Status and potential of 802.16a WiMAX
The IEEE 802.16a standard, approved in January 2003, provides wireless last-mile broadband access over the frequency bands between 2 and 11 GHz, a range that enables non-line-of-sight performance. This makes the IEEE 802.16a standard the appropriate technology for last-mile applications where obstacles like trees and buildings are present, or where base stations must be mounted on homes and buildings rather than towers and mountains.
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. 802.16a systems can help meet this requirement by supporting differentiated service levels. For example, a base station could simultaneously support more than 60 businesses with T1-level connectivity and hundreds of homes with DSL-rate connectivity.
WiMAX (the Worldwide Interoperability for Microwave Access Forum), an industry group with members representing equipment makers, component suppliers and service providers, is actively promoting the adoption of IEEE 802.16a compliant systems. The organisation is helping to ensure the compatibility and interoperability of broadband wireless access equipment.
The typical cell radius of 802.16a systems is expected to be four to six miles. This new standard will help the industry provide solutions across multiple broadband segments:
- Broadband on-demand - 802.16a wireless technology enables a service provider to provide service with speed comparable to a wired solution in a matter of days, and at significantly reduced cost. It also enables instantly configurable 'on demand' high-speed connectivity for temporary events such as trade shows.
- Cellular backhaul - The robust bandwidth of 802.16 technology makes it an excellent choice to carry backhaul traffic for cellular base stations in a point-to-point configuration.
- Residential broadband: filling the gaps in cable and DSL coverage - Practical limitations prevent cable and DSL technologies from reaching many potential broadband customers. This will change with the launch of standards-based systems based on 802.16a.
- 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.
- Best-connected wireless service - The IEEE 802.16e extension to 802.16a introduces nomadic capabilities which will allow users to connect while roaming outside their home areas.
Differentiating factors for 802.16a
By using a robust modulation scheme, IEEE 802.16a delivers high throughput at long ranges with a high level of spectral efficiency that is tolerant of signal reflections. The base station can also trade throughput for range. For example, if a robust link cannot be established using 64 QAM (quadrature amplitude modulation), changing to 16 QAM can increase effective range.
To accommodate easy cell planning in both licensed and licence exempt spectrum worldwide, 802.16a supports flexible channel bandwidths. For example, if an operator is assigned 20 MHz of spectrum, that operator could divide it into two sectors of 10 MHz each.
In addition to supporting a robust and dynamic modulation scheme, the IEEE 802.16a standard also supports technologies that increase coverage, including mesh topology and 'smart antenna' techniques.
Quality of service
The IEEE 802.16a standard includes quality of service features that enable services such as voice and video that require a low-latency network. 802.16a voice service can be either traditional time division multiplexed (TDM) voice over IP (VoIP).
Privacy and encryption features are included in the 802.16a standard to support secure transmissions and provide authentication and data encryption.
With the 802.16a standard in place, suppliers can amortise their research and development costs over much higher product volume. Just as important, for the millions of people around the world who cannot get access to broadband connectivity via cable or DSL, the new IEEE 802.16a wireless technology will enable a 'third pipe' to connect homes, businesses, public 802.11 hot spots and communications cafes to the many benefits of the internet.
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