performance measurements and analysis of quality of
TRANSCRIPT
Performance Measurements and Analysis of Quality of Service in WiMAX
Networks Using Network Simulator NS-2
1Jokhu Lal,
2Dr. Neeraj Tyagi
1Research Scholar CSED, MNNITAllahabad, India
Email: [email protected] 2Professor and Head of Department
CSED, MNNIT Allahabad, India
Email:[email protected]
Abstract
In recent years, there is tremendous growth in the field of wireless communication due to the
availability of portable low cost devices and demand for computation and communication while one is
on move and using number of applications supported by Broadband Wireless Access (BWA)
Networks. Among these networks IEEE802.16, also known by trade name as WiMAX support
different applications like, Voice over IP, Video and Audio streaming, data transport and web access
with Quality of Service (QoS) in mind. Due to slow progress of deployment of Wired Broadband
network (such as ADSL, Cable Modem, Fiber Optical Cable etc.) in rural area, this new technology is
spreading very fast everywhere due to cost effective alternative and ease of deployment.
Our work focuses on performance measurements and analyzing Quality of services for WiMAX
Networks using Network Simulator NS-2. We have used WiMAX module version 2.6 to simulate at
NS-2 to measure the performance for different types of traffic with parameters like throughput, delay,
jitter and packet loss which decide the Quality of Service. From analysis of these parameters for
different type of Services for WiMAX, we find that better results are obtained for those Service flows
which are designed for a particular application groups.
Keywords: WiMAX;QoS; BWA; UGS; OFDMA; NS-2.
1.Introduction In recent past, there has been exponential growth for use of communication network due to
availability of high speed core network and fast progress in access networks. In local loop there is
deployment of fiber optic links, coaxial cables and DSL. Now users have choice to use number of
multimedia applications such as VOIP, video and audio conference, video streaming, online gaming
and data communication on these high speed access networks, which are based on bandwidth and
delay constraints. Complementing and competing with these access network is Broadband wireless
access network which is used today everywhere for reliable, ease and cost effective Internet access.
The latest one such high speed technology is WiMAX network [1][2]. In rural and suburban part of
most of developing countries where DSL or cable based connection are not available, WiMAX may
be boon as it may be installed very rapidly at low cost investment for sparsely scattered residential
user. For small and medium enterprises also, WiMAX will provide a cost effective solution which are
using costly leased line based access. This may also be used as a complement solution like backhaul
to Wi-Fi hotspot, cellular, public safety and private networks. One such use case is shown in Figure 1.
The presence of different types of applications leads to heterogeneous type of traffic load. The main
problem with BWA network is to provide QoS for different applications at changing network
conditions as wireless link characteristic is changing with time and location. When a packet is
traversing from source to destination in WiMAX network, it experiences delay, jitter, packet loss and
out of order delivery.
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Figure 1: A WiMAX Network Application Scenario.
Considering these issues IEEE802.16 standard includes Quality of Service (QoS) mechanism at MAC
layer. Responsibility of MAC layer among other is to allocate bandwidth as required by different user
applications. It allocates bandwidth based on needs of applications and their QoS preferences. Large
number of applications supported by WiMAX network is grouped in five QoS classes. These services
can be initiated, changed or terminated by Dynamic Service Addition (DSA), Dynamic Service
Change (DSC) and Dynamic Service Deletion (DSD) command message. Both BS and SS can initiate
these message by a two or three- way handshake procedure. To start a service at SS, after detecting a
flow, it calculates whether resources are available or not. If available it sends a DSA message to BS.
On receiving of DSA from SS, BS checks whether request may be supported or not and sends a
response to SS. After getting response from BS, SS sends DSA acknowledgement to BS and new
service is initiated. We included WiMAX Module version 2.6 in Network Simulator NS-2 for
simulation and analyzing of different network scenario and load to measure different QoS parameters.
