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

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

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

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

5 Non co-sited transmitters: The solution Careful planning using mitigation techniques: Interference between non co-sited transmitters is an issue, but still is manageable through careful planning RemedyComment 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 transmitterAs SFN; relative expensive

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 Mobile hand-held DVB-T receiver Radiated energy : Hand-held to DVB

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 Portable and mobile reception can be exposed to interference from mobile uplinks at very short distances (few metres) Where’s my picture gone?

Band partitioning, with: Sufficient guard bands Adequate maximum transmitting power Sufficiently low out of band emissions 9 Moving interference sources: The solution Guard band

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

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

The digital receiver Receiver selectivity Channel interactions

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

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.

Channels interactions: some band-plan examples N+9 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.

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