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Maxing Out on WiMax

  • 20 October, 2004 15:07

Broadband wireless will revolutionise people's lives by enabling a high-speed connection directly to the information they need, whenever and wherever they need it. Broadband data services, such as delivery of rich Internet Protocol and media content, are an increasingly important component of the services and revenue of network operators, who want to expand the reach of their broadband data networks without expensive construction and infrastructure costs. High-speed broadband wireless data overlays to voice network are just emerging, as service providers respond to these consumer and enterprise demands for rich media, mobile applications and services.

What exactly is WiMAX? WiMAX (Worldwide Interoperability for Microwave Access) is a technology for "wireless" broadband. Some people referred WiMAX to as "WiFi on steroids". Today, when you want broadband, you connect using T1, DSL or cable modems to physical cables called landlines. WiMAX, an evolving standard for point-to-multipoint wireless networking, works for the "last mile" in the same way that Wi-Fi "hotspots" work for the last one hundred feet of networking within a building or a home. In addition to "last mile" broadband connections, WiMAX has a number of other applications in hotspots, cellular backhaul and in high-speed enterprise connectivity.

When the WiMAX technology is fully deployed in a few years, a WiMAX base station could beam high-speed Internet connections to homes and businesses in a radius of up to 50 km (30 miles) (typical is three – five km due to obstructions); these base stations will eventually beam to an entire metropolitan area, making that area into a WMAN and allowing true wireless mobility within it.

The ability to provide these broadband connections wirelessly, without laying wire or cable in the ground, greatly lowers the cost to provide these services. So, WiMAX may change the economics for any place where the cost of laying or upgrading landlines to broadband capacity is prohibitively expensive, as in emerging countries. In countries like India, Mexico, and China, where there is currently insufficient wired infrastructure, WiMAX can become part of the broadband backbone.

How does WiMAX work?

WiMAX is poised to become a key technical underpinning of fixed, portable and mobile data networks. WiMAX is an implementation of the emerging IEEE 802.16 standard that uses Orthogonal Frequency Division Multiplexing (OFDM) for optimisation of wireless data services. OFDM technology uses "sub-carrier optimisation," assigning small sub-carriers (kHz) to users based on radio frequency conditions. This enhanced spectral efficiency is a great benefit to OFDM networks and makes them very well suited to high-speed data connections for both fixed and mobile users. Systems based on the emerging IEEE 802.16 standards are the only standardised OFDM-based Wireless Wide Area Networks (WWAN) infrastructure platforms today.

Service providers will operate WiMAX on licensed and unlicensed frequencies. The technology enables long distance wireless connections with theoretical speeds of up to 75 megabits per second (typical speeds will be lower depending upon how the service provider configures the base station for spectrum utilisation). Wireless WANs based on WiMAX technology cover a much greater distance than Wireless Local Area Networks (WLAN), connecting buildings to one another over a broad geographic area. WiMAX can be used for a number of applications, including "last mile" broadband connections, hotspot and cellular backhaul, and high-speed enterprise connectivity for businesses.

A Closer Look at the IEEE 802.16 Standard for Broadband Wireless

Drawing on the expertise of hundreds of engineers from the communications industry, the IEEE has established a hierarchy of complementary wireless standards. These include IEEE 802.15 for the Personal Area Network (PAN), IEEE 802.11 for the Local Area Network (LAN), 802.16 for the Metropolitan Area Network, and the proposed IEEE 802.20 for the Wide Area Network (WAN). Each standard represents the optimised technology for a distinct market and usage model and is designed to complement the others.

A good example is the proliferation of home and business wireless LANs and commercial hotspots based on the IEEE 802.11 standard. This proliferation of WLANs is driving the demand for broadband connectivity back to the Internet, which 802.16 can fulfill by providing the outdoor, long range connection back to the service provider. For operators and service providers, systems built upon the 802.16 standard represent an easily deployable “third pipe” capable of delivering flexible and affordable last-mile broadband access for millions of subscribers in homes and businesses throughout the world.

Designed from the Ground Up for Metropolitan Area Networks

In January 2003, the IEEE approved the 802.16a standard which covers frequency bands between two GHz and 11 GHz. This standard is an extension of the IEEE 802.16 standard for 10 – 66 GHz published in April 2002. In July of 2004 a revision to the 802.16a specification was ratified and is now referred to as the 802.16-2004 specification for fixed broadband access. These sub 11 GHz frequency ranges enable non line-of-sight performance, making the IEEE 802.16-2004 standard the appropriate technology for last-mile applications where obstacles like trees and buildings are often present and where base stations may need to be unobtrusively mounted on the roofs of homes or buildings rather than towers on mountains.

