Ecc Report 138 Measurements on the Performance of Dvb-t Receivers ...

8/8/2019 Ecc Report 138 Measurements on the Performance of Dvb-t Receivers ...

1/25

ECC REPORT 138

Electronic Communications Committee (ECC)

within the European Conference of Postal and Telecommunications Administrations (CEPT)

MEASUREMENTS ON THE PERFORMANCE OF DVB-T RECEIVERS IN THE

PRESENCE OF INTERFERENCE FROM THE MOBILE SERVICE

(ESPECIALLY FROM UMTS)

Ljubljana, September 2009


2/25

ECC REPORT 138Page 2

0 EXECUTIVE SUMMARY

Justification

This Report summarises the CEPT activity relating to measurements on the performance of DVB-T receivers in terms

of measured carrier-to-interference protection ratios and overloading thresholds in the presence of interference from

the mobile service, especially that from UMTS. It is aimed to assist administrations seeking to protect theirbroadcasting services in the band 470-790 MHz from interference generated by UMTS services in the band 790-862

MHz.

Findings

In general, protection ratios show a decrease in values (from -31 to -67 dB for the base station interference and from -

5 to -55 dB for the user equipment interference) as the frequency offset increases. However, the protection ratio in theimage channel is similar to the one in the third adjacent channel. The overloading threshold shows only small

variations with frequency offset.

At equal frequency offsets the impact of user equipment interference into DVB-T receiver is considerably higher thanthe one from the base station, the effect being linked to the use of transmit power control. In particular, the latter

increases the required protection ratio by 12-26 dB and decreases the overloading threshold detected by 7-11 dB

depending on the frequency offset.

Further studiesIt is expected that LTE will be more widely deployed than WCDMA mobile service (UMTS) in the band 790-862MHz. Therefore, measurements on LTE interference into DVB-T reception will need to be carried out in order to

assess the impact of this on the broadcasting service.

First measurements on LTE BS and UE interference into DVB-T receivers indicate a general agreement with the

results presented in this report in static conditions. However, the dynamic conditions and the impact of the timevariation of the interfering signal need to be studied in more detail. Therefore, not all of the conclusions may be

transferred unchanged to the LTE case.

The results of these studies will be set out in a subsequent Report of ECC/TG4.


3/25


Table of contents

0 EXECUTIVE SUMMARY................ ....................................................................................................... .............. 2

1 INTRODUCTION .................................................................................................. ................................................. 5

2 USEFUL DEFINITIONS........................................................... ............................................................................. 5

2.1 RADIO FREQUENCY SIGNAL-TO-INTERFERENCE RATIO (C/I)............................................................................ 52.2 RADIO FREQUENCY PROTECTION RATIO (PR)................................................................................................... 52.3 RECEIVERBLOCKING......................................................................................................... ............................... 52.4 RECEIVER(FRONT-END) OVERLOADING THRESHOLD ....................................................................................... 5

3 CRITERIA TO BE USED WHEN ASSESSING INTERFERENCE................................................................ 6

4 MEASUREMENTS..................................................................................................... ............................................ 6

4.1 BROADCASTING SERVICE PARAMETERS ........................................................................................... ................ 64.2 MOBILE SERVICE PARAMETERS ........................................................................................................ ................ 64.3 TEST PROCEDURE............................................................................................. ................................................. 9

4.3.1 Measurements under static conditions ............................................................................. .......................... 94.3.2 Measurements under dynamic conditions ......................................................................................... ......... 9

4.4 RESULTS OF FIELD MEASUREMENTS ............................................................................................ ................... 12

5 PROTECTION RATIOS....................... ................................................................................................. .............. 125.1 EFFECT OF UETRANSMIT POWERCONTROL (TPC) ...................................................................................... 14

6 CONCLUSION ...................................................................................................... ................................................ 15

6.1 FURTHER STUDIES.......................................................................................... ................................................. 15

ANNEX A: PROTECTION RATIO MEASUREMENTS OF DVB-T INTERFERENCE INTO USB DVB-T

RECEIVERS...................................................................................... .............................................................................. 16

ANNEX B: MEASUREMENTS ON PROTECTION OF DVB-T RECEIVERS INTERFERED WITH BY LTE

SIGNALS........................................................................................ .................................................................................. 17

ANNEX C: CORRECTION FACTORS FOR PROTECTION RATIOS FOR PORTABLE AND MOBILE

DVB-T RECEPTION......... ..................................................................................................... ........................................ 22

ANNEX D: TREATMENT OF OVERLOADING THRESHOLD........................................................................... 23


4/25


LIST OF ABBREVIATIONS

ACLR Adjacent Channel Leakage Ratio

AWGN Additive White Gaussian NoiseBS Base station

BEM Block Edge Mask

BER Bit error ratioCEPT European Conference of Postal and Telecommunications Administrations

COFDM Coded Orthogonal Frequency Division Multiplexing

DVB-T Digital Video Broadcasting Terrestrial

ECC Electronic Communications CommitteeFDD Frequency Division Duplex

GE06 The Geneva 2006 Agreement and Plan

GSM GlobalSystem for Mobile communicationsIMT International Mobile Telecommunications

ITU-R International Telecommunication Union - Radiocommunication Sector

LTE Long Term Evolution

PF Picture failures

RRC-06 Regional Radiocommunication Conference, Geneva 2006TPC Transmit Power Control

UE User equipment

UMTS Universal Mobile Telecommunications SystemWCDMA Wideband Code Division Multiple Access

WRC-07 World Radiocommunication Conference 2007


5/25


1 INTRODUCTION

WRC-07 co-allocated the band 790-862 MHz (channels 61-69) to the mobile service (except aeronautical mobile) on

a primary basis from 17 June 2015 in Region 1 with an identification of the band for IMT. In some European

countries this allocation is valid before 2015 subject to technical coordination with other countries contracting to the

GE06 Agreement.This report summarises the CEPT activity relating to measurements on the performance of DVB-T receivers in the

presence of interference from the mobile service, especially that from UMTS.

