MobiSteer

Abstract

In this work, we investigate the use of directional antennas 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 approaches 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 maximized. 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 commercially available eight element phased-array antenna. In the experiments, we use controlled scenarios with our own APs, in two different multipath environments, as well as in situ scenarios, where we use APs already deployed in an urban region -to demonstrate the performance advantage of using MobiSteer over using an equivalent omni-directional antenna. We show that MobiSteer improves the connectivity duration as well as PHY-layer data rate due to better 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.

RoadGate: Mobility-Centric Roadside Units Deployment for Vehicular Networks

“…Drive-thru Internet [3] was first introduced in the paper, which shows that a vehicle moving with the velocity of 180 km/h can access internet data via a roadside AP. Refrences [4, 5] confirm the feasibility of WiFi-based vehicular Internet access for noninteractive applications. Cabernet [6] aims to deliver data to and from moving vehicles by using WiFi access points.…”

iBUS: An Integrated Beamformer and Uplink Scheduler for OFDMA Small Cells

“…The remaining constraints are all conservation constraints indicating the following: 1) assignment of a single beam per frame; 2) net allocation of subchannels being limited to in a frame; and 3) assignment of one contiguous set of subchannels to a user in a frame, respectively. 3 We now show that it is hard to even obtain a polynomial-time approximation scheme (PTAS) for the ISP problem. Specifically, we have the following result.…”

“…2 (see uplink). The resulting SNR for each user with each beam is measured directly at the BS 3 In the uplink, LTE uses single-carrier frequency-division multiple access (SC-FDMA) due to its lower peak-to-average-power ratio (PAPR) than OFDMA [2]. With SC-FDMA, the clients are constrained to be allocated only contiguous subcarriers, which is explicitly captured by our formulation.…”

Region-Based Efficient Beam Handover Scheme in IEEE 802.11 Wireless Networks

“…This sequence of messages can be divided into three types: probe, authentication, and association. As described in [2], the probing delay constitutes the biggest part (over 90%) of the handover latency. Moreover, in case of AP with directional antenna, it has higher probability of long handover latency compared to the normal AP with omni-directional antenna.…”

“…However, using a dynamic beam steering scheme has a key problem when processing a handover between access points (APs) [2,3]. That is, the new AP does not know where to allocate its beam towards the moving node.…”