RESULTS OF THE LABORATORY EVALUATION OF AN 8 MHz ADTB-T TELEVISION SYSTEM FOR TERRESTRIAL BROADCASTING FINAL REPORT (VERSION 3.

Transcription

1 RESULTS OF THE LABORATORY EVALUATION OF AN 8 MHz ADTB-T TELEVISION SYSTEM FOR TERRESTRIAL BROADCASTING FINAL REPORT (VERSION 3.0) Prepared by the COMMUNICATIONS RESEARCH CENTRE CANADA For HDTV TEEG CHINA January 15, 2003

2 EXECUTIVE SUMMARY The Communications Research Centre Canada (CRC) carried out laboratory tests to evaluate the performance of a prototype 8 MHz Advanced Digital Television Broadcasting (ADTB-T) terrestrial transmission system for HDTV TEEG China. The main results from the laboratory tests are summarized below: 1. The 8 MHz ADTB-T system payload data rate is Mbps. The AWGN channel threshold is 10.5 db (BER = 3E-6). 2. The ADTB-T system implemented an excellent RF front-end. With a consumer grade single conversion tuner, it has more than 90 db input dynamic range and should have good adjacent channel interference rejection capability. 3. The ADTB-T system can withstand: A -6 db single echo within a delay range between to µs. A -3 db single echo within a delay range between to µs. A 0 db single echo over a 30 µs range (Since there are two equal amplitude signals, time reference can not be selected). 4. The ADTB-T system has an impressive dynamic multipath performance: For -1 µs delay and -3 db amplitude single echo, the system can tolerate 340 Hz Doppler shift. For +1 µs, -3 db single echo, the Doppler rate is 630 Hz. For - 9 and +9 µs, -3 db single echo, the Doppler rates are 195 Hz and 270 Hz, respectively. 5. The ADTB-T system can survive CRC#4 multipath profile with 0 db echo power. 2

3 Table of Contents EXECUTIVE SUMMARY Introduction Description of the ADTB-T prototype receiver Laboratory set-up Transmitter Channel Receiver Test conditions Test Procedures and results Susceptibility to Random Noise Input RF Dynamic Range Susceptibility to Burst Noise Susceptibility to Random Noise in the Presence of Static Multipath Ensembles Susceptibility to Single Static Echoes Susceptibility to Strongest Static Echoes Susceptibility to Single Dynamic Echoes at Varying Doppler Rates Susceptibility to Dynamic Echoes in the Presence of Random Noise Susceptibility to Single Dynamic Echoes at various Delays and Doppler Rates Receiver Equalizer Range Single Echo Pair Echoes Phase noise impairment Conclusion APPENDIX A

4 1 Introduction The Advanced Digital Television Broadcasting Terrestrial (ADTB-T) transmission system was designed by the HDTV Technical Executive Expert Group (TEEG) of China. The prototype system was jointly developed by the Shanghai Jiaotong University, Shanghia Chinips Technologies Co., Ltd., and LINX Electronics Inc. This ADTB-T system was evaluated in the laboratory of the Communications Research Centre Canada (CRC) against random noise, burst noise, phase noise and multipath impairments. This report outlines the results of these laboratory evaluations. The tests were carried out in January

5 2 Description of the ADTB-T prototype receiver The ADTB-T receiver is a prototype receiver designed to handle the severe multipath conditions and fast Doppler shift that can often be encountered in the field during mobile reception. The front end consists of a single conversion consumer grade tuner and a 10- bit A/D. A robust synchronization circuit drives an NCO to lock the carrier frequency and an external VCXO for sampling clock generation. It is designed to operate under severe channel degradation, and fast Doppler conditions. The equalizer has a unique configuration that enables proper equalization of strong ghosts while minimizing noise enhancement. The equalizer is also designed to have sufficient length and speed to handle the complex ensembles that exist in indoor, outdoor and mobile environments. The receiver also has a phase tracker for correcting high frequency phase noise from the tuner, as well as the deinterleaver, and Reed-Solomon decoder for error correction. The system is implemented with an FPGA circuit board encased in a 19 inch rack mount. The 8 MHz ADTB-T system payload data rate was Mbps in the transmission mode used for these tests. 5

