Journal of Emerging Technologies in Web Intelligence Contents

92 JOURNAL OF EMERGING TECHNOLOGIES IN WEB INTELLIGENCE, VOL. 2, NO. 2, MAY 2010source. These can be generalized into a single equationwith both the source and receiver moving as given below:⎡ v ⎤f = ⎢ − srr f e 1 ⎥(11)⎣ v + v sr ⎦Where v sr is the source to receiver velocity radialcomponent. Now since the source nodes have equalpower so frequency of transmission will remain same forall the nodes within the vicinity. From (11) above we getthe velocity of the neighboring nodes as⎡ f − f ⎤v = e rsr v⎢⎥(12)⎣ f r ⎦Now overall time period for which the link remainsestablished will depend on the following relationdT = (13)v srwhere T in (13) is defined as the time period for whichthe link with the neighboring node will remainestablished. The time period depends on d because if thenode covers the maximum distance away from the othernode, then a small velocity of it in the opposite directionwill disconnect the link. The time T will be more if it isnegative as the velocity will be having +ve or –ve signdepending upon the direction of motion.C. Signal QualityThe distance, and position plays an important role infinding mobility and hence the link stability. However,the stability of the link also depends on the quality ofsignal as well. In Mobile Adhoc Networks (MANETs)the signal quality plays an important role in selecting theroute to the destination. The parameters like distance andmobility proposed above effects the signal quality,however in spite of the feasible distance and mobilitythreshold values, the node may not receive from theneighboring node the good quality signal due to noisysurroundings. When there is a signal transmission from anode with certain power in the noisy environment, the Biterror rate of the signal increases apart from the normalpath loss in the medium. The receiver on the basis of thereceiver sensitivity, and the threshold Signal to NoiseRatio (SNR), predicts the quality of signal. Overall it isthe Receiver signal strength indicator (RSSI) whichprovides the details of the quality of signal received.RSSI which is basically a measurement of how well theradio is receiving or 'hearing' data to determine thequality of signal received. It's typically measured in -dBm, which is the power ratio in decibel (dB) of themeasured power referenced to one milliwatt (mW).Normally in the real testing environments the RSSI above-60 dB is considered the threshold required to performgood networking functions and any value higher than thatis the stable value. We denote this value by .Therefore overall link stability which is denoted by L SSOshould satisfy L S , T and M RSSI the three importantparameters to determine the stability of the route.IV. ROUTINGThe above parameters calculated can be used to enhancethe routing procedures already available. To incoorporatethe changes, the nodes needs to be modified.Below are the node level modifications suggested whenthe node behaves as, the intermediate and the destinationnode.A. Intermediate node operationWhen the intermediate node receives the RREQ packetfrom the source or from any of its neighbors it providesthe additional information of the distance and thefrequency in the RREQ packet and forwards it to thedestination. The Algorithm 1 provides the operationaldetails to be performed at each intermediate node.Algorithm 1 Algorithm to be executed in the node1 Set , (m, n), M RSSISet k stable link time threshold2 Measure d3 if d < µ L s = 1 Goto xElse d > µ L s = 0 stop.3 x: calculate RSSI4 if RSSI < M RSSI goto 8 else5 calculate v sr5 if vsr -ve calculate TElse if +ve calculate T6 if T < k reject6 Else if T > k select and modify RREQ7 stopB. Destination node operationThe destination node on receiving RREQ packets fromthe several nodes sends the reply to the source byselecting the best path on the basis of the T, M RSSI value.Algorithm 2 provides the process details of thedestination node when RREQ arrives from differentnodes of the destination node.Algorithm 2 Process execution when RREQ arrives1 Analyze RREQ2 Extract, d, v sr M RSSI*3 Compared with d* and M RSSI with M RSSI * and v sr with v sr*4 if d > d* and M RSSI < M RSSI*and v sr > v sr*Reject RouteElse select RouteThe source node when sending the RREQ packet,calculates before, the distance, mobility and SNR of theneighboring nodes. It then embeds the information in theRREQ packet and sends it to the destination via. Nexthop neighbor.© 2010 ACADEMY PUBLISHER