Crowd (Soft) Control Moving Beyond The Opportunistic John Rula and Fabián E. Bustamante Northwestern University {john.rula|fabianb}@eecs.northwestern.edu ABSTRACT A number of novel wireless networked services, ranging from participatory sensing to social networking, leverage the increasing capabilities of mobile devices and the movements of the individuals carrying them. For many of these systems, their effectiveness fundamentally depends on coverage and the particular mobility patterns of the participants. Given the strong spatial and temporal regularity of human mobility, the needed coverage can typically only be attained through a large participant base. In this paper we explore an alternative approach to attain cover- age without scale – (soft) controlling the movement of participants. We present Crowd Soft Control (CSC), an approach to exert limited control over the temporal and spatial movements of mobile users by leveraging the built-in incentives of location-based gaming and social applications. By pairing network services with these location-based apps, CSC allows researchers to use an application’s incentives (e.g. game objectives) to control the movement of participating users, increasing the effectiveness and efficiency of the associated network service. After outlining the case for Crowd Soft Control, we present an initial prototype of our ideas and discuss potential benefits and costs in the context of two case studies. 1. INTRODUCTION A large class of novel wireless networked services, ranging from delay-tolerant networking [3, 25], to digital geo-tagging [24] and participatory sensing [4,9,14], leverages the increasing capabilities of mobile devices and the movement of the individuals carrying them. Whether aimed at providing connectivity in challenging settings, entertainment, or support for citizen science, the effec- tiveness of these proposed systems depends on coverage that can typically only be attained through a critical mass of participants. For instance, several projects have explored the use of data carriers to bridge the gaps in intermittently connected mobile networks [3, 7, 25]. To effectively overcome the lack of end-to- end connectivity, the proposed approaches must either assume a large participatory base or introduce some form of control over the mobility of participants. In the context of community sensing, Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. HotMobile’12 February 28–29, 2012, San Diego, CA, USA. Copyright 2012 ACM 978-1-4503-1207-3 ...$10.00. accurately characterizing a distributed phenomena, such as pollu- tion levels or vehicular road conditions, similarly requires sufficient coverage to capture the variations of the metrics of interest across space and over time. The uncoordinated movement of participants, with typically strong spatial and temporal regularity [5], however, means that certain areas of potential interest may not be covered or the collected data may never reach its destination due to limited connectivity. Recently, a number of research efforts have proposed addressing this problem by using either the social networks of large popula- tions or their previously recorded mobility patterns [8, 12, 18]. Hui et al. [8], for instance, suggests leveraging participants’ social net- work connections to predict movements; these predictions are then used to aid data forwarding decisions in delay tolerant networks (DTNs). Reddy et al. [18] proposes building a recruitment system for participatory sensing based on a large participant base and their previously collected mobility traces. Thus, by carefully selecting participants from a sufficiently large pool based on their recorded movements or social network, a researcher can piece individual mobility patterns together into a quilt of the necessary coverage. In this paper, we present an alternative approach to attain coverage without scale by (soft) controlling the movement of participants. We introduce Crowd Soft Control (CSC), an approach to exert limited control over the temporal and spatial movements of mobile users by leveraging the built-in incentives of location-based gaming and social applications. Location-based applications rely on users’ position and orientation to enhance their game play or social networking experience. For instance, a class of games known as augmented reality games use a mobile device’s GPS location along with its camera and compass to overlay virtual information on top of a user’s camera view [23]. Social networking games like Foursquare 1 and Gowalla 2 encourage users to “check-in” at locations to alert their friends to their whereabouts and collect virtual rewards. We argue that by leveraging the incentives of such location-based applications (e.g. offering bonus points for visiting a certain location), users’ actions can be manipulated to achieve a network service’s goal (e.g. taking a measurement at that location). The following section expands on the case for Crowd Soft Con- trol and provides an overview of a general architecture. Sections 3 and 4 present an initial prototype of our ideas and illustrate them using two case studies. We review related work in Sec. 5 and discuss open issues and future work in Sec. 6 and 7. 1 foursquare.com 2 gowalla.com