WiMAX--future comms?

WiMAX is an acronym that stands for Worldwide Interoperability for Microwave Access, a certification mark for products that pass conformity and interoperability tests for the IEEE 802.16 standards.

Products that pass the conformity tests for WiMAX are capable of forming wireless connections between them to permit the carrying of internet packet data. It is similar to WiFi in concept, but has certain 'improvements that are aimed at improving performance and should permit usage over much greater distances.

IEEE 802.16 is working group number 16 of IEEE 802, specializing in point-to-multipoint broadband wireless access.

Technical advantages over WiFi

Because IEEE 802.16 networks use the same LLC layer (standardized by IEEE 802.2) as other LANs and WANS, it can be both bridged and routed to them. An important aspect of the IEEE 802.16 is that it defines a MAC layer that supports multiple physical layer (PHY) specifications. This is crucial to allow equipment makers to differentiate their offerings. This is also an important aspect of why WiMAX can be described as a "framework for the evolution of wireless broadband" rather than a static implementation of wireless technologies. Enhancements to current and new technologies and potentially new basic technologies incorporated into the PHY (physical layer) can be used. A converging trend is the use of multi-mode and multi-radio SoCs and system designs that are harmonized through the use of common MAC, system management, roaming, IMS and other levels of the system. WiMAX may be described as a bold attempt at forging many technologies to serve many needs across many spectrums.

The MAC is significantly different from that of WI-FL (and ethemet from which Wi-Fi is derived.

MAC uses contention access-all subscriber stations wishing to pass data through an access point are competing for the AP's attention on a random basis. This can cause distant nodes from the AP to be repeatedly interrupted by less sensitive, closer nodes, greatly reducing their throughput. By contrast, the P,02.16 MAC is a scheduling MAC where the subscriber station only has to compete once (for initial entry into the network). After that it is allocated a time slot by the base station. The time slot can enlarge and constrict, but it remains assigned to the subscriber station meaning that other subscribers are not supposed to use it but take their Wm. This scheduling algorithm is stable under overload and oversubscription (unlike 802.11). It is also much more bandwidth efficient. The scheduling algorithm also allows the base station to control Quality of Service by balancing the assignments among the needs of the subscriber stations.

A recent addition to the WiMAX standard is underway which will add Ml mesh networking capability by enabling WiMAX nodes to simultaneously operate in 'subscriber station" and "base station" mode. This will blur that 'initial distinction and allow for widespread adoption of WiMAX based mesh networks and promises widespread WiMAX adoption.

The original WiMAX standard, IEEE 802.16, specifies WiMAX in the 10 to 66 GHz range. 802.16a added support for the 2 to 11 GHz range, of which most parts are already unlicensed internationally and only very few still require domestic licenses. Most business interest will probably be in the 802.16a standard, as opposed to licensed frequencies. The WiMAX specification improves upon many of the limitations of the Wi-Fi standard by providing increased bandwidth and stronger encryption. It also aims to provide connectivity between network endpoints without direct line of sight in some circumstances. The details of performance under non-line of sight (NLOS) circumstances are unclear as they have yet to be demonstrated. It is commonly considered that spectrum under 5-6 GRz is needed to provide reasonable NLOS performance and cost effectiveness for PtM (point to multi-point) deployments. WIMAX makes clever use of multi-path signals but does not defy the laws of physics.

