A Mobile Ad-hoc Network (MANET) Tho(2002), Perkins(2001) may be a collection of nodes, that are ready to connect on a wireless medium forming an absolute and dynamic network with wireless link. That is, over time the links between the nodes might modify and thanks to node mobility, nodes might disappear and new nodes may appear within the network. The physical size of a MANET is expected to be larger than the radio range of the wireless interfaces, thus for any two nodes in the network to be able to communicate, routing of traffic through a multi-hop path is necessary. In addition to the challenge presented by routing in traditional wired networks, a routing protocol for MANET must be able to respond to a high degree of topological changes in the network and still maintain stable routing. Also, the peculiarities of wireless interfaces (such as the inherent differences from wired media in medium access characteristics as well as the broadcast nature), must be taken into account. Finally, the fact that the available bandwidth on a wireless link currently is in order of magnitude smaller than that available wired network, requires that a protocol be carefully designed to reduce the amount of control traffic generated. Several protocols exist, addressing the problems of routing in MANET. Such protocols are traditionally divided into 2 classes, depending on when a node acquires a route to a destination.

The general survey of MANET is taken from C.E. Perkins (2001) and C.K. Tho (2002). Routing protocols in MANET and its classification and performance comparison is from K. Prabu and A.Subramani (2012). Optimized link state routing protocol in MANET is from T. Clause (2003), Floriano (2009) and Thomas Kunz (2010). Reduced route request in MANET using MPR selection and select neighbour node from source node is taken from Voorhaen (2006) and Zhihao Guo (2007). Problem identification of this paper and proposed ESPR algorithm concept has been identified from De Rango (2008), Zhigao Guo (2011) and K. Prabu (2013).

Routing is the Exchange of information (in this case typical term 'packets') from one station of the network to the other. The major goals of routing are to find and maintain routes between nodes in a dynamic topology with possibly uni-directional links, using minimum resources. A protocol is a set of standard or rules to exchange data between two devices. These protocols find a route for packet delivery and deliver the packet to the correct destination. Routing protocols are classified into unicast, multicast and broadcast routing protocols. 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 the same message to multiple destinations. Broadcast is the basic mode of operation over a wireless channel; each message transmitted on a wireless channel is generally received by all neighbors located within onehop from the sender. 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, Prabu and Subramani (2012).

It keeps track of routes for all destinations in the ad hoc network, called Proactive protocols or Table-Driven Protocols, as the routes can be assumed to exist in the form of tables. Each node maintains one or more tables containing routing information to every other node in the networks. All nodes keep on updating these tables to maintain latest view of the network. The main advantage is that Communications with arbitrar y destinations experience minimal initial delay from the point of view of the applications. The disadvantages of proactive protocols is that Additional control traffic is needed to continually update stale route entries. In Table Driven routing protocols some of the existing table driven or proactive protocols are: DSDV (Destination sequenced distance vector), CGSR (Cluster-head gateway Switch routing), WRP (Wireless routing protocol), STAR (Source tree adaptive routing protocol), OLSR (Optimized link state routing protocol), FSR (Fisheye state routing protocol), HSR (Hierarchical state routing protocol) and GSR (Global state routing protocol).

In this protocol, routes are created as and when 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 route is no longer needed. The advantage is that due to high uncertainty in the position of the nodes, however, the reactive protocols are much suited and perform better for MANET. 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 are: DSR (Dynamic source routing), AODV (Ad hoc on-demand distance vector), ABR (Associative based routing), SSA (Signal stability based adaptive routing), PLBR (Preferred link based routing protocol), TORA (Temporally ordered routing) and FORB (ipv6 flow handoff in ad-hoc wireless network).

The protocol belonging to this category combine the best features of the above 2 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 within this zone, we can use table-driven approach. For nodes that are located beyond this zone, we can use on-demand approach. Disadvantages of hybrid protocols is that success depends on amount of nodes activated and reaction to traffic demand depends on gradient of traffic volume. Some of the Hybrid Routing Protocols are: CEDAR (Core extraction distributed adhoc routing), ZRP (Zone Routing Protocol) and ZHLS (Zone based hierarchical link state routing).

