Signal acquisition and tracking with adaptive arrays in the digital mobile radio system IS-54 with flat fading

The author considers the dynamic performance of adaptive arrays in wireless communication systems. With an adaptive array, the signals received by multiple antennas are weighted and combined to suppress interference and combat desired signal fading. In these systems, the weight adaptation algorithm must acquire and track the weights even with rapid fading. The author considers the performance of the least-mean-square (LMS) and direct matrix inversion (DMI) algorithms in the North American digital mobile radio system IS-54. He shows that implementation of these algorithms permits the use of coherent detection, which improves performance by 1 dB over differential detection. Results for two base station antennas with flat Rayleigh fading show that the LMS algorithm has large tracking loss for vehicle speeds above 20 mph, but the DMI algorithm can acquire and track the weights to combat desired signal fading at vehicle speeds up to 60 mph with less than 0.2 dB degradation from ideal performance with differential detection. Similarly, interference is also suppressed with performance gains over maximal ratio combining within 0.5 dB of the predicted ideal gain