Multiple inputs and multiple output channel improve the performance of wireless links by using multiple transmitters and receivers at both end. However when multiple users are added to the system number of transmitters exceed the number of receiver as result the system in overloaded condition (NtNr). A major drawback of this overloaded condition is that ML detection performs poorly and also makes the detection process more complex.
In this thesis a technique known as Hybrid Automatic Repeat Request HARQ IR has been proposed to convert this overloaded system into under loaded or critical loaded system by using the concept of virtual receive antenna and then use the simple JML or MMSE detection technique for detection. Additionally two schemes have been proposed that work well under overloaded condition. The proposed scheme allows us to use simple MUD technique without requiring any additionally hardware. Simulations demonstrate that HARQ IR result in improved BER and throughput performance.
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