Zhonghai Wang

A Novel Semidistributed Localization Via Multinode TOA–DOA Fusion

This paper presents a 2-D semi-distributed localization technique, which is based on the fusion of the positioning data estimated by multiple mobile nodes. The fusion is implemented in the local coordinate of one of the nodes (reference node) and improves the positioning performance of the desired node in the coordinate of the reference node. This paper introduces the proposed localization fusion technique. The fusion weights and positioning error are theoretically derived, and the efficiency of a suboptimal reference node selection method, the positioning error, and the position update rate are evaluated via simulations.

A Novel Implementation of DOA Estimation for Node Localization on Software Defined Radios: Achieving High Performance with Low Complexity

This paper introduces a novel implementation of direction-of-arrival (DOA) estimation for localization of nodes in (mobile) ad-hoc networks. The localization technique is being implemented on a software defined radio (SDR) system. The SDR system needs DOA estimation for: (a) beam-forming and detection, and (b) localization. The detection process needs coarse DOA estimation, while the localization needs a fine one. The technique fuses two known DOA estimation techniques: delay-and-sum and root-MUSIC. The former is a simple technique suitable for on-line (high speed) implementation required for detection. Hence, it would consume less power. The latter is a complex technique that needs higher processing time and consumes more power and would be suitable for off-line DOA estimation. Hence, the fused DOA estimation technique offers high performance with low complexity and power consumption.

Omnidirectional Mobile NLOS Identification and Localization via Multiple Cooperative Nodes

This paper presents an Omnidirectional mobile target-node (TN) localization technique in nonline-of-sight (NLOS) scenarios. Here, a TN cooperates with base-nodes (BNs) with antenna-arrays to allow them to find its position via time-of-arrival (TOA) and direction-of-arrival (DOA) measurements. When line-of-sight (LOS) channel is available, each BN localizes TNs in its coverage area with reasonable accuracy. However, when LOS channel is obstructed, considerable localization error is generated. To avoid NLOS error, a technique is proposed to identify if a TN is in the LOS of multiple BNs or not. The technique enables BNs to determine and localize their shared reflection points, and to localize NLOS TNs. The paper assumes single-bounce-reflection NLOS channel between BNs and TNs. In NLOS scenarios, when three or more reflection points are shared by a TN and multiple sets of BNs, the shared reflection points are localized via DOA fusion, and then the TN is localized via TOA fusion. The equations for NLOS identification, shared reflection points determination and localization and NLOS TN localization are theoretically derived. Simulations are conducted to evaluate the proposed technique in terms of the probability of false alarm and misdetection of NLOS identification and shared reflection points determination, and NLOS TN localization accuracy.

Manet Localization via Multi-Node TOA-DOA Optimal Fusion

This paper presents a multi-node 2-Dimensional (2D) time-of-arrival (TOA) and direction-of-arrival (DOA) optimal fusion technique. This technique can be applied in ad-hoc networks, especially suitable for the application in the mobile ad-hoc networks (MANETs). In this work, positioning error in MANETs would be optimized via TOA-DOA joint estimation and fusion across multiple nodes. In the proposed MANET, we assume two categories of nodes: Those equipped with antenna arrays (base-nodes) and those equipped with omni-directional antennas (target-nodes). All nodes are capable of communicating with other nodes. Base-nodes are capable of positioning (TOA-DOA estimation) other nodes located in their coverage area. A fusion method is proposed to minimize the mean square of the positioning error of a target-node, when more than one base-node estimates its position. The fusion scheme is derived theoretically and compared with simulation results. This paper depicts the capability of the proposed 2D fusion algorithm to considerably reduce the positioning error. The proposed technique has important applications in GPS-denied environments

Comparison of Semidistributed Multinode TOA-DOA Fusion Localization and GPS-Aided TOA (DOA) Fusion Localization for MANETs

This paper evaluates the performance of a semidistributed multinode time-of-arrival (TOA) and direction-of-arrival (DOA) fusion localization technique in terms of localization circular error probability (CEP). The localization technique is applicable in mobile ad hoc networks (MANETs) when global positioning system (GPS) is not available (GPS denied environments). The localization CEP of the technique is derived theoretically and verified via simulations. In addition, we theoretically derive the localization CEP of GPS-aided TOA fusion and GPS-aided DOA fusion techniques, which are also applicable in MANETs. Finally, we compare these three localization techniques theoretically and via simulations. The comparison confirms that in moderate scale MANETs, the multinode TOA-DOA fusion localization technique achieves the best performance; while in large scale MANETs, GPS-aided TOA fusion leads to the best performance.

