Investigating the energy consumption of a wireless network interface in an ad hoc networking environment

Energy-aware design and evaluation of network protocols re- quires knowledge of the energy consumption behavior of actual wireless interfaces. But little practical information is available about the energy consumption behavior of well-known wireless network interfaces and de- vice specifications do not provide information in a form that is helpful to protocol developers. This paper describes a series of experiments which ob- tained detailed measurements of the energy consumption of an IEEE 802.11 wireless network interface operating in an ad hoc networking environment. The data is presented as a collection of linear equations for calculating the energy consumed in sending, receiving and discarding broadcast and point- to-point data packets of various sizes. Some implications for protocol design and evaluation in ad hoc networks are discussed. Keywords—energy consumption, IEEE 802.11, ad hoc networks I. INTRODUCTION Because mobile devices are dependent on battery power, it is important to minimize their energy consumption. The energy consumption of the network interface can be significant, espe- cially for smaller devices. Most research in energy conserva- tion strategies has targeted wireless networks that are structured around base stations and centralized servers, which do not have the limitations associated with small, portable devices. By contrast, an ad hoc network is a group of mobile, wireless hosts which cooperatively form a network independently of any fixed infrastructure. The multi-hop routing problem in ad hoc networks has been widely studied in terms of bandwidth utiliza- tion, but energy consumption has received less attention. It is sometimes (incorrectly) assumed that bandwidth utilization and energy consumption are roughly synonymous. Recently, there has been some study of energy-aware ad hoc routing protocols, particularly for distributed sensor networks. In this context, en- ergy is often treated as an abstract "commodity" for purposes of minimizing cost or maximizing time to network partition. We believe that energy-aware design and evaluation of net- work protocols for the ad hoc networking environment requires practical knowledge of the energy consumption behavior of ac- tual wireless devices. In addition, it is important to present this information in a form that is useful to protocol developers: the total energy costs associated with a packet containing some number of bytes of data. Device specifications, which indicate the current draw while transmitting and receiving, are somewhat unhelpful in this respect. This paper describes a series of experiments which obtained detailed measurements of the energy consumption of a Lucent WaveLAN IEEE 802.11 wireless network interface operating in ad hoc mode. The data is presented as a collection of linear equations for calculating the energy consumed in sending, re-