2011 International Conference on Indoor Positioning and Indoor Navigation (IPIN), 21-23 September 2011, Guimarães, Portugal Synchronized Events in Mobile Systems Physically Nearby Nelson Marques * and Filipe Meneses ** Dept. of Information Systems, University of Minho Guimarães, Portugal * Email: a48064@alunos.uminho.pt ** Email: meneses@dsi.uminho.pt Abstract— The advances and convergence of information technology and communication technologies in mobile devices, enables the creation of ubiquitous applications for these devices. In this paper, we propose a system capable of producing a certain coordinate effect between the mobile devices of the spectators present at an event. Keywords— Mobile and Wireless Computing; Events; Location; Broadcast I. INTRODUCTION In this modem era, finding someone that doesn’t carry a mobile phone is increasingly an exception. With technological progress, in a short space of time, mobile phones have gone from devices designed to ensure only voice communication to open systems, capable of providing voice and video communications, sending and receiving messages, run applications, access to Internet and many others. When a space is filled with spectators to attend an event is common for people to carry out some choreography and chants, showing their support and appreciation to the athletes or performers. For example, normally in a football stadium, spectators raise their arms in a coordinated movement to produce a visual effect called “wave”. The purpose of this study is to develop a system that allows spectators at an event to be able to accomplish a particular coordinated effect through their mobile phones. For example, reducing the illumination of the stadium the spectators may put in the air their mobile phones and create “a wave”. The difference to the model with the arms in the air is that now the wave is created, for example, by turns on and off in a coordinated manner, the display or the keyboard of the mobile devices. II. CHALLENGES AND SOLUTIONS The proposed work present a number of challenges: getting an event spread in useful timing through a large number of mobile phones, getting the event to occur in a synchronized way, dealing with the heterogeneity of the devices in terms of operating systems, processing capabilities and communication. In order to implement an application there are several aspects that should be considered, as well as combined solutions that address the challenges. In this section, we discuss two possible approaches to solve the challenges of the presented work (figure 1). A. Ad hoc aproach The recent penetration of new technologies like Bluetooth (BT) and IEEE 802.11 in mobile devices enables the creation of Mobile Ad hoc Networks (MANET) [1]. In this kind of approach, the devices can freely and dynamically organize into network topologies arbitrary and temporary, enabling communication between them without the need for a pre-defined infrastructure [2]. In this particular case, viewers/users only need to be within range for participate in the event. Unlike other technologies of information transmission, BT provides direct information to all persons who are in the area instead of a group of known people. One of the disadvantages of combining the BT technology with this model is the great complexity of the nodes forming the network. Despite the maturity of BT, the initial connection, even in the newer versions, are still consuming too much time [2] [3] [5] and even after a connection is establish, each device has it’s way of dealing with incoming messages [6]. Besides that, the union of the ad hoc model with BT technology is likely to partitioning the network. B. Approach with infrastructure These networks are configured so that the nodes can’t communicate directly with each other, making the communication only with access points. A node wishing Figure 1: (A) Ad hoc approach. (B) Approach with infrastructure.