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Post by Barry Thomas McQuire with IT Pros Silicon Valley

Is that the death knell I can hear sounding for WiMAX? Not quite. The wireless technology has taken several body blows recently, but it should survive.

Of these blows, erstwhile WiMAX champion Clearwire's decision to trial LTE technology is probably the most damaging, along with the news that some of the companies that have secured 2.3 GHz spectrum in the potentially enormous Indian market plan to use LTE rather than WiMAX.

WiMAX has been put on the back foot by the momentum building behind LTE TDD, the LTE variant that uses the same unpaired spectrum allocations.


Although mobile WiMAX reached the market earlier than LTE, it has failed to gain a strong foothold and its modest achievements to date have mostly been overshadowed by the rapid growth of HSPA and now HSPA+, as well as EV-DO. By the end of 2010, there will be 8.7 million mobile WiMAX connections worldwide, according to Maravedis, compared with more than 380 million HSPA connections, according to Wireless Intelligence.

So, why hasn't mobile WiMAX gained more traction? On paper, it has considerable promise – it uses many of the same advanced technologies as LTE, including OFDM and MIMO on the radio interface.

But in practice, live WiMAX networks aren't performing any better than HSPA+ networks. Clearwire says its WiMAX service offers average mobile download speeds of 3 Mbps to 6 Mbps, while independent tests have found that T-Mobile USA's HSPA+ network is delivering average download speeds of around 5 Mbps. In Stockholm, TeliaSonera's commercial LTE service delivered an average downlink speed of 33.4 Mbps in recent tests by IDG News Service.

Incompatible and In the Cold

Moreover, unlike HSPA+ and LTE, WiMAX wasn't designed with compatibility and co-existence with mobile operators' existing GSM, CDMA and 3G networks at its core, meaning that a call or data session can't necessarily be handed-over between a conventional mobile network and a WiMAX network, as a subscriber moves in and out of coverage areas.

Given that context, the market for WiMAX has really been limited to so-called green-field operators, as it would have been an expensive U-turn for any operator to move from GSM or 3G into WiMAX, instead of simply upgrading to HSPA.

For similar reasons, a step from CDMA-2000 into WiMAX would effectively be a massive gamble on customers being prepared to put up with potentially dropped calls and data sessions when they moved out of areas of WiMAX coverage.

As WiMAX isn't a viable upgrade option for most existing mobile operators, it has been very difficult for vendors to get the economies of scale necessary to develop a wide selection of mass-market WiMAX devices. While HSPA has an ecosystem made up of several hundred equipment manufacturers offering more than 2,000 HSPA-capable devices, many vendors have turned away from WiMAX and towards LTE, and now some hitherto WiMAX operators are following suit.

Mash-up or Mess-up?

WiMAX's incompatibility with existing mobile networks is just one of the reasons it hasn't reached its apparent potential. In an age when openness and diversity, mash-ups and application development are creating a vast range of end-user services, it is easy to forget that mobile telecoms is a huge global success because of tight adherence to standardized technologies.

By contrast, early WiMAX networks have been deployed using a variety of implementations which have not always been compatible with one another and have held varying degrees of compliance with the 802.16 specifications.

All of these implementations have been swept up under the WiMAX banner, but having a single name for a disparate collection of technical implementations does not replicate a standards-based ecosystem.

This fragmentation creates an R&D headache for device manufacturers as they often need to adapt equipment for specific operators and specific networks. In trying to get ahead of LTE by arriving early and exploiting the resultant time-to-market advantage, WiMAX has shot itself in the foot.

Now, WiMAX finds itself in a precarious position. The vast majority of the major mobile operators in the world have made public statements of intent to move to LTE and they are making sure that this technology is deployed in a consistent way that will enable the ecosystem to achieve economies of scale. The years of experience that these operators have with deployments of 2G and 3G technologies mean that the LTE pioneers are unlikely to make the same mistakes as their WiMAX counterparts.

