1. Mobile Broadcast and Spectrum Issues (DVB-T) Workshop April 2003
TECHNICAL ASPECTS IN SPECTRUM ALLOCATION FOR DVB-UMTS CONVERGENCE TERMINALS
DVB-UMTS & EICTA MBRAI
Mobile Broadcast and Spectrum Issues (DVB-T) Workshop April 2003
Pekka Talmola

2. DVB-UMTS Group and EICTA
DVB ad hoc Group UMTS work items
Co-operative services by joint utilisation of DVB and UMTS technologies
Concepts for terminals in co-operative networks, especially:
Convergence terminals using both DVB-T and
cellular radio services such as GSM, GPRS and UMTS.
Further work have been done and will be done in EICTA MBRAI
Mobile and Portable DVB-T Radio Access Interface Specification.
Deals also with interoperability issues between cellular and DVB-T.

3. Targets
Tight integration of the radio systems within the terminal unit.
Practical limitations to the terminal design and operating frequency allocations.
This document reviews the technical merits from the terminal point of view of various frequency bands that could be reserved for use by convergence terminals.
DTV
DVB - T
BCP
Mux
DVB - T
transmitter
broadcast network operator
Mobile
terminal
DVB -
UMTS
IP data
WCP p - t - p
core
RAN
network
UMTS / UTRA
GPRS / GERAN
mobile operator
Scenario 2: IP services co-ordinated on UMTS and DVB networks

4. Problem Areas
RF Immunity for DVB-T reception from the Cellular transmitter
Out of band spurios products
Blocking
Transmitter wideband PA-noise
Internal unwanted coupling
Power consumption of the DVB-UMTS terminal
Battery operated terminal
Very high linearity requirements in RF due to the high power level differences
Antenna efficiency
Small integrated antennas
Very wide frequency range to support in the worst case

5. Design Aspects 1: Antenna Efficiency
The antenna size will be small probably less than /10 ->Real part of the antenna impedance will be small, most of the radiation comes from the ground plane.
Wide frequency range (UHF) means that resonant designs are impossible ->Tuneable matching circuit has to be designed
Matching small resistive part of the antenna to receiver input with tuneable circuit will be lossy. ->Antenna gain will be very low, in the order of -5dBi to –10 dBi
Combining VHF III to this kind of antenna would mean extremely low antenna gain, much less than –10 dBi. ->VHF III is unpractical
Being able to narrow the band to about 80 MHz (10 channels) would enable resonant designs (point frequency) and higher antenna gains from –3 to 0dBi range.
High UHF-frequencies have slight advantage over the lower ones

6. Design Aspects 2: Doppler Shift
Often misunderstood as the decisive factor for mobile reception, but is still important.
In UHF low frequencies will give 1.5 times advantage over the high UHF
Current demodulators give rather good performance
> 100 km/h with 8k 16QAM MHz
VHF III will give >2 advantage over low UHF
This is, however, needed only in very special cases like high speed trains.
Low or mid UHF is sufficient for most applications.

7. Design Aspects 3: Cellular Interoperability
Spurious carrier like emissions in UHF are not a major problem
Blocking of the DVB-T receiver can be problem
Can be handled by DVB-T pre-filtering
GSM Tx +33 dB at 880 MHz
Max allowed at the DVB-T input is –35 dBm
68 dB total filtering requirement
10 dB from antenna isolation
58 dB filter requires at least 100 MHz transition band
Tx-noise
Wideband noise from the Tx PA
G=20 dB, NF=15 -> Pn= -70 dBm
20 dB more than 16QAM sensitivity!
PA gain drops at lower frequencies
HP Filter at Tx output would be easier to implement for low DVB-T Rx freq.
Going below 600 MHz would probably be a useful solution.
880 MHz
960 MHz
858 MHz
GSM Tx
+33 dBm

8. Design Aspects 4: Propagation & Interference
Lower frequencies in UHF or VHF III give advantages in propagation.
In principle better coverage.
In practise this advantage will be balanced out by the worse antenna efficiency at these frequencies.
Impulse interference will be a problem for portable devices
At low frequencies, especially VHF III interference level is considerably higher.

9. Design Aspects 5: Harmonisation
A harmonised approach to the frequency range would be highly desirable enabling economics of scale to be used.
VHF III would clearly not allow this and any terminal having VHF III would also have to support UHF

10. Conclusion
Giving marks for various design aspects from --- to +++ will result the following conclusion:
The conclusion is that when simultaneous use of cellular
900 MHz radios is required low UHF-band should be used.
Band IV (474MHz to 602 MHz) could be suitable compromise,
having 17 channels.