.e., eNB class, UE class, MME class etc. The whole of the LTE
protocol stack is implemented with three network nodes, i.e., UE, eNB, and MME which forms
the application to PHY layer that includes radio link control(RLC), radio resource control(RRC)
and MAC entities. These network nodes can either be destination or source and maintain the flow
of data through source and destination IP addresses, ports and transport protocol. The data flow,
resource allocation and maintenance of QoS are performed by packet schedulers that are located
at eNB. LTE-Sim supports some of the well known scheduling algorithms such as PF, MLWDF,
ExPF, FLS and Log scheduling. LTE-Sim also supports CQI feedback by utilizing the channel
quality estimation report from the UE and converting it to the set of CQI feedbacks reported to
eNB and several other features. In the application layer of LTE-Sim, four traffic generators have
been developed (trace-based, on-off, infinite buffer and constant bit rate). Packet transmission
and propagation models are covered by the simulator's Channel module using four different
phenomena as suggested in the path loss, the penetration loss, the shadowing and the fast fading
due to the signal multipath. All the aforementioned features give it the flexibility and modularity
to device a complete system for simulating LTE network in LTE-Sim.
6.1 SIMULATION RESULTS IN LTE-SIM
In this paper an evaluation of different packet scheduler algorithms such as PF, M-LWDF
and EXP/PF supported by LTE-Sim is simulated in terms of packet loss Ratio, packet delay,
average throughput, fairness index and Spectral efficiency with varying number of users and user
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speed. Simulation scenario is considered in an urban macro cell with cell coverage of 1 KM with
the presence on interference and propagation loss. Fairness index is measured by Jain’s fairness
[9] method. All the users are experiencing single flow (50% of the users are having VoIP flow
and the rest are having Video flow) modelled with infinite buffer application. Users (varied from
10 to 40) are moving with the speed either of 3kmph or 12kmph.Simulation parameters is
summarized in Table. 2
Table2. Simulation Parameters
Bandwidth 10 MHz
Frame Structure FDD
Cell Radious 1 KM
User Speed 3 Kmph, 120 Kmph
Flow Duration 80 sec
Maximum Delay .1 Sec
Video Bit rate 242 kbps
From Figure 9 it can be seen that for all the schedulers, average throughput (Video and VoIP) is
decreasing with the increase in user speed. With the increase in user speed, the channel quality
experienced by the user becomes worse and lower order MCS are selected which results in
decreased average throughput of Video and VoIP flow.
9(a) 9(b)
Figure 9. Average Throughput of a)VoIP and b)Video Flow with different schedulers at different
speed
Figure 10a shows, for video flow, packet delay remains almost the same for M-LWDF and
EXP/PF with increasing user number and speed while delay increases with PF. For VoIP, packet
delay increases with speed and user number for all the scheduling algorithms, which is show in
Figure 10b.
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10 (a) 10 (b)
Figure 10. Delay in a)Video and b)VoIP Flow with different schedulers at different speed
In LTE, link adaptation becomes complex with user speed which results in increasing packet loss,
which is demonstrated in Figure.10, where for all the schedulers the packet loss increases with
speed. Figure. 11 shows the spectral efficiency degrades with user speed irrespective of
scheduling algorithms used
11(a) 11(b)
Figure 11. Packet Loss Ratio of a)VoIP and b)Video Flow with different schedulers at different
speed
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Figure 12. Spectral Efficiency of different schedulers in LTE-SIM
7. CONCLUSION
NS-3 and LTE-Sim supports various downlink scheduler algorithms and the same has been
simulated. Based on the area of work, traffic type such as voice or video, number of UEs,
mobility type as speed, traffic environment such urban/suburban/rural the researchers can select
the simulation platform either NS-3 or LTE-Sim to meet the needs. NS-3 provides a rich source
of tutorials and source codes in the NS-3 repository site and since it is a open access tool these
source codes can be used and modified as the simulation plan. LTE-Sim offers a vibrant users
community in the Google group to raise any questions or doubts faced in the simulation. This
special feature of LTE-Sim negates the lack of tutorials for the beginners. The uniform feature
between these simulators are both work in Linux platform which is also another open source
operating system. The install process for these simulators are pretty simple and can be used in the
same computer.
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