Abstract: Methods and apparatuses for minimizing co-channel interference in communications systems are disclosed. A method in accordance with the present invention comprises scrambling a first frame using a first scrambling code, attaching a first header to the first frame to create the first signal, scrambling a second frame using a second scrambling code, attaching a second header to the second frame to create the second signal, and transmitting the first signal and the second signal over different channels of the communication system.

Abstract: A system and method for data transmissions in a wireless communications system, which accommodates for a periodic blockage of the transmission signal, is provided. A data stream is segmented into packets of a predetermined fixed-size for a burst-mode transmission over a channel of the communications system, wherein the transmission is subject to a periodic blockage. A forward error correction outer code is then applied to the packets of the data stream for recovery of packets subjected to the periodic blockage, and a unique word is added to each packet for acquisition of frequency, carrier phase and symbol timing of the respective packet. The packets of the data stream are interleaved based on an interleaver of a depth based at least in part on a ratio of a blockage free duration between two consecutive blockages of the periodic blockage to a duration of each blockage of the periodic blockage.

Abstract: A parameterized interleaver design process is provided, which optimizes the design for interleavers of any size, and can be completely specified using only a few design parameters. According to the parameterized interleaver design process an interleaver ?(i) of a length N is generated. A number of subpermutation masks are defined, and a first intermediate interleaver permutation is partitioned into a number of subgroups, wherein the number of subgroups corresponds with the number of subpermutation masks. Each of the subgroups of the first intermediate interleaver permutation is partitioned into a number of further subgroups, and each of the subpermutation masks is applied to each of the further subgroups of a corresponding subgroup of the first intermediate interleaver permutation, resulting in a corresponding portion of a second intermediate interleaver permutation. The resulting interleaver ?(i) is generated based at least in part on the first and second intermediate interleaver permutations.

Abstract: An approach for reliably communicating over a satellite in support of a communication service including, for example, as direct broadcast satellite and data service, is disclosed. An input message is encoded, yielding a structured Low Density Parity Check (LDPC) coded message. The coded message is modulated according to a high order modulation scheme that has a signal constellation representing more than two symbols per signaling point—e.g., 8-PSK (Phase Shift Keying) and 16-QAM (Quadrature Amplitude Modulation). The system includes a transmitter configured to propagate the modulated signal over the satellite. The above approach is particularly applicable to bandwidth constrained communication systems requiring high data rates.

Abstract: Methods, systems and software are provided for high order signal modulation based on improved signal constellation and bit labeling designs for enhanced performance characteristics, including decreased power consumption. According to the improved signal constellation and bit labeling designs for enhanced performance characteristics, designs for 8-ary, 16-ary, 32-ary and 64-ary signal constellations are provided. According to an 8-ary constellation, improved bit labeling and bit coordinates are provided for a 1+7APSK signal constellation. According to a 16-ary constellation, improved bit labeling and bit coordinates are provided for a 6+10APSK signal constellation. According to three 32-ary constellations, improved bit labeling and bit coordinates are provided for a 16+16APSK signal constellation and two 4+12+16APSK signal constellations.

Abstract: A method for efficient retransmission over a satellite network including transmitting data packets to VSATs, receiving retransmission requests for at least one of the data packets from the VSATs, generating a retransmission packet based on the retransmission requests using XOR summing, transmitting the retransmission packet to the plurality of VSATs.

Abstract: An approach is provided for minimizing co-channel interference in a communication system is disclosed. A header of a first frame is scrambled based on a first unique word. A header of a second frame is scrambled based on a second unique word. The first frame including the corresponding scrambled header and the second frame including the corresponding scrambled header are transmitted, respectively, over adjacent co-channels of the communication system. Each of the frames further includes a payload and a pilot block. The payload and the pilot block of the first frame are scrambled based on a first scrambling sequence. The payload and the pilot block of the second frame are scrambled based on a second scrambling sequence. The above arrangement is particularly suited to a digital satellite broadcast and interactive system.

Abstract: An approach is provided for processing structure Low Density Parity Check (LDPC) codes. Memory storing edge information and a posteriori probability information associated with a structured parity check matrix used to generate Low Density Parity Check (LDPC) coded signal are accessed. The edge information represent relationship between bit nodes and check nodes, and are stored according to a predetermined scheme that permits concurrent retrieval of a set of the edge information.

Abstract: Methods include configuring M parallel accumulation engines, accumulating a first information bit at a first set of specific parity bit addresses using the accumulation engines, increasing a parity bit address for each member of the first set of specific parity bit addresses by a pre-determined offset for each new information bit, accumulating subsequent information bits at parity bit addresses that are offset from the specific parity bit addresses by a pre-determined offset until an M+1 information bit is reached, accumulating the next M information bits at a second set of specific parity bit addresses using the accumulation engines, increasing a parity bit address for each member of the second set of specific parity bit addresses by the pre-determined offset for each new information bit; and repeating accumulating and increasing the addresses until the information bits are exhausted. Related systems are described.

Abstract: A communications system includes a base station that is configured to transmit a signal that is modulated according to a predetermined modulation scheme and an orthogonal frequency division multiplexing scheme, wherein the signal is encoded using space-frequency coding. The base station includes a plurality of multiple-input multiple-output (MIMO) transceivers. The system includes a terminal that is configured to receive the modulated signal. The above arrangement is particularly applicable to providing multichannel multipoint distribution services (MMDS) over a radio communications system.

Abstract: An approach is providing for supporting broadcast transmission of low density parity check (LDPC) coded signals. A receiver includes a decoder configured to decode an LDPC signal to output a decoded signal. The decoder is further configured to operate as an encoder; as such, interference cancellation can be implemented by the encoder re-encoded the received decoded signal. The above approach has particular applicability to satellite broadcast systems.

