Issues on Broadband Wireless Communication Systems: Channel Estimation, Frequency Synchronization and Space-Time-Frequency Coding

“Faster, higher, stronger”– the Olympic motto is being pursued and practised in the design of broadband wireless communication systems. Motivated by the huge demands for fast and reliable communications over wireless channels, broadband communication systems are required to provide faster (lowcomplexity) data processing, higher data throughput and stronger (lower error rate) performance. In practice, however, broadband communication systems must cope with critical performance-limiting challenges that include timeand frequency-selective fading channels, noise, inter-symbol interference (ISI), intercarrier interference (ICI) as well as power and bandwidth constraints. To address these challenges, this thesis investigates several physical layer aspects of broadband wireless communication systems. Orthogonal frequency division multiplexing (OFDM) is an effective technique to eliminate ISI in broadband wireless communications. This thesis studies the problem of training-based OFDM channel estimation and proposes a training method that minimizes the number of pilots employed to achieve a desired bit error rate (BER) performance. A clustered pilot pattern is further proposed to enhance the BER performance. Focusing on OFDM frequency synchronization, this thesis also proposes a clustered pilot tones placement and a novel pilot sequence design for carrier frequency offset (CFO) compensation. The analytical and simulation results show that the root mean square error (RMSE) of the CFO estimate can be greatly reduced. Incorporating OFDM into multiple-input multiple-output (MIMO) system, MIMO-OFDM has been shown to provide larger channel capacity and greater diversity gain. However, current coding schemes for MIMO-OFDM are either