A-VSB
A-VSB or Advanced VSB is a modification of the
A-VSB builds on the existing ATSC transmission standard to enhance
A-VSB incorporates three new elements: a Supplementary Reference Signal (SRS), a Scalable Turbo Stream (STS), and support for Single Frequency Networks (SFN).
Supplementary Reference Signal
A-VSB receivers utilize the SRS in order to remain synchronized with the transmission. This helps maintain reception of the main stream and any
The SRS adds an additional
Scalable Turbo Stream
The addition of a new turbo-coded stream enables broadcasters to increase the error-correction capability of a secondary stream transmission. Two options are proposed for the turbo stream: ½ and ¼ rate codes, i.e., the new video stream requires 2x or 4x the video rate in final transport payload. The new Threshold of Visibility (TOV) SNRs are 9.6 and 4.5 dB, respectively; 1.6dB is claimed with diversity reception. Conventional 8VSB has a TOV SNR of 15.1 dB. The turbo codec uses single-input single-output (SISO) iterative decoding and time interleaving.
Single Frequency Networks
The last option—SFN—is made possible by adding a VSB Frame Initialization Packet (VFIP) that synchronizes the transport frame sequences to a GPS reference.
References
- Samsung Press Release, SAMSUNG's Advanced-VSB Technology To Bring Portable And Mobile TV To North American Digital TV Broadcasting, retrieved 2007-04-05, January 8, 2007.