Space-Time Coding Technology In Wireless Mobile Communication

The technique of space-time coding (STC) has been advancing drastically in recentyears. This technique is mainly designed to combat channel fading in downlinktransmission by combining the technique of channel coding and that of array diversity,hence increasing the capacity of wireless communications systems and giving diversitygain and coding gain to them. It can also improve the bandwidth efficiency oftraditional single-antenna systems. This technique is intended to provide new solutionsto the problem of limited bandwidth. This thesis is mainly focused on the space-time coding technique by combiningarray signal processing. Firstly, we introduce the principle of space-time code and givethe design criteria of it for quasi-static flat-fading channels. Secondly, we classifyspace-time coding into two types according to CSI available at both the transmitter andthe receiver or not. The first type coding includes Layered Space-Time Coding (LSTC),Space-Time Trellis Coding (STTC) and Space-Time Block Coding (STBC). And thesecond type coding includes Unitary Space-Time Coding (USTC) and DifferentialSpace-Time Coding (DSTC). Then we detail their encoding and decoding theories,features, and performances. Also the comparison between them is presented.Simultaneously, we present the examples and simulation results of them. At the same time, two kind of new space-time coding are presented in thisdissertation for combating the disadvantages of the classical space-time codlings,namely, Layered Space-Time Block Coding (LSTBC) and high code-rate DifferentialSpace-Time Coding. At last we investigate the combination of space-time codingtechnique and orthogonal frequency division multiplexing (OFDM) technique,especially the combination of LSTBC and OFDM. In this thesis, the author makes the following contributions: 1. An improved Space-Time Coding is suggested which is based the layeredstructure and Space-Time Block Coding, as we name it as Layered Space-Time BlockCoding. It combines the advantages of LSTC and STBC. At the receive antennas thegroup interference suppression is used, along with a singular value decomposition (SVD)decoding algorithm. The new approach has higher spectrum efficiency and higher coderate than STBC. Simulation results show that the proposed approach outperformsBLAST at the ability of combating fading. 2. A new differential detection scheme for transmit diversity is present, whenneither the transmitter nor the receiver has the channel state information. It still remainsthe advantage of detection without CSI as DSTC. Moreover it has the advantages of lowencoding and decoding complexity, high code rate. Of course the system can get acertain spreading gain at hand as the spreading codes. 3. We combine the LSTBC and OFDM in frequency selective channels. Analysisshows that OFDM-STC can improve diversity because of the frequency selectivity.