Analogue orthogonal precoding using reduced-complexity transceivers

Orthogonal transmission toward N undesired receivers via conventional digital beamforming techniques requires at minimum (N + 1) active transmit antennas. As the radio frequency (RF) complexity increases linearly with the number of active antennas, orthogonal transmit precoding becomes impractical for simple user terminals. The paper proposes an alternative solution utilizing a single-radio reactance-assisted antenna system, featuring low-power consumption, low cost and ease of fabrication. The orthogonal precoding technique to be proposed emulates classical digital orthogonal precoding for suppressing the interference toward a number of users, but at highly reduced RF complexity.