ATSC 3.0 basics tutorial | features, Protocol Stack, Physical Layer, Frame structure, advantages or benefits
This ATSC 3.0 tutorial covers basics of ATSC 3.0 TV technology including features. It mentions ATSC 3.0 protocol stack, ATSC 3.0 Physical layer, ATSC 3.0 Frame structure and ATSC 3.0 advantages or benefits.
Introduction: The ATSC standard 3.0 is successor to ATSC 1.0 and ATSC 2.0 standards used for digital television broadcasting over various transmission networks such as terrestrial, satellite or cable. These standards are developed and manageed by Advanced Television Systems Committee consisting of member companies.
Features of ATSC 3.0 TV Technology
Following are the features of ATSC 3.0 TV technology:
• 4K UHD TV is key goal of ATSC 3.0 standard. 8K is possible in the future.
• Supports resolution of 3840x2160 at a frame rate of 60 Hz.
• Provides High Dynamic Range.
• 10 bits/pixel is used for transmission.
• Enables HDTV delivery to mobile and handheld devices such as smartphones, tablets etc.
ATSC 3.0 Protocol Stack
The figure-1 depicts ATSC 3.0 protocol stack.
As shown it consists of following protocol layers.
• System Discovery and Signaling: This layer uses unique sequence to find the frame or signal.
• Physical layer:It uses OFDM technique used to transmit bits over the air in 6 MHz bandwidth.
• Protocols: This layer uses internet protocols. Here data is organized as streams or files.
• Presentation: This layer uses different coding schemes for pictures and sound to enable compression. It includes UHD, HD & SD multicast and immersive audio.
• Applications:It is software where in screen is considered to be a web page.
ATSC 3.0 Frame Structure
The figure-2 depicts ATSC 3.0 frame structure. As shown ATSC 3.0 frame consists of bootstrap, preamble and payload parts. Frame is composed of one of more than one subframes.
Bootstrap: It is used to configure the receiver part to decode
Preamble: It has two parts viz. L1-Basic, L1-Detail. L1-Basic helps in decoding L1-Detail and first subframe. L1-Basic uses 200 bits per coded block is at fixed code rate of 3/15. It uses 3 QPSK and 4 NUC types viz. NUC_16_8/15, NUC_64_9/15, NUC_256_9/15, NUC_256_13/15. L1-detail carries critical information such as FFT size, modulation, FEC code rate etc. which helps in decoding rest of the subframes. L1-detail uses code rate of 6/15 for modes 3 to 7 while uses QPSK at code rate of 3/15 for mode-1 and mode-2.
Payload: Rest of the ATSC 3.0 frame consists of payload which is in the format as defined by L1 signaling.
ATSC 3.0 Physical Layer
The figure-3 depicts ATSC 3.0 Physical layer for downlink and uplink. The downlink contains all the blocks or modules used in digital TV transmitter of broadcasting station. This signal is received and decoded/demodulated by ATSC tuner at TV set. The uplink part shown is the uplink processing which takes place at transmitter part of subscribers having ATSC 3.0 technology features. It is used for broadband connectivity with main station.
ATSC 3.0 Physical layer consists of following generic modules.
• Scrambler• FEC• Bit interleaver• Mapper• Time interleaver • OFDM Framer• Frequency Interleaver• Pilots• Reserved tones• Guard interval functions etc.
Figure-3 shows BICM module. BICM stands for Bit Interleaved and Coded Modulation. It consists of three parts viz. FEC (Forward Error Correction), Bit interleaver (BIL) and mapper (MAP).
ATSC 3.0 physical layer uses LDM technique. LDM stands for Layered Division Multiplexing which uses spectrum overlay technique to super-impose different physical layer streams with different unique power levels, modulations and code rates. This technique helps in decoding the data in different environments and applications. LDM receiver uses signal cancellation technique to decode the signal. The technique is also called as Power Division Multiplexing due to use of different power levels for different layers.
ATSC 3.0 Advantages or benefits
Following are the advantages or benefits of ATSC 3.0 technology.
• It leverages benefits of both broadcasting and broadband technologies. It mixes or merges over the air TV with internet broadband including wifi.
• Provides weather alerts or emergency alerts.
• Uses advanced compression to supports different audio and video over the available 6 MHz BW.
• It uses robust modulation upto 4096QAM.
• The technology is used by different advertizers to display advertizements on the TV.
• It has many more interactive features including multichannel immersive audio.
• It is backward compatible with previous TV technologies.
• It has been used for LTE mobile offload to relieve high bandwidth traffic from LTE network to TV transmission networks to deliver it to LTE customers/users.
• Due to channel bonding feature, the technology provides efficient usage of available spectrum.
• Due to usage of OFDM technique and high modulation techniques such as 256 QAM or 4096QAM in the physical layer of ATSC 3.0, significant higher data capacity can be achieved.
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