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An Energy Consumption Assessment Method for WIFI Large-Scale Wireless Sensor Network Based on Dynamic Channel Energy Model
Weikai Tana†, Xiaoyuan Lub, Yunxiang Xuc, Kejun Zhaod and Peng Gaoe
National Engineering Research Center for Broadband Networks & Applications,
Shanghai 200336, China
Energy efficiency is one of the most serious constraints for the deployment of large-scale wireless sensor network (WSN) significantly. However, an excellent strategy to raise energy efficient depends on a precise energy consumption assessment method. In this paper, an energy consumption assessment method based on dynamic channel energy model is proposed. Energy consumption is divided into two parts: static and dynamic. The former includes receiving, idle and clear channel assessment state, whose energy consumption is only related to a stationary working current and duration. Transmission energy consumption refers to dynamic energy consumption, function of which is described as a cubic function. The energy consumption calculation is adjusted to meet the transmission power dynamically and timely. Simulation results show that the dynamic energy consumption during transmission is summed accurately. Compared with the others, such as some simple energy models without dynamic case. It provides to support for the deployment of WIFI large-scale WSN.
Keywords: Channel Energy Model; Large-Scale Sensor Network; Energy Consumption Assessment.
1.Introduction
Recently, wireless sensor network (WSN), providing emergency monitoring, remote monitoring and environmental awareness, has been significantly interested. With the development of sensor network theory and technology, it has been widely used. Most of the applications are still limited to a small-scale wireless sensor network. However, many applications require large-scale deployment to achieve high coverage, high-precision sensing purposes, such as forest fire monitoring 1. Large-scale wireless sensor network based on WIFI has received a lot of attention 2.
In WSN, two aspects of problems we face to are the limited battery life and efficient usage of energy, which become more serious in large-scale WSN. In fact, compared to small scale applications, large-scale WSN manages a large number of nodes to achieve high coverage, which leads to greater energy consumption. Therefore, strategies, such as routing and QoS control, must be improved to raise energy efficiency3. However, the design of an excellent strategy depends on a precise energy consumption assessment method extremely. Especially, the assessment results of the impact from the varying circumstances where the sensor works. This directly affects the validity of the strategy design. In 4, authors suggest a simple energy model. The model only takes into account energy dissipation during the start-up, receive, and transmit modes. For the transmit energy it’s too simple. In 5, a radio energy dissipation model is described but it isn’t accurate enough. Various energy-efficient methods are considered in literatures but only use the simple model of energy consumption, which leads to a fuzzy simulation result and a fuzzy effectiveness of their proposed methods 6, 7. Therefore, an accurate energy consumption assessment method for WIFI large-scale wireless sensor network is proposed to provide an exact reference for the deployment of WIFI large-scale WSN.
2.Sensor Model
A sensor usually consists of the following subsystems: communication subsystem, processing subsystem and sensor subsystem. The energy consumed by communication subsystem is much higher than processing subsystem, up to 80 percent. Thus, the communication subsystem is main source of system energy consumption in WIFI large-scale sensor network 8.
Fig.1 Sensor model.
The basic structure of a sensor is shown in Fig.1. We divide the energy consumption calculation into two parts: dynamic and static. Dynamic energy consumption includes a short-circuit power that flows directly from the supply to ground during a transition at the output of a CMOS gate. Dynamic part, namely transmission circuit (TX), is composed of digital to analog converter, modulation circuit and generates emission signal. Static energy consumption is associated with maintaining the logic values of internal circuit nodes between the switching events, such as basic circuit. Static part includes: (a) basic circuit (BA) composed of voltage controlled oscillator (VCO) and frequency synthesizer, provides the power and frequency of the basic circuit; (b) transmission amplifier (PA) is signal modulation circuit to FM and launch; (c) receiving circuit (RX) is the low noise amplifier (LNA), mixer, filter, intermediate frequency amplifier and demodulation circuit, AD converter; (d) Sensor is detection of Sensor signals.
3.Proposed Dynamic Channel Energy Model
In communication subsystem, node state can be divided into four types: transmitting state, receiving state, idle state and clear channel assessment (CCA) state. They are represented by STX, SRX, SCC, SID, respectively.
We have to pass through the state of SID when switching between any two states of STX, SRX and SCC. EID, ETX, ERX and ECC are used to represent the energy consumption of each state; IID, ITX, IRX and ICC are used to represent the current of each state. From dynamic and static parts analyzed in Section Sensor Model, the total system energy consumption can be calculated as
where Estatic represents the energy consumption of those circuits whose power consumption is a constant. Estatic is calculated as
Since the energy consumption of SID only relates to the basic circuit, we get EID = EBA = PBAtID, Where PBA represents the power consumption of basic circuit is a consta...
