Higher Rank Interference Effect on Weak Beamforming or OSTBC Terminals

Spatial multiplexing is one of the multi-antenna techniques employed by current generation wireless systems. Based on existing research, spatial multiplexing is known to be susceptible to interference. However, it is not well known what is the effect of spatial multiplexing on other transmissions, i.e., how does user performance depend on whether a neighboring cochannel interferer applies a single (spatial) stream or a multi stream transmission. This work attempts to alleviate this shortcoming by analyzing the impact of interference rank (number of spatial streams) on a beamforming and orthogonal space-time block coded user transmission. We generalize existing analytical results on signal-to-interference-plus-noise-ratio distribution and outage probability under arbitrary number of unequal power interferers. Our results are in close form and include interference rank as a parameter, allowing for a thorough study of its impact. Analysis shows that higher rank interference causes lower outage probability, and can support higher outage threshold especially in the case of beamforming.