Packet-error probability analysis for unslotted FH-CDMA systems with error-control coding

In frequency-hopped (FH) code-division multiple-access (CDMA) systems, a number of users can transmit their packets simultaneously by using quasi-orthogonal FH patterns (codes). In applications where time is unslotted, the symbol-error probability is not the same for each symbol because the number of interfering users varies throughout the packet duration. Packet-error probability for such systems is evaluated by first enumerating all possible interference states and then averaging the packet-error probability associated with each of these states. The use of Reed-Solomon error-control coding is assumed. The computational task for this evaluation is enormous. Therefore, upper bounds and an alternate less-detailed approximate model are developed for easier computation. This approximate model generates results that are very close to those obtained using the authors´ first model (1988) for the cases in which those results are computable. The conclusions of this study confirm the observation, originally made elsewhere, that the widely used threshold-based model for other-user interference is not an accurate one