Cooperative Scheduling of Downlink Beam Transmissions in a Cellular Network

The next generation of wireless networks (e.g.,) will use multiple techniques to improve channel spectral efficiencies. In this paper we focus on one such technique, beamforming, in the downlink channel. In each sector a number of fixed beams are used to serve users. For each frame the scheduler chooses a beam and then schedules one or more mobiles that lie within that beam. Since the basestation's power is focused on a narrow beam then the served users can achieve higher rates and the sector coverage is also increased. However, this beam causes more interference in adjacent sectors. If a neighboring sector schedules a user that lies within the coverage of the beam then the achievable rate for that user will be low. The neighboring sectors must therefore schedule users outside of the beam. This requires coordination among the sectors. In this paper we assume that each sector coordinates with the sector that lies directly opposite. We provide a framework and show what information needs to be exchanged and how the schedulers in each base station uses the exchanged information to schedule users so that beam collisions are avoided. This must be done with the objectives of high spectral efficiencies and also user fairness. We compare our approach with a simple, non-coordinated approach to illustrate the advantages that coordination provides.