WiMAX

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WiMAX, the Worldwide Interoperability for Microwave Access, enables the delivery of wireless broadband services over long distances. WiMAX is based upon the IEEE 802.16 standard, also called WirelessMAN, which was developed for non-line-of-sight (LoS) communication. WiMAX technology can provide connectivity in many ways, from point-to-point links to full mobile cellular type communication. The name WiMAX was created by the WiMAX forum which was formed in June 2001.The WiMAX forum describes WiMAX as "a standards-based technology enabling the delivery of last mile wireless broadband access as an alternative to cable and DSL." WiMAX technology has already been incorporated into notebook computers and PDAs to deliver high speed mobile Internet services.[1]

Contents

Uses

High speed bandwidth and wireless connectivity make WiMAX suitable for the following potential applications:[1]

  • Connecting Wi-Fi hotspots with each other and to other parts of the Internet.
  • Providing a wireless alternative to cable and DSL for last mile broadband access.
  • Providing high-speed data and telecommunications services.

Broadband access

Many companies are examining and testing WiMAX technology for “last mile” connectivity at high data rates. The resulting competition with cable and DSL providers may bring lower prices for home and business users where internet connectivity was economically unavailable.

Mobile handset applications

Cellular companies are evaluation WiMAX technology to increases mobile bandwidth for a variety of data-intensive applications. Sprint Nextel – Announced investment of about US$ 5 billion in WiMAX technology over the next few years[2]. WiMAX networks will go live for a test launch in Chicago, Baltimore, and Washington DC. Commercial lauches are still expected to happen during spring of 2008.[3]

Technical Information

How WiMAX works.[4]

How it works

Practically WiMAX operates similar to Wi-Fi but a much higher speeds and over greater distances. A WiMAX system consists of two parts:

  • A WiMAX tower
  • A WiMAX receiver

WiMAX towers can connect directly to the internet or another WiMAX tower, using line-of-sight communication. A connection to a second tower is often called a backhaul. By using multiple towers, large, remote areas can receive WiMAX signals.[4]

WiMAX provides two forms of wireless service:

  • Non-line-of-sight, much like Wi-Fi, where a small antenna on your computer connects to the tower. These kinds of transmissions use a low frequency range, between 2 GHz to 11GHz.
  • Line-of-sight, a fixed dish antenna points directly at the receiver’s dish. This signal is much stronger and uses higher frequencies, reaching a possible maximum frequency of 66GHz.[4]

Specifications

WiMAX technology can be configured for many applications. Typically WiMAX has a broadcast radius of three to ten kilometers with bandwidth up to 40 Mbps per channel. This is enough bandwidth to support hundreds of T-1 speed connections and thousands of residential DSL speed connections.[4]

For mobile WiMAX networks, speeds up to 15 Mbps within a radius of three kilometers can be achieved.[5]

Comparison with Wi-Fi

"Due to the fact both WiMAX and Wi-Fi begin with the same two letters, are based upon IEEE standards beginning with "802.", and both have a connection to wireless connectivity and the Internet, comparisons and confusion between the two are frequent. Despite this, the two standards are aimed at different applications."[1]

  • WiMAX uses the IEEE 802.16 standard which is a newer standard of wireless networking than 802.11. *Wi-Fi operated in the unlicensed spectrum (2.4 or 5.8 GHz) making in much cheaper to deploy.
  • WiMAX has a much higher bandwidth at a maximum 70 Mbps versus Wi-Fi at 54Mbps.
  • WiMAX has a range of up to 50 kilometers compared to Wi-Fi at around 30 meters.
  • WiMAX and Wi-Fi have different Quality of Service (QoS) mechanisms. Wi-Fi uses a packet priority system while WiMAX can setup connections based on scheduling algorithms.
  • WiMAX is highly scalable.