Throughput, delay, delay variation and packet loss parameters are considered. Simulations scenario is
taken for streaming of multimedia traffic and its effect on different QoS parameters are analyzed.
1.1 WiMAX Functioning Overview
WiMAX standard focused on Physical and MAC layer access due to changing wireless link
conditions and requirements of QoS for different applications. Other higher layer protocols are
generally common for all networks. WiMAX standard works in two modes for sharing medium [1],
[2], [15]. These are Point to Point (PMP) Mode and Mesh Mode. In Point to Point Mode, a Centralize
Base Station (BS) is controller of all communication within its cell and sectors. In communication
from BS to SSs it is broadcast, which is received by all Subscriber Stations (SSs). Transmission from
SSs to BS is directed to and coordinated by BS. In Mesh Mode each node communicates with other
up to BS in the way, thus it works on distributed manner. We are considering here Point to Point
Mode.
1.2 Physical Layer of WiMAX
WiMAX supports wireless MAN-SC, OFDM and OFDMA as physical layers for different
purpose. Wireless MAN-SC was designed for 10 to 60 GHz Spectrum in Line of Sight (LOS)
scenario. Due to very high frequency, these bands are being affected by rain, interference and
multipath effect, thus there are no products available in these frequencies.For Non Line of Sight
(NLOS) communication, WiMAX standardized OFDM PHY below 11GHz frequencies for fixed SSs
also known as IEEE802.16d. Here SSs use Time Division Multiple Access (TDMA) mode to share
media. In OFDM which is a multi-carrier transmission where several sub carriers are used for
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transmission and control of all sub carriers are given to a user at a time. Time slots are allotted to SS
for transmission. In case of mobile subscriber, numbers of users transmit simultaneously using
different sub carrier at same time slot. Thus scheduling is done to allocate sub carriers and time slot to
different users. OFDMA which is norms today for WiMAX PHY is combination of time and
frequency division multiple access.In wireless transmission, state of channel is changing over time, so
Adaptive Modulation and Coding scheme is used based on channel condition. Both MS and BS
estimate about channel condition based on downlink and uplink packets signal strength
respectivelyand finaldecision for most efficient modulation and coding scheme for transmission is
taken by BS.
1.3 MAC Layer of WiMAX
802.16 MAC is connection oriented. A connection which is unidirectionalis made, before
transmission of data.In WiMAX Standard, data transmissions are frame based and partitioned in
uplink and downlink subframe. Downlink transmission from BS to SS is broadcast in downlink sub
frame but only intended SS receives data. In uplink sub frame, SSs transmit data to BS in TDMA slot
assigned to it. Downlink and uplink sub frame are duplex in either FDD where downlink and uplink
sub frames are to be transmitted at same time on different frequencies or TDD where uplink sub frame
follows downlink sub frame at different time on same frequency[3]. At start of each downlink sub
frame, the BS broadcast UL and DL MAP as shown in Figure 2. In these maps there are information
about start and end time of grants of UL and DL sub frame for SSs.
Figure 2: WiMAX Downlink and Uplink Subframe for FDD and TDD.
On beginning of each downlink sub frame, BS sends a sequence of physical preambles to let
synchronize SSs. Also to synchronize with BS uplink scheduler each SS sends a physical preamble
before transmitting data. Service Data Unit (SDU) from upper layers is encapsulated in as Protocol
Data Unit (PDU) by MAC layer and a six byte header is included in MAC Protocol Data Unit
(MPDU). Here bandwidth is requested based on the queue size of a connection on connection basis,
but BS allocates grants on the base of SS. Thus SS scheduler distributed these grants among
connections based on various constraints.
Request for bandwidth may be either incremental basis or aggregate basis. On aggregate
basis, SS requests bandwidth based on whole backlog of the queue, but in case of incremental basis
SS calculate bandwidth request based on difference between current backlog of queue and one carried
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by last bandwidth request. Bandwidth may be requested by any one or mixed of following
mechanism: - unsolicited, unicast polling, broadcast/multicast polls and piggybacking.
