Planning of Wireless Community Networks Károly Farkas
University of West Hungary Bajcsy-Zsilinszky u. 9. H-9400 Sopron, Hungary
Budapest Univ. Tech&Econ Magyar Tudósok krt. 2. H-1117 Budapest, Hungary
Budapest Univ. Tech&Econ Magyar Tudósok krt. 2. H-1117 Budapest, Hungary
ABSTRACT The objective of this chapter is to discuss the applications, state-of-the-art technologies, planning methods and business models for wireless community networks and provide an integrated presentation of these essential parts with examples. After a short introduction we give an overview about the state-of-the-affairs of wireless community networks presenting the driving forces, stakeholders, services and built upon applications in some carefully selected projects. Then, we discuss the technological aspects and suggest a design methodology for planning wireless community networks. The application of this methodology is illustrated via an ongoing digital city project in Hungary. After this we analyze the relevant business models and include a sample financial calculation. And finally, before concluding the chapter we give a short outlook discussing the future trends of the area.
1. INTRODUCTION Broadband access to citizens, communities, public institutions and developing businesses is a natural need today. However, there is no a straightforward way to provide broadband access to these users. Although today’s technologies (from ADSL via fiber-to-the premises to broadband wireless access) are appropriate for this purpose, telecommunication companies cannot afford their deployment and serve these users due to the large costs and very long return on investment (ROI) period. As an alternative, a so-called community network (CN) can be created and deployed by governments and international organizations worldwide serving strategic purposes, too. Community networks are able to foster economic development, help startups grow, bring new businesses into the region and can alleviate also the problems related to the digital divide. Reflecting these objectives a huge number of community network related initiatives have been launched recently in North America as well as in Europe. Community network infrastructures can be built by using the common technologies in telecommunication companies’ networks. Fiber has been an attractive solution for many cities, first of all in North America. Building a fiber network is technically viable where a local government or some of its utility companies own ducts and support structures forming “free” assets. However, for economical feasibility it is necessary to have a few large customers, such as ISPs (Internet Service Providers), which use and pay for a substantial share of fiber capacity. On the other hand, wireless technologies (e.g., Wi-Fi, WiMAX or 3G mobile) are almost always appropriate for building community networks because they are relatively easy to install, expand and operate in a cost effective manner. Planning, deployment and operation of community networks have been challenging tasks. As opposed to telco networks, there is a specific set of services that the city or region wants to implement. These services and built upon applications are to be made accessible for a wide range of geographically diverse users regardless their locations. Moreover, cities can more freely choose communication technologies, including emerging ones, as they do not have the stringent business requirements the telecommunication companies have to meet, such as short ROI or totally risk-free adaptation of new technologies. However, suitable business models have to be defined with clever constructions of involving both the public and private sectors, while satisfying legal and regulatory requirements. The objective of this chapter is to discuss the applications, state-of-the-art technologies, planning methods and business models for wireless community networks and provide an integrated presentation of these essential parts with examples. This integrated approach has been rarely found in the technical literature. Our previous works (Szabó et al., 2007; Szabó et al., 2008) address the issue of wireless community networks. A recent edited book (Chlamtac et al., 2005) attempts to bring together the most important aspects – technical, legal, regulatory and economic – of community networks into one book.
Within the framework of an ongoing European Network of Excellence project called OPAALS (OPAALS, 2008), the social side, information technologies and economic models are being investigated by a large inter-disciplinary international team, also putting community networks in a wider context of digital ecosystems and digital business ecosystems.
2. BACKGROUND In this section, first we discuss the stakeholders, initiators and the set of applications usually considered for community networks, then present one European and two North American case studies as representative examples of community network projects.