Standards

Current WiMAX technology called Mobile WiMAX, is based on the IEEE Std 802.16e-2005[7]. This IEEE standard is an amendment of IEEE Std 802.16-2004[8], which means the actual standard is 802.16-2004 as amended by 802.16e-2005. Both standards need to be read together to understand them fully. IEEE Std 802.16-2004 addresses only fixed systems. It replaced IEEE Standards 802.16-2001, 802.16c-2002, and 802.16a-2003.

IEEE 802.16e-2005 

IEEE amendments taken directly from http://en.wikipedia.org/wiki/WiMAX#IEEE_802.16e-2005

IEEE 802.16e-2005 improves upon IEEE 802.16-2004 by:

  • Adding support for mobility (soft and hard handover between base stations). This is seen as one of the most important aspects of 802.16e-2005, and is the very basis of 'Mobile WiMAX'.
  • Scaling of the Fast Fourier Transform (FFT) to the channel bandwidth in order to keep the carrier spacing constant across different channel bandwidths (typically 1.25 MHz, 5 MHz, 10 MHz or 20 MHz). Constant carrier spacing results in a higher spectrum efficiency in wide channels, and a cost reduction in narrow channels. Also known as Scalable OFDMA (SOFDMA). Other bands not multiples of 1.25 MHz are defined in the standard, but because the allowed FFT subcarrier numbers are only 128, 512, 1024 and 2048, other frequency bands will not have exactly the same carrier spacing, which might not be optimal for implementations.
  • Improving NLOS coverage by utilizing advanced antenna diversity schemes, and hybrid-Automatic Retransmission Request (HARQ)
  • Improving capacity and coverage by introducing Adaptive Antenna Systems (AAS) and Multiple Input Multiple Output (MIMO) technology
  • Increasing system gain by use of denser sub-channelization, thereby improving indoor penetration
  • Introducing high-performance coding techniques such as Turbo Coding and Low-Density Parity Check (LDPC), enhancing security and NLOS performance
  • Introducing downlink sub-channelization, allowing administrators to trade coverage for capacity or vice versa
  • Enhanced Fast Fourier Transform algorithm can tolerate larger delay spreads, increasing resistance to multipath interference
  • Adding an extra QoS class (enhanced real-time Polling Service) more appropriate for VoIP applications.

"802.16d vendors point out that fixed WiMAX offers the benefit of available commercial products and implementations optimized for fixed access. It is a popular standard among alternative service providers and operators in developing areas due to its low cost of deployment and advanced performance in a fixed environment. Fixed WiMAX is also seen as a potential standard for backhaul of wireless base stations such as cellular, Wi-Fi or even Mobile WiMAX."[1]

Future development

The long term goal for the evolution of WiMAX is to achieve 100Mbps for mobile devices and 1 Gbps for fixed devices.

"Since the evolution of core air-link technologies has approached the practical limits imposed by Shannon's Theorem, the evolution of wireless has embarked on pursuit of the 3X to 10X+ greater bandwidth and network efficiency by advances in the spatial and smart wireless broadband networking technologies."[1]

Current deployments

The WiMAX Forum now lists over 350 WiMAX trials and deployments. Current and planned deployments and the bands in which they operate and the standards they use are listed in the article below.

List of deployed WiMAX networks

See also

Wireless Network Security
Network-Based Software Architectures
Satellite Networking

References

  1. WiMAX. Wikipedia.org.
  2. 4G Mobile Broadband. sprint.com.
  3. Sprint Preparing Soft Launch for WiMax Service. brighthand.com.
  4. How WiMAX works. howstuffworks.com.
  5. WiMAX Forum — Frequently Asked Questions. wimaxforum.org.
  6. WiMAX vs WiFi. techwarelabs.com.
  7. IEEE 802.16e Task Group (Mobile WirelessMAN®). ieee802.org.
  8. IEEE 802.16 Task Group d. ieee802.org.

External links

Goedvola 23:37, 13 April 2008 (EDT)

Retrieved from "http://wiki.cas.mcmaster.ca/index.php/WiMAX"
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