Relay selection and resource allocation in adaptive beamforming-based I2V communication system

Abstract

Recently, as the wireless communication technologies grow fast, the need for wireless vehicular communication on the road has been increased as well. In particular, several wireless technologies, such as the IEEE 802.11p or the IEEE 802.16j standard, have been suggested to support vehicular communications. Nevertheless, both poor channel environment caused by the propagation loss, fading effect, or high speed of the vehicle and interference from other communication links can make the received signal power below a certain threshold value where the reliable transmission can be guaranteed. In addition, omni-directional transmission in conventional system uses its resources inefficiently. Meanwhile, adaptive beamforming technology has several advantages compared to the omni-directional transmission of conventional system, such as spatial diversity, interference migitation, and adaptibility, which is suitable for infrastructure-to-vehicle communication system. Moreover, multi-hop relaying can improve system performance by transmitting data through relays which have relatively good channel conditions. In this thesis, we focus on the infrastructure-to-vehicle communication system which exploits the advantage of both multi-hop relaying and adaptive beamforming technology. In the system we consider, the received power can be increased at the vehicle due to directional gain of adaptive beamforming technology. Specifically, to maximize the sum end-to-end capacity of vehicles, we propose two relay selection and resource allocation schemes; optimization and heuristic schemes. Since the optimization scheme has too high computational complexity resulted from lots of possible combinations of relay assignment to find optimal relays in real time, we propose a heuristic scheme that efficiently finds appropriate relays and allocates resources for the selected relays with low computational complexity by considering the interference among vehicles. By using the heuristic scheme, t...