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Routing Protocols for Wireless Sensor Networks By: Murtadha S. Al-Sabbagh Supervised By: Dr. Muhammed NajmAl-Salam
Overview • Introduction • Data Dissemination and Gathering • Routing Challenges and Issues • Routing Strategies for wireless networks • WSN routing techniques • WSN routing protocols comparison • Protocol Selection
INTRODUCTION • The main task of wireless sensor nodes is to sense and collect data from a target domain, process the data, and transmit the information back to specific sites where the underlying application resides. • Achieving this task efficiently requires the development of an energy-efficient routing protocol to set up paths between sensor nodes and the data sink.
DATA DISSEMINATION AND GATHERING • Data dissemination is a process by which data and queries for data are routed in the sensor network. • In a scope of data dissemination, a source is the node that generates the data and a node that is interested in data is called sink. • Data gathering is to transmit data that has been collected by the sensor nodes to the base station.
ROUTING CHALLENGES AND DESIGN ISSUES 1.Network Scale and Time-Varying Characteristics: • the densities of the WSNs may vary widely, ranging from very sparse to very dense. • in many applications, the sensor nodes numbering in the hundreds if not thousands, are deployed in an ad hoc and often unsupervised manner over wide coverage areas. • In these networks, the behavior of sensor nodes is dynamic and highly adaptive .
ROUTING CHALLENGES AND DESIGN ISSUES 2. Resource Constraints: • Energy is a key concern in WSNs, which must achieve a long lifetime while operating on limited battery reserves. • Also the WSN nodes have low technical specifications that must be taken into consideration when designing a WSN routing protocol.
ROUTING CHALLENGES AND DESIGN ISSUES 3. Sensor Applications Data Models: • The data model describes the flow of information between the sensor nodes and the data sink. • These models depends on the nature of the application. • The need to support a variety of data models increases the complexity of the routing design problem.
ROUTING STRATEGIES IN WIRELESS NETWORKS • Mobile Wireless Networks : • Ad-hoc networks. • WSNs. • Ad-hoc networks have several protocols like : 1. Proactive strategy relies on periodic dissemination of routing information to maintain consistent and accurate routing tables across all nodes of the network. 2. Reactive strategy :establish routes to a limited set of destinations on demand.. 3. Hybrid strategy.
ROUTING STRATEGIES IN WIRELESS NETWORKS • Ad-hoc networks routing protocols are not suited for WSNs for the following reasons: 1. Ad-hoc networks tend to exhibit their least desirable behavior under highly dynamic conditions. 2. Routing protocol overhead typically increases dramatically with increased network size and dynamics. 3. A large overhead can easily overwhelm network resources. Furthermore. 4. Traditional routing protocols operating in large networks require substantial internodal coordination, and in some cases global flooding. 5. Capabilities of the ad-hoc network nodes are relatively high compared to sensor nodes • New routing strategies are therefore required for sensor networks.
WSN Routing Techniques 1. flat network architecture protocols in which all nodes are considered peers. 2. Data-centric routing protocols use attribute-based naming, whereby a source node queries an attribute for the phenomenon rather than an individual sensor node. 3. Hierarchical routing protocols imposes a structure on the network. 4. Location based protocols where location information is needed in order to calculate the distance between two particular nodes so that energy consumption can be estimated.
1. flat network architecture protocols • all nodes are considered peers. • A flat network architecture has several advantages, including minimal overhead to maintain the infrastructure • and the potential for the discovery of multiple routes between communicating nodes for fault tolerance.
1.1 F looding And Gossiping • In flooding, each sensor receiving a data packet broadcasts it to all of its neighbors and this process continues until the packet arrives at the destination or the maximum number of hops for the packet is reached.
1.1 F looding And Gossiping • Gossiping is a slightly enhanced version of flooding where the receiving node sends the packet to a randomly selected neighbor, which picks another random neighbor to forward the packet to and so on. • Gossiping avoids the implosion problem by limiting the number of packets that each node sends to its neighbor to one copy. • The latency that a packet suffers on its way to the destination may be excessive, particularly in a large network.
2. Data-centric Protocols • Asource node queries an attribute for the phenomenon rather than an individual sensor node. • The interest dissemination is achieved by assigning tasks to sensor nodes and expressing queries to relative to specific attributes. • Different strategies can be used to communicate interests to the sensor nodes, including broadcasting and attribute-based multicasting.