There are number of network applications available and increasing continuously day by day.
These are grouped in QoS classes. There are five QoS classes as shown in Table 1:- Unsolicited Grant
Service (UGS), Real Time Polling Service (rtPS), Extended Real Time Polling Service (ertPS), Non
Real Time Polling Service (nrtPS) and Best Effort Service (BE).
Table1: Different QoS Services Classes with use case and QoS specifications in WiMAX system
UGS is used for real time applications with stringent on delay and delay variationswith CBR
type traffic at periodic interval are taken such as TI/EI and VOIP communication. Here grants are
periodic and base period and grants size are given at connection setup phase. SS connection with UGS
service then not request for bandwidth thereafter.
rtPS service class is less stringent on delay, it generates variable size real time application
packets at regular interval like MPEG video. BS provides unicast poll periodically which base period
is decided at connection setup. This period can be set to the interval at which application generate
SDU. When BS polled a SS, SS submit its bandwidth request based on its current queue backlog size
and BS allocate grant in next frame for transmission of data.
ertPS uses efficiency and features of both UGS and rtPS. To overcome delay constraints BS
allocate grants at regular interval in an unsolicited manner like used in UGS and thus save time of
bandwidth requesting. But like rtPS, allocations in ertPS are of variable size. For example, trafficlike
Voice over IP with silence suppression came in this category.
nrtPS and BE services are for application which have no specific delay requirements. The
nrtPS connections are given a minimum bandwidth with Minimum Reserved Traffic Rate (MRTR)
parameters. BS grants unicast polls to nrtPS connections for a large time-scale, which may be upto
one second. nrtPSconnections also use contention based bandwidth requests in response to BS
broadcast or multicast polls which are given in UL-MAP. Main drawback of this mechanism is that
when two or more SSs send bandwidth request in same contention slot, the collision occurred. A
bandwidth request is considered lost if there is not grant from BS in specific time (nearly 50 ms) [3].
BE connection use only contention based slot and piggybacking for bandwidth request as there is no
guaranteed service for this class.
To avoid collision in bandwidth request, SS randomly select a number in its back off window,
which gives the number of contention slots to which defer before sending. Thus this polling is used
for traffics which have no fixed delay constraints, such as bursty web access services. Also, an SS can
send unsolicited bandwidth request for non UGS backlogged connection by using part of grants issued
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for its data transmission. In another technique, incremental unsolicited bandwidth request may be
piggybacked with PDU by 2 bytes MAC sub header.
1.4 Band width Request and Grant Mechanism
In case of down link traffic, BS is the sole controller as it know all about of traffic such as queue
lengths and packet size to make the scheduling decisions. For uplink traffic, SSs send bandwidth
request to BS, which decide how many slots to grant in next uplink sub frame as shown in Figure 3.
Figure 3: Bandwidth Request and Grant Mechanism in WiMAX.
For BE and nrtPS connections, SS sends contention based band width request to BS when
there are backlogged queues on SS side. After receiving grants SS transmits packets to BS. It may be
possible that new packets come to backlogged queue in between. In that case SS can send incremental
bandwidth request by means of specific MAC header or by piggybacking the request with
transmitting connection PDU. A minimum number of contention slots or bandwidth minimum is
reserved in each uplink subframe for broadcast polls [10]. For rtPS connections there are unicast polls
on fixed interval. Polling period of each connection is equal to inter arrival time of SDU, i.e. for video
conferencing 33ms and for VOIP 20ms [3]. For nrtPS connections unicast polls may be set to 500ms
to 1 second [4].
2.Related Works
Different Authors have worked on QoS parameters in WiMAX network for different service
classes. Authors in [4] have investigated in details quality of service parameters for FDD, but
duerequirement of separate transmitter and receiver devices and extra hardware, cost of equipments
for FDD are high. Authors in [6] have simulated and analyzed by taking VOIP type traffic into
account for various QoS parameters, but their focus was for BE service class and its parameters.
