 signals using DS/BPSK waveforms that have low time cross-correlations [63]-[76]. For FH/MFSK waveforms, Reed-Solomon codewords have been proposed [77]-[82] as hopping sequences that yield low time cross-correlation. Signals with the same form as spread-spectrum signals discussed in ear- lier chapters but designed to have low time cross-correlation require the use of specific chip sequences to be assigned to radios. When these are used to divide the available channel capacity we refer to this as code division multiple access (CDMA). We distinguish³ this CDMA technique from SSMA where in SSMA we assume the chip sequences are statistically inde- pendent when regarded as random processes. That is, for SSMA we assume pseudorandom sequences are well modelled as i.i.d. sequences and differ- ent keys result in independent pseudorandom sequences. The SSMA sys- tem thus uses spread-spectrum signals that are uncorrelated in the statistical sense where the expectation of the time cross-correlation of any two signals is zero. We define CDMA signals as those designed to have low time cross-correlations where the signals are not statistically independent. Generally, CDMA signals with sequences of long periods behave like SSMA signals [65]. Superscript(3)To our knowledge this distinction between CDMA and SSMA has not been used before. Summary of Multiple Access Techniques Another common way to divide up the total radio channel capacity is to use time-division multiple access (TDMA) [57]. Here time is divided into disjoint slots where any two radios communicate using assigned time slots. This can be done with signals that occupy the entire signal bandwidth or with each sub-band of an FDMA system. In principle, TDMA is equivalent to FDMA with time rather than fre- quency being the primary variable that is divided into segments. In practice, however, TDMA systems are more flexible than FDMA systems. TDMA sys- tems require some means of maintaining a common time reference among all radios, which usually means that some network cont