Types of Access to a WIMAX Network.
WiMAX is a broadband wireless standard that enjoys widespread support from both the computer and telecommunications industries worldwide, making this technology particularly cost effective. It is engineered to deliver significant business benefits to operators and users in diverse environments (enterprise, consumer, emerging, public service), geographies and demographies (urban, suburban, rural), both over the short and long terms. The paper highlights some points that make “WiMAX”- the World Interoperability for Microwave Access, the most appropriate technology solution to favor the broadband wireless access to ICTs infrastructure and services in rural areas. And also present the various usage scenarios of WiMAX to addressing different applications.
- Broadband wireless access
- Developing countries
The idea that access to information opens doors to wider economic and social development opportunities is not new. In 1984, the “Missing Link Report’’ pointed to the fact that the lack of telecommunication infrastructure in developing countries impedes economic growth, but with a scope limited to access to telephones rather than today’s wider concept of Information and Communications Technologies (ICTs) access and usage. In 1996, the International Telecommunications Union (ITU) initiated a United Nations project for the “Right to Communicate’’ aimed at providing access to basic ICTs for all, with motivation to reduce information poverty for developing countries. Thus, during the first World Summit on the Information Society (WSIS) held in Geneva in December 2003, the ‘Digital Divide’ was defined as the unequal access to ICT. Although this unequal access usually apply to differences between countries (the international digital divide) e.g. comparing developed and developing countries or regions; within countries (the domestic digital divide); and most importantly the divide between rural and urban, well educated or poorly educated populations or poor and rich citizens. Despite the various parameters and selected criteria (e.g. Internet host and/or users, fixed and mobile telephones) that can be considered or use to express an overall trend of growing ICTs disparities between and within countries, the availability and the quality of the access (i.e. the physical telecommunication infrastructure) is the key to a quick and reliable development of ICTs in the countries. Looking closer to the statistics as published by the different official bodies such as ITU or the World Bank in Figure 1, it is clear that the gap in ICTs access between developed and developing countries do exist (ITU World Telecommunications Development report 2003).
There are many reasons for the barriers why, until now, broadband ICT access was mainly deployed in developed countries and more precisely in urban areas as shown in Figure 2. However it can easily be explained that economics and existing technologies are the main drivers (and barriers in developing countries) to ICTs.
In the same way, while developed countries and urban areas are requiring higher and higher bit rates for multimedia applications, rural areas in developing countries are still at first favoring voice communication with a slow evolution towards ICTs. Moreover, while developed countries already have existing telecommunication infrastructure ready to evolve and the financial resources to invest and pay for new services, developing countries still suffer from the lack of basic infrastructures (not only telecommunication infrastructures, but also power supply, roads), and more crucial, have great difficulty to mobilize the necessary financial resources. This is what we call the “demand factor’’.
The paper is organized as follows. Section II defines WiMAX, the Forum and Profiles. Section III describes why and how WiMAX will be a key element in this new important worldwide objective to provide an equitable and affordable access to ICTs infrastructure and services. The various usage scenarios to illustrate the ability of WiMAX to address different applications are given in sections IV and V. And the paper ended with the conclusion.
2. What is WiMAX?
WiMAX stands for “World Interoperability for Microwave Access’’. It is a broadband wireless technology that supports fixed, nomadic, portable and mobile access. WiMAX is largely supported by the computer and the telecommunications industry, cost-effective and standard base. It is engineered to deliver the latest type of ubiquitous fixed and mobile services such as Voice 0ver Internet Protocol (VoIP), Information Technology and Video at very low cost. WiMAX systems are able to cover a large geographical area, up to 50 km and to deliver significant bandwidth to end-users up to 72 Mbps. To meet the requirements of different types of access, two versions of WiMAX have been defined. The first is based on IEEE 802.16-2004 and is optimized for fixed and nomadic access. The initial WiMAX Forum CERTIFIED products will be based on this version of WiMAX. The second version is designed to support portability and mobility, and will be based on the IEEE 802.16e amendment to the standard.
