Directional Antenna Diversity for Mobile Devices:Characterizations and Solutions

摘要

We report a first-of-its-kind realization of directional transmission for smartphone-likemobile devices using multiple passive directional antennas, supported by only one RFchain. The key is a multi-antenna system (MiDAS) and its antenna selection methods thatjudiciously select the right antenna for transmission. It is grounded by two measurementdrivenstudies regarding 1) how smartphones rotate during wireless usage in the field and2) how orientation and rotation impact the performance of directional antennas undervarious propagation environments.We implement MiDAS using the WARP platform, and evaluate it usmg acomputerized motor to rotate the prototype according to traces collected from smartphoneusers in the field. Our evaluation shows MiDAS achieves median of 3dB increase in linkgain. Combined with rate adaptation and power control, MiDAS also improves goodputand power saving. MiDAS does not require any changes to the network infrastructure,and is therefore suitable for immediate deployment.