6 3 Laboratory set-up The ADTB-T system is tested against impairments. The impairments are random noise, burst noise and phase noise, as well as multipath distortion with and without noise injection. The laboratory set-up for the evaluation of the ADTB-T system is presented in Figure 1. The set-up is divided in three sections: Transmitter, Channel and Receiver. 3.1 Transmitter The DTV signal is obtained from the ADTB-T modulator. The test sequence is the ADTB-T modulator internal PRBS data generator (pn-23). The IF signal of the ADTB-T modulator is connected to the up-converter to obtained an RF signal on China channel 39 ( MHz). 3.2 Channel A Micronetics NOD-5250 generator is used to generate the random noise. The generator is connected to the combiner along with the desired DTV signal. A controlled gated noise is used with the noise generator to generate the burst noise. A controlled phase noise is use with the noise generator to generate phase noise at the up-converter. An HP89440A vector analyzer is used to calibrate the RF system. A TAS 4500 FLEX channel simulator is used to simulate multipath distortion. multipath profile details can be found in Appendix A. The 3.3 Receiver The output signal from the combiner is connected to the ADTB-T receiver. The output of the ADTB-T receiver is connected to an HP 3784A Bit Error Rate (BER) meter. The BER is used as reference measurement to determine the Threshold of Visibility (TOV) level, which is defined as a BER = 3E Test conditions The tests are done on China channel 39 ( MHz). BER tests are conducted. The TOV level is defined as BER = 3E-6. For the measurement in the case of Multipath, the signal power refers to the main signal power. In the case of C+I/N, the echo power is included i.e., C+I indicates total received signal power (main signal and echoes). 6

7 Without noise injection the TAS 4500 FLEX channel simulator has a of 37 db. Multipath profile details are listed in Appendix A. center of the RF channel. Echo phases are referenced to the The tests are conducted with and without signal re-acquisition. In this report With Re-acquisition (w. re-acq.) means: Disconnect the RF signal and re-acquire the signal to find the TOV level, where the receiver can re-acquire the signal with the maximum impairment or interference. In this report Without Re-acquisition (w/o. re-acq.) means: Find the TOV level with the maximum impairment or interference without reacquiring the signal. An HP89440A vector signal analyzer is connected at the combiner output, to make the average power measurements of the DTV and random noise signals. 7

8 Transmitter Channel Receiver * ADTB-T Modulator with internal PRBS data Random Noise Generator Micronetics PNG 5200 Directional Coupler UP * Converter Phase Noise Controlled Gated Noise Controlled Channel Simulator TAS 4500 FLEX Combiner Vector Analyzer HP 89440A ADTB-T Receiver BER Meter HP 3784A * * Provided by Shanghai Jiaotong University, Shanghai Chinips Technologies Co., Ltd and LINX Electronics Inc. Figure 1. Set-up for the Laboratory Evaluation of the ADTB-T system. 8

9 4 Test Procedures and results The following procedures were intended to verify the performance of the ADTB-T television system. The tests included measurements on: -Random noise -Dynamic Range -Burst noise -Multipath Ensembles -Single Echo -Phase noise 4.1 Susceptibility to Random Noise The purpose of these tests is to determine the robustness of the ADTB-T television system to random noise impairment. The DTV desired signal is adjusted at three different RF levels: Strong (-28 dbm), Moderate (-53 dbm) and Weak (-68 dbm). The noise level is increased until TOV is reached and the value is recorded. Level w/o. re-acq w. re-acq Strong Moderate Weak Table 1. Susceptibility to Random Noise 4.2 Input RF Dynamic Range The ability of the ADTB-T television system to receive very strong and very weak signal is tested. The maximum and minimum RF signal level is determined by increasing and decreasing respectively the RF power signal level at the receiver s input until the TOV level is reached. Minimum RF Level (dbm) Maximum RF Level (dbm) w/o. re-acq w. re-acq w/o. re-acq w. re-acq > 5.5* > 5.5* *: This is the maximum power, which was available from the test bed. Table 2. Maximum and minimum RF signal level 9