The measurements described in this report were used to develop the channelling arrangements for the mobile services

in the band 790-862 MHz and the block edge mask applicable to the 790 MHz boundary (see CEPT Reports 030 [1]

and 031 [2] for more details).

2 USEFUL DEFINITIONS

2.1 Radio frequency signal-to-interference ratio (C/I)

It is the ratio, generally expressed in dB, of the power of the wanted signal to the total power of interfering signals and

noise, evaluated at the receiver input (see Rec. ITU-R V.573-5 [3]).

Usually, C/I is expressed as a function of the frequency offset between the wanted and interfering signals over a widefrequency range. In this document, C/I expressed in this way is referred to as C/I curve. C/I curves show the ability

of a receiver to discriminate against interfering signals on frequencies differing from that of the wanted signal.

2.2 Radio frequency protection ratio (PR)

It is the minimum value of the signal-to-interference ratio required to obtain a specified reception quality under

specified conditions at the receiver input (note that this differs from the definition in Rec. ITU-R V.573-5 [3]). In this

report, the specified reception quality and the specified conditions have been defined separately by each entitythat has undertaken measurements.

Usually, PR is specified as a function of the frequency offset between the wanted and interfering signals over a wide

frequency range. In this document, PR specified in this way is referred to as PR curve. PR curves show the ability ofa receiver to discriminate against interfering signals on frequencies differing from that of the wanted signal.

2.3 Receiver Blocking

Receiver blocking is the effect of a strong out-of-band interfering signal on the receivers ability to detect a low-level

wanted signal. Receiver blocking response (or performance level) is defined as the maximum interfering signal level

expressed in dBm reducing the specified receiver sensitivity by a certain number of dB's (usually 3 dB).

Consequently, the receiver blocking response is normally evaluated at a wanted signal level which is 3 dB above thereceiver sensitivity and at frequencies differing from that of the wanted signal.

2.4 Receiver (front-end) overloading threshold

Overloading threshold (Oth) is the maximum interfering signal level expressed in dBm, where close to that level thereceiver loses its ability to discriminate against interfering signals at frequencies differing from that of the wanted

signal.In some cases the interfering signal may so strongly overload the receiver front-end that the receiver becomes blind

and thus unable to receive anything at all. In most cases, receiver overloading happens beyond the first adjacent

channels. Under overloading conditions (I>Oth), the receiver is interfered with by the interfering signal whatever the

wanted signal level.


6/25


3 CRITERIA TO BE USED WHEN ASSESSING INTERFERENCE

DVB-T systems use coded orthogonal frequency division multiplexing (COFDM) which spreads the information overa large number of orthogonal carriers. Forward error correction is then applied to improve the bit error ratio (BER). In

many digital systems the data to be transmitted undergoes two types of FEC coding; Reed Solomon and convolutional

coding (Viterbi). At the receiver end, the pseudo-random sequence added at the transmitter by the convolutional

encoder is decoded by the Viterbi decoder, followed by Reed Solomon decoding for parity checking.The error protection employed by such digital systems usually results in an abrupt cliffedge effect in the presence of

interference when compared to analogue systems. The different criteria to be used when assessing interference todigital systems include:

Post Viterbi BER=2x10-4 A measure of the number of un-correctable Transport Stream errors in a defined period (sometimes also

normalized to Error Seconds).

Picture Failure. Number of observed (or detected) picture artefacts in a defined period. Subjective failure point

The reference BER, defined as BER = 2 x 10-4

after Viterbi decoding, corresponds to the quasi error free (QEF)

criterion in the DVB-T standard, which states less than one uncorrelated error event per hour. However, there is

often no direct way of identifying BER or transport stream errors for commercial receivers. In this case picture failure

(PF) is the only means of assessing the interference effects.

4 MEASUREMENTS

4.1 Broadcasting service parameters

The DVB-T parameters shown in Table 1 were used as the wanted signal source.

DVB-T signal parameters

Modulation Centre

frequency

(MHz)

Number

of carriers

Channel

raster (MHz)

Coding rate Guard interval

COFDM-64-QAM 786 8k mode 8 2/3 1/32

Average receiver sensitivity measured (dBm) Wanted signal levels used (dBm)

-81 -75, -70, -60, -50, -40 and -30

Table 1

4.2 Mobile service parameters

Interfering UMTS signal parameters are given in Table 2. The restriction of 488 frames (7320 bits) put on theTransmit Power Control (TPC) pattern length was necessary to keep the time needed to generate UMTS frames

reasonable. The finite TPC profile was periodically repeated to simulate TPC profile of infinite duration.


7/25


UMTS (3GPP version 6)

Access technique Modulation Modulation filter

CDMA/FDD QPSK single carrier Root raised cosine =0;22

Channel raster Chip rate Data rate DL DPCH/ UL DPDCH&DPCCH

5 MHz 3,84 Mbps 30 ksps / 60&15 ksps1

Mode DL/UL Scrambling mode UL TPC pattern length/step

DPCH /

DPDCH&DPCCH

Long 7320 bits (488 frames)/1 dB

Generated UMTS BS

signal ACLR3

(dB/5MHz); TPC off

Generated UMTS UE

signal ACLR2,3

(dB/5MHz); TPC on

50 (fc=792.5 MHz)

48 (fc=812.5 MHz)

49 (fc=858 MHz)

35 (worst case, fc=817.5)

(best case fc=817.5)

1No impact was observed on the measurements results at lower and higher data rates

2high variation of ACLR due to the TPC profile used in the measurements

3 Measured with a rectangular filter of 5 MHz bandwidth. This definition of ACLR is

different from the ACLR definition used in the 3GPP specifications (see 3GPP TS

25.101 [4] and 25.104 [5]) and thus the values shown above cannot be directly

compared with the ACLR requirements given in the 3GPP specifications high variation

of ACLR due to the TPC profile used in the measurements.

