DVB-T/T2 signal parameters measurement, generation of 3D TV transport stream

Transcription

1 Digital Television and Radio Systems (NDTV) Laboratory Exercise no. 4 DVB-T/T2 signal parameters measurement, generation of 3D TV transport stream The purpose of this laboratory task is to familiarize with measurement receiver R&S ETL TV Analyzer and DVB-T signal parameters measurement, which is come from DVB-T networks (multiplexes) 1 and 2. You should get basic idea about transport stream MPEG-2 TS content, about spectrum of received digital television signal, about constellation diagram of inner modulation, about signal BER, about S/N ratio in channel and parameters of coding and broadcasting in 1 st and 2 nd multiplexes. Orthogonal Frequency Division Multiplex (OFDM) is the representative of Multi Carrier Modulation (MCM). In combination with Forward Error Correction (FEC) in the baseband is called as COFDM (Coded OFDM). It is characterized by high immunity against Inter-symbol interferences (ISI), which occur due to multi-path propagation (reflection from barriers). Reflected signals has on receive site various time delays and amplitudes, most probably in range from units to hundreds of µs. The OFDM subcarriers are transmitted simultaneously with inner M-QAM or QPSK modulation. The subcarriers spectrum are overlap each other such a way that the minimum of power spectrum of one subcarrier overlaps the maximum of neighbor one. Measurement receiver R&S ETL TV Analyzer is digital receiver with inbuilt monitor, which manages to measure except digital and analog channels signal level, also a detail DVB- T/T2 signal quality evaluation. The modularity of R&S ETL measure system allows the upgrade it to digital satellite and cable measurement by another modules application. Integrated TFT display allows to evaluation of received video broadcasting. There are included various detectors (peak detector, mean, minimal and maximal value detectors). The correction curves, which are saved in EEPROM after calibration allow high accuracy of measurement. Today is digital terrestrial television broadcasting DVB-T provides by networks (multiplexes) 1 (channel 25th, 506 MHz), 2 (channel 40th, 626 MHz), 3 (channel 59th, 778 MHz) a 4 (channel 64th, 818 MHz). Their parameters are in Tab

2 Tab. 4.1: Technical parameters of DVB-T broadcasting networks (multiplexes) 1 to 4 in Brno (source DVB-T Network 1 (channel 29th, 538 MHz) ČT1, ČT2, ČT24, ČT4 Sport Barvičova Hády V 16 34'47" 49 11'56" H 16 40'28" 49 13'22" OFDM guard interval 1/4 19,10 Mbit/s DVB-T Network 2 (channel 40th, 626 MHz) Nova, Prima, Barrandov, Cool, Nova Cinema H 16 40'28" 49 13'22" Hády V 16 34'47" 49 11'56" Barvičova DVB-T Network 3 (channel 59th, 778 MHz) Z1, Public TV Hády H 16 40'28" 49 13'22" V 16 34'47" 49 11'56" Barvičova DVB-T Network 4 (channel 64th, 818 MHz) ČT1, Nova HD, O2 Info, Očko FN Bohunice H 16 34'14" 49 10'33" OFDM guard interval 1/4 19,10 Mbit/s OFDM guard interval 1/4 19,10 Mbit/s OFDM guard interval 1/8 22,17 Mbit/s Measurement tasks and procedure 1. Familiarize yourself with the digital television receiver STB Icecrypt STC6000HD PVR and with television display TVP functionalities. STB is connected to the TVP input via HDMI 2 interface. Familiarize yourself also with measurement analyzer ETL. Manuals are attached

