Broadband Access Technologies for Rural Connectivity in Developing Countries
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312 International Journal of Research and Reviews in Computer Science (IJRRCS) Vol. 2, No. 2, April 2011 Broadband Access Technologies for Rural Connectivity in Developing Countries F. Simba 1(Corresponding Author), B.M. Mwinyiwiwa 1, E.M. Mjema 1, L. Trojer 2, N.H. Mvungi 3. 1College of Engineering and Technology of the University of Dar es Salaam, Tanzania. 2Blekinge Institute of Technology, Sweden. 3College of Informatics and Virtual Education of the University of Dodoma, Tanzania. Abstract : Rural areas especially those of the developing Optical fiber technology is another option for access countries provide challenging environment to implement networks; it provides a huge amount of bandwidth in the communication infrastructure for data and Internet based services. range of Gbps. A single strand of fiber offers total The main challenges are the high cost of network implementation bandwidths of 25,000 GHz. Passive Optical Networks and lack of customer base, as rural areas are characterized by low (PONs) are widely deployed to implement the fiber optic income, highly scattered and low population density. This situation drives network operators to establish network infrastructures in access networks [2]. A PON is usually viewed as the final urban/city centers leaving rural areas as underserved community. segment of optical fiber-to-the home (FTTH) or close to it This paper surveys the available connectivity technologies with (FTTx). Commercially available and widely deployed PON potentials to offer broadband access network to rural areas. The access networks are the IEEE 802.3ah Ethernet PON scope of this survey is on wireless access technologies, due to the (EPON) with a symmetric rate of 1.25 Gb/s, or the ITU-T´s fact that they are efficient in terms of cost, time of deployment and G.984 Gigabit PON (GPON) with an upstream rate of 1.244 network management for rural environment. We provide Gb/s and a downstream rate of 2.488 Gb/s [2]. comparison of the surveyed technologies in terms of their capacity The xDSL and coaxial cable infrastructures are well (data rates) and coverage. We also discuss the current deployment established in developed countries. For example in most of of WiMAX and 3G technologies in Africa, which is a home to most of the developing countries. The survey results indicate potential the European countries and USA almost all households have broadband access technologies for rural areas of the developing twisted-pair cabling and the entire cities are connected by countries. POTS (Plain Old Telecommunication System). In addition, almost all households have wiring for cable services. Keywords: access network, broadband, developing countries, rural. However this is not the case in the rural areas of developing countries, which are characterized by low density and 1. Introduction sparsely populated areas. Characteristics of rural areas of the developing countries, provide a challenging environment in terms of network costs and time of deployment to implement A connectivity network can be categorized as a backhaul or wired technologies such as xDSL, coaxial cables and optical an access network. The access networks provides the so fibers. Therefore, wireless technologies are envisioned as called "last mile" connectivity that connect end users to the suitable technologies for rural environment. backhaul network which finally connect to the internet. The Wireless access technologies that are candidates for existing access network technologies constitute of enhanced broadband rural access networks include: Wireless Fidelity copper wires based on Digital Subscriber Line (xDSL), (WiFi), Worldwide Interoperability for Microwave Access coaxial cable, fixed and mobile wireless, satellite based (WiMAX), cellular mobile wireless networks and satellite wireless and fiber optic technologies. based technologies such as Very Small Aperture Terminal The xDSL technologies use existing Public Switched (VSAT). The access technologies surveyed in this paper are Telephone Network (PSTN) infrastructure to provide those with potentials to connect rural areas, especially those broadband data service. In xDSL, the telephone line carries of the developing countries. The scope is limited to wireless both voice and data signals/packets; there is a splitter at the technologies that have been proposed as candidates for rural end user premise where voice and data services are connectivity [3,4]. separated. The xDSL systems cover various technologies The rest of this paper is organized as follows: In section 2 such as asymmetric DSL (ADSL), very-high-speed DSL we investigate broadband wireless technologies that may (VDSL), and high-bit-rate DSL (HDSL). Their theoretical potentially provide rural connectivity. The investigation is peak data rates (downlink/uplink in Mbps) are: 2/1.05 based on the widely deployed technologies as well as the (HDSL), 8/0.8 (ADSL) and 52/26 (VDSL) respectively. emerging ones. Section 3 indicates the current deployment Cable modem technology uses coaxial cable to provide status of WiMAX and 3G technologies. In addition, there is a Internet data services along with digital TV. The theoretical comparison of the surveyed wireless technologies in terms of peak bandwidth is up to 30 Mbps. It is worth to note that capacity and coverage. Then, the survey conclusion and wired technologies have distance limitations. Therefore the direction for future research are presented in section 4. data rates provided depends on the distance covered. The data rate decreases as soon as the distance covered exceed the specified range. 