2.1 Community Networks Under the term “community network” or CN we mean the combination of the telecommunication infrastructure created by the participation of the local government or public organization, the services provided upon it and the specific business model to operate the infrastructure and provide services. Here we mainly focus on wireless CNs, where at least the access part but in many cases also the distribution and backbone parts are implemented using a wireless and/or mobile technology. The stakeholders of community networks include: (i) public agencies (local governments, local development agencies, public organizations); (ii) users (citizens, SMEs (Small and Medium Enterprises), associations, etc.); (iii) private sector service providers (e.g. telcos or ISPs); (iv) local and global facilitating agencies (such as research and consulting centers, associations of community networks). Usually one of the above stakeholders is the “initiator” of the project. Classical community networks were initiated by the communities themselves as grass root initiatives, since most of today’s projects are planned and implemented by some form of local and/or regional governments’ participation. Applications that drive the development of community networks can be grouped as follows: A) Access to public information and services • Public Internet kiosks for access to public information, e-government services, tourism. • Portals for e-government services, for local communities and for tourists. B) Public safety • Enhancing public safety by remote surveillance of public areas. • Improving the communication with police, civilian police, fire department and alike. C) Traffic control and transportation • Coping with traffic congestion by vehicle monitoring and intelligent traffic light control. • Vehicle management for public transportation (buses). • Intelligent parking systems with flexible payment. • Monitoring of road conditions, in particular in winter. D) Health care Improving the efficiency and cost-effectiveness of health care services by broadband and wireless communications among and within health care providers. • Providing telemedicine services. • Home health care and assisted living. E) Business services •
• Business partners/providers/clients searching. • Digital services: search, use and combine. • B2B (Business to Business) and B2C (Business to Client) transactions. • Advertise product and services. F) Educational • Remote classroom. • Remote consultation. G) Utility companies • •
AMR (Automated Meter Reading) for electricity, water, gas companies. On-line maps with pipes and wires helping outdoor works.
In most cases, there is usually 1 or 2 applications that are the main motivations for the implementation of a given community network. Below we list some wireless CN initiatives together with their primary applications (Intel Solutions, 2005): • Chaska, MN, US - Digital divide for schools, businesses and residents; • Cheyenne, WY, US - Traffic signal management; • Corpus Christi, TX, US - Automated meter reading for city-owned utilities; • Lewis&Clark County, MT, US - T1 replacement; access to remote county buildings; • Ocean City, MD, US - Integrated digital, voice and video for city buildings; • Piraí, Brazil - Municipal field-force productivity; promotion; • Portsmouth, UK - Bus passenger information dissemination; • San Mateo, CA, US - Police field-force productivity improvement; • Shanghai, China - Police field-force productivity improvement; • Spokane, WA, US - Municipal applications and e-Government initiatives; • Westminster, UK - Video surveillance and enhanced security.
2.2 Case Studies of Recent Community Network Projects As the status of August 1, 2007 there were 92 regional and city-wide networks, 68 city hot zones and 40 public safety and municipal use networks, alone in the US (source: MuniWireless (2008), one of the well-known portals of wireless community networks). Furthermore, 215 city and country-wide projects are in progress. The total number of existing networks and ongoing projects is 415, which reflects an exponential growth regarding the figure (122) two years ago. There are similar initiatives around the globe and a comparable growth is expected to happen in the next few years. Although Europe, at least the continental part, seems to be lagging behind the US, the ambitious European plans to penetrate broadband services to citizens and institutions and foster regional development can help the spreading of CNs even on the old continent. Below we present three case studies of recent community network projects that represent different objectives, target applications, stakeholders and business models. Although all these projects aim at providing various services and applications, in each case there is one primary application on which the business model is built. T.Net in Italy aims at creating a telecommunication infrastructure in a province that is sparsely populated and geographically challenged. The main goal of Wireless Philadelphia in the US is to provide Internet access in a city where the Internet penetration is quite low, while the primary objective of the Corpus Christi project in the US is to implement city-wide remote data collection for utility companies.
2.2.1 T-Net, Trentino, Italy T.Net (Longano, 2007) is a community network project under implementation in Trentino, a province in Northern Italy. It is part of the eSociety initiative of the local government, whose strategic aims are: (i) the innovation of the local economy; (ii) the improvement of Public Administration efficacy; and (iii) the reduction of the gap which keeps many citizens from participating in the Information and Knowledge Society. Its management model involves publicly controlled companies for the implementation and management of the broadband infrastructure, supplying of transport services, connectivity and IT services for public administration and renting infrastructure to market operators under fair and non-discriminatory conditions. The network consists of a fiber optic backbone and a pre-WiMAX based (HiperLAN-2) wireless access network. The number of backbone nodes is 78 with the total length of optical cable over 750 km. The network connects 223 municipalities in total. Until the fiber infrastructure will be built, the province is leasing Gbit Ethernet facilities from Telecom Italia, the Italian incumbent telecom service provider. At the end of 2007, wireless access was provided for 150 municipalities.
