Browsing by Author "Hailu, Gebremariam"

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    Analysis and Evaluation of Diversity-Multiplexing Tradeoff for Multiple-Antenna systems in Ultra Wideband (UWB-MAS) and Rake Receiver
    (Addis Ababa University, 2012-07) Hailu, Gebremariam; Mokuria, Getahun (PhD)
    Ultra wide-band (UWB) systems have recently attracted much research interest owing to their appealing features in short-range wireless communications. These features include high data rates, low power consumption, multiple access communications, and precise positioning capabilities.On the other hand, multiple antenna systems (MAS) and space-time coding (STC) techniques, such as space time block coding (STBC) are well known for their great potential to play a significant role in the design of the next-generation broadband wireless communications. Multiple-Input Multiple-Output (MIMO) system extends the link reliability (spatial diversity (SD)) and increase throughput,(spatial multiplexing (SM)).However, there is a fundamental tradeoff(DMT) between how much of each type of gain in any coding scheme can extract. In this thesis the approach for multi-antenna system is to obtain tradeoff between SD and SM gains for UWB technology. Atheoretical analysis is conducted to enlighten the DMTfor UWB-MAS (UWB-MISO/SIMO) and therefore; performance enhancements provided by the proposed scheme compared to the classic single link scheme is evaluatedat finite signal-to-noise ratios (SNRs).The tradeoff curves provide a characterization of achievable SD and SM for a given space-time code at SNR’s encountered in practice. A Rake receiver is employed that captures energy from sequences transmitted from N transmit antennas at M receive antennas in a subset of the resolvable multipath components. Exact diversity gain expressions are determined for orthogonal space–time block codes (OSTBC). It is shown that the asymptotical diversity gain has an infinite valueeven with single-antenna systems and the multi-antenna techniques can be very beneficial in the practical range of signal-to-noise ratios. Comparisons are also provided with DMT results in the literature and found thatcodes that are not optimal over the Rayleigh fading channels are also not optimal over the UWB channels. Key words: DM, DMT, Finite signal-to-noise ratio (SNR), MAS, OSTBC, outage probability, SM, UWB.