Abstract: Interleaving methods and apparatus are disclosed for an in-band on-channel digital audio broadcasting system. The guard periods that separate any two adjacent symbols in a conventional OFDM system can provide a mechanism for OFDM frame synchronization. The guard period of successive OFDM frames is utilized to establish one or more unique positive or negative patterns and thereby provide a mechanism for interleaver synchronization. By proper positioning of the guard period patterns, one or more particular portions of each interleaver block are identified, such as the beginning and midpoint of each interleaver block. The present invention identifies the beginning of each interleaver block, for example, by positioning the fourth negative cyclic prefix with OFDM frame zero (0). The present invention can optionally identify the midpoint of each interleaver block, for example, by positioning the fourth negative cyclic prefix with OFDM frame 206.

Abstract: An OFDM receiver recovers an rf signal as in-phase (I) and quadrature phase (Q) components of a baseband signal sampled in an A/D converter. The I and Q components of a received symbol are correlated at all sampling points. Correlation values are averaged over the latest L frames and saved in an L-deep FIFO. Symbol amplitude and phase are computed and passed to an offset estimator and an OFDM frame synchronization estimator. A phase-locked loop oscillator provides a sample number identifying the OFDM frame boundary to the offset estimator. An estimated offset value is selected as the negative of the phase angle of the auto correlation.

Abstract: Interleaving methods and apparatus are disclosed for an in-band on-channel digital audio broadcasting system. The guard periods that separate any two adjacent symbols in a conventional OFDM system can provide a mechanism for OFDM frame synchronization. The guard period of successive OFDM frames is utilized to establish one or more unique positive or negative patterns and thereby provide a mechanism for interleaver synchronization. By proper positioning of the guard period patterns, one or more particular portions of each interleaver block are identified, such as the beginning and midpoint of each interleaver block. The present invention identifies the beginning of each interleaver block, for example, by positioning the fourth negative cyclic prefix with OFDM frame zero (0). The present invention can optionally identify the midpoint of each interleaver block, for example, by positioning the fourth negative cyclic prefix with OFDM frame 206.

Abstract: Interleaving methods and apparatus are disclosed for an in-band on-channel digital audio broadcasting system. The guard periods that separate any two adjacent symbols in a conventional OFDM system can provide a mechanism for OFDM frame synchronization. The guard period of successive OFDM frames is utilized to establish one or more unique positive or negative patterns and thereby provide a mechanism for interleaver synchronization. By proper positioning of the guard period patterns, one or more particular portions of each interleaver block are identified, such as the beginning and midpoint of each interleaver block. The present invention identifies the beginning of each interleaver block, for example, by positioning the fourth negative cyclic prefix with OFDM frame zero (0). The present invention can optionally identify the midpoint of each interleaver block, for example, by positioning the fourth negative cyclic prefix with OFDM frame 206.

Abstract: A method for use in a receiver in an orthogonal frequency division multiplexing-based data transmission system of detecting frame synchronization with respect to a signal received from a transmitter in the system comprises the following steps. First, the received signal is searched at a first predetermined sub-carrier frequency and at least a second predetermined sub-carrier frequency for a previously inserted data pattern. Then a frame boundary in the received signal is identified as a position where the data pattern is detected at both the first predetermined sub-carrier frequency and the second predetermined sub-carrier frequency.