2.2.2 Wireless Philadelphia, US The Wireless Philadelphia initiative (The Wireless Philadelphia Executive Committee, 2005) started with a pilot, covering the central districts and is currently being expanded to cover the entire metropolitan area with a total of 20 million USD investments. The project is financed and implemented by EarthLink, one of the dominant ISPs in the US. The business model is built on providing Internet access in the city, as the level of broadband penetration is very low (below 25%) and is mainly based on dial-up access. EarthLink is also planning to sell bandwidth both to retail and wholesale customers. The city is planning to subsidize Internet access for low-income residents. Mobile workers that constitute half of the city workforce will communicate using this network infrastructure, supported by an already implemented Geo-spatial Information System (GIS). Other applications include video surveillance to reduce crime in the city.
2.2.3 Corpus Christi, US
In 2001, the city of Corpus Christi, which has about 250,000 inhabitants and an area of about 150 sq. miles, decided to implement an AMR system for water and gas customers (Corpus Christi Pioneers, 2007). The underlying network is an optical fiber backbone together with a Wi-Fi mesh network built and operated by Tropos Networks, the market leader in delivering metro-scale Wi-Fi mesh network systems. Overall, the city spent 20 million USD on the AMR system and on the wireless network, which yields a saving of 30 million USD over the estimated 50 million USD costs within the next 20 years without AMR. In addition to savings, the project resulted in higher level of customer service and support to citizens. After the rollout of the project, it was realized that the AMR application uses only a fraction of the bandwidth of the wireless network. Therefore, the city is planning to implement other applications including the support for public safety, health inspection, animal control, public works and utilities personnel.
3. TECHNOLOGICAL ASPECTS In this section, first we give a short overview about the available wireless technologies on which wireless community networks can be built, then discuss the planning issues for technology selection regarding these networks.
3.1 Available Wireless Technologies Below we overlook three wireless technological alternatives such as Wi-Fi mesh, WiMAX and 3G cellular mobile. For further information interested readers should refer to any of the several books, e.g. (Webb, 2007), on wireless technologies.
3.1.1 Wi-Fi Mesh Wi-Fi (Wireless-Fidelity) mesh networks are peer-to-peer multi-hop networks based on the IEEE 802.11 standard family (IEEE 802.11, 2008), where the nodes cooperate with each other to route information packets through the network (see Figure 1). They present an alternative solution to “infrastructure based” networks like ADSL (Asymmetric Digital Subscriber Line). Mesh networks have some attractive features. Thus, they are “organic”; nodes may be added and deleted freely; the mesh principle means also fault tolerance, hence nodes may fail and packets will still be routed; mesh networks are manageable in a distributed manner. However, mesh networks also pose challenges. If there are too many nodes, the need for routing other nodes’ traffic decreases the access throughput of a given node. On the other hand, if there are too few nodes then routing could be a problem. Security is also an issue. A practical problem is that today there are no interoperable products as the WLAN (Wireless Local Area Network) mesh standard (IEEE 802.11s) is relatively new. In spite of the aforementioned shortcomings, the majority of wireless CNs is Wi-Fi mesh and it is the most likely option to consider when someone is planning to create such an infrastructure. Current products feature dual/multiple radios (separate radio(s) for the access and backbone parts) to significantly compensate the throughput decrease when traffic is routed through a chain of nodes. Most recently combined devices have been also developed that implement both the Wi-Fi mesh and WiMAX capabilities using the latter technology for backbone purposes.
