WiMAX: Broadband Wireless Acces

WiMAX (Worldwide Interoperability for Microwave Access) is the IEEE 802.16 standards-based wireless technology that provides MAN (Metropolitan Area Network) broadband connectivity. WiMAX is an Air Interface for Fixed Broadband Wireless Access Systems, also known as the IEEE WirelessMAN air interface. WiMAX-based systems can be used to transmit signals as far as 30 miles. So far, WiMAX can offer a solution to what is normally called the "last-mile" problem by connecting individual homes' and business offices' communications.

Cable/DSL Broadband Access

Currently, there are cable and DSL broadband access services in the marketplace. But, their practical limitations in features and deployment have prevented them from reaching many potential broadband Internet customers. The wired broadband connection provided by cable and DSL is an all-consuming and expensive process. A large number of areas throughout the world currently are not able to access broadband connectivity. Traditionally, 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 connectivity. The limitation of cable is that many older cable networks have not been equipped to offer a return channel, and converting and deploying these networks to support high-speed broadband can be expensive.

Wireless Standards

Drawing on hundreds of experts in the telecommunications industry, the IEEE has established a collection of wireless standards that include IEEE 802.15, also known as Bluetooth, for the Personal Area Network (PAN); IEEE 802.11, also known as WiFi, for the Local Area Network (LAN); 802.16 for the Metropolitan Area Network (MAN), and IEEE 802.20 for the Wide Area Network (WAN).

Unlike WiFi, WiMAX's range is typically measured in miles rather than feet. The main distinction of the difference between the two standards means that WiFi is focused on a local-area networking (LAN) technology and that WiMAX is a MAN technology.

The 802.16d standard of extending 802.16 supports three physical layers (PHYs). The mandatory PHY mode is 256-point FFT Orthogonal Frequency Division Multiplexing (OFDM). The other two PHY modes are Single Carrier (SC) and 2048 Orthogonal Frequency Division Multiple Access (OFDMA) modes. By the way, the corresponding European standard—the ETSI HiperMAN standard—defines a single PHY mode identical to the 256 OFDM modes in the 802.16d standard.

Why WiMAX?

WiMAX covers a couple of different frequency ranges. Basically, the IEEE 802.16 standard addresses frequencies from 10GHz to 66GHz. The 802.16a specification, which is an extension of IEEE802.16, covers bands in the 2GHz-to-11GHz range. WiMAX has a range of up to 30 miles with a typical cell radius of 4–6 miles.

WiMAX's channel sizes range from 1.5 to 20MHz as well, and offer a WiMAX-based network the flexibility to support a variety of data transmitting rates such as T1 (1.5Mbps) and higher data transmitting rates of up to 70Mbps on a single channel that can support thousands of users. This flexibility allows WiMAX to adapt to the available spectrum and channel widths in different countries or licensed to different service providers.

WiMAX supports ATM, IPv4, IPv6, Ethernet, and VLAN services. So, it can provide a rich choice of service possibilities to voice and data network service providers. In addition, WiMAX provides an ideal wireless backhaul technology to connect 802.11 wireless LANs and commercial hotspots with the Internet.

The WiMAX-based solution is set up and deployed like cellular systems using base stations that service a radius of several miles/kilometers. The most typical WiMAX-based architecture includes a base station mounted on a building and is responsible for communicating on a point to multi-point basis with subscriber stations located in business offices and homes. The customer premise equipment (CPE) will connect the base station to a customer as well; the signal of voice and data is then routed through standard Ethernet cable either directly to a single computer, or to an 802.11 hot spot or a wired Ethernet LAN.

WiMAX-based solutions include many other advantages, such as robust security features, good QoS (Quality of Service), and mesh and smart antenna technology that will allow better utilization of the spectrum resources. Also, the WiMAX-based voice service can work on either traditional Time Division Multiplexed (TDM) voice or IP-based Voice, also known as Voice over IP (VoIP).

WiMAX Connectivity and Solutions

WiMAX allows equipment vendors to create many different types of IEEE802.16-based products, including various configurations of base stations and customer premise equipment (CPE). WiMAX also allows the services provider to deliver many types of wireless access services. The WiMAX can be used on a variety of wireless broadband connections and solutions:

• "Last Mile" Broadband Access Solution—Metropolitan-Area Networks (MAN) connections to home and business office, especially in those areas that were not served by cable or DSL or in areas where the local telephone company may need a long time to deploy broadband service. The WiMAX-based wireless solution makes it possible for the service provider to scale-up or scale-down service levels in short times with the client request.
• Backhaul networks for cellular base stations, bypassing the Public Switched Telephone Network (PSTN); the cellular service providers can look to wireless backhaul as a more cost-effective alternative. The robust WiMAX technology makes it a nice choice for backhaul for enterprises such as hotspots as well as point-to-point backhaul solutions.
• Backhaul enterprise connections to the Internet for WiFi hotspots. It will allow users to connect to a wireless Internet service provider even when they roam outside their home or business office.
• A variety of new business services by wireless Internet service provider.

Who Are Working on WiMAX?

The WiMax Forum is a non-profit organization formed in 2001 by Nokia Corp. and Ensemble Communications Inc., etc. Right now, the WiMAX Forum has more than 110 members of equipment, semiconductor suppliers, and services providers such as Alcatel, AT&T, Fujitsu, Intel, Nortel, Motorola, SBC and Siemens, and so forth. The WiMax Forum aims to support wireless metropolitan-area networking products based on IEEE 802.16, like the Wi-Fi Alliance has done for wireless LANs and IEEE 802.11. The WiMAX Forum has most recently been working to promote the adoption of IEEE 802.16-compliant equipment, certification, and interoperability testing. In 2003, Intel Corp. became a major supporter of the WiMax Forum.

In order to bring interoperability into MAN, the WiMAX Forum is focusing its efforts on establishing a baseline protocol that allows equipment and devices from multiple vendors to interoperate and that also provides a choice to buy equipment and devices from different suppliers.

Currently, there are no WiMax-certified products yet available in the market, but the race is already on. At the Intel Developer Forum in September 2004, Intel showed off its first samples of a WiMAX chipset that has been named Rosedale. Intel is planning to offer WiMax transmitters by 2005, and expects to ship WiMax devices for the home and office to take off by 2006. Also, Intel hopes that notebooks will begin to incorporate WiMAX technology during 2006, and by 2007, handsets for mobility will be available. Intel has already signed up Proxim and Alcatel to develop WiMAX base-station and CPE (Customer Premises Equipment) kits. Fujitsu Microelectronics America Inc. in early 2005 expects to introduce a new WiMAX-based single-chip solution for deployment in base stations and subscriber stations as well; the product integrates both PHY and MAC functionality. Siemens Information and Communication Mobile also plans to build complete WiMAX-based solutions for establishing fixed, broadband speed metropolitan area wireless radio networks.

About the Author

Xiaole Song is a professional designing, integrating and consulting Telecommunication, IP Telephony, Computer Telephony Integration, and Speech applications. Feel free to e-mail any comments about this article to xiaole_song@yahoo.com.

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