Table 2

It should be noted that the generated UMTS interfering signal out-of-band power was lower than specified in 3GPPrequirements for UMTS base stations (BS) and user equipment (UE) (see Figures 1 and 2). However ECC/SE42 has

defined a block edge mask (BEM) which will need to be respected by ECN base stations emitting into the frequency

range below 790 MHz. ACLR values calculated from this BEM would be more stringent than the values used for the

measurement in this report. Improvement in ACLR values result in a slightly improved PR in the 1st

adjacent channeldue to reduction of out-of-band emission of the interfering transmitter.

The preferred band plan is defined for a FDD mobile system. In most cases the UE contains a duplex filter to preventinterference into its own receiver. Usage of such a filter will at the same time further reduce the required protection

ratio in the 1st

adjacent channel due to reduction of out-of-band emission of the interfering transmitter.


8/25


UMTS BS inter fer ing signal w ithout TPC; RMS dete ctor

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

806.5 808.5 810.5 812.5 814.5 816.5 818.5

Frequency (MHz)

dBm

/10kHz

UMTS BS emission mask defined for P=43dBm (ETSI TS 125 104)

Spectrum analyser noise floor

Figure 1

UMTS UE inter fer ing signal

Max PEAK detector; Max HOLD mode

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

802.5 804.5 806.5 808.5 810.5 812.5 814.5 816.5 818.5 820.5 822.5

Frequency (MHz)

dBm

/10kHz

UMTS UE emission mask (ETSI TS 125 101)UMTS UE TPC offUMTS UE TPC onSpectrum analyser noise floor

Figure 2


9/25


4.3 Test procedure

Ten different DVB-T receivers (set-top boxes available on the market in 2008, can type tuners), which are consideredto be typical DVB-T receivers, were tested against UMTS interference in a Gaussian channel environment.

In addition, measurements have been conducted in the United Kingdom to characterise the performance of USB TV

devices in the presence of DVB-T interference. The results have been compared to the RF performance of a typical

set-top box DVB-T receiver. The results of the measurements are given in Annex A to this report and can be used toextrapolate the impact of UMTS interferer on overall performance of the USB TV devices. The relatively poor

performance as the channel offset is increased of the USB stick tuners for computer viewing should be noted as acause for concern. These are miniaturised units and appear to have compromises in their design, when compared with

the RF selectivity of tuners tested in digital set-top boxes and current digital TV sets.

The DVB-T receiver signal-to-interference ratios (C/I) were measured, in the presence of a UMTS interfering signal,

at six different wanted signal levels: -75, -70, -60, -50, -40 and-30 dBm. The objective was to evaluate the receiver PR

and Oth. Setting the wanted signal at relatively high levels permitted feeding into the receiver under test strongerinterfering signals than those fed into it at lower wanted signal levels. In principle, C/I measured at C ref are 3 dB

higher than those measured at higher wanted signal levels. Actually, when the measurements are conducted at a

wanted signal level close to the receiver noise floor, the impact of the receiver noise on the measurement results is not

negligible. Consequently, at wanted signal level close to receiver sensitivity, noise should be taken into account, e.g.

at sensitivity + 3dB, 3 dB should be added to the PR.

First measurements on LTE-signals interfering into DVB-T reception were performed under static conditions (i.e.with no signal variation in the time domain) and showed certain similarities with the measurements on UMTS

interference. These findings provide first insight into how DVB-T will behave in the presence of LTE interfering

signals (see Annex B for more details). However, further measurements are required, in particular, studying time-

variant signal interference, before concluding on the issue, and it is expected that another ECC report will provide

protection ratio measurement results applying to LTE technology.

4.3.1 Measurements under static conditions

Receiver sensitivity as well as protection ratio were determined to ensure the absence of picture failure during a

minimum observation time of 30 s. The wanted and interfering signal levels were measured at the receiver input as the

rms power in an additive white Gaussian noise (AWGN) channel. Measurement results were noted as C/I.

4.3.2 Measurements under dynamic conditions

Transmit Power Control (TPC) is one of the most important features of cellular mobile communication systems like

GSM, UMTS and LTE. In particular, in UMTS, for an optimal reception in the uplink, all UE signals should reach the

base station receiver with the same signal power. Actually, if the UE transmitted at a fixed power level, the cells

would be dominated by users closest to BS and distant users could not be distinguished by BS (Near-Far problem).TPC is also a very effective method to compensate the UE/BS signal amplitude variations, which are mainly due to

fading, in the uplink (UEBS) as well as in the downlink (BSUE). Furthermore, TPC is an efficient method of

reducing UE power consumption.

In principle, the transmitted UMTS signal subjected to TPC is received with a quasi-constant amplitude by the UMTS

receiver as shown in Figure 3, ensuring a given SIR or BER/BLER at the receiver. This is particularly true for mobile

speeds lower than 50 km/h.


10/25


Basic Transmit Power Control (TPC) concept

Uplink case ; UE spe ed = 3 km /h

-65

-60

-55

-50

-45

-40

-35

0 0,2 0,4 0,6 0,8 1

Time (s)

Amp

litude

(dBm

)

UE signal subjected to fading - No TPC

UE signal w ith TPC responding to f adingUE signal w ith TPC received by BS

Figure 3

However, via a different transmission path, the same UMTS signal can be received with a time-varying amplitude bya victim receiver (e.g. by a DVB-T receiver). The range of the amplitude variation may reach several tens of dB

depending on the UMTS UE speed and the environment.

In the UMTS downlink, UMTS BS is continuously requested to vary its output power by several UMTS UE

communicating with it through statistically independent time-varying transmission paths. Accordingly, UMTS BS

increases or decreases the amplitude of the baseband signal intended for each UMTS UE concerned. Then, all the

baseband signals are added, including the pilot signal (CPICH) which is not subjected to TPC, to build up the complexenvelope of the UMTS BS signal. Note that generally 5-15 % of the total BS power is devoted to CPICH (about 10%

in the case of urban/suburban deployment).The addition of all these independently varying signals has an averagingeffect and thus minimises the amplitude variation of the UMTS signal fed into the BS power amplifier. Therefore, onemay logically expect that UMTS BS output power variation due to TPC in the downlink is less significant than the

UMTS UE output power variation due to TPC in the uplink.

