TAILIEUCHUNG - Space-Time Coding phần 8

Các hoạt động mã hóa được mô phỏng như một thời gian rời rạc quá trình Markov hữu hạn nhà nước. Quá trình này có thể được đại diện đồ họa bởi sơ đồ nhà nước và lưới mắt cáo. Đối với các ct đầu vào, quá trình Markov hữu hạn nhà nước tạo ra một vt đầu ra | LST Receivers 209 assuming EIR symbol estimation and uncorrelated decoder outputs. If LLRs are used there is a bias between symbol estimates. However the bias effect is less relevant in the iterative MMSE receiver than in the iterative PIC receiver since the MMSE detector performs interference suppression as well as cancellation. Thus the use of DSC in iterative MMSE receivers is less effective than for iterative PIC receivers. Comparison of the Iterative MMSE and the Iterative PIC-DSC Receiver In this section we compare the performance of the iterative MMSE receiver and the iterative PIC-DSC receiver. It is demonstrated that the PIC-DSC receiver is able to achieve similar performance as the MMSE-STD and even outperform MMSE-STD in a high interference environment. The direct implementation of the iterative MMSE receiver based on matrix inversion has complexity which is polynomial in the number of transmit antennas 36 . Furthermore the iterative MMSE filter coefficients need to be recalculated for each symbol in iterations k 1 as well as from iteration to iteration. The complexity performance trade-off of the iterative PIC-DSC is therefore significantly better than that of the iterative MMSE receiver. However for slow fading channels it is possible to implement adaptive MMSE receivers with the complexity being linear in the number of transmit antennas. Figure FER performance of a HLSTC with nT 8 nR 2 R 1 2 iterative MMSE and iterative PIC-DSC receivers BPSK modulation on a slow Rayleigh fading channel 210 Layered Space-Time Codes We demonstrate the performance of an HLST scheme with separate R 1 2 4-state convolutional component encoders the frame size of L 206 symbols BPSK modulation and MAP decoding. The channel is modelled as a frequency flat slow Rayleigh fading channel. The results are shown in the form of the frame error rate FER versus Eb N0. Figure compares the iterative MMSE and iterative PIC-DSC performance for an 8 2 HLSTC. The results .

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