a transmitter transmits successive data fields , and each data field includes a mix of vsb data segments and e - vsb data segments and interleaved portions of maps . the maps define the mixes of vsb data segments and e - vsb data segments in corresponding data fields to be transmitted after the corresponding maps are transmitted . prior to interleaving , the maps are encoded . at a receiver , the maps are de - interleaved and de - coded so as to derive the mix of vsb and e - vsb data segments defining each of the data fields . the interleaving and de - interleaving have a combined latency of at least l fields . the vsb and e - vsb data segments of each of the data fields are separated in response to the de - interleaved maps .