Authors in [7] have simulated and analyzed for UGS and ertPS service classes for comparison of
performance of these two service classes. Authors in [8], havealso analyzed performance of only UGS
service class for different QoS parameters. Authors in [5] have simulated and analyzed QoS
parameters for BE, UGS and rtPS service classes only using VOIP and multimedia traffic but they did
not consider nrtPS service class. Authors in [9] have taken VOIP traffic with different codec to
analyze UGS, rtPS and BE service class only for different QoS parameters. Continuing our work [11]
we have measured and analyzed various QoS parameters such as throughput, packet loss, average
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delay and average jitter of different service classes for video traffic based on WiMAX module 2.6
integrated with NS-2.
3.Proposed work
With the help of QoS, Systems reliability and accuracy are measured. To measure QoS
quantitatively parameters like throughput, packet loss, delay and jitter or variation in delay of arrival
of consecutive packet are used. By taking a real time video streaming traffic simulation was done and
these parameters were measured and analyzed for different service classes.These parameters are
defined as follows:
3.1 Parametersfor Quality of Service Throughput: Numbers of Packets send per second or per time slot is known as throughput. It is rate
of data or packets transferred in unit time through a network. For calculation of throughput TP, in
Equation 1, PacketSizei is the packet size of ith packet which reached the destination node, PacketSt0
is the start time of first packet from the source node and Packetarrn is the last packet arrival time at
destination node.
TP=∑𝑖 PacketSize 𝑖
Packetarr 𝑛−PacketSt 0
Equation1: Calculation of Throughput
In above equation every transferred packet size is added to total transfer of data. Difference
between time of first packet starting time from source node and last packet arrival time at destination
node is calculated as total time.
Delay: Time taken by a packet to traverse from source node to destination node is known as delay or
latency. Delays in packets are due to: processing delay, transmission delay, propagation or traversal
delay, network or queuing delay. In equation 2 average delay is calculated as packetarri is time when
packet reaches destination node and PacketSti, is the time when packet “i” leaves the source node and
“n” is total number of packets.
Average Delay=∑𝑖 Packetarr 𝑖−PacketSt 𝑖
n
Equation2: Calculation of Average Delay or Latency
Jitter: Delay variation of two consecutive packets between source node and destination node is
known as jitter between packets. Jitter reveals the variation in latency in network due to congested
network, different route followed packets, queuing time at nodes followed by packets etc. Jitter
reveals stability and effectiveness of a network.In equation 3 show the steps to calculate average jitter.
It is the average of absolute difference in time it takes for consecutive packets to reach the destination
node.
AverageJitter =∑𝑖⃒ Packet arr𝑖𝑒 − Packet St𝑖𝑒𝑡 − (Packet arr𝑖 − Packet St𝑖)⃒
n − 1
Equation3: Calculation of Average Jitter
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Packet Loss: It revealed the perceived quality of applications. Packets losses are due to several
reasons such as error in bits, overflowing of buffers, congested networks etc.Packet loss is the ratioof
sum of all packets which are not reaching to destination node over the sum of packets which leaves
the source node and can be calculated as shown in equation 4.
𝑃𝑎𝑐𝑘𝑒𝑡𝐿𝑜𝑠𝑠 =∑ Lost Packet Size𝑖
∑Packet Size𝑗× 100
Equation4: Calculation of Packet Loss
3.2Details of Simulation WiMAX network was simulated with help of network simulator (NS-2) [13]. WiMAX
module patch release version 2.6 [14] was integrated with NS-2. In dynamic nature of networks
network simulator NS-2 have proved useful as it is simple event driven network simulator. It have
good support for simulation of TCP, routing protocols and multicasting protocols for wired and
wireless networks. Core of simulator is written in C++ and it uses OTcl script as interpreter.
Configuration of network and traffic agents etc is specified in TCL file. Different Simulation steps of
WiMAX on NS-2 are shown in Figure 4.
