Jesse Caulfield

Summary of a field test report about co-channel interference in C-Band. It would be interesting to see this method of analysis applied to TV Band white spaces.

Background:
Several national administrations around the world have designated portions of the frequency band 3.4 – 4.2 GHz for use by terrestrial wireless applications such as WiMAX and future mobile services. Commonly referred to as C-band, these frequencies are already used by satellite services, radar systems and microwave links.

The sensitivity of C-band satellite receiving systems makes them particularly sensitive to disruptions by mobile terrestrial frequencies in immediately adjacent bands.

The Test:
Early in 2007, the Global VSAT Forum (GVF) coordinated an effort to confirm whether WiMAX systems would cause interference to satellite systems operating in an adjacent frequency band.

A side-by-side occurred in November 2007, the results of which showed that WiMAX transmission could cause significant problems to a digital satellite receiver in excess of 12 km away. Calculations based on measured data implied a required separation distance of 278 km.

Results and Recommendations:
FSS antennas cannot co-exist with WiMAX systems using the same frequencies within a radius from between 50 and 200 km, dependent upon the local terrain and WiMAX power output levels.

Comments:
The test setup is designed to illustrate worst case interference. However, in the real world satellite up and downlink signals are polarized, plus Industry and the IEEE are working on 802.11 y (radio beacon) & k (signal measurement) to help WiMAX radios and networks detect and avoid licensed incumbent services.

It would be interesting to also see adjacent frequency and co-channel opposite-polarization interference analysis.

References:

• SIURG Field Test Report

Just found this great video explaining [one side] of the white space concept.

The video is a great synopsis for non-technicl folks just learning about the opportunity. It’s worth 3 minutes sitting through:

It seems the production group is concerned about New York being nervous about microphone interference and looking to preemtively limit unlicensed TV Band in the city.

Resources:

• People’s Production House
• White Spaces

In summary: The Gov’t mucked up the transition (6 years in the making) and now wants to extend the deadline so consumer screens won’t go dark on Feb 17. Problem is they sold channel 55 at auction in 2002 and the broadcast industry has been gearing up for years.

One telling issue to watch is QUALCOMM. They bid $38 million for five Economic Area Grouping (EAG) D block 700 Mhz licenses, giving them six megahertz covering the entire country except areas on the Pacific to launch MediaFLO service on Feb 18.

“Telcos might not be so keen to accept one of Obama’s broadband grants or loans, bid in auction or even support a new initiative if they know the terms could change instantly and arbitrarily.”

This is worth watching – will the Obama Administration keep the Government’s promises or start shredding inconvenient contracts.

References:

• http://telephonyonline.com/wireless/news/qualcomm-dtv-transition-0120/
• http://telephonyonline.com/residential_services/commentary/obama_broadband_challenge_0120/?cid=hcom
• http://www.dailywireless.org/2005/02/25/the-700-mhz-club/
• http://en.wikipedia.org/wiki/MediaFLO

FCC Chairman Kevin J. Martin Announces Resignation
Effective Jan. 20

Innovative use of Unlicensed Spectrum — The 2008 initiative to use television “white spaces” spectrum handed consumers a significant victory. Chairman Martin championed this initiative to free up spectrum, improve wireless broadband and inspire new Internet-based products and services.

International TV White Space Promotion — Chairman Martin created the International TV White Spaces Fellowship and Training Initiative for the FCC to work with international regulators and spectrum experts on TV white spaces technical issues. Its goal is to promote white spaces potential and development of a international devices ecosystem. The FCC Office of Engineering and Technology and International Bureau will administer the fellowship program.

“Martin has long argued that using white spaces can advance the rollout of broadband. The announcement comes the day after President-elect Barack Obama made ubiquitous broadband access a cornerstone of his economic recovery plan.”

Source & References:

• http://www.scvtv.com/npnews/fcc011509.html
• International TV White Spaces Fellowship and Training Initiative
• FCC Taking White Spaces Training Abroad

Monta Monaco Hernon
January 15, 2009

As triple-play has moved from buzzword to reality, today’s hot concept seems to be the wordier notion of consumer access to content whenever and wherever. Some say the FCC’s decision to allow the unlicensed use of TV white spaces will facilitate this.

“The increased connectivity of this quality of spectrum allows more people to watch TV in more places. You will be able to watch high-definition (HD) broadcast television on your Blackberry …. White space is going to be the vessel through which so much of this content is pushed,” said Jake Ward, spokesperson for the Wireless Innovation Alliance, a consortium that supports the use of TV white spaces.

The spectrum at issue exists between broadcast TV channels, specifically below 900 MHz and in the 3 GHz band. The FCC’s ruling in November opened the way for unlicensed wireless devices to operate in this unused spectrum. According to FCC Chairman Kevin Martin, the way has been paved for “Wi-Fi on steroids.”

“I fully expect that everything from enhanced home broadband networks, to intelligent peer-to-peer devices, and even small communications networks will come into being in TV white spaces,” he wrote in a statement shortly after the ruling.
Opposition and safeguards

The National Cable and Telecommunications Association is among the parties that expressed concerns prior to the ruling. The NCTA said that devices with high output power could interfere with cable viewing. The association called for, among other things, restricting portable devices to a maximum of 10 mW and the prohibition of transmission in the VHF channels.

The FCC did build a number of safeguards into its rules, including the use of spectrum-sensing technology and geolocation capability and access to a database of “incumbent services” such as the locations of cable system headends. All white space devices must be certified by the FCC Laboratory and approved by the full Commission.

The first white space devices could appear within a year, with the first application being something simple, like a remote control networking system, Ward said, calling the issue of interference a “red herring.”

“Were there issues (during FCC’s proof of concept testing) with geolocating and proximity interference and volume?” he said. “Sure, but these are prototype devices …. It’s not like the large boxes of wires are going to be on the shelves at Radio Shack any time soon. They have to go out and be developed by R&D, by tech companies and come back to be certified as harmless by the FCC.”

- Monta Monaco Hernon

Reference:

• http://www.cable360.net/print/ct/news/ctreports/33686.html