TV White Spaces devices: how to avoid interference?

Transcription

1 Federal Office of Communications TV White Spaces devices: how to avoid interference? Dr. Vice-chairman CEPT WGSE, Chairman CEPT SE43 The cognitive radio challenge for dynamic and flexible spectrum access 4 July 2011 Bologna, Italy

2 White space White space is a part of the spectrum, which is available for a radiocommunication application at a given time in a given geographical area on a non-interfering / non-protected basis with regard to primary services and other services with a higher priority on a national basis Power Time Spectrum in Use White Spaces Frequency 2

3 How it works Traditional radios are assigned operational lanes WSDs intelligently switch lanes and adjust parameters How to avoid interference to incumbent users? 3

4 CEPT developments June 2008: CEPT Report 24 Definition of a 'white space Call for further studies to enable the use of CR devices within white space spectrum May 2009: Establishment of CEPT SE43 To define technical and operational requirements for the operation of CRS in the white spaces of the band MHz to ensure the protection of incumbent radio services/systems To investigate the consequential amount of spectrum potentially available as white space January 2011: Final approval of ECC Report 159 Extension of the mandate until September

5 Chicken and egg problem of WSD "I hope we re not going to have the same old argument" Industry: Regulators: "There is political and regulatory uncertainty" "Industry has not yet provided convincing use cases" 5

6 WSD characteristics Categories personal/portable devices home/office devices private/public access points Deployment scenarios indoor/outdoor low/high antenna Emission technology OFDM 6

7 Cognitive techniques for WSDs Spectrum sensing WSD conducts a measurement within a candidate channel, to determine whether any protected service is present Geo-location database WSD measures its location and consults a database to determine which channels it can use at its current location Beacons Signals used to indicate that particular channels are either in use by protected services or vacant 7

8 Services to be protected in and outside the band MHz Radio Astronomy 8 MHz White spaces Aeronautical Radionavigation 440 Mobile Service 470 PMSE Digital Broadcasting f, MHz Mobile Service 8

9 Detection threshold for sensing Takes into account the hidden node Depends on the characteristics and deployment scenarios/planning configurations of the WSD and the victim Sensing broadcasting service: detection threshold by fixed WSD (30 m): dbm detection threshold by portable WSD (1.5 m): dbm Sensing PMSE systems: detection threshold: dbm Extremely challenging to implement using current technology! 9

10 Protection of broadcasting service BS tower BS receiver WSD Spectrum sensing, if employed by a stand-alone WSD (autonomous operation) is not reliable enough to guarantee protection of nearby DTT receivers However, a collaborative sensing may help Operation of a WSD assisted by a Geo-location database is currently the most feasible option 10

11 Protection of PMSE systems PWMS receiver WSD Spectrum sensing appears to be problematic Radio microphone Geo-location database appears to be the most feasible approach Disable beacon approach to provide a bubble of protection in locations where PMSE equipment is in use Safe-harbour channels not used by DTT and reserved for PMSE use 11

12 Protection of radio astronomy service ( MHz) Studies revealed very large separation distances between WSDs and RAS observatories Autonomous WSDs (with sensing only): TV channels 37 to 39 should be excluded from operational frequencies Under some conditions this requirement can be relaxed WSDs assisted by a geo-location database: exclusion zones around RAS sites should be defined Requires Up to 450 km consultation between neighbouring administrations 12

13 Protection of fixed/mobile services in adjacent bands Two different methodologies suggested are not fully developed and require further studies Protection of IMT systems above 790 MHz calls for WSDs with very low spectral leakage Optimum trade-off between permitted power and required spectral leakage depends on deployment scenarios and business cases for WSDs Protection of PMR systems below 470 MHz requires WSDs to be separated by few hundreds of meters 13

14 General Principles and requirements for operation of WSDs under the geo-location have been set Information to be exchanged between a WSD and a geolocation database has been identified Administrations are flexible to adopt the geo-location framework to their national circumstances 14

15 Requirements to WSD WSD shall be capable of communicating to the database Geographical location, location accuracy, device type/id/model, expected area of operation WSD shall be capable of receiving from the database Available frequencies, maximum transmit power, appropriate national/regional database to consult, time of validity of the information provided, if sensing is required WSD shall only transmit once it has successfully communicated ( ) with the database The WSD shall stop transmitting immediately if it can not re-consult the database it fails to monitor its location it moves outside the determined area 15

16 Management of database Possible options: Single database on a national or European level, one or multiple databases, public or closed databases subject to further discussions within CEPT Key issues: Technical information on services/systems to be protected Database update frequency Translation process Combined sensing and geo-location approach Cross check of availability of usable frequencies needs further investigations 16

17 Where are we now? 17

18 Further work Defined technical and operational requirements are based on a number of assumptions The analysis and conclusions may be revised in future Information from WSD industry and standard organisations is required Well-established technical characteristics of WSDs The feasibility of autonomous WSDs taking into account collaborative sensing techniques Open regulatory issues (as originated from technical work): Appropriate regulatory regime for geo-location database management Thorough specification of communication protocol/interface between the geo-location database and WSDs 18

19 Thank you Questions 19