On The Media Access Control Protocols For Ad Hoc Networks With MIMO Links

Ad Hoc networks do not need the support of any fixed infrastructure and can groupnetworks flexibly, thus is promising technology for future communication networks.However, with the advantage of flexibility and low cost, Ad Hoc networks still faces severechallenges in technical realization. As the key technologies related to Ad Hoc networks arecomprehensive, there are quite a number of problems that are open. Among the keytechnologies, Media access control(MAC) protocols mainly solve the problems ofaccessing the sharing wireless channel, and its performances directly affect the transmissionefficiency. The introduction of Multiple Input Multiple Output(MIMO) technology to AdHoc networks has brought new resources and put forward some new requirements for thedesign of MAC protocols. In this thesis, we study the MAC protocols for Ad Hoc networkswith MIMO technology, and our main contributions are as follows:(1)Combing the contention-based protocol PRP MAC and reservation based protocolFPRP, a hybrid protocol FPR-PRP MAC is proposed. FPR-PRP adopts a synchronous timestructure, and allows the nodes acquire transmission slot numbers through five phasereservation. Then in information slots, some nodes can transmit RTS packets with higherpriority according to the reservation results, and other nodes contend with each other totransmit RTS packets. A receiving node determines the maximum allowable number of datastreams according to all the RTS packets it received, and put this number in the CTS packetto reply the transmitter. The mechanism of combing reservation with contention inFPR-PRP MAC reduces the collisions of RTS packets in the network. Moreover, thesynchronous time structure eliminates the collisions of control packet and data packet.Therefore, the proposed FPR-PRP MAC can transmit much more packets instream-controlled way, and increase the network throughput.(2) Based on protocol threading technique, a node activation topology-transparentMAC MIMO-T-TTMA is proposed for MIMO link Ad Hoc networks. It combines a timespread multiple access protocol and a TDMA protocol in time-sharing mode. The nodes inthe networks determine the number of data streams to be transmitted through exchange ofRTS/CTS packets. When RTS/CTS exchange fails or in non-assigned slots, the node also transmits one stream according to some probability, with the expectation of improving theslots utilization. MIMO-T-TTMA eliminates the transmission failure when the networksmax degree increases, moreover, it has higher throughput when max degree is relativelylarge, thereby it adapts to Ad Hoc networks with changing topologies.(3) A link activation topology-transparent MAC MIMO-LATTMA is proposed for AdHoc networks with MIMO links. The protocol allocates transmission slots for each link inthe networks based on the theory of orthogonal Latin squares, so that each link cansuccessfully transmit its data streams in at least one slot in a frame. The average throughputof the protocol is deduced through theoretical analysis. To maximize the averagethroughput, a method of searching the optimal protocol parameters is also derived.Numerical results show that, MIMO-LATTMA can increase the throughputs of networknodes.(4) A centralized TDMA protocol E-MIMO-CTDMA is proposed for MIMO link AdHoc networks, which can make full use of MIMO spatial multiplexing(SM) to improve thenetwork performances. Specifically, by utilizing the SM in the initial slot allocation phase,E-MIMO-CTDMA can reduce the scheduling frame length. Moreover, allows networknodes to transit more streams in a slot further exploit the SM thoroughly. The throughputand delay of E-MIMO-CTDMA are derived via the theoretic analysis. Evaluation resultsshow that, E-MIMO-CTDMA can increase the network throughput and reduce the averageand maximum delay.(5)A distributed adaptive TDMA protocol MIMO-DATDMA is proposed for MIMOlink Ad Hoc networks. By carefully considering MIMO SM and reasonably allocating slotsand streams for each node, MIMO-DATDMA can ensure collision-free transmission for allthe nodes when network topology dose not change. While new nodes’ appearance or nodes’mobility changes the network topology, MIMO-DATDMA can quickly discover thetopology changes, and adjust the slots and streams of a portion of nodes, evenly making thenetwork resume the collision-free state. Simulation results show that, by making full use ofthe MIMO’s advantages, MIMO-DATDMA can evidently reduce the time needed foradjusting the network parameters.