3 2. Tune signal of 1st and 2nd multiplex signals on STB receiver (channel 29 th, 538 MHz and channel 40 th, 626 MHz). Save found television and radio programs to the preselection memory of STB. Check the signal quality by the inbuilt detectors of level and quality in [%]. Note the values for both broadcasting networks. Procedure: Menu Instalace Hledání terestriálu (OK) - Mód hledání (Ručně) - Program (40) - Kmitočet (626 MHz) Vyhledat Uložit. 3. Tune the measurement receiver ETL on signal of 2 nd multiplex (channel 40 th, 626 MHz). Try tuning channel by channel and continuously. Measure the signal level in [dbµv]. Procedure: Push the button MEAS < > Digital TV Settings swirch TV Standard to OFDM DVB-T/H. Than pres the button FREQ and set the frequency of C40 channel (626 MHz). Press the button MEAS < > Overview - Level. 4. Display the program content of transport stream MPEG-2 TS of 2 nd multiplex on the screen of measure receiver ETL (TV and radio programs). Note the identificators in MPEG-2 TS and used compress type MPEG. Packet identifiers of MPEG-2 TS are Video-PID and Audio-PID. Procedure: Press the button Mode and chose the option TS Analyzer (wait for analyzer start) press the button and choice the option Topology you can see transport stream content and individual programs streams on the screen of 2 nd multiplex. Press the button and choice the option AV Decoder you can see PIDs: Video-PID, Audio-PID choice the option Decoder Info to display the compression type MPEG (Video and Audio). Than switch off the analyzer TS Analyzer: File < > Exit (wait for switching off). 5. Display the spectrum of arbitrary channel of digital television on the screen of ETL. Measure mean level of received signal in [dbµv] by the cursors. Than measure the crosstalk to the neighborhood channel from spectral mask in [db]. Procedure: Press the button Measure Spectrum. SPAN 10 MHz MKR change by rotary selector (the scale on the screen - min dbµv). 6. Display the constellation diagram of inner M-QAM. Zoom on the detail of one quadrant of the diagram. Measure BER before and after Viterbi decoder and S/N in [db]. Display also other information about 2 nd multiplex broadcasting parameters (OFDM mode, inner modulation scheme, code rate, guard interval, hierarchical modulation, channel number, frequency). Procedure: Press the button MEAS Modulation Analysis Const Diagram - Zoom 1st/2nd/3rd/4th/none quadrant choice (display the detail of one constellation diagram quadrant). Information about broadcasting parameters in 2 nd multiplex you can display easily: press MEAS < > Overview. 7. Disconnect the measurement receiver ETL from the central cable distribution and connect it to the shorted dipole antenna ANT. Try to display the impulse response (press the button MEAS Channel Analysis / Echo Pattern) and display the reflection signals (channel 40 th, 626 MHz). The scale of abscissa could be switched to the distance or time lag. You can read relative loss of delayed signals [db], delay in [µs] and distance in [km] by using markers (< > marker)

