|M.Sc Student||Gidony David|
|Subject||Adjacent Channel Interference Cancellation for MSK-Type and|
QPSK Signals Using Antenna Diversity
|Department||Department of Electrical Engineering||Supervisor||Mr. Yitzhak Kalet|
This work addresses the problem of adjacent channel interference (ACI) (and co-channel interference-CCI) between constant envelope MSK-type and QPSK signals, in a slow flat Rayleigh fading channel. The communication system considered, consists of M transmitters each transmitting an independent MSK-type signal, in a FDM system, operating over independent slow flat Rayleigh fading channels in the presence of AWGN. One of the signals is identified as the desired signal and the other signals are classified as the interferers. Each signal transmits independent uncoded data bits, which are assumed to be time synchronized.
Because the baseband modulating pulses have infinite bandwidth, this fact will introduce ACI, resulting in degradation in performance of the desired signal.The proposed receiver, whose goal is reduce the effect of above mentioned interference, contains N receiving antennas with a single processor. Each receiving antenna contains an array of M sub-receivers, each sub-receiver coherently detects one of the transmitted signals. An algorithm, based on the maximum likelihood
criterion and the properties of the received vector, is developed. This algorithm exploits the previously detected data bits for the current detection interval. The property of the multipath channel (Rayleigh channel) greatly increases the ability of the receiver to distinguish between the different transmitted signals.
The results presented show that the suggested receiver plus the proposed algorithm outperforms the classic receiver, especially for small channel spacings and large power imbalances between the desired signal and the interferers. The bit error rate results for the suggested receiver, almost coincide with the case of no ACI at
all. In other words the ACI degradation is almost eliminated, allowing very close channel spacing.