Abstract: Apparatus for iterative decoding of a sequence of signal packets coded in accordance with a multi-component coding scheme. The apparatus includes a plurality of decoders, each of which performs a respective different decoding method on one of the signal packets, such that the plurality of decoders operate substantially concurrently.

Abstract: A method and apparatus for normalizing a plurality of state-metric registers in a decoder using a trellis. The method includes determining an approximate minimum of respective state-metric values stored in the plurality of state-metric registers, and subtracting the approximate minimum from the values. Determining the approximate minimum preferably includes determining the minimum of a predetermined number of most significant bits in the plurality of state-metric registers.

Abstract: Apparatus for iterative decoding of a sequence of signal packets coded in accordance with a multi-component coding scheme. The apparatus includes a plurality of decoders, each of which performs a respective different decoding method on one of the signal packets, such that the plurality of decoders operate substantially concurrently. Iterative decoding may be stopped if a predefined threshold maximum number of iterations is reached, or if the previous two decoder iterations have satisfactory cyclic redundancy checks (CRC), or if the input frame buffer to the decoder is filled to within a predefined percentage of its storage capacity.

Abstract: A method and apparatus for determining the rate of received data in a variable rate communication system. The receiving system decodes each frame of the received signal to produce a set of normalized correlation metrics, cyclic redundancy check (CRC) bits, and possibly Yamamoto quality metrics, one for each possible data rate. The normalized correlation metric for each rate is calculated from a correlation value an a constant computed for that rate. The correlation value is determined from a correlation of the demodulated soft frame symbols and the re-encoded frame. The highest normalized correlation metric is selected and the CRC bit for this data rate is checked. If the CRC checks, this data rate is indicated as the received data rate. Otherwise, the next highest normalized correlation metric is selected and the process continues. If no CRC check, an erasure is indicated.

Abstract: A method and apparatus for rate determination in a communication system using orthogonal rate-dependent Walsh covering codes. Orthogonal rate-dependent Walsh codes are used to cover repeated code symbols prior to transmission over a communication link. In one embodiment, the Walsh codes comprise orthogonal binary codes that increase by powers of two for each data rate used in the system. Code symbols are repeated and then covered at the symbol rate using the inventive orthogonal Walsh codes. The inventive code symbol repetition and encoding method and apparatus is particularly advantageous in encoding data that contains long sequences of logical zeros and ones. The orthogonal nature of the code symbols encoded in accordance with the present invention allows use of a more accurate and less complex data rate determination apparatus in the receiver. Rate determination is thereby improved resulting in an improvement in data service capability and a reduction in decoding errors.

Abstract: A method and apparatus for decoding a frame of multi-rate encoded digital data which contains redundant information provided to validate the decoding operation. A frame of data is received which contains information bits and cyclic redundancy check (CRC) bits. In accordance with the invention, the received frame is decoded and a check is conducted to determine whether the CRC bits correspond correctly for the decoded information bits. If the decoded frame passes the CRC test process, the decoded fame is provided to the user. However, if the decoded frame does not pass the CRC test, then at least one additional decoding process is performed on the received frame. In the first exemplary embodiment of the present invention, on a failure of the CRC check, the data is decoded using a trellis decoder and the data that yields the next most likely path through the trellis is selected.

Abstract: The method for selecting CRC polynomials (or CRC generators) for linear coded systems. In the exemplary embodiment, a communication system utilizes a concatenated code comprising a CRC code and a convolutional code. The CRC generators are selected based on the distance spectrums which have been computed for all possible CRC generators of a given length L. The distance spectrum comprises a listing of the number of paths (or code words) at various weights (or Hamming distance). These paths represent error information sequences I(x) which have diverged from an all-zero transmitted sequence (or the zero state) and have merged back into the zero state. The paths are checked by the CRC generators. If the CRC check passes, indicating that the error information sequence is undetected by the CRC check, the weight of this path is calculated and the distance spectrum for this CRC generator is updated. Otherwise, if the CRC does not check, the path is ignored. The CRC generator with the maximum minimum distance d.sub.

Abstract: The present invention is a novel and improved method and apparatus for decoding a frame of digital data which contains redundant information provided to validate the decoding operation. In the present invention, a frame of data contains information bits and cyclic redundancy check (CRC) bits. The received frame is decoded and a check is conducted to determine whether the CRC bits correspond correctly for the decoded information bits. If the decoded frame passes the CRC test process, the decoded fame is provided to the user. However, if the decoded frame does not pass the CRC test, then at least one additional decoding process is performed on the received frame. In the first exemplary embodiment of the present invention, if the CRC test is failed, a noise vector of a predetermined set of noise vectors is summed with the received frame and the resultant frame is decoded for a second time.