IEEE Wireless Communications • October 2008
73
1536-1284/08/$25.00 © 2008 IEEE
RECENT ADVANCES AND EVOLUTION OF
WLAN AND WMAN STANDARDS
INTRODUCTION
The WiMAX Forum is a consortium of over 400
organizations interested in IEEE 802.16 based
broadband wireless access. The members include
service providers, equipment vendors, chip ven-
dors, researchers, and users. The Forum devel-
ops interoperability specifications for equipment
using IEEE 802.16 standards. IEEE standards
have many options and allow a wide range of
parameters. While this generality is good, it also
makes it difficult for equipment from two ven-
dors to interoperate unless they both choose the
same set of optional features and similar values
of various parameters. WiMAX Forum members
limit the standard options to a set of profiles
that can be implemented in products [1]. The
products are then tested for interoperability in
WiMAX Forum certification laboratories.
WiMAX Forum certification ensures that the
equipment purchased from different vendors will
interoperate. Most networking and telecommu-
nications technologies have similar interoperabil-
ity organizations; for example, the WiFi Alliance
for IEEE 802.11 wireless LAN standards.
It is important to understand the difference
between IEEE 802.16 standards and WiMAX, in
the sense that WiMAX networks implement only
a subset of the features and parameter values
allowed by the IEEE standard. For example,
IEEE 802.16 allows orthogonal frequency-divi-
sion multiple access (OFDMA) frame duration
to be 0.5 ms, 1 ms, 2 ms, and more. The WiMAX
Forum has selected just one value: 5 ms. IEEE
802.16 allows mesh mode and license exempt
mode operations. The WiMAX Forum does not
yet have a profile for these modes, so they are
more of theoretical interest at this point in time.
OFDMA frame duration has a significant impact
on the throughput and delay performance of
applications and so researchers analyzing
WiMAX networks may get very different results
just by using an incorrect value.
For performance results from two research
studies or two vendors to be comparable, it is
important that both be based on a similar set of
features and parameter values, and be represen-
tative of the real-world equipment, which in the
case of IEEE 802.16 equipment means parame-
ters and features specified in WiMAX Forum
profiles. In addition, new technologies often
have features that are not well understood and
may be modeled incorrectly. Therefore, experts
need to discuss various modeling alternatives
and select the best, if there is one.
The Application Working Group of the
WiMAX Forum is chartered to study the perfor-
mance of various applications on WiMAX net-
works and recommend best practices for
optimizing the applications’ performance. The
tasks include developing standard application
workload models. For the last three years, the
Working Group has been developing a system-
RAJ JAIN, CHAKCHAI SO-IN, AND ABDEL-KARIM AL TAMIMI,
W
ASHINGTON UNIVERSITY IN ST. LOUIS
ABSTRACT
WiMAX
1
has attracted a lot of attention
recently in the telecommunication community
including researchers, product developers, and
service providers. Numerous papers have been
published on various design issues of WiMAX
networks. Since the issues being discussed are
usually ahead of product availability, most of
these studies require simulation. It is important to
have some common features among these models
so that their results can be compared. Therefore,
the Application Working Group of the WiMAX
Forum has developed a standard simulation
methodology that describes the key features to be
simulated, the method of simulating these fea-
tures, and various parameter values to be used.
This system-level methodology has been used in
several public and commercial WiMAX simula-
tion models. This article presents a summary of
the simulation methodology, and discusses the
key issues and common mistakes in simulating
various features of network configuration, and the
physical, MAC, and application layers.
SYSTEM-LEVEL MODELING OF IEEE 802.16E
MOBILE WIMAX NETWORKS: KEY ISSUES
This work was sponsored by a grant from WiMAX Forum.
1
WiMAX, Mobile WiMAX, Fixed WiMAX, “WiMAX
Forum, WiMAX Certified, WiMAX Forum Certified, the
WiMAX Forum logo, and the WiMAX Forum Certified
logo are trademarks of the WiMAX Forum.
This article presents
a summary of the
simulation
methodology and
discusses the key
issues and common
mistakes in
simulating various
features of network
configuration,
physical layer, media
access control layer,
and application layer.
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