WiMAX Technologies, Performance Analysis, and QoS

A typical wireless communication system contains several signal processing steps. In addition to the radio front-end, radio systems commonly incorporate several digital components such as a digital baseband processor, a media access controller, and an application processor. An overview of such a system is illustrated in Figure 1.1.
Most wireless systems contain two main computational paths, the transmit path and the receive path. In the transmit path, the baseband processor receives data from the media access control (MAC) processor and performs
• Channel coding
• Modulation
• Symbol shaping
before the data is sent to the radio front-end via a digital to analog converter (DAC). In the receive path, the RF signal is first down-converted to an analog baseband signal. The signal is then conditioned and filtered in the analog baseband circuitry. After this the signal is digitized by an analog to digital converter (ADC) and sent to the digital baseband processor that performs
• Filtering, synchronization, and gain control
• Demodulation, channel estimation, and compensation
• Forward error correction (FEC)
before the data is transferred to the MAC protocol layer.
The aim of this chapter is to give an introduction to the programmable baseband processors suited for WiMAX systems and other multimode wireless systems. Related processing challenges that influence the design of such processors are also highlighted. A mapping of the WiMAX mode IEEE
802.16d onto a programmable processor is used as an example to illustrate the computational requirements on a WiMAX system.