MobiSteer: Using Steerable Beam Directional Antenna for Vehicular Network Access

In this work, we investigate the use of directional anten-
nas and beam steering techniques to improve performance
of 802.11 links in the context of communication between a
moving vehicle and roadside APs. To this end, we develop
a framework called MobiSteer that provides practical ap-
proaches to perform beam steering. MobiSteer can operate
in two modes { cached mode { where it uses prior radio
survey data collected during idle” drives, and online mode,
where it uses probing. The goal is to select the best AP and
beam combination at each point along the drive given the
available information, so that the throughput can be maxi-
mized. For the cached mode, an optimal algorithm for AP
and beam selection is developed that factors in all overheads.
We provide extensive experimental results using a com-
mercially available eight element phased-array antenna. In
the experiments, we use controlled scenarios with our own
APs, in two di erent multipath environments, as well as in
situ scenarios, where we use APs already deployed in an ur-
ban region { to demonstrate the performance advantage of
using MobiSteer over using an equivalent omni-directional
antenna. We show that MobiSteer improves the connec-
tivity duration as well as PHY-layer data rate due to bet-
ter SNR provisioning. In particular, MobiSteer improves
the throughput in the controlled experiments by a factor of
2 { 4. In in situ experiments, it improves the connectivity
duration by more than a factor of 2 and average SNR by
about 15 dB.