**2.4. WSN vs. MANET**

240 Wireless Sensor Networks – Technology and Protocols

network.

space and 4500 bytes available code space

techniques used for energy scavenging.

information about the occurring events.

global positioning system GPS.

**2.3. Routing protocols in WSN** 

processing unit of a smart dust mote prototype is a 4 MHz Atmel AVR8535 microcontroller with 8 KB instruction flash memory, 512 bytes RAM and 512 bytes EEPROM [24]. TinyOS operating system is used on this processor, which has 3500 bytes OS code

*Radio transceiver*: The radio transceiver unit is responsible for connecting the node to the

 *Power supply unit*: One of the most important components of a sensor node is the power unit. Since the sensor nodes are often inaccessible, power is considered a scarce resource and the lifetime of a sensor network depends on the lifetime of the power resources of the nodes. Power is also a scarce resource due to the size limitations. For instance, the total stored energy in a smart dust mote is of the order of 1 J [25]. It is possible to extend the lifetime of the sensor networks by energy scavenging [26], which means extracting energy from the environment. Solar cells are an example for the

 *Localization Systems; e.g. GPS(Global Positioning System):* Most of the sensor network routing techniques and sensing tasks require the knowledge of location with high accuracy. Thus, it is common that a sensor node has a location finding system like the

 *Data centric Routing*: Data-centric routing protocols have an architecture in which there is a sink that communicates with certain regions to collect data from the sensors located in the selected regions [27]. An example of such protocols is SPIN (Sensor Protocols for Information via Negotiation) [28] which is the first data-centric protocol that considers data negotiation between nodes in order to eliminate redundant data and save energy. Another famous example is Directed Diffusion [29]. In this protocol data is diffused through sensor nodes by using a naming scheme for the data. An enhanced version of Directed Diffusion is Rumor routing [30] that routes the queries to the nodes that have observed a particular event rather than flooding the entire network to retrieve

 *Hierarchical Routing*: Hierarchical routing attempts to efficiently maintain the energy consumption of sensor nodes by involving them in multi-hop communication within a particular cluster. Data is then aggregated and fused in order to decrease the number of transmitted messages to the sink[27]. LEACH (Low Energy Adaptive Clustering Hierarchy) [31] is one of the first hierarchical routing approaches for sensors networks in which clusters of the sensor nodes are formed based on the received signal strength. The cluster-heads are then used as routers to the sink. This will save energy since the transmissions will only be done by such cluster heads rather than all the sensor nodes. Other protocols are mainly inspired by this protocol, such as TEEN (Threshold sensitive Energy Efficient sensor Network protocol) [32] that is designed to be responsive to

sudden changes in the sensed attributes such as temperature.

WSN is a kind of ad hoc network. From an abstract network view point, WSN is similar in most of the aspects to ad hoc networks. However, WSN is very special compared to other types of ad hoc network due to the following [12,34]:


consideration in WSN compared to other types of ad hoc network in the sense that WSN when deployed it is mainly focused on how to satisfy the environmental conditions.

 *Application specifications*: While normal ad hoc networks can be usually thought as general purpose networks, the whole WSN is built to serve a specific application. Therefore, WSN must satisfy the application requirements in addition to the environment conditions. This complicates the issue of finding general purpose solutions for many aspects in WSN.