10 4.3 Susceptibility to Burst Noise The purpose of this test is to determine the robustness of the ADTB-T television system to gated random noise impairment. The DTV desired signal is adjusted to the Moderate level (-53 dbm). The gated noise level is adjusted for a of 5 db (-58 dbm). The pulse width is increased until TOV is reached and the pulse width is measured and recorded for a pulse rate of 10 and 1 Hz. Level Pulse Rate (Hz) Pulse Width (µs) Moderate Moderate Table 3. Susceptibility to Burst Noise with Re-acquisition 4.4 Susceptibility to Random Noise in the Presence of Static Multipath Ensembles The purpose of the multipath testing is to determine how robust is the ADTB-T television system in the presence of static multipath ensembles with random noise injection. The at TOV is recorded for each multipath ensemble. All the multipath tests are done with the desired DTV signal RF level adjusted to the Moderate level (-53 dbm). Level Ensemble Type C+I/N Moderate Calibration 10.5 N/A Moderate Brazil A Moderate Brazil B Moderate Brazil C Moderate Brazil C* Moderate Brazil D Moderate Brazil E Moderate China Moderate China Moderate China Moderate China Moderate China Moderate China Moderate China Moderate China 8** Moderate China Moderate China *: The phase of paths 1,4 and 5 is change to 180 to create a notch in the center of the RF channel. **: The amplitude of the path 6 (30 µs) is change from 0 db to 0.3 db as the ADTB-T system is not working with the original ensemble China 8. Table 4. Susceptibility to Random Noise in Presence of Static Multipath Ensembles with Re-acquisition 10

11 4.5 Susceptibility to Single Static Echoes The purpose of the multipath testing is to determine how robust is the ADTB-T television system in the presence of a single static echo with random noise injection. The echo power level at TOV is recorded for each scenario of single echo power and delay. All the multipath tests are done with the desired DTV signal RF level adjusted to the Moderate level (-53 dbm). Level Echo Delay (µs) Doppler Rate (Hz) Echo Power Moderate Moderate * Moderate * Moderate * Moderate * Moderate * Moderate * Moderate * Moderate * Moderate * Moderate * Moderate * Moderate * Moderate * Moderate * Moderate * Moderate * Moderate * Moderate * Moderate * Moderate * Moderate * Moderate Moderate Moderate *: No errors were observed even with maximum multipath injection (0 db). Table 5. Susceptibility to Single Static Echo in Presence of Random Noise with Re-acquisition 11

12 4.6 Susceptibility to Strongest Static Echoes The purpose of the multipath testing is to determine how robust is the ADTB-T television system in the presence of a strong static echo in static multipath ensembles with and without random noise injection. The echo power level at TOV is recorded for each multipath ensemble without noise injection. If the receiver can handle a 0 db echo without any errors, the is recorded for TOV with noise injection. The C+I/N is calculated and recorded. All the multipath tests are done with the desired DTV signal RF level adjusted to the Moderate level (-53 dbm). Level Ensemble Type Echo Power C+I/N Moderate Calibration N/A 10.5 N/A Moderate Modified Brazil C 0* Moderate Modified Brazil D 0* Moderate Special Brazil C N/A *: No errors were observed even with maximum multipath injection (0 db). Table 6. Susceptibility to Strongest Static Echoes with Re-acquisition 4.7 Susceptibility to Single Dynamic Echoes at Varying Doppler Rates The purpose of the multipath testing is to determine how robust is the ADTB-T television system in the presence of a single dynamic echo at varying Doppler rates with random noise injection. The Doppler rate at TOV is recorded for each scenario of single echo power and delay. All the multipath tests are done with the desired DTV signal RF level adjusted to the Moderate level (-53 dbm). Level Echo Delay (µs) Echo Power Doppler Rate (Hz) w/o. re-acq. w. re-acq. Moderate Moderate Moderate Moderate Moderate Moderate Moderate Moderate Moderate Moderate Moderate Not Working Not Working Moderate China > 1000* > 1000* *: This is the maximum Doppler rate, which was available from the test bed. Table 7. Susceptibility to Single Dynamic Echoes at Varying Doppler Rates 12

