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Key Considerations in Developing Mobile WiMAX Systems

Wed, 08/08/2007 - 12:26pm
Byron Young, Adaptix Inc.

Mobile WiMAX is poised to be the next big opportunity for equipment vendors and for the communications industry in general. It promises per-user bandwidth at
multimegabit rates, boosts spectral efficiency and supports IP convergence out to the network edge. Based on the IEEE 802.16e standard, Mobile WiMAX will provide personal broadband at up to 150 km/hour. All of these elements have made Mobile WiMAX a high priority development both for suppliers and operators, all of whom are positioning to be the new leaders in 4G networking.

However, it may not be a simple move for suppliers to make. Previous changes to networking equipment and handsets have been incremental and evolutionary. As a true 4G technology, Mobile WiMAX represents a revolutionary change from existing technologies. Developers looking to create successful Mobile WiMAX-compliant systems have three basic challenges they must face: 1) new technical challenges, 2) interoperability and certification cycles, and 3) Intellectual Property Rights (IPR) issues.

Getting Technical
With a legacy in the initial IEEE 802.16-2004 and later 802.16e-2005 standards, Mobile WiMAX has its basis in firm standards and gives developers a clear path for working toward an interoperable technology. Of course, base station and subscriber device manufacturers face a series of technical challenges. Mobile WiMAX is still a new technology, and it includes key areas of new innovation for developers. The following are some of those key areas:

1. OFDMA Physical Layer. IEEE 802.16e-2005 is the first widely embraced standard to be based on Orthogonal (OFDMA). OFDMA is a multiple access transmission format that can supply significant gains in spectral efficiency, with particular advantages in mobile applications. Unlike legacy OFDM applications (e.g. 802.11a/g, Fixed WiMAX, etc.), OFDMA utilizes on-the-fly allocation of subcarriers and timeslots to individual subscribers based on bandwidth needs and dynamic signal and noise conditions. If implemented correctly, OFDMA offers higher bandwidths over less spectrum, making it the best fit for not only WiMAX, but for other 4G communications systems, as well.

2. RF Front End Technology. OFDMA systems require RF sections with high dynamic range. That means OFDMA systems may require amplifiers that are more powerful than those used in legacy systems. These higher-powered amplifiers prevent OFDMA systems from "clipping" when under peak conditions. An increasing number of new WiMAX-specific RF components are now available and include RF management devices, high-efficiency amplifiers and filters, all of which help to reduce development and manufacturing costs.

3. Software Defined Radios. The Software Defined Radio (SDR) platforms built on new hardware architectures driven by state-of-the-art programmable DSPs and FPGAs are ideal in supporting the large number of features and flexibility required in Mobile WiMAX standards. If designed properly, an OFDMA-based Mobile WiMAX system could also support other OFDMA standards such as 3GPP Long Term Evolution (LTE).

4. IP Convergence. Mobile WiMAX utilizes end-to-end IP networking. That requires network processing, policy management and security to be implemented in Radio Access Network (RAN) components that are outside of the network core. Mobile WiMAX RANs will need to integrate IP stacks, layer 3 switching/routing and layer 1/2/3 QoS. More recently, some software vendors have begun delivering complete Mobile WiMAX software stacks, making it easier and faster to implement subscriber devices and base stations.

As Mobile WiMAX technology continues to mature, many of these issues will be resolved, especially with "off-the-shelf" merchant silicon solutions increasing in availability.

Certification and Interoperability
From the very beginning, Mobile WiMAX has been created to be a highly interoperable technology pointed toward eventual certification. As such, it has always been designed to minimize deployment risk. Though documents such as IEEE 802.16e and WiMAX Forum technical specifications provide Mobile WiMAX a major advantage, designing to standards does not guarantee interoperability between vendors, who often interpret standards differently. However, these diverse interpretations are usually clarified in updates such as the upcoming Corrigenda 2 for 802.16e.

Even so, practical interoperability must be planned and executed carefully. To achieve interoperability, developers must commit engineering resources and time. As part of that commitment, vendors should be participating in multiple interoperability tests — particularly those promoted by the WiMAX Forum as part of its "Plugfest" program.

In addition to helping ensure multi-vendor operation, Plugfests act as a sort of dress rehearsal for WiMAX Forum certification. Like other certification programs, such as CableLabs’ DOCSIS, WiMAX Forum certification is a key vendor requirement for many carriers selecting Mobile WiMAX equipment.

Intellectual Property
In the past, Intellectual Property Rights were often treated as background issues. In today’s world, both vendors and operators alike have become highly aware of patent issues. Recent examples in the area of telecommunications have demonstrated that not only product shipments, but carrier services, as well, could be affected by IPR legal cases.

In the area of Mobile WiMAX, IPR is a key issue that is being closely scrutinized. Chief among IPR considerations are the basic methods describing OFDMA and how it can be applied to mobile applications in a cellular environment.

Many of the potential IPR conflicts can be avoided through proper planning and dialogue with key IPR holders. Through the implementation of licensing programs, the Mobile WiMAX industry can flourish with appropriate business cases for all parties.

Final Thoughts
Mobile WiMAX developers face several technical, testing and IPR challenges, but the good news is that the issues are reasonably manageable with proper planning and investment. With continued focus from developers and increased interest and commitment from communications carriers, Mobile WiMAX can become the first wide area wireless standard to supply a mass deployment conduit for high-impact content-rich services supported by a new generation of mobile multimedia devices. About the Author

As the vice president, marketing and product management, Byron Young is responsible for market strategy, product planning and industry relations for ADAPTIX. In his more than 20 years in the telecom and datacom industries, Young served as the vice president of marketing for Transat Technologies. There, he led the company’s strategic planning and product management functions.

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