Two-dimensional differential demodulation for OFDM

The possibility of combining differential demodulators in time direction and frequency direction for orthogonal frequency-division multiplexing (OFDM) frames is investigated. The proposed algorithm uses not only the direction in which the information is modulated, but also joins it with other symbols in time or frequency direction of the OFDM frame, resulting in an additional second direction that is differentially demodulated as well. In the special case that is investigated here, the second direction does not carry any modulated information. Nevertheless, it is shown that it can be used for the two-dimensional demodulation process without changing the transmitter. Therefore, the proposed algorithm is applicable for existing digital transmission systems, for example, digital audio broadcasting, as well as new systems.