Dynamic Virtual Flows Allocation Algorithm In Collision Resistant Multiple Access

Collision Resistant Multiple Access (CRMA) to conduct multiple access problemsis a new kind of spectrum shared protocol. The network using this protocol transmitby natural coding at orthogonal channels during the wireless transmission and re storesthe information at receivers so that it needn’t sense if the channel is occupied,prominent improving the throughput and reducing the cost. The virtual flowtechnology, the core technology in the Collision Resistant Multiple Access,contributes mostly to this highly performance of the CRMA-protocol.This thesis expounds details of the CRMA and proposes two kinds of dynamicvirtual flow allocation algorithm to the problem of virtual flow. The main works areas follows:First, this thesis analyses the main idea of CRMA, discovering that the efficiencyreduction of transmission is caused by dynamic network and increasing physical flow.Algorithms should satisfy the following requirements to handle throughputdegradation. Firstly, algorithms should adaptively coordinate access of flows andmake sure that a few physical flows exist in the network. Secondly, the algorithmshould coordinate the access of physical flows and increase virtual flows.Second, the thesis proposes a first-come-first-service algorithm. The basic idea ofthe algorithm is that there are only two physical flows transmitting in the network andthey occupy all channels. If a new flow accesses the network, the decoding would befailed. Thus, the network could utilize the decoding failure to discover the access ofthe new flow and start rollback course. The senders resend signal including theStarting time of mission by CRMA without virtual flows. After receivers decode, theysend ACK with Starting time of missions to senders. The sender wo uld sendoccupying half channel resources with virtual flow if the node discovers that it is theone of first two earliest flows. Otherwise, it should stop to wait. The simulation resultshows that the throughput of first-come-first-service algorithm out-performs virtualflow technology by22%.Third, correlating the advantage of the least flow with virtual flow for maximumthroughput when only one flow transmits occupying all channels in network, the leastflow priority algorithm has been proposed in this thesis. The basic idea of thealgorithm is that there are only two physical flows transmitting in the network and they occupy all channels. If a new flow accesses the network, the decoding would befailed. Thus, the network could utilize the decoding failure to discover the access ofthe new flow and start rollback course. Senders resend signal including the volume ofthe rest of data by CRMA without virtual flows. After the receivers decode, they sendVirtual Flow ACK to notice the two senders with the minimum data volume to occupyall channels with virtual flow technology, at the same time, send wait ACK withwaiting time t to other senders. The receivers received the wait ACK wait to sendsignal until the wait time is over. Virtual flow allocation algori thm increases virtualflows and decreases physical flows to make the most of channels improvingthroughput. The experiment results show that the throughput of the least flow priorityalgorithm out-performs first-come-first-service algorithm by13%and out-performsvirtual flow technology by35%.