ty, and amount of side information required. One would like to have detectors and metrics that are robust in the sense that they minimize the degradation due to the worst conditions in the channel and are not sensitive to channel parameters and do not require much side information. Multiple Access Table 2.2 Maximum number of users-P < 10-4 List-of-L* without List-of-L* with Metric Collision Compensation Collision Compensation 2.4.2 Conventional Multipoint-to-Point The point-to-point system covered in the previous section assumed all radios used independent hopping patterns and that during each hop an MFSK chip is transmitted. There the frequency hopping radios may or may not be synchronized. Now suppose L radios use FH/MFSK waveforms to simultaneously transmit data to a single radio terminal. A brute force approach to the point-to-multipoint design is to have a radio terminal with L separate receiver systems where the l-th system receives the l-th radio transmitter signal using the l-th random frequency hopping pat- tern. This means there are L frequency synthesizers at the receiving radio terminal where each one is synchronized to one of the L transmitting radios. One approach to reducing the complexity of the receiving radio's termi- nal is to require all radios to transmit synchronously such that at the receiv- ing radio terminal all transmitted radio signals hop at the same time. In addition, suppose all L radios use the same hopping pattern but with fre- quency offset SO that after dehopping (using one frequency synthesizer) the L transmitted radio signals appear in non-overlapping MFSK sub-bands. These can then be detected using a conventional FDMA receiver system. This is illustrated in Figure 2.25 where Wss is the total spread-spectrum fre- quency band and WMA is the frequency range used for the L MFSK signals in an FDMA mode. Here the multiple access band is generally much smaller than the spread-spectrum frequency band WMA W SS (2.38) and it is hopped around once every chip time Tc. Thus, we have here a