The most common 802.16-2004 configuration consists of a base station mounted on a building or tower that communicates on a point to multi-point basis with subscriber stations located in businesses and homes. 802.16-2004 has up to 30 miles of range with a typical cell radius of four – six miles. Within the typical cell radius, non-line-of-sight performance and throughputs are optimal. In addition, 802.16-2004 provides an ideal wireless backhaul technology to connect 802.11 wireless LANs and commercial hotspots with the Internet.

802.16-2004 wireless technology enables businesses to flexibly deploy new 802.11 hotspots in locations where traditional wired connections may be unavailable or time consuming to provision and provides service providers around the globe with a flexible new way to stimulate growth of the residential broadband access market segment. With shared data rates up to 75 Mbps utilising a 20MHz channel and a single “sector” of an 802.16-2004 base station – where sector is defined as a single transmit/receive radio pair at the base station – provides sufficient bandwidth to simultaneously support more than 60 businesses with T1-level connectivity and hundreds of homes with DSL-rate connectivity. To support a profitable business model, operators and service providers need to sustain a mix of high-revenue business customers and high-volume residential subscribers. 802.16-2004 helps meet this requirement by supporting differentiated service levels, which can include guaranteed T1-level services for business, or best effort DSL-speed service for home consumers.

The IEEE 802.16-2004 specification also includes robust security features and the Quality of Service needed to support services that require low latency, such as voice and video. The IEEE 802.16-2004 voice service can be either traditional Time Division Multiplexed (TDM) voice or Voice over IP (VoIP).

Broadband Wireless Access Applications

The IEEE 802.16-2004 standard will help the industry provide solutions across multiple broadband segments:

1. Cellular backhaul. Internet backbone providers in the U.S. are required to lease lines to third-party service providers, an arrangement that has tended to make wired backhaul relatively affordable. The result is that only about 20 per cent of cellular towers are backhauled wirelessly in the U.S. In Europe, where it is less common for local exchange carriers to lease their lines to competitive third parties, service providers need affordable alternatives. Subsequently, wireless backhaul is used in approximately 80 per cent of European cellular towers. With the potential removal of the leasing requirement by the FCC, U.S. cellular service providers will also look to wireless backhaul as a more cost-effective alternative. The robust bandwidth of 802.16-2004 technology makes it an excellent choice for backhaul for commercial enterprises such as hotspots as well as point-to-point backhaul applications.

2. Broadband on-demand. Last-mile broadband wireless access can help to accelerate the deployment of 802.11 hotspots and home/small office wireless LANs, especially in those areas not served by cable or DSL or in areas where the local telephone company may have a long lead time for provisioning broadband service. Broadband Internet connectivity is mission critical for many businesses, to the extent that these organisations may actually re-locate to areas where service is available. In today’s market, local exchange carriers have been known to take three months or more to provision a T1 line for a business customer, if the service is not already available in the building. Older buildings in metropolitan areas can present a tangle of wires that can make it difficult to deploy broadband connections to selected business tenants. 802.16-2004 wireless technology enables a service provider to provision service with speed comparable to a wired solution in a matter of days, and at significantly reduced cost. 802.16-2004 technology also enables the service provider to offer instantly configurable “on demand” high-speed connectivity for temporary events including trade shows that can generate hundreds or thousands of users for 802.11 hotspots. In these applications, operators use 802.16-2004 solutions for backhaul to the core network. Wireless technology makes it possible for the service provider to scale-up or scale-down service levels, literally within seconds of a customer request. “On demand” connectivity also benefits businesses, such as construction sites, that have sporadic broadband connectivity requirements. Premium “on demand” last-mile broadband services represent a significant new profit opportunity for operators.

3. Residential broadband: filling the gaps in cable and DSL coverage. Practical limitations prevent cable and DSL technologies from reaching many potential broadband customers. Traditional DSL can only reach about 18,000 feet (three miles) from the central office switch, and this limitation means that many urban and suburban locations may not be served by DSL connections. Cable also has its limitations. Many older cable networks have not been equipped to provide a return channel, and converting these networks to support high-speed broadband can be expensive.

The cost of deploying cable is also a significant deterrent to the extension of wired broadband service in areas with low subscriber density. The current generation of proprietary wireless systems is relatively expensive for mass deployments because, without a standard, few economies of scale are possible. This cost inefficiency will all change with the launch of standards-based systems based on 802.16. In addition, the range of 802.16-2004 solutions, the absence of a line of sight requirement, high bandwidth, and the inherent flexibility and low cost helps to overcome the limitations of traditional wired and proprietary wireless technologies.

4. Underserved areas. Wireless Internet technology based on IEEE 802.16 is also a natural choice for underserved rural and outlying areas with low population density. In such areas, local utilities and governments work together with a local Wireless Internet Service Provider (WISP) to deliver service. Recent statistics show that there are more than 2,500 WISPs who take advantage of license-exempt spectrum to serve over 6,000 markets in the U.S. [Source: ISP-Market 2002]. On an international basis, most deployments are in licensed spectrum and are deployed by local exchange carriers who require voice services in addition to high-speed data. This is because in these areas the wired infrastructure either does not exist or does not offer the quality to support reliable voice, let alone high-speed data. The term, “Wireless Local Loop” is often used to describe such applications, since it is used as a substitute for traditional copper phone wire in the local loop.

