Orthogonal frequency division multiple access for broadband wireless systems: Algorithms and implementation

Motivated by the increasing demand of the modern society for high-speed reliable information exchanges anytime, anywhere, broadband wireless systems (BWS) are envisioned for future mobile communication networks. It has been widely acknowledged that the terrestrial BWS faces a formidable challenge due to the frequency-selective multipath fading propagation environment. Multi-carrier modulation (MCM) is a preferable physical layer technology for BWS, since it can efficiently mitigate the frequency-dependent distortion across a wide frequency band and simplify the equalization in a multipath fading environment. BWS also relies on the multiple access technique to divide the common transmission medium among multiple users. As a unique multiple access system based on the MCM technology, the orthogonal frequency division multiple access (OFDMA) is a promising technology for BWS.; This dissertation first introduces OFDMA systematically. The multiple access technique in OFDMA is discussed along with the comparison of different subcarrier assignment schemes. A series of enabling technologies for OFDMA, including synchronization, transceiver architecture and their performance evaluation, are then presented and organized into two parts. One is the interleaved OFDMA, the other is the generalized OFDMA. For interleaved OFDMA, the periodic signal structure is exploited resulting in a new signal model, based on which a scalable transceiver structure is created. An efficient deterministic multiuser carrier frequency offsets (CFO) estimation algorithm is designed, and the uplink frequency synchronization algorithm is derived.; The generalized OFDMA is defined in this dissertation to describe OFDMA with any kind of subcarrier assignment schemes. A perturbation matrix is derived to characterize the generalized OFDMA uplink with multiuser synchronization errors. Two algorithms are applied to restore the ideal uplink signals that would have been received if all users are synchronized. Furthermore, an efficient implementation is realized via a banded-matrix approximation to the perturbation matrix for OFDMA with large number of subcarriers.