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COMMUNICATION NETWORKS
Project Title: OPNET Simulation of IEEE
802.16(WiMAX)
Spring 2010
FINAL PROJECT REPORT
Sukhchandan Lally
http://www.sfu.ca/~lally
ABSTRACT
WiMAX stands for Worldwide Interoperability for Microwave Access. It is a
telecommunication technology which provides wireless transmission. It provides access
to Internet and other portable devices. It has a transmission speed of 10 Mbps. The
name WiMAX was introduced by WiMAX Forum in 2001.It is an alternative approach to
deliver content over cable and other links at “last mile” (which is from a communication
provider to a customer.
WiMAX provides a theoretical maximum data rate of 75 Mbps on a single channel, and
is designed to deliver next-generation high-speed mobile voice, video, and data
services to a large geographical area.
WiMAX has the ability to support various types of applications, such as web browsing,
email, and file transfer. Connecting Wi-Fi hotspots to the Internet, providing a wireless
alternative to cable and Digital Subscriber Line (DSL) for broadband access, providing
data, telecommunications and Internet Protocol television (IPTV) services and providing
portable connectivity. However, for applications that require real-time response, such as
voice over IP (VoIP), streaming video and video conferencing, its Quality of Service
(QoS) is inferior to traditional wired Internet due to packet loss over wireless mediums.
Figure 1: How WiMAX works
TABLE OF CONTENT
ABSTRACT ......................................................................................................................2
TABLE OF CONTENT .....................................................................................................4
LIST OF TABLES ............................................................................................................6
LIST OF FIGURES...........................................................................................................7
LIST OF ACRONYMS......................................................................................................9
1. INTRODUCTION........................................................................................................12
2. WiMAX (802.16e) BACKGROUND.............................................................................13
3. VIDEO STREAMING OVERVIEW..............................................................................18
4. COMPARISON OF WiFi AND WiMAX ......................................................................20
5. SIMULATION .............................................................................................................22
5.1) Simulation tool.........................................................................................................22
5.2) Simulation Setup.....................................................................................................22
5.3) General Description of Scenarios ...........................................................................23
5.4) Scenarios.................................................................................................................23
Scenario 1:......................................................................................................................23
Scenario 2:......................................................................................................................25
6. SIMULATION RESULTS............................................................................................27
Scenario 1:......................................................................................................................26
Scenario 2:......................................................................................................................33
7. CONCLUSION ...........................................................................................................35
8. FUTURE WORK ........................................................................................................35
9. REFERENCES...........................................................................................................36
LIST OF TABLES
Table 1: WiFi and WiMAX Comparison [13]...........................................................17
Table 2: WiMAX parameters...................................................................................21
Table 3: WiFi parameters .......................................................................................22
LIST OF FIGURES
Figure 1: How WiMAX works [11].....................................................................................3
Figure 2: WiMAX client station connection [1]................................................................16
Figure 3: Variety of wireless technologies [1] ................................................................19
Figure 4: Overview of the simulation setup.....................................................................23
Figure 5: Subnet 1..........................................................................................................24
Figure 6: Subnet 2. ........................................................................................................24
