Abstract: A method, base station and subscriber station which use recursive systematic codes (RSC codes) for channel coding in GSM mobile radio systems. In addition, these RSC codes also can be used on the basis of the hardware installed in existing GSM mobile radio systems. The RSC codes can be introduced during the introduction of an adaptive multirate coder.

Abstract: A method and a device for decoding for use in a code-division multiple access (CDMA) transmission system for demodulating a received signal available in serial code concatenation, with a two-step coding being carried out at the transmitting end of the transmission system, including an orthogonal, multi-step inner Hadamard code and an outer, error-correcting code of a predefined rate. In the receiver, a soft-in/soft-out decoder is provided, at whose input and output soft values are processed as reliability information, i.e., L-values. The soft output of the first decoder step, or inner code is the soft input for the decoder step, or outer code, that follows in each case, the first decoder step receiving the output values of the preceding demodulation, which contain the channel's reliability information. A soft output is used by the decoder, in particular a MAP decoder, as a-priori information for the systematic bits of the Walsh function of the inner code for decoding of the inner code.

Abstract: A method of transmitting encoded digital signals and decoding the digital signals at a receiver. During source encoding, the signals are divided into a plurality of subunits. Each subunit is assigned one of a plurality of differing levels of significance. The subunits are hierarchically ordered in a data frame according to their levels of significance. The subunits are then channel encoded utilizing a variable rate code. The rate increases for increasing levels of significance. At the receiver decoder, a subset of the subunits are correctly decoded to produce a correct portion of decoded data. The correct portion is defined by a position of a first error in the data frame. The position of the first error in the data frame is dependent upon at least one of the encoding rate, channel quality, and decoding complexity. The digital signals are then reconstructed using only the correct portion of decoded data.

Abstract: A method and a device for decoding for use in a code-division multiple access (CDMA) transmission system for demodulating a received signal available in serial code concatenation, with a two-step coding being carried out at the transmitting end of the transmission system, including an orthogonal, multi-step inner Hadamard code and an outer, error-correcting code of a predefined rate. In the receiver, a soft-in/soft-out decoder is provided, at whose input and output soft values are processed as reliability information, i.e., L-values. The soft output of the first decoder step, or inner code is the soft input for the decoder step, or outer code, that follows in each case, the first decoder step receiving the output values of the preceding demodulation, which contain the channel's reliability information. A soft output is used by the decoder, in particular a MAP decoder, as a-priori information for the systematic bits of the Walsh function of the inner code for decoding of the inner code.

Abstract: A method and a device for decoding for use in a code-division multiple access (CDMA) transmission system for demodulating a received signal available in serial code concatenation, with a two-step coding being carried out at the transmitting end of the transmission system, including an orthogonal, multi-step inner Hadamard code and an outer, error-correcting code of a predefined rate. In the receiver, a soft-in/soft-out decoder is provided, at whose input and output soft values are processed as reliability information, i.e., L-values. The soft output of the first decoder step, or inner code is the soft input for the decoder step, or outer code, that follows in each case, the first decoder step receiving the output values of the preceding demodulation, which contain the channel's reliability information. A soft output is used by the decoder, in particular a MAP decoder, as a-priori information for the systematic bits of the Walsh function of the inner code for decoding of the inner code.

Abstract: An adaptive abort criterion in iterative decoding of transmitted, multi-dimensionally encoded information employs the relative entropy, approximations of the relative entropy or quantities similar thereto as criterion for the change in the weighted decisions of successive iteration sub-steps. When an iteration sub-step does not produce a change of the relative entropy lying above a predetermined threshold, then the iterative decoding is aborted.

Abstract: Method for protected transmission of data with multi-component coding, whereby a non-uniform error protection is achieved by selection of important bits or bit sequences from an information sequence (I), the bit sequences being supplied to further component coders (COD1 through COD3).