Figure 1. Wi-Fi Mesh Network Example1
Source: Proxim Wireless (2005)
3.1.2 WiMAX WiMAX (Worldwide Interoperability for Microwave Access) is an emerging wireless technology and a flexible telecommunication architecture based on the family of IEEE 802.16 standards (IEEE 802.16, 2008). It is often considered as the next generation of Wi-Fi networks, though the two technologies represent two different design and development lines from technical perspectives. The WiMAX technology provides a big step ahead evolution as the offered capacity and the communication range are approximately an order of magnitude higher compared to Wi-Fi. The topology of a WiMAX network can be point-to-point, point-to-multipoint or mesh. The area coverage is up to tens of km in LOS (Line Of Sight) environment at limited data rates. An attractive feature is operation under NLOS (Non Line Of Sight) conditions. Spanning only short distances high capacity and data rates up to 100 Mbps can be achieved which make WiMAX a viable option for backbone and distribution network segments. It provides a high level of security due to the 3DES (Data Encryption Standard) and the AES (Advanced Encryption Standard) encryption standards. Quality of service is an inherent feature of WiMAX. It has several service classes including support for real-time data streams. Figure 2 illustrates a typical fix WiMAX network architecture consisting of base stations, subscriber stations and different communication link types. To support mobile or nomadic users – implementing seamless handover of the user between the base stations – the mobile version of WiMAX based on the IEEE 802.16e standard was approved at the end of 2005, and products built on this standard have already been available. To deploy a WiMAX network is easy, quick and relatively inexpensive. Different spectrum allocation possibilities exist in licensed and license-free frequency bands. However, implementers of wireless CN infrastructures are cautious regarding WiMAX, mainly due to the currently high costs of WiMAX subscriber stations. Though, as we mentioned above, the combination of a WiMAX based backbone for Wi-Fi mesh networks seems to be an attractive option. Moreover, mobile WiMAX will be definitely the solution when mobility is of key importance.
Figure 2. Fix WiMAX Network Example2
3.1.3 3G Cellular Mobile 2
Source: Intel Corp. (2004)
3G cellular systems together with enhancements like HSDPA/HSUPA (High-Speed Downlink Packet Access/High-Speed Uplink Packet Access) (ITU, 2008) also, due to the smaller cell size, offer per-customer data rates that would satisfy the requirements of most of today’s mobile applications. Nevertheless, it is hard to find community networks that are based on cellular mobile service. The reason might be a simple one: municipalities did not take this option into account. On the other hand, cellular operators might be also reluctant to work out individual offers for cities with very special pricing, and specific solutions in addition to cellular coverage, e.g. a combination with WiMAX, to support large institutional users. Thus, we include this option here for completeness only.
3.2 Technology Selection for Wireless Community Networks As mentioned above, there are differences between community networks and telcos’ networks from the viewpoint of technology selection, too. For community networks, cost minimization is not the primary objective and implementers of CNs can also experiment with new and advanced technologies. Another difference is that interoperability is of critical importance for CNs. There are several factors to be considered when selecting the right wireless technology for a CN, such as application requirements, coverage, timeframe, frequency issues and costs. Below we focus only on the requirements of the applications and expected coverage which should be identified in the first step. A summary of our analysis about the state-of-the-art wireless technologies is shown in Tables 1 and 2. One of the most important issues in technology selection is finding the most suitable alternative for the application requirements. Table 1 helps choose the right technology and configuration by coverage, bandwidth and density parameters. Table 2 focuses on QoS (Quality of Service) measures. First, we should define the main elements of the network: • • •
Microcell is an area covered by one access point or mesh node in the access network. Macrocell is a union of well-connected microcells. Macrocell connects to the backbone with one or more backbone access points. Backbone access point (BAP) is a node of the network, which connects one macrocell to the backbone network.
