What Is Mobile Wimax

What is mobile WiMAX? Designed to leverage the IP infrastructure to deliver high-speed data to handsets, PDAs, and other mobile devices mobile WiMAX can compete with or complement cellular. By Jack Shandle Page 1 of 2 Wireless Net DesignLine (07/11/2006 7:49 PM EDT) The first mobile WiMAX products are scheduled to be rolled out late this year or very early in 2007—so if you haven't done some research into this interesting technology already it's time to start. Designed from the beginning to connect to the IP network, mobile WiMAX offers low latency and high Quality of Service (QoS). It will have no difficulty accessing IP multimedia data or implement technologies such as VoIP. This is the basic argument driving the mobile WiMAX campaign for market acceptance. In the ever widening world of wireless technologies, mobile WiMAX is aimed at a very lucrative market: the delivery of high-data bandwidth digital data streaming off the IP network. In other words, the much-talked-about delivery of mobile services. Cellular, Wi-Fi and even Bluetooth through its relationship with Ultrawideband (UWB) also have designs on the multimedia services market. While there is still some question as to whether there is room for still another wireless technology, WiMAX has a good story to tell. Mobile WiMAX can be embedded on any number of personal devices such as PDAs, notebook PCs, game consoles, iPods, MP3 players, and cellular phones. As such, its potential to compete with cellular technology is obvious, particularly for broadband, datacentric applications. WiMAX and cellular But mobile WiMAX may also co-exist with cellular technology. WiMAX is not optimized to carry circuit-switched voice traffic. From the WiMAX perspective, voice is a far more appropriate application for cellular technology. The problem with that scenario from the cellular perspective is that the expected growth in mobile revenue is in the data segment. Between 2004 and 2008, a 20% CAGR is forecast for mobile data while revenue for mobile voice traffic is actually expected to drop by a few percent over the same period. Voice revenues will still be almost double data in 2008 but the trend is clear.

The single most important technology advantage that mobile WiMAX has over 2G and 3G cellular is its adoption of Orthogonal Frequency Division Multiple Access (OFDMA) multiplexing. OFDMA works well in multipath environments and is cost effective for network operators because it has higher performance and gives them more flexibility in managing spectrum resources. Mobile WiMAX performance is typically compared to 3G technologies such as EVDO (Evolution Data Optimized) and HSDPA (High Speed Downlink Packet Access), and HSUPA. Depending on system configuration, mobile WiMAX has a clear performance edge. In terms of net throughput per channel, mobile WiMAX delivers between 50% and 3X greater bandwidth, the greatest differential coming in a WiMAX system with a twoantenna MIMO (Multiple In Multiple Out) implementation. The WiMAX Forum published the data on which this comparison is based. The information is shown in Figure 1. MIMO is just as applicable to cellular technology but has not been implemented as yet. Click here for Figure 1 Figure 1: Mobile WiMAX beats 3G cellular in data bandwidth. The cellular industry is, of course, not standing still. The Third Generation Partnership Project (3GPP) has incorporated it in its LTE (Long Term Evolution) specification. Another indication is that Qualcomm, ever a dominant player in the cellular market, last year signaled its interest in OFDMA by acquiring Flarion, a company that had developed an excellent OFDMA technology. Another contributor to mobile WiMAX's performance edge is that it uses Time Division Duplex (TDD) to separate channels and that is attractive for the implementation of other technologies that boost performance. TDD is less complex than FDD (Frequency Division Duplex) technology favored by the cellular industry. TDD uses a single frequency channel, separating uplink and downlink traffic with a guard time. It is the use of the single channel for uplink an downlink that makes it easier to implement MIMO and beamforming technologies that it depends on for a good part of its advantage over 3G cellular. Mobile WiMAX basics Mobile WiMAX is based on the IEEE 802.16e-2005 standard. Although it will probably migrate to higher levels of the RF spectrum later, it is presently capable of operating in the 2.3 GHz, 2.5 GHz, and 3.3-3.8 GHz spectrum bands. Channel sizes range from 3.5 MHz to 10 MHz, which provides the flexibility mobile operators need to make the optimal use of the spectrum available to them.

The WiMAX Forum will begin mobile WiMAX late this year or early in 2007. Although handoffs and power saving mechanisms are required of all mobile WiMAX products, it is anticipated that features such as high-speed handoffs, roaming, and MIMO will all be available after the middle of 2007. Because any deployment of mobile services will have to find some way to deal with multiple networks (3G core, LTE, Wi-Fi, 3G RN, and mobile WiMAX), the industry is developing architectures that will let service providers utilize them all with minimum economic impact. From the IP side, IP Multimedia Subsystems (IMS) will also service providers to deliver all the services—both now and in the future—that the Internet provides. Network operators will be able to control and charge for each service. As a consequence of its flexible, layered architecture, IMS also gives service providers the ability to independently develop applications. Coming from the cellular side, Multimedia Domain (MDD) does essentially the same thing. WiMAX supports both IMS and MDD, although network operators do not have to implement IMS or MDD to take advantage of core WiMAX capabilities. Economic perspective The case for mobile WiMAX being a cost effective technology is fundamentally one of standards and interoperability. Equipment must conform to the IEEE 802.16e-2005 and ETSI HiperMAN 1.3.2 standards but it is well known that meeting those standards does not necessarily translate into interoperability between products from different manufacturers. For mobile WiMAX, the WiMAX Forum will reprise its interoperability certification program for fixed WiMAX. Interoperability allows system operators to shop around for base stations and end user equipment as well as decide when to upgrade. One of the more interesting synergies between technologies brings together mobile WiMAX and Wi-Fi capability in a single chipset. The rationale behind this combination is that mobile WiMAX is better suited for roaming and Wi-Fi is a technology that is better suited for offices and other interior spaces. This perspective is not as popular with the Wi-Fi camp as it is with the WiMAX proponents. But the combination of the two technologies into a single chipset would certainly bring down the cost of end-user equipment. Perhaps the biggest cost advantage of WiMAX compared to cellular comes not out of standards or higher levels of integration but royalty payments. Royalties paid by manufacturers of WCDMA phones, for example, average between 10% and 15% for the average selling price of the phone. This is big difference from the 2% to 5% royalty charges in the rest of the telecommunications industry. Significantly, the WiMAX Forum is clearly looking for royalty solutions that are far less onerous.

Potential scenarios As a high capacity IP-based wireless technology, WiMAX can either overlay an existing 3G network and provide higher performance data delivery. Its technology mix (OFDMA and TDD) and its synergies with other wireless technologies such as Wi Fi, make it a good bet to at least find a niche if not become a major competitor to cellular. Mobile WiMAX's appeal is, perhaps, most keenly felt by 2G operators that what to leapfrog their 3G competitors. But 3G operators may find it appealing as well. Korea Telecom, for example, is already deploying its WiBro services, which are based on mobile WiMAX. In addition, DSL service providers and cable providers may find mobile WiMAX valuable in areas where their wired network does not deliver good performance. WiMAX may also be a good choice in greenfield projects where virtually no infrastructure exists. Only time will tell.