Study On Iterative Detecting Technique In SSD-DSTTD System

It’s still a severe challenge that how to get more higher rate and reliability withlimited spectrum resource. Multiple input multiple output (MIMO) technology canachieve effective communication and have a major increase in system capacity withoutincreasing extra transmitted power and bandwidths. Double space-time transmitdiversity (DSTTD) has attracted intense attention and absorbed by IEEE802.16e as abroadband wireless mobile communication standard, becase it has a good banlancebetween diversity gain and multiplexing gain, but also it has simple receiver structureand robustness against correlated fading channels. DSTTD can’t against fadingcompletely because it can’t get full diversity, how to improve system performance inspecific channel environment is a significant issue.For further improving the DSTTD system performance, SSD technology iscombined. By doing constellation rotation on modulating signal and interlacing I/Qcomponents to achieve high diversity order. With increase of system capacity thecomplexity of detecting algorithm which has a close association with systemperformance becomes high.The thesis studied MIMO model and its capacity based on wireless fading channelmodels and MIMO theories, analysed and simulated zero forcing algorithm and MMSEdecoding algorithm in DSTTD system.In order to future improve diversity gain with independent identically distributedchannel, the thesis studied SSD-DSTTD system with linear detection, analysed systemmodel, decoding algorithm and detection algorithm. Transmited system transmittingmodel to single antenna model using linear space-time decoding algorithm.The receiverjointed vector Gaussian approximation algorithm and scalar Gaussian approximationalgorithm with channel decoding to iterative demodulation based on the idea of softinterference cancellation. The theory analysis illustrated MMSE algorithm had betterperformance than zero forcing algorithm, vector Gaussian approximation algorithm hadbetter performance than scalar Gaussian approximation algorithm. Through simulatingand analyzing different algorithms, they all had2dB performance improvementcompared with DSTTD system.Iterative detecting is a effective method to realize high speed and effectivetransmission，more spectrum efficiency，against fading and interference. Thanks to the enlighten of BICM-ID, the SSD-DSTTD system jointed space-time and error correctiondecoding to perform a iterative loop using the idea of soft interference cancellation. Thealgorithm has a good performance against fading and approaches Gaussian performance.Simulation results illustrated the iterative algorithm is better than linear algorithmwithout much increment of complexity.When linear space-time decoding with linear detection, SSD-DSTTD system cannot pass all information on to demodulator,which cause losses on performance. Thethesis proposed a SSD-DSTTD system jointed with space-time decoding. The systemcombined space-time decoding and demodulating with error correction decoding to toperform a iterative loop using the idea of soft interference cancellation. The algorithmhas a good performance against fading and approaches Gaussian performance underindependent identically distributed channel. Simulation results illustrated the iterativealgorithm has much better improvements than linear algorithm, and has a certainincrease in complexity within a limit.