4290

4061

كارشناسي ارشد

مخابرات

اصفهان : دانشگاه صنعتي اصفهان، دانشكده برق و كامپيوتر

1387

هشت، 112، [II] ص. : مصور، نمودار

ص.ع. به: فارسي و انگليسي

مهدي مهدوي

حسين سعيدي

23/7/1387

پژمان خديوي، مسعود رضا هاشمي

مهندسي برق و كامپيوتر

ID4061

به فارسي و انگليسي: قابل رويت در نسخه ديجيتال

AbstractTCP protocol has been widely used on the internet TCP responds to the channel conditionand the traffic of the network dynamically adjust the data rate injected to the networkeffectively and provides a reliable connection The characteristics of TCP render for itswide spread usage in many applications and encourages the use of this protocol in wirelessAd Hoc networks TCP protocol has many challenges in Ad Hoc networks as it wasoriginally designed for wired networks Every time that a packet is lost TCP concludesthat there is congestion in the network which is not always correct in Ad Hoc networks InAd Hoc networks reasons like lossy channel contention in wireless medium and linkbreakage due to node mobility cause packet loss Every time a packet is lost due to one ofthese reasons TCP slows down and reduces size of congestion window which leads tothroughput degradation although the reason for packet loss is not congestion In this thesisthe goal is to reduce the number of acknowledgement generated by the receiver in order toreduce contention between data packets and Acks So collisions will be reduced andthroughput is increased This idea aims to mitigate the hidden terminal problem in thenetworks which are based on IEEE 802 11 protocol like Ad Hoc networks In order toreduce number of Acks at the receiver four techniques will be evaluated and simulatedusing NS2 network simulator All techniques are implemented in two different scenarios 1 SANET 2 MANET In MANET scenario throughput is calculated for different speedsand in SANET scenario throughput is calculated for chains of hops of different length Also in SANET scenario number of TCP connections between sender and receiver arechanged Then performance of all techniques is compared with original TCP algorithm Anew technique for delaying and reducing ACKs at the receiver will be proposed whichestimates channel condition and changes the rate of ACKs accordingly In the proposedtechnique ACK rate is changed in an efficient way and TCP congestion window canincrease faster to obtain better throughput The new technique will be also simulated usingNS2 compared with the other four techniques and the improvement will be shown

مهدي مهدوي

حسين سعيدي

پژمان خديوي، مسعود رضا هاشمي