The management of pilot symbols in MIMO- OFDM systems by adding a feedback branch

Channel estimation techniques for Multi Input Multi Output Orthogonal Frequency Division Multiplex (MIMO-OFDM) systems based on a pilot arrangement are investigated. Training based Channel estimation with a block type pilot arrangement is studied through an algorithm for determination of efficient number of pilot symbols in an OFDM symbol by adding a feedback branch and employment of the Maximal Ratio Receiver Combining (MRRC) technique as a MIMO scheme. Channel estimation at pilot frequencies is based on the Least Square (LS) method while channel interpolation is performed by a linear interpolation. Finally, the influence of the new algorithm through three different Stanford University Interim (SUI) channel models are simulated and studied. It will be shown dramatic amount of assigned bandwidth for channel estimation can be saved for data transmission by proposed technique. Moreover, a comparison between this system and a simple OFDM system without any MIMO technique is presented. Also, the Bit Error Rate (BER) performances of both systems are indicated and compared with each other at the end.