2.1. IEEE 802.16-2004 Standard
The IEEE 802.16 standard which includes Medium Access Control (MAC) and physical (PHY) layer specifications, aims at supporting Internet services over wireless metropolitan area networks (WMAN). It is also an alternative to traditional wired networks, such as Asymmetric Digital Subscriber Line (ADSL) and cable-modem. There are two modes (two different air-interfaces) defined in WiMAX networks: Point-to-Multi-Point (PMP) and Mesh modes. In PMP mode, two SSs (Subscriber Stations) can only communicate through BS (Base Station), while in Mesh mode, two SSs can communicate directly.
2.2. IEEE 802.16e -2005 Standard
On July 2002, a study group called IEEE 802.16 Mobile WirelessMAN Task Group was initiated to produce an amendment covering the PHY and MAC layers for combined, fixed, and mobile operations in the licensed band range. The amendment was approved in December 2005 and the new standard called IEEE 802.16e-2005 was published in February 2006. The scope of this standard is to provide mobility enhancement support for SS moving at the vehicular speed, in addition to corrections to 802.16-2004 fixed operation that was developed as IEEE 802.16-2004/Cor1-2005 and published along with IEEE 802.16e-2005. 802.16e introduces many changes to PHY and MAC layer protocols owing to mobility support, which required addressing new issues that were not required in 802.16-2004, such as handoff and power management.
The mobile WiMAX PHY layer is based on OFDMA technology. The network is an IP end-to-end conventional architecture that provides high-speed broadband. With a modification from fixed WiMAX to mobile WiMAX, the PHY layer also supports BWs from 1.25 to 20 MHz. The standard is designed to accommodate either TDD or FDD (Time / Frequency Division Duplexing) deployments, allowing for both full- and half-duplex terminals in the FDD case.
The MAC layer was initially designed specifically for the point-to-point wireless access environment. It supports higher layer or transport protocols such as asynchronous transfer mode (ATM), Ethernet, or IP, and is designed to easily accommodate future protocols that have not yet been developed. MAC layer specification practices considerable departures from 802.16-2004 to provide support for mobility. It adds support for handoff and power management.
3. WHY WiMAX AS SOLUTION?
Compared with other wired solution such as ADSL, or any other wireless or satellite system, WiMAX based access networks will enable operators and service providers to cost-effectively reach million of new potential customers providing them with broadband ICTs access. This is even true for developing countries and rural areas for which the cost/profitability and the demand factors are essential. This obviously includes adequate coverage, reliability, performances (throughput), capacity and applications. Table 1 shows how WiMAX supports different types of access and their requirement.
|Fixed||Outdoor and indoor||Single/stationary||No||Yes||Yes|
|Nomadic access||Indoor CPEs, PCMCIA cards||Multiple/stationary||No||Yes||Yes|
|Portability||Laptop PCMCIA or Mini-cards||Multiple/walking Speed||Hard handoff||No||Yes|
|Simple mobility||Laptop PCMCIA or Mini cards PDAs or smartphone||Multiple/low Vehicular Speed||Hard handoff||No||Yes|
|Full mobility||Laptop PCMCIA or Mini cards PDAs or smartphone||Multiple/high Vehicular Speed||Soft handoff||No||Yes|
The WiMAX standard has been developed with many objectives in mind. These objectives are as follows:
The two licensed bands 3.3-3.8 GHz and 2.3-2.7 GHz
One license exempt band 5.725-5.85 GHz.
In addition to the flexibility offered to address all national spectrum situations, this single radio, will makes base stations and customer premises equipment costs very attractive.
4. WiMAX Applications
WiMAX was developed to become a last mile access technology comparable to DSL, cable and E1/T1 technologies. It is a rapidly growing technology that is most viable for backhauling the rapidly increasing volumes of traffic being generated by Wi-Fi hotspots. WiMAX is a MAN technology that fits between wireless LANs, such as 802.11, and wireless wide-area networks (WANs), such as the cellular networks. WiMAX can serve in applications such as cellular backhaul systems, in which microwave technologies dominate, backhaul systems for Wi-Fi hot spots and most prominently as residential and business broadband services. WiMAX is billed to support many types of wireless broadband connections including but not limited to the following: high-bandwidth MANs, cellular backhaul, clustered Wi-Fi hotspot backhaul, last-mile broadband, cell phone replacements and other miscellaneous applications such as automatic teller machines (ATMs), vehicular data and voice, security applications and wireless VoIP.
