TV-Band White Spaces Database Providers list officially released

One year after the proposals by TV-Band white-spaces database providers the FCC released recently the next steps in this matter. As it was expected the FCC opted for license the spectrum database to multiple providers:

"While the operation of multiple database administrators may present some coordination challenges, we find it is in the public interest to have multiple parties developing business models for this new mechanism."

It results that all the proposals from last year have been "conditionally" selected:

• Google
• CommSearch
• FrequencyFinder
• KB Enterprieses/LS Telcom
• Key Bridge
• NeuStar
• Spectrum Bridge
• Telcordia
• WSdB

The details of the database architecture are not complete. To this end, database providers have to complete their proposals to address the new rules and attend the following OET Workshops. As I commented before, the providers were conditionally selected. From the announcement:

"we are designating the database administrators subject to a number of conditions, including that they attend workshops to be conducted by OET and perform real-world testing of their databases to ensure they provide accurate results before they are made available for use by TV bands devices"

ECC Report 159: European white space devices

While in the US the FCC pushed the "final" rules for unlicensed access of the television band in Europe the ECC approved a similar report, although in a preliminary phase. This report, published as ECC Report 159, can be downloaded from the CEPT meeting documentation area (by selecting group 43, year 2010, folder SE43#7-1009-Biel>>Minutes and document number SE43(10)126-Annex 3). In this report the working group SE43 studies both the protection requirements of the licensed users of the 470-790MHz band (and its neighboring bands) and the operational characteristics of the unlicensed devices, in the document referred as white space devices.

The document studies three candidate techniques to be implemented by the cognitive radio devices, namely sensing, geo-location database and beacon. However in a similar line to the FCC conclusion the report indicates that the current technology is not adequate for sensing based standalone systems:

"The sensing thresholds were derived for a limited number of scenarios using the methodology developed within this report and taking into account a range of potential DTT receiver configuration. Some of the values so obtained (being in the range from -91 to -165 dBm depending on the DTT planning scenario) appear to be too low to be implemented using the current technology. Moreover, in some scenarios, even these low values for the detection threshold do no guarantee a reliable detection of the presence/absence of the broadcasting signals at the distance corresponding to the interference potential of a WSD."

While the ECC Report 159 also studies the combination of sensing and geolocation database to assure the required protection to primary users, the ECC will probably conclude that geolocation based devices offer enough protection without additional sensing. This may look as bad news for the companies which invested in spectral sensing research. However, as Roberto points out in a comment of the last post spectrum sensing devices may be useful to build and keep up to date the information present in the database.

FCC "final" rules. Cognitive radio or just unlicensed access?

In the previous post I presented the situation in both the US and Europe regarding the use of unlicensed white space devices in the television band. As it was expected, the FCC released the "final" rules for the cognitive use of TV white spaces in the US (press release, report FCC-10-174).

This solution is based on a database architecture only. That is, the white space devices must have geolocation capabilities and download from a database the occupancy tables while they are not required to perform additional sensing before transmitting. Moreover, as opposed to 2008 rules, the low power devices which could relay only on sensing are banned:

"Eliminating the requirement that TV bands devices that incorporate geo-location and database access must also listen (sense) to detect the signals of TV stations and low power auxiliary service stations (wireless microphones). As part of that change we are also revising and amending the rules in several aspects to reflect use of that method as the only means for determining channel availability. While we are eliminating the sensing requirement for TVBDs, we are encouraging continued development of this capability because we believe it holds promise to further improvements in spectrum efficiency in the TV spectrum in the future and will be a vital tool for providing opportunistic access to other spectrum bands."

Note that the final rules encourage further research in cognitive radio sensing techniques, since this may be useful for other spectrum bands. However the final rules discard the idea of cognitive radios: is it cognitive to download from a database a list of free channels?

On the other hand, wireless microphones, low-power dumb devices that cannot be guaranteed to be registered in the database, will have two channels for exclusive use. Extra channels can be temporarily reserved in the database during special events for the use of these devices.

To finish with, note that the central part of the architecture is still missing. While the FCC already received different proposals for the database architecture, interface and specifications of the database need to be defined yet.

