Jahanzeb Farooq

Implementation of I E E E 802.16 W i M A X

I am employed at INRIA France since October 2006 as a software engineer, working on development of network simulation software for wireless broadband network technology IEEE 802.16 WiMAX, which will then be integrated into NS-3. NS-3 is a next generation discrete-event network simulator software being developed as a collaboration between University of Washington, ICIR, Georgia Institute of Technology and INRIA Sophia Antipolis. The core architecture of NS-3 is based on that of YANS's (Yet Another Network Simulator), developed by Mathieu Lacage, my colleague at INRIA.

WiMAX is likely to play a key role in fixed and mobile broadband wireless metropolitan area networks. WiMAX is based on the IEEE 802.16 standard and is a cost effective fixed wireless alternative to cable and DSL services, as well as mobile wireless competitor for the GSM/UMTS networks. The objective of this project is to write simulation modules to simulate MAC and PHY layers of this new wireless access technology and to integrated them into NS-3. The project is supervised by Thierry Turletti. My job responsibilities include analysis, design and development of WiMAX simulation model. Implementation includes development of complete WiMAX MAC protocol in C++ as well as the PHY. I am very much enjoying my job although IEEE 802.16 WiMAX is a complex technology and I often found myself stuck in the technical details of how the protocol works. Anyways this is helping me becoming kind of an expert of WiMAX with the passage of time.

The block diagram of the MAC layer from the preliminary design draft is shown below. A brief overview of NS-3 and WiMAX follows next.


WiMAX MAC for NS-3: block diagram from preliminary design

NS-3

NS-3 is a next generation discrete-event network simulator for Internet systems, targeted primarily for research and educational use. The NS-3 project is funded by the National Science Foundation and is a collaboration between University of Washington, Georgia Institute of Technology and the Planete group at INRIA Sophia Antipolis. NS-3 is the next major revision of the NS-2 simulator, which is is one of the most widely used simulators in the academic and industrial community since the last decade. The work on NS-3 is still in progress. NS-3 is free software. It is covered by the GNU GPLv2 license and is publicly available for research, development, and use. More information can be found on the official NS-3 website www.nsnam.org. A tutorial is found here.

NS-3 is a user-space program that runs on Unix/Linux based systems as well as Windows (currently via Cygwin and possibly via native win32 APIs in the future). It is written in C++, with Python scripting interface for users. The focus is on IPv4 and IPv6-based networks, but other non-IP architectures such as sensors or DTNs are to be supported. NS-3 is meant to be modifiable and extendable by users; some users will be able to use example scripts that are provided, but it is expected that most (research) users will want to either write new scripts or modify or add to the simulator models in some way. NS-3 provides support for the following:

• construction of virtual networks (nodes, channels, applications) and support for items such as event schedulers, topology generators, timers, random variables, and other objects to support discrete-event network simulation focused on Internet-based and possibly other packet network systems.
• support for network emulation; the ability for simulator processes to emit and consume real network packets
• distributed simulation support; the ability for simulations to be distributed across multiple processors or machines
• support for animation of network simulations
• support for tracing, logging, and computing statistics on the simulation output

NS-3 has a modular implementation containing a core library supporting generic aspects of the simulator (debugging objects, random number generators, smart pointers, callbacks, unit tests, reference list), and a simulator library defining simulation time objects, schedulers, and events. A common library defines objects that are independent of specific network architectures, such as generic packets and tracing objects. Finally, the node library defines abstract base classes for fundamental base objects in the simulator, such as nodes, channels, and network devices. Internet-related models (IP and transport protocols) are found in the internet-node library. Specific devices such as Ethernet are in device libraries. Users may write and link their own libraries. The modular implementation allows for smaller compilation units. ns-3 executable programs may be built to either statically or dynamically link the libraries.

Source: www.nsnam.org

IEEE 802.16 WiMAX

WiMAX is a standards-based technology enabling the delivery of last mile wireless broadband access as an alternative to wired broadband like cable and DSL. WiMAX provides fixed , nomadic, portable and, soon, mobile wireless broadband connectivity without the need for direct line-of-sight (LOS) with a base station.

IEEE 802.16 defines the air interface specification for broadband wireless access systems supporting multimedia services, including the medium access control layer (MAC) and multiple physical layer (PHY) specifications. The WiMAX technology, defined as Worldwide Interoperability for Microwave Access, is based on wireless transmission methods defined by the IEEE 802.16 standard. WiMAX aims to provide wireless data over long distances, in a variety of different ways, from point to point links to full mobile cellular type access. It offers an alternative to wired networks, such as coaxial systems using cable modems, fiber optics and digital subscriber line (DSL) links. The technology supports high data rates ranging from 30 Mbps to 155 Mbps depending on the distance from the base station and the underlying PHY layer. Typical range of WiMAX is about 30 miles. While the more familiar WiFi handles local areas, such as in offices or hotspots, WiMAX covers wider, metropolitan or rural areas. WiMAX technology ideally provide data rates up to 75 megabits per second (Mbps) per base station with typical cell sizes of 2 to 10 kilometers. This is enough bandwidth to simultaneously support (through a single base station) more than 60 businesses with T1/E1-type connectivity and hundreds of homes with DSL-type connectivity.



There are two flavors of WiMAX, i.e. fixed WiMAX and Mobile WiMAX. Fixed WiMAX is optimized for fixed and nomadic applications in LOS and NLOS environments and mobile WiMAX is targeted primarily for portable and mobile applications in NLOS environment. The medium access control (MAC) layer of 802.16 supports point-to-point (PTP), point-to-multipoint (PMP) and mesh network architectures. Multiple physical layer (PHY) specifications are supported for different operational environments.

The bandwidth and reach of WiMAX make it suitable for the following potential applications:

• Connecting WiFi hotspots with each other and to other parts of the Internet (i.e., backhauling).
• Providing a wireless alternative to cable and DSL for last mile broadband access.
• Providing high-speed data and telecommunications services.
• Providing nomadic, portable, and mobile connectivity.

WiMAX changes the last mile problem for broadband in the same way as WiFi (WLAN 802.11) has changed the last one hundred feet of networking. WiMAX has a range of up to 30 miles, which can be used to provide both campus-level network connectivity and a wireless last-mile approach that can bring high-speed networking and Internet service directly to customers. This is especially useful in those areas that are not served by cable or DSL or areas where the local telephone company may need a long time to deploy broadband service. While the 30-mile range of the WiMAX wireless networking standard promises to eventually connect individuals over vast distances, the technology is currently being tested as a backhaul solution. In the role of backhaul, WiMAX can aggregate WiFi network connections and link them to the Internet. It can also provide flexible long-range connectivity to wired government campuses and other LANs.

Given the tremendous popularity it is gaining, the industry analysts believe the WiMAX market will be worth anywhere from $3 billion to $5 billion by year 2009.

The WiMAX Forum is the organization dedicated to certifying the interoperability of WiMAX products. Those that pass conformance and interoperability testing achieve the "WiMAX Forum Certified" designation and can display this mark on their products and marketing materials. The WiMAX Forum was established in June 2001 and is an industry-led, not-for-profit organization of more than 490 companies to include over 200 operators formed to certify and promote broadband wireless products. Some of the prominent names are Intel, Motorola, Nokia, Ericsson, Alcatel-Lucent, and AT&T, Siemens AG, Cisco Systems, Nortel Networks, Samsung, Sprint, Fujitsu and Proxim. Complete list of companies associated with WiMAX Forum is found here. A FAQ on WiMAX standard, technology, companies/industry, WiMAX forum, certifications etc is located here. Some other good sources are www.wimax.com and www.wimax-industry.com.