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# AN EFFICIENT ANT BASED QOS AWARE INTELLIGENT TEMPORALLY ORDERED ROUTING ALGORITHM FOR MANETS

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International Journal of Computer Networks & Communications (IJCNC)

International Journal of Computer Networks & Communications (IJCNC)

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• 3. International Journal of Computer Networks & Communications (IJCNC) Vol.5, No.4, July 2013 191 will take: either A or B. The first ones will choose a random direction and will deposit pheromone along their way. The ants taking the way SBD (or DBS), will arrive at the end of the obstacle (depositing more pheromone on their way) before those that take the way SAD (or DAS). So, pheromone intensity of route SBD becomes greater than that of route SAD. So, the ants choose the path SBD (Figure 1c). The ants will then find the shortest way between their nest and the food source. (a) (b) (c) Fig. 1. Behavior of ants for searching the food from S to D In most cases, an artificial ant will deposit a quantity of pheromone represented by Δτi,j only after completing their route and not in an incremental way during their advancement. This quantity of pheromone is a function of the found route quality. Pheromone is a volatile substance. An ant changes the amount of pheromone on the path ( i, j) when moving from node i to node j as follows: τi,j = σ.τi,j + Δτ i,j (1) Where 10 <<  and  is the pheromone evaporation factor which avoids infinite increment of pheromone which may leads to stagnation of the route . At one point i, an ant chooses the point j (i.e. to follow the path ( i, j)) according to the following probability: Pi,j = ∑∈Cki ikik ijij , ).()( ).()(     (2) Where, τi,j: is the pheromone intensity on path ( i, j). ηi,j: is the ant’s visibility field on path ( i, j)(an ant assumes that there is food at the end of this path). α and β : are the parameters which control the relative importance of the pheromone intensity compared to ant’s visibility field. C: represents the set of possible paths starting from point i (( i, k ) is a path of C). Like real pheromone the artificial pheromone decreases over time for fast convergence of pheromone on the edges. This happen in ACO according to the following formula: τi,j = (1-q). τi,j q∈(0,1] (3)
• 7. International Journal of Computer Networks & Communications (IJCNC) Vol.5, No.4, July 2013 195 drain rate (path (i, j)) or DR (R) = ),(max jiPn∈ { drain rate(n)} where, drain rate (n) is the rate of energy dissipation of node ‘n’ on path(i, j). hop count (path (i, j)) or HC (R) = Number of nodes in the path. 5.1 CALCULATION OF PHEROMONE Ant deposits pheromone during traversal of the link for finding a route. The quantity of pheromone it deposited on each link (i, j) along the route R is noted by ji,∆ and it is a function of global quality of route R. It is expressed by the following equation- ji,∆ = DRHCD EB RDRRHCRD RERB   )()()( )()( ++ + (4) Here λB, λE, λD, λHC and λDR are the weight factors which indicate the relative significance of the QoS parameters during pheromone update on path (i, j). The quantity of the deposited pheromone is defined only after finding the route. The pheromone quantity of the link (i, j) is updated according to the equation (1). 5.2 CALCULATION OF PATH PREFERENCE PROBABILITY Path Preference Probability is calculated in each intermediate node as well as source node upon receiving of QRY Reply_Ant. Suppose current node i receives QRY Reply_Ant from node j for destination d, then the Path Preference Probability is calculated as- Pijd= ∑ ∈ iNk ijdikdikdikdikdik ijdijdijdijdijdij DREBD DREBD 654321 654321 ][].[].[].[].[][ ][].[].[].[].[][     (5) Here α1, α2, α3, α4, α5 and α6 are the tunable parameters which control the relative weights of pheromone trails, hop count, bandwidth, energy and drain rate respectively. Ni is the set of neighbors of i and k is the neighbor node of i through which a path to destination is known. The relative metrics are calculated from source i to destination d via j as- Dijd d))(i,delay(path 1 = ijdη d))ath(i,hopcount(p 1 = Bijd= bandwidth (path(i,d)) Eijd = energy (path (i,d)) ijdDR d))i,rate(path(drain 1 = Now, source as well as neighbors has multiple paths from source to destination. The path with higher Path Preference Probability is selected for the data transmission.
