Browsing by Author "Getaneh, Birlew"

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    Performance evaluation of a layered space-time structure for MIMO systems
    (Addis Ababa University, 2011-07) Getaneh, Birlew; Hailu, Ayele (PhD)
    MIMO systems are an appealing candidate for emerging fourth-generation wireless networks due to their potential to exploit space diversity for increasing conveyed throughput without wasting bandwidth and power resources. Particularly, layered space-time architecture (LST) proposed by Foschini, is a technique to achieve a significant fraction of the theoretical capacity with a reasonable implementation complexity. It is based on signal processing and conventional one dimensional coding, which includes vertical BLAST (Bell Laboratories Layered Space Time) and diagonal BLAST. BLAST accomplishes this by splitting a single user’s data stream into multiple sub-streams and using an array of transmitter antennas to simultaneously launch the parallel sub-streams. All sub-streams are transmitted in the same frequency band, so spectrum is used very efficiently. Since the user’s data is being sent in parallel over multiple antennas, the effective transmission rate is increased roughly in proportion to the number of antenna elements used. In this thesis, we focus on the performance evaluation of a layered space-time structure for MIMO systems under Rayleigh fading condition. Firstly, we throughly understand the different layered space-time architectures and investigate the performance of general V-BLAST architecture with Maximum Likelihood (ML), Zero-Forcing (ZF), Minimum Mean-Square Error (MMSE), the Successive Interference Cancellation (SIC) and the Ordered Successive Interference Cancellation (OSIC) detectors for 2 × antenna arrangement. Here, in addition to performance (BER), the different detection algorithms are evaluated in terms of computational complexity. From the results, we have seen that the maximum-likelihood (ML) detector is optimum in the sense of achieving the minimum error probability. Unfortunately, the complexity of the ML detector is exponential in the constellation size and the dimensions of the system. But, by using the SIC & OSIC detectors, we approach the performance of the ML detector with lower computational complexity. It is also shown that the average performance is improved when the number of receive antenna increases. Finallly we understand and evaluate performance bound trends of Rate Compatible Punctured Convolutional (RCPC) codes and investigate the unequal error protection capabilities of rate compatible punctured convolutional codes (RCPC codes) when used together with V-BLAST MIMO systems for a mother code rate of 1/4. The