WiMAX FAQ's

What is WiMAX?

WiMAX is a coined term or acronym meaning worldwide interoperability for microwave access (WiMAX). What WiMAX is however at its heart is a standards initiative. Its purpose is to ensure that the broadband wireless radios manufactured for customer use interoperate from vendor to vendor. The primary advantages of the WiMAX standard are to enable the adoption of advanced radio features in a uniform fashion and reduce costs for all of the radios made by companies, who are part of the WiMAX Forum™--- a standards body formed to ensure interoperability via testing.

Where did the idea of WiMAX come from?

Much of the credit for the formation of the WiMAX Forum™ and the notion of the WiMAX initiative must go to the founding members of the Forum, which committed themselves early to the process of creating a collaborative standards body. Once Intel came aboard, it recognized that for the broadband wireless industry (both fixed and mobile broadband wireless) to gain traction and wide acceptance both hardware prices must decline and a consistent operating environment must be cemented into place. The key point of launch however, had to begin with the silicon chip manufacturers whose chip products would form the core of WiMAX technology value and capability. Intel deserves a great deal of credit for helping drive this process.

Why is WiMAX important for fixed broadband wireless?

WiMAX is arguably even more important for the fixed broadband wireless segment than mobile broadband, at least internally to that industry. It seems clear that mobile broadband wireless holds the loftier long term monetary and customer growth potential. However, the fixed wireless segment has been fragmented essentially since its inception. There are no cohesive standards for outdoor metropolitan area networks beyond the adapted Wi-Fi technologies. Wi-Fi as a standard has been accepted in broad strokes by the industry and the public. However, it is not a well conceived citywide technology. This industry has languished due to the inability to foment a cohesive technology strategy. Innovative features were restricted to individual brands with the result that numerous innovations if combined would have greatly improved results for all.

Why is WiMAX important for mobile broadband wireless?

Mobile broadband wireless or 3G has enjoyed two largely consistent standards, those being the code division multiple access (CDMA) based approach with its evolution data only (EVDO) and the universal mobile telecommunications system (UMTS) and its faster upgrade high speed downlink packet access (HSDPA), which in particular has gained some deployments in the past year. However, these technologies have been slow to mature into economically viable and affordable iterations. The EVDO schema is now in a Revision A version which improves bandwidth considerably. Sprint is the first US based carrier to begin wide deployment. It currently has 10 markets deployed with plans for 21 by the end of 2006. The bandwidth limitations have been significant and the adoption by carriers, particularly those utilizing GSM technology here in the US has been very slow (as they are essentially incompatible technologies).

Newer broadband UMTS (universal mobile telecommunications system) systems that are GSM compatible have seen some traction with AT&T recently in the US, with the bulk of gains happening overseas, particularly in Europe. The sheer cost factor of the technology relative to its native spectral efficiency has not been conducive to adoption either. Estimates for the nation’s cellular carriers to build a comprehensive 3G network have ranged as high as $50 Billion.

Mobile WiMAX offers a multi-spectrum standard with a better broadband technology concept that can significantly reduce costs, improve spectral efficiency and deliver profitable services. The growth curve of the technology, partly due to the large number of chip and radio vendor firms driving the technology, should provide a much higher innovation curve for WiMAX. Internationally, broadband mobile wireless does enjoy greater acceptance. Many companies are inherently more comfortable using a 3G upgrade from the GSM side due to the similarities of the technology.

Will WiMAX replace DSL and Cable?

It is important to remember that WiMAX is a global broadband wireless standard. The question of whether or not it could replace either DSL or Cable will vary from region to region. Many developing countries simply do not have the infrastructure to support either cable or DSL broadband technologies. In fact, many such countries are already widely using proprietary broadband wireless technologies. Even in such regions however, it is very unlikely that either Cable or DSL technologies would disappear. The business case and basic infrastructure often dictates that the cheapest solutions will predominate. In many areas in developing nations, it may be cheaper to deploy Cable and DSL in the cities, whereas WiMAX will dominate outside of major towns.

In the US, both Cable and DSL are growing extremely fast, but are not available for all customers. Rural and remote areas often lack broadband choices if any are available at all. When they are available, the DSL or cable plant may only exist within the town limits with no service outside the city limits. This offers a compelling argument that low-cost WiMAX gear can leverage access to many new customers. WiMAX also promises a whole new level of data access flexibility that will be much less location specific for customers. This type of robust mobile, portable or fixed broadband access will be unprecedented.

In addition, WiMAX will provide competitive options for carriers and users that will benefit traditional wireline carriers and customers by encouraging innovation and improved services.

With the advent of IPTV fiber plays are enjoying resurgence. It does not appear that WiMAX or broadband wireless will be ready to deliver IPTV in the immediate future. However, fixed WiMAX may offer the best potential for delivery of this potential content juggernaut. More recently some promising new compression technologies have been announced. These technologies, while still in development, could potentially allow the delivery of true IP-based TV signals, even to cellular type handhelds. One company asserts that it could deliver high definition TV (HDTV) in as little as 2.5 Mbps of bandwidth, with standard resolution signal requiring 1.5 Mbps. These speeds are within the potential reach of WiMAX.

