| 摘要 |
<p>A robust data extension is added to a standard 8VSB digital television transmission system by encoding high priority data packets in a rate 1/2 trellis encoder. The high priority data 1/2 trellis encoded packets are multiplexed with normal data packets and input into the normal data service of an 8VSB system, which further contains a rate 2/3 trellis encoder. The combined trellis encoding results in a rate 1/3 trellis encoding for robust data packets and a rate 2/3 trellis encoding for normal packets. Rate 1/3 trellis encoding provides the substantially equivalent robustness of a 2VSB signal while retaining the backward compatibility characteristics of an 8VSB signal. Four legacy requirements for backward compatibility with existing ATSC compliant receivers and transmitters are met: 1) the modulus of the symbol set for robust data transmission is the same as that for an 8VSB signal; 2) compatibility with existing trellis encoders and decoders is maintained; 3) Reed Solomon parity bytes are transmitted as normal data so that existing receivers do not flag robust data packets as having Reed Solomon parity errors; and 4) MPEG compatibility is maintained by guaranteeing that robust data packets will not appear as false MPEG packets that otherwise could destabilize the existing MPEG decoder.</p> |