Abstract: An approach is provided for decoding a low density parity check (LDPC) coded signal. Edge values associated with a structured parity check matrix used to generate the LDPC coded signal are retrieved from memory. The edge values specify the relationship of bit nodes and check nodes, and are stored within memory according to a predetermined scheme that permits concurrent retrieval of a set of the edge values. A decoded signal corresponding to the LDPC coded signal is output based on the retrieved edge values.

Abstract: An approach is provided for supporting carrier synchronization in a digital broadcast and interactive system. A carrier synchronization module receives one or more signals representing a frame that includes one or more overhead fields (e.g., preamble and optional pilot blocks and one or multiple segments separated by pilot blocks). The module estimates carrier frequency and phase on a segment by segment basis and tracks frequency between segments. Carrier phase of the signal is estimated based upon the overhead field. Estimates carrier phase of random data field are determined based upon the estimated phase values from the overhead fields, and upon both the past and future data signals. Further, the frequency of the signal is estimated based upon the overhead fields and/or the random data field. The above arrangement is particularly suited to a digital satellite broadcast and interactive system.

Abstract: An approach for reliably communicating over a satellite in support of a communication service including, for example, as direct broadcast satellite and data service, is disclosed. An input message is encoded, yielding a structured Low Density Parity Check (LDPC) coded message. The coded message is modulated according to a high order modulation scheme that has a signal constellation representing more than two symbols per signaling point—e.g., 8-PSK (Phase Shift Keying) and 16-QAM (Quadrature Amplitude Modulation). The system includes a transmitter configured to propagate the modulated signal over the satellite. The above approach is particularly applicable to bandwidth constrained communication systems requiring high data rates.

Abstract: An approach is provided for supporting frame synchronization in a digital broadcast and interactive system. A transmitter includes an encoder that outputs a Low Density Parity Check (LDPC) codeword. The transmitter also includes a framing module generates a LDPC coded frame in response to the LDPC codeword, and appends a physical layer signaling field to the LDPC codeword for specifying modulation and coding information associated with the LDPC coded frame. The physical layer signaling field is encoded with a Forward Error Correction (FEC) code and has an embedded framing structure to assist with frame synchronization. The above arrangement is particularly suited to a digital satellite broadcast system.

Abstract: A method and apparatus for providing an asymmetrical backwards compatible communications signal that is capable of being decoded by QPSK and OQPSK receivers as well as PSK and QAM receivers is provided. The invention comprises a timing error accumulator coupled to a first bit stream. The first bit stream includes content that is common to the QPSK/OQPSK receiver and to the PSK/QAM receiver. A phase error accumulator is coupled to a second bit stream and adjusts the phase of symbols in the second bit stream. A phase and timing error compensator is coupled to the phase error accumulator and the timing error accumulator and adjusts the first and second bit streams received from the phase error accumulator and the timing error accumulator in order to reduce timing and phase errors. A higher order modulator coupled to the phase- and timing error compensator is also provided. The higher order modulator processes the first and second bit streams to provide the asymmetrical backwards compatible signal.

Abstract: A parameterized interleaver design process is provided, which optimizes the design for interleavers of any size, and can be completely specified using only a few design parameters. According to the parameterized interleaver design process an interleaver ?(i) of a length N is generated. A number of subpermutation masks are defined, and a first intermediate interleaver permutation is partitioned into a number of subgroups, wherein the number of subgroups corresponds with the number of subpermutation masks. Each of the subgroups of the first intermediate interleaver permutation is partitioned into a number of further subgroups, and each of the subpermutation masks is applied to each of the further subgroups of a corresponding subgroup of the first intermediate interleaver permutation, resulting in a corresponding portion of a second intermediate interleaver permutation. The resulting interleaver ?(i) is generated based at least in part on the first and second intermediate interleaver permutations.

Abstract: An approach is provided for encoding short frame length Low Density Parity Check (LDPC) codes. An encoder generates a LDPC code having an outer Bose Chaudhuri Hocquenghem (BCH) code. Structure is imposed on the LDPC codes by restricting portion part of the parity check matrix to be lower triangular and/or satisfying other requirements such that the communication between bit nodes and check nodes of the decoder is simplified. Further, a cyclic redundancy check (CRC) encoder is supplied to encode the input signal according to a CRC code. This approach has particular application in digital video broadcast services over satellite.

Abstract: A method and apparatus for encoding data for transmission in a communication system provides increased efficiency in bandwidth utilization through higher data rates, lower error rates, lower power levels, and/or increased capacity. A set of orthogonal codes is partitioned into subsets. The data to be transmitted is partitioned into packets of bit sequences, each of which is mapped to an orthogonal code in an assigned subset. The number of members in a particular subset is determined by the relative transmission requirements of the data signal the subset will be used to encode.

Abstract: A new pulse shape for CPM is introduced which is obtained by a linear combination of well-known RC and REC pulse shapes. The new pulse shape addresses the tradeoff between the width of the PSD main lobe and the rate of decay of the side lobe to improve the coded performance of multi-carrier systems affected by ACI. Also, a methodology is proposed to design and evaluate the performance of the new pulse shape for multi-carrier, coded systems based on the modulation constrained capacity. Furthermore, a binary convolutional code and the CPM modulator are concatenated using an S-random bit interleaver to lower the error floor. Finally, Laurent representation of the new pulse shape is suggested such that by retaining only the principal pulses at the receiver, complexity of the receiver can be reduced.