E-VSB map signaling

Addition of a backwards-compatible enhanced data mode (E-VSB) to ATSC (Advanced Television Systems Committee) standard 8-VSB transmissions requires a way to reliably indicate to new enhanced receivers the mix of E-VSB and 8-VSB data. This mix is indicated by "map" data using bits in the reserved area of the 8-VSB data field sync. This must be done in a manner that allows for changing the mix "on the fly" without loss of E-VSB/8-VSB data. The reception of the map data must be significantly more robust than the lowest code rate E-VSB data. A method is described that offers reliable signaling without latency for channel-change in the receiver.