Figure 4: Simulation Steps of WiMAX Module on Network Simulator NS-2
For different network scenariosTCL Scripts were written and that was run on NS-2 which
produces trace files. To calculate throughput, packet losses, delay and jitter from these trace filesperl
scripts were used. Graphs are plotted using GNU Plot. The traffic is started after some time to allow
mobile node to complete registration as after simulation starts each node goes through basic
registration procedure to get associated with base station.
3.3 Results andAnalysis A real time scenario is considered to analyze QoS for WiMAX. As due to availability of wide
bandwidth, today streaming videos on Internet is a common phenomenon. We used video streaming
for analysis of different service classes.
Video traffic generated from different subscriber stations are set up. Video streaming falls in
Variable Bit Rate (VBR) type traffic, where packet size changed on the basis of frame type. For
example in case of MPEG traffic, „I‟ and „B‟ frames are smaller in size than a „P‟ frame, At the same
time for H.263 traffic there are „I‟ frames, „P‟ frames and „PB‟ frames. Due to simplicity in MPEG-4
video coding with enhanced compression performance and to provide a network friendly video
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representation, we have taken MPEG-4 data stream of high quality for simulation purpose. Over
Networks, video streams packets are transported.Transport protocol used for this purpose is Real-time
Transport Protocol (RTP).
To obtain VBR frame stream Mr. Bean movie with high quality MPEG-4 encoded was used
from the website in [12]. A trace file is generatedusing this file.This trace file is attached to the UDP
agent as a traffic source. The trace file which is in binary format contains information of time, frame
number, frame type and packet size etc. Analysis is done using BE, nrtPS, rtPS and UGS services
flows for the video traffic. The parameters for analysis are throughput, packet loss, delay and jitter.
These parameters are observed for each service flow by increasingnumber of nodes for video traffic.
Figure 5Show the variation of throughput for video traffic in case of increasing number of
nodes. In comparison of with BE and nrtPS service flows, rtPS and UGS service flows have higher
throughput.There is lowest throughput for BE service flow. If we compare UGS service flow with
other service flows, UGS have much higher throughput than BE and nrtPS service flow, and rtPS
service flow throughput was nearly equal to that of UGS for same number of nodes.
Figure 5: Throughput of video traffic for different service flows with increasing Number of Nodes.
As UGS grants are fixed on periodic basis in each round of scheduling and there is no packet
loss due to this it has high throughput. For rtPS, as BS polls each SS for grant of bandwidths in each
frame, and due to this number of control packets are being used, for this reason some packets get
loosed. In case of nrtPS polling interval are large and there is contention based request so there is no
guarantees of bandwidth allocation in each frame. For BE as there is no guaranteed service,
bandwidths are allotted only when there is remaining resource after serving three types of services.
Due to that there is lowest throughput for this service class.
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Figure 6: Packet loss of video traffic for different service flows with increasing Number of Nodes.
Figure6above showspacket loss for four service flows. In case of UGS service flow,there is constant
packet loss.The reason behind this is due to UGS bandwidth grant is fixed in each round on regular
interval, so packets are being sent in every round. For BE and nrtPS service flows packet loss increase
as the number of nodes increase. Value of packet loss is less if number of nodes is less for BE and
nrtPS service flow but it increases rapidly for increasing number of nodes.When numbers of nodes are
less, then adequate resources are available for nrtPS and BE service flows but on increasingnumber of
nodes there are chances for collisions of packets due to contention for requests of grant for resources
and thus more packet loss. For rtPS service flow there is slight variation in packet loss as number of
nodes increases and it is lowest amongall flows. This is due to the factthat each SS is polled by BS to
take request on regular interval and thus packets are sent on regular basis without collisions.
Figure 7: Average Delay of video traffic for different service flows with increasing Number of Nodes.
Figure 7 shows the average delay for four service flows on increasing number of nodes. UGS
service flow has higher delay but variation in delay is lessin comparisons to BE, nrtPS and rtPS flows.