As a general assumption, there is no sectorization in the discussed network topology scenarios, we use only omni-directional antennas. Table 1. Technology Selection for Capacity and Coverage Planning ID1 Techno- Configu- Maximum Number of Maximum Maximum Maximum logy 2 ration 3 microcell microcells macrocell microcell node capacity 4 in capacity 6 radius 7 distance 8 5 macrocell
Maximum Maximum Typical usage 11 coverage bandwidth (macrocell density size in 0.01 (Mbps/0.01 km2) 9 km2) 10
2 Wi-Fi mesh
Max. 2 hops NLOS
175 Mbps 100 m
High density coverage (optimal)
3 Wi-Fi mesh
Max. 3 hops NLOS
170 Mbps 100 m
High density coverage with few BAP
100 Mbps 3 km
Rural, backhaul, special req’s
4 WiMAX LOS
100 Mbps 1
5 WiMAX NLOS
6 WiMAX Max. 2 mesh hops NLOS
380 Mbps 1 km
Rural, urban, suburban
Explanations to Table 1 column by column:
1 2 3
ID: Identifies the cases for referring. Technology: What network technology, Wi-Fi or WiMAX, is used and in point-to-multipoint or in mesh mode. Configuration: Indicates the condition of propagation, which affects link quality and cell size, and the maximum number of hops in mesh scenarios. Maximum microcell capacity: Average effective usable data rate at network layer using the given technology and configuration. Number of microcells in macrocell: This number is 1 in non-mesh networks. In mesh networks, it can be calculated from the maximum number of hops. Maximum macrocell capacity: Microcell capacity multiplied by the number of microcells in one macrocell. Maximum microcell radius: This parameter values are based on transmission power limited by EU-conform regulation at high data transfer rates for high cell efficiency. Within the given range the actual technology can provide an almost perfect coverage in most cases. Maximum node distance: The distance of two neighboring nodes should not be longer than the maximum microcell radius multiplied by the square root of 2, caused by the square gridded layout of the topology. Hence, the full coverage is ensured with existing overlapping areas. Maximum coverage (macrocell size in 0.01 km2): This value shows the size of the covered area by one macrocell. We can also define backbone access point (BAP) density in number of BAP/km2 which can help estimate the initial and operational costs. Maximum bandwidth density (Mbps/0.01 km2): The quotient of the capacity and the coverage of macrocell. It shows the available bandwidth on each area of 100x100 m2. Typical usage: This field indicates typical scenario(s) where the given technology and configuration are often used.
The data in Table 2 are also based on our measurements and calculations using the following assumptions: • •
Soft QoS means IEEE 802.11e standard in Wi-Fi. Managing QoS is one of the inherent features in WiMAX. The delay and jitter parameters are one-way latency measures. Table 2. Technology Selection for QoS Planning
Maximum Average microcell delay per capacity hop (low utilization )
Average delay per hop (high utilization) without QoS
Average delay Bandwidth Voice per hop (high allocation transmission utilization) capability capability with QoS with/without soft QoS
20 Mbps 5 ms
yes / no
2 Wi-Fi mesh
Max. 2 hops NLOS 7 Mbps
yes / no
3 Wi-Fi mesh
Max. 3 hops NLOS 2 Mbps
no / no
100 Mbps 20 ms
50 Mbps 30 ms
6 WiMAX mesh Max. 2 hops NLOS 16 Mbps 80 ms
Our practical suggestions for technology and configuration selection based on Table 1 and 2 are: •
If some not frequently connected spots should be covered by a wireless network, standalone Wi-Fi access points as hotspots should be used. It can be used in LOS and, to a limited extent, in NLOS conditions. IEEE 802.11e capable devices should be used to support QoS requirements to real-time services such as voice communication (Table 1, 1st row).
If a larger area has to be covered by a limited number of backbone access points, Wi-Fi mesh network with only few hops should be used. More than 2-3 hops to the BAP cause degradation in effective bandwidth and in QoS parameters, too. Real-time applications can tolerate this relapse up to 2 or 3 hops with 802.11e support (Table 1, 2nd and 3rd rows).
Wide areas with low density of users should be covered by WiMAX. It can be used not only in access networks but also in backbone networks in point-to-point or point-to-multipoint configuration. Robustness and high data rates of WiMAX guarantee the QoS and sufficient capacity in LOS and in NLOS environment, too (Table 1, 4th and 5th rows).
WiMAX can operate also in mesh mode. In this case, advantages of Wi-Fi mesh and WiMAX are combined. However, this solution has been not widely implemented yet (Table 1, 6th row).
To summarize the possibilities for technology selection to build wireless CNs we can say that, for a number of applications, Wi-Fi mesh could be the solution, but for applications that require QoS and high bandwidth, WiMAX is the best choice. However, because of the low penetration of WiMAX devices, we have to use still today a widely preferred access technology, such as Wi-Fi. On the other hand, the backbone or distribution network should be robust and should have sufficient capacity. The combination of WiMAX and Wi-Fi technology, and the combination of mesh, ordinary access and transfer can be the optimal solution for every wireless community network. Wi-Fi will remain the only feasible customer access solution for the next 2-3 years (until mobile WiMAX cards will be as ubiquitous and cheap as expected by major market players).
