Abstract: A communication system comprises a transmitting apparatus and receiving apparatus for transmitting/receiving a N-ary signal, based on a prime number exceeding 2, inclusive of an efficient error correction system. The transmitting apparatus includes a binary to N-ary converting unit for converting a binary transmit signal into an N-ary signal, as an information sequence, where the N of the N-ary number is a prime number exceeding 2, an encoding unit for generating a transmit sequence, comprised of BCH code on a Galois field with the number of elements being a prime number exceeding 2, and a multi-level modulating unit for multi-level modulating the transmit sequence and for transmitting the multi-level modulated transmit sequence to a receiving apparatus.

Abstract: The invention relates to a method and apparatus for implementing the training phase of adaptive channel equalization on a digital communications path passing signals modulated using QAM or CAP in a system configuration where the transmitter or the receiver or both of them include bandstop filters that form at least one stop band on the signal spectrum. In the method, the training of the adaptive equalizers is performed utilizing a sparse symbol constellation, wherein the number of symbol states (S) is reduced from that of the symbol constellation used in the normal data transmission state. The benefit of the sparse symbol constellation is that the strong intersymbol interference caused by a stop band falling on the signal spectrum can thus be reduced to such a low level in regard to the signal power that a linear equalizer may be used to reach a situation, wherein the proportion of correct symbol recovery decisions becomes sufficiently high for the training of a decision-feedback equalizer.

Abstract: A data transmitting/receiving apparatus and method for improving the reliability of data bits in a CDMA mobile communication system. High-priority bits are mapped to a high-reliability bit position and low-priority bits, to a low-reliability bit position in symbols. Thus system performance is improved at a transmission.

Abstract: Techniques for transmitting and receiving signals using a linear propagation channel, and the detection and decoding of the signals, are described. The symbols are decoded by computing the likelihood of each bit in a block of data in light of all blocks of received complex data and the constraints imposed by the channel code. Extrinsic information and a priori information are exchanged in an iterative fashion until desired performance is achieved. Extrinsic probability values are computed by searching through hypotheses in the constellation of available symbols to maximize the extrinsic probability values, with decoding employing a stored list of candidate points for discovered within a search radius, the list comprising the solution points found within the smallest radii.

Abstract: A method and apparatus for detecting and decoding multiple or single users in a TDMA system where multipath propagation is present. A TDMA receiver may receive a one dimensional TDMA signal stream and may include a maximum likelihood sequence estimation (MLSE) stage to detect users from the received one dimensional TDMA signal stream. A decision feedback equalizer receives the postcursor portions of the TDMA channel from a channel estimator and an estimate of the postcursor portions of the transmitted signal from the MLSE stage. The decision feedback equalizer (DFE) truncates the interference in the received TDMA signal stream by cancelling the postcursor portion of the channel. The MLSE stage operates on the truncated TDMA signal stream to detect users.

Abstract: A method and apparatus for producing a variable rate precoded signal are presented in which a variable rate encoder receives a rate control signal and