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Compatibility of Digital Broadcasting and Mobile Services

Regional Seminar on Digital TV Broadcasting

Algiers, 4-5 December 2007

Presented byJan Doeven

Where’s mypicture gone?

or

2

Interference scenarios

Non-co-sited transmitters

Moving interferencesources

Cross border interference

Digital TV receiver

Selectivity

Channel interactions

Concerns about Digital DividendAnalogue 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

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Non co-sited transmitter

Channel N+x

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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

Remedy Comment

Cross polarisationOnly effective in case of rooftop reception

Power adjustment Coverage of second transmitter may not be sufficientAntenna adjustment

Adequate frequency separation

Provided that GE06 Plan entry with at least 4 channels difference is available

Fill-in transmitter As 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-heldDVB-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

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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)

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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-TtransmitterChannel N

Interfering Radiated energy :DVB to Base station

Country A Country B

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The digital receiver

Receiver selectivity

Channel interactions

Receiver selectivityOverloading and N+9 issues

Source: BBCChannel 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)

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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.

To know more about why your picture is gone….

Watch the video at

www.ebu.ch

..and what could happen if any Digital Dividend is spent unwisely?