Transmission Strategy And Performance Analysis Of Buffer-aided Relay System For Wireless Body Area Network

At present,Wireless Body Area Network(WBAN)is more and more widely used,which can not only provide continuous body monitoring for patients,but also provi de diagnostic medical data for doctors.WBAN is a short-range communication network centered on the human body.It consists of personal terminals,networking equipment,sensors within a certain distance around the human body,sensors worn on the surface of the human body,and even sensors implanted inside the human body.WBAN is generally deployed on the human body,so it will face new and higher requirements in terms of highly reliable data transmission,miniaturization of equipment,and low-power design.Especially for implanted WBAN,the in-body sensor nodes are often energy constrained,so it is a surgical risk to replace their batteries,and the human body acts as a communication medium,which makes the channel more complex and signal attenuation more severe.Furthermore,the conventional relay cooperative WBAN system uses a fixed schedule to receive and transmit data without considering the channel quality,so the system performance is always limited by the bottleneck link.In order to solve the above problems,this thesis analyzes the transmission strategies and performance of the bufferaided relaying implanted WBAN.The main work and results are as follows:(1)In order to improve the reliability of data transmission,a buffer-aided relay system for implanted WBAN is proposed,in which the relay node is equipped with a data buffer.By using Gauss-Hermite quadrature method and linear-approximation method,the closedform expressions of the average bit error rate(BER)and average delay for two link selection protocols are derived over the human lognormal fading channel,and the correctness of the theoretical analysis is verified by simulation modeling.The theoretical and simulation results show that,compared with the conventional single-relay WBAN,the two link selection protocols(namely Protocol 1 and Protocol 2)adopted in this thesis can enable the relay to use the optimal channel for data transmission,so they can break through the limitation of bottleneck link and achieve significant BER performance advantages.In addition,under the same parameters,although protocol 2 has higher delay than protocol 1,the BER performance of protocol 2 is significantly better than that of protocol 1.Results reveal that,the BER performance of the Protocol 2 is independent of the buffer size,and through giving a small buffer size the Protocol 2 can achieve lower power consumption at the cost of a slight delay.(2)In order to solve the problem of energy limitation and high reliability transmission,on the basis of the above,this thesis further proposes a buffer-aided relay system based on wireless energy transmission.Wireless energy supply can solve the energy shortage of the source node and the buffer-aided relay can flexibly utilize the optimal channel,taking about the above advantages,a transmission strategy for wireless energy and information transmission about this system is designed,and the BER and average delay are analyzed.By deriving the BER and average delay expressions and discussing related parameters,a trade-off scheme of BER and average delay is finally obtained.The results show that the proposed system achieves good BER performance with a slight delay while the implanted source node continuously obtains energy.