PERFORMANCE OF AN INDOOR MOBILE RADIO COMMUNICATION SYSTEM USING DIRECT-SEQUENCE SPREAD SPECTRUM WITH DMSK MODULATION AND DIVERSITY

Abstract

Radio communication in an indoor mobile environment requires that the mobile units be simple in construction, low in cost, efficient in bandwidth usage and somewhat immune to multipath propagation. This presents a difficult problem. Direct-sequence spread spectrum multiple access (DS-SSMA) with differential minimum shift keying (DMSK) carrier modulation is proposed and analyzed for use in indoor mobile radio digital communication systems. An analysis for computing the bit error rate (BER) performance of the proposed system is developed. The analysis takes into account multiple order diversity that is commonly required for such systems. Performance results are numerically computed using the analysis method developed in the thesis. These results are compared with the results reported before in literature for DS-SSMA with differential phase shift keying (DPSK) carrier modulation. DPSK was found to outperform DMSK modulation. This can be attributed to higher bandwidth efficiency of DMSK. In spite of this poorer performance DMSK may be chosen because of this higher spectral efficiency and other benefits such as simplicity and better prime power efficiency of the mobile.