Trials of TV White Space Communications at 40Mbps in Central London

- with Qualified White Space Database under UK Ofcom Pilot -

July 24, 2014

Successfully deployed a 3.7 km link between two locations, and a broadband wireless communications link at more than 40 Mbps throughput, both in central London - a large city which has many TV broadcasters and many active wireless microphone users.
Information about available channels and maximum transmission power in each channel is provided by a database developed by NICT and has passed the qualification tests for the Ofcom’s TV White Spaces Pilot.
Contributions to the development of white space communications regulations of the UK and other countries are expected

The National Institute of Information and Communications Technology (NICT, President: Dr. Masao Sakauchi) has successfully deployed the mobile broadband communications systems at more than 40 Mbps throughput, and has successfully established a 3.7km link between two locations within the framework of the TV White Spaces Pilot organized by Ofcom, the communications regulator of the UK. The trials of NICT systems have been deployed in central London, a big city which has many incumbents to be protected, for example TV broadcasters and active wireless microphone users. NICT has also successfully developed a white space database which passed the qualification tests to be included in the Ofcom’s databases list. This database provides protection from interference to the incumbents by calculating and providing information about available channels and maximum transmission power in each channel to the white space systems. NICT’s trials which deploys TV white space mobile broadband communications based on database information in a crowded city is the first of its kind. The experiences obtained during the trials are expected to contribute to the development of TV white spaces regulations in the UK as well as other countries in the world.

Background

Using TV white spaces is being considered as one of the potential solutions to the high demands on multi-user support and high speed to broadband wireless communications systems. The Ofcom, an independent regulator and competition authority for the UK communications industries has started the TV White Spaces Pilot which provides an opportunity for the stakeholders to conduct tests with their systems and to provide feedbacks to the development of white space communications regulation. In order to join the pilot, the devices have to conform to a set of specifications determined by ETSI which make sure that they will not interfere to the incumbents in the TV bands, while the databases have to conform to a set of specifications determined by Ofcom which requires them to provide operational parameters to the devices. NICT joined the Ofcom’s pilot as both device developer and database developer. Because of the intensive and dynamic use of the spectrum in a large city, it is a challenge that the database uses the most updated incumbents’ information to calculate the operational parameters for the devices in real-time, and the devices regularly communicates with the database to exchange operational parameters.

Achievements

The antenna deployed at the roof of a building in Denmark Hill for the 3.7 km link establishment.

NICT has successfully established the 3.7 km wireless link between two locations, and has successfully achieved more than 40 Mbps throughput for broadband mobile systems in the TV bands. Both trials have been deployed in central London, a crowded city where the white space systems have to avoid interference to a large number of incumbents e.g. broadcasting users and PMSE (wireless microphone, in-ear monitor etc.) users. Using operational parameters provided by a database and successfully deploying mobile broadband communications system in a large city is the first trial of its kind. The details are as follows:

NICT has developed IEEE 802.11af-based system and established wireless connection between two locations separated by 3.7 km in central London. NICT has developed an LTE-based system and provided high throughput at more than 40 Mbps between a base station and a mobile terminal in central London. Both of the systems developed by NICT conform with the ETSI specifications which defines a strict level of unnecessary power emissions in neighboring channels.
NICT has implemented a TV white space database according to Ofcom’s specifications. The database calculates and provides operational parameters to the white space systems by taking into account the dynamically changed information about spectrum usage of the incumbents such as TV broadcastings and wireless microphones. The operational parameters include locations, occupied channels, transmission power and transmission schedule.

Future prospects

Based on the experiences and the results obtained from the trials, NICT plans to improve the performance of the devices and the database. NICT also expects to contribute these experiences to the development of white space relevant regulations in other countries, as well as to transfer their white space technologies to the stakeholders.

Acknowledgements

The deployment of the equipments was at the Denmark Hill and Guy's campuses of King's College London. NICT appreciates sincere thanks to the assistance from King's College London in these trials.

Appendix

NICT has verified the operations of the broadband mobile communications system and the backhaul communications system between two fixed points on TV white spaces during the trials.

Regarding the broadband mobile communications system, the operations of the LTE-based system in TDD mode using one channel and in FDD mode using two separate channels have been confirmed. The LTE-based system has also achieved more than 40 Mbps throughput (downlink) when operated in FDD mode by using 20 MHz bandwidth of three consecutive channels. Regarding the backhaul communications system between two fixed points located in central London which are separated by 3.7 km, the system has achieved more than 2 Mbps throughput at maximum transmission power 36 dBm (EIRP) based on the operational parameters provided by the database (See Figure 1).

It should be noted that in central London there is a very high power TV tower nearby. There are also many PMSE users who operate at different locations, channels and schedules. It was a big challenge for us to operate the TV white space communications systems in such environment by looking for suitable channels and suitable transmission power. The trials reminded us about the unique characteristics of spectrum usage in the TV bands in large and crowded cities, and clarified the performance requirements to TV white space communications systems operating in this environment. It is expected that the experiences and the results obtained from the trials will contribute to the R&D of TV white space communications systems, and to the development of regulations regarding TV white space communications.

Figure 1: Trials locations and system deployments for the fixed point-to-point communications

Figure 2: NICT’s TV white space database and provided operational parameters

Figure 2 shows the graphical user interface (GUI) of the TV white space database developed by NICT. The database conforms to Ofcom’s specifications. It has passed the qualification tests and has been included in the list of databases to be used by any stakeholder during the Ofcom’s TV White Spaces Pilot. There are input fields for the antenna location, antenna height, device type and device class etc. Based on input values the database calculates maximum transmission power in each channel and the validity time then provides these operational parameters to the devices. The database has a function to stop providing operational parameters to any device, or to a group of devices located within a geographical area (which is called “kill switch”). This function is used to stop the operation of certain device(s) under the request of Ofcom, for example to support the investigation about interference. The database has to update within a specified time after receiving the power adjustment requests or the scheduled/unscheduled updates of PMSE information and has to use the latest information for its calculation. Due to this specification the maximum transmission power in each channel varies from time to time. As a result the channel availability can change after a short time, which has been verified during the trials.

Glossary

Ofcom’s TV White Spaces Pilot

The pilot was organized by Ofcom to aim to test all interactions between devices and databases; to provide an opportunity for industry to conduct trials using the proposed framework; and to gain further information on the coexistence issues between new use by white space devices and existing use for DTT and PMSE.
TV White Spaces Pilot:

http://stakeholders.ofcom.org.uk/spectrum/tv-white-spaces/white-spaces-pilot/

Qualifying White Space Databases:

https://tvws-databases.ofcom.org.uk/

Ofcom

Ofcom (Office of Communications) is the communications regulator of the UK.

TV White spaces

TV band frequencies which can be used by communication systems under some certain conditions determined by each regulator.

PMSE

Programme Making and Special Events. PMSE includes radio mic, in-ear monitor, talkback etc.

NICT white space systems

NICT’s IEEE 802.11af-based system: Press release, “World’s First TV White Space WiFi Prototype Based on IEEE 802.11af Draft Standard Developed”, October 17, 2012,
https://www.nict.go.jp/en/press/2012/10/17-1.html
NICT’s LTE-based system: Press release, “Alleviating Overcapacity, Specially Developed Smartphone Utilizing TV Whitespace with LTE Technology”, March 19, 2014,
https://www.nict.go.jp/en/press/2014/03/19-1.html