mbols M = Mo increases. The case where each radio transmitter uses a random address sequence is essentially the spread-spectrum example where each transmitter uses the FH/MFSK waveform with diversity of degree m. The only difference here that we have L radios simultaneously transmitting at all times in the same M-ary sub-band of total bandwidth WMA. The examples here assume that each chip energy detection output is hard quantized. Certainly, more infor- mation is maintained for making decisions if the chip energy detector out- puts are quantized into more levels. Another possibility is to form an ordered list of the chip energy detector outputs and use it for making decisions. One could then account for the differences in received signal strengths from dif- ferent radios. Weaker signals will consistently fall lower on the list. Creighton [116] has examined the use of list detectors with various metrics for this SSMA system. The address sequence is essentially the simplest repeat m coding. With more powerful codes we can achieve somewhat better performance. Greater DECODER ENERGY DETECTOR QUANTIZER ENERGY DETECTOR QUANTIZER DECODER FREQUENCY DEHOPPER ENERGY DETECTOR QUANTIZER DECODER f-M-1 Figure 2.26. Independent decoders. Multiple Access improvements, however, can be achieved by changing detectors and metrics, and taking advantage of side information in the decoding process. The system proposed by Goodman et al. [117] certainly is not as efficient as pure FDMA. However, it allows random access with no overall control. With low duty cycle users this means many users can access a single receiv- ing radio terminal with no overall control other than hop synchronization. To make this system more efficient Haskell [122] and Timor [124], [125] have proposed schemes that make use of information derived while decoding the messages of other users to reduce interference of a given transmitted radio signal. For the same example above with 209 simultaneous users Timor's scheme achieves 450 users. In the next section we exami