Spread spectrum pulse position modulation-a simple approach for Shannon´s limit-

A spread spectrum pulse position modulation (SS-PPM) system is proposed and its basic performances are described. In many direct sequence spread spectrum (DS-SS) systems, each demodulator is desired to use an only pseudonoise (PN) matched filter for simple structure and low cost. Such systems as on-off keying (SS-OOK) or differential phase-shift keying (SS-DPSK) systems have been conventionally used. The present authors propose the spread spectrum pulse position modulation (SS-PPM) system as one of such systems, and show that the SS-PPM system has the following advantages: (1) higher data rate (about 4 times higher than the other conventional SS systems under the same bandwidth and the same code length), (2) superior performance of bit error rate (BER) to the other systems (BER characteristics of the SS-PPM system improves with increasing the number of chip slot of the SS-PPM system, and it approaches Shannon´s limit). Furthermore they evaluate asynchronous CDMA performance of the SS-PPM system by theory and computer simulation