Beamfocusing outperforms airy beams for overcoming antenna blockage
Beamfocusing Versus Airy Beams: Does Antenna Blockage Require Beam Bending?
Information Theory
Summary
Sometimes signals sent by antennas get blocked by obstacles, which can make it hard for devices to receive them well. Some people thought that special signals called Airy beams, which can bend around obstacles, might help fix this. But the authors show that just focusing the signal straight at the receiver works best for single-antenna devices, even if parts of the antenna are blocked or the signal has errors. For larger receivers with many antennas, changing the beam can help but it still doesn’t need to bend like an Airy beam.
What this means in practice
- •For wireless communication engineers: Design antenna systems focusing beams directly on receivers to optimize signal strength even with obstacles blocking parts of the antenna array.
- •For satellite communication designers: Adjust beam patterns for larger multi-antenna receivers to illuminate unblocked parts without needing Airy beam bending techniques.
Authors
Emil Björnson, Vitaly Petrov, Erik G. Larsson
Abstract
Airy beams are often proposed in array beamforming to bend beams around obstacles. We prove that, for a single-antenna receiver, conventional beamfocusing maximizes the received power regardless of how many antennas are blocked and, in expectation, even with phase errors in the channel state information. This also holds for multi-antenna receivers under a phase-separability condition that is satisfied in rank-one channels. Numerical results confirm that unmodified beamfocusing is optimal for physically small receivers (i.e., those that fit within the beamwidth) when an obstacle is present. For physically larger receivers, the optimal precoding deviates from beamfocusing to better illuminate the receiver's unobstructed parts, but will not become Airy beams. While Airy beams can be configured to perform well, their ability to follow a bent trajectory in front of an obstacle does not maximize the received power behind it.