2.1 SPIN • Sensor Protocols for Information via Negotiation. • The main objective of SPIN is to overcome the shortcomings of conventional protocols like flooding. • The basic property of this family of protocols are data negotiation and resource adaptation. • data negotiation requires that nodes running SPIN ‘‘learn’’ about the content of the data before any data are transmitted between network nodes.
2.1 SPIN • To carry out negotiation and data transmission, nodes running SPIN use three types of messages: • The first message type, ADV (advertise) • The second message type, REQ (request) • The third message type, DATA
2.1 SPIN • Basic operation of SPIN
2.1 SPIN • SPIN versions: • SPIN-PP (Basic Handshake sequence) • SPIN-EC (When a node energy level approaches the low threshold, a node running SPIN-EC reduces its participation in the protocol operations.)
2.1 SPIN • SPIN-BC (Is designed for broadcast networks where the ADV signal will reach all the sensors in the coverage area of the source) • SPIN-RL (Enhance its reliability and overcome message transmission errors caused by a lossy channel). by periodic broadcasting of ADV and REQ)
2.2 Directed Diffusion • Directed diffusion is a data - centric paradigm for sensor query dissemination and processing that provides energy efficiency, scalability, and robustness. • In contrast to SPIN, in direct diffusion the sink is the node that broadcast the request for a specific data throughout the network in what is called an “ interest message”. • A gradient can be thought of as a reply link pointing toward the neighboring node from which the interest is received.
3. Hierarchical Protocols • The main aim of hierarchical routing is to efficiently maintain the energy consumption of sensor nodes by: • involving them in multi-hop communication within a particular cluster. • performing data aggregation and fusion in order to decrease the number of transmitted messages to the sink.
3.1 LEACH • Low-energy adaptive clustering hierarchy (LEACH) is one of the most popular hierarchical routing algorithms for sensor networks. • The idea is to form clusters of the sensor nodes based on the received signal strength and use local cluster heads as routers to the sink. • The main objectives of LEACH are: 1. Extension of the network lifetime 2. Reduced energy consumption 3. Use of data aggregation to reduce the number of communication messages
3.1 LEACH • Cluster heads change randomly over time in order to balance the energy dissipation of nodes. • The LEACH operation can be depicted by the following two phases: • 1.setup phase: In which the cluster head selection is performed. • 2.steady-state phase: In which data collection, aggregation and delivery to the base station happens.
3.2 PEGASIS • Power-efficient gathering in Sensor Information Systems (PEGASIS) is an improvement of the LEACH protocol. • Rather than using a tree or star hierarchy as in the LEACH protocol , the PEGASIS protocol uses chain hierarchy. • Data aggregation is carried out by : • 1. The chain leader (3) issues a token to the right most node telling it to send its sensing information, when the request reaches node (7) it sends the information to node (6) where this one aggregate its information to it and consequently until the aggregated information reaches node (3) • 2.Node (3) issues the same operation to the left most node and after having all the information from the left and right sided sends the aggregated information to the sink. 1 4 6 0 2 3 5 7
3.2 PEGASIS • The sequential approach discussed before is not practical and consumes time. • A better approach would be using parallelism in aggregation. • In this approach node can use CDMA to work simultaneously and not interfere with each other. • Starting from the bottom up in the figure: • First each node send its date to the neighbor odd node. • Secondly each odd node sends its data. • Last node 7 send its aggregated data to Node 3. 7
4. Location based protocols • The main objective of geographical routing is to use location information to formulate an efficient route search toward the destination. • Geographical routing is very suitable to sensor networks, where data aggregation is a useful technique to minimize the number of transmissions toward the base station by eliminating redundancy among packets from different sources.
4.1 Geographic Routing • A node knows its own location, the locations of its neighbors, and the destination’s location (D) • The destination’s location is included in the packet header • Forwarding decision is based on local distance information • Greedy Forwarding: achieve max progress towards D x D y Greedy Forwarding
4.1 Geographic Routing • Greedy forwarding • Next hop is the neighbor that gets the packet closest to destination source destination • Greedy forwarding can lead into a dead end, where there is no neighbor closer to the destination.
4.1 Geographic Routing • The solution is to use a combination of greedy routing with what called (face routing), where the latter is a technique of routing that rout packets on the faces of the path • Figure below illustrates face routing .
WSN routing protocols comparison • LEACH, PEGASIS, SPIN, DD, Geographical routing comparison below :
Routing Protocols Selection for particular applications • LEACH, PEGASIS, SPIN, DD, Geographical routing comparison below :
