Overview of WiMAX technology
Introduction
After years of development and uncertainty, a standards based interoperable solution is emerging for wireless broadband. A broad industry consortium, the Worldwide Interoperability for Microwave Access (WiMAX) Forum has begun certifying broadband wireless products for interoperability and compliance with a standard. WiMAX is based on wireless metropolitan area networking (WMAN) standards developed by the IEEE 802.16 group and adopted by both IEEE and the ETSI HIPERMAN group. In this chapter, we present a concise technical overview of the emerging WiMAX solution for broadband wireless.
We begin the chapter by summarizing the activities of the IEEE 802.16 group and its relation to WiMAX. Next, we discuss the salient features of WiMAX and briefly describe the physical and MAC-layer characteristics of WiMAX. Service aspects, such as quality of service, security, and mobility, are discussed, and reference network architecture is presented. The chapter ends with a brief discussion of expected WiMAX performance.
WiMAX
WiMAX has the potential to replace a number of existing telecommunications infrastructures. In a fixed wireless configuration, it can replace the telephone company's copper wire networks, the cable TV's coaxial cable infrastructure while offering Internet Service Provider (ISP) services. In its mobile variant, WiMAX has the potential to replace cellular networks. How do we get there?
What is WiMAX?
WiMAX is stand for (Worldwide Interoperability for Microwave Access) is an emerging technology that is designed to deliver fixed, and more recently, mobile broadband connectivity. The WiMAX trade name is used to group a number of wireless technologies that have emerged from the IEEE (Institute of Electrical and Electronics Engineers) 802.16 Wireless MAN (Metropolitan Area Network) standards. The main two standards are identified as 802.16-2004 (October 2004) and802.16e (December 2005), with 802.16e introducing mobility and currently receiving a great deal of interest in the telecoms world. The diagram below summarizes different environments in which WiMAX could be employed.
WiMAX Standard
Like most IEEE standards, the 802.16 standard family consists of the basic 802.16 standard, and several, ever-increasing variations signified by adding a small alphabet to the basic specification name. The first 802.16 standard was published on 8 April 2002 and was followed by three amendments 802.16a to address issue of radio spectrum, 802.16b to address the issue of quality of service and 802.16c to address the issue of interoperability.
In September 2003, a revision project called 802.16REVd commenced aiming to align the standard with aspects of the European Telecommunications Standards Institute (ETSI) HYPERMAN standard as well as lay down conformance and test specifications. This project concluded in 2004 with the release of IEEE 802.16-2004 and the withdrawal of the earlier 802.16 documents including the a/b/c also an amendment to the standard, 802.16e, and addressing mobility was concluded in 2005. This is sometimes called “Mobile WiMAX”. The latest revisions in progress are 802.16f and g. These specifications try to address the management issues relating to 802.16 specifications, especially to 802.16e. The 802.16g defines the management plan procedures and services, and the 802.16f defines the management information base.
In addition there are amendments at pre-draft stage:
n 802.16 – Improved coexistence mechanisms for license-exempt operation. n 802.16i - Mobile management information base.
What is a Standard?
Is a published document that sets out specifications and procedures designed to ensure that a
material, product, method, or service meets its purpose and consistently performs to its intended use.
Benefits of standardized WiMAX
- Fewer product variants through a common subset of capabilities.
- Less risk, lower system costs and greater return on investment.
- Faster, cheaper access to more widely available, higher quality service.
- Significant growth potential for broadband wireless deployment in underserved markets.
- Equivalent delivery of services vs. wire line or fiber.
- Guaranteed minimum performance levels.
- Consistent levels of voice, video and data flow quality.
General features of IEEE 802.16
- Broad bandwidth 70 Mbps throughput in 20 MHz channel (in WMAN-OFDM air interface).
- Supports multiple services simultaneously with full QOS.
- Bandwidth on demand (frame by frame).
- MAC designed for efficient use of spectrum.
- Comprehensive, modern, and extensible security.
- Supports frequency allocations from <1 to 66 GHz.
- TDD and FDD (TDD dominates lately).
- Link adaptation: Adaptive modulation and coding.
- Point-to-multipoint topology, with mesh extensions.
- Support for adaptive antennas and space-time coding.
- Extensions to mobility
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