Adaptive or steered beam downlink antennas are known for capacity enhancement of cellular communication systems. A space division multiple access (SDMA) system may use a plurality of individually steered beams within a sector of a cell of a cellular system for communicating simultaneously with a selected plurality of user equipments (UEs), such as cellular phones, in successive timeslots. However, random scheduling of which user equipment to serve in any one timeslot does not maximise system performance because beam overlaps, which cause interference, occur when a base station is communicating with a plurality of UEs subtending a small angle of divergence at the antenna. To improve system performance, and minimise interference, the steered beams need to be kept separated, i.e. to have a minimum overlap. This means that scheduling of which UEs to serve in any one timeslot needs to be carefully tailored, such that all users are served, but in groups of well-spaced members. Searching through the UEs to find a best group, then a second best group, and so on, leaves final selections of UEs that form very poor groups that degrade overall system performance. For example, with a steered beam 10 as shown in FIG. 1, the best choice, which is chosen first, is at the peak of the beam, with UEs 11, 12, 13 separated by 20°. As subsequent choices are made which seek to maintain the 20° separation, the last choice 14, 15, 16 almost inevitably includes two UEs 14, close together close to a border of the sector with an adjoining sector. Similarly, with a fixed multi-beam 20 as shown in FIG. 2, the best choice, 21, 22, 23, which will be chosen first, will be of UEs at the peaks of the multi-beam 20, which are therefore well separated in angle of arrival. However, as a consequence, a last selection will inevitably include user equipments 24, 25, 26 that are at cusps of the multi-beam. However, any alternative approach of searching through all possible groupings to find optimal groups is at present too slow for practical implementation.
USPTO Backgrounds
USPTO Backgrounds