Broadband mobile wireless communication has been receiving more and more public interest. In order to provide higher data-rate transmission, the quasi-static broadband channel characteristics as well as other fading channel issues such as intersymbol and intercarrier interference (ISI and ICI) need to be taken into consideration. Spectral efficiency is also of particular importance due to the expensive cost of subscription of a particular frequency band from local governments. Unfortunately, most current algorithms, such as coding, for improving system performance require bandwidth expansion and may induce long encoding and decoding latency in ordinary single-carrier systems....[ Read more ]

Broadband mobile wireless communication has been receiving more and more public interest. In order to provide higher data-rate transmission, the quasi-static broadband channel characteristics as well as other fading channel issues such as intersymbol and intercarrier interference (ISI and ICI) need to be taken into consideration. Spectral efficiency is also of particular importance due to the expensive cost of subscription of a particular frequency band from local governments. Unfortunately, most current algorithms, such as coding, for improving system performance require bandwidth expansion and may induce long encoding and decoding latency in ordinary single-carrier systems.

In this thesis, we introduce two novel techniques necessitating no extra bandwidth at the expense of a moderate increase in complexity. The first one is based on the traditional differential modulation with a new interpretation as a special rate-1 recursive convolutional code. With the brilliant principle of Turbo Code, iterative A-Posteriori-Probability decoding is applicable to ordinary coded differential systems in order to achieve significant interleaver gain and better performance than the conventional best system with coherent modulation and detection. The traditional concept of 3dB performance loss for differential modulation is no longer a must and an extra differential code is shown to provide even higher gains in a high code-rate system. The second one is a special diversity technique which requires no extra bandwidth. This is known as Signal Space Diversity (SSD) and the diversity benefit is intrinsic in the modulation constellation. SSD requires only simple modification in any transmitter structure and therefore can be used together with a differential code for further improving the system performance in a fading channel. The detection part can be easily incorporated into the iterative detector for the previous coded differential system with only moderate increases in complexity.

A high code-rate system is then proposed for power- and bandwidth- efficient broadband mobile wireless transmission based on the two aforementioned rate-1 techniques. We tackle the long latency problem as well as the ISI and ICI issues by using Orthogonal Frequency Division Multiplexing (OFDM) as the radio access technique. Data symbols are encoded in the frequency domain in order to utilize the delay diversity offered by OFDM for the reduction of interleaver size. The inherent loss of multipath diversity of an OFDM system is then solved by the introduction of SSD. With these two rate-1 techniques, significant gains can be achieved with a small number of iterations for not only the bit error rate (BER) performance, but also the performance of frame error rate (FER), which is an important parameter for higher-layer protocols design.