Embedding sensors in urban buses is a promising strategy to deploy city-wide wireless sensor networks. By taking advantage of the mobility of buses, it is possible to achieve extended spatial coverage with fewer sensors as compared to a static setup. The trade-offs are that urban buses only cover part of the city, and that the frequency of the buses, and consequently of the data collection, is inhomogeneous across the city. Depending on the communication technology, buses may be unable to deliver the collected data on time. In this paper, we propose a coverage metric that takes into account the delivery delays of sensed data and the frequency at which a given region is sensed. The metric indicates, for a given time window, the proportion of streets that can be sensed under the requirements of an application. We apply the metric to more than 19 million GPS coordinates of 5,706 buses in Rio de Janeiro, mapping the coverage achieved for different application needs during a week. We build an abacus relating the coverage to different application requirements. We also calculate the coverage of a scenario only with static sensors. We show, among several observations, that bus-based sensing increases the coverage of applications by up to 7.6 times, in the worst case analyzed, when compared to a pure static scenario.

在城市公交车中嵌入传感器是部署城市范围的无线传感器网络的有前途的策略。与静态设置相比，通过利用总线的移动性，可以用更少的传感器实现扩展的空间覆盖。权衡取舍的是，城市公交车仅覆盖部分城市，并且公交车的频率以及因此的数据收集在整个城市中是不均匀的。取决于通信技术，总线可能无法按时交付收集的数据。在本文中，我们提出了一种覆盖率指标，该指标考虑了感测数据的传递延迟和给定区域被感测的频率。该度量标准针对给定的时间窗口指示在应用程序要求下可以感知的街道比例。我们将该度量标准应用于里约热内卢的5,706辆公交车的1900万个GPS坐标上，绘制了一周内满足不同应用需求的覆盖范围。我们建立了一个算盘，将覆盖范围与不同的应用程序需求联系起来。我们还仅使用静态传感器来计算方案的覆盖范围。在一些观察结果中，我们显示，与纯静态方案相比，基于总线的传感在最坏的情况下，将应用程序的覆盖范围提高了7.6倍。