Single Carrier Frequency Domain Equalization In 802.16a

Nowadays, broadband wireless access technique has been an inevitable trend for wireless communication technique development. In broadband wireless communication, ISI caused by multi-path affect the performance of the communication system seriously. As a protocol of broadband wireless communication, IEEE 802.16a advises the standards of MAC layer and physics layer of broadband wireless access between 2 to 11 GHz, in which OFDM and SC-FDE are advised as transmission schemes of physics layer. In this paper, both broadband transmission schemes advised by the standard are analysed. OFDM transforms high bit-rate into low symbol-rate with serial-to-parallel, by which enlarger the symbol interval and to eliminate ISI. SC-FDE uses frequency domain inverse filter to offsetting the linear distortion of the channel based on the channel estimation in frequency domain. Essentially, eliminating the ISI by OFDM and SC-FDE is frequency domain signal processing.In this paper, channel estimation and FDE algorithm in the SC-FDE system are mainly studied. The training sequence of channel estimation in frequency domain should have flat spectrum, which can estimate channel fast and exactly. The performance can be improved by increasing the estimation precision. Then, the relationship between the length of training sequence and system performance is studied through simulation. Three algorithms of FDE are analyzed. Each algorithm has different compute complexity and equalization performance. On the condition of satisfying the system desire, different FDE algorithm should be used in different channel environment to decrease complexity, which can obtain better reliability and stability. Thus, a notion of channel adaptive equalization is presented in the paper. Relative algorithm is adaptively selected according to the channel estimation result.