For the aforementioned reason, in this measurement campaign, DVB-T PR and Oth in the presence of a UMTS BSinterfering signal were measured only under static conditions (TPC off). For DVB-T PR and Oth measurements in the

presence of a UMTS UE interfering signal, the latter was subjected to a 3 km/h TPC profile with a dynamic range of

20 dB that is shown in Figure 4. This profile was derived by measuring the fading profile on a spectrum analyser forCase 1 defined in ETSI specifications TS 125 101 [4] and TS 125 104 [5].

The objective of the measurements conducted under dynamic conditions was to evaluate the impact of the time

varying UMTS interfering signal on the DVB-T receivers. It can be also noted that in a measurement conducted in theUK on a specific receiver, protection ratios were approximately independent of mobile terminal speed.


11/25


UMTS UE inter fer ing signal amplitude variation

3 km /h TPC profile; Aref

= maximum interfering s ignal amplitude

-24

-22

-20

-18

-16

-14

-12

-10

-8

-6

-4

-2

0

0 0,5 1 1,5 2 2,5 3 3,5 4 4,5

Time (s)

Relativeto

Aref

(dB

)

Ideal TPC prof ileQuantized TPC prof ileTPC prof ile implemented in UMTS UE signal generator

Figure 4

Figure 5 shows the waveform measured at the UMTS generator output. This waveform is quite similar to the TPCprofile implemented in the generator. The profile was kept unchanged during the measurements; different UMTS

interfering signal levels were obtained by means of a variable RF attenuator.

UMTS generator output

Max rms average power at the DVB-T receiver input = 6 dBm/5MHz

-10

-5

0

5

10

15

0 1 2 3 4 5

Time (s)

Relativeamplitude(dB)

UMTS generator output (UE; TPC on) Average value

Figure 5

Under dynamic measurement conditions PR and O th were determined to ensure the absence of picture failure during aminimum observation time of 30 s. The interfering signal level was measured as the rms average power in an additive

white Gaussian noise (AWGN) channel. Measurement results were noted as C/I.


12/25


4.4 Results of field measurements

A field study has been undertaken jointly by the EBU and Free TV Australia in August 2008 making use of the

existing UMTS (WCDMA) network in Australia in the 850 MHz band1. The study aimed to carry out real tests of

compatibility between DVB-T2 reception on one side and UMTS base station and mobile terminal transmissions onthe other side. The results of the study were made available to ITU-R in the context of JTG 5-6 activities.

Although the Australian DVB-T system is based on 7 MHz raster, the measurements results are broadly comparable to

those carried out in Europe and presented in section 5 to this report. The significant finding was that there was definiteinterference between a UE and a close proximity receiving DVB-T antenna, when the UE is in close frequency

proximity to the DVB-T receive channel. The interference occurred within an order of a few meters separation. This

finding confirms that the decision to reverse the duplex direction in CEPT is correct.

5 PROTECTION RATIOS

The protection ratios presented in this section have been measured for DVB-T 8 MHz bandwidth system variant 64-QAM 2/3 for static reception conditions (Gaussian channel). Protection ratios for different DVB-T system variants

relative to 64-QAM 2/3 DVB-T signal and for different reception conditions can be obtained using correction factors

given in Table A.4.4-15 of the RRC-06 Final Acts. These correction factors are repeated in Table 3 and are to be

added to the protection ratios for a DVB-T 64-QAM 2/3 Gaussian channel:

Table 3: Correction factors for protection ratios (dB) for different system variants relative to 64-QAM 2/3

DVB-T signal and for different reception conditions interfered with by other primary services

1 The report can be downloaded from ftp://sydney:[email protected]

2 DVB-T system variant considered: 64 QAM 2/3

DVB-T system

variant

Gaussian

channel

Fixed

reception

Portable

outdoor

reception

Portable

indoor

reception

Mobile

reception

QPSK 1/2 13.5 12.5 10.3 10.3 7.3

QPSK 2/3 11.6 10.5 8.2 8.2 5.2

QPSK 3/4 10.5 9.3 6.9 6.9 3.9

QPSK 5/6 9.4 8.1 5.6 5.6 2.6

QPSK 7/8 8.5 7.1 4.5 4.5 1.5

16-QAM 1/2 7.8 6.8 3.6 3.6 1.6

16-QAM 2/3 5.4 4.3 2.0 2.0 1.0

16-QAM 3/4 3.9 2.7 0.3 0.3 2.7

16-QAM 5/6 2.8 1.5 1.0 1.0 4.0

16-QAM 7/8 2.3 0.9 1.7 1.7 4.7

64-QAM 1/2 2.2 1.2 1.0 1.0 4.0

64-QAM 2/3 0.0 1.1 3.4 3.4 6.4

64-QAM 3/4 1.6 2.8 5.2 5.2 8.2

64-QAM 5/6 3.0 4.3 6.8 6.8 9.8

64-QAM 7/8 3.9 5.3 7.9 7.9 10.9

Note: Recent measurements of IMT BS interference into DVB-T reception for Gaussian and time-

variant Rayleigh channels indicate that the correction factors of Table 3 for mobile reception are moreappropriate also for portable reception than those given in Table 3 for portable reception. It is therefore

recommended to use the correction factors for mobile reception for both portable and mobile reception.Details can be found in Annex C.


13/25


The overloading thresholds are assumed to be independent from the reception conditions.

The protection ratio for a frequency offset of plus 72 MHz corresponds to the spurious response at the imagefrequency.

