Digital Television Broadcasting Systems Testing in Brazil

Transcription

1 Digital Television Broadcasting Systems Testing in Brazil Kiev, Ukraine November 2000 Interregional Seminar on the Transition from SECAM to Digital TV Broadcasting Renato Maroja - maroja@cpqd.com.br Fundação CPqD - Campinas - SP - Brazil 1

2 Organization of the tests Entities and roles ANATEL - National Agency of Telecommunications - Brazilian regulating authority Conducts the process of defining a DTV standard for Brazil Authorized (after a public consultation) the realization of the field tests Contracted CPqD as consultant in the process Will define the DTV standard based on the tests results and other technical and non-technical aspects SET - (Brazilian) Society of Television Engineering ABERT - Brazilian Association of Radio and Television Broadcasters SET/ABERT studies the evolution of DTV standards since 1994, and has structured task groups to carry on the tests Makes planning studies to consider digital channels along with analog channels Technological agreement with Instituto Mackenzie - Human resources Instituto Mackenzie - a Brazilian private University, in São Paulo Tests methodologies Acquired test equipment, set up the laboratory and field tests installations Executed the tests and reported the results to ANATEL, together with SET/ABERT 2

3 Organization of the tests Entities and roles (cont) CPqD - Private foundation with expertise in Telecommunications support in systems aspects - CPqD works in multiple areas in telecommunications analysis and consolidation of the laboratory tests methodology development of ambiences for systems simulations analysis and consolidation of the field tests methodology checking and support in the laboratory and field tests development of tools for planning studies analysis of the tests results advice on other aspects of the introduction of Digital TV in Brazil ~1100 employees m2 3

4 Laboratory and Field Tests Tests objectives: Compare terrestrial DTV systems with respect to the transmission layer Laboratory Tests - robustness/capacity analysis of the systems under controlled conditions Interference - A to D, D to A, D to D, CW and FM: planning Robustness to impulsive noise Multipath performance static, single and multiple echoes dynamic, Doppler shift, mobility BER x C/N performance in white noise (AWGN) - modulation, planning, transmitter power 4

5 Interference: Protection Ratios D/U = Desired/Undesired Signal power ratio (db) Lower ratios more robustness Digital into Analogue (*) ATSC DVB - 2K DVB - 8K ISDB Co-channel Upper adjacent Lower adjacent Analogue into Digital ATSC DVB - 2K DVB - 8K ISDB Co-channel Upper adjacent Lower adjacent Digital into Digital ATSC DVB - 2K DVB - 8K ISDB Co-channel Upper adjacent Lower adjacent (*) CCIR 4: 37,5 db Taboo channels interference: irrelevant 5

6 Robusteness to Impulsive Noise Digital signal + gated Noise C/Neq Gate: 30s cycle, 12,5 Hz to 100 Hz, fixed T W BER < 3 x 10-6 within 2 minutes counting C/ Ne q (d B) C/Neq(dB) ,0 100,0 200,0 300,0 400,0 500,0 600,0 700,0 800,0 900,0 Window (ms) ATSC - Zenith ATSC - Chip T ATSC - Chip S ATSC - Chip A DVB 3/4 1/16 2K DVB 3/4 1/16 8K DVB 3/4 1/8 2K DVB 2/3 1/32 8K DVB - Chip N - 3/4 1/16 2K DVB - Chip N - 2/3 1/32 8K DVB - Chip M - 2/3 1/32 8K DVB - Chip L 2/3 1/32 8k DVB - Chip L 3/4 1/16 8k ISDB 3/4 1/16 4K INT4 ISDB - Chip J 6

7 Multipath - single static echo t G = 74 ms Gráfico : Relação entre o atraso e a relação eco-sinal para taxa de erro de limiar E/C (db) ATSC ATSC - Chip S DVB 3/4 1/16 2K DVB - Chip M - 3/4 1/16 8K DVB - Chip M - 2/3 1/32 8K ISDB 3/4 1/16 4K 0,1s ISDB - Chip J Atraso (em us) Echo delay (ms) 7

8 C/N degradation with single echo Increased echo amplitude requires higher C/N (imposes penalty) DVB-T and ISDB demodulators showed evolution along the tests COFDM: guard interval ATSCcannot stand strong echoes: ~2 db with high penalties 8VSB: (long, complex) transversal equalizers t G = 18,7 ms C/N (db) 8

9 BER x C/N performance BER = 3 x 10-6 ATSC Zenith: 14.5 db DVB-T chip M 2/3 1/32 8K: 16.9 LOP DVB-T NDS 3/4 1/8 2K: 18.8 db ISDB-T DiBEG 3/4 1/16 2K/4K/8K: 18.5 db COFDM: robustness x payload Better - Worse 9

10 Field Tests Field tests - robustness/capacity analysis under real reception conditions Coverage - real world reception includes white noise, multipath, interference from other channels and impulsive noise Gap filler - recover coverage on a shadowed spot Indoor reception - high attenuation and time varying multipath Mobility - Doppler frequency shift - some trajects in São Paulo, near the transmitter 10