OLSR according to Clausen and Jacquet (2003) is a proactive routing protocol for MANET. The protocol inherits the stability of the link state algorithm and has the advantage of getting routes straightaway accessibility once required due to its proactive nature. OLSR minimizes the overhead caused by flooding of control traffic by using only selected nodes, known as Multi-Point Relays (MPR), to carry control messages. This system considerably reduces the amount of retransmissions needed to flood a message to any or all nodes within the network. Upon receiving associate update message, the node determines the routes (sequence of hops) toward its notable nodes. Every node selects its MPRs from the set of its neighbors saved within the Neighbor list Voorhaen, Antwerpen and Blondia (2006), Zhihao Guo and Malakooti (2007). The set covers nodes with a distance of 2 hops. The concept is that whenever the node broadcasts the message, only the nodes enclosed in its MPR set are chargeable for broadcasting the message. OLSR uses HELLO and TC messages. The Topology control (TC) messages continuously maintain the routes to any or all destinations within the network. The protocol is extremely economical for traffic patterns wherever massive (an outsized/an oversized) set of nodes of human action with another large set of nodes, and wherever the (source, destination) pairs change over time. The HELLO messages are changed periodically among neighbor nodes, to discover the identity of neighbors and to signal MPR choice. The protocol is especially suited for large and dense networks, because the improvement is finished by using MPRs that work well during this context. The larger and dense a network, a lot of improvement will be achieved as compared to the classic link state algorithm. OLSR uses hop-by-hop routing, i.e., every node uses its local information to route packets.

// The following steps are repeated to find the path from Source S to Destination D in time interval t.
// The same procedure is followed in 1 hop, 2 hop and so on.,
start
select hop1(v) node from the source S
then store V,
select FCN(v) from set V
then store Vf
find Edgenode (En(v)) from Set Vf
if(En(v) Motion towards Destination D)
then
calculate Mv(v) in particular time interval t
calculate Tp(v)
calculate Dt(v) from S
calculate Tp(S)
if(Tp(v) &Tp(S) is sufficient to forward dt data)
then if (Dt(v) is within Range of S)
accept(v)
add (Path(S,v,Dt))
else
reject(v)
end;

Figure 1 shows the flow diagram for the energy saver path routing algorithm in MANET using OLSR. Select all the vertices from source within 1 hop and store. Again select the entire Forward Capacity Node (FCN) from the set of vertices within 1 hop and store. Find the edge node En(v) from the set of forward capacity vertices with maximum distance node from source and also within one 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 that node, and Tp(S) source have 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 then 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.

Figure 1. Flow diagram for ESPR algorithm

In this section, the authors evaluate the performance of routing protocol of MANET in an open environment. The simulations were carried out using Network Simulator (NS-2) [12]. The authors have simulated the mobile ad hoc routing protocols using this simulator by varying the number of nodes. The IEEE 802.11 distributed coordination function (DCF) is used as the medium access control protocol. The packed size is 512 bytes. The traffic sources are UDP. Initially nodes were placed at certain specific locations and then the nodes move the speeds up to 25 meter/sec. For fairness identical mobility and traffic scenario were used across different simulations. The simulation parameters are shown in Table 1.

Table 1. Simulation Parameter (Number of nodes 50-250)

The performance the proposed Energy Saver Path Routing (ESPR) algorithm and evaluation of the performance of the algorithm is compared with Ordinary OLSR Protocol.

The following metrics are measured and compared.

The ratio of the packets that successfully reach destination.

 

In this part, the authors compare the performance of ESPR and ordinary OLSR. The ESPR algorithms have good delivery ratio above 90% and also ESPR algorithm is providing better performance compared to ordinary proactive OLSR protocol. In Figure 2 ESPR Packet Delivery Ratio (PDR) has improved than ordinary OLSR with number of node increased.

Figure 2. Packet Delivery Ratio vs. Number of nodes

The end-to-end delivery is number of packets successfully delivered at the same time delay is reduced. Using ESPR algorithm for sending packet from source to destination, more time delay is reduced than ordinary OLSR below 60%. Figure 3 shows that in ESPR more time delay is reduced than ordinary OLSR with number of node increased.

Figure 3. End-to-End Delay vs. Number of nodes

The ESPR algorithm takes minimum energy to select the path from source to destination for each and every hop in dynamic environment. In Figure 4, the proposed ESPR algorithm takes minimum energy (Joules) than ordinary OLSR with transmission range increased.

Transmission Power Calculations:

 

Figure 4. Consumed Energy (Joules) vs. Transmission Range (Meters)

The experiments and simulations have shown that the proposed protocol for routing in MANET works in most situations, it even works well. This experiment revealed shortcomings in a couple of situations. The proposed ESPR routing algorithm is using modified by ordinary OLSR Protocol. The performance of the proposed concept is well than ordinary OLSR protocol. In this paper the proposed routing algorithm ESPR has improved Packet Delivery Ratio (PDR) above 90%, reduced End-to-End delay below 60% and reduced transmission of power (Joules) than ordinary OLSR. In Figure 2, ESPR has improved packet delivery ratio compared to ordinary OLSR. In Figure 3 ESPR has reduced end-to-end delay compared to ordinary OLSR. In Figure 4 ESPR reduced transmission of power compared to ordinary OLSR. Finally ESPR has provided overall better performance than ordinary OLSR.