All these issues motivate the use of quotation marks when I write FCC "final" rules.

Final FCC rules for the unlicensed use of the TV white spaces today?

The FCC is expected to release today the final rules for the use of TV white space spectrum in the US. The previous version of these rules, published almost two years ago, generated several protests by (both aerial and cable TV) broadcasters and raised additional technical issues seeking reconsideration of the 2008 rules. However during these two years the FCC authorized several tests and trials in order to evaluate the benefits and possible problems the unlicensed access to the TV band. The FCC also received database proposals from different companies to enable the use of geolocation based devices, and allowed the time for the digital transition process to complete.

While this happens in the US, Europe is still a step behind. Recently the CEPT SE43 workgroup, which is developing recommendations for the unlicensed use of 470-790 MHz in Europe, participated in the 57th WG SE meeting. A final version of the Draft rules for European White Space Devices (draft ECC Report 159) has been approved for public consultation (see pages 17-18 of this document). After a two weeks pre-consultation period within administration, the public consultation will start on the 30th of September. However, from the documents currently available, additional studies will be probably required before the definitive report is published.

In the (hopefully) near future I will go over the FCC decision and the ECC Report.

Edit: Here my comments on the FCC decision.

Testing and certification of Cognitive Radio equipment

After reading a recent discussion on the Linked-in Cognitive Radio group I researched on the testing procedure of Cognitive Radio equipment. It is not straightforward to define a testing procedure so that reconfigurable systems are guaranteed to comply with regulations under all circumstances: the behavior of a node may depend on the current conditions and past history of the environment.

Right now there is no standard procedure that allows vendors to test their cognitive radio prototypes. In this sense the Wireless Innovation Forum's Test and Measurement Work Group is currently preparing a report called "Test Guidelines and Requirements for Television Band Devices (TVBDs) Designed to Operate on Available Channels in the Broadcast Television Frequency Bands":

The report will identify unique test challenges created by SDR/CR radio system technology used for TVBDs and will provide a basis for test and certification."

These challenges include dynamic waveform activation, opportunistic scheduling, policy based operation, spectrum sensing and interference avoidance. While this report will be an useful tool, its final version is scheduled in October 2010.

Other tests have been performed so far they have been oriented to measure only a subset of parameters of the system or to show the proof-of-concept of the unlicensed access paradigms. For example, the FCC testing of TV white space devices developed a procedure for the evaluation of equipment of different vendors, however it was oriented to the elaboration of the rule-set for unlicensed use of the tv-band. The test plan divides the procedure in three well differentiated parts:

1. Laboratory bench tests of sensing capabilities (single laboratory-grade DTV, single RF-capture DTV Input Signal, multiple DTV Signals and wireless microphone signals).
2. Laboratory bench tests of generated interference (transmitter emissions characterization and interference to wireless microphones).
3. Field Tests (both for sensing performance and generated interference).

The results of this testing plan conducted to the geolocated database based approach finally approved by the FCC.

The DARPA XG report "A Description of the August 2006 XG
Demonstrations at Fort A.P. Hill" presents a detailed description of the tests carried out in an outdoor six node network of Next Generation (XG) radios capable of using spectrum over a wide range of frequencies on a secondary basis. The conclusions read as follows:

A six-node XG network and three two-node XG networks were tested using four test scenarios: two were without XG adaptation and two were after adaptation. The audience, members of the U.S. government's military and spectrum management officials, was able to see clearly how XG could adapt to the local interference landscape and share frequencies rapidly and with little to no interference with existing legacy military radio systems. This demonstration showed that DARPA concepts of frequency sharing in a mobile environment are possible with today's technology."

On the other hand, Europe is also defining the requirements for the unlicensed access to TV-band and considering the possible regulatory issues in the SE43 Regulatory Affairs Working Group:


While this study is not mature enough to offer a practical testing and certification protocol, Ofcom (communications regulator in the UK) presented in February 2009 a consultation regarding the exploitation of cognitive radio in digital dividend bands:

Determining the sensitivity of a device is relatively straightforward. It is often quoted in device specifications and can readily be confirmed in laboratory trials. For example, a number of DTT receivers could be procured, a test signal inserted into their aerial socket and the strength of this signal reduced until the picture quality visibly deteriorates."

