The Study Of Layered Space-Time Coding In Wireless Communication Systems

The major challenges in wireless communication systems are to increase spectrum efficiency and improve link reliability in the future. As studies indicate, Layered Space-Time coding technique is one of Multiple-Input Multiple-Output (MIMO) signal processing techniques, which is regarded as one of the most promising solutions for enhacing data rate and shorting efficiency resource using the multi-path transmission in the scattering environment.Especially, Vertical Bell Labor.Layered Space-Time coding (VBLAST) has become the first choice for its simple transmitter structure.Though traditional VBLAST can bring rather high band efficiency, its great shortcomings are that its complex decoding procedure which can result in the error propagation and the performance of bit error rate and the limit for the receiver antennas. The VBLAST application in the real environment is limited because of less diversity gain and less ability to anti the channel's fading and correlation and the above shortcomings.Therefor,how to construct a scheme that is able to achieve a good tradeoff between rate,reliability and complexity is the key problem for realising the practical application .The paper provides a hybrid coding architecture which means the combination of VBLAST and STBC in order to achieve simultaneous diversity and multiplexing gain and get a tradeoff between them.Then,considering that each layer for traditional VBLAST has the same transmitter power allocation (TPA) and the modulation rate, the paper discusses two modified VBLAST systems.One is the TPA scheme which combines TPA and VBLAST and is based on the minimum of the total bit error rate.The other is the iterative bit and power allocation for modified VBLAST which is based on the detection order and only needs a little feedback.VBLAST is one of spatial multiplying technologies in the multi-antenna systems. Its application has been limited because its decoding complexity is high and it needs the transmitting antenna's synchronization and the quantity of the receiving antennas is not less than that of transmitting antenna. The paper provides another space multiplexing technique called Spatial Modulation(SM) and brings in a high rate coding-Linear Dispersion coding (LD) for VBLAST system. In the end, the multiuser VBLAST system is referred in order to satisfy the requirement of the communication between the station and multiusers in the modern wireless mobile communication systems.The multiuser MIMO system Based on VBLAST structure is simply discussed.