A vacation-based performance analysis of an energy-efficient motorway vehicular communication system

Due to the unprecedented growth in bandwidth requirement, the increasing number of access points (APs) deployed within a macrocell for services such as video conferencing, video gaming, and data off-loading leads to significantly higher energy consumption. This advancement in mobile networks has forced researchers to explore various methods of energy saving, although with little emphasis on motorway vehicular networks where mobility is also an important aspect. Energy saving in these networks is extremely challenging due to the dynamic nature of the environment in which they operate. To analyze such a network, we first develop a performance model for a medium access control (MAC) protocol, namely, the modified version of packet reservation multiple access (M-PRMA) with wireless channel impairments in a motorway vehicular environment. The M-PRMA protocol provides communication links (time slots) between an AP and the vehicles in range. The time slots of the M-PRMA protocol are modeled as servers where each outage of the channel is represented as a server on queue-length-independent vacation. Then, each AP, in a hierarchical micro-macro topology, is modeled as a single-server queue where the AP takes queue-length-dependent vacations (switches to sleep mode) to save energy during its inactivity period, although at the expense of degraded quality of service (QoS). To address this, a number of sleep strategies for the AP are studied. Finally, both of these proposed models (M-PRMA with channel impairments and AP with sleep cycles) are analyzed and verified through simulations. The performance results reveal that the introduction of sleep strategies at an AP can save up to 80% transmission energy during off-peak hours and 66% on average during the day in a motorway vehicular environment while supporting end-to-end QoS for video and audio conferencing applications.