| Ad-hoc network is composed by a number of mobile terminals, it is a temporary and autonomous network, and due to its flexibility in the formation and dissolution, so,ad hoc network has great value in temporary scenes. Researches show that ad-hoc which is planar in structure is poor in development, and when the number of nodes increase,it will reduce the throughput of network, while clustering network structure can facilitate the management, and clustering structure having strong advantages in expansion, robust, resource consumption, and the MAC(Medium Access Control) protocol based on CSMA(Carrier Sense Multiple Access) due to the nature of its random access, can not resolve the conflict fundamentally, the MAC protocol based on TDMA(Time Division Multiple Access) has less conflict and higher channel utilization. This thesis researchs clustering algorithm and slot allocation strategy, designs clustering algorithm which is stable, strategy which has high degree of multiplexing in time slot allocation. In addition, introducing the directional antennas in ad hoc networks can improve the quality of transmission link, improve network performance, reduce signal interference, this thesis researchs directional antenna in access control, designs access control protocol for certain scenarios.This thesis paper researchs clustering algorithm and slot allocation policy based on the ominidirectional antenna pattern, it includes two parts. In the first part, the application scenarios is that the distance between clusters is long, clusters can only communicate with each other by the head nodes, thesis uses coloring algorithm to allot the time slots, uses LID(lowest ID) algorithm to cluster the nodes, then, thesis realizes the simulation for the clustering algorithm and slot allocation policy, it shows that the clusters is stable, the alrgorithm has high degree of multiplexing in time slot allocation. For the second part, as for the LID algorithm does not consider the mobility of node, the energy of node, the degree of node, thesis designs a clustering algorithm which considers the mobility, energy and degree, thesis also optimizes the situation that the head node changes, algorithm allows clusters communicate by head nodes. For the slot allocation strategy, algorithm has a fixed and total slot allocation, algorithm also has a independent slot allocation for each cluster. The simulation shows that the overhead is low, the energy is balanced, the cluster is stable and has high degree of multiplexing in time slot allocation.This thesis also researchs the case that the node has directional antenna and omnidirectional antenna simultaneously, thesis designs a MAC protocol based on a hybrid antenna, the protocol allots nodes that are not in conflict to the same slots. Algorithm uses omnidirectional antenna to broadcast the messages, uses directional antenna to determine the links and avoid the conflict. Algorithm also consider the fairness. The simulation shows that the algorithm has more throughput, smaller delay and better fairness than others.This thesis considers the case that nodes only have directional antenna, thesis designs the MAC protocol. Protocol has a strict requirements in network structure, it adapts to reticular network structure. The node in protocol has four directional antennas, by sending and receiving messages in turn, protocol reserves the slot time, insuring the transmission is conflict-free. Protocol mainly considers the wrong data and time slot multiplexing. The simulation shows that the protocol has bigger throughput than others and handle the wrong data well. |
