A Multiple User Opportunistic Scheme: The Grassmannian Approach

Scheduling in a broadcast (BC) channel based on partial channel state information at the transmitter (CSIT) is carried out in an opportunistic way. In an orthogonal approach, the number of generated beams would be equal to the available base station antennas, but this paper presents a scheme where more beams are generated. The novel scheme follows the Grassmannian line packing approach to guarantee the largest orthogonality among the generated beams. Each of the selected users performs an interference mitigation that partially cancels the multiuser interference terms that arise in this multiplexing scenario. Analytical expressions are derived for the novel scheme and the superior performance of this approach is also demonstrated via simulations for an outdoor wireless scenario. Beside achieving larger system sum rate, we show that this proposal also provides a lower system delay