13 4.8 Susceptibility to Dynamic Echoes in the Presence of Random Noise The purpose of the multipath testing is to determine how robust is the ADTB-T television system in the presence of a dynamic echo in static multipath ensembles with random noise injection. The echo power level at TOV is recorded for each multipath ensemble. All the multipath tests are done with the desired DTV signal RF level adjusted to the Moderate level (-53 dbm). Level Ensemble Type Doppler Rate (Hz) Echo Power Moderate ATTC Dynamic * Moderate ATTC Dynamic * Moderate ATTC Dynamic * Moderate ATTC Dynamic * Moderate ATTC Dynamic * Moderate ATTC Dynamic Moderate ATTC Dynamic * Moderate ATTC Dynamic * Moderate ATTC Dynamic * Moderate ATTC Dynamic * Moderate ATTC Dynamic * Moderate ATTC Dynamic Moderate China * Moderate China * Moderate China * Moderate China * *: No errors were observed even with maximum multipath injection (0 db). Table 8. Susceptibility to Dynamic Echoes in Presence of Random Noise with Re-acquisition In the next Table, the echo power level at TOV is recorded for each multipath ensemble without noise injection. If the receiver can handle a 0 db echo without any errors, the is recorded for TOV with noise injection. The C+I/N is calculated and recorded. Level Ensemble Type Doppler Rate (Hz) Echo Power C+I/N Moderate Calibration N/A N/A 10.6 N/A Moderate CRC #1 1 0* Moderate CRC #1 5 0* Moderate CRC #2 1 0* Moderate CRC #2 5 0* Moderate CRC #3 1 0* Moderate CRC #3 5 0* Moderate CRC #4 1 0* Moderate CRC #4 5 0* *: No errors were observed even with maximum multipath injection (0 db). Table 9. Susceptibility to Random noise in the presence of Dynamic Echoes with Re-acquisition 13

14 4.9 Susceptibility to Single Dynamic Echoes at various Delays and Doppler Rates The purpose of the multipath testing is to determine how robust is the ADTB-T television system in the presence of a single dynamic echo at various delays and Doppler rates with random noise injection. The echo power at TOV is recorded for each scenario of single echo delay and Doppler rate. All the multipath tests are done with the desired DTV signal RF level adjusted to the Moderate level (-53 dbm). Level Echo Delay (µs) Doppler Rate (Hz) Echo Power Moderate * Moderate * Moderate * Moderate * Moderate * Moderate * Moderate * Moderate * Moderate * Moderate * Moderate * Moderate Moderate * Moderate * Moderate * Moderate Moderate * Moderate * Moderate * Moderate Moderate Moderate * Moderate * Moderate *: No errors were observed even with maximum multipath injection (0 db). Table 10. Susceptibility to Single Dynamic Echo at various delays in Presence of Random Noise with Re-acquisition 14

15 4.10 Receiver Equalizer Range The purposes of these tests are to characterize the ADTB-T television system equalizer range Single Echo The delay of a single echo is changed to determine the range over which the receiver equalizer operates without any noise injection. Doppler frequency of 0.2 Hz is used to ensure inclusion of all phases. Level Echo Power Doppler Rate (Hz) Echo Delay (µs) Minimum Maximum Moderate N/A < -125* > 125* Moderate N/A Moderate N/A Moderate N/A ** 30.0 ** *: This is the maximum echo delay, which was available from the test bed. **: As there are two equal amplitude signals in this case, the time reference to zero is arbitrarily. Table 11. Receiver Equalizer Range with Re-acquisition Pair Echoes The delay of a pair of echoes (pre and post with a 1 µs offset delay) are increased together to determine the range over which the receiver equalizer operates. No random noise added. Doppler frequency of 0.2 Hz is used to ensure inclusion of all phases. Echo Doppler Echo Delay (µs) Level Power Rate (Hz) Pre Echo Post Echo Moderate N/A Moderate N/A Moderate N/A -17* 18* *: As there are three equal amplitude signals in this case, the time reference to zero is arbitrarily. Table 12. Receiver Equalizer Range with Pair Echoes (Pre and Post) with Re-acquisition 15

