ADAPTIVE INTERFERENCE CANCELLATION FOR FAST FADING CHANNEL

One of the big problems in wireless communication channels is the multipath fading. Almost all environments suffer for this multipath which is caused when the receiver receive more than one signal path because of diffraction, reflection, shadowing and scattering. Each path has different properties which cause more complexity in the receiver end to recover the transmitted signal especially in the
case of fast fading channel when we have fast varying time domain. In a typical orthogonal frequency division multiplexing (OFDM) broadband wireless communication system, a guard interval and cyclic prefix are inserted to decrease the effecting of inter-symbol interference and the inter-carrier interference. The superimposed training sequence is one of the technical methods used to increase
the transmission efficiency and decreases the effect of inter-symbol interference (ISI). The superimposed training sequence is the random data added the transmitted frame and it is stored in the receiver for channel estimation and equalization process.  In this thesis, the superimposed training sequence STS will be imposed on OFDM system. The superimposed training system (STS) is done by two methods: the first one is an algebraic sum of training sequence with the OFDM transmitted frame and the second one uses matrix concatenate in the transmitter to add the training sequence with OFDM frame and using the adaptive equalizer in the receiver to improve the received signal . Two types of equalizers are used in our simulation which are; the LMS and the RLS equalizers and the results of two equalizers were compared between them. The STS with RLS equalizer gives minimum bit error rate (BER) and better system stability and performance compared to LMS equalizer. The modulation schemas which are in the communication system are; (BPSK, QPSK and 16 QAM). The