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|Title: ||Capacity and diversity gains of mimo systems in correlated rician fading channels|
|Authors: ||Ali, Adel Ahmad|
Qaseem, Syed Mohammad Tabish
|Keywords: ||Diversity gains|
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
|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.|
|Appears in Collections:||College of Engineering|
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