Saturday, September 19, 2009

WiMAX Radio Overview

A WiMAX radio channel is a communications channel that uses radio waves to transfer information from a source to a destination. It may transport one or many communication channels and communication circuits on a single RF channel.

WiMAX radio channels may operate within different frequency bands, have different radio channel bandwidths, dynamically change modulation types, use a variety of access technologies and other characteristics that allow WiMAX to reliably provide a variety of types of communication services.

The WiMAX radio systems can use a single carrier (SC) or multi-carrier (MC) transmission. Single carrier transmission is the use of a single carrier wave that is modified to carry (transport) all of the information. Multi-carrier is a communication system that combines or binds together two or more communication carrier signals (carrier channels) to produce a single communication channel. This single communication channel has capabilities (capacity) beyond any of the individual carriers that have been combined. When each of the carriers in a multi-carrier system is mutually independent (orthogonal) to each other, it is called orthogonal frequency division multiplexing (OFDM).

Figure 1 shows the key components of a basic WiMAX radio system. The major component of a WiMAX system include subscriber station (SS), a base station (BS) and interconnection gateways to datacom (e.g. Internet) and telecom (e.g. PSTN). An antenna and receiver (subscriber station) in the home or business converts the microwave radio signals into broadband data signals for distribution. In the example, a WiMAX system is being used to provide telephone and broadband data communication services. When used for telephone services, the WiMAX system converts broadcast signals to an audio format (such as VoIP) for distribution to IP telephones or analog telephone adapter (ATA) boxes. When WiMAX is used for broadband data, the WiMAX system also connects the Internet through a gateway to the Internet. The WiMAX system can reach distances of up to 50 km when operating at lower frequencies (2-11 GHz).

Figure 1: WiMax System
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