Figure 7: LAN..................................................................................................................25
Figure 8: Video Conferencing.........................................................................................27
Figure 9: WiMAX.............................................................................................................28
Figure 10: UDP for Server of Subnet 1 ..........................................................................28
Figure 11: WiMAX parameters for Base Station of Subnet2..........................................29
Figure 12: UDP for Mobile node of Subnet 2..................................................................30
Figure 13: Video Conferencing for Mobile node of Subnet 2..........................................31
Figure 14: WiMAX parameters for Router of Subnet 2...................................................31
Figure 15: WiMAX delay for Base station and Router of Subnet 2.................................32
Figure 16: WiMAX : BS Free Downlink and Uplink Capacity..........................................32
Figure 17: WLAN parameters of the Campus Network..................................................33
Figure 18: WLAN of AP in Campus Network (In stacked statistics)...............................34
Figure 19: WLAN of AP in Campus Network (In overlaid statistics)...............................34
LIST OF ACRONYMS
3G 3rd Generation Networks
4G 4th Generation Networks
ADSL Asymmetric Digital Subscriber Line
AP Access Point
BER Bit Error Rate
Bps bits per second
Bps Bytes per second
BS Base Station
CCK Complementary Code Keying
CDMA Cellular Division Multiple Access
CSMA/CA Carrier Sense Multiple Access/Collision Avoidance
DSL Digital Subscriber Line
DSP Digital Signal Processing
DSSS Direct Sequence Spread Spectrum
FDD Frequency Division Duplexing
FFT Fast Fourier Transform
GPS Global Positioning System
GSM Global System for Mobile
IEEE Institute of Electrical and Electronics Engineers
ITU International Telecommunication Union
LAN Local Area Network
LOS Line Of Sight
LTE Long Term Evolution
MAC Media Access Control
MAN Metropolitan Area Network
Mbit/s megabits/second
MIMO Multiple input multiple output
MPEG Motion Picture Experts Group
MS Mobile Station
ms millisecond
OFDM Orthogonal Frequency Division Multiplexing
OFDMA Orthogonal Frequency Division Multiple Access
PAN Personal Area Network
PC Personal Computer
PHY Physical Layer
PMP Point to multi point
P2P Peer to Peer Network
QoS Quality of Service
RF Radio Frequency
RTP Real Time Protocol
SOFDMA Scalable Orthogonal Frequency Division Multiple Access
SS WiMAX Subscriber station
SU Subscriber Unit
TCP Transmission Control Protocol
TDD Time Division Duplexing
UDP User Datagram Protocol
USB Universal Serial Bus
VoD Video on Demand
WiFi Wireless Fidelity
WiMAX Worldwide Interoperability for Microwave Access
WWAN Wireless Wide Area Network
1. INTRODUCTION
WiMAX embodies IEEE 802.16 family of standards that provide fixed and mobile
broadband access in telecommunication industry. Mobile WiMAX, is based upon IEEE
Std 802.16e-2005. It is a supplement to the IEEE Std 802.16-2004, and so the actual
standard is 802.16-2004 as amended by 802.16e-2005. Thus, these specifications need
to be considered together. WiMAX network can be connected with an IP based core
network, which is typically chosen by operators that serve as Internet Service Providers
(ISP). 802.16e-2005 uses Scalable Orthogonal Frequency-division Multiple Acess
(SOFDMA) rather than Orthogonal Frequency-division Multiplexing(OFDM).Multiple
duplexing schemes used in WiMAX are Time Division Duplexing (TDD) and Frequency
Division Duplexing (FDD). It uses Internet Protocol (IP) network architecture. It uses
Connection oriented MAC (Multiple Access Control) layer. The 802.16 specification
applies across a wide range of the Radio Frequency (RF) spectrum, and WiMAX can
function on any frequency below 66 GHz. WiMAX can either operate at higher bitrates
or over longer distances but not both: operating at the maximum range of 50 km
increases bit error rate and thus results in a much lower bitrate. It uses MIMO (Multiple-
input multiple-output) communications technology on WiMAX, which is the technology
brand name for the implementation of the standard IEEE 802.16. 802.16 specifies the
air interface at the PHY (Physical Layer) and at the MAC (Medium Access Control layer.
WiMAX is a possible replacement candidate for cellular phone technologies such as
GSM (Global System for Mobile) and CDMA (Cellular Division Multiple Access), or can
be used as an overlay to increase capacity. There are numerous devices on the market
that provide connectivity to a WiMAX network. These are known as the "subscriber unit"
(SU). There is an increasing focus on portable units, this includes handsets (similar to
cellular smartphones), PC peripherals (PC Cards or USB), and embedded devices in
laptops, which are now available for Wi-Fi services. In addition, there is much emphasis
from operators on consumer electronics devices such as Gaming consoles, MP3
players and similar devices. It is notable that WiMAX is more similar to Wi-Fi than to 3G
cellular technologies.