11 Field Tests - TX Site São Paulo Biggest market in Brazil: 40% GNP Economical potential "Acid test": difficult coverage Topographic conditions - gap filler High density of buildings in some regions UHF channel 34 (593 Hz center frequency) TX station Site definition for TV Cultura tower: coverage, infrastructure and space for equipments and for antenna in tower Transmitter: Harris DCD20PL1, operated at 2,5 KW for all systems Antenna: 104 m agl; 9.3 dbd; 12 KW max. ERP 11

12 Field Tests - RX Site RX Van mast 10 m agl Antenna: Scaffner, 2.6 dbd Pre-amplifier, hybrids Noise Generator Receivers - availability MPEG 3 Decoder Spectrum Analyzer Measurement period: Nov 9, 1999 to Abril 28,

13 RX Test sites in São Paulo Measurement Procedure Point RX antenna to obtain best reception Measure received C = -30 dbm Add external noise up to BER Threshold or artifacts; Calculate available margin, electric field, etc C = Signal Power N = Noise power in channel bandwidth C/N = Signal to noise ratio Measured points 17 radials 15 o apart distances: 3, 6, 9, 12, 15, 20, 25, 30, 40 Km 13

14 Field Tests - Coverage 127 test points: ATSC and DVB-T 2K Criterion: Margin > 0 db III Percentual de Recepção - Gráfico por Distância Critério: Margem > 0 100% 90% Percentage Percentual de Sites of sites 80% 70% 60% 50% 40% 30% 20% 10% 0% Distance Distância (km) (Km) ATSC DVB - 8k DVB - 2k ISDB - 4k 14

15 Field Tests - Coverage 127 test points: ATSC and DVB-T 2K Criterion: Margin > 0 db III Percentual de Recepção - Função Cumulativa Crtério: Margem > 0 100% Percentage Percentual de Site of sites 90% 80% 70% 60% Distance Distância (km) (Km) ATSC DVB - 2k DVB - 8k ISDB - 4k Canal VHF-Alto/Analog. 3 a 5 Canal VHF-Alto/Analog. 2 a 5 15

16 Field Tests - Coverage 27 test points: ATSC, DVB-T 2K, III Percentual de Recepção - Gráfico por Distância - 27 Pontos Simutâneos Critério: Margem > 0 Criterion: Margin > 0 db 100% 90% Percentage Percentual de Site of sites 80% 70% 60% 50% 40% 30% 20% 10% 0% Distance Distância (km) (Km) ATSC DVB 8K 2/3 1/32 DVB 8K 3/4 1/16 DVB 2K 3/4 1/16 ISDB 4K 3/4 1/16 16

17 Field Tests - Coverage III Percentual de Recepção - Função Cumulativa - 27 Pontos Simutâneos Critério: Margem > 0 Criterion: Margin > 0 db 100% Percentage Percentual de Sites of sites 90% 80% 70% 60% 50% 40% 30% Distance Distância (km) (Km) ATSC DVB 8K 2/3 1/32 DVB 2K 3/4 1/16 DVB 8K 3/4 1/16 ISDB 4K 3/4 1/16 17

18 Gap filler measurement sites GAP FILLER LOCALIZAÇÃO DOS PONTOS DE MEDIDAS 500m 1000m 1500m 2000m 2500m 3000m m 2000m Gap filler Radiation pattern Tilted beam m 1000m 500m m m m m 3000m Actuation Superposition Out of range PONTOS DE ATUAÇÃO DO GAP FILLER PONTOS DE SOBREPOSIÇÃO DE SINAIS DA ESTAÇÃO PRINCIPAL E O GAP FILLER PONTOS FORA DA AREA DE ATUAÇÃO DO GAP FILLER 3500m 18

19 Outdoor Reception - Gap Filler Improvement of reception with gap filler Antenna is re-oriented with gap filler on/off Distance from main transmitter ~5,6 Km -> ~19 ms 100% 90% 80% 70% 77% Actuation region 77% 85% 100% 100% 100% 90% 80% 70% Superposition region 82% 82% 73% 91% 60% 60% 50% 50% 45% 40% 40% 30% 23% 30% 27% 20% 10% 0% OFF ATSC DVB-8K ISDB-8K 20% 10% 0% ON OFF ATSC DVB-8K ISDB-8K ON 19

20 Indoor Reception 12 sites where the 3 systems were tested under identical conditions Indoor antenna: UHF log-periodic - Silver Sensor Percentage of good reception Normal Blender On People walking around near antenna 20

21 SET/ABERT Reports The data, tables and graphs presented here were extracted mainly from the SET/ABERT Final Report - Part 2, that is available in Portuguese and in English at: These results express the conclusions arrived at by SET/ABERT, and do no express ANATEL's viewpoint. Thank you for your attention 21