Please use this identifier to cite or link to this item: http://scholarbank.nus.edu.sg/handle/10635/22856
Title: Performance analysis of diversity wireless systems
Authors: CAO LE
Keywords: MIMO, ARQ, MSE, CSI, Capacity, Outage
Issue Date: 6-Aug-2010
Source: CAO LE (2010-08-06). Performance analysis of diversity wireless systems. ScholarBank@NUS Repository.
Abstract: Many wireless communication systems make use of the diversity technique: a well-known concept to combat the effects of multipath fading. Diversity reception consists of receiving redundantly the same information-bearing signal over multiple fading channels, (then combining them at the receiver so as to increase the received signal-to-noise ratio (SNR).) One way by which these multiple replicas can be obtained is using multiple antennas in multiple-input-multiple-output (MIMO) systems for achieving space diversity. The ergodic capacity is a key performance parameter of a MIMO fading channel. We obtain tight bounds on the ergodic capacity over an identical MIMO fading channel, which show explicitly the dependency of the ergodic capacity on the SNR and the number of transmit and receive antennas. The results enable us to determine the optimal number of transmit antennas to be used for a given SNR and a given total number of antennas. Recently, MIMO systems over a non-identical fading channel have attracted great attention because of their applications in cooperative communications and distributed antenna systems. We derive explicit and closed-form expressions of the ergodic mutual information (MI) and the information outage probability. Two simple and near-optimal power-allocation schemes are then proposed for maximizing the ergodic MI and minimizing the information outage, respectively. Another approach to obtain multiple replicas of the same information-bearing signal is by using multiple time slots separated by at least the coherence time of the channel in automatic-repeat-request (ARQ) systems, leading to the exploitation of time diversity. With imperfect channel state information at the receiver (CSIR), the performance parameters of ARQ systems are evaluated as a function of the accuracy of the channel estimation. A link between data-link-layer performances and physical-layer parameters is therefore established. An attempt is made to study the inter-relationships among the various relevant system performance parameters and the dependency of these relationships on the CSIR accuracy. For enhancing the throughput, adaptive transmission strategies have been adopted to match the transmission rate to time-varying channel conditions for achieving higher spectral efficiency. Therefore, with regard to maximizing the throughput, in addition to providing a more reliable transmission, ARQ schemes with adaptive transmissions are extensively adopted. Considering a practical case with the imperfect channel state information at the transmitter (CSIT) and the imperfect CSIR, an optimal continuous-rate adaptation scheme is studied so as to achieve a maximum goodput.
URI: http://scholarbank.nus.edu.sg/handle/10635/22856
Appears in Collections:Ph.D Theses (Open)

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