Efficient Zero-Forcing Based Interference Coordination for MISO Networks

We consider coordination of transmission strategies in interference networks, where multiple antennas at the transmitters can be used to adjust the spatial signature of the transmitted signal. For single antenna receivers the interference power received can be constraint by so-called interference temperatures, which can be used to coordinate the amount of interference in the network. We recapitulate recent research results on this topic and discuss methods to select interference temperatures that lead to performance gains compared to uncoordinated transmission. A special configuration is to demand interference to be completely eliminated, so-called zero-forcing. Methods based on zero-forcing allow for simple computation of the transmit strategies, while for general temperatures iterative algorithms are required. Strictly enforcing completely orthogonalized transmission drastically reduces the number of active users in the network and is therefore too restrictive for larger networks. We suggest an efficient algorithm that enforces orthogonal transmission only in part, which leads to an increased number of users and significant performance gains, while maintaining the low complex computation of the transmit strategies. The method is based on successive user allocation, that avoids an exhaustive search for the active user set and the user transmitter pairs for which interference should be eliminated.