Will WiMAX take off?

April 19, 2009 by
Filed under: Technology 

Sprint is touting its recently launched 4G service. It is a result of a joint venture with Clearwire. The underlying technology is called WiMAX (Worldwide Interoperability for Microwave Access).  WiMAX is a standards-based technology enabling the delivery of last mile wireless broadband access with performance expectations similar to those of wired broadband like cable or DSL. WiMAX provides fixed, nomadic, portable, and mobile wireless broadband connectivity without the need for direct line-of-sight with a base station. In a typical cell radius deployment of three to ten kilometers, some WiMAX Forum Certified™ systems can be expected to deliver capacity of up to 40 Mbps per channel, for fixed and portable access applications.

Mobile network deployments are expected to provide up to 15 Mbps of capacity within a typical cell radius deployment of up to three kilometers. Its main application is allowing for urban areas and cities to become “metro zones” for portable outdoor broadband wireless access.
WiMAX is classified as a 4G technology in the sense that it is significantly different than 3G wireless technologies like HSPA or EVDO.   Due to these differences, service providers can launch teh technology significantly cheaper than prior versions.   At the same time they drive complexities and high cost for the device manufacturers particularly in its early stages.

The main characteristics in the standard that make WiMAX so compelling are:

1. S-OFDMA (Symmetric Orthogonal Frequency Division Multiple Access). The OFDMA modulation scheme allows for a significant improvement in spectral efficiency over CDMA used in 3G. This translates into higher capacity on the same spectrum allocation for the service provider. Symmetry allows for same upload and download speeds, critical for Web 2.0 applications where the user requires similar bandwith in both directions. The combination of these 2 features allows WiMAX to perform very similar to a traditional broadband connection like DSL, cable, or enterprise T-1’s and at faster speeds.

2. Full IP architecture: Non circuit switched architectures allow for bandwidth on demand applications as well as an easy expansion over time. This drives the right economics for the service providers allowing very high bandwidth reuse factors. Very similar to the wired Internet that grew extremely fast.

3. MIMO (Multiple Input Multiple Output): This technology enables a significant channel efficiency compared to SISO (Single Input Single Output) used in 3G by adding frequency diversity to the communications channel. Fading and multi-path, so common in urban environments and indoors, are frequency dependent. MIMO increases the probability of uncorrupted packets arriving at their destination. From the service provider perspective this translates into more users in the same spectrum due to the reduction in retransmissions and lost packets. From the device perspective battery consumption is being saved.

4. Frequency Agnostic: There are currently WiMAX deployments across the world in 450, 700 MHz; 1.9, 2.1, 2.3-2.7, 3.3-3-5, and 5.8 GHz, both in licensed and unlicensed bands. This allows adaptation to the spectral allocations and flexibility for large or small service providers. This is perhaps the feature that has yet to be rationalized since it presents a lot of complexities and cost for device manufacturers, particularly for international enterprise deployments such as multi-national companies.

5. Support for TDD (Time Division Duplex) and FDD (Frequency Division Duplex) profiles: This part of the standard allows for flexibility to adopt WiMAX in frequency ranges where either scheme is technically preferable or mandated by local regulatory bodies.

6. IABF (Intelligent Adaptive Beam Forming): This feature is particularly critical for urban environments where power is lost through absorption in buildings and other interferers. It also allows devices to operate at lower power by introducing antenna gain in the communication channel which also translates into longer battery life.
Although all of these features are technically compelling there are not WiMAX exclusive. Most notably the other 4G technologies that are being analyzed (LTE or Long Term Evolution and UMB or Ultra Mobile Broadband) are following similar technical recommendations.

It is worth noticing the complexity of this technology from the device perspective. Multi-frequency systems will drive complex RF front ends and antennae whereas TDD/FDD profiles with MIMO and OFDMA drive very complex baseband architectures. Silicon suppliers will require significant R&D investments in order to address these issues efficiently.

There are basically two main standards driven by the IEEE. 802.16d or “fixed” WiMAX, which is designed for fixed, nomadic, and portable applications. This standard competes with fixed wireless proprietary architectures, Metro-WiFi and hot spots. 802.16e or “mobile” WiMAX is geared towards internet-on-the-go-applications.  This is the version that is most relevant for a 4G applications.

The WiMAX standard is the result of two main standards bodies: IEEE-802.16 and the WiMAX Forum. It is similar to WiFi in the sense that the IEEE (802.11)is responsible of setting the standards and a group formed by industry leaders (WFA) is responsible of ensuring interoperability. Today more than 500 companies are members of the WiMAX forum, 170 of whom are service operators. Some of the most notable are Motorola, Intel, Sprint-Nextel®, Clearwire®, Bell Canada®, Vodafone®, Nokia-Siemens®, Alcatel-Lucent®, IBM®, and Cisco® through the aquisition of Navini in 2007.

The September 2007 WiMAX World conference in Chicago, one of 3 held worldwide that year drew an estimated 7000 attendees from some 500 companies and around 100 speakers. In contrast, 3GPP and the OMA (Open Mobile Alliance) responsible for driving the GPRS / UMTS activities has thousands of members and runs 3GSM event twice a year. The European event that same year drew 70000 attendees, 1300 exhibitors and 500 speakers (120 CEOs).

As promising as WiMAX sounds, it has not been selected by major service providers around the world for their 4G deployments. the only exception  has been the CLearwire-Sprint JV.  LTE in contrast has been given significant preference throughout the world and has the potential to overshadow Clearwire’s attempts.  In the US AT&T and Verizon have announced LTE as their 4G technology of choice.  Combined they boast more than 150 million subscribers.  In addition to that it is expected that most European service providers will follow the LTE route as well.  The economies of scale that this will provide for device manufacturers is tremendous.

The only advantage WiMAX has over LTE is the fact that it exists today.  An advantage that has a very, very short shelf life.  Can Sprint/Clearwire launch the service fast enough to gain some subscribers or AT&T and Verizon Wireless beat them to the punch?  A quick glance at their balance sheets will provide a hint.

WiMAX, perhaps one of the most exciting technology developments of the 21st century has the potential to suffer the fate of iDEN:  outstanding technology, potential for a great service, but relegated to a single service provider.

Enjoy.

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