Energy Efficient V2X-enabled Communications

Nowadays,user terminals like smartphones are enjoying increasing popularity.More and more compute-intensive applications such as high definition video gaming and virtual reality applications are developing and coming into play in our mobile devices.However,most user terminals only have limited battery capacity due to size and space constraints,which directly affects users' quality of experience(QoE).Thus,energy efficiency(EE)has become a key performance indicator for the next generation wireless networks and attracted increasing attention from both industrial and academic communities.V2X communications allow vehicles to exchange data with other entities of the traffic system around them.With the help of V2 X communications,the information of surrounding environment,especially the information of the hidden vehicles and traffic signals,can be collected.Thus,it can enhance road safety,improve traffic efficiency,and provide rich on-board information and entertainment services.As an added benefit,the cooperative nature of V2 X communications can also be exploited to improve the energy efficiency of cellular networks.In this paper,we propose an energy-efficient relay assisted transmission scheme based on V2 X communications in the uplink cellular networks.We aim to maximize energy efficiency of the uplink while considering both the circuit power and transmit power as well as the delay constraint.The main contributions of this paper are summarized as follows.(1)To obtain the potential benefits of V2 X communications,many works have been done.The proposed V2X-enabled transmission scheme in this paper differs drastically from traditional V2 X communications schemes in the following two ways.Firstly,instead of supporting safety and entertainment services for vehicles,for the V2X-enabled transmission scheme we aim to maximize the energy efficiency of wireless networks.More importantly,in the traditional V2 X communications schemes,the related information needs to be delivered with ultra-low delay since it is closely related to the safety of involved persons.The proposed V2X-enabled transmission scheme focuses on the energy saving for delay insensitive applications.Future wireless networks are expected to support a variety of services with diverse quality of service(QoS)requirements.Some applications,such as video conferences and cloud desktop,require real-time service.Others,such as email and uploading files for sharing,are delay insensitive.Thus,it is possible to exploit the diversity of QoS requirements for different applications to save energy.(2)We propose an energy-efficient relay assisted transmission scheme based on V2 X communications in uplink cellular networks to maximize uplink energy efficiency.(3)We derive theoretical models for both direct transmission mode and V2 Xenabled transmission mode while considering both the transmit power and circuit power as well as the delay constraint.For the V2X-enabled transmission mode,we first consider the transmission without the delay constraint and obtain the corresponding optimal power allocation through sequential quasiconvex optimization algorithm.Based on the obtained result,we further propose the optimal resource allocation policy that satisfies the delay constraint and minimizes energy consumption.(4)Simulation results show that there exists an energy-delay tradeoff and the proposed V2X-enabled scheme can achieve significant energy saving with an acceptable delay compared with the traditional direct scheme,the decoding-andforward based transmission scheme,and the opportunistic store-carry and forward based transmission scheme.