In the previous post, I discussed using Splat! to predict the receive level of an RF signal. In particular I considered CBLFT UHF CH25 as received from the CN Tower as shown above in Figure 1. In order to study ATSC_8VSB which is the DTV standard used in North America, GNU Radio can be used to actually simulate a transmitter and receiver.
Figure 2 ATSC DTV Standard Signal Flow
Figure 2 shows the block diagram of ATSC_8VSB from Ref.1. Video information is compressed by an MPEG-2 video coder and audio is compressed by a Dolby AC-3 coder. These two streams are mixed with Auxiliary & Control data to form a MPEG-2 transport stream of packets. These packets undergo Channel Coding and 8VSB Modulation with modules as shown in Figure 3.
Figure 3 ATSC Channel Coding & Modulation Modules
Figure 4 shows a GNU Radio simulation of ATSC_8VSB transmission. An MPEG-2 video file is read into the simulation and processed by the channel coding blocks. The signal is then 8VSB modulated to UHF CH25 and the spectrum displayed.
Figure 4 UHF CH25 ATSC_8VSB Simulation with Video & Spectrum
GNURadio Companion Basics Course:
Please send your comments, questions and suggestions to:
#1 – “A/53 ATSC Digital Television Standard Parts 1 – 6, 2007
#2 – “GNU Radio 3.7.0 Documentation – gnuradio.atsc Signal Blocks”