On the coding-spreading trade-off in downlink and uplink MC-CDMA systems

In this paper the trade-off between coding and spreading is investigated in the framework of a MC-CDMA system, whose physical layer parameters are derived from the wireless LAN (WLAN) HIPERLAN/2 (or IEEE 802.11a). For both downlink and uplink transmissions, the achievable bit rate is evaluated by considering several receiver structures, with code rate and spreading factor as parameters. Numerical results show that in the case of the minimum mean square error (MMSE) per-user detector with single-user soft decoder, the best code rate, for a target bit error rate, gives good performance as the spreading factor (and hence the number of users) increases. The scheme, with component blocks appropriately designed, could therefore be considered as a valid proposal for enhanced next generation WLAN.