Analysis of incoherent pre-RAKE TDD/DPSK/CDMA wireless portable communications

Abstract

Incoherent direct-sequence spread-spectrum code-division multiple-access (CDMA) with differential phase-shift keying (DPSK) modulation is a promising approach for wireless portable communications. The pre-RAKE system is also attracting attention for wireless portable communication in time division duplex applications due to achieving the same multipath diversity of the RAKE receiver but using an ordinary matched filter receiver at the portable unit. In this paper, we study the pre-RAKE system with DPSK modulation for multi-user communications in a Rayleigh fading channel. The system performance is analyzed in a generalized Rayleigh fading multipath channel. Two diversity-combining techniques, namely, maximal ratio combing (MRC), equal gain combing (EGG) and zero forcing equalization (ZFE) are considered Both diversity types are supplemented by selection diversity for the strongest paths in gain. We also consider the effect of imperfect channel estimation on the system performance and compare the results with the case of coherent QPSK pre-RAKE system.