MAI analysis for forward link mono-dimensionally spread OFDM systems

This paper deals with the average value interface between link and system level simulations for mono-dimensionally spread OFDM systems in the forward link. In particular, we investigate the intracell interference statistics for different levels of multipath channel correlation, and discuss how they impact the link-to-system level interface. We show that for low correlated channel coefficients, where the choice of the interfering spreading code has no impact on the MAI power, only one orthogonality factor can be used to determine the local mean SINR. Moreover, in this context, the MAI is shown to follow a Gaussian distribution for large spreading factor, and consequently, a unique relationship between the local mean SINR and average BER exists for all equalization strategies and system loads. For correlated channel coefficients however, one orthogonality factor per interfering spreading code is required to determine accurately the local mean SINR. In this context, the MAI Gaussian approximation is no longer valid, and high order statistical moments are required to characterize the MAI distribution. Therefore, in this context, one SINR-BER mapping per couple of equalization strategy and system load is required at the average value interface. This study is a first step in order to evaluate the capacity of forward link OFDM-CDMA systems.