Abstract: A multiplexed signal transmission system according to the present invention has a transmission section which includes an input for receiving a group of square pulses having a fixed phase relation to each other, a first generator for generating edge pulse trains containing all edges extracted from the square pulses in the phase sequence, a second generator for generating edge attribute information representing an attribute of edge following after a prescribed edge in the same edge pulse train, a converter for converting a plurality of parallel data composing of the edge attribute information and mode information for controlling a system status into a serial data, an aligner for aligning the serial data corresponding to the edge pulses after the edge pulses, a third generator for generating a four-level signal having a reference signal level, a first level associated with clocks for the serial data, a second level associated with the serial data superposed on the clock,and a third level associated with the edge

Abstract: In a digital transmission system including a transmitter (2) coupled via a channel (4) to a receiver (6) a detection signal r.sub.k is compared with a number of reference values to determine the destination symbols a.sub.k. Since the size of the received signal r.sub.k is not known in advance, the ratio between the detection signal and the reference values is to be determined by an adapting circuit (16) on the basis of the received signal and the decisions made. The problem may then occur that as a result of an initially erroneous value of the ratio between detection signal and reference values not a correct adaptation is made. By recognizing such a situation because specific values of the symbols a.sub.k are lacking, in such a situation said ratio can be brought to such a value by the correction circuit (18) that all the values of a.sub.k again occur.

Abstract: Digital signals, such as digitized television signals, are subjected to a source coding step followed by a channel mapping step. The source coding step causes the television signal to be represented by two or more data streams while, in the channel mapping step, the mapping is such that the data elements of the various data streams have differing probabilities of being erroneously detected at the receiver. In preferred embodiments, a first one of the aforementioned data streams carries components of the overall television signal which are regarded as the most important--for example the audio, the framing information, and the vital portions of the video information, such as motion compensation information--and that data stream is mapped such that its data elements have the lowest probability of error.

Abstract: A communications system simultaneously transmits both a primary data signal and a secondary voice signal in such a way that the dynamic range of the secondary voice signal is increased even though deliberate errors are introduced into the transmitted data portion of the signal. In particular, the communications system includes an error correcting technique like channel encoding and the constellation signal space is divided into a number of regions, where at least one of the regions overlaps with another region. The primary signal is channel encoded to select a particular one of the number of regions, the region being represented by a reference signal point value. The voice signal is encoded to provide a signal point vector, which is added to the reference signal point in such a way that the resultant signal point is located in the overlapping region thereby deliberately introducing an error into the resulting transmitted signal point stream.

Abstract: Convolutionally encoded information subjected to channel intersymbol interference is decoded by calculating the minimum cost path through a trellis. The trellis terminates in known states. Exploiting the open architecture of the coprocessor, the minimum cost state is checked to ascertain if it is the known, that is, correct state and if it is not, the possible known states are searched by the DSP inside the ECCP active register and the state with the lowest cost amont the possible states is selected.

Abstract: An outer symbol error correcting code is concatenated with a punctured multidimensional trellis code to provide an optimal scheme for communicating digital television signals in a standard (e.g., approximately six MHz) bandwidth channel via a cable television network or the like. An input signal is encoded using an outer symbol error correcting code to produce successive blocks. Each block comprises N seven-bit coded symbols of which M represent information to be communicated and the remaining N-M coded symbols comprise error correcting information. M/N is either 120/126, 121/127 or 122/128. The blocks are interleaved, and may be supplemented with control symbols that include a synchronization pattern for M/N=121/127 or M/N=122/128. The interleaved blocks are convolutionally encoded using an inner trellis code having a punctured rate 4/5 (sixty-four QAM) or 3/4 (sixteen QAM). The output symbols are multilevel modulated for transmission over a communication path using, for example, sixteen or sixty-four QAM.

Abstract: A simultaneous voice and data modem performs "voice-activated" data rate changes to improve the transmission quality of the voice signal. In particular, when the simultaneous voice and data modem detects that a local telephone set has gone "off-hook," the simultaneous voice and data modem selects a signal space with a lower symbol density, which, although resulting in fewer bits per symbol, provides for a higher quality voice transmission.

Abstract: A multi-level superposed amplitude-modulated baseband signal processor which has simple hardware structure and a filtering effect for bandwidth and power efficiency in a digital transmission system includes a data delayer, a signal level converter, an operator, two pulse generators, two adders and two amplifiers, thereby eliminating the need for conventionally required pulse waveforms and simplifying circuit structure. Specifically, when the number of the multi-levels is desired to be changed, the relevant multi-level superposed amplitude-modulated baseband signal can be provided by a simple change of the processor.

Abstract: A digital exciter (30) for selectively modulating digital or analog input data. The digital exciter includes a digital signal modulator (32) and a digital quadrature modulator (DQM)(36) comprising two digital signal processors (DSPs). The signal modulator is controlled by a control (40). An operator can selectively determine whether the digital exciter is used for modulating either two level or four level NRZ digital data and whether the device is to provide linear modulation or frequency modulation (FM) of the input signal. An interpolator (38) interpolates a 662/3 kHz timer interrupt rate used in the signal modulator to a 400 kHz rate, thereby reducing the processing load on the DSP comprising the DQM by simplifying the sine and cosine values used in the quadrature modulation. An operator can select from among a plurality of operating parameters on a menu for controlling the signal modulator, either from a local or a remote video display terminal (VDT).

Abstract: Multilevel coded modulation equipment includes a transmission unit and a reception unit. The transmission unit includes a first converting unit, a first encoding unit, a first differential encoding unit, a second encoding unit, a mapping unit, and a modulating unit. The reception unit includes a demodulating unit, a first decoding unit, an inverting unit, a phase shifting unit, a second decoding unit, a differential decoding unit, a decision unit, and a second converting unit. The first converting unit distributes an input serial digital signal to a plurality of levels containing a level 1 indicating a level which is transparent to a 90.degree. phase ambiguity, and a level 2 indicating a level which is transparent to a 180.degree. phase rotation. The second converting unit receives outputs from the inverting unit, the differential decoding unit, and the decision unit, multiplexes the received signals into a serial digital signal, and outputs the serial digital signal.