4. DESIGN OF WIRELESS COMMUNITY NETWORKS In this section, we deal with issues related to the design of wireless community networks. Fist, we overview the design methodology, then illustrate the network design by a case study.
4.1 Design Methodology In general, there are significant differences between planning of CNs and ISPs’ or other service providers’ design methodology. Key differences include the following requirements for the planning of CNs: (i) ubiquitous Wi-Fi access covering the whole territory of the community; (ii) users should be provided with other forms of access as well; (iii) mobility or at least nomadic access across the covered area must be supported; (iv) support of a multiplicity of user devices from simple mobile phones through PDAs and laptops to video conferencing equipment; (v) the network should support a specific set of government, business and society-related applications. The whole design process consists of the following steps: 1.
Identifying applications and services. First, we should select the key applications and services which raise requirements toward the network.
Identifying network technology requirements, based on applications. We should analyze the requirements of the applications and services selected in the first step. This analysis should contain QoS (delay, jitter) and bandwidth parameters.
Identifying coverage requirements and the possibilities and limitations of the environment. To prepare the network technology selection, we should determine the area which is supposed to be covered by the network, with its topography, natural obstacles such as hills or trees as well as buildings, availability of support structures, towers etc.
Choosing network technology. Selecting the right technology is one of the key parts of network planning. This decision should be based on identified requirements and conditions of the environment. We should choose optimal solutions both for the access and the backbone network. This step of the design process is explained in detail in Section 3.2.
Planning of network topology. This complex part of the methodology uses the results of the coverage requirement analysis as well as the network technology selection. We should plan the network topology according to the topography and the optimal station placement strategies.
Verifying original requirements. Last, but not least, this step stands for verifying the results of planning. We should recognize the differences between the original requirements and the capabilities provided by the planned network.
These steps are illustrated in Figure 3.
Figure 3. Flowchart of the Design Process for Wireless Community Networks
4.2 Case Study: Network Design for a Digital City in Hungary To illustrate the design methodology discussed above we present here the wireless network design of a digital city in Hungary. The digital city project is the municipality’s initiative to implement a city-wide network infrastructure and services based on that.
4.2.1. Services for the Municipality of the City The planned wireless infrastructure will serve several important goals: (i) it will carry the internal data and voice traffic among public institutions and publicly controlled companies, thus saving costs of bills currently being paid to telecom service providers; (ii) it will improve the efficiency of work processes and introduce electronic customer services via an egovernment initiative; (iii) it will improve services for citizens and facilitate citizens’ participation in public processes. Some specific applications based on interviews with potential large users are as follows:
A) Public safety system The objective is to improve public safety and reducing crime in the city by establishing a network of surveillance cameras and equip police and fire brigade personnel with wireless enabled devices. B) Telemetrics for a local utility company The objective is to use the wireless network to implement AMR for the local water company. C) Parking management for a local parking company The wireless community network is planned to support parking services in several ways: communication with the parking ticket dispensers, providing enforcement staff with handheld devices, etc. Additional services include online payment, SMS warnings of expiring parking tickets and reminders of unpaid parking dues. D) Services for a public bus company The objective is to improve the efficiency of the company’s operations and the quality of passenger service. The planned wireless CN will collect and transmit real-time data related to departure and arrival times, delays, technical problems, road and traffic conditions. E) Advanced tourism information system The objective is to implement a tourist and cultural information portal based on geospatial information system, and install several kiosks supporting free or low-cost Internet access to this portal.
4.2.2 Pilot Network Estimations and Planning After identifying the services we have to analyze their requirements (Table 3). The required overall microcell capacity is calculated as the aggregate of average bandwidth for each service, and the maximum value of delay in the network must be not greater than the minimum of the maximum tolerated service delays. Table 3. Requirements of the Identified Services Service ID
Average Bandwidth Probability of Average per user per activity per number of user bandwidth microcell user per microcell per microcell
Maximum tolerated delay