Energy Constraints of Localization Techniques in Wireless Sensor Networks (WSN): A Survey <s> Angle of Arrival (AOA) / Degree of Arrival (DOA) <s> Awareness of the physical location for each node is required by many wireless sensor network applications. The discovery of the position can be realized utilizing range measurements including received signal strength, time of arrival, time difference of arrival and angle of arrival. In this paper, we focus on localization techniques based on angle of arrival information between neighbor nodes. We propose a new localization and orientation scheme that considers beacon information multiple hops away. The scheme is derived under the assumption of noisy angle measurements. We show that the proposed method achieves very good accuracy and precision despite inaccurate angle measurements and a small number of beacons <s> BIB001 </s> Energy Constraints of Localization Techniques in Wireless Sensor Networks (WSN): A Survey <s> Angle of Arrival (AOA) / Degree of Arrival (DOA) <s> A new angle of departure (AOD) aided distributed localization approach for wireless sensor node is proposed in this paper. An L-shaped antenna array is arranged on anchor node end and the ground single antenna sensor node conduct its own line of sight AOD estimation for self-localization. Considering the limited degree of freedom provided by the anchor node can not guarantee a successful recognition to the LOS signal component in multipath environment, we adopt the minimum redundancy configuration. Via the intrinsic character of wireless channel, the maximum degree of freedom through performing two-dimension joint difference co-array operation can be obtained at sensor node end. Therefore, the sensor node can identify the LOS signal component in a very high probability with a rebuild degree of freedom increased virtual array. The validity of proposed methods are verified by numerical examples. <s> BIB002
AOA based positioning techniques involve measuring angles of the node seen by reference nodes. AOA measurement is a method for determining the direction (Degree of Arrival) of propagation of a radio-frequency wave for example of an antenna. Based on the positioning of the sensor nodes, the Degree of Arrival (DOA) of the emitting source node is estimated. With the measured angles, each sensor node is able to calculate the position of other nodes or determine the angle of the unknown node's relative position to some anchor node. Basic trigonometry relations are employed in determining the angles of source nodes to the normal (anchor node) in the network. Angle of Arrival (AOA) estimation is fundamental to many wireless sensing and communication applications, especially RF source localization. AOA is typically performed using antenna array elements that are mapped to the incident direction of the signals to a reference node. There are two advantages of using AOA, first the phase of the received signal at each node is usually more stable than the received signal strength (RSS) and secondly, for an effective AOA estimation scheme, two antenna arrays will achieve accurate node localization as compared to other range-based approaches that will require three or more sensor nodes. Generally, AOA technique provides more accurate localization result than RSSI based techniques but the cost of hardware is high in AOA. AOA is prone to effects such as multi-path effects (two or more paths of a signal arriving at a receiving antenna), shadowing, scattering and also when there is no line of sight. A distributed AOA-based localization and orientation approach for wireless sensor networks under the assumption that all unknown sensor nodes are capable of detecting angles of the incident signal from neighboring nodes is proposed in BIB001 . Other AOA localization techniques can be seen in BIB002 [18], employing L-shaped minimum redundancy linear array antennas equipped at anchor nodes and RFID Tags. This technique provides a high degree of accuracy for localization when there a clear line-of-sight between nodes in the network. The technique also requires skills and man hours in setting up the antennas to provide the required spacing for spatial diversity to accurately estimate the AOA.