However, the report also stress the fact that the sensing performance has to be achieved in real world scenarios:

In particular, the devices must be able to sense in the presence of strong signals in adjacent channels (or they must choose not to use channels where strong signals are present in adjacent channels). They must also be able to sense adequately in the presence of other cognitive devices using nearby channels. Hence, we suggest that, as part of the specification and resulting type-approval verification, cognitive devices be tested to ensure that they do not incorrectly declare a channel to be unused regardless of the level of signal in adjacent channels."

Other points commented in the document are Bandwidth, Signal characteristics, Time between checking for channel usage, Out-of-band performance, Politeness...

As a conclusion, while there exists no integral test plan for Cognitive Radio devices, the evaluation of some of their capabilities can be carried out following a test methodology similar to the ones presented. For example, sensing and interference can be determined for single nodes using a procedure similar to the FCC test plan. Other more sophisticated network features require more complex tests that measure the aggregated interference and the dynamic capabilities of the network, such as the DARPA XG evaluation or some of the points considered in Ofcom's report.

Unlicensed access to television broadcasting spectrum in Europe

The previous post about the unlicensed access to TV-band in the US was finished with the question What can Europe learn from this?. I will try here to answer this question by summarizing the current state of the European regulations for unlicensed access to the white spaces in the television band.

The Open Spectrum Alliance is a coalition of companies, organizations and individuals founded in May 2009 in order to push the unlicensed access to the spectral resources. They actively collaborate with the CEPT's Electronic Communications Committee working group designated to study the technical and operational requirements for the operation of cognitive radio systems.

The SE43 working group is currently preparing a document defining the requirements for the operation of cognitive radio systems in the white spaces of the band 470-790 MHz. This draft describes the protection requirements of terrestrial broadcasting (detection thresholds, hidden node margins...) together with the architecture to achieve it (spectral sensing, geolocation database, combination of sensing and geolocation...).

That is, they are working in a document equivalent to the rules approved by the FCC in November 2008 for the regulation of devices using white spaces of the TV band in the USA. While the FCC had been examining this issue for six years prior to the elaboration of the document, the European version could be expected to be ready at the end of the year. That is, the document would be developed in three years in part by using the experience obtained from the american pioneering work.

In order that the european ruleset comes into play further steps are needed due to the more complex hierarchy in the EU. Therefore we could say that the european regulatory process presents a delay of 3 years with respect to the USA's framework for cognitive radio, which already defined proposals for the geolocation databases and cognitive radio data networks tests.

White space data network trial in Wilmington

Two experimental TV band white space licenses are included in the FCC list of experimental actions from 1/1/10 to 2/1/10. One of them is TV Band Service LLC that received a license for use of 168-216 MHz and 470-608 MHz spectral bands "to conduct research by using vacant spectrum in the television broadcast band, for the testing of fixed Whitespace devices" in the Wilmington area, DL. This company seems to be working with Spectrum Bridge to set up this network. Rick Rotondo, chief marketing officer and co-founder of Spectrum Bridge declared:

There's a ton of white space in Wilmington"

More information on ABC News and other sources.

The second license is for Spectrum Bridge itself (also interested in becoming a white spaces database provider) and covers the same frequency range in the area of Lake Mary (Seminole), FL.

A third experimental license somehow related to cognitive radio was granted to Matthew T. Kaufman, to use part of the 700 MHz band to "perform a non-line-of-sight digital network experimentation" with fixed and mobile devices in Los Gatos and Bonny Doon, CA. Kaufman stated that the main purpose of his experiment is to determine the real-world performance of the 700 MHz band in non-line-of-sight conditions. The results obtained will help the future development of "rapidly-deployable public safety networks for disaster situations".