313 International Journal of Research and Reviews in Computer Science (IJRRCS) Vol. 2, No. 2, April 2011 2. Broadband Access Technology for Rural Table 1. IEEE 802.16 Standard Description Connectivity Standard Description Data Rates WiFi technology, also known as IEEE 802.11 was 802.16d This 70 Mbps specifically designed for wireless local area network (802.16- amendment is standard. The WiFi technology offer theoretical peak data 2004) also known as rate of 54/11/54/600 Mbps for IEEE 802.11a/b/g/n standards 802.16-2004 respectively. Other technologies, either wired or wireless, because it was can serve as access networks to deliver data over long released in distance and then WiFi is used to deploy local network in 2004. The standard only order to distribute the data service locally. WiFi networks support fixed use unlicensed spectrum, which raises the possibility of operation. interference from other devices. Its coverage is limited in 802.16e This standard, 15 Mbps most cases to only 30 - 100 meters. Another option for (802.16- also known as broadband access network is the wireless mesh network 2005) 802.16-2005 in (WMN). The WMN is a communications network made up view of its of radio nodes organized in a mesh topology. It release date, designed for interconnects stationary and/or mobile clients and optionally nomadic and provides access to the Internet. Characteristic of a WMN is mobile use. that the nodes at the core of the network are forwarding data 802.16m This is an 100 Mbps to and from the clients in a multihop fashion. WMNs can be amendment to for mobile built up by using existing wireless technologies, such as the the air applications commonly used IEEE 802.11 (WiFi). Similar to WiFi, WMN interface; it can and 1 Gbps support both for fixed is also challenged by coverage limitation. Since the scope of fixed and applications this paper is on access technology to cover the last mile mobile users. connectivity of a rural area, then WiFi and WMN technologies are not discussed here. On the other hand, There are three topologies for WiMAX network: fixed point- satellite based wireless technology such as VSAT have been to-point (P2P), fixed point-to-multipoint (P2MP) and mobile proved from literature to be the relatively expensive option WiMAX. The WiMAX network consists of two key for rural connectivity [5]. Therefore, VSAT is also out of components: a base station and a subscriber device. The scope of this paper. The remaining wireless technologies WiMAX base station is mounted on a tower or tall building to broadcast the wireless signal. The subscriber can receives discussed are the WiMAX and cellular mobile technologies. the signals on a WiMAX-enabled notebook or mobile The hybrid fiber-wireless network is also discussed as a Internet device (MID). For fixed WiMAX deployments, a potential emerging access technology for rural connectivity. Customer Premises Equipment (CPE) is needed to act as a wireless modem providing interface to the WiMAX network 2.1. The Worldwide Interoperability for for a specific location, such as a home, cafe, or office. Microwave Access A point-to-point (P2P) topology consists of a dedicated long- range, high-capacity wireless link between two sites. The WiMAX, also known as IEEE 802.16, is a wireless central site hosts the base station (BS), and the remote site communications standard that is intended for wireless hosts the subscriber station (SS), as shown in Figure 1. The BS controls communications and security parameters in Metropolitan Area Networks (MAN). WiMAX provides establishing the link with the SS. The P2P topology is used broadband wireless access of approximately up to 48km for for high-bandwidth wireless backhaul services at a maximum fixed stations, and 5 - 15 km for mobile stations. The IEEE operating range of approximately 48 km using line of sight 802.16 standard has undergone different amendments for (LOS) or non-line of sight (NLOS) signal propagation [6]. improvements which at the end results into the earlier amendments, the IEEE 802.16a/b/c standards to be withdrawn. The current available standards are 802.16d, 802.16e, 802.16m [1]. Their respective brief description and data rates are shown in Table 1. 314 International Journal of Research and Reviews in Computer Science (IJRRCS) Vol. 2, No. 2, April 2011 mostly used in urban areas. The reason for this is, WiMAX was specifically designed for metropolitan area network although it has lots of potential to connect rural areas as well [7].