Analysis On Overlapped Multiplexing Technology And Its Application

Overlapped multiplexing technologies is general term of several kinds of technologies which are based on overlapped theory. From the angle of coding, there are overlapped code division multiplexing (OVCDM) and overlapped time division multiplexing (OVTDM). Overlapped code division multiple access (OVCDMA) is the technology from the angle of multiple access. The detection algorithms and coded overlapped techniques are main topics which have been discussed in paper.OVCDM can achieve higher spectral efficiency with low order modulation because of its coding out of Galois field and combining coding and modulation together. But detection complexity of OVCDM grows rapidly with constrain length increasing, which results in finding sub-optimal or fast algorithms to deal with that problem. Simplified and fast algorithms, such as Fano algorithm, stack algorithm and parallel detection algorithm, are introduced in the paper. Meanwhile, analysis of a real coefficient parallel concatenated code structure which is different with the previous parallel concatenated is given at the end of the chapter.OVTDM is a kind of symbols overlapped in time domain and forms a convolution relationship among symbols. Comparing with traditional time division multiplexing, it can transmit more bits within same time slot without spreading spectrum through introducing inter-symbol interference intentionally. In order to reduce the complexity of detection, MMSE-SIC and stack algorithms are adopted in decoding OVTDM after the OVTDM's performance in some typical channels being introduced. Performance of coded OVTDM is studied for the purpose of improving the performance of OVTDM.OVCDMA can eliminate inter-cell interference through using expanded generalized complementary orthogonal code groups in network designing. Although there are several ways to improve the efficiency of signature sequence, the complexity problem brought by factional chip shift, joint detection of multi signature sequences and high order modulation should be solved by fast algorithms. The performance of fast detection algorithms in OVCDMA, such as Fano algorithm, stack algorithm and serial interference cancellation, are discussed in the paper. Researches about TD-OVCDMA are focused on how to obtain diversity gain under the conditions of four transmitting antennas and one receiving antenna TD-SCDMA system in ITU-UrbanMacro channel. In that research, the reason of turbo equalization not obtaining iteration gain is given after analyzing the characteristic curve of ITU-UrbanMacro channel trough EXIT chart.