The Research On Power Control And Scheduling Algorithms For Energy-efficient Design In Wireless Body Area Network

Wireless Body Area Network(WBAN)can provide patients with low-cost,continuous and accurate medical care,and it has become a new trend in the field of telemedicine,intensive care and other areas in recent years.In consideration of human safety and energy constraints of the component,energy-efficient design is critical in the design of WBAN.The energy consumption of nodes is divided into three parts: data acquisition,processing and transmission,in which transmission energy consumption accounts for the largest proportion.Power control and scheduling algorithm as the two key means to reduce transmission energy consumption,their research have theoretical and practical significance.At present,main problems of power control and scheduling algorithms in WBAN are:(1)The existing power control algorithms are based on a predefined function between the link quality and the transmission power,which simplifies the relationship between the two variables and thus has a large computational mistake.(2)The parameter Received Signal Strength Indicator(RSSI)characterizing the link quality is too susceptible to environmental factors.(3)Existing scheduling algorithms are measured only by the network lifetime as the parameter,without taking into account the transmission rate of nodes under specific applications and the network fairness requirements.In this paper,power control and scheduling algorithms are optimized.The feedback control is used in the power control,different transmission requirements of the sensor nodes are considered in the scheduling algorithm.Specifically as follows:(1)A feedback power control algorithm based on Proportional,Integral and Differential(PID)algorithm is proposed.The algorithm uses a mean value of Link Quality Indicator(LQI)to reflect the link quality.By the PID algorithm,the power adjustment is obtained as the output and the difference between the mean LQI and the LQI threshold of nodes is taken as the input.Experimental results show that,on the premise of gaining 97.6% packet reception rate,the average energy consumption of the algorithm is reduced by 17.3mw and 13.7mw respectively,the average network lifetime is increased by 28.7% and 23.4% as compare to traditional methods like Multiplicative Increase Additive Decrease(MIAD)and Dynamic Postural Position Inference(DPPI).(2)A centralized scheduling algorithm including the fairness parameter is proposed.At the beginning of the time slot,the Sink node selects which node to transmit according to the link quality of each node.The problem is modeled as a Markov Decision Process with fairness constraint and the optimal scheduling strategy is obtained by using value iteration.Experimental results show that a reasonable choice of fairness threshold can extend the network lifetime and the proposed algorithm prolongs the lifetime of the network compared with traditional algorithms.(3)A distributed scheduling algorithm is proposed in order to solve the problem that the centralized scheduling is very expensive in energy and difficult to expand.The algorithm adds the fairness parameter to the energy efficiency index of Dynamic Protocol for Lifetime Maximization(DPLM).Each node calculates the energy efficiency index according to its own current link quality and calculates the back-off time according to its relationship with the efficiency index.Experimental results show that,compared with the DPLM algorithm,the proposed algorithm can allocate the transmission time slot reasonably while guaranteeing the network lifetime,thus satisfies the different requirements of data transmission.