Due to the fact thatgrants for UGS service flows are fixed on regular interval, but video traffic is of
VBR nature all packets are not sent on time for these flows. BE service flow got bandwidth allotted
only when there is any remaining resource available after serving all service flows. For BE service
flow average delay increases rapidly in comparison with rtPS service flowas number of nodes
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increases due to collision of packets as there is no guaranteed allocation of resources for these flows .
Although value of average delay is higherfor rtPS service flow than nrtPS service flow but variation
in delay is less than nrtPS service flow. The reason is that for rtPS bandwidths are allotted on regular
basis and for nrtPS, it is allotted on large polled interval as well as contention basis in which there is
collision of bandwidth request packets. As in case of BE service flow the value of delay increases in
nrtPS service flow also as number of nodes increases.
InFigure 8 below, it shows changes in average jitter for BE, nrtPS, rtPS and UGS service
flows with increasing number of nodes. From figure,it seems that there is no any relation with jitter
valueand number of nodes for UGS service flow. This is due to the fact that there is fixed allocation
for UGSservice flow and video traffic is a variable bit rate service and all packets are not being served
in fixed intervals thus delay variation in packets are not fixed. In case of rtPS service flowbandwidth
request is sent by each SS based on packets in queue requirement on fixed interval, so it has lowest
jitter among all service flows for maximum number of nodes and it is nearly constant.BE and nrtPS
service flows have lower jitter for small number of nodes, but it increases rapidly as number nodes
increases. This is due to the fact that at the time when bandwidth is available, video traffic for BE and
nrtPS service flows introduced least jitter, but on increasing the number of nodes, the network
resources are being distributed between all nodes, and thus results in increasing jitter for
these service flows. For rtPS service flows there is small changes in average jitter with the increasing
nodes due to guaranteed allocation of resources and it remains nearly constant for increasing numbers
of nodes.
Figure 8: Changes in average Jitter for all four service flows with increasing numbers of node for
video traffic.
4. Conclusion
The performance was analyzed for BE, nrtPS, rtPS, and UGS service flows with different
QoS parameters such as throughput, packet loss, delay and jitter and was compared for video traffic
which passed through WiMAX network with increasing number of nodes. When we consider packet
loss and average jitter, rtPS service flow is better than all three service flows. There is slight change in
variation in delay or jitter for rtPS service flow and it has least value when numbers of nodes are
being increased due to the fact that there are regular interval polling for rtPS service flow. For average
delay, value is high for rtPS than BE and nrtPS service flows, but there is slight variation in value as
number of nodes increases and in case of BE and nrtPS it increases rapidly due to non availability of
resources to these service classes and also due to collisions of packets. The delay is maximumfor UGS
service flow as it is of VBR type of traffic and allocations for UGS service flow are fixed in each
frame thus all packets are not being sent on regular interval. rtPS service flows show least packet loss
as number of nodes increases and throughput is much higher than BE and nrtPS service flows and is
equivalent to UGS flow for video traffic due to the fact of regular resource allocation at fixed
interval. From above it shows that rtPS service flow is best choice for streaming video traffic as in
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case of rtPS service flow bandwidth are periodically requested based on queue size which are not
fixed as in case of UGS service flow, where bandwidth are fixed on regular interval irrespective of
traffic which may be utilized or not .
