Patent ID: 7830983
Filing Date: 2010-11-09
Classification: H04L

Abstract:
1. A method for transmitting additional data in a digital transmission system, comprising the steps of: receiving a primary signal comprising digital Level 1 data; performing digital multiple phase shift keying (D-MPSK) modulation on the digital Level 1 data; adding a secondary signal to the D-MPSK modulated digital Level 1 symbols as an offset to produce an offset signal, wherein the secondary signal comprises digital Level 2 data not derived from the received primary signal, such that the digital Level 2 data is additional data that is superimposed on the digital Level 1 data to create a hierarchical modulated data stream prior to differential signal mapping; and transmitting the offset signal on a carrier wave through space to receivers including legacy receivers using an orthogonal frequency-division multiplexing (OFDM) transmission system, wherein the step of adding the secondary signal further comprises adding equal and opposite phase shifts for alternative bit values of the digital Level 2 data as a function of superimposing the digital Level 2 data prior to the differential signal mapping.