A Survey of Localization in Wireless Sensor Network <s> Localization Algorithm in Heterogeneous Sensor Network. <s> In wireless sensor networks, node location information is critical for many applications. In this paper we propose a novel boundary node based localization scheme for location discovery in heterogeneous wireless sensor networks. We make use of a small number of high-end beacon nodes, which have more energy supply and a larger transmission range than other sensor nodes. Our scheme initially determines the locations of boundary nodes, which are nodes located in the coverage boundary of a beacon node. Other nodes then estimate their locations with the help of the boundary nodes and the beacon nodes. Simulation results show that the proposed scheme performs much better than an existing scheme in terms of the localization error and the standard deviation of the error. <s> BIB001 </s> A Survey of Localization in Wireless Sensor Network <s> Localization Algorithm in Heterogeneous Sensor Network. <s> This paper proposes a hierarchical two-step localization method for heterogeneous sensor networks. The network consists of three types of nodes: anchor nodes with known locations, a few nodes equipped with both Ultra-Wide Band (UWB) and RF radios, and a large number of sensor nodes called Lite Nodes. By using a hierarchical network architecture and UWB technology, only a small number of anchor nodes are needed. The localization method works in two steps. First, UWB nodes estimate their locations by using the built-in high-precision distance measurement and locations of anchor nodes. Next, Lite Nodes use UWB nodes as references to estimate their locations. The performance of iterative and non-iterative localization methods are compared. It is observed through simulations that iterative method produces much smaller localization error. The effects of UWB node placement and other parameters such as measurement noise, number of anchor nodes, and communication ranges on the resulting localization error are also presented. <s> BIB002 </s> A Survey of Localization in Wireless Sensor Network <s> Localization Algorithm in Heterogeneous Sensor Network. <s> In this paper we investigate the impact of a Relay Node (RN) placement plan on a heterogeneous wireless network called Hybrid Wireless Network with dedicated delay nodes (HWN*) in terms of system capacity, transmission delay and Quality of Service (QoS). A novel HWN* Heuristic RN Placement (HHRP) algorithm, which considers RN assistance & support for radio resource sharing such as inter-network traffic balancing, TD/CDMA soft handover, routing and user mobility has been implemented. A system level simulation is used to quantify the benefits of HWN* using HHRP algorithm over HWN* with other RN placement plans and multi-hop cellular networks. I. INTRODUCTION A heterogeneous wireless network refers to a wireless net- work that is comprised of wireless nodes with different radio access technologies or equipment with different operating systems. For example, it can be a wireless sensor network including bluetooth based radio access and zigbee 802.15.4 based radio access or a hybrid wireless network including cellular access and 802.11b/g based radio access. Specifi- cally for a hybrid wireless network, the increase of cellular communication intensity results in a reduction in cell size, thus much denser clusters are required resulting in increased infrastructure cost and system complexity. Meanwhile, the bursty nature of communication traffic and path loss results in traffic prediction difficulty. A solution must be found to provide effective resource management, congestion control and routing. The hybrid wireless network which incorporates cellular and MANET interfaced RELAY nodes, provides a practical approach for this. Nevertheless, the dedicated relay infrastructure approach can be also be adapted to the emerging wireless sensor network in order to maintain node connectivity, support sensor data aggregation and optimise power consump- tion. <s> BIB003 </s> A Survey of Localization in Wireless Sensor Network <s> Localization Algorithm in Heterogeneous Sensor Network. <s> Location estimation and tracking for mobile stations have attracted a significant amount of attention in recent years. Different types of signal sources are considered available to provide measurement inputs for location estimation and tracking in heterogeneous wireless networks. Various techniques have been studied and combined for location tracking, e.g., the least square methods for location estimation associated with the Kalman filters for location tracking. In this paper, the hybrid unified Kalman tracking (HUKT) technique is proposed to provide an integrated algorithm for precise location tracking based on both time of arrival (TOA) and time difference of arrival (TDOA) measurements. A new variable is incorporated as an additional state within the Kalman filtering formulation to consider the nonlinear behavior in the measurement update process. The relationship between this new variable and the desired location estimate is applied in the state update process of the Kalman filter. Three different designs of hybrid factor are proposed to adaptively adjust the weighting value between the TOA and TDOA measurements. Moreover, similar concepts are also utilized in the design of unified Kalman tracking schemes for pure TOA and TDOA measurement inputs in this paper. Compared with existing schemes, numerical results illustrate that the proposed HUKT algorithm can achieve enhanced accuracy for mobile location tracking, particularly under environments with an insufficient number of measurements in one of the signal paths. <s> BIB004
Most of the localization methods for the wireless sensor networks are only to consider the homogeneous network. The different kinds of the nodes such as the different maximum communication radius and the different nodes own the different localization mechanisms are not considered in homogeneous, so the localization methods for the homogeneous network cannot be directly applied in the heterogeneous wireless sensor networks. Du et al. BIB001 propose a new boundary nodes localization method by using a small number of anchor nodes. First the boundary nodes are elected and their positions are determined. Then the location information of boundary nodes is sent to other nodes through a small hop communication range. Finally, other nodes estimate their locations by the hop count and hop range. The scheme uses fewer beacon nodes, but has much smaller localization error and standard deviation. This method uses fewer beacon nodes, but with a smaller location error and standard deviation. Dong et al. BIB002 proposed a two-step localization method for two-tiered hierarchical heterogeneous sensor networks. The network consists of three types of nodes: anchor nodes with known locations, a few nodes equipped with both Ultrawide Band (UWB) and RF radios, and a large number of normal sensor nodes. The localization method works in two steps: firstly the high-accurate ranging capability of UWB nodes is used to estimate their location from a few anchor nodes, then, sensor nodes estimate their locations by using UWB nodes as anchor nodes. Sometimes the distance between some nodes can be measured directly, while others cannot be. Selecting a different positioning algorithms accord to the mutual distance between nodes can be measured or not. Chiang et al. BIB004 proposed a hybrid unified Kalman tracking (HUKT) technique. The accuracy of tracking is based on both time of arrival (TOA) and time difference of arrival (TDOA) measurements. This method is proposed to adaptively adjust the weighting value between the TOA and TDOA measurements. The scheme can both provide higher localization accuracy for mobile network and adapt to environments with insufficient signal sources. According to the different communication radius of the nodes, some super nodes can be deployed at some areas with plenty communication demands to transmit the information. Shen and Pesch BIB003 considered the nodes with more power and longer communication range as the heterogeneous nodes and propose a heuristic relay positioning algorithm for heterogeneous wireless sensor networks, to achieve the sharing of resources in heterogeneous wireless sensor network by using the relay nodes.