5. Best-connected wireless service. As the number of IEEE 802.11 hotspots proliferates, users will naturally want to be wirelessly connected, even when they are outside the range of the nearest hotspot. The IEEE 802.16e extension to 802.16-2004 introduces nomadic capabilities which will allow users to connect to a WISP even when they roam outside their home or business, or go to another city that also has a WISP.

Throughput, Scalability, QoS, and Security

Throughput - By using a robust modulation scheme, IEEE 802.16 delivers high throughput at long ranges with a high level of spectral efficiency that is also tolerant of signal reflections. Dynamic adaptive modulation allows the base station to tradeoff throughput for range. For example, if the base station cannot establish a robust link to a distant subscriber using the highest order modulation scheme, 64 QAM (Quadrature Amplitude Modulation), the modulation order is reduced to 16 QAM or QPSK (Quadrature Phase Shift Keying), which reduces throughput and increases effective range.

Scalability - To accommodate easy cell planning in both licensed and license-exempt spectrum worldwide, 802.16 supports flexible channel bandwidths. For example, if an operator is assigned 20 MHz of spectrum, that operator could divide it into two sectors of ten MHz each, or four sectors of five MHz each. By focusing power on increasingly narrow sectors, the operator can increase the number of users while maintaining good range and throughput. To scale coverage even further, the operator can re-use the same spectrum in two or more sectors by creating proper isolation between base station antennas.

Coverage - In addition to supporting a robust and dynamic modulation scheme, the IEEE 802.16 standard also supports technologies that increase coverage, including mesh topology and “smart antenna” techniques. As radio technology improves and costs drop, the ability to increase coverage and throughput by using multiple antennas to create “transmit” and/or “receive diversity” will greatly enhance coverage in extreme environments.

Quality of Service - Voice capability is extremely important, especially in underserved international markets. For this reason the IEEE 802.16-2004 standard includes Quality of Service features that enable services including voice and video that require a low-latency network. The grant/request characteristics of the 802.16 Media Access Controller (MAC) enables an operator to simultaneously provide premium guaranteed levels of service to businesses, such as T1-level service, and high-volume “best-effort” service to homes, similar to cable-level service, all within the same base station service area cell.

Security - Privacy and encryption features are included in the 802.16 standard to support secure transmissions and provide authentication and data encryption.

Operators’ Benefits from WiMAX

WiMAX has key benefits for operators. By choosing interoperable, standards-based equipment, the operator reduces the risk of deploying broadband wireless access systems. By deploying WiMAX, operators will enjoy economies of scale enabled by the standard help reduce monetary risk. Operators are not locked in to a single vendor because base stations will interoperate with subscriber stations from different manufacturers. Ultimately, operators will benefit from lower-cost and higher-performance equipment, as equipment manufacturers rapidly create product innovations based on a common, standards-based platform.

Rolling out of WiMAX

Intel sees WiMAX deploying in three phases: the first phase of WiMAX technology, based on IEEE 802.16-2004, will provide fixed wireless connections via outdoor antennas in the first half of 2005. Outdoor fixed wireless can be used for high-throughput enterprise connections (T1/E1 class services), hotspot and cellular network backhaul, and premium residential services.

As an industry leader of the WiMAX technology, Intel Corporation has recently previewed the first WiMAX “system-on-a-chip” design, code named “Rosedale,” for cost-effective customer premise equipment (CPE) that supports IEEE 802.16-2004. CPEs are placed at a home or business to transmit and receive a wireless broadband signal providing Internet connectivity.

In the second half of 2005, WiMAX will be available for indoor installation, with smaller antennas similar to 802.11-based WLAN access points today. In this fixed indoor model, WiMAX will be available for use in wide consumer residential broadband deployments, as these devices become "user installable," lowering installation costs for carriers.

By 2006, technology based on the IEEE 802.16e standards will be integrated into portable computers to support movement between WiMAX service areas. This allows for portable and mobile applications and services. In the future, WiMAX capabilities will even be integrated into mobile handsets.

While high-speed DSL and cable broadband access are only available to a fraction of computer users globally today, WiMAX will make it possible to build cost-effective, high-speed wireless connections to homes and businesses in urban and rural environments. Intel has focused its WiMAX development efforts on making it easier and more cost effective for the next generation of computer users to wirelessly access the high-speed Internet.

-ENDS-

For more information, please contact:

Debbie Sassine / Daniel Fitzpatrick Spectrum Communications Tel: (02) 9954 3299 Email: debbies@spectrumcomms.com.au / danielf@spectrumcomms.com.au

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