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Please use this identifier to cite or link to this item: http://hdl.handle.net/123456789/8822

Title: Capacity and diversity gains of mimo systems in correlated rician fading channels
Authors: Ali, Adel Ahmad
Qaseem, Syed Mohammad Tabish
Keywords: Diversity gains
Mimo system
Wireless system
Channel fading
Multiple antennas
Symbol error rate
Issue Date: 2005
Abstract: Multiple input multiple output (MIMO) systems using multiple transmit and receive antennas are widely recognized as the vital breakthrough that will allow future wireless systems to achieve higher data rates with limited bandwidth and power resources, provided the propagation medium is rich scattering or Rayleigh fading and the fades are independent and identically distributed. On the other hand, traditionally, multiple antennas have been used to increase diversity to combat channel fading. Hence, a MIMO system can provide two types of gains: spatial multiplexing or capacity gain and diversity gain. However, the capacity and diversity benefits of MIMO systems depend strongly on what kind of fading the channels undergo; whether the fades associated with different transmit and receive antennas are correlated; and whether the channel state information (CSI) is available at the transmitter. This thesis presents the progress we have made towards determining the capacity and diversity benefits of multiple antennas under different assumptions about the underlying channel. Here, in this thesis slow and frequency nonselective MIMO systems in correlated Rician fading environment are assumed. Symbol error rate (SER) expression for M-ary phase shift keying (MPSK) modulation for MIMO systems is obtained. The correlated MIMO Rician fading channel matrix is proposed and the combined effect of Rician factor (K) and correlated fading parameter (r) on the capacity and diversity gains of MIMO Rician fading channels is investigated. For m × m MIMO systems, the combined gain in the SNR in dB due to K factor and correlated fading parameter (r) in terms of their individual gains in the SNR in dB at any given fixed capacity is presented in mathematical forms. These mathematical expressions give a good estimate of the combined gains in the SNR (dB) to within 1 dB. We also found that relative capacity gains when CSI is available at the transmitter are more at higher values of K and r i.e., the improvement in capacity when CSI is available at the transmitter is more at higher values of K and r. The correlation increases the SER, thus reducing the diversity order of the system. MIMO systems with higher values of K are more affected by correlated fading. The improvement due to K factor in correlated fading reduces with the increase in the diversity order D. Also we found that the MIMO system with 4th order diversity having r = 0.7 gives better performance than the system with 6th order diversity having r = 0.9, which implies that if there is insufficient space for placing the antennas (which is the cause of correlated fading); the decision for choosing the number of antennas should be taken carefully.
Description: This study has been conducted & submitted to the Deanship of Graduate studies in partial fulfillment of the requirements for the degree of Master of Science in Electrical Engineering June 2005.
URI: http://hdl.handle.net/123456789/8822
Appears in Collections:College of Engineering

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