Iterative decoding bounds for multiuser multilevel FSK

Abstract

In this work we study joint multiuser detection using factor graphs for an N frequency T user noisy multiple access channel. This channel may model a frequency hopped code division multiple access system. The system is separated in two parts: multiuser detector and a code. We present a factor graph for the multiuser detector and obtain from it extrinsic information transfer (EXIT) curves. Paired with the EXIT curves of low density parity check and repeat accumulate codes, we obtain values for the signal to noise ratio (SNR) that bound the systempsilas performance. The EXIT curves for the codes are presented from the detectors perspective. The results show that rates close to the sum capacity are achievable.