混合RF/FSO DTN中的最优多播
Optimal Multicasting in Hybrid RF/FSO DTNs
摘要：
延迟容忍网络（DTNs）中的多副本路由模式意味着增加联系带宽会导致数据传输延迟的减少和吞吐量的提高。利用混合射频/自由空间光（RF/FSO）PHY层，高数据率FSO链路可用于增加接触带宽。然而，由于FSO链路的高度定向性，广播是困难的。增加波束发散角以在广播集中包括许多节点的朴素广播策略导致低数据率，并且不总是导致最小可实现延迟。在这项工作中，我们开发了一个最佳的多播算法的混合RF/FSO网络。我们表明，这个问题是一个抽象的最小重量集覆盖问题，这是已知的NP-难。提出了一种计算量小的贪婪局部最优启发式算法。使用延迟，吞吐量和计算时间作为度量的综合评估使用各种解决方案进行。这些广泛的评估表明，我们的解决方案优于天真的广播和多个单播，需要95%的时间相比，确切的算法，同时提供相当的性能。
英文摘要：
The multi-copy routing paradigm in Delay Tolerant Networks (DTNs) implies that increasing contact bandwidth leads to a decrease in data delivery delay and an improvement in throughput. With Hybrid Radio Frequency/Free Space Optical (RF/FSO) PHY layers, the high data rate FSO links can be used to increase the contact bandwidth. However, due to the highly directional nature of FSO links, broadcasting is difficult. A naive broadcast strategy where the beam divergence angle is increased to include many nodes in the broadcast set results in low data rate, and does not always result in the minimum achievable delay. In this work we develop an optimal multicast algorithm for hybrid RF/FSO networks. We show that the problem is an abstraction of the minimum weight set cover problem which is known to be NP-hard. A computationally cheap greedy local optimum heuristic is proposed. A comprehensive evaluation using delay, throughput and computation time as metrics is performed using various solutions. These extensive evaluations show that our solution outperforms both naive broadcast and multiple unicast, taking 95% less time as compared to the exact algorithm, while providing comparable performance.
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