Wireless Community Networks: an Alternative Approach for Nomadic Broadband Network Access
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FRANGOUDIS LAYOUT 4/20/11 2:11 PM Page 206 ACCEPTED FROM OPEN CALL Wireless Community Networks: An Alternative Approach for Nomadic Broadband Network Access Pantelis A. Frangoudis and George C. Polyzos, Athens University of Economics and Business Vasileios P. Kemerlis, Columbia University ABSTRACT forming a scan for wireless network presence in such a setting reveals so high a number of wire- Low-cost wireless LAN equipment operating less access points (APs) in the neighborhood in unlicensed spectrum has revolutionized local that we should be more concerned about inter- area communications, introducing novel schemes ference than coverage. AP density in metropoli- for open wireless connectivity and even new tan areas has made it possible to build a business business models. The ease of deployment of based just on their existence and not their com- Wi-Fi has made it ubiquitous in densely populat- munication capabilities [1]. ed urban areas, and it was just a matter of time Wireless Community Networks (WCNs) have before wireless communities emerged. Using been developed as grassroots movements of inexpensive wireless technology to communicate, WLAN enthusiasts, who use inexpensive net- autonomous wireless internetworks have been working equipment for free interconnection, built, offering a variety of broadband services. thus creating all-wireless autonomous networks. Based on our own experience participating in Reasons for their emergence can be found in the one of the largest wireless communities world- above discussion. However, their success also wide, the Athens Wireless Metropolitan Net- depends on local factors (e.g. degree of penetra- work, we attempt to explain their structure and tion of fixed broadband access services in the mechanisms, study the reasons for their emer- area). Based on the offered wireless connectivity, gence and growth, and predict their future evo- such networks aim at providing a variety of ser- lution. We expect that future wireless vices, with free community-wide VoIP and file communities will be oriented toward providing sharing topping the list of the most frequently broadband access to nomadic users. To this end, accessed services. we have proposed that wireless network access Increased Wi-Fi coverage and the emer- be shared in a peer-to-peer, reciprocal manner. gence of WCNs raise the question of whether Thus, ubiquitous broadband Internet access can low-cost alternatives to traditional mobile ser- be achieved at a low cost, at least in metropoli- vices offered by 2.5G and 3G systems can be tan areas where there is abundant wireless cov- achieved. We focus on nomadic users, i.e. roam- erage, providing an inexpensive alternative to ing users accessing broadband services from broadband cellular services. multiple fixed locations and without necessarily sustaining uninterrupted connectivity while INTRODUCTION moving. In selected urban areas the answer is clearly yes, and the trend is in the direction of For wireless local area network communications, adequate coverage in all urban areas [2]. Before Wi-Fi emergence was a true revolution. Driven this idealistic environment is a reality, though, by their low cost and ease of deployment, IEEE issues such as the incentives of private WLAN 802.11-enabled devices became standard equip- owners to permit public access to their APs and ment for laptops and handheld devices and relevant security concerns need to be resolved. appeared as the predominant technology for As to WCNs, they are mainly exclusive; offering local wireless connectivity. Operation in unli- services to (potentially mobile) nonmembers censed spectrum facilitated Wi-Fi deployment, occurs today only due to the altruism of some since it was straightforward for commercial oper- of their participants. The architecture of such ators, academic institutions, or even plain radio networked communities and incentives that communications enthusiasts and tech-savvy users keep them operating with robustness are worth This article was written to build wireless service architectures on top of studying. while V.P. Kemerlis was it, without the need for acquiring a license. In In the remainder of this article, we first clas- at the Athens University of modern densely populated urban areas, the cov- sify public wireless access schemes and report on Economics and Business. erage that WLANs offer is ever-growing. Per- some of the most significant WCNs worldwide. 