Non-line-of-sight identification via phase difference statistics across two-antenna elements

This study proposes and investigates the performance of a new non-line-of-sight (NLOS) identification technique for multiple antenna systems that is based on the phase difference across two antenna elements. In order to avoid any confusion in the position location process, NLOS identification techniques should be implemented in the localisation systems. A phase wrapping selection algorithm is proposed to calculate the phase difference variance across two-antenna elements. A theoretical relationship is maintained between the phase difference variance and the Rician K-factor. The proposed K estimator requires an uncorrelated phase across antenna elements. The validity of this assumption is verified via channel modelling simulations. Then, a hypothesis test on the K-factor is formed to identify NLOS situations. The prior distributions of K-factor under line-of-sight (LOS) and NLOS conditions, and the K-factor threshold that are used to distinguish LOS and NLOS situation are derived. The impact of shadowing on the performance of the proposed NLOS identification method is studied. The performance of the proposed phase difference K estimator technique is compared with the envelope-based K estimator.

A New Multi-Antenna Based LOS - NLOS Separation Technique

This paper introduces a line-of-sight (LOS) and non-LOS (NLOS) separation technique based on the statistics of the phase difference of two received signals. The phase difference is achieved via a co-installed synchronized two-receiver system. The variance of the phase difference is used to separate LOS and NLOS. The probability-density-function (PDF) of the received signal phase generated by NLOS component is theoretically derived. The variance of the phase difference is calculated using the derived PDF numerically and verified via simulations. The LOS and NLOS separation performance versus signal power ratio of LOS to NLOS is evaluated via simulations.

A new TOA-DOA node localization for mobile ad-hoc networks: Achieving high performance and low complexity

This paper proposes a novel approach for node localization with applications in mobile ad-hoc networks. The network consists of base nodes and target nodes. Base nodes equipped with antenna arrays are capable of localizing target nodes independently via integrated time-of-arrival (TOA) and direction-of-arrival (DOA) estimation. In addition, base nodes cooperate to improve the localization accuracy by fusing the estimated target node positions. Kalman filter is integrated with the fusion to further improve the localization performance. The proposed technique is compared to a localization technique based on extended Kalman filter (EKF), which directly fuses the multiple measured TOA-DOA. The comparison criteria include localization accuracy in terms of error cumulative distribution function (CDF) and approximate posterior Cramer Rao lower bound (APCRLB), filter stability and computational complexity. The comparison confirms that the proposed method involves minor computational complexity, while it demonstrates slightly larger PCRLB; however, compared to EKF its stability is higher. This makes it a good candidate for localizing multiple target nodes in mobile ad-hoc networks.

A Novel Semi-Distributed Cooperative Localization Technique for MANET: Achieving High Performance

This paper introduces a semi-distributed cooperative localization technique realized via multi-node time-of-arrival (TOA) and direction-of-arrival (DOA) optimal fusion: Each base-node estimates the position of target-nodes by joint TOA- DOA evaluation, and then, the target-node position estimation error is minimized by TOA-DOA optimal fusion across multiple base-nodes. The performance of the proposed technique is studied and compared to two GPS-based positioning techniques, i.e., GPS-aided TOA fusion and GPS-aided DOA fusion. The circular error probability (CEP) is derived theoretically and verified via simulations. The results confirm the superiority of the proposed localization technique in moderate scale mobile ad- hoc networks (MANETs) compared to the two GPS-based fusion schemes. Thus, while the proposed technique is applicable to MANETs in GPS-denied environments, it is also suitable for GPS available environments. Finally, compared to the centralized scheme, the positioning updating rate of the semi-distributed technique is higher and its power consumption in the reference base node is considerably lower.