Abstract: Improved Viterbi decoding of radio signals of the type calculating a metric increment ##EQU1## wherein .lambda..sub.k is calculated at time intervals indexed by k, i is a data bit position index, y is a received value, x is a coded bit of a predetermined sequence, and a is a fading factor, uses a metric addition B.sub.k according to the equation ##EQU2## where B.sub.k is a function of the quantityu.sub.k L.sub.k =log.sub.10 P(u.sub.k =+1)/P(u.sub.k =-1)!.If the channel is binary symmetrical, B.sub.k =u.sub.k L.sub.k /L.sub.0k where L.sub.0k =log (1-P.sub.0k)/P.sub.0k ! and P.sub.0k is the binary symmetrical channel error probability. If the channel is a gaussian and fading channel then B.sub.k =u.sub.k L.sub.k / (E.sub.s /N.sub.0) log.sub.10 e! where E.sub.s /N.sub.0 is the channel signal-to-noise ratio and log.sub.10 e is approximately equal to 0.434.

Abstract: A novel receiver for subcarriers in a radio broadcasting system is described, in which the characteristic frequency of the mixing oscillator is varied under program control. An incoming signal from antenna 1 passes through an input stage 2 to a mixing stage 3. Mixing stage 3 receives the output of an oscillator 4. The output of the mixing stage passes into an intermediate frequency filter stage 5, which preferably includes A/D converters 13 and demultiplexers 14. Stage 5 feeds a plurality of demodulators 6, which may include equalizers 12. Buffer memories 7 store information from demodulated subcarrier signals, and feed an evaluation unit 8. Evaluation unit 8 has a first output which drives a speaker 9 and a second output which is applied to a memory 11. A control unit 10, connected to the output of memory 11, controls the frequency generated by mixing oscillator 4.

Abstract: In a method for generalizing the conventional Viterbi algorithm, in which the transition costs are formed in a metric increment unit (TMU) and adding, comparing and selection are performed in a succeeding add-compare-select (ACS) unit, the difference costs from two arriving paths are calculated for each individual state, the reliability information at the beginning of each path being set to the highest value. Then the reliability value of the path with the least costs is updated at the points where the information points differ from the competing path, updating being performed in accordance with a table, and where the prior value of the reliability information and the difference costs are inserted into the table as the new input values. Then this new value is taken from the table and is stored, together with hard decisions, as path memory, where storage can be in the form of fixed or floating point values.

Abstract: There are described apparatus and methods for producing time-varying of trellis-coded modulations, specifically, time-varying trellis-coded phase-shift-keying, to facilitate carrier phase recovery when the signal has been exposed to extraneous phase variations and noise.Typically, eight-phase-shift-keying (8-PSK), with rate 2/3 convolutional coding, is followed on a repetitive basis by one or two formats of four-phase-shift-keying (4-PSK), which formats are chosen to ease phase synchronization and to conserve the use of bandwidth and not to worsen the bit error probability while reducing the probability of synchronization loss and the length of error bursts or "random walks".The variation of the modulation formats could be:(1) 8-PSK (rate 2/3) followed by 4-PSK,(2) 8-PSK (rate 2/3) followed by 4-PSK (preferred format) and then 4-PSK (secondary format) or,(3) any of many other periodic formats of 8-PSK and 4-PSK sections.

Abstract: A sequential decoder for error correction on burst and random noise channels using convolutionally encoded data. The decoder interacts with a deinterleaver which time demultiplexes data from a data channel from its time multiplexed form into a predetermined transformed order. The decoder includes a memory for storing a table of likelihood values which are derived from known error statistics about the data channel such as the probabilities of random errors and burst errors, burst error severity and burst duration. The decoder removes an encoded subblock of data from the deinterleaver and enters it into a replica of the convolutional encoder which calculates a syndrome bit from a combination of the presently received subblock together with a given number of previous subblocks. The syndrome bit indicates if the current assumption of the path through the convolutional tree is correct.