UWB Bluetooth test standards still undefined

Now that the Bluetooth SIG has picked MB-OFDM as its technology-of-choice, the organization is off doing one of the things that it does best -- getting approval of a common frequency band so that Bluetooth devices can be used worldwide.

However, there is a twist in the process this time: Getting country regulators like the US 's FCC, Europe's CEPT and Japan 's MPT to think differently when considering UWB.

For the last 70 years, the mindset of regulators when reviewing new technologies is to identify a frequency band -- a box -- that the proposed application can operate in and then ensure that the application operates only in their box and not spill over into the box next to them, thus disrupting their neighbor.

However, for UWB to operate successfully, its basic underlying technology requires -- as the name implies -- an ultra-wide bandwidth for it to work. Wider the bandwidth, then lower the power (per unit of frequency) that is required to successfully use UWB. 'Ultra wide' implying bandwidths on the order of gigahertz, as opposed, for example, to wideband CDMA's requirement of a 5-MHz frequency band. The Bluetooth SIG is now promoting a 1.7-GHz bandwidth above 6-GHz for UWB Bluetooth.

Theoretically, the power levels needed for UWB operation would be in the noise floors of adjacent applications. And that is the 'twist' in the process this time: getting regulatory agencies to first accept a technology that inherently is going to spill out of its box, and, when it does, at what acceptable power levels.

The US 's FCC was one of the first agencies to tackle the issue, beginning its studies in 1998. One of its chief concerns and the concern of others was that UWB applications not interfer with global positioning system (GPS) receivers. By 2002, the FCC gave UWB the go-ahead to operate using Part 15 limits as the baseline for its operation. (Part 15 permits the operation of authorized low power RF devices without a license from the Commission or the need for frequency coordination under general emissions limits.)

One of the interesting things about UWB regulations is that they differ from traditional regulations in three significant ways:

"§ emission is intentional

"§ the level of emission is measured as 'per MHz'

"§ field strength is not limited to frequencies above 960 MHz.

This will alter testing strategies and the specifications on testing equipment required.

The first Report and Order from the FCC has since been followed up with a second in 2004 and the granting of a waiver request in March 2005 to allow OFDM devices to be tested with hopping activated and to allow the practical development of MB-OFDM devices. This was an important waiver redefining the method of testing UWB products.

The WiMedia Alliance expects that Europe, Korea and Japan will soon authorize the use of UWB technology as well -- perhaps in the third quarter this year, with Australia , New Zealand , Canada , Singapore and Hong Kong to quickly follow.

Currently, the issues of permissible bandwidths and acceptable power levels are being addressed.

For applications like UWB Bluetooth and wireless USB, the FCC has allocated a frequency band from 3.1 GHz to 10.6 GHz with a maximum power level of -41.3 dBm/MHz EIRP.

 

ETSI (Europe), ofcom ( UK ), MIC ( Japan ) have approved or proposed a -41.3 dBm/MHz limit as well for the 3.1- to 10.6-GHz band. Singapore 's iDA initially set a higher power limit for its country's UWB development work, and has stated that its regulatory framework will be based on ITU's recommendations. (Last February ITU's Study Group 1 approved a series of draft recommendations that gives UWB radio the status of a Global Regulatory Standard.) Korea 's ETRI's standard is a much lower -66.58 dBm/MHz.

However, at the EU level a problem appeared on March 24 with the issuing by the ECC of its ECC/DEC/(06)04 decision. ECC/DEC/(06)04 was developed in response to an EC mandate to identify the conditions relating to the harmonized introduction in the EU radio applications based on UWB technology. That's the good news. The bad news is that buried in Annex 1 is a power specification that would reduce the operating capabilities of UWB Bluetooth devices by about 20% to 30%.

In the 6- to 8.5-GHz band, UWB devices can output a maximum power level of -41.3 dBm/MHz; however, in the 8.5- to 10.6-GHz band, the ECC decision reduces the maximum output to -65 dBm/MHz.

As noted earlier, the UWB Bluetooth community is standardizing on a 1.7-GHz bandwidth, operating above 6 GHz. This is where they think that they will have their best chances of getting common agreement from regulatory agencies around the world. Currently, the common worldwide spectrum is 7.25 GHz to 8.5 GHz. The 1.25-GHz bandwidth isn't quite wide enough to ensure that UWB Bluetooth products would meet users' expectations. Therefore, Bluetooth needs the ECC to restore the maximum output in at least the 8.5- to 9.0-GHz band to -41.3 dBm/MHz. That would give UWB Bluetooth the desired 1.7-GHz bandwidth.

On May 19 the Bluetooth SIG sent a letter to the ECC asking for the opportunity to discuss reasoning behind the 8.5- to 9.0-GHz band prohibition. And until this impasse is resolved, UWB Bluetooth test development is left in a state of flux.

 

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