Design and experimental evaluation of a 2.4 GHz-AoA-enhanced beamsteering algorithm for IEEE 802.11ad mm-wave WLANs

IEEE 802.11ad millimeter-wave (mm-wave) WLAN nodes achieve high throughput at the cost of the frequent re-steering requirement of highly directional antenna beams to establish and maintain links disrupted by beam misalignment, node mobility, or link blockage. Consequently, rapid and robust beamsteering algorithms are essential to enable seamless communication in mm-wave WLANs. In this paper we propose AoASteer, a beamsteering algorithm that speeds up the link establishment process in IEEE 802.11ad mm-wave WLANs by preferentially searching over a subset of mm-wave antenna sectors predicted by 2.4 GHz angle of arrival (AoA) estimation at the access point (AP). We experimentally evaluate the performance of AoASteer through extensive measurements in several indoor and outdoor locations, using 60 GHz USRP-SiversIMA packet radio transceivers to gather real mm-wave link information, and a 2.4 GHz USRP-based receiver with an 8-element uniform linear antenna array for AoA estimation, both implemented using GNU Radio. Our evaluation results, obtained for APs with different numbers of beams per sector, show that AoASteer typically selects a near-optimal LOS or NLOS link to establish communication, while significantly reducing the link establishment latency. For example, for 4-sector mm-wave antennas, AoASteer reduces the latency by 46 μs for 73% of our measurement cases compared to the IEEE 802.11ad beamsteering algorithm, while achieving the highest data rate of 6.7 Gbps for 92% of the cases.