Abstract: Wireless sensor network is a distributed sensor network and it consists of a large number of tiny, portable devices called sensor nodes. Wireless sensor network has attracted many researchers because of its infrastructure less nature. It has emerged as promising technology in wireless communication field. Network sensor nodes are having limited energy and resources in wireless sensor network. Sensor node performs the function of collecting, processing and forwarding data to destination. Localization techniques are used to detect location or geographical placement of sensor nodes. Localization is a one of the problem in wireless sensor network. Without localization data collected in many applications is not accurate and even not useful also. In both networking and application domain of wireless sensor network localization play very significant role. In this paper various localization techniques are discussed with their requirements, area of applications and limitations
Keywords: Wireless sensor network, Practicle swarm optimization (PSO) and Binary practicle swarm optimization (BPSO), Localization.