Today, wherever available, these applications use expensive, proprietary methods for broadband access. WiMAX was developed to provide low-cost, high-quality, flexible, BWA using certified, compatible and interoperable equipments from multiple vendors. As WiMAX is based on interoperability-tested systems that were built using the IEEE 802.16 standard-based silicon solutions, WiMAX will reduce costs. WiMAX is well placed to address challenges associated with traditional wired access deployment types such as:
Large area coverage access, covering a large area (also referred to as hot zones) around the base station and providing access to 802.16 clients using point-to-multipoint topology;
Last-mile access, connecting residential or business subscribers to the base station using point-to-multipoint topology;
Backhaul, connecting aggregate subscriber sites to each other and to base stations across long distances using point-to-point topology.
In summary, the WiMAX standard has been developed to address a wide range of applications as shown in Table 2.
|Class description||Real Time?||Application type||Bandwidth|
|Interactive Gaming||Yes||Interactive gamig||50 ? 85 K bps|
|VoIP,Video conference||Yes||-VoIP -Video phone||4 - 64 Kbps 32 ? 384K bps|
|Streaming media||Yes||-Music/Speech -Video clips -Movies streaming||5 ? 128 K bps 20 - 384Kbps "/>2 Mbps|
|Information Technology||No||- Instant messaging - Web browsing E-mail(with attachment )||<250byte messages "/>500 K bps "/>500 Kbps|
|Media Content Download Store and forward||No||Bulk data, Movie Download||"/>1Mbps "/>500 K bps|
Some more disruptive applications of WiMAX can be:
Remote monitoring of patients’ vital signs in health-care facilities to provide continuous information and immediate response in the event of a patient crisis.
Mobile transmission of maps, floor layouts and architectural drawings to assist fire-fighters and other response personnel in the rescue of individuals involved in emergency situations.
Real-time monitoring, alerting and control in situations involving handling of hazardous materials.
Wireless transmission of fingerprints, photographs, warrants and other images to and from law-enforcement field personnel.
5. Usage Scenarios
Based on its technical attributes and service classes, WiMAX is suited to supporting a large number of usage scenarios. WiMAX technology will revolutionize the way we communicate. It will provide total freedom to people who are highly mobile, allowing them to stay connected with voice, data and video services. It will allow people to go from their homes to their cars, and then travel to their offices or anywhere in the world, all seamlessly. To illustrate the ability of WiMAX to address the applications outlined in Table 2, several representative usage scenarios are outlined in Table 3.
|Technical Attribute Usage Scenario s||Flexible Arch||High Security||Wimax QoS||Quick Deployment||Interoperability||Portability||Mobility||Cost Effecttive||Wider Coverage||NLOS||High Capacity|
|Cellular B ack haul||*||*||*|
|Wireless Service Provider||*||*||*|
|Offshore Comms .||*||*||*||*||*||*|
5.1. Cellular Backhaul
Majority of backhaul is done by leasing E1 services from incumbent wire-line operators. With the WiMAX technology, cellular operators will have the opportunity to lessen their independence on backhaul facilities leased from their competitors. Outside the United States, the use of point-to-point microwave is more prevalent for mobile backhaul, but WiMAX can still play a role in enabling mobile operators to cost-effectively increase backhaul capacity using WiMAX as an overlay network as depicted in Figure 5. This overlay approach will enable mobile operators to add the capacity required to support the wide range of new mobile services they plan to offer without the risk of disrupting existing services.
Some salient points about WiMAX use as cellular backhaul are:
multiple cell sites are served;
there is capacity to expand for future mobile services;
It is a lower cost solution than traditional landline backhaul.
5.2. Education Networks
School boards can use WiMAX networks to connect schools and school board offices within a district, as shown Figure 6. Some of the key requirements for a school system are NLOS, high bandwidth (>15 Mbps), Point-to-Point and Point-to-Multipoint capability, and a large coverage footprint. WiMAX-based education networks, using QoS, can deliver the full range of communication requirements, including telephony voice, operating data (such as student records), email, Internet and intranet access (data), and distance education (video) between the school board office and all of the schools in the school district, and between the schools themselves. The WiMAX solution provides broad coverage, making it very cost-effective, particularly for rural schools, which may have little or no communications infrastructure, and which are widely dispersed. When school boards own and operate their own network, they can be responsive to changes in the location and layout of their facilities. This will significantly reduce the annual operating cost of leased lines. Wired solutions cannot offer a quickly deployable, low-cost solution, and most versions of DSL and cable technology do not have the throughput required by these education networks.
