lapping time intervals. However, TDMA receivers must operate at higher burst rates to achieve the same overall throughput. In addition, time synchronization must somehow be maintained among the radios in the network. Acquisition and synchronization must also be done by the receiver for each separate radio transmission burst and this reduces the overall efficiency by requiring extra overhead bits in each burst. Similar to conventional TDMA, a radio terminal in an SSMA system using DS/BPSK waveforms can simultaneously receive transmissions from several radios using a single receiver. Suppose all radios transmitting to the same receiving radio terminal use the unique key associated with this radio. Instead of transmitting in non-overlapping time intervals as in TDMA sys- items, each transmitting radio introduces a unique time shift in its DS/BPSK transmission which is a multiple of the basic chip time. At the receiving radio terminal these time-shifted DS/BPSK signals all using the same pseudoran- dom sequence appear like components of a multipath channel output with one radio transmission. If the receiving radio knows the time shifts used by the transmitting radios, then it can correlate delayed versions of the com- mon pseudorandom sequence with the received radio signal to resolve the various transmitted signals (see Section 1.6, Chapter 1, Part 2). If each coded bit consists of N° chips then correlation is done for each N° chip sequence corresponding to a coded transmitted bit of each radio Spread-Spectrum Multiple Access with DS/BPSK Waveforms transmitter. The N° chip correlator can be realized with a time-varying matched filter using a SAW device [83]-[86]. With a matched filter the var- ious transmitted DS/BPSK signals will appear as peaks of energy at the fil- ter output. The peaks are roughly two chip time in width and separated from each other by the relative delays of the radio signal shifts at the receiving radio. This is illustrated in Figure 2.8 where we show one coded bit from three radios and the tim