WiMAX - A new alternative for wireless broadband access

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WiMAX – A new alternative for wireless broadband access

Christian Hellwig
Eurescom
hellwig@eurescom.de

WiMAX is a new suite of air interface standards for combined fixed, portable and mobile broadband wireless access (MBWA). It offers very interesting features like a bandwidth of up to 75 Mbps, Quality of Service (QoS) establishment on a per-connection basis, strong security, and support for multicast and mobility. WiMAX uses licensed as well as license-exempt frequency bands between 2 and 66 GHz with channel widths between 1.25 and 20 MHz.

The upcoming WiMAX (Worldwide Interoperability for Microwave Access) products will allow carriers to wirelessly backhaul traffic, i.e. to carry cellular as well as hotspot traffic to the core network. WiMAX will also allow high-speed enterprise connectivity and reaching individual users in the drop segment, using an indoor Customer Premises Equipment (CPE) with non-line-of-sight (NLOS). With the revision of IEEE standard document 802.16e upcoming in 2005, also some mobility support will be provided. Revision 802.16f is intended to improve multi-hop functionality, and 802.16g is supposed to deal with efficient handover and improved QoS.

Evolution

IEEE 802.16 was originally design to be a radio standard for cost-effective last-mile broadband connectivity to users not served by wired broadband such as DSL or cable. By now, this WMAN (Wireless Metropolitan Area Network) standard is addressing a broader market for mobile, low-cost, high-speed broadband connections. It is optimized for high, bursty data-rates, but can simultaneously support real-time multimedia and isochronous applications such as Voice over IP (VoIP).

802.16 standards and deployment evolution.
(Source: Intel Technology Journal, Volume 8, Issue 3, 20 August 2004)

The frequency band between 10 and 66 GHz is provided for line-of-sight (LOS) solutions for a variety of licensed frequencies (10.5, 25, 26, 31, 38 and 39 GHz), the 2 to 11 GHz frequency band for non-line of sight (NLOS) solutions over both licensed and license-exempt frequencies. The minimum channel bandwidth for WiMAX is 1.75 MHz per channel, 10 MHz being considered as optimum. It remains to be seen what impact potential interference may have, especially on QoS commitments.

The current 802.16-2004 standard is the base standard and will be amended in 2005 by 802.16e, adding primarily some mobility support.

Different kinds of WiMAX products will be offered, likely covering the following areas:

Fixed wireless solutions using outdoor antennas (based on 802.16-2004), which can be used for cellular and hotspot backhaul, high-speed enterprise connectivity, and premium residential Internet services (e.g. high-speed Internet access, VoIP); available by mid 2005.
Smaller indoor antennas for fixed connections (based on 802.16-2004), for a broader residential high-speed Internet coverage, allowing for installation by the consumer; available by end of 2005.
Products for mobile terminals, supporting mobility and movement between different WiMAX service areas (based on 802.16e); available in the course of 2006.
Meshed networking or multi-hop (based on 802.16f ), where every Subscriber Station (SS) can also function as Base Station (BS), forwarding traffic from one SS to the next until it arrives finally at the BS.

Relationship between channel bandwidth, cell size, LOS/NLOS, and throughput. (Source: Laine, Boettle, Boscher, Feijt: Alcatel Strategy White Paper – WiMAX, making ubiquitous high-speed data services a reality, 28 June 2004)

Intel is already giving beta versions of its WiMAX chip “Rosedale”, which is based on 802.16-2004, to its development partners for first tests. Rosedale is a low-cost system-on-a-chip for WiMAX base stations.

Conclusion

WiMAX is a very interesting new development in the area of wireless broadband access. It is expected to be deployed by different kinds of network operators (wireless Internet service providers, cellular operators, DSL (Digital Subscriber Line) operators), using different business models.

Currently, Eurescom study P1446, “WiMAX in Backhaul and Access Networks”, is exploring IEEE 802.16 topics. The results will be available to the subscribers of the Eurescom study programme by end of January 2005.

Further information on Eurescom study P1446 is available at www.eurescom.de/public/projects/P1400-series/P1446/

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