5.3. Campus Connectivity
Government agencies, large enterprises, universities, and colleges, can use WiMAX networks to connect multiple locations, sites and offices within their campus, as shown in Figure 7. Campus systems require high data capacity, low latency, a large coverage footprint, and high security. Campus networks carry a mix of voice, data, and video, which the WiMAX QoS helps prioritize and optimize. It takes less time and resources to interconnect a campus through a WiMAX network, since excavation and external construction are not required. Some campuses have been around for a long time, and digging trenches for cable may not be permitted. In such cases, WiMAX solutions may be one of the most effective ways to interconnect campus buildings. Even if wired installations are permitted, the lead-time to deploy a wired solution is much longer than the lead-time to deploy a WiMAX solution, without offering any accompanying benefits.
5.4. Rural Connectivity
Service providers use WiMAX networks to deliver service to underserved markets in rural areas and the suburban outskirts of cities as shown in Figure 8. The delivery of rural connectivity is critical in many developing countries and underserved areas of developed countries, where little or no infrastructure is available. Rural connectivity delivers much-needed voice telephony and Internet service. Since the WiMAX solution provides extended coverage, it is a much more cost-effective solution than wired technology in areas with lower population densities. It solutions can be deployed quickly, providing communication links to these underserved areas, providing a more secure environment, and helping to improve their local economies.
5.5. Wireless Service Provider Access Network
Wireless Service Providers (WSPs) use WiMAX networks to provide connectivity to both residential (voice, data and video) and business customers (primarily voice and Internet), as illustrated in Figure 9. The WSP could be a CLEC (Competitive Local Exchange Carriers) that is starting its business with little or no installed infrastructure. Since WiMAX is easy to deploy, the CLEC can quickly install its network and be in position to compete with the ILEC (Incumbent Local Exchange Carrier). A common network platform, offering voice, data and video, is highly attractive to end customers, because it presents a one-stop shop and a single monthly bill. Support for multiple service types allows for different revenue streams, yet it reduces customer acquisition cost, and increases ARPU (Average Revenue Per User). The WSP needs only one billing system and one customer database. Cellular operators may also be interested in applying WiMAX in their networks. These operators already have towers, billing infrastructure and a customer base in place, but the deployment of a WiMAX solution will expand their market presence in their service area.
5.6. Theme Parks
Theme park operators can use WiMAX to deliver a broad range of communication services for their amusement parks, expositions, hospitality and operation centers, and buses and service vehicles, as shown Figure 10. The network can support a wide range of communications traffic, including two-way dispatch from a control center, video surveillance throughout the park, reservation data, inventory database access and update, site status monitoring, video on demand, and voice telephony. Some of the key requirements for a system like this are support for fixed and mobile operations, high security, scalable architecture and low latency. The broad coverage range of WiMAX means an entire park can be covered from only a few numbers of Base Stations, scalable upwards as capacity requirements increase.
Re-deployment of the network, in response to changes in theme park facilities, is straightforward and simple, unlike the changes that would be required had the park been served by wired facilities, such as DSL or cable. WiMAX mobility capability will support two-way voice and data communications to the theme park’s tour buses and service vehicles. Real-time video can be broadcast to tour buses, providing tourist information, promotions, and weather to passengers.
Demand for wireless broadband access is growing fast and embracing an ever-widening range of applications that encompass fixed, nomadic, portable and mobile data access as well as fixed and mobile voice services, and content streaming. Looking back to the barriers as summarized by ITU in Figure 2 and section 3, WiMAX appears clearly as the solution to favor the broadband ICTs access in developing countries. Undoubtedly, WiMAX is a new powerful broadband wireless technology aiming at providing a universal ubiquitous and equitable and affordable access to ICTs infrastructure and services, and thus highly contributing to bridge the “Digital Divide”.
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