Performance Analysis of a Multiple Antenna Concatenated DMT-FMT Scheme in the Uplink

In this paper we analyze a recently proposed concatenated multitone system for application in the asynchronous multiple access channel (wireless uplink). We study the robustness of the scheme to the users´ time offsets, carrier frequency offsets, and channel time/frequency selectivity. A comparison with multiuser OFDM and MC-CDMA is reported which shows that increased robustness and better performance can be achieved with the proposed scheme. It is based on the concatenation of an inner filtered multitone (FMT) modulator with transmission over multiple antennas, and an outer space-time cyclically prefixed discrete multitone (ST-CP-DMT) modulator. The inner modulator is used to efficiently realize frequency division multiplexing of the users by partitioning the FMT sub-channels among them. The outer modulator copes with the residual sub-channel intersymbol interference and it further implements a form of transmit diversity. Frequency and space diversity is exploited via direct sequence (DS) data spreading across the DMT tones