  A Wireless Sensor Network (WSN) consists of spatially distributed autonomous
sensors to monitor physical or environmental conditions, such as temperature,
sound, pressure,etc. In sensing applications, data packets are flowing from
sensor nodes to base station. In data collection processes, bottom up approach
is used. In bottom up approach, all nodes send their sensed data packets to
base station directly. In this approach will lead to increased delay, which
will lead to higher energy consumption. To reduce the energy consumption of
sensor nodes,Clustering Algorithm and Low-Energy Adaptive Clustering Hierarchy
(LEACH) are being used. Efficient gathering in Wireless Sensor information
systems, Power Efficient Gathering in Sensor Information System (PEGASIS) is
being used. There are lot of research issues in Wireless Sensor Networks such
as delay, lifetime of network, energy dissipation which needs to be resolved.
