More Related Content
What's hot
What's hot (20)
Similar to WSN-Routing Protocols Energy Efficient Routing
Similar to WSN-Routing Protocols Energy Efficient Routing (20)
More from ArunChokkalingam
More from ArunChokkalingam (14)
Recently uploaded
Recently uploaded (20)
WSN-Routing Protocols Energy Efficient Routing
- 1. Dr.Arun Chokkalingam Professor Department of Electronics and Communication RMK College of Engineering andTechnology Chennai. WSN-Routing Protocols Energy Efficient Routing
- 2. UNIT III WSN NETWORKING CONCEPTS AND PROTOCOLS • MAC Protocols for Wireless Sensor Networks, • Low Duty Cycle Protocols And Wakeup Concepts – • S-MAC, • The Mediation Device Protocol • Contention based protocols – PAMAS, • Schedule based protocols – LEACH, • IEEE 802.15.4 MAC protocol, • Routing Protocols • Energy Efficient Routing, • Challenges and Issues inTransport layer protocol.
- 3. Objective of Routing protocols
- 4. Routing protocols • In a multihop network, intermediate nodes have to relay packets from the source to the destination node. • Such an intermediate node has to decide to which neighbor to forward an incoming packet. • Typically, routing tables that list the most appropriate neighbor for any given packet destination are used. • The construction and maintenance of these routing tables is the crucial task of a distributed routing protocol.
- 5. Energy-efficient unicast Routing 1. Minimize energy per packet (or per bit) 2. Maximize network lifetime 3. Routing considering available battery energy 1. MaximumTotal Available Battery Capacity 2. Minimum Battery Cost Routing (MBCR) 3. Min– Max Battery Cost Routing (MMBCR) 4. Conditional Max – Min Battery Capacity Routing (CMMBCR) 5. Minimize variance in power levels 6. MinimumTotalTransmission Power Routing (MTPR)
- 6. Example scenario for a communication between nodes A and H
- 7. Energy-efficient unicast • At a first glance, energy-efficient unicast routing appears to be a simple problem: • Take the network graph, assign to each link a cost value that reflects the energy consumption across this link, and pick any algorithm that computes least-cost paths in a graph. • shortest path algorithm to obtain routes with minimal total transmission power. • In fact, there are various aspects how energy or power efficiency can be considered of in a routing context. • following Figure shows an example scenario for a communication between nodes A and H including link energy costs and available battery capacity per node.
- 8. Minimize energy per packet (or per bit) • The most straightforward formulation is to look at the total energy required to transport a packet over a multihop path from source to destination.. • The goal is then to minimize, for each packet, by selecting a good route. • Minimizing the hop count will typically not achieve this goal as routes with few hops might include hops with large transmission power to cover large distances • However, this cost metric can be easily included in standard routing algorithms. • In the example • The minimum energy route is A-B-E-H, requiring 3 units of energy. • The minimum hop count route would be A-D-H, requiring 6 units of energy.
- 9. Maximize network lifetime • A WSN’s task is not to transport data, but to observe (and possibly control). • Hence, energy-efficient transmission is at best a means to an end • Which event to use to differentiate the end of a network’s lifetime is, 1. Time until the first node fails. 2. Time until there is a spot that is not covered by the network 3. Time until network partition (when there are two nodes that can no longer communicate with each other
- 10. Maximum Total Available Battery Capacity • Choose that route where the sum of the available battery capacity is maximized • , Looking only at the intermediate nodes route A-B-E-G-H has a total available capacity of 6 units, • but that is only because of the extra node G that is not really needed – such detours can of course arbitrarily increase this metric. • Hence, A- B-E-G-H should be discarded as it contains A-B-E-H as a proper subset. • A- B-E-G-H = 6 units • A-B-E-H= 4 Units • Finally, route A-C-F-H = 5units is selected.
- 11. Minimum Battery Cost Routing (MBCR) • Instead of looking directly at the sum of available battery capacities along a given path, • MBCR looks at the “reluctance” of a node to route traffic. • This reluctance increases as its battery is drained; • for example, routing cost can be measured as the reciprocal of the battery capacity. • Then, the cost of a path is the sum of this reciprocals and the rule is to pick that path with the smallest cost. • Since the reciprocal function assigns high costs to nodes with low battery capacity, • this will automatically shift traffic away from routes with nodes about to run out of energy. • route A-C-F-H is assigned a cost of 1/1+ 1/4 = 1.25, • route A-B-E-H is assigned a cost of 1/2+ 1/2 = 1, • but route A-D-H only has cost 1/3=0.33. Consequently, this route is chosen, protecting node C from needless effort
- 12. Conditional Max – Min Battery Capacity Routing (CMMBCR) • Another option is to conditionalize upon the actual battery power levels available. If there are routes along which all nodes have a battery level exceeding a given threshold, then select the route that requires the lowest energy per bit. • If there is no such route, then pick that route which maximizes the minimum battery level. (Minimum Battery Cost Routing )
- 13. Minimize variance in power levels • To ensure a long network lifetime, one strategy is to use up all the batteries uniformly to avoid some nodes prematurely running out of energy and disrupting the network. • Hence, routes should be chosen such that the variance in battery levels between different routes is reduced.
- 14. MinimumTotalTransmission Power Routing (MTPR) • looked at the situation of several nodes transmitting directly to their destination, mutually causing interference with each other. • A given transmission is successful if its SINR (signal-to-interference-plus-noise ratio) exceeds a given threshold. • The goal is to find an assignment of transmission power values for each transmitter (given the channel attenuation metric) such that all transmissions are successful and that the sum of all power values is minimized. • MTPR is of course also applicable to multihop networks. • A direct performance comparison between these concepts is difficult as they are trying to fulfill different objectives.
- 15. Some example unicast protocols 1. Distance vector routing on top of topology control 2. Maximizing time to first node outage as a flow problem 3. Maximizing time to first node outage by a max– min optimization 4. The max min zP min approximation 5. Maximizing number of messages 6. Bounding the difference between routing protocols
- 16. Some example unicast protocols Attracting routes by redirecting • Step 1: Let us assume that node X and Z are unaware of the presence of Y node. • When node X communicates with node Z, node X has no choice but to transmit packets directly to node Z . • in the case that node X is not aware of its attenuation distance from node Z, node X may search for node Z by transmitting at full power and then adjusting its transmission power once node Z replies with a packet of its own.
- 17. • Step2: because nodeY is capable of overhearing packets from both X and Z, • nodesY can estimate the power attenuation with respective to both nodes. • If nodeY computes that the new route X -Y -Z offers a lower cost than the route X to Z. • then the nodeY sends a route redirection message to node X as illustrated in figure. • In this example the route Z-Y-X is more costly than route Z to X. • Step 3: After receiving the route redirection message from nodeY, node X transmits packet for node Z first to nodeY which then forwards these packet to node Z. • The advantage of this scheme is that its administrative overhead regarding explicit message exchanges is small. • The need to overhear traffic is, however, not quite as appealing and makes this scheme not particularly suitable for WSNs.
- 18. Bounding the difference between routing protocols • To approach this problem, the graph is partitioned into “spheres” Si that include all the nodes that are reachable from the base station in at most i hops. • The interesting case is then networks where “most” nodes are more than a single hop away from the base station • Then, all traffic has to go through the nodes of sphere S1, and because there are relatively few of these nodes, they limit the lifetime of the network. •
- 19. Multipath unicast routing 1. Sequential Assignment Routing (SAR) 2. Constructing energy-efficient secondary paths 3. Simultaneous transmissions over multiple paths 4. Randomly choosing one of several paths 5. Trade-off analysis
- 20. Multipath unicast routing Source Sink Disjoint paths Primary path Secondary path Source Sink Disjoint paths Primary path Secondary path Source Sink Braided paths Primary path Source Sink Braided paths Primary path • The unicast routing protocols discussed so far tried to construct a single energy-efficient path between a sink and a receiver. • Focusing on choosing the best possible path,. • Extending the focus to multiple paths and trying to balance • Moreover, multiple paths provide redundancy in that they can serve as “hot standbys” to quickly switch to when a node or a link on a primary path fails.
- 21. Cont • Such multipath routing protocols construct several paths between a given sender and receiver. • The basic goal is to find k paths that do not have either links or nodes in common • Once the paths have been established by the routing protocol, the forwarding phase can then dynamically decide which path to choose to transmit a packet. • This can increase the robustness of the forwarding process toward link or node failures. • Classical multipath routing has been explored for two reason: load balancing and robustness.
- 22. Constructing energy-efficient secondary paths • When using multiple paths as standby paths to quickly switch to when the primary path fails, an obvious concern is that of the energy efficiency of these secondary paths compared to the optimal primary path. • Their first observation is that strictly requiring node disjointness between the various paths tends to produce rather inefficient secondary paths as large detours can be necessary. • To overcome this problem and yet retain the robustness advantages of multiple paths, • they suggest the construction of so-called “braided” paths .These braided paths are only required to leave out some (even only one) node(s) of the primary path but are free to use other nodes on the primary path. • This relaxed disjointness requirement results in paths that can “stay close” to the primary path and are therefore likely to have a similar, close to optimal energy efficiency as the primary path.
- 23. Disjoint Multipaths • The first multipath mechanism we consider constructs a small number of alternate paths that are node-disjoint with the primary path, and with each other. • These alternate paths are thus unaffected by failures on the primary path, but can potentially be less desirable than the primary path. Source Sink Disjoint paths Primary path Secondary path Source Sink Disjoint paths Primary path Secondary path Source Sink Braided paths Primary path Source Sink Braided paths Primary path
- 24. Braided Multipaths • While disjoint paths can be energy inefficient since node-disjoint paths could be potentially longer than the primary path. • Our braided multipath relaxes the requirement for node disjointedness. • Alternate paths in a braid are partially disjoint from the primary path, not completely node-disjoint. • This alternate best path need not necessarily be completely node disjoint with the primary path. We call the resulting set of paths (including the primary path) the idealized braided multipath. Source Sink Disjoint paths Primary path Secondary path Source Sink Disjoint paths Primary path Secondary path Source Sink Braided paths Primary path Source Sink Braided paths Primary path