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DVB-T2_Training
- 2. Studio of Program Provider 1 Distribution Network Studio of Program Provider 2 Distribution Network Studio of Program Provider 3 Distribution Network One channel and one program over the over the channel bandwidth. Each program requires it own transmitter. TV Transmitter TV Transmitter TV Transmitter TV Transmitter TV Transmitter TV Transmitter TV Transmitter TV Transmitter TV Transmitter
- 3. Transport Stream Multiplexer Modulator Amplifier Modulator Amplifier Modulator Amplifier Audio/Video Encoder Program 1 Telecom Network (Microwave, Fibre optics) Audio/Video Encoder Program 2 Audio/Video Encoder Program 3 In a Digital structure several TV and radio programs can share a common transmitter network, Multiple programs in the same channel bandwidth Satellite
- 4. Digital Excellent quality over the whole coverage area, independent of the distance between transmitter and receiver. Analog TV Reception quality directly depends on the field strength. With increased distance the reception quality continuously decreases as the signal gets closer to the noise floor. Low Reception Quality Excellent Reception Quality
- 5. This is given in decibels (dB) and is referred to as the C/N specification. When the receiver C/N drops below the specified level, the receiver software blanks the picture and sound, or switches to a backup source, until the C/N again raises above the threshold. Analog TV Reception quality depends on field strength. As the distance between the transmitter and receiver increases reception quality continuously decreases due to noise in the picture. This is referred to a Graceful Degradation. ReceptionQuality Distance between transmitter and receiver Digital The transition from the covered to not covered area is very sharp. The position can vary slightly according to atmospheric (weather) conditions. The border between the covered and not covered regions is determined by the RF carrier to noise ratio (signal to noise) within the receiver.
- 6. • Larger FFT with extended bandwidth has lower out of band level than 2k (DVB-T) • 8MHz bandwidth, GI = 1/8 • Extended bandwidth in 8k, 16k, 32k FFT • Out of band energy is lower with larger FFT size
- 7. Summary of Differences: DVB-T DVB-T2 Forware error correction (FEC) & Code Rates Convolutional Coding + Reed Solomon 1/2, 2/3, 3/4, 5/6, & 7/8 LDPC + BCH 1/2, 3/5, 23, 3/4, 4/5, & 5/6 Modulation QPSK, 16QAM, & 64QAM QPSK, 16QAM, 64QAM & 256QAM Rotated constellation Mode N/A Rotated or None rotated modes Guard intervals 1/4, 1/8, 1/16, & 1/32 1/4, 19/256, 1/8, 19/128, 1/16, 1/32, & 1/128 Discrete Fourier Transform (DFT size) 2k & 8k 1k, 2k, 4k, 8k, 16k, & 32k Scattered Pilots 8% of total 1%, 2%, 4%, or 8% Pilot Patterns N/A 8 Patterns Avalible Continual Pilots 2.6% of total .35% of total Single or Multiple PLP
- 8. What does all this mean in coverage?
- 9. 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 0 5 10 15 20 25 C/N (dB) EffectivebitsperCell Shannon Limit DVB-T2 QPSK DVB-T2 16-QAM DVB-T2 64-QAM DVB-T2 256-QAM BICM Limit DVB-T QPSK DVB-T 16-QAM DVB-T 64-QAM Modulation and Coding Performance DVB-T “24 Mbit/s” mode DVB-T2 “36 Mbit/s” mode DVB-T2 “40 Mbit/s” mode DVB-T2 at failure DVB-T at QEF Capacity limits for simple Gaussian noise channel With LDPC can get close to theoretical limit Typically 30% gain in capacity compared with DVB-T codes.
- 10. Capacity (Bit Rate Mbps) The maximum capacity of DVB-T is approximately 31.67 Mbps The maximum capacity of DVB-T2 is approximately 50.34 Mbps CNR (Carrier to Noise Ratio) The carrier to noise ratio is controlled by the modulation mode and the code rate. With DVB-T2 there has been significant improvements in CNR. One point to remember with DVB-T and DVB-T2 the lower the transport stream bit rate the lower the CNR, this equals a more robust signal. As you increase the transport stream bit rate the CNR increases. This equals a less robust single. This means a lower quality signal goes father than a higher quality signal. Compared to DVB-T, DVB-T2 offers a higher transport stream bit rate with a comparable CNR.
- 11. The chart below shows the CNR for DVB-T (8MHz Channel) Gaussian Channel • directional antenna used • direct reception Ricean Channel • directional antenna used • multi path reception Rayleigh Channel • non-directional antenna • multi path reception EN 300 744
- 12. The chart below shows the CNR for DVB-T2 (LDPC Long Block Length: 64800 bits) Gaussian Channel • directional antenna used • direct reception Ricean Channel • directional antenna used • multi path reception Rayleigh Channel • non-directional antenna • multi path reception EN 302 755
- 13. Theoretical Comparison DVB-T DVB-T2 64 QAM 64 QAM 3/4 Code rate 3/4 Code Rate Gaussian Channel Gaussian Channel 26.3 Mb/s 30.5 Mb/s Distance in km Fieldstrength CNR CNR Noise Floor * The Noise floor includes transmitter noise, signal path noise, and receiver noise D 3.1 dB CNR = 18.0 dB CNR = 15.1 dB
- 14. Distance in km Fieldstrength 64 QAM, GI 1/16 Code rate 3/4, 32k ~ 29.2 Mbit /s C/N: 15.1 dB 16 QAM, GI 1/6 Code rate 3/4, 32k ~ 19.4 Mbit/s C/N: 10 dB QPSK, GI 1/6 Code rate 3/4, 32k ~ 9.7 Mbit/s C/N: 4.1 dB This curve represents the RF signal to noise ratio verses distance from the transmitter site for a given site effective radiated power (ERP) The area covered by a DVB-T2 transmitter is strongly depending on transmitter site ERP and the selected parameters for the COFDM signal, see following examples noise floor C/N C/N C/N The C/N values given above are represent Gaussian channel values C/N 256 QAM, GI 1/16 Code rate 3/4, 32k ~ 38.9 Mbit /s C/N: 20 dB
- 15. Questions