Repeater-assisted capacity enhancement (RACE) for LOS MIMO point-to-multipoint links

We present here an exploration of enabling MIMO spatial multiplexing in a long range LOS point-to-multipoint link such as might be found in a ground-to-air sensor network backhaul or LOS cellular configuration. The paper focuses on the capacity between a single multi-antenna sensor and an airborne multi-antenna transceiver, facilitated by an airborne single-antenna repeater. The multi-point aspect is treated by showing the regions on the ground where any multiple-antenna sensor in those regions could receive high capacity service. This repeater-assisted capacity enhancement (RACE) technique yields a capacity improvement of approximately a factor of two relative to the configuration without the repeater. A large geographical area may be serviced by proper design of system parameters. In the sensor network backhaul configuration, this capacity improvement may enable higher fidelity sensor fusion algorithms than currently possible because of link limitations. In the cellular configuration or any multi-user communication system, this technique may enable data-intensive applications that would otherwise be unavailable because of data rate constraints. To aid the reader in understanding the analysis, a separable metric for capacity is developed, which allows us to consider the impact of the TX/RX configurations separately. This metric may be helpful for other analyses where the RACE concept is found to be useful.