Using statistical analysis the 10th, 50

th, and 90

thpercentile of all measured protection ratios and the 10

th, 50

th, and 90

th

percentile of all measured overloading thresholds for UMTS interference into DVB-T were calculated. They are listedin Table 4 and Table 5 for the interfering signal defined as the average and as maximum rms power, respectively. The

frequency offset is measured between the central frequencies of wanted and interfering signals.

DVB-T PR and Oth for 64-QAM 2/3 DVB-T signal

(UMTS BS TPC off)

PR (dB) Oth (dBm)fi-fw (MHz)

10th 50th 90th 10th 50th 90th

0 16 18 19 NR NR NR

6.5 -36 -31 -26 -15 -9 -3

7.5 -38 -33 -28 -14 -8 -2

8.5 -40 -35 -30 -13 -7 -1

11.5 -46 -41 -35 -9 -4 2

16.5 -55 -41 -28 -9 -2 4

21.5 -61 -45 -29 -12 -4 3

26.5 -64 -51 -38 -14 -5 5

31.5 -71 -57 -44 -15 -6 3

36.5 -73 -45 -17 -14 -6 2

41.5 -75 -66 -56 -13 -5 3

46.5 -72 -63 -54 -12 -4 4

51.5 -76 -66 -56 -12 -4 5

56.5 -76 -67 -57 -12 -3 6

72 -53 -48 -42 -12 -1 9

NR: Oth is not reached. That is at this frequency offset PR is the predominant criterion. Consequently,

DVB-T receiver is interfered with by the interfering signal due to insufficient C/I (


14/25


DVB-T PR and Oth for 64-QAM 2/3 DVB-T signal

(UMTS UE TPC on)

PR and Oth relative to the interfering

signal rms average power

PR and Oth relative to the interfering

signal maximum rms power

PR (dB) Oth (dBm) PR (dB) Oth (dBm)fi-fw (MHz)

10th 50th 90th 10th 50th 90th 10th 50th 90th 10th 50th 90th

0 30 30 31 NR NR NR 18 18 19 NR NR NR

6.5 -7 -5 -3 NR NR NR-19 -17 -15 NR NR NR

11.5 -29 -22 -14 -21 -14 -8 -41 -34 -26 -9 -2 4

16.5 -37 -25 -14 -18 -13 -8 -49 -37 -26 -6 -1 4

21.5 -39 -28 -16 -18 -12 -6 -51 -40 -28 -6 0 6

26.5 -43 -33 -24 -19 -12 -6 -55 -45 -36 -7 0 6

31.5 -56 -42 -28 -21 -13 -5 -68 -54 -40 -9 -1 7

36.5 -60 -32 -4 -27 -17 -8 -72 -44 -16 -15 -5 4

41.5 -64 -53 -42 -21 -13 -5 -76 -65 -54 -9 -1 7

46.5 -60 -51 -42 -21 -13 -6 -72 -63 -54 -9 -1 6

51.5 -64 -54 -44 -21 -13 -5 -76 -66 -56 -9 -1 7

56.5 -65 -55 -45 -21 -13 -4 -77 -67 -57 -9 -1 8

72 -41 -36 -30 -22 -12 -2 -53 -48 -42 -10 0 10

NR: Oth is not reached. That is at this frequency offset PR is the predominant criterion. Consequently,DVB-T receiver is interfered with by the interfering signal due to insufficient C/I (


15/25


signal subjected to TPC compared to a UMTS signal without TPC. This phenomenon is shown in Figure 2. This

seems to be the main reason why UMTS UE TPC has a negative impact on the DVB-T receiver performance.

The impact of a UMTS signal subjected to TPC on a DVB-T receiver cannot be linked to a single parameter (i.e. max

peak value of the UMTS signal). It seems that it rather depends on the overall TPC profile or more precisely on the

magnitude of the amplitude variations around the average value (dynamic range of the TPC) and the relative numberof occurrences (or frequency) of the high amplitude variations.

6 CONCLUSION

This report presents the results of CEPT studies to assess the performance of DVB-T receiver in terms of measured

carrier-to-interference protection ratios and overloading thresholds in the presence of interfering UMTS signal with

(for interference from the user equipment) and without (for interference from the base station) transmit power control.

The measurements described in this report were used to develop the channelling arrangements for the mobile services

in the band 790-862 MHz and the block edge mask applicable to the 790 MHz boundary (see CEPT reports 030 &

031 for details). Improvement in interfering transmitter ACLR values result in a slightly improved (decreased in thiscase) PR for the broadcasting service interfered with by UMTS signals in the 1st adjacent channel due to reduction of

out-of-band emission of the interfering transmitter.

Ten different DVB-T receivers (set-top boxes available on the market in 2008, can type tuners), which are consideredto be typical DVB-T receivers, have been tested against UMTS interference in a Gaussian channel environment.

Interference in co-channel, first adjacent channel and beyond has been considered. Values for the measured protectionratios and overloading thresholds have been statistically calculated at the 10

th, 50

thand 90

thpercentile for all the

receivers tested.

In general, protection ratios show a decrease in values (from -31 to -67 dB for the base station interference and from -

5 to -55 dB for the user equipment interference) as the frequency offset increases. However, the protection ratio in theimage channel is similar to the one in the third adjacent channel. The overloading threshold shows only small

variations with frequency offset.

At equal frequency offsets the impact of user equipment interference into DVB-T receiver is considerably higher than

the one from the base station, the effect being linked to the use of transmit power control. In particular, the latter

increases the required protection ratio by 12-26 dB and decreases the overloading threshold detected by 7-11 dB

depending on the frequency offset.

The results may be used by administrations seeking to protect their broadcasting services from interference generated

by UMTS services in the band 790-862 MHz.

6.1 Further studies

It is expected that LTE will be more widely deployed than WCDMA mobile service (UMTS) in the band 790-862

MHz. Therefore, measurements on LTE interference into DVB-T reception will need to be carried out in order toassess the impact of this on the broadcasting service.

