Wireless sensor networks have many sensor devices that send their data to the sink or base station for further processing. This is called direct delivery. But this leads to heavy traffic in the network and as the nodes are limited with energy, this decreases the lifetime of the network. So data aggregation technique is introduced to improve the lifetime. This technique aggregates or merges the multiple incoming packets in to single packet and forwards it to sink. There is different data aggregation techniques based on the topology of the network.

This report clearly explains the purpose of data aggregation and gathering in WSN, data aggregation in flat networks and data aggregation in hierarchical networks, different data aggregation techniques in cluster based networks, chain based, tree based and grid based networks.

Data aggregation technique can successfully minimize the data traffic and energy consumption only when it is carried out in a secure manner. Part2 of the survey explains the possible attacks that affect data aggregation in wireless sensor network. The secure data aggregation techniques in wireless sensor networks are also discussed in this report.