It is basically interested in receiving data from other sensor nodes. It can be part of the wireless sensor network or an external device such as a laptop or PDA. There is usually one base station, but depending on the application, multiple base stations are possible in a network. Sensory information is communicated to the base station via hop-by-hop wireless transmissions. The interaction patterns between the source and the sink include the following: Event detection: If a certain event occurs, the sensor nodes report the measurement of this event to the affected sinks. This is known as event detection in WSN. Periodic measurement: You need to periodically report events to the affected sinks to get the latest event data. Tracking: This feature of the wireless sensor network reports the location of an intruder observed in the network. As it can be deduced that most of the data in the sensor network will be directed towards the sink and this transmitted data will pass through many intermediate nodes before reaching the sink interested in the data. Data communication directly from node to sink will be very energy-intensive and also very expensive, so multi-hop communication is preferred in wireless sensor network. Fig1.3: Basic example of a path from node to sink