First measurements on LTE BS and UE interference into DVB-T receivers indicate a general agreement with the

results presented in this report in static conditions. However, the dynamic conditions and the impact of the timevariation of the interfering signal need to be studied in more detail. Therefore, not all of the conclusions may be

transferred unchanged to the LTE case.

The results of these studies will be set out in a subsequent Report of ECC/TG4.


16/25


ANNEX A: PROTECTION RATIO MEASUREMENTS OF DVB-T INTERFERENCE INTO USB DVB-T

RECEIVERS

DVB-T USB receivers PR and Oth in the presence of a DVB-T interfering signal

(fw=778 MHz)

fi-fw (MHz)

Oth TV6_USB1

(dBm)

PR TV6_USB1

(dB)

Oth TV7_USB2

(dBm)

PR TV7_USB2

(dB)

-88 0 -48 -17 -52

-80 0 -48 -17 -52

-72 0 -48 -18 -50

-64 1 -48 -18 -50

-56 1 -48 -18 -50

-48 1 -48 -18 -51

-40 2 -48 -19 -50

-32 2 -48 -19 -50

-24 2 -48 -19 -49

-16 2 -48 -19 -39

-8 0 -30 -21 -27

0 NR 17 NR 17

8 0 -31 -21 -24

16 4 -47 -20 -4124 4 -52 -20 -49

32 4 -52 -19 -48

40 5 -51 -19 -49

48 5 -52 -20 -49

56 5 -52 -19 -49

64 5 -52 -20 -49

72 5 -52 -20 -49

80 5 -52 -20 -48

88 5 -54 -20 -48

NR: Oth is not reached. That is at this frequency offset PR is the predominant criterion. Consequently,

DVB-T receiver is interfered with by the interfering signal due to insufficient C/I (


17/25


ANNEX B: MEASUREMENTS ON PROTECTION OF DVB-T RECEIVERS INTERFERED WITH BY LTE

SIGNALS

1. Introduction

In addition to measurements of UMTS interference into DVB-T reception, being basis of the conclusions of this

report, initial measurements of LTE interference into DVB-T reception have been reported to ECC TG4. Thesemeasurements give a first impression of how DVB-T reception behaves in the presence of interference from LTE UE

and BS and how the results might differ from the findings regarding UMTS interference described in the main part ofthe report.

This annex describes the main results of these recent measurements. However, TG4 regards them as preliminary and

further investigations have to be performed in order to complement them to give a full picture of LTE interferenceinto DVB-T reception. This will be described in future in a separate report of ECC TG4.

2. Measurements by IRT

In these measurements the interfering effect of LTE Base Station (BS) and User Equipment (UE) signals into DVB-Treception has been investigated. Three DVB-T receivers were used in the measurements, two set top boxes and a

USB-stick type one. The blocking levels of one of the receivers were assessed. The interfering LTE signal was shaped

to correspond to the critical spectrum mask. A 5 MHz bandwidth was chosen. No TPC was applied for the LTE UEsignal.

The DVB-T signal transmission over a Gaussian, a static Rayleigh and a time-variant Rayleigh channel was

simulated. Protection ratios and overload thresholds for frequency offsets from -8 MHz to +72 MHz were determined.A 16QAM-2/3 modulation was chosen for DVB-T.

Tables B1 and B2 give the results for LTE UE and BS interference, respectively, for the Gaussian and the time-variant

Rayleigh case. For comparison, the values proposed by this report for UMTS interference are given in the lines

denoted by Deliverable D.

Frequency

offset

fi fw [MHz]

-8 0 8 16 24 32 40 48 56 64 72

Rx1 -27 23 -25 -37 -42 -51 -51 -50 -51 -53 -26

Rx2-19 20 -18 -45 -53 -66 -68 -70 -70 -71 -36

PR [dB]

Gaussian

channelRx3

-19 18 -19 -45 -46 -46 -46 -50 -47 -47 -47

Deliverable DGaussian

-22 13 -22 -42 -48 59 -67 -68 -72 - -53

Rx1-19 - -17 -31 -34 -47 -50 -48 -51 -52 -18

Rx2-12 25 -12 -38 -42 -51 -54 -60 -68 -62 -31

PR [dB]

time-variant

Rayleighchannel Rx3

- - - - - - - - - - -

Deliverable Dmobile

-16 19 -16 -36 -42 -53 -60 -62 -66 - -47

Table B1: PR values LTE UE (TPC off) into DVB-T 16QAM 2/3


18/25


Frequency offsetfi fw [MHz]

-8 0 8 16 24 32 40 48 56 64 72

Rx1(Can tuner)

-42 13 -42 -47 -49 -56 -55 -55 -56 -58 -54

Rx2(Can tuner)

-48 11 -47 -53 -57 -58 -57 -56 -58 -60 -51

PR [dB]

Gaussian

channelRx3

(Silicon tuner) -45 9 -44 -51 -52 -52 -53 -54 -56 -57 -57

Deliverable DGaussian

-36 12 -36 -46 -53 -62 -64 -69 -72 - -53

Rx1

(Can tuner)- - -33 -38 -40 -40 -47 -46 -48 -50 -33

Rx2(Can tuner)

- 18 -39 -45 -49 -43 -49 -48 -50 -53 -44

PR [dB]

time-variantRayleigh

channel Rx3(Silicon tuner)*

- - - - - - - - - - -

Deliverable D

Mobile-30 19 -30 -40 -47 -56 -63 -63 -66 - -47

Table B2:PR values LTE BS into DVB-T 16QAM 2/3

* this receiver has not been yet measured

For several frequency offsets the results show remarkable differences for the three receivers reflecting different

receiver implementation techniques.

The results also show that the LTE-UE signal interference to DVB-T is worse than the LTE-BS signal interference,due to the pulse nature of the LTE-UE signal.

For the two set-top box receivers the image frequency in not well filtered and the protection ratio in channel N+9 is

high compared to the values in the channels N+5 to N+8. The receiver 3 with silicon tuner (USB-stick) has no higher

protection ratio in channel N+9 than in the channels N+5 to N+8, but all protection ratio values are higher than for

receiver 1 and 2.