2. WiMAX (802.16e) OVERVIEW
WiMAX provides a maximum transfer speed of 75Mbps per channel, and a maximum
range of 50km (although, not both at the same time). Compared to ADSL, which has a
maximum local-loop range of approximately 5km, WiMAX has a marked advantage in
total area coverage. Also thanks to the large coverage area, users are able to stay
connected to a high-speed internet connection while mobile, a major advantage over
ADSL and cable. WiMAX simplifies the implementation of high-speed internet access to
remote users, and is much cheaper to implement than wired systems.
This project focuses on the feasibility of using a WiMAX connection to provide last-mile
internet connection for video conferencing. WiMAX is capable of providing the required
bandwidth mentioned above over a large geographical area, however its QoS is, in
general, lower than that of a wired connection. Compared to wired connections, wireless
connections have a much higher bit error rate (BER) due to the unpredictable nature of
the transmission medium (air) and the obstacles between the transmitter and receiver.
This necessitates re transmissions, which leads to delay and jitter, and the need to
buffer incoming data.
WiMAX is often confused with Wi-Fi another wireless telecommunication standard, but
both of these standards are much different in terms of infrastructure pre-requisites and
network capabilities. Wi-Fi is basically a limited wireless extension of the conventional
wired telecommunications network, using which we can access wireless internet within
a small range of 10-100m from the Wi-Fi access point, whereas WiMAX provides long
range wireless internet access at broadband speed, with the help of a dedicated
network infrastructure, built exclusively for wireless data communication at much higher
speed.
Types: There have been majorly two developments with regard to WirelessMAN
broadband: Fixed WiMAX and Mobile WiMAX. The earlier of the two WirelessMAN
standards,Fixed WiMAX(or IEEE 802.16d) employs High gain-low portability uni-
directional antenna at user’s end and provides a limited wireless broadband access. It
supports following sub-channels: Single High Gain carrier, OFDM 256 FFT(Fast Fourier
Transform) and OFDMA 1K-FFT Mobile WiMAX (or IEEE 802.16e) takes the Wireless
broadband access to much larger coverage area as it employs Low gain-High portability
Omni-directional antennas at user’s end(in the form of Flash drive sized modem).
Mobile WiMAX supports not only Single carrier, OFDM 256 FFT and OFDMA 1K-FFT
but also OFDMA 2K-FFT, 512-FFT and 128-FFT sub-channels.
Infrastructure: Implementation of WiMAX requires a similar scale of basic
telecommunication infrastructure, as built in case of a voice communication network
(GSM, CDMA). Base Stations, sectorized antennas, control center and other critical
constituents are generally a part of such infrastructure
Coverage: WiMAX network has often been claimed in media to be capable of
providing broadband speeds to a coverage of over 30 miles (with a single base station)
but that’s possible only in ideal conditions (Line-Of-Sight (LOS) area, No real-time
traffic, negligible attenuation). Practically, a single base station can provide a
satisfactory broadband access within a range of 4-5 miles (Non-LOS and real-time
traffic conditions). With LOS conditions, the coverage can go upto 10 miles. Rest of the
coverage and Quality-of-Service (QOS) details are solely dependent upon the terrain
and population conditions
Terminology: IEEE 802.16 standard is generally referred as “WirelessMAN” but the
term “WiMAX” was actually given to IEEE 802.16 standard by WiMAX Forum,founded in
mid 2001 to take care of conformity, interoperability and promote the IEEE 802.16
standard(or Wireless broadband) at a global scale
Limitation: The major limitation of WiMAX is the effect of QOS in high traffic, non-
LOS areas. It’s quite impractical for WiMAX networks to support over 40 Mbps of
internet speed at a distance of 15-20 miles. This limitation is quite unavoidable and
found in other wireless networking standards as well.
