1. A multiple-user multiple-antenna system (MU-MAS) comprising: a plurality of base transceiver stations (BTSs) having a plurality of MU-MAS antennas for establishing multiple concurrent communication channels with a plurality of users; wherein either the BTSs and/or the wireless users measure link quality of the communication channels therebetween and use the link quality measurements to define a user cluster; the BTSs and/or the wireless users further measuring characteristics of communication channels between each user and each MU-MAS antenna within a defined user cluster and precoding data transmissions between the MU-MAS antennas within the user cluster and the users reachable by those MU-MAS antennas based on the measured channel characteristics.