Research On Key Problems In MIMO-based Wireless Sensor Networks

Wireless sensor networks(WSN) are composed of thousands of low-cost, low-power consuption nodes which are with the capacity of sensing,computing and wireless communication.The new type of networks promises many new application areas,such as military defence,entironmental monitoring,space exploration,medical treatment,intelligent home and anti-terrorism.Therefore,the research on WSN is one of the hotspots.Since the sensor nodes are battery driven and it is impractical to recharge the battery for so many nodes after deployment,energy efficiency has been a key concern in the research work of WSN.Multiple-input Multiple-output(MIMO) technique refers to using multiple antennas in transmitting and receiving end.MIMO technique could improve spatial multiplexing gain by exploring the spatial resource sufficiently.So MIMO system could increase the system capacity by times under the same spectral resource and transmit power budget.It is the key technique in the next generationg mobile communication system.Integrating MIMO technique with space-time coding and taking advantage of spatial and time coding could achieve spatial diversity and temporal diversity.Consequently this could decrease bit error rate and improve system stability without increasing the transmitting power.Using MIMO technique in WSN could make use of the diversity gain to increase the receiver signal intensity and overcome the channel fading.MIMO technique in WSN also provides multiplexing gain to support higher data rate and improve energy-efficiency.The MIMO-based WSN could save node's transmitting power, maintain network connectivity,lengthen the networks' lift time.Therefore,the research on the MIMO-based WSN has received more attention recently.By studing the characters of WSN and MIMO respectively,this paper focuses on the research of some key questions in MIMO-based WSN and proposes the resolutions relatively.Main contributions of this paper include:â‘ Propose a novel organizing method for MIMO-based WSNDirect application of multiantenna techniques to sensor networks is impractical due to the limited physical size of a sensor node which typically can only support a single antenna.So when using MIMO technique in WSN,individual single-antenna nodes to cooperate on information transmission and/or reception,a cooperative MIMO system can be constructed such that energy-efficient MIMO schemes can be deployed.This paper researchs how to choose the cooperative nodes based on the remaining energy and location to constitute virtual antenna array.This paper also analizes the networks energy consumption model.â‘¡Propose a novel routing protocol for MIMO-based WSNIn order to save the transmitting energy,the routing protocol for MIMO-based WSN not only just finds the next relay node,but also considers the cooperative nodes' energy consumption.This paper studies these characters of MIMO-based WSN,and proposes a new distributing energy-efficient routing protocol which is suitable for those characters.The simulation results indicate that this protocol can obviously reduce the network energy consumption,enhance the energy validity,lengthens the sensor networks lifespan.â‘¢Propose a novel MAC protocol for MIMO-based WSNIn order to solve the problems that the process of accessing channel is complex and pronely causes collisions in MIMO-based WSN,a heterogeneous WSN models and a centralized TDMA scheduling algorithm based on the networks models are proposed in this paper.The scheduling algorithm based on the model first colors the nodes with considering the special nodes' degree of conflict nodes,then decides the scheduling priority according to the product of node's packet number and the hop to the base station.The simulations show that the algorithm could effectively avoid conflict,raises utilization rate of slot and has better performance in terms of latency, throughput and suitability for the MIMO-based WSN.