1. Regional Seminar on Digital TV Broadcasting
Algiers, 4-5 December 2007
Compatibility of
Digital Broadcasting and
Mobile Services
Where’s my
picture gone? or
Presented by Jan Doeven 1

2. Concerns about Digital Dividend
Analogue TV transferred to digital
Digital dividend
Band IV/V spectrum
Interference scenarios
Non-co-sited transmitters
Moving interference sources
Cross border interference
Digital TV receiver
Selectivity
Channel interactions
If part of the Digital Dividend is allocated to mobile communication services, black screens could be expected. 2

3. Non co-sited transmitters: The issue
Non co-sited transmitters are increasingly used because of:
Different network operators for the same type of service
Different network structures for different service types
The interference is mainly localized around the interfering transmitter site 3

4. Non co-sited transmitters: Coverage gaps
Channel N+x
Where’s my picture gone?
Wanted DVB-T transmitter
Channel N
Interfering
field strength
Maximum acceptable difference between wanted and unwanted signals
Service area
Interference area
Wanted
field strength
Field strength
Distance

5. Non co-sited transmitters: The solution
Careful planning using mitigation techniques:
Remedy
Comment
Cross polarisation
Only effective in case of rooftop reception
Power adjustment
Coverage of second transmitter may not be sufficient
Antenna adjustment
Adequate frequency separation
Provided that GE06 Plan entry with at least 4 channels difference is available
Fill-in transmitter
As SFN; relative expensive
Illustrates multiplexes already allocated
High level of investment:
time. energy and money
consumers, regulators, broadcasters
Interference between non co-sited transmitters is an issue, but still is manageable through careful planning 5

6. Moving interference sources: The issue
Mobile communication systems:
The Downlink is technically similar to broadcasting and therefore can be controlled
The Uplink is initiated from moving terminals and therefore can not be controlled
Radiated energy :
Hand-held to DVB
Mobile hand-held
DVB-T receiver 6

7. Moving interference sources: Portable –indoor and outdoor- reception
Each GE06 Plan entry has a specified reception mode
Portable reception
Portable or rooftop reception
Rooftop reception
Portable (indoor and outdoor) possible in limited area because of high required field strength

8. Moving interference sources: New convenient reception modes
Portable antennas
Indoor reception
USB stick receivers
Hand-held receivers
Mobile in-car receivers
Where’s my picture gone?
Portable and mobile reception can be exposed to interference from mobile uplinks
at very short distances (few metres) 8

9. Moving interference sources: The solution
Band partitioning, with:
Sufficient guard bands
Adequate maximum transmitting power
Sufficiently low out of band emissions
BUT
interference from mobile phone transmissions is not a trivial problem
Guard band 9

10. Cross border interference: to the Mobile service!
Uplink reception at Base station is very sensitive
Sub-band use is not mandatory,
Neighbouring country may continue to use high power broadcasting transmitters in the same sub- band
Cross border coordination becomes very difficult 10

11. Cross border interference: The issue
DVB-T transmitter
Channel N
Interfering Radiated energy :
DVB to Base station
Country B
Country A
Base station receiver
Channel N
Radiated energy :
Hand-held to Base station
Where’s my picture gone?
Mobile hand-held tx

12. The digital receiver Receiver selectivity Channel interactions
Market-based management of radio spectrum in the broadcasting bands is a threat to Europe's broadcasting systems".
Flexibility and spectrum trading may increase the revenue of some players, but may limit efficient use of the spectrum and the plurality of the offer.
They emphasise that, "Consumers have the right to expect more, and not less, from the digital switch-over".

13. Receiver selectivity Overloading and N+9 issues
Average values of 7 DVB-T receivers 64QAM 2/3
C/I (dB)
Channel offset
Source: BBC

14. Receiver selectivity Performance
Out of band protection ratios below specifications under normal operating conditions
Specifications exceeded in case of overloading.
In order to improve compatibility out of band performance need to be improved.

15. Channels interactions: some band-plan examples
DVB-T channel where there could be N+9 interference on some receivers if overloaded
Guard band or duplex gap (between Downlink and Uplink)

16. CONCLUSIONS
Careful planning is needed to avoid interference between non co-sited transmitters;
DVB-T transmitters and mobile base stations.
Interference from mobile uplink transmissions could be an issue even with sub band operation;
Needs careful investigations.
Use of same channel by DVB-T and Mobile uplinks will in borders areas will give severe restrictions to mobile service.
Improved digital receiver performance with regard to interference is required;
In particular in case of overloading. 16

17. To know more about why your picture is gone….
..and what could happen if any Digital Dividend is spent unwisely?
Watch the video at