In general, the results for LTE UE and BS signals show conformity with the results obtained for the interfering effect

of UMTS signals into DVB-T reception.

Regarding LTE UE interference, for frequency offsets 0 MHz and 32 MHz and higher, the measurements give on

average a higher susceptibility of the DVB-T receivers as compared to the UMTS values, given in table 5. Withregard to LTE BS interference a similar behaviour is observed, however, not that prominent for the image channel

case, frequency offset 72 MHz. In the case of the small frequency offsets +-8 MHz the DVB-T receivers are even

more robust as compared to the UMTS values, given in table 4.

Frequency

offset

fi fw [MHz]

8 16 24 32 40 48 56 64 72

Gaussian -7 3 -20 -10 -7,5 -6 -5 -4 3

static

Rayleigh-7 3 -17 -14 -9 -6 -5 -5 -2

Deliverable D -2 -1 0 -1 -2 -1 -1 -1 0

Table B3: Oth values LTE UE into DVB-T 16QAM 2/3

Table B3 gives the results for DVB-T blocking thresholds (O th) caused by LTE UE interference. The measurementswere taken for one DVB-T receiver in a Gaussian and a static Rayleigh channel. Again, for comparison, the values

proposed by this report for UMTS interference are given in the lines denoted by Deliverable D.

The results are about the same for the Gaussian and the static Rayleigh channel. For frequency offsets 16, 24 and 32

MHz the receiver shows a strange behaviour which is still to be clarified. For the remaining offsets the measurements

give a higher susceptibility to LTE UE interference of 2 to 5 dB as compared to the results for UMTS, given in table5.


19/25


3. Measurements by MediaBroadcastMB carried out two measurement campaigns, a first on one nine different DVB-T receivers interfered with by SC-

FDMA-like signals without external time variation, and a second one on 4 other receivers interfered with by LTE UL-signals varying in the time domain.

In total, 13 different receivers were tested (five STB, five USB sticks, one USB box, one SCART-receiver, one

portable receiver).

DVB-T system parameters

The parameters used for the DVB-T signal are summarized in table B4. No live signal was used for the purpose of

these measurements.

Modulation Centre

frequency

(MHz)

Number

of

carriers

Channel

raster

(MHz)

Coding

rate

Propagation channels

COFDM-16-QAM

754, 762 or770

(CH 56-58)

8k mode 8 2/3 AWGN

Table B4: Parameters used for the (wanted) DVB-T signal

LTE system parameters

The LTE signal was simulated in the base band and up-converted or generated by an Arbitrary I/Q Wave Generator

using base band I/Q-sequences.

Transmission frequency 826 MHz 834 MHzBandwidth 4.32 MHz

Number of sub-carriers static case 288, dynamic case 12 288 sub-carriers

Number of Frames static case 18, dynamic case 1 23 active Radio Frames (1 in I1_, 23 inI2_) additional unused were inserted after both sequences

The LTE-signal was ideal, i.e. there were no measurable emissions within the frequency range of the wanted DVB-

T Signal (suppression of more than 85 dB). All results presented can be traced back to higher order intermodulation inthe receiving device and/or to interactions with receiver time-constants.

Signal structure (dynamic case)

The following signals I_NRF were used for measurements, with:

: type of LTE-signal:

1: one radio frame, 24 resource blocks (288 carriers, i.e. 4.32 MHz), 10ms long

2: 23 radio frames, in which only one resource block is occupied (frequency varies), 230ms long: number of added radio frames ("Null Radio Frames, NRF), where duration of one radio frame is 10 ms.

"0NRF" stands for no NRF added, i.e. signal without zero power.

Results - Static Case

The results for USB-type devices are summarized in Table B5, for the best and the worst receiver tested.3

3 Some administrations that planned for fixed outdoor roof top reception may not have an interest in the results of portable devices

including USB receivers.


20/25


DVB-T USB receivers PR and Oth in the presence of a DVB-T interfering signal

(fw=754 MHz)

fi-fw (MHz)

Oth best

(dBm)

PR best

(dB)

Oth worst

(dBm)

PR worst

(dB)

64 -4 -55 -22 -48

72 -6 -52 -22 -49

80 -4 -55 -22 -48

Note 1: PR is applicable unless the interfering signal level is above the corresponding

Oth. If the interfering signal level is above the corresponding Oth, the receiver isinterfered with by the interfering signal whatever the C/I is

Note 2: At wanted signal level close to receiver sensitivity, noise should be taken into

account, e.g. at sensitivity + 3dB, 3 dB should be added to the PR

Table B5: Protection Ratio SC-FDMA-like LTE Interference Measurements into USB DVB-T receivers

Results - Dynamic Case

First tests were carried out with different signals, e.g. in order to make sure that the measurement set-up is ok.; results

are shown in Fig. B1.

-70 dB

-60 dB

-50 dB

-40 dB

-30 dB

-20 dB

-10 dB

0 dB

10 dB

-100 dBm -80 dBm -60 dBm -40 dBm -20 dBm 0 dBm

DVB-T Rx Level in N+8

req.

PR

I1_0NRF

I2_0NRF

DVB-T

I2_10NRF

Figure B1: Protection ratio for different signals; interferer at N+8, I3 is a DVB-T signal and all others LTE

SC-FDMA signals; receiver Rx2.1

Figure B2 shows the behaviour of the same receiver in the presence of two different signals with different time

structures, as a difference to a constant signal (no NRF).


21/25


d_PR@N+8 for Rx DVB-T = -68 dBm

0

5

10

15

20

1 ms 10 ms 100 ms 1000 ms

Duration zero power in LTE

dPR

,zu

LTE

_v

1idea

l

I1_

I2_

Figure B2: Difference of two signals (different time structures) with a constant signal

Measurements of different receivers

Table B6: Overview of the results

The measured C/I-values in Table B6 are provided best signal (i.e. I1_0NRF) and another sequence for which thebehaviour was worse (worse signal).

