Ladas & Parry
Code-division-multiple-access-system based on M-ary pulse-position modulated direct-sequence
 A BPSK-MPP-DS-CDMA system is devised using a pulse position modulated direct sequence technique. Under the same bandwidth, same energy used for one decision, and same bit error rate conditions, if the number of users is less than the period N.sub.cp of the pseudorandom sequence signal PN.sub.p.sup.i (t) used in the BPSK-MPP-DS-CDMA system, the multiple access capacities of the binary (M=2), ternary (M=3), quaternary (M=4), and pentary (M=5) BPSK-MPP-DS-CDMA systems according to the present invention are respectively at least 2, 5.34, 13.28, and 26.4 times greater than that of the conventional BPSK-DS-CDMA systems. On the other hand, if the number of users attains N.sub.cp, the multiple access capacity can not increase any more, however, the bit error rate of the system will be reduced. Furthermore, (M-1)/M transmitting energy is saved. 
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Chen-Yi
Chang