The breadth and depth of LTE's global support is very ominous for WiMAX, but I do see the 802.16 technology having a future, primarily in scenarios where mobility and interoperability are a secondary consideration. These could include acting as an alternative to fixed lines in areas that are difficult and expensive to reach with ADSL and as a backup service in case a fixed line fails. WiMAX is also sometimes used to provide backhaul links for mobile base stations and it should continue to have a role in that market.

So, WiMAX will live on, but not as a significant rival to HSPA or LTE...............

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Recently, I spoke about Wi-Fi won the battle on being the technology of choice for basic networking in laptops and later mobile devices too.

The fight was taken to the next level in WAN technologies.

With the deployment of 4G technologies imminent, the field became very interesting.

To put simply, to create 4G technologies, we needed to have the data rates that were prevalent in WiFi (20-30 Mbps) but also have the mobility, that were the forte of existing cell phone technologies. One player’s strength was others’ weakness.

It was the question of if data communications based WiMAX (802.16e) would gain mobile capabilities and keep up its intrinsic strength of fast data rates, or if cellular technologies (like CDMA, WCDMA, etc) would get fast data rate capabilities retaining their mobility. Sounds like a thriller, isn’t it?

To be honest, mobile wireless broadband was created by technologies powered by WiMAX (IEEE 802.16e) which was launched in late 2005 in S. Korea (in a flavor called WiBro) – With this, close to 25 Mbps was initially available at the network, permitting video conferencing, HD video streaming etc.

However, there were initial hiccups during handovers (when a mobile moves from one cell to another, the signaling is transferred from one cell to another) – Typical handovers initially were in tune of 120 – 150 milliseconds. (Not bad for data traffic, but bad for voice)

Despite being first in market, WiMAX did not do great, and will be relegated to background, for the reason similar to why WiFi won – Compatibility.

Considering 4G technologies, the two options were WiMAX and another was LTE (Long Term Evolution – Sorry if you expected something fancy  ) – While LTE was delayed, it was an upgrade to existing networks, while WiMAX was a brand-new technology. The operators who had spent a lot of money in 3G, were apprehensive of sinking a lot of money in a brand new technology, while LTE was only a couple of years away, then.

WiMAX was a great technology – It offered mind-boggling speeds in a mobile environment, brought lot of technologies that were considered only lab-worthy out to real life. WiMAX brought very exciting technologies to mainstream:

1. MIMO (Multiple Input, Multiple Output)– You might see a lot of ads saying – ‘Powered by MIMO’. These systems have transmitters and receivers with more than one antenna. I assure you that this is way more complex than sticking another antenna to your mobile 
2. Space-Time Frequency Coding (I’ll do well to skip explaining what is this, but to put it simply, it is a way of encoding data at the transmitter and decoding it at the receiver to boost overall data rates. If my mailbox gets flooded with requests on explaining this, I’ll certainly do it  )
3. Downlink Channel Reporting – In Communication systems, only a receiver can measure the nature of the wireless channel in which data is transmitted. This is measured and sent back to the network for tuning the amount of data or data rates sent from network to the receiver. To simply put, if the mobile is in a very noisy area, send data at lower data rates, else send it at much higher data rates
4. Beam Forming – This is definitely Star-Trek stuff. It is normal for some of us to go around the office or the road, asking ‘Is it clear now?’ while talking on the phone. While you can certainly do it, your house cannot move around.
   
   So, if you are one of the lucky people in the cell edge where the signal is permanently low, you’ll be blessed with a constant low signal and hence low data rates (See #3), though your provider will not reduce your subscription rates. To provide good signal to these areas, technologies like beam forming are used. In this an array of antennas produce signals (waves) that constructively interfere to spacially provide excellent signal strength to the subscriber in bad coverage area.

While WiMAX proved these and many more, LTE smartly learnt from these experiences and incorporated a good part of these, removed some, and is ready for prime.

WiMAX, is an example of technology that despite doing a lot of things right, failed, despite being the first in the market. It is a classic example of why things can fail despite a working solution, and being first in market.

But, I can certainly say one thing for sure – I loved working in both WiFi and WiMAX, and certainly enjoy contributing to the LTE ecosystem.....