TV-Band White Spaces Database Providers

To complement last week's entry on Google's White Spaces Database Proposal I include here the complete list of proposals for databases for Cognitive Radio Devices:

• Google's proposal
• CommSearch's proposal
• FrequencyFinder's proposal
• KB Enterprieses/LS Telcom's proposal
• Key Bridge's proposal
• NeuStar's proposal
• Spectrum Bridge's proposal
• Telcordia's proposal
• SdB's proposal

TV-Band White Spaces Database

In the previous post about unlicensed access to television band in the US I commented that the call for proposals from intended database providers for TV-band cognitive devices was already closed.

Though this is not directly related to my research I have to confess that I was curious. This week I read the proposal by Google with its view about how this database should be. The points I want to stress are the following:

• Google offers itself as one of multiple database providers. Its proposal suggest that ideally not one but several parties could offer the database services. Then a single entry point (denoted in the document as clearinghouse) could serve as access to the multiple databases. The clearinghouse would disseminate the information among multiple providers which have to define interfaces to keep their information synchronized.


• The database will offer the functions required by the FCC: Repository, Registration and Query. Additionally Google's architecture proposes Synchronization with Other Databases, Public Access Interface and additional Database Services. In order to promote innovation Google suggests that rather than providing a closed functionality, a database could perform a variety of functions that add value and utility to querying devices:
  A TVWS Database Service provider could, for example, combine location-based information with detailed information in the database such as transmitter locations, and use propagation algorithms to produce a ranking of available channels.


• Google recommends to avoid per-query fees, which would discourage database use. Since Google business plans are based on the spread of internet access and not on user fees, the database could be financially supported by Google for at least 5 years.

We see that following the philosophy that characterizes Google the proposal pushes the innovation. To this end they propose an open access interface that everyone could use for developments based on the public information of the database. Moreover, different database providers could offer a variety of functions that would add value their solutions. However, Google uses its dominating position to offer a database solution without requiring additional fees. This on the one hand is good for the final user but on the other hand difficulties the incorporation of new companies interested in offering database solutions.

Image thanks to: SQL Developer.

Unlicensed access to television broadcasting spectrum in the US

November 2008 Federal Communications Commission (FCC) adopts rules for unlicensed access to unused television spectrum in the US. This was a brave decision since the detection technology required for unintrusive spectrum access (usually called cognitive radio) was (and is) not mature yet. In fact the technical proposal FCC 08-260 recognizes the difficulty of completely avoiding the harmful interference to primary users. To overcome the technical drawback of primary signal detection an alternative approach is proposed:

All devices, except personal/portable devices operating in client mode, must include a geolocation capability and provisions to access over the Internet a database of protected radio services and the locations and channels that may be used by the unlicensed devices at each location."

Moreover, to avoid co-channel interference to primary users the FCC proposal rules that even neighboring channels are prohibited to secondary devices. Fixed and personal/portable devices must also have a capability to sense TV broadcasting and wireless microphone signals as a further means to minimize potential interference. The devices that rely only on spectrum sensing to avoid causing harmful interference will be subject to a rigorous process of testing by FCC's Laboratory.

But, how did the proposal evolve?

Analogue television broadcasting switch off in the US was initially planned for the 17th February 2009, day in which unlicensed devices could start to use the spectrum. Though some reports described the transition to digital TV flowing smoothly, the official switch off date was delayed until June 2009.

But only last November the FCC did open the call for proposals from potential database managers.

Potential administrators have to demonstrate expertise and present a business plan for the next five years. Additionally proposals should outline the information stored, a process for incumbents to register, and the query procedure. Some members of the "White Spaces Database Group" are Comsearch, Dell, Fox, Google Inc., Microsoft Corporation, Motorola, NetLogix, Neustar, Phillips, Spectrum Bridge, SWIM and Waterford Consultants, LLC. Now the call is closed and public and industry have until 18th February 2010 to comment on the proposals.

All these delays on the initial plan are motivated because USA is the first country opening the unused spectrum. However the existing technical challenges are being addressed by both american industry and research community. While this happens american companies gain experience and establish an infrastructure that will assure their leadership when other countries start opening this new market.

One question comes to my mind at this point, and is What can Europe learn from this?