In Vivo Characterization of a Wide area 802.11b Wireless Seismic Array
In Vivo Characterization of a Wide area 802.11b Wireless Seismic Array
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发表时间：
2007-05
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通讯作者：
M. Lukac;V. Naik;I. Stubailo;A. Husker;D. Estrin
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作者：
M. Lukac;V. Naik;I. Stubailo;A. Husker;D. Estrin
使用802.11b远程链路的无线传感器网络使领域科学家能够实时测量物理现象，并在具有科学意义的范围内进行测量。虽然在这种情况下的部署正在增加，但缺乏对网络吞吐量的表征，这使得很难预测在这些类型的网络上的传感应用的性能。研究了分布在山区、山谷、农村平原和城市环境中的节点组成的MASE地震数据采集网络。该网络全长250公里，链路长达43公里，已连续运行2年多。本文的贡献有三个方面：(A)我们给出了网络运行中无线链路的吞吐量特征，(B)我们建议了无线参数的设置以提高网络的性能，以及(C)我们记录了节点的正常运行时间和网络的数据产量。我们的发现对未来使用802.11b的无线传感器网络部署的设计是有益的。在我们广泛变化的网络设置中，我们发现，虽然信噪比与吞吐量或距离无关，但吞吐量与距离大致相关，并且不会随着时间的推移而显著变化。在链路层，启用RTS-CTS握手会降低吞吐量，而启用重试会提高吞吐量。此外，用于传输比特率的默认的基于阈值的速率自适应算法是次优的。我们发现，大多数故障案例是由于系统问题而不是网络问题造成的。在8个月的时间里，数据收益率为78%。
Wireless sensor networks using 802.11b long-distance links enable domain scientists to measure physical phenomena in real time and at a scientifically meaningful scale. Although deployments in this setting are increasing, a characterization of the network- throughput is lacking which makes it difficult to predict the performance of sensing applications on these types of networks. We present a study of the MASE seismic data collection network which includes 64 nodes spread across mountains, valleys, rural plains, and urban environments. The network spans 250km with links as long as 43km and has been operating continuously for more than 2 years. The contributions of this paper are three fold: (a) we present a throughput characterization of wireless links for a network in operational use, (b) we suggest settings for the wireless parameters to improve the performance of the network, and (c) we document the uptime of the nodes and the data yield of the network. Our findings are beneficial for the design of future wireless sensor network deployments using 802.11b. In our networks widely varied settings, we find that while signal-to-noise ratio is not correlated with throughput or distance, throughput is roughly correlated with distance and does not change significantly over time. At the link-layer, enabling the RTS-CTS handshake decreases the throughput while enabling retries improves the throughput. In addition, the default threshold-based rate adaptation algorithm for the transmission bit-rate is suboptimal. We find that the majority of fault cases are due to system issues and not network issues. The data yield over the course of an eight month period was 78%.