The difference to a standard i.e. constant signal reaches 20 dB and more and has nothing to do with overloadingthreshold.

Receiver

C/I for

worst

sequence

Difference between

best and worst

sequence

C/I for

worst

sequence

Difference between

best and worst

sequence

[dB] [dB] [dB] [dB]

smalles difference -46,8 -6,5 -47,4 -4largest difference -17,4 -22,4 -27,4 -20,5

smalles difference -32,3 -3,6 -74,8 -2

largest difference -42,3 -6,1 -44,3 -9

smalles difference -4,8 -1,5

largest difference -18,3 -16

smalles difference -52,8 -1,6 -51,3 -1largest difference -27,3 -27 -27,3 -27

Channel N+9

Rx 2.1

Rx 2.2

Rx 2.3

Rx 2.4

Channel N+8


22/25


ANNEX C: CORRECTION FACTORS FOR PROTECTION RATIOS FOR PORTABLE AND MOBILE

DVB-T RECEPTION

Measurements on LTE UE interference into DVB-T reception carried out by the IRT show that for a time-variant

Rayleigh channel which is the relevant radio transmission channel for portable and mobile reception an increase of

the protection ratios of 7 to 9 dB is to be expected as compared to an Gaussian radio transmission channel. This is awell know behaviour, which can also be observed for the C/N values of the different DVB-T variants and for the

protection ratios for interference from other co- or adjacent channel DVB-T services.

The measurements were taken for a slowly time-varying Rayleigh channel. They are therefore particularly appropriate

for portable outdoor and indoor DVB-T reception. Two typical DVB-T set-top boxes have been investigated for

centre frequency offsets between -8 MHz and +72 MHz. Even if the absolute values of the protection ratios differ forsome frequency offsets, their relative difference between Gaussian and time-variant Rayleigh channel is

approximately constant. This leads to the conclusion that the results of the measurements are generally valid. The

bandwidth of the interfering IMT signal was taken to be 5 MHz.

The differences in protection ratios vary between 7 and 9 dB, apart from the 32 MHz frequency offset where anexceptional difference in protection ratios of 15 16 dB is found. For the image channel (72 MHz frequency off-set)

an extremely high value of 21 dB is observed for receiver 1 which is probably due to a particularly high susceptibility

of this receiver to image channel interference in the time-variant Rayleigh channel.

Difference of

centre frequency

fi - fw [MHz]

0 8 16 24 32 40 48 56 64 72

Rx1 - 9 9 9 16 8 9 8 8 21Difference [dB]

Gaussian time-variant Rayleigh

channel Rx2 7 8 8 8 15 8 8 8 7 7

i: interfering signal, w: wanted signal

Table C1: Difference of PR values for Gaussian and time-variant Rayleigh channel

for LTE BS interference into DVB-T 16QAM 2/3

Table 3 of the main section of this document gives correction factors for protection ratios for portable and mobile

DVB-T reception as compared to those for a Gaussian radio transmission channel. These differences vary for the

different DVB-T variants between 3.2 and 4.0 dB for portable reception and between 6.2 and 7.0 dB for mobilereception.

A comparison with the measurement results in table C1 shows that the correction factors of table 3 for mobile

reception are much more appropriate to describe the time-variant Rayleigh channel, i.e., also portable reception, thanthe figures given in table 3 for portable reception. Even an increase of 1 to 2 dB would be desirable.

It is therefore recommended if correction factors are to be taken from table 3 to use those for mobile reception also

for portable reception.


23/25


ANNEX D: TREATMENT OF OVERLOADING THRESHOLD

In general, to ensure protection within the small covered area (i.e. at 95 % of the locations) in the absence of receiver

overload, the median wanted field strength (EWmed) must exceed the median interfering field strength (EImed) as in the

following expression:

EWmed EImed+PR + (95%) (W2 + I2)

The last term in the preceding expression is the location correction factor, which takes into account the statistical

location variations of both the wanted and interfering signals (i.e. Wand I).

The i-th nuisance field,NIi, of any given interferer,Ii, is:NIi =EIimed+ PRi, whereEIimedis the median interfering field

strength of the i-th interferer, andPRiis the relevant protection ratio for the wanted signal with respect to the i-th

interferer.

Figure D14 displays different interference cases that may occur at any given reception point.

For an interfering signal,IU, which is less than the overloading threshold Oth, the maximum interfering signalIUmax,

for any given wanted signal level, CW, is:

IUmax = CW PR.

That is,IUI

Umaxto avoid interference. See Cases 1 and 2 in Figure D1.

However, when the resulting value ofIUmax is larger than Oth, the actual maximum interfering field strength is Oth Oth + PR

IU < Oth

CW

IUmaxPR

IUCW

IUmaxPR

IU

CW

PRIU

Oth Oth


25/25


ANNEX E: LIST OF REFERENCES

[1] CEPT Report 030 in response to the EC Mandate on The identification of common and minimal (least restrictive)technical conditions for 790-862 MHz for the digital dividend in the European Union

[2] CEPT Report 031 the EC European Commission in response to the Mandate on Frequency (channelling)

arrangements for the 790-862 MHz band (Task 2 of the 2nd Mandate to CEPT on the digital dividend)

[3] ITU-R Recommendation V.573-5: Radiocommunication vocabulary (www.itu.int)[4] TS 125 101: Universal Mobile Telecommunications System (UMTS); User Equipment (UE) radio transmission

and reception (FDD) (www.etsi.org)

[5] TS 125 104: Universal Mobile Telecommunications System (UMTS); Base Station (BS) radio transmission and

reception (FDD) (www.etsi.org)

______________

Ecc Report 138 Measurements on the Performance of Dvb-t Receivers ...

Documents

Transcript of Ecc Report 138 Measurements on the Performance of Dvb-t Receivers ...