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 communications system has, a base station (40) and an inter-working gateway (48) for operating two-way wireless Internet communications over a Universal Mobile Telecommunications System (UMTS) communications network. The Internet communications are segmented and multiplexed into framing protocol-protocol data units (FP-PDUs) to operate over the UMTS communications network.

Abstract: A frame formatting technique for filling a fixed length master frame with a number of variable length frames and adding additional data to synchronize the individual variable length frames and increase the randomness of the fixed length master frame. The technique fills unused portions of the fixed length master frame with random data to maximize the randomness of the fixed length master frame which can be used to produce a well behaved modulated signal for digital broadcasting, thereby increasing the efficiency of digital broadcasting system.

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: In accordance with the principles of the present invention, in addition to conventional use of frequency division multiplexed upper and lower side bands, the spectral area occupied by the analog host will be utilized by applying a one-dimensional modulation, e.g., pulse amplitude modulation (PAM) as opposed to the conventional use of a two-dimensional modulation, e.g., quadrature amplitude modulation (QAM). Furthermore, the analog and digital information within the analog host bandwidth may be combined in quadrature to keep the signals orthogonal. Thus, should one side band under the analog carrier be deteriorated or obliterated by adjacent channel interference, the other side band under the analog carrier can still provide useful data and hence better digital audio codec performance. By transmitting one or two digital data streams asymmetrically with respect to the center frequency, particular digital side bands can be rendered useless as environmental conditions warrant (e.g.

Abstract: A receiver of digital information typically performs a frame synchronization finction to locate the beginning of a frame of within received information. Frame and interleaver synchronization functions are complex tasks to accomplish, and are made more so when transmitted information is subjected to harsh interference by the environment of the transmission media, e.g., wireless media. Such interference may be sufficiently minimized by filtering the band signal at the receiver in a simple manner to allow receiver processes to perform successfully frame synchronization and interleaver functions on the filtered signal, in which such filtering may be achieved using a simple bandpass filter. Although such filtering renders the received signal sufficiently clean to recover frame synchronization and interleaver signals, it nevertheless corrupts the information carried in the signal, thereby making it extremely difficult to recover the information.

Abstract: A method and a receiver for reducing adjacent-channel interference to a digitally modulated receive signal evaluates error rates of the receive signal associated with different receive bandwidths of the receive signal. The receiver selects a preferential bandwidth among the different bandwidths based on a suitably low error rate associated with the preferential bandwidth. The selection of the different bandwidths is achieved by digital signal processing that weighs desired data bits representing a desired bandwidth differently than rejected data bits representing a rejected bandwidth.

Abstract: An OFDM subcarrier method and apparatus effectively reassigns subcarriers with respect to a data stream from a plurality of Digital Audio Broadcast (DAB) services or programs to reduce selective effects (e.g., selective channel fading) of the transmission channel (e.g., an FM station) on some of the DAB services or programs but not on others. In one embodiment, a symbol reassignment encoder at the transmitter shuffles the data or symbols in the data stream from the DAB services to effectively reassign the subcarriers used by each of the DAB services. The reassignment spreads the selective effects of the transmission channel, e.g., channel fading, over a larger group of DAB services, to improve the robustness and quality of the overall transmission channel.

Abstract: An orthogonal frequency division multiplexing (OFDM) technique which is time division multiplexed to reduce the overall effect on individual services from conditions such as selective fading. In accordance with the principles of the present invention, all available subcarriers in a channel are assigned to fewer than all of the requesting services, e.g., to just one particular service for a period of time. The period of time is preferably independent of the length of a conventional data frame. Thereafter, a second service is assigned access to the use of all available subcarriers for a period of time corresponding to its required bandwidth, and so on until all requesting services are allotted a portion of time for access to all available subcarriers. Any one service may utilize any number of the available subcarriers in a particular superframe containing one cycle of transmissions for all services.