Space-time adaptive processing and subband array implementations

Abstract

Inter-symbol interference (ISI) and co-channel interference (CCI) are two major sources to signal impairment in mobile communications. To suppress both ISI and CCI, space-time adaptive processing (STAP) systems are shown to be effective, leading to increased capacity and improved quality of service. The high complexity and slow convergence, however, are often the hurdles in practical implementation of the STAP systems. Several subband array implementations have been proposed for STAP over the past few years. These methods are to provide optimal or sub-optimal steady state performance with reduced implementation complexity and improved convergence performance. The purpose of this paper is to investigate the steady state performance of subband arrays with different decimation rates and to derive analytical expressions of the minimum mean square error (MMSE). The discrete Fourier transform (DFT) based subband arrays and both unconstrained and constrained weight adaptations are considered.