矿井Mesh无线多跳路径流内竞争分析及约束方法

Analysis and constraint methods for intra-flow contention in multi-hop paths of wireless mesh networks in mines

  • 摘要: 针对现有无线Mesh网络的多跳带宽无法支撑实时音视频类大通量业务的问题,分析了矿井Mesh无线多跳路径流内竞争机制,揭示了多跳带宽损失机理。指出大于6跳的多跳中继系统存在最优收敛比,具备约束多跳带宽1/nn为链路数量下降趋势的可能性,小于等于6跳的多跳中继系统不能约束1/n下降趋势。决定多跳中继系统存在最优收敛比的关键因素是载波侦听距离与稳定通信距离之比ΔS:当路径节点按ΔS=2均匀分布时,多跳带宽存在最优收敛比1/6;由于矿井无线传输的分界特性,ΔS≈3,导致矿井内路径节点均匀分布时的多跳带宽最优收敛比为1/8;矿井无线覆盖的不对称、不稳定特性造成节点不能均匀分布,因此模拟矿井 10 跳路径的多跳带宽最优收敛比为1/5。基于约束竞争范围的思想,提出异频分段串联混合组建链状网络的方法,在不修改Mesh协议的条件下,利用频率分割路径使流内竞争范围约束在各条路径内。实验结果表明,当无线链路数量大于10跳时,链状网络的首末带宽大于传统Mesh多跳路径的多跳带宽,同时收敛比也大于1/n,验证了该方法约束多跳带宽1/n下降趋势的可行性。

     

    Abstract: To address the issue that the multi-hop bandwidth of existing wireless Mesh networks cannot support real-time, high-throughput services such as audio and video in mines, the intra-flow contention mechanism of multi-hop paths in mine wireless Mesh networks was analyzed, revealing the mechanism of multi-hop bandwidth degradation. It was pointed out that multi-hop relay systems with more than six hops have an optimal convergence ratio, which can potentially constrain the 1/n (n being the number of links) bandwidth degradation trend. However, systems with six or fewer hops cannot constrain this trend. The key factor determining the existence of an optimal convergence ratio is the ratio ΔS between the carrier sensing distance and the stable communication distance. When path nodes are uniformly distributed with ΔS=2, the optimal convergence ratio is 1/6. Due to the unique boundary characteristics of wireless transmission in mines, ΔS≈3, resulting in an optimal convergence ratio of 1/8 when nodes are uniformly distributed. However, the asymmetric and unstable nature of wireless coverage in mines prevents uniform node distribution. Therefore, for a 10-hop path in a simulated mine, the optimal convergence ratio is 1/5. Based on the idea of constraining the contention range, a method of constructing a chain network using frequency-division segmented serial hybrid links was proposed. Without modifying the Mesh protocol, this method constrained intra-flow contention within each path segment by splitting the path using different frequencies. Experimental results showed that when the number of wireless links exceeded ten hops, the bandwidth between the first and last nodes in the chain network was greater than the multi-hop bandwidth of traditional Mesh paths, and the convergence ratio also exceeded 1/n, validating the feasibility of the proposed method in constraining the 1/n bandwidth degradation trend.

     

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