Autonomous beam coordination for the downlink of an IMT-Advanced cellular system

Cellular systems like Long Term Evolution Advanced (LTE-Advanced) aim at reusing the whole spectrum in each cell which leads to high inter-cell interference and thus low signal to interference and noise ratio (SINR) conditions for users at the cell edge. One way to utilize multiple antennas at the base station is to perform downlink transmit beamforming which besides increasing the received power at the mobile also has the potential to reduce interference when collisions of beams from different base stations are avoided. To this end we propose an autonomous coordination mechanism that allows cells to coordinate their beams in the frequency domain. In addition to increasing the SINR, it reduces interference fluctuations (the “flash light” effect) due to uncoordinated scheduling in neighbor cells thus making the interference situation more predictable. This further boosts the throughput potential. The proposed scheme is based on feedback from mobiles to their serving base station but does not require inter-cell signaling. By means of system level simulations we show that our autonomous approach converges after few iterations and yields significant cell mean and cell-edge throughput improvements.