**Author details**

20 Wireless Sensor Networks – Technology and Protocols

1. Layering based security approach:

the cryptographic techniques to ensure the data reliability.

Data is collected and managed at application layer therefore it is important to ensure the reliability of data. Wagner (Wanger, 2004) has presented a resilient aggregation scheme which is applicable to a cluster based network where a cluster leader acts as an aggregator in sensor networks. However this technique is applicable if the aggregating node is in the range with all the source nodes and there is no intervening aggregator between the aggregator and source nodes. To prove the validity of the aggregation, cluster leaders use

Network layer is responsible for routing of messages from node to node, node to cluster leader, cluster leaders to cluster leaders, cluster leaders to the base station and vice versa.

Data link layer does the error detection and correction, and encoding of data. Link layer is vulnerable to jamming and DoS attacks. TinySec (Karlof et al., 2004) has introduced link layer encryption which depends on a key management scheme. However, an attacker having better energy efficiency can still rage an attack. Protocols like LMAC (Hoesel et al., 2004) have better anti-jamming properties which are viable countermeasure at this layer.

The physical layer emphasizes on the transmission media between sending and receiving nodes, the data rate, signal strength, frequency types are also addressed in this layer. Ideally

The aim of this chapter is to discuss few important issues of WSNs, from the application, design and technology points of view. For designing a WSN, we need to consider different factors such as the flexibility, energy efficiency, fault tolerance, high sensing fidelity, lowcost and rapid deployment, above all the application requirements. We hope the wide range of application areas will make sensor networks an integral part of our lives in the future. However, realization of sensor networks needs to satisfy several constraints such as scalability, cost, hardware, topology change, environment and power consumption. Since these constraints are highly tight and specific for sensor networks, new wireless ad hoc networking protocols are required. To meet the requirements, many researchers are engaged in developing the technologies needed for different layers of the sensor networks

Future research on WSN will be directed towards maximizing area throughput in clustered Wireless Sensor Networks designed for temporal or spatial random process estimation, accounting for radio channel, PHY, MAC and NET protocol layers and data aggregation

FHSS frequency hopping spread spectrum is used in sensor networks.

Application layer

Network layer

Data link layer

Physical Layer

protocol stack.

**10. Conclusion & future work** 

M.A. Matin *Institut Teknologi Brunei, Brunei Darussalam* 

M.M. Islam *North South University, Dhaka, Bangladesh* 