206 0163-6804/11/$25.00 © 2011 IEEE IEEE Communications Magazine • May 2011 FRANGOUDIS LAYOUT 4/20/11 2:11 PM Page 207 Access point WiFi interface with Mesh software router Point-to-point link Mobile user/client directional antenna Internet Internet Internet (a) (b) Figure 1. Architectural alternatives for Wireless Community Networks. A wireless mesh architecture is shown in (a), while the hotspot- based alternative is shown in (b). We describe the architecture of community wire- Commercial Initiative — Following the above less mesh networks. Then we discuss the circum- trend, commercial players have entered the stances under which WCNs emerged and scene, offering mediation services for the devel- evolved, respectively. We present the incentive opment of wireless communities. FON [9], for mechanisms that regulate their operation and instance, has proposed a private hotspot shar- study their future. We discuss our views and pro- ing scheme, where WLAN owners can either posal for WLAN hotspot sharing and conclude share their WLANs for a small monetary com- the article. pensation or in exchange for similar service when they are away from their own WLAN. FON takes care of user registration and authen- A CLASSIFICATION OF PUBLIC tication and withholds a fraction of the money IRELESS CCESS CHEMES paid to the hotspot micro-operator for the pro- W A S vided service. Here we characterize WCNs based on the initia- Notably, British Telecom has recently part- tive behind their emergence and their architec- nered1 with FON so that hundreds of thousands ture. of BT’s subscribers share their home broadband lines over Wi-Fi with other community members. INITIATIVES Community Initiative — A major focus of this Municipal Initiative — Municipalities often work is on wireless communities that are the set up APs in public spaces, offering inexpen- result of collective efforts of individual volun- sive Internet access to citizens. To achieve this, teers and function on a not-for-profit basis. Suc- they may get into agreements with private com- cessful communities have emerged, members of panies, permitting them to deploy their wireless which use IEEE 802.11/Wi-Fi technologies to set solutions. Authentication with the operator of up a wireless backhaul to connect to one-anoth- the network, as well as a fee for the service, er, enjoying a variety of broadband services, may be required. This model has been adopted such as VoIP, online games, FTP, or Web access by the municipality of Philadelphia [10], as well [3]–[7]. Sometimes community members operate as the City of London, which has set up a deal public hotspots to offer wireless access to with The Cloud, a European Wi-Fi hotspot passers-by, attaching them to the community aggregator. network, or even offering Internet access through community-owned Internet gateways. DESIGN ALTERNATIVES In a similar fashion, an individual WLAN Wireless Mesh — WCNs that have sprung owner may open his private hotspot for public from private initiatives often have this structure. access without anticipating monetary compensa- Multi-interface nodes set up a wireless mesh. tion. Instead, he is either driven by pure altru- Some also act as gateways to the public Internet ism, or expects that his offering will be and can be reached over the wireless backbone. reciprocated by other community members when We offer a more in-depth discussion of this he is roaming near foreign hotspots [8]. architecture in Fig. 1a. 1 http://www.bt.com/btfon IEEE Communications Magazine • May 2011 207 FRANGOUDIS LAYOUT 4/20/11 2:11 PM Page 208 Network Location Founded Size Architecture Initiative SeattleWireless Seattle, WA, USA 2000 ~80 nodes Mesh Community AWMN Athens, Greece 2002 2473 nodes Mesh Community CUWiN Urbana, IL, USA 2002 48 nodes Mesh Community Berlin’s Freifunk Berlin, Germany 2002 316 nodesa Mesh Community Wireless Leiden Leiden, Netherlands 2002 73 nodes Mesh Community NetEquality Roofnet Portland, OR, USA 2007 126 nodes Mesh Community NYCwireless New York City, USA 2001 145 nodes Hotspot-based Community Wireless Philadelphia Philadelphia, PA, USA 2007 15 miles2 Hotspot-based Municipal FON Worldwide 2006 ~700,000 hotspotsb Hotspot-based Commercial a Circa 2007 [6] b Based on information available from http://www.fon.com, as of September 2009. Table 1. Wireless communities around the world (as of September 2009). Hotspot-based Architecture — Hotspot-based is to provide a free citywide all-wireless network WCNs typically target nomadic users who use in the city of Leiden and offer free broadband wireless hotspots to access the Internet (Fig. 1b). Internet access to nearby villages, where no fast Here, deploying a wireless backhaul is not the Internet alternatives exist. norm. Municipality-initiated WCNs usually have Recently, the Freifunk community has gained this structure. Sometimes, hotspot-based WCNs much popularity. Freifunk mesh networks have are built relying on the private contributions of sprung up in various German cities, as well as in individual WLAN owners, who share their fixed cities in Austria and Switzerland. In Berlin, Frei- broadband lines over Wi-Fi. We have witnessed funk counted 316 concurrent participating nodes both commercially initiated [9] and not-for-profit on average, according to a 2007 study [6]. [8] such attempts. The MIT Roofnet [12] mesh network started as a research project focusing on wireless multi- hop routing and IEEE 802.11 protocol perfor- WIRELESS COMMUNITIES mance, while offering Internet access to nearby ROUND THE ORLD residents. It is now less vibrant (approximately A W 20 active nodes), but its technology is used from Here we report on some of the most significant other wireless community projects.