References
[1].IEEE standard 802.16, “IEEE standard for Local andMetropolitan Area Networks, Part 16: Air interface forfixed Broadband Wireless Access Systems”, 2004. [2]. IEEE standard 802.16e, “IEEE Standard for Local and Metropolitan Area Networks, Part 16: Air interface for fixed and Mobile Broadband Wireless Access Systems”, 2005. *3+.C.Ciconetti, L.Lenzini and C.Ekluud, “ Quality of Service Support in IEEE 802.16 Network”, IEEE Networks, Volume 20, NO.2, 2006. *4+. C.Ciconetti, A.Erta, L.Lenzini and E.Mingozzi, “Performance Evaluation of the IEEE 802.16 MAC for QoS Support”, IEEE Transactions on Mobile Computing,Vol.6, No.1, January 2007. [5]. R.A. Talwalkar and M.Ilas, “Analysis of Quality of service (QoS) in WiMAX networks”, IEEE International Conference on Networking, 2008. [6]. D.Joshi and S.Jangale, “Analysis of VOIP traffic on WiMAX using NS2 Simulator”, International Journal of Advanced Research in Computer Science and Electronics Engineering, Vol.1, Issue2, April2012. *7+. I. Adhicandra, ‘Measuring data and VOIP traffic inWiMAX networks”, Journal of Telecommunications, Volume 2, Issue 1, p1-6, April 2010. [8]. M.Vikram and N. Gupta, “Performance Analysis of QoS Parameters for WiMAX Networks”, International Journal of Engineering and Innovative Technology, Vol.1 Issue 5,May 2012. *9+. Tarik Anouri and A. Haqiq, “Performance Analysis of VOIP Traffic in WiMAX using various service Classes”, International Journal of Computer Application (0975-8887), Volume 52, No.20, August2012. [10]. Jokhu Lal and Neeraj Tyagi, “Proposal of a CombinedDownlink and Uplink Scheduling Architecture for Mobile WiMAX”, International Conference on Recent Trends in Computer Scienceand Engineering Central UniversityBihar, Patna, February,2014. [11] Jokhu Lal and Neeraj Tyagi, “Performance Analysis ofQuality of Service for Different Service Classes inWiMAX Network”,International Conference on Recent Advances in Mathematics, Statistics and Coputer Science,Bihar, India, 29-31 May 2015. [12]. “MPEG-4 and H.263 Video Traces for Network Performance Evaluation”, (Master’s Thesis) Athamnoh K.http://trace.eas.asu.edu/TRACE/pics/FrameTrace/mp4/Verbose_bean.dat. [13]. The Network Simulator ns-2 http://www.isi.edu/nsnam/ns/ . [14].NIST, Seamless and Secure mobility, NS-2 NISTWiMAX Module, http://www.antd.nist.gov/seamlessandsecure,December,2009. [15]. C.So-In, Raj Jain and A.K. Tamini, “Scheduling in IEEE 802.16e Mobile WiMAX Networks: Key Issues and a Survey”, IEEE Journal on Selected areas incommunications, Vol.27,No.2, February 2009.
Authors Biography
Jokhu Lalobtained B.Tech degree from Institute of Engineering & Technology, Lucknow,
Lucknow University, India in 1994 and M.Tech from Motilal Nehru National Institute of
Technology (MNNIT) , Allahabad, India in 2004. Presently he is pursuing Ph.D from
MNNIT, Allahabad, India. In 2004 he joined as Lecturer Computer and promoted to Head
of Department Computer in 2013 in Department of Technical Education Government of
Uttar Pradesh (India). He is currently posted at Government Girls Polytechnic, Allahabad
(India).
His research interests include Broadband Wireless Networks, Quality of Service and
Scheduling in Wireless Networks.
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Dr. Neeraj Tyagi is Professor and Head of Department, Computer Science and
Engineering, Motilal Nehru National Institute of Technology (MNNIT, formerly known as
MNREC), Allahabad, India. Dr. Tyagi has completed his B.E., M.E. and PhD from
MNNIT Allahabad in Computer Science and Engineering. Dr. Tyagi has more than 25
years of teaching and research experience and also Industrial experience of working with
renowned companies like:-G.E (Capital) - U.S.A,Electronic Data Systems (now HP
Enterprise Services) - U.S.A,Warman International- Australia. His research interests
include Mobile Computing, Vehicular Ad Hoc Network, Wireless and Sensor Network,
Routing Protocol, Unix and Linux Network Administration.He is also a member of IEEE
Communication Society.
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