Evolutionary Game Based Strategy Selection for Hybrid V2V Communications

Vehicle-to-vehicle (V2V) communications is an important technology in vehicular ad hoc network (VANET) to support autonomous data exchange among vehicles. Multiple V2V communications modes have been investigated for VANET, including dedicated short-range communications (DSRC) based on IEEE 802.11p and LTE-V2X, which are suitable for different packet transmission cases. In order to fully exploit the strengths of various modes, hybrid V2V communications strategies are designed in this paper, where each vehicle is allowed to choose different modes for different kinds of transmissions in separate frequency bands for transmission throughput improvement. Furthermore, since it is usually impractical to decide all the vehicles’ communications strategies globally due to high computational complexity and heavy overhead to broadcast the decisions, we model the selection of hybrid V2V communications strategies for vehicles as an evolutionary game. A strategy selection algorithm is then proposed, where each vehicle can select its hybrid V2V communications strategy locally based on its evaluation of the payoffs for different strategies and limited signalling from the base station. Simulation results demonstrate that the proposed algorithm can converge to an asymptotic stable state, which can improve the transmission throughput of vehicles, and is robust to the slight evaluation errors of payoffs and the strategy mutations of a few vehicles.

I. Introduction

Vehicular ad hoc network (VANET) is a promising technology for data exchange on the road, where traffic related information can be exchanged for traffic management, and entertainment-related data can be transmitted to improve user experiences [1]. In VANETs, vehicles are allowed to transmit signals autonomously to other vehicles in broadcasting, multicasting or unicasting manner, referred to as vehicle-to-vehicle (V2V) communications [2]. Moreover, the basic awareness messages should be periodically broadcast by vehicles including position, speed, etc. [3]. Currently, multiple modes and heterogeneous vehicular network have been investigated for V2V communications, including dedicated short-range communications (DSRC) based on IEEE 802.11p and LTE-V2X [4]–[8]. In DSRC, a vehicle could transmit packets in a dedicated frequency band if the channel is sensed idle for a specific period and when the packet transmission collides with other vehicles’ transmissions, the vehicle should wait for a random backoff interval before re-transmission, as specified by the carrier sense multiple access with collision avoidance (CSMA/CA) protocol [5]. In LTE-V2X, time-frequency resources are structured as that in LTE and can be allocated to different vehicles for V2V communications by a base station globally or by vehicles locally. Particularly, in LTE-V2X mode 4, vehicles use the sensing-based semi-persistent scheduling (SPS) scheme to select and reserve resource blocks (RBs) for packet transmissions locally, which facilitates reducing vehicles’ reliance on base station (BS) [3]. Hence, LTE-V2X mode 4 is a promising mode in LTE-V2X to support V2V safety applications which cannot completely depend on the coverage availability and the scheduling of BS [6]. The performance of DSRC and LTE-V2X mode 4 has been analysed in [3], which is highly related to the vehicle density, transceiver-receiver distance and packet generation patterns. It was illustrated in [3] that there is no absolute superiority between those two modes.