Joint TDOA And AOA Localization Algorithm For Wireless Senor Network

Wireless Sensor Networks is the adaptive network system which is consists of many low cost,small volumes,low power consumption sensor nodes.As a new type of sensor technology,wireless sensor network has very broad application prospects,is often used in military,industrial production,farming and animal husbandry production,intelligent transportation,smart home,and many other fields.Traditional sensor network,usually using GPS devices to obtain the node location parameters,the method virtually increased the system cost and cannot assure high precision of node location parameter,therefore needs a new node localization method to solve the problems of the existing system,which make the wireless sensor network technology onto the stage.Wireless sensor network localization technology,as the name implies,it is a node location method with the aid of wireless sensor network,through the communication between sensor nodes,with the help of the specific localization algorithm,realize the precise location of the target node.This paper introduces the basic concepts of wireless sensor network localization technology and the operation process of it,explains emphatically in the localization algorithms which are widely used in the existing system,put forwards four kinds of problems existing in the current localization algorithm.(1)The problem of needs the location information of anchor nodes from the very beginning.In the traditional wireless sensor network localization system,the location information of anchor nodes are often known,this greatly limits the scope of the system can apply,at the same time,it redu ces the stability of the system.For this,a anchor self-localization algorithm is proposed in this paper,from use the anchor nodes which have the small antenna array and known the location information,to complete the location of other anchor nodes.(2)The problem of the clock anchor nodes not synchronized.One of the biggest factors which limit the positioning accuracy of the time-difference-of-arrival(TDOA)localization algorithm is the clock of anchor nodes are not synchronized.The calculate TDOA information will deviate from the real TDOA information for the unsynchronized problem.This will lead the impairment of the location system performance.For this,the clock synchronization compensation algorithm is proposed in this paper,with the aid of anchor nodes easy to achieve the line-of-sight communication with each other,this feature estimated the clock offset and the clock skew of anchor nodes based on the time-of-arrival information of the anchor node communication and finally compensation the calculate TDOA information to solve the clock unsynchronized problem.(3)The non line-of-sight(NLOS)communication between Sensor nodes.The non line-of-sight communication means the line-of-sight communication line is blocked due to the obstacles.The non line-of-sight communication between nodes will cause the time-of-arrival(TOA)information from tag node which is recorded by anchor nodes exists a big error,affect the system location performance.For this,the non line-of-sight identification algorithm is proposed in this paper,with the aid of anchor nodes easy to achieve the line-of-sight communication with each other and the TOA information of broadcast signals at anchors will take on drastic fluctuation due to the NOLS errors,this made the standard deviation of anchor-tag TDOA magnified,this algorithm use it to identify anchors at which there are NLOS error.Finally,reject the anchor nodes which have the NLOS error.(4)The problem of high algorithm complexity of TDOA location algorithm.Because of TDOA location algorithm have the higher order and nonlinear equations,so it is difficult to obtain analytical solution,it needs the help of iteration,and the iterative algorithm will leads the other problems like the power consumption of the system increases,the algorithm complexity increase,and the iterative method maybe non-converging,so we need a new location method to solve the above problems.This paper joint the TDOA and angle-of-arrival(AOA)to get a new localization algorithm,to converted the location equation from TDOA algorithm into a quadratic equation.From the quadratic equation we can get the distance between anchor nodes and tag nodes.This new algorithm the greatly reduces the system complexity and power consumption of the system.It also reduces the number of anchor nodes for location.Simulation results show that the proposed algorithm can effectively solve the four problems at present in wireless sensor network localization algorithm and improves the system location performance.