4 8. Reconnect ETL back to the centralized cable distribution and erase all the preselections. Switch ETL back to the mode of DVB-T digital television measurement and tune the 2 nd multiplex. Voluntary experimental task 9. Use the laboratory transmitter SFU and analyzer ETL to experimental verification of television receive availability in case of worsening conditions of C/N and in the fading channels. Match your results with table Annex A.1 in standard ETSI EN V1.6.1 ( ). Set the parameters of DVB-T broadcasting: channel C58 (770 MHz); Level 70 dbuv, 8K mode, inner modulation 64QAM, code rate 2/3; guard interval 1/8. Vary the values of C/N. Note the results in channels: AWGN, RC20 and RL Set the parameters of DVB-T: channel C58 (770 MHz); Level 70 dbuv, 8K mode, inner modulation 64QAM, code rate 2/3; guard interval 1/8. Vary the values of C/N. Note the results in channels: AWGN, RC20 and RL20. Setting procedure of SFU: Press the button Setup FAVORITIES - FREQUENCY TX:FREQUENCY: FREQUENCY (set 770 MHZ) - TX:LEVEL: LEVEL (set 70 dbµv). Use the rotary selector (you can use also mouse) to set other parameters: MODULATION MODULATION TRANSMISSION STANDARD (zadejte DVB- T/H). DIGITAL TV CODING FFT SIZE (set 8K); GUARD INTERVAL (set 1/8); HIERARCHY (set NON-HIERARCHICAL); CONSTELLATION (set 64QAM); CODE RATE (set 2/3). NOISE NOISE (set ADD); AWGN (switch to ON); AWGN C/N (vary the value from 10 to 40 db). FADING FADING (switch to ON); PROFILE STANDARD (select DVB); PARAMETER SET (select first RC20 ANX B and than RL20 ANX B). 11. Use the laboratory transmitter SFU and analyzer ETL to experimental verification of DVB-T2 television receive availability in case of worsening conditions of C/N and in the fading channels. Match your results with table Tab. 45 of standard ETSI TS V1.2.1 ( Set the parameters of DVB-T2 broadcasting: channel C58 (770 MHz); Level 70 dbuv, 32K (extended) mode, inner modulation 256QAM, code rate 3/5; guard interval 1/16. Vary the values of C/N. Note the results in channels: AWGN, RC20 and RL Setting procedure of SFU: Press the button Setup FAVORITIES - FREQUENCY TX:FREQUENCY: FREQUENCY (set 770 MHZ) - TX:LEVEL: LEVEL (set 70 dbµv). Use the rotary selector (you can use also mouse) to set other parameters: MODULATION MODULATION TRANSMISSION STANDARD (set DVB-T2). DIGITAL TV BICM FEC FRAME (Normal); CODE RATE (set 3/5); CONSTELLATION (set 256QAM); CONSTELL. ROTATION (on/off); - 4 -

5 FRAMING+OFDM - FFT SIZE (set 8K); GUARD INTERVAL (set 1/16); PILOT PATTERN (chose PP4). NOISE NOISE (switch to ADD); AWGN (switch to ON); AWGN C/N (vary the value from 10 to 40 db). FADING FADING (switch to ON); PROFILE STANDARD (choice DVB); PARAMETER SET (select first RC20 ANX B and than RL20 ANX B). 13. Use SFU laboratory transmitter to broadcast transport stream of 3D television in DVB-T2 standard. Transport streams samples with video streams in Frame Compatible format (FC) are located in folder e:/. The video is compressed both MPEG-2 and MPEG-4 AVC, with variable data rate levels Find the differences in Quality of Experience (QoE) among used compress algorithms and data rates, both in 3D video mode and 2D mode (switch off by the button 3D on TVP remote controller). Set the highest data rate (29 Mbit/s). Increase the noise level in the channel, till the Cliff falls effect occurs. Observe the depth perception breakdown before complete signal lose. Fig. 4.1: Transport stream generator in SFU

6 Used laboratory facilities STB digital television receiver DVB DVB-T/T2 Icecrypt STC6000HD + RC TVP television receiver LG + remote controller ETL broadcasting analyzer R&S ETL-K202 TV Analyzer SFU laboratory transmitter DVB-T/T2 R&S SFU Broadcast Test System ANT shortened inner dipole antenna for DVB-T Technisat Connection cable 3 x BNC-BNC, 1 x BNC antenna, 2 x T reduction BNC, HDMI Fig. 4.2: Laboratory workplace Task 4 Conclusion Each student gives here individual measurement evaluation and confirms it by his signature. You have to comment each measurement step in detail, all of outcomes and measured characteristic. Individual conclusion should also contain major technical knowledge from measurement. Used and recommended literature [1] Fischer, W. Digital Television. A practical Guide for Engineers. Springer, [2] Legíň, M. Televizní technika DVB-T. BEN technická literatura, Praha, [3] Bednář, J., Gregora, P. Příjem DVB-T. BEN technická literatura, Praha, [4] Digitální televizní vysílání DVB-T. Mapa pokrytí a odborné informace k příjmu signálu sítí 1 až 4, Internet Info s.r.o. 2009, ISSN ISSN , online dostupné na adrese < -6-