16 4.11 Phase noise impairment The purpose of this test is to determine the robustness of the ADTB-T television system to phase noise. The phase noise is created by injecting an FM modulated white noise at the local oscillator of the DTV modulator up-converter (IF to RF). The DTV signal is adjusted and measured as for the interference testing. This test is done with the DTV signal RF level adjusted to -53 dbm. The phase noise value is measured using an HP8560E spectrum analyzer with the phase noise measurement option. The phase noise level is increased until TOV is reached and measured in dbc/hz at 0.1 khz, 1 khz, 2 khz, 5 khz, 10 khz, 20 khz and 50 khz at either side of the peak carrier. Frequency offset (khz) Phase Noise (dbc/hz) Table 13. Phase Noise Robustness at Moderate Level with Re-acquisition 16

17 5 Conclusion Based on the laboratory test results, the ADTB-T system is very robust against Doppler shift, as well as against strong static and dynamic multipath distortion. It has the potential to be able to provide high-speed data or DTV broadcasting service to mobile terminals. However, laboratory test environment might not fully reproduce the realworld conditions for mobile reception. The system still needs to undergo extensive field test to prove its reliability to provide mobile services. It may be possible to further improve the system performances by: (1) Including modulation mode that reduces the data rate to further enhance the noise and interference robustness; (2) Increasing the size of the interleaver to improve the capability to handle deep signal fade. 17

18 Multipath Ensemble Calibration Brazil A Brazil B Brazil C Brazil D Brazil E Special Brazil C Modified Brazil C Modified Brazil D APPENDIX A MULTIPATH PROFILE DETAILS Channel Simulator Path 1 Path 2 Path 3 Path 4 Path 5 Path 6 Parameter Delay (µs) 0 Attenuation 0 OFF OFF OFF OFF OFF Phase (degrees) 0 Delay (µs) Attenuation Delay (µs) Attenuation Delay (µs) Attenuation Delay (µs) Attenuation Delay (µs) Attenuation OFF OFF OFF Phase (degrees) Delay (µs) Attenuation Phase or Doppler Hz Delay (µs) Attenuation Variable Phase or Doppler Hz 0 0 Delay (µs) Attenuation Variable Phase or Doppler 0.2 Hz Delay (µs) ATTC Attenuation 0 Varied together OFF OFF OFF Dynamic 3 Variable Phase or Doppler Hz Doppler Delay (µs) ATTC Attenuation 0 Varied together OFF OFF OFF Dynamic 4 Variable Phase or Doppler Hz Doppler Special Brazil C: EchoPath3and4areassignedsamedelay(1.506µs), but different amplitude and phase. The Path 4 is 0 db amplitude and 0 degree phase, while Path 3 is 0 db amplitude and 0.2 Hz Doppler phase shift. The combined effect of Path 3 and 4 creates a flat fading environment so that the combined multipath amplitude goes higher and lower than 0 db in a 0.2 Hz cycle. 18

19 Multipath Ensemble CRC Dynamic Channel Simulator Path 1 Path 2 Path 3 Path 4 Path 5 Path 6 Parameter Delay (µs) # Varied to Attenuation # reach # TOV # Phase or Doppler or5Hz 90 Delay (µs) China 1 Attenuation Delay (µs) China 2 Attenuation Delay (µs) China 3 Attenuation Delay (µs) China 4 Attenuation Delay (µs) China 5 Attenuation Delay (µs) China 6 Attenuation Delay (µs) China 7 Attenuation Delay (µs) China 8 Attenuation Delay (µs) China 9 Attenuation Delay (µs) China 10 Attenuation Delay (µs) China 11 Attenuation Variable Phase or Doppler Doppler Delay (µs) 0 1 China 12 Attenuation 0 Variable OFF OFF OFF OFF Variable Phase or Doppler 0 Doppler Note: The pre-echoes in the above ensembles are not indicated with negative delays, since the channel simulator does not accept any negative delays. 19