الفهرس 
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Abstract
The wireless sensor network (WSN) is a network composed of spatially distributed sensors which communicate among themselves for detecting and recording the physical phenomenon (like temperature, sound, pollution levels, and so on ) and organizing the collected data at a central location. Due to the use of WSN in various applications, knowing the location of the object or event is one of the most important challenges in WSN, which is called the localization process. The thesis objective focuses on studying the localization in the WSNs for the range-based and the range-free. In the range-based , Received Signal Strength indicator (RSSI) and Angle of Arrival (AOA) algorithms are considered for the WSN localization process. Moreover, a proposed method based on AOA localization techniques with dynamic distance reference anchor has been presented and the problem of localization accuracy which is affected by environmental conditions is improved. The proposed algorithm is implemented into a near ground radio propagation channel of agriculture farm (short and tall grass). It is found that the proposed localization method provides the best results as compared with conventional methods. In the range-free, the most familiar range-free positioning algorithm is the algorithm of Distance Vector-Hop. It simply uses average hop distance to reflect the distance actually, but it suffers from reduced precision because it uses only network topology, instead of distances between pair of adjacent nodes. In this thesis, the classic DV-Hop, RDV-Hop, and Hybrid DV-Hop algorithms are enhanced based on the differential evolution algorithm of WSN node localization. The enhanced DE algorithm has been implemented to acquire an optimal global solution that corresponds to the estimated location of the unknown node. The results of the simulation showed clearly that the new algorithms had lower average position errors and higher accuracy than the previous ones.