What is the Range of WiMAX?

The answer to this question probably generates more confusion than any other single aspect of WiMAX. It is common to see statements in the media describing WiMAX multipoint coverage extending 30 miles. In a strict technical sense (in some spectrum ranges) this is correct, with even greater ranges being possible in point to point links. In practice (and especially in the license-free bands) this is wildly overstated especially where non line of sight (NLOS) reception is concerned.

Due to a variety of factors explained in more detail in other FAQ answers, the average cell ranges for most WiMAX networks will likely boast 4-5 mile range (in NLOS capable frequencies) even through tree cover and building walls. Service ranges up to 10 miles (16 Kilometers) are very likely in line of sight (LOS) applications (once again depending upon frequency). Ranges beyond 10 miles are certainly possible, but for scalability purposes may not be desirable for heavily loaded networks. In most cases, additional cells are indicated to sustain high quality of service (QOS) capability. For the carrier class approach, especially in regards to mobility, cells larger than this seem unlikely in the near future.

What is the actual throughput (data transfer rate) of WiMAX Technology?

WiMAX supports very robust data throughput. The technology at theoretical maximums could support approximately 75 Mbps per channel (in a 20 MHz channel using 64QAM ¾ code rate). Real world performance will be considerably lower---perhaps maxing out around 45 Mbps/channel in some fixed broadband applications. Remember however, that service across this channel would be shared by multiple customers. Actual transmission capabilities on a per customer basis could vary widely depending on the carrier’s chosen customer base, which is actually an inherent strength because it can be defined by QOS in a deliberate fashion to offer different bandwidth capabilities to customers with different needs (and different budgets). Mobile WiMAX capabilities on a per customer basis will be lower in practical terms, but much better than competing 3G technologies. WiMAX is often cited to possess a spectral efficiency of 5 bps/Hz, which is very good in comparison to other broadband wireless technologies, especially 3G.

In practical terms, Sprint has stated that it intends to deliver service at 2 Mbps to 4 Mbps to its customers with Mobile WiMAX.

The modulation scheme, whether quaternary phase shift keying (QPSK), quadrature amplitude modulation (16QAM, 64 QAM etc.) and their attendant code rate variations deliver varying bandwidth capabilities by channel size. Like most things wireless, the devil as they say is in the details. The good news is that pretty much all of the news is good in this regard relative to other broadband wireless and wireline competitors of WiMAX. The OFDMA® technology actually supports multiple modulation schemes depending upon the users range from the cell with users at closer range receiving signal across more sub-channels at, for example, 64 QAM whereas a user at greater range would receive signal across fewer sub-channels (with higher gain or power per channel) using a lower bandwidth QPSK technique for example.

Many things affect transfer rate beyond simple radio capability---one major element being distance from the base station. The physics of radio cannot be avoided. Longer ranges result in lower bandwidth delivered. Also, the spectrum channel size (1.e. 20 MHz or other) that regulation defines as appropriate for different frequency bands will dictate bandwidth capabilities at least to some extent. Also, remember that the RF and physical environment play a strong role in throughput results. Essentially, the real world blunts theoretical performance.

The physics of frequency range plays a powerful role in bandwidth capability. The higher the frequency, the greater the bandwidth delivery potential and the shorter range potential. Lower frequencies enjoy much greater range capability, but trade that off with much lower bandwidth potential. Fortunately, even with disclaimers centered on real world impediments, WiMAX throughput is excellent.

WiMAX equipment benefits to service providers

The benefit of a consistent technological standard alone to the service provider community is significant. The collection of numerous best of breed technology innovations into one consistent package will improve service. The WiMAX spectrum efficiency gains are very solid, which will leverage the ability to provide service to denser customer bases for lower costs. A more consistent technological approach is a key ingredient to identifying best practices for delivering broadband wireless access consistently across multiple geographic and radio frequency (RF) environments.

The cost savings from silicon chip based support of WiMAX technology offers profound implications. The WiMAX forum states that it expects the first wave of customer premise equipment (CPE) to be available to carriers in the $350 US price range. Second generation gear which will offer improved self-installation capabilities (per the Forum) should sell in the $250 US cost range. Whereas the third generation of WiMAX gear usable for laptops and other portables could sell in the $100 range.

Industry pundits widely believe that sub $100 CPE is essential for the broad acceptance of BWA technology. More recent conversations offer hope for integrated chips that could drop below $50 each when volume manufacturing comes online. Lastly, the opportunity to shop vendors for enhanced feature sets while being able to consistently count upon a base set of radio capabilities can only help the service provider industry in creating market differentiation from wireline products---hopefully heralding a new era of enormously flexible, mobile and powerful broadband services