SIR Based Time Slot Multiplexing Algorithm In Multi-hop Ad Hoc Networks

A mobile ad hoc network has no need of fixed network infrastructures, and can quickly build a network platform for military or civilian applications. In recently years, the requests for real-time and interactive services have increased continuously, and put forward the requirement for high performance mobile ad hoc networks. Although the rapid progress on OFDM and MIMO technologies has laid the foundation to enhance the performance of a mobile ad hoc network, an efficient MAC protocol becomes the key to improve network performance due to the fact that the wireless channel is a broadcast media and is vulnerable to interference.Generally, MAC protocols in mobile ad hoc networks are classified into competitive, allocated and mixed ones. For the allocated MAC protocols, dynamic time slot allocation protocols have the advantage of high channel utilization, which make them become hot research topics in distributed TDMA protocols. In the traditional distributed time slot allocation mechanism, time slots are assigned to nodes. In order to avoid receiving conflict, that a time slot can only be successfully reserved by a node in two hop range is requested. This constraint leads to a time slot in two hop range only has a transmission link, which causes a large waste of time slot resources. This paper proposes an algorithm named SIR based Time Slot Multiplexing Algorithm(SIR-TSMA). The algorithm uses SIR channel sensing technology and requests a reservation node to make access test for its link in time slot resource set one by one. If the test link meets the coexistence conditions with links existed in the time slot, the node would reserve the time slot so as to obtain an alternative time slot subset. This is a reservation mechanism based on the coexistence of links, which assigns slots to links. The characteristic of the algorithm introduces a higher link degree of parallelism in each time slot, which improves the network throughput. The algorithm requires to select a time slot with the largest average SIR ratio to access link in the time slot subset, which can improve the network throughput compared with random selection. For different priority services, nodes can give priority to the access test of high priority services, the algorithm provides a great convenience for this.Firstly, the MAC protocol design of SIR-TSMA algorithm and the physical layer design based on OFDM are completed in this paper. Among them, the physical layer based on FPGA development is completed, all modules use HDL Verilog language. The simulation tests for the full frequency channel and single frequency channel are also completed. Secondly, based on the Linux development platform, the simulation system design for the SIR-TSMA algorithm is completed. The performance of the network is simulated, and the feasibility of the algorithm is verified, and the superiority of the proposed algorithm is showed compared with traditional time slot allocation algorithms. Finally, some characteristics of the new algorithm are verified in simulation system.