CEPT was mandated by the EC to carry out technical activities in order to provide the EU with relevant technical information in preparation for an EU-level policy proposal on how to achieve a suitable coordination, and consistency of approaches, regarding the digital dividend, in view of maximising its overall value. This also aims at developing harmonised conditions for the availability of radio spectrum to be able to satisfy a future demand for pan-European service.
COGEU will extract relevant subsets of existing CEPT specifications in the scope of TVWS access and protection requirements.
CEPT REPORT Title Relevance for COGEU
CEPT REPORT21 [19] “Technical considerations regarding harmonization options for the Digital Dividend”
“Compatibility issues between “cellular / low power transmitter” networks and “larger coverage / high power / tower” type of networks”, March 2007
COGEU coexistence evaluation, protection of DVB-T (WP4)
CEPT REPORT24 [9] “Technical considerations regarding harmonization options for the Digital Dividend” - “A preliminary assessment of the feasibility of fitting new/future
applications/services into non-harmonised spectrum of the digital dividend (namely the so-called "white spaces" between allotments)”, June 2008
COGEU scenarios applications (WP2)
CEPT Report 29 [20] “Technical considerations regarding harmonisation options for the digital dividend in the European Union” “Guideline on cross border coordination issues between mobile services in one
country and broadcasting services in another country”, June 2009
COGEU coexistence evaluation – cross border issues (WP4)
CEPT REPORT 138 [21] “Measurements on the performance of DVB-T receivers in the presence of interference from the mobile service (especially from UMTS)”, Ljubljana, September 2009
COGEU system requirements (WP3) COGEU coexistence evaluation, protection of DVB-T (WP4)
CEPT Report 32 [22] “Recommendation on the best approach to ensure the continuation of existing Program
Making and Special Events (PMSE) services operating in the UHF (470-862 MHz),
including the assessment of the advantage of an EU-level approach”, October 2009 COGEU system requirements (WP3) COGEU coexistence evaluation, protection of PMSE (WP4)
CEPT Draft Report (3rd meeting SE43) [23]
Technical and Operational Requirements for the Possible Operation of Cognitive Radio Systems in the White Spaces of the frequency band 470-790 MHz, January 2010
COGEU system requirements (WP3)
CEPT Report (Draft) [24] Draft ECC Report LTE: “Measurements on the performance of DVB-T Receivers in the presence of interference from the mobile service (especially from LTE)”, February 2010 COGEU system requirements (WP3) COGEU coexistence evaluation, protection of DVB-T (WP4)
CEPT ECC Spectrum Engineering working group 43 (SE43) is defining technical requirements for the operation of Cognitive Radio in the TVWS. An initial report is expected by mid 2010 (www.ero.dk). Two established groups are relevant for COGEU: Determination of detection thresholds and Requirement for Geolocation database. Following the aims of these groups is presented.
3.2.2.1 CEPT SE43: Spectrum sensing and detection thresholds
With spectrum sensing, devices try to detect the presence of protected services in each of the potentially available channels. Spectrum sensing essentially involves conducting a measurement within a candidate channel, to determine whether any protected service is present. When a channel is determined to be vacant, sensing is typically applied to adjacent channels to determine what constraints there might be on transmission power, if any. Some channels may be excluded, because the occupying service is not amenable to protection by sensing. For example, the radio astronomy service on Channel 38.
An increasingly sophisticated array of techniques is being applied to spectrum sensing, yielding enhanced levels of sensitivity, in return for using more detailed knowledge of the signal characteristics of the services in question.
A significant advantage of spectrum sensing (stand alone) is that it does not rely on any existing local infrastructure, such as connection to a database, for example. This may be more important in remote and rural areas. However, if sensing thresholds are set very low, then increasing device cost and complexity is matched with a reduced number of available channels. This would reduce the potential value to end users, particularly in areas of higher population density, and would hinder cost reductions in the technology.
So far analyses of sensing performance assume that detection is carried out independently by each device, in ignorance of results found by other cognitive devices in the same location. The emergence of cooperative sensing in which devices share their findings, brings the potential to reduce the hidden node margin by a substantial amount.
The cooperative sensing devices could for example be on different height, or one devices controls the other. This in turn would enable more relaxed sensing thresholds to be allowed, without compromising the protection afforded to established services.
In addition to a preliminary scanning of the band when a device is installed or powered on, we anticipate that sensing devices will periodically rescan the channel. This will allow them to detect changes in the presence of protected services. For example, a protected service may have started up in a channel previously considered vacant or in one or more of the adjacent channels.
Key parameters for spectrum sensing include: • The sensing threshold;
• Periodicity of re-sensing on channels that have been detected as vacant; • Sampling duration.
3.2.2.2 CEPT SE43: Requirement for Geo-location database
Geo-location appears to be an alternative to sensing. In this approach cognitive devices measure their location and make use of a “geo-location” database to determine which channels they can use at their current location. They are unable to transmit until they have successfully determined from the database which channels, if any, are available in their location.
In this case parameters such as location accuracy and frequency of database enquiry are important. This approach would require fast update (real-time in principle needed) in order to cover/model dynamic components (time variability) in the licensed Network. Considerations need to be made on maintenance, responsibility, geographical coverage, etc.