Analysis This week’s IEEE summit highlighted the breakneck pace of change that is driving innovation in wireless, but also threatening to break its standards process apart. Political wars rage in areas like UltraWideBand and fast Wi-Fi, but more fundamental debates are taking place over how different specifications should coexist and which territory they should occupy. As Wi-Fi reaches up to WiMAX’ range and WiMAX aims for the mobility of 802.20, the most important IEEE group of all may be 802.22, looking at the cognitive radio that will enable devices to use all three and to take advantage of proposed opening of US television spectrum.
This week’s IEEE meeting in Portland, Oregon is shaping up to be one of the most lively in years, with a packed agenda that highlights both the current breakneck pace of change in wireless networking, and many of the splits that could slow this pace in the near future.
As well as the obligatory vote on the UltraWideBand-based 802.15.3a standard proposal, in which the two technologies – Motorola’s DS-UWB and Intel/TI’s Multiband OFDM – will fight it out once more, there are new debates raging that may prove just as intractable. Like the UWB schism - which threatens to drive both camps to establish de facto standards, diluting the role of the IEEE in the wireless future – splits over fast Wi-Fi, mobile WiMAX and use of broadcasting spectrum for broadband wireless could all have a highly negative effect on the progress towards a multi-network, standards-based wireless world.
The fight for broadcast spectrum
A more unexpected battle, but one that shows where the ambitions of the WiMAX camp are heading, broke out early in the IEEE summit, over television broadband. Proposals to allow sharing of underused US TV spectrum by wireless devices could open a whole new range of opportunities for WiMAX, and the 802.16 group and its greatest cheerleader Intel are keen to take the driving seat.
These ambitions clashed with IEEE plans to set up a separate body, called 802.22, to look at a standard for the peculiar requirements of broadband wireless in TV spectrum, and specifically at a cognitive radio that would be able to detect when a wireless device might interfere with an incumbent broadcaster’s signal and back off. This group would be a spin-off of the existing 802.18, also called the Radio Regulatory TAG, which exists to provide the 802 wireless working groups with regulatory expertise.
This plan was denounced by the 802.16 committee chairman, Roger Marks, who claimed its work was already covered by the remit of the WiMAX work. "I don't see how this is in anyway different than what we do in 802.16," said 802.16 members. A resolution was passed that would submit comments to the Executive Committee, explaining why the TV-Broadband standards work should be incorporated into the 802.16 standards group and not spun off into a separate working group like 802.22.
The debate may seem obscure, but a look at the factors behind it reveal why it is actually of crucial importance to companies that want WiMAX to become the dominant technology for broadband wireless.
Last month, the Federal Communications Commission (FCC) issued a Notice of Proposed Rulemaking that would allow for unlicensed broadband wireless operations in underused television frequencies, in channels below 900MHz and in the 3GHz band. This proposal has been heavily supported by FCC chair Michael Powell and has been the subject of intensive lobbying by Intel, which sees the additional spectrum as a rich hunting ground for WiMAX, particularly in its mobile form.
The FCC proposes to insist that unlicensed devices in these bands should incorporate cognitive radios to identify unused channels. It will permit two types of broadband access – by low power personal gadgets such as Wi-Fi or WiMAX cards in laptop computers or home networks; and by higher power fixed wireless technology providing commercial broadband services.
As well as relieving the pressure on overcrowded unlicensed spectrum for Wi-Fi and WiMAX operators, the freeing up of these frequencies would also be important because signals in the lower TV band can travel longer distances and penetrate buildings and trees more easily than they can in the current 2.4GHz and 5GHz bands.
Intel’s CTO, Pat Gelsinger, a vocal campaigner for more liberal approaches to spectrum suitable for Wi-Fi and WiMAX, commented:
"For more than half a century, vacant TV channels (which represent some of the most valuable spectrum available) have been underutilized. Releasing this spectrum for unlicensed use will help foster new technologies, create opportunities for business and bring exciting new products to consumers."
The move will be a driver to accelerate work on WiMAX profiles that will allow the technology to work in the 3GHz band and the lower frequencies. Although all the focus of recent 802.16 work has been on bands between 2GHz and 11GHz, the WiMAX Forum said earlier this year that it would also look at profiles for low frequencies, clearly with the potential FCC changes in mind.
WiMAX is flexible in its channel sizes and can use the 6MHz width of the TV channels. Even with these narrower channels, signal range below 900MHz could be three times that in 2.4GHz, reducing the number of base stations required well below 3G’s requirements, and so making mobile WiMAX clouds an even stronger proposition against cellular.