Multirate/ Multiclass overlapped FFH-CDMA system : performance evaluation and cutoff rate analysis

Abstract

In this paper, a new method is proposed to achieve a multi-class multirate fast frequency hopping code division multiple access system (FFH-CDMA) based on a novel code overlapping procedure. We investigate the signalto-interference ratio (SIR) performance for such system. A channel model that allows multirate overlapped transmission is presented base on which a closed form solution for the SIR has been derived. A comparison between the exact value of the SIR and the approximated one assuming random sequences is also discussed. On the other hand, the cutoff rate for each class of users is analyzed. It is shown that for a required quality of service (QoS) guarantee, a number of active users, and a given probability of hit, the data rate for each class can be increased beyond the nominal rate imposed by the un-overlapped constraint used in classical systems.