Improved signal design for bandwidth efficient multiple access

The problem of optimizing signals for the Gaussian multiple access channel under a quality of service (QoS) constraint is addressed. In particular, the bandwidth efficient multiple access (BEMA) approach (Varanasi, M.K. and Guess, T., IEEE Trans. Commun., vol.49,no.5, p.844-54, 2001) is considered, wherein signals are designed at the base station and fed back to, and for use by, uplink transmitters, in order to minimize a strict bandwidth while ensuring that each user meets a rate-specified QoS constraint. A new recursive, greedy algorithm for signal design is proposed that exactly meets the QoS requirements. Preliminary analysis and numerical examples suggest it is optimal.