Future: The future of WiMAX looks brighter as there are already over 475 WiMAX
networks deployed in 140 countries worldwide and the network extension is happening
at a very fast pace. See the list of deployed WiMAX networks here. Also, as it offers a
cheaper and more bandwidth-efficient way of providing Wireless broadband (compared
to 3G).
Deployment: As a standard intended to satisfy needs of next-generation data
networks (4G), WiMAX is distinguished by its dynamic burst algorithm modulation
adaptive to the physical environment the RF signal travels through. Modulation is
chosen to be more spectrally efficient (more bits per OFDM/SOFDMA symbol). That is,
when the bursts have a high signal strength and a carrier to noise plus interference ratio
(CINR), they can be more easily decoded using digital signal processing (DSP). In
contrast, operating in less favorable environments for RF communication, the system
automatically steps down to a more robust mode (burst profile) which means fewer bits
per OFDM/SOFDMA symbol; with the advantage that power per bit is higher and
therefore simpler accurate signal processing can be performed.
Burst profiles are used inverse (algorithmically dynamic) to low signal attenuation;
meaning throughput between clients and the base station is determined largely by
distance. Maximum distance is achieved by the use of the most robust burst setting;
that is, the profile with the largest MAC frame allocation trade-off requiring more
symbols (a larger portion of the MAC frame) to be allocated in transmitting a given
amount of data than if the client was closer to the base station.
The client's MAC frame and their individual burst profiles are defined as well as the
specific time allocation. However, even if this is done automatically then the practical
deployment should avoid high interference and multipath environments. The reason for
which is obviously that too much interference causes the network function poorly and
can also misrepresent the capability of the network.
The system is complex to deploy as it is necessary to track not only the signal strength
and CINR (as in systems like GSM) but also how the available frequencies will be
dynamically assigned (resulting in dynamic changes to the available bandwidth.) This
could lead to cluttered frequencies with slow response times or lost frames.
As a result the system has to be initially designed in consensus with the base station
product team to accurately project frequency use, interference, and general product
functionality.
Figure 2: WiMAX client station connection [1]
3. Video Streaming Overview
Video content refers to the video information available from video service providers;
examples include a wide range of sitcoms, newscasts, sporting events, and movies in
real-time and stored video (VoD) formats. The content is structured as a sequence of
video frames or images that are sent or “streamed” to the subscriber and displayed at a
constant frame rate [4].
Video streaming is inherently loss-tolerant yet delay-sensitive [8], which implies that
video playback on the subscriber machines may tolerate some degree of frame loss.
However, delays or variations intra-frame reception rapidly degrade the overall video
playback experience. While streaming real-time video and VoD possess different
transmission and buffering requirements from the network and the client video player,
video content may be characterized by several parameters including video format, pixel
color depth, coding scheme, and frame inter-arrival rate.
Videos are a sequence of images displayed at a constant rate and each frame contains
spatial (within) or temporal (between images) redundancy. Hence, various video coding
schemes have evolved to reduce the raw video content size by exploiting this
redundancy while balancing quality. These schemes include ITU H.26x and ISO MPEG-
x codecs. Video frame inter-arrival rates range from 10 frames to 30 frames per second.
Since queuing delays change dynamically and video packets may not necessarily
traverse the same path between the VoD server and the client station, the end-to-end
delay (referred to as jitter) will vary.
Typical streaming services utilize the User Datagram Protocol (UDP) that provides best
effort service without delay, loss, or bandwidth guarantees. Unlike Transmission Control
Protocol (TCP), UDP is connectionless, unreliable and it does not provide flow control or
congestion control. The lack of reliability and congestion control mechanisms are
desirable properties in media delivery because video servers can stream their content at
the native encoding rate of video content without being constrained by congestion
control when a packet loss occurs. Equally undesirable is the TCP retransmission
scheme given the delay sensitive nature of video applications. UDP segments are
subsequently encapsulated into unicast IP datagrams for proper addressing and routing
to the video clients. IP datagrams can be lost due to router buffer overflows or delayed
due to router congestion, which impacts the video client playback rate. Consequently,
video clients implement a buffering scheme to smooth the playback rate and
compensate for network jitter. The primary objective is to maintain a constant playback
rate that coincides with the original encoding rate. IP datagrams pass through
appropriate MAC and PHY layers and then propagate through the Internet and access
network to the video client subscriber. Video client stations buffer, decompress, and
playback the frames at a constant rate.