• 9. International Journal of Computer Networks & Communications (IJCNC) Vol.5, No.4, July 2013 197 Fig. 2. HELLO_ Ant packet format Fig. 3. QRY Request_Ant Packet format Fig. 4. QRY Reply_Ant Packet format Pkt_Type = HELLO Energy Drain rate Starting time Pkt_Type = QRY Request_Ant Req_Starting Time Bandwidth Pkt_Type = QRY Reply_Ant Hop Count Delay Energy Drain rate Bandwidth 0 2 9 17 31 Source ID Destination ID Stack of nodes visited : : 0 2 17 31 Source ID Stack of nodes to be visited : : Destination ID Height (Hi) 0 2 8 14 19 25 31
• 11. International Journal of Computer Networks & Communications (IJCNC) Vol.5, No.4, July 2013 199 6.2. ROUTE MAINTENANCE PHASE Fig. 5. UPD packet format for a node (k) Fig. 6. Error packet format for a node UPD packet: It contains the destination id (did), height of the node (say, Hk of node k) that is broadcasting the packet. Error packet: It contains the Source id, Originator id of the node. A node k is said to have no downstream links if Hk < HNk,j for all non-NULL neighbors j∈Nk. Algorithm 2: Route Maintenance BEGIN Here 2 cases can occur: Case 1: When an intermediate node k detects the route failure, if it has an outbound link (Hk> HNk,j) i.e. another unexpired route exists in the cache, the route with better Path Preference Probability is selected for routing. Case 2: When an intermediate node detects the route failure, if it has no outbound link the following sequence of steps are performed: Step 1: The node generates an Error packet and sends to the source node and all intermediate nodes delete routes from their cache which contains that node. Step 2: As soon as source receives the error packet, it deletes routes from the cache which contain the node and if an unexpired route exists in the cache, the route with next better Path Preference Probability is selected for routing. Step 3: After sending the Error packet, the node where link failure occur, starts local link maintenance according to the following conditions: a. Generate: Node k has no downstream links due to link failure. ( k ,oidk, rk) = (t, k, 0), where t is the time of failure. ( k , k) = (0, k). Node k defines a new reference level, if k has no upstream neighbors, it sets Hk = NULL. Destination id(did) Height(Hk) Source id Originator id 0 15 31 0 15 31
• 12. International Journal of Computer Networks & Communications (IJCNC) Vol.5, No.4, July 2013 200 b. Propagate: Node k has no downstream links due to link reversal following receipt of an UPD and the ordered sets ( k ,oidk, rk) are not equal for all j ∈ Nk. ( k ,oidk, rk) = max {( k ,oidk, rk) | j∈Nk} ( k ,k) = {min { j | j∈Nk with ( j ,oidj, rj) = max {( j ,oidj, rj) } - 1, k}. Node k propagates the reference level of its highest neighbors and chooses a reference lower than all neighbors of that reference level. c. Reflect: Node k have no downstream links due to link reversal following receipt of an UPD packet and the sets ( j ,oidj, rj) are equal with rj =0 for all j∈Nk. ( k ,oidk, rk) = ( j ,oidj, 1) ( k , k) = (0, k). Node k reflects back the reference level by setting the r bit. d. Detect: Node i has no downstream links due to link reversal following receipt of an UPD packet and the sets ( j ,oidj, rj) are equal with rj=1 for all j∈Nk and oidk=k. ( k ,oidk, rk) = (_, _, _) ( k , k) = (_, k). Node k has detected a partition and route erasure phase invoked (described below). e. Generate: Node k has no downstream links due to link reversal following receipt of an UPD packet and the sets ( j ,oidj, rj) are equal with rj=1 for all j ∈Nk and oidj∈k. ( k ,oidk, rk) = (t, k, 0), where t is the time of failure. ( k , k) = (0, k). Node k experienced a link failure between the time it propagated a reference level and the reflected higher sub-level returned from all neighbors. This link failure required no reaction. Step 4: Finally, after performing step 2, step 3, if the cache contains no unexpired routes, again a new route discovery phase is started. END 6.3 ROUTE ERASURE PHASE Fig. 7. CLR packet format of a node CLR packet: It consists of destination id (did) and the reference level of node. It is used to erase invalid routes. Destination id(did) Reference level 0 15 31