MIMO Spatial Mode Adaptation at the Cell Edge Using Interferer Spatial Correlation

In conventional MIMO cellular systems, the spatial transmission mode, e.g. spatial multiplexing or transmit diversity, is chosen independently in each cell. Unfortunately, the optimum transmission mode for users that are interference limited depends to a large extent on the transmission mode used by interfering base stations. This paper proposes interference-aware link adaptation where base stations exchange their transmission plans with neighboring base stations and broadcast this information to the active users. Each user measures its long term susceptibility to spatial interference and returns this information to the base station via a spatial mode table. The base stations then schedule active users according to the decisions made in interfering base stations and the preferred transmission strategies of its own users. Simulations illustrate the ergodic sum rate the performance of switching between spatial multiplexing and statistical beamforming in different spatially correlated channels.