WiMAX is an all-IP infrastructure deployed in a point-to-multi-point (PMP) topology
where one or more subscribers communicate with a WiMAX base station. WiMAX is
able to achieve Quality of Service (QoS) by using a bandwidth request and granting
scheme on the subscriber stations. This prevents the WiMAX base station from over-
subscribing its available resources. Therefore, given the multiple air interfaces and
adaptive transmission rates, WiMAX provides a compromise between 4G mobility and
Wi-Fi throughput rates.
Figure 3. Variety of wireless technologies [1]
4. Comparison with Wi-Fi
Comparisons between WiMAX and Wi-Fi are frequent because both are related to
wireless connectivity and Internet access.
WiMAX is a long range system, covering many kilometers, that uses licensed or
unlicensed spectrum to deliver connection to a network, in most cases the
internet.
Wi-Fi uses unlicensed spectrum to provide access to a local network.
Wi-Fi is more popular in end user devices.
Wi-Fi runs on the Media Access Control's CSMA/CA protocol, which is
connectionless and contention based, whereas WiMAX runs a connection-
oriented MAC.
WiMAX and Wi-Fi have quite different quality of service (QoS) mechanisms:
1. WiMAX uses a QoS mechanism based on connections between the base
station and the user device. Each connection is based on specific scheduling
algorithms.
2. Wi-Fi uses contention access - all subscriber stations that wish to pass data
through a wireless access point (AP) are competing for the AP's attention on
a random interrupt basis. This can cause subscriber stations distant from the
AP to be repeatedly interrupted by closer stations, greatly reducing their
throughput.
Both 802.11 and 802.16 define Peer-to-Peer (P2P) and ad hoc networks, where
an end user communicates to users or servers on another Local Area Network
(LAN) using its access point or base station.
Wi-Fi and WiMAX are complementary. WiMAX network operators typically provide a
WiMAX Subscriber Unit which connects to the metropolitan WiMAX network and
provides Wi-Fi within the home or business for local devices (eg, Laptops, Wi-Fi
Handsets, iPhones) for connectivity. This enables the user to place the WiMAX
Subscriber Unit in the best reception area and still be able to use the WiMAX network
from any place within their residence.
Table 1: WiFi and WiMAX Comparison [13]
5. SIMULATION
5.1) Simulation tool
OPNET is a research oriented network simulation tool. It is a very powerful software tool
that simulates the real world behaviour of wired and wireless networks. OPNET Modeler
version 14.0 was used in this project for simulating WiMAX links. “The OPNET wireless
module and the WLAN model provide high-fidelity modeling, simulation, and analysis of
wireless networks, including the RF environment, interference, transmitter/receiver
characteristics, full protocol stack, including MAC, routing, higher layer protocols and
applications. Furthermore, the ability to incorporate node mobility and interconnection
with wire-line transport networks provide a rich and realistic modeling environment.”[11]
“The OPNET WiMAX Specialized Model is available for OPNET Modeler® Wireless
Suite and OPNET Modeler® Wireless Suite for Defense. It supports the IEEE 802.16-
2004 and IEEE 802.16e-2005 standards. It was developed by OPNET with guidance
from prominent industry leaders such as Motorola, Samsung, Alcatel-Lucent, and
France Telecom.”[12]
5.2) Simulation Set Up
In this project, I used OPNET Modeler 14.0 to simulate MPEG4 Video traffic over
WiMAX link. There is a subnet in that has a server, for streaming MPEG4 video,
connected to the Internet cloud. There is another subnet which receives the MPEG4
video data and distributes the video content from a WiMAX Base Station to the
subscriber station (SS) around it. The SS receives the WiMAX data through their
WiMAX routers and distribute the video content over WiMAX link to the computers. The
general simulation setup is shown in Figure4.
