Cellular and Wi-Fi networks now form a global substrate that provides billions of mobile phone users with consistent, location-aware communication and multimedia data access. On this substrate is emerging a new class of mobile phone applications that use the phones location, image and acoustic sensors, and enable people to choose what to sense and when to share data about themselves and their surroundings. Peoples' natural movement through and among living, work, and ldquothirdrdquo spaces, provides spatial and temporal coverage for these modalities, the character of which is impossible to achieve through embedded instrumentation alone. This paper proposes a network service architecture for participatory sensing, describing challenges in (1) network coordination services enabling applications to efficiently select, incentivize and task mobile users based on measures of coverage, capabilities and interests; (2) attestation mechanisms to enable data consumers to assign trust to the data they access; and (3) participatory privacy regulation mechanisms used by data contributors to control what data they share.

SMS has been arguably the most popular wireless data service for cellular networks. Due to its ubiquitous availability and universal support by mobile handsets and cellular carriers, it is also being considered for emergency notification and other mission-critical applications. Despite its increased popularity, the reliability of SMS service in real-world operational networks has received little study so far. In this work, we investigate the reliability of SMS by analyzing traces collected from a nationwide cellular network over a period of three weeks. Although the SMS service incorporates a number of reliability mechanisms such as delivery acknowledgement and multiple retries, our study shows that its reliability is not as good as we expected. For example the message delivery failure ratio is as high as 5.1% during normal operation conditions. We also analyze the performance of the service under stressful conditions, and in particular during a "flash-crowd" event that occurred in New Year's Eve of 2005. Two important factors that adversely affect reliability of SMS are also examined: bulk message delivery that may induce network-wide congestion, and the topological structure of the social network formed by SMS users, which may facilitate quick propagation of viruses or other malware.

In recent years, cellular networks have experienced an astronomical increase in the use of Short Message Service (SMS), making it a popular communication means for inter-personal as well as content provider-to-person usage. Yet little is known about the traffic and message user behavior in real SMS systems. In this paper, we present a measurement study of SMS based on traces collected from a nationwide cellular carrier during a three-week period. We characterize message traffic at both the message level and the conversation thread level. We also examine the "store-and-forward" mechanism of SMS and present initial measurements on how messages are actually delivered.