Application Of Space-Time Coding In UWB Communication Systems

Ultra Wideband (UWB) is seen to be a technology for delivering very high data rates at very low power spectral densities. The most common form of UWB is Impulse Radio, which communicates using very short pulses, typically on the order of hundreds of picoseconds. Due to the short pulse duration of the pulses, UWB signals have significantly more resolvable multipath as compared to narrow signals. Therefore, UWB is a viable candidate for short range communications in dense multipath environments.Multiple-Input Multiple-Output(MIMO)system is well known for its potential of improving system performance under multipath scenarios. In particular, a large number of propagation paths between transmit and receive antennas can be utilized to combat channel fading effect and gain link reliability. By the use of Space-Time(ST)coding techniques, MIMO can provide both diversity and coding advantages simultaneously, and hence yield high spectral efficiency and remarkable quality improvement.To exploit the advantages of both UWB and MIMO systems, we propose UWB ST coded scheme. All the work can be summarized as follows:The IEEE UWB channel model, the ways of modulation and multiple access and some kinds of rake receivers are introduced here. Space-time coding technology for space-block codes and layered space-time codes are given in detail.Based on the system models of single-antenna DS-UWB, how to obtain multipath diversity are given with the combination of FS rake receiver with MRC(maximum ratio combination). UWB space-time block codes scheme is presented with the finally statistical decision results .The simulation results with IEEE UWB channel model are given to compare the system performance of single-antenna with that of two antennas.The scheme for UWB layered space-time codes are proposed with its decoding algorithm. Then UWB serially concatenated layered space-time codes are presented, then the decoding algorithm of the scheme is given by the introduction of iterative soft-decision decoding algorithm for the serially concatenated system. The simulation results are used to compare system performances of the two schemes.