The MPEG4 video that is used in this project is Matrix III movie. This movie trace is
taken from Will Hrudey’s project [2] and he originally obtained this video trace from
Arizona State University. For this simulation, video application is chosen in order to
overload the Wireless link.
5.3) General Description of Scenarios:
There are two scenarios in this Project. In 1st scenario WiMAX and WiFi links are
measured under optimal conditions. In the second scenario different parameters for
WiFi link are measured. This test is done with maximum transmit power and Free Space
path loss model for both WiFi as well as WiMAX. For all these simulations only up to the
first 30 minutes of Matrix III is streamed from the server. For both the scenarios the 30
minutes simulation time took about 30 minutes of real time.
5.4) Scenarios:
Scenario 1
Figure 4: Overview of the simulation setup
Figure 5: Subnet 1
Figure 6: Subnet 2
Table 2: WiMAX parameters
Scenario 2
Figure 7: LAN
The purpose of this scenario is to find the maximum simulation of WiFi parameters with
the chosen parameters shown in table 3. I found WLAN delay, load, throughput for this
scenario.
Base Station (BS) Subscriber Station (SS)
Tx Power 0.3 W 0.5 W
Antenna Gain 14dBi 14dBi
Path Loss Free Space Free Space
Bandwidth 20MHz 20MHz
Table 3: WiFi (802.11) parameters
Access Point (AP) Mobile Node
Tx Power 0.1 W 0.1W
Data Rate 12Mbps 12Mbps
Receiver Power
Threshold
-95dBm
-95dBm
Buffer Size 1024000 bits 256000 bits
Short Retry Limit 7 7
Long Retry Limit 4 4
Large Packet Processing Fragment Fragment
Access Point
Fuctionality
Enabled Disabled
6. SIMULATION RESULTS
Scenario 1:
a) Figure 8 shows Video Conferencing for two subnets connected to internet. It shows
different parameters in Video Conferencing such as Packet Delay variation, Packet End
to end Delay (which is measured in seconds), Traffic received and Traffic sent (which
are both measured in bytes/sec).
Figure 8: Video Conferencing
b) Figure 9 shows the WiMAX delay (measured in seconds), WiMAX Load and WiMAX
Throughput (both measured in bits/sec)
Figure 9: WiMAX
c) Figure 10 shows UDP (User Datagram Protocol) Traffic received and Traffic sent
(both measured in bytes per second) for Server of subnet 1.
Figure 10: UDP for Server of Subnet 1
d) Figure 11 shows WiMAX parameters for Base station of Subnet 2 such as Delay,
Throughput, Load, Traffic received and Traffic sent.
Figure 11: WiMAX parameters for Base Station of Subnet 2
e) Figure 12 shows the UDP Traffic received and sent measured in bytes/sec for mobile
node of Subnet 2.
Figure 12: UDP for Mobile node of Subnet 2
f) Figure 13 shows Video Conferencing for mobile node of Subnet 2.It measures Packet
Delay, End to end Delay, Traffic received and sent over a period of 30 minutes.
Figure 13: Video Conferencing for Mobile node of Subnet 2
g) WiMAX parameters for Router of subnet 2 are shown in figure 14.It includes WiMAX
data dropped, Delay, Load, Throughput, Traffic received and traffic sent.
Figure 14: WiMAX parameters for Router of Subnet 2
h) WiMAX Delay for Base station and Router of Subnet 2 was compared.The blue dots
show delay for base station and red shows delay for router of subnet 2 is shown in
figure 15.
Figure 15: WiMAX delay for Base station and Router of Subnet 2
i) WiMAX Base station Downlink and Uplink Capacity was measured in figure 16.
Figure 16: WiMAX : BS Free Downlink and Uplink Capacity
Scenario 2:
a) WLAN parameters of the Campus Network which includes Application
Configuration, Profile Configuration, Server, Switch, Access Point and mobile
node are shown in figure 17.
Figure 17: WLAN parameters of the Campus Network
b) Figure 18 shows WLAN parameters of Access Point (AP) of Campus network and
Figure 19 shows same results in Overlaid Statistics. Figures show AP connectivity,
Delay (sec), Load (bits/sec), Media Access Delay (sec), Queue size (packets) and
Throughput (bits/sec).
J WLAN of AW WLAN of AP in Campus Network
Figure 18: In stacked statistics Figure 19: In overlaid statistics
7. CONCLUSION:
Different parameters such as Delay, Load, Throughput affect the performance of
WiMAX in a small area. The parameters for different models such as Base station,
router and subscriber station were studied. Delay for base station and router were
compared and as expected delay of router was less but it was for entire period of 30
minutes but in case of base station it had higher value but was present only for first few
minutes. As expected WiFi works better in a small area as compared to WiMAX. This
project presented several challenges, such as generating a working WiMAX network in
OPNET and setting attributes to make the network realistic. Also, learning about the
technical aspects of WiMAX and video conferencing enabled to determine a good set of
scenarios to run.
8. FUTURE WORK:
To obtain better tuning of simulation’s performance, there are several aspects of the
simulation that could be used for further work such as changing parameters for different
models used. Varying the simulated terrain between the user and the BS would effects
of different physical landscapes. The path loss model could be other than chosen Free
Space loss which was chosen for this project.Finally, increasing the video data rate to
high-quality video settings would also be beneficial and would require changing all
parameters.
9. REFERENCES
[1] W. Hrudey and Lj. Trajkovic, “Streaming video content over IEEE 802.16/WiMAX
broadband access,” OPNETWORK 2008, Washington,DC, Aug. 2008.
[2] P. Sharma, “Facts About WiMAX And Why Is It “The Future of Wireless
Broadband””, TechPluto, Jun. 20, 2009 [Online]. Available:
http://www.techpluto.com/wimax-in-detail/ (Accessed: April 2010).
[3] “WiMAX”, Wikipedia, [Online]. Available: http://en.wikipedia.org/wiki/WiMAX
(Accessed: April 2010).
[4] I. Uilecan, C. Zhou, and G. Atkin, “Framework for delivering IPTV services over
WiMAX wireless networks,” Proc. IEEE EIT 2007, Chicago, IL, May 2007, pp. 470–475.
[5] “WiMAX (802.16) specialized model”, OPNET, [Online]. Available:
http://www.opnet.com/WiMAX/index.html (Accessed: April 2010).
[6] “WiMAX Deployments”, WiMAX MAPS, Apr. 14, 2010 [Online]. Available:
http://www.wimaxmaps.org/ (Accessed: April 2010).
[7] OPNET Technologies,OPNETWORK2007 proceedings(online).Available:
http://www.opnet.com/opnetwork2007.
[8] WiMAX Forum Online.Available: http://www.wimaxforum.org/news/pressreleases.
[9] H.Nyberg, C.Johansson ,B.Olin, “A streaming video traffic model for mobile access
network,” in Proc.IEEE VTC 2001 Rhodes, Greece, Sep. 2001.
[10] H.Schulzrinne, S.Casner, R.Frederick and V.Jacobson, “Real time Protocol,” RFC
3550, Jul. 2003.
[11] “WLAN (802.11)”, OPNET, [Online]. Available:
http://www.opnet.com/support/des_model_library/WLAN80211.html
(Accessed: April 2010).
[12] “WiMAX (802.16) specialized model”, OPNET, [Online]. Available:
http://www.opnet.com/WiMAX/index.html (Accessed: April 2010).
[13] www.bioenabletech.com/.../2009/06/wifiwimax.jpg
[14] www.wifinotes.com/.../how-wimax-works-image.gif
