IEEE 802.16* and WiMAX*: broadband wireless access for everyone
By Margaret LaBrecque, President, WiMAX™ Forum
Margaret is Director of Industry Programs for Intel’s Broadband Wireless Division. At Intel since 1994, she has lead development of Intel platforms to support high-speed connectivity delivered via datacasting, Ethernet, cable modem and wireless. She was recently elected President of the WiMAX™ Forum (www.wimaxforum.org) which certifies interoperability of systems conforming to the IEEE 802.16* and ETSI HiperMAN* standards for Metropolitan Area Networks.
Margaret holds a Master’s degree in Electrical Engineering from MIT in Adaptive Signal Processing and an MBA from the Stanford Graduate School of Business.
Introduction: 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 optimized 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 wireless LANs (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
The most common 802.16a 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. 802.16a has a range of up to 30 miles with a typical cell radius of 4–6 miles. Within the typical cell radius, non-line-of-sight performance and throughputs are optimal. In addition, 802.16a provides an ideal wireless backhaul technology to connect 802.11 wireless LANs and commercial 802.11 hotspots with the Internet. 802.16a 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, a single “sector” of an 802.16a 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, using 20 MHz of channel bandwidth. 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 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 802.16 specification also includes robust security features and the Quality of Service needed to support services that require low latency, such as voice and video. 802.16 voice service can be either traditional Time Division Multiplexed (TDM) voice or Voice over IP (VoIP).
Broadband wireless access applications
Throughput, scalability, QoS, and security
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 10 MHz each, or 4 sectors of 5 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 undeserved international markets. For this reason the IEEE 802.16a 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.
Benefits of standards
Standards also specify minimum performance criteria for equipment, enabling a common broadband wireless access baseline platform that equipment manufacturers can use as the foundation for ongoing innovations and faster time-to-market. With its broad industry support, the 802.16 standard lets device manufacturers and solutions vendors do what they do best, achieving overall price/performance improvements and opening mass-market opportunities that cannot be equalled by proprietary approaches.
WiMAX* focuses on interoperability
In an effort to bring interoperability to Broadband Wireless Access, WiMAX is focusing its efforts on establishing a unique subset of baseline features grouped in what is referred to as “System Profiles” that all compliant equipment must satisfy. These profiles will establish a baseline protocol that allows equipment from multiple vendors to interoperate, and that also provides system integrators and service providers with the ability to purchase equipment from more than one supplier. System Profiles can address the regulatory spectrum constraints faced by operators in different geographies. For example, a service provider in Europe1 operating in the 3.5 GHz band who has been allocated 14 MHz of spectrum is likely to want equipment that supports 3.5 and/or 7 MHz channel bandwidths and TDD (time-division duplex) or FDD (frequency-division duplex) operation. Similarly, a WISP in the U.S. using license-exempt spectrum in the 5.8 GHz UNII band may desire equipment that supports TDD and a 10 MHz bandwidth. WiMAX will establish a structured compliance procedure based upon the proven test methodology specified by ISO/IEC 96462.
The process starts with standardized Test Purposes written in English, which are then translated into Standardized Abstract Test Suites in a language called TTCN3. In parallel, the Test Purposes are also used as input to generate test tables referred to as the PICS (Protocol Implementation Conformance Statement) pro forma. The end result is a complete set of test tools that WiMAX will make available to equipment developers so they can design in conformance and interoperability during the earliest possible phase of product development. Typically, this activity will begin when the first integrated prototype becomes available.
Ultimately, the WiMAX suite of conformance tests, in conjunction with interoperability events, will enable service providers to choose from multiple vendors of broadband wireless access equipment that conforms to the IEEE 802.16a standard and that is optimized for their unique operating environment. Internationally, WiMAX will work with ETSI, the European Telecommunications Standards Institute, to develop similar test suites for the ETSI HIPERMAN standard for European broadband wireless metropolitan area access.
WiMAX has key benefits for operators. By choosing interoperable, standards-based equipment, the operator reduces the risk of deploying broadband wireless access systems.
Intel Corporation and the IEEE 802.16 standard
High-speed wireless broadband technology based on the IEEE 802.16 standard promises to open new, economically viable market opportunities for operators, wireless Internet service providers, and equipment manufacturers. The flexibility of wireless technology, combined with the high throughput, scalability, long range and Quality of Service features of the IEEE 802.16 standard will help fill the broadband coverage gaps and reach millions of new residential and business customers worldwide. The WiMAX Forum* is an industry group focused on creating system profiles and conformance programs to help ensure interoperability among devices from different manufacturers. Intel is actively participating in these industry efforts to help reduce investment risks for operators and service providers while enabling them to more cost effectively take advantage of the tremendous market potential of wireless broadband access.
2. IEC is the International Electrotechnical Commission, a leading global organization that publishes international standards for all electrical, electronic, and related technologies.
3. TTCN: Tree and Tabular Combined Notation.
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