Uses for WiMAX

WiMAX is a wireless metropolitan area network (MAN) technology that can connect IEEE 802.11 (Wi-Fi) botspots with each other and to other parts of the Internet and provide a wireless alternative to cable and DSL for last mile (last kin) broadband access. IEEE 802.16 provides up to 50 km (31 miles) of linear service area range and allows connectivity between users without a direct line of sight. Note that this should not be taken to mean that users 50 km (31 miles) away without line of sight will have connectivity. Practical limits from real world tests (http-//www.theregister.co.uk/2005/10127/ wimax_world_att_trial/) seem to be around "3 to 5 miles" (5 to 8 kilometers). The technology has been claimed to provide shared data rates up to 70 Mbit/s, which, according to WIMAX proponents, is enough bandwidth to simultaneously support more than 60 businesses with T1-type connectivity and well over a thousand homes at 1Mbit/s DSL-level connectivity. Real world tests (http//ww. theregister.co. uk/2005/10/27/wimax_world att trial/), however, show practical maximum data rates between 500kbit/s and Mbit/s. depending on conditions at a given site. It is also anticipated that WIMAX will allow interpenetration for broadband service provision of VoIP, video, and Internet access-simultaneously. Most cable and traditional telephone companies are closely examining or actively trial-testing the potential of WIMAX for 'last mile" connectivity. This should result in better pricepoints for both home and business customers as competition results from the elimination of the "captive" customer bases both telephone and cable networks traditionally enjoyed. Even in areas without preexisting physical cable or telephone networks, WIMAX could allow access between anyone within range of each other. Home units the size of a paperback book that provide both phone and network connection points are already available and easy to install.

There is also interesting potential for interoperability of WiMAX with legacy cellular networks. WIMAX antennas can "share' a cell tower without compromising the function of cellular arrays already in place.

Companies that already lease cell sites in widespread service areas have a unique opportunity to diversify, and often already have the necessary spectrum available to them (i.e. they own the licenses for radio frequencies important to increased speed and/or range of a WiMAX connection). WiMAX antennae may be even connected to an Interact backbone via either a light fiber optics cable or a directional microwave link. Some cellular companies are evaluating WiMAX as a means of increasing bandwidth for a variety of data-intensive applications. In line with these possible applications is the technology's ability to serve as a very high bandwidth "backhaul" for Internet or cellular phone traffic from remote areas back to a backbone. Although the cost-effectiveness of WiMAX in a remote application will be higher, it is definitely not limited to such applications, and may in fact be an answer to expensive urban deployments of T1 backhauls as well. Given developing countries' (such as in Africa) limited wired infrastructure, the costs to install a WiMAX station in conjunction with an existing cellular tower or even as a solitary hub will be diminutive 'in comparison to developing a wired solution. The wide, flat expanses and low population density of such an area lends itself well to WiMAX and its current diametrical range of 30 miles. For countries that have skipped wired infrastructure as a result of inhibitive costs and unsympathetic geography, WiMAX can enhance wireless infrastructure in an inexpensive, decentralized, deployment-friendly and effective manner.

Another application under consideration is gaming. Sony and Microsoft are closely considering the addition of

WiMAX as a feature in their next generation game console. This will allow garners to create ad hoc networks with other players. This may prove to be one of the "killer apps" driving WiMAX adoption: WiFi-like functionality with vastly improved range and greatly reduced network latency and the capability to create ad hoc mesh networks.

'Mat is due to embedding WiMAX into the system processors and board architectures for laptop, PDA and other devices. Of course, the price is not zero as premium features drives acceptance of premium 'Intel Inside' driven designs. But as a competitive positioning strategy, the ability to embed multi-mode WiMAX/WiFi/cellular into consumer and IT products should create a compelling argument for WiMAX's acceptance.

WiBro:South Korean version

Perhaps the most telling deployments for WiMAX will be for the WiBro mobile derivative: WiBro has South Korean government support with the requirement for each carrier to spend over $1 billion US for deployments. The Koreans sought to develop WiBro as a regional and potentially international alternative to 3.5-4G systems. But given the lack of self developed momentum as a standard, WiBro has joined WiMAX and agreed to harmonize with the similar OFDMA 902.16c version of die standard. What makes WiBro roll outs, which will start in April of 2006, a good 'test case' for the overall WlMAX effort is that it is mobile, well thought out for delivery of wireless broadband services, and the fact that the deployment is taking pine in a highly sophisticated, broadband saturated market. WiBro will go up against 3G and very high bandwidth wire "c services rather than as gap-filler or rural under-served market deployments as is often exampled as the 'best fit' markets for WiMAX. WiBro goes much more "in your face" in direct competition with 3G and high bandwidth wired services which pose tough competition.

Targetting Network SPs not Consumers

Early products are likely to be aimed at network service providers (SPs) and businesses, not consumers. It has the potential to enable millions more to have wireless Internet connectivity, cheaply and easily. Proponents say that WIMAX wireless coverage will be measured in square kilometers while that of Wi-Fi is measured in square meters. According to WIMAX promoters, each WIMAX node or "base station" would enable high-speed Internet connectivity between homes and businesses in a radius of up to 50 km (31 miles). (it should be noted that these claims, especially that such distances can be achieved without LOS (line of sight), represent, at best, a theoretical maximum under ideal circumstances. The technical merit of these claims has yet to be tested in the real world,) (If you are planning on 'investing $$ in this to get a usable grade of service, do the RF link budget analysis with accompanying signal strength simulations in a multi-node environment specifying antenna gain/height and path losses) These base stations will eventually cover an entire metropolitan area, making that area into a WiMAN and allowing true wireless mobility within it, as opposed to hot-spot hopping required by Wi-Fi. Its proponents are hoping that the technology will eventually be used in notebook computers and PDAS. True roaming cell-like wireless broadband, however, will require 802.16c. Qualcomm acquires Flarion The acquisition of Flarion [I] (http://www.flarion.com) by mobile wireless heavyweight Qualcomm and the re--posturing of their systems and OFDM patent portfolios as being central to OFDMA/802.16e developments has broadened the level of interest in the emerging field of OFDM wireless. Some question the motives of Qualcomm: is this an attempt to switch adoption of WiMAX? Or is this more a recognition by Qualcomm that OFDM will likely become a predominant core technology for 4G and beyond wireless systems? Intel Wimax Collaborations with Nokia, Intel in 2005 In June, Nokia and Intel Corporation announced a cooperation to accelerate the development, adoption and deployment of (IEEE 802.16c) Areas of development include mobile clients, network infrastructure, industry-enabling efforts and market development. For mobile devices and notebook platforms, base station strategies to help deploy a WiMAX network infrastructure that will provide adequate and reliable coverage.

Motorola Inc. and Intel Corporation announced on October, 2005, their plan to collaboratively adoption of mobile WiMAX based on the proposed IEEE 802.16c standard, for both fixed and wireless broadband applications. Interoperability testing of Motorola mobile devices, network equipment, and customer premises equipment with Intel products.

Standards

IEEE 802.16-2005, approved December, 2005, (formerly named 802.16e), the WiMAX mobility standard, is an improvement on the modulation schemes stipulated in the original WiMAX standard. It allows for fixed wireless and mobile Non Line of Sight (NLOS) applications primarily by enhancing the OFDMA (Orthogonal Frequency Division Multiplexing Access).

Many think that by stipulating a new modulation method called Scalable OFDMA (SOFDMA), 802.16-2005 will

make the older 802.16-2004 which uses OFDM-256 obsolete. However, several manufacturers plan for a migration path from the older version of the standard to the more robust, mobile modulation scheme. In any case, manufacturers are working through the WiMAX Forum to achieve compatibility between similar system profiles.

SOFDMA will improve upon OFDM256 for NLOS applications by:

* Improving NLOS coverage by utilizing advanced antenna diversity schemes, and hybrid-Automatic Retransmission Request (hARQ)

* Increasing system gain 'by use of denser sub-channelization, thereby improving indoor penetration

* Introducing high-performance coding techniques such as Turbo Coding and low density Parity Check (LDPC), enhancing security and NLOS performance

* Introducing downlink sub-channelization, allowing administrators to trade coverage for capacity or vice versa 

* Improving coverage by introducing Adaptive Antenna Systems (AAS) and Multiple Input Multiple Output (MIMO) technology

* Eliminating channel bandwidth dependencies on sub-carrier spacing, allowing for equal performance under any RF channel spacing (1.25-14 MHz)

* Enhanced Fast Fourier Transform (FFT) algorithm can tolerate larger delay spreads, increasing resistance to multipath interference

SOFDMA and OFDMA256 are not compatible so most equipment will have to be replaced. However, some manufacturers are attempting to provide a migration path for older equipment to OFDMA256 compatibility which would case the transition for those networks which have already made the SOFDMA investment.