通过微型时隙接入优化多AP住宅宽带连接中的TCP性能
Optimizing TCP Performance in Multi-AP Residential Broadband Connections via Mini-Slot Access
摘要：
互联网应用的高带宽需求最近推动了提高住宅下载速度的需求。已经提出了对该问题的实际解决方案，即经由802.11连接聚合范围内的802.11接入点（AP）回程的带宽。由于802.11设备通常是单无线电，因此在不同无线电信道上与多个AP的通信需要在客户端站点处引入时分多址（TDMA）策略。目前在这方面的研究假设，有足够数量的TCP流饱和的非对称数字用户线（ADSL）背后的AP。然而，根据用户业务模式，这可能无法保证。因此，TDMA策略在端到端传输中引入了额外的延迟，这将导致TCP吞吐量的降低和AP回程的利用不足。在本文中，我们首先进行了深入的实验分析与定制的802.11驱动程序的多AP TDMA的使用如何影响观察到的TCP流的往返时间（RTT）。然后，我们介绍了一个简单的分析模型，准确地预测TCP RTT时，访问无线介质与多AP TDMA政策。基于此模型，我们提出了一个资源分配算法，在本地运行的工作站，它大大减少了观察到的TCP RTT与一个非常低的计算成本。我们提出的方案可以提高高达1：5倍的总吞吐量观察站相比，国家的最先进的多AP TDMA分配。我们还表明，该算法的吞吐量性能是非常接近的理论上限在关键的模拟场景。
英文摘要：
The high bandwidth demand of Internet applications has recently driven the need of increasing the residential download speed. A practical solution to the problem has been proposed aggregating the bandwidth of 802.11 Access Points (APs) backhauls in range via 802.11 connections. Since 802.11 devices are usually single-radio, the communication to multiple APs on different radio-channels requires the introduction of a time-division multiple access (TDMA) policy at the client station. Current investigation in this area supposes that there is a sufficient number of TCP flows to saturate the Asymmetric Digital Subscriber Line (ADSL) behind the APs. However, this may be not guaranteed according to the user traffic pattern. As a consequence, a TDMA policy introduces additional delays in the end-to-end transmissions that will cause degradation of the TCP throughput and an under-utilization of the AP backhauls. In this paper, we first perform an in-depth experimental analysis with a customized 802.11 driver of how the usage of multi-AP TDMA affects the observed Round-Trip-Time (RTT) of TCP flows. Then, we introduce a simple analytical model that accurately predicts the TCP RTT when accessing the wireless medium with a Multi-AP TDMA policy. Based on this model, we propose a resource allocation algorithm that runs locally at the station and it greatly reduces the observed TCP RTT with a very low computational cost. Our proposed scheme can improve up to 1:5 times the aggregate throughput observed by the station compared to state-of-the-art multi-AP TDMA allocations. We also show that the throughput performance of the algorithm is very close to the theoretical upper-bound in key simulation scenarios.
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