Mobile Ad-hoc Network (MANET) is most often a cluster of wireless mobile nodes dynamically establishing a brief live network without the use of network infrastructure. MANET is associated with the rising space of analysis in the communication network world. The change in network topology due to node movement associated with the link failure and creation, source in radio resources and bandwidth, limited battery power and computing capability pose challenges in packet routing in MANET. Energy efficiency is the most important design consideration in MANETs, due to the limited battery life of mobile terminals. The network lifetime will improve suitability, reducing the requirement power of connections. A number of Routing protocols have been proposed in the recent scenario. There are many advantages and disadvantages in those algorithms. This paper is a survey of the new and improved energy based routing methods in Mobile Adhoc Networks.
Reducing energy consumption has been studied in the backbone networks and the data center networks. In mobile networks, the communication between the totally different devices may be either wireless or wired. Recently, network researcher's square measure for learning networks supported in new communication techniques, especially wireless communication. Mobile networks have a high error rate, bandwidth limitations and power restrictions. Thanks to impact from transmission power, receiver sensitivity, noise, fading and interference, wireless link capacity frequently varies. MANET supports multi-hop routing, where the nodes other than the source and the destination nodes also take part in packet forwarding from one end to another. This results in the energy consumption of intermediate nodes even though they are not the actual sender or receiver of the data. The available battery power of the nodes decide the lifetime of the node as well of the whole network [1,2].
A Mobile Ad-hoc Network (MANET) is a self configuring infrastructure less network of mobile devices connected by wireless links. Adhoc is Latin and means “for this purpose”. Each device in a MANET is free to move independently in any direction, and will therefore change its links to other devices frequently. Some MANETs are restricted to local area of wireless devices (such as a group of laptop computers), while others may be connected to the Internet. Because of the dynamic nature of MANETs, they are typically not secure, so it is important to be cautious as what data is sent over a MANET. Energy saving is potentially achieved by appropriately provisioning network capacity, by shutting down unnecessary network elements, while the capacity of remaining network elements still meet some demands [2-4].
Energy efficiency is one of the most important design consideration in MANETs, due to the limited battery life of mobile terminals. The network lifetime will be improved by suitably reducing the requirement of power for connections. In energy constrained operations, it is important to save energy, which results in the improvement of network lifetime by searching alternative paths between the same source and destination [2,4].
Now-a-days, power saving is one of the main constraints in MANETs. Normally, portable power sources such as batteries are used in a MANET. Hence, battery technology development is very slow. Many power aware routing protocols are considered to overcome the problem. In order to overcome, efficient power management, various power aware solutions algorithm have been described in this paper.
A Routing protocol is a protocol that specifies how routers communicate with each other, disseminating information that enables them to select routes between any two nodes on a computer network, the choice of the route being done by routing algorithms. Major goals of routing are to find and maintain routes between the nodes in a dynamic topology with possibly unit-directional links, using minimum resources. A routing protocols shares this information first among the immediate neighbors, and then determines the throughput of the network [1], [5]. This way, the routers again knowledge of the topology of the network. Routing protocols for MANET have been classified according to the strategies of discovering and maintaining routes into unicast, multicast and broadcast routing protocols [1], [4].
Unicast forwarding means a one-to-one communication, i.e., one source transmits data packets to a single destination. Multicast routing protocols come into play, when a node needs to send a same message to multiple destinations. Broadcast is the basic mode operation over a wireless channel; each message transmitted on a wireless channel is generally received by all neighbors located within one hop from the sender [1]. The studies on various aspects of unicast routing protocols have been an active area of research for many years such as Table Driven or Proactive, On-Demand Driven or Reactive and Hybrid Routing Protocols.
Using a proactive routing protocol, nodes in a mobile adhoc network continuously evaluate routes to all reachable nodes and attempt to maintain consistent, up-to-date routing information. Keeping track of routes for all destinations in the ad hoc network are called proactive protocols or Table driven protocols. It maintains a consistent information about the path from each node to every other destination by periodically updating the routing tables. The main advantage is that, communications with arbitrary destinations experience minimal initial delay from the point of view of applications. The disadvantages of proactive protocols is that, additional control traffic is needed to continually update the stale route entries. Example of Table Driven Protocols is: DSDV, CGSR, WRP, STAR, OLSR, FSR, HSR, and GSR [1] , [2], [4], [5].
In reactive routing protocol, routing paths are searched, only when they are needed. The aim of the On Demand or the Reactive Routing Protocols is to reduce the amount of bandwidth consumed by maintaining the routes to only those destinations to which a path request is required. When a transmission occurs from source to destination, it invokes the route discovery procedures. The route remains valid till destination is achieved or until the router is no longer needed. The main advantage is that due to high uncertainty in the position of the nodes, however, the reactive protocols are much suited and perform better for MANETs. The disadvantages of reactive protocols include high latency time in route finding and excessive flooding leading to network clogging. Some of the On Demand or Reactive Routing protocols: DSR, AODV, ABR, SSA, PLBR, TORA and FORB [1], [2].
This protocol belonging to this category combines the best features of the above two categories. Nodes within a certain distance from the node concerned or within a particular geographical region are said to be within the routing zone of the given node. For routing with this zone, a On-Demand approach is used. Disadvantages of hybrid protocols is that, the success depends on gradient of traffic volume. Some hybrid Protocols are: CEDAR, ZRP, and ZHLS.
The Optimized Link State Routing (OLSR) Protocol is a proactive routing protocol. They have routes that are immediately available in each node for all destinations the network. OLSR [1], [4] is an optimization of pure link state routing protocol like Open shortest Path First (OSPF). OLSR minimizes the scale of the management packet by considering together with only a subset of its current neighbors, and minimizes flooding by the employment of a Multipoint Relay (MPR) Strategy. A Multi Point Relay reduces the size of control messages. The use of MPRs also minimize the flooding of control traffic [4]. Using the MPR technique, every node selects a number of its current neighbors, as its MPRs which square measure allowed the rerunning of management packets.
When a node receives an effect packet, it only rebroadcasts the packet, if it's a MPR of the causing node. Otherwise it only reads and processes it, but doesn't return the management packet [1]. OLSR contains two types of control messages: neighborhood and topology messages, known as Hello message and Topology Control (TC) messages. It discovers and then disseminates the link state information throughout the Mobile ad-hoc Network. OLSR uses power and network resources. It requires a reasonably large amount of bandwidth and CPU power [4], [5].
Ad-hoc On Demand Distance Vector Routing Protocol is an On-demand protocol that discover routes on a needed basis using the route discovery process. It uses traditional routing tables, one entry per destination to maintain the routing information. When a route to a new destination is needed, the node broadcasts a RREQ to find a route to the destination. AODV sequence numbers is maintained in each destination to determine freshness of the routing information and to prevent routing loops. These sequence numbers are carried by all the routing packets. The routing is made available by uncasing a PREP back to organization of the RREQ.
AODV is the Ad-hoc On Demand Distance Vector Routing Protocol which is a reactive protocol. Its aim is to reduce the amount of bandwidth consumed by maintaining the routes only to those destinations to which a path request is required. Reactive Protocols are designed for Mobile Adhoc Networks to overcome the increased overhead problem in protocols. Unlike Proactive Protocols, reactive protocols create a route only when desired, if a node desires to send a message to a destination node. The process is completed when a source node finds a route to the destination. A route maintanance procedure is implemented to maintain a route until the destination is no longer available or not desired [4-7].
The dynamic source routing protocol is a simple and efficient routing protocol designed specifically for the use in the multihop mobile adhoc networks. DSR allows the network to be completely self-organizing and selfconfiguring without the need of any predefined infrastructure. This protocol is composed of the two main mechanisms.
The route discovery procedure of DSR portocol often discovers many routes from source node to destination node and the route with minimal hop is more possible chosen for data transmission than others, the nodes frequently chosen are more likely to consume more energy, which results in short usage of the battery [9] . One of the primary characteristics of DSR is that it specifies each node along the path to the destination. Route request (RREQ) and Route reply (RREP) packets accumulate source routes so that, once a Route is discovered, the source learns the entire source route and can place that route into subsequent data packets [8] .
The Temporary Ordered Routing Algorithm (TORA) is a highly adaptive, efficient and scalable distributed routing algorithm based on the concept of link reversal. TORA is proposed for highly dynamic mobile, multichip wireless networks. It is a source, initiated on demand routing protocol. It finds multiple routes from a source node to destination node. The main feature of TORA is that, the control message are localized to a very small set of nodes near the occurrence of a topological change. The protocol has three basic functions: Route Creation, Route maintenance and Route erasure. TORA has been maintaining multiple routes to destinations so that topological changes does not require any reaction to all [10] .
Destination Sequenced Distance Vector Routing Algorithm (DSDV) is a table driven routing scheme for adhoc mobile networks. It is based on the Bellman-ford algorithm. The improvement made to the Bellman-Ford algorithm includes freedom from loops in routing table by using sequence numbers. Each node acts as a router, when as a routing table is maintained and periodic routing updates are exchanged, even if the routes are not needed. A sequence number associated with each route are a path to the destination to prevent routing loops [5]. In DSDV, each mobile node of an Ad-hoc network maintains a routing table, which lists all the available destinations and sequence number generated by the destination node. Using such routing table stored in each mobile node, the packets are transmitted between the nodes of an ad-hoc network. Each node of the Ad-hoc network updates the routing table with advertisement periodically or when significant new information is available to maintain the consistency of the routing table with the dynamically changing topology of the Ad-hoc network.
One important goal of routing protocol is to keep the network functioning as long as possible along with establishing correct and efficient routes between the pair of nodes. Transmission power control and load distribution are two approaches to minimize the active communication energy, and sleep/power-down mode is used to minimize energy during inactivity. This section presents a set of energy aware routing protocols and their performances are analyzed in various scenarios.
K. Prabu (2014), proposed a routing algorithm based on energy to find the path between source and destination using high potential score edge node selections. It is used to find the shortest path from a source to destination. OLSR protocols using ESPR (Energy Saver Path Routing Algorithm) in MANETs selects all the vertices from source within 1 hop and stores them. Again, select the entire Forward Capacity Node (FCN) from the set of vertices within 1 hop and store. To find the edge node En (V) from the set of forward capacity vertices with maximum distance node from source and also within 1 hop transmission range. Source node can maintain the edge node capacity towards the destination, then calculate Mv (V) motion of that node in particular time interval t, Tp(V) Transmission power of that node, Dt(V) distance from source to the node, and tp(S) source has sufficient power to forward the data to that selected edge node. If the Tp(V) and Tp(S) is sufficient to forward dt (Data Transfer in mbps) data than if Dt(V) is within the range of source, accept the node and add path with (S,V,Dt), otherwise the node will be rejected.
Utkarsh, Mukesh Mishra and Suchismita Chinara, proposed a ESAR algorithm which improves the network lifetime. Its selects the best path for packet transmission till any nodes in the path exhaust the battery power beyond a threshold value. In the well known AODV routing algorithm, the source node sends RREQ and waits for RREP from the destination and gets the first RREQ, it sends back the RREP through that path as that path is considered as the shortest path. Then after any RREQ message received by the destination is discarded. Considering the energy impact on the routing path, it is understood that as the same path is used for packet transmission by the source and destination, the energy consumed by the nodes in that path is very high. AODV and EESODR algorithm using the shortest path in terms of minimum hop counts is chosen by AODV for packet routing.
The transmission delay is reduced, whereas the network lifetime is compromised. At the same time, EEAODR choose an alternative path for packet transmission to save the energy of shortest path, while compromising the delay in transmission. It considers the actual distance between the source and destination along with the minimum available energy of a node in the path. When a source does not find the path to the destination in its routing table, it broadcasts the route request RREQ message. The receiver upon receiving the first RREQ waits for a period to collect more RREQ message paths and are stored for the selection of actual routing paths as and when required. It selects the path with minimum cost value indicating that the path has the shortest distance to the destination and has the maximum of the minimum available battery power of the node among the different paths. This selected path is chosen as the best path for packet transmission till any node in the path exhaust battery power beyond a threshold value.
Yong Oh Lee and A.L. Narasimma Reddy proposed techniques to construct an appropriate topology that takes the traffic demands into account and also the study on how much multipath routing can be contributed to energy saving compared to the single/shortest path routing. The authors show that the proposed techniques reduce energy consumption by an additional 17% over previous schemes. It assigns the traffic to demand multiple paths and can be seen as a modified binpacking problem, where available paths are the bins and the traffic is the object to be packed. In single/shortest path routing, the traffic demand between an OD-pair cannot be split and allocated to the available paths. Two bin packing algorithms in order to assign the traffic demand of OD-pair to multiple paths. They considered all the available paths as bins, and divides these bins into several set of closed bin set, which satisfies a certain condition, i.e. path length.
First, the order of OD-pairs is Considered, Before sorting each OD-pair, compute multiple paths, whose path length is from the length of the shortest path to the length of the shortest path plus two extra hops. If the number of possible paths is larger than K, it is restricted to K-shortest paths. Routing density is expected to give an indication of how critical or useful this link can be in routing various flows. To improve energy savings, we iteratively run algorithm on the reduced topology and adding a highly utilized node on the currently-used topology is expected to turnoff more nodes in the topology control than adding a highly utilized node on the original topology.
K. Prabu has proposed a new algorithm to develop a new routing protocol for MANETs. The proposed enhanced version of Power Aware Optimized Link State Routing (PAOLSR) protocol using proactive OLSR protocol has a new metric to find the route with higher transmission rate, less latency and better stability. It checks bandwidth and delay constraint during request and uses a well new mobility prediction mechanism to determine the stability of link during a path selection. The performance of PAOLSR is evaluated by using NS-2 simulation tool and is compare with the OLSR protocol.
It uses a mathematical model in MANET Link stability model, Link expiration time, and Energy drain rate. Select the hop1 node from source node S, then store the vertices set V. Again select Route Request (R-REQ) node from the vertices set V. Then store Route Request Vertices, set VRREQ and set all the initial values as null. Check if the condition of broadcast route request node i(BR_REQ(I)) is greater than are equal to the initial Broadcast Route Request node (BR_REQ) and also the destination node i(Di) is greater than are equal to the destination D. PA-OLSR has less consumed energy with an increased transmission range compare to the existing OLSR protocol. PA-OLSR outperforms the proactive OLSR in terms of route stability, network lifetime, and energy consumption.
In this paper, the characteristics of Mobile Ad-hoc Networks, their application areas and also the routing in Mobile Ad-hoc Networks are discussed. The classification of routing protocols, the different types of protocols used in Mobile Ad-hoc networks, their advantages and disadvantages are also seen. Energy based routing protocols proposed by various authors are discussed in this paper with regard to power aware routing, which is achieved by designing an energy efficient protocol that reduces energy consumption during the conventional protocols.