Adaptive subband arrays for multipath fading mitigation

In high-speed digital mobile communications, intersymbol interference (ISI) due to multipath fading and co-channel interference (CCI) are two significant problems that decrease the communication quality and limit the communication capacity. Adaptive array alone or together with temporal equalizations or diversity techniques are promising methods to suppress both the ISI and CCI. We propose an adaptive subband array with DFT filter banks for multipath fading mitigation in land mobile communications. The purpose is to improve the convergence of the desired signal equalization as well as to effectively suppress the interferers. A DFT filter bank transforms the received time-domain data into the frequency domain, and as such yield a multiple narrowband signal processing problem. The transformed signal has a higher signal correlation in each frequency subband due to the reduction in bandwidth. Note that the increase of signal correlation by the suband technique is blind in the sense that it does not require any information of the arrival signals. With increased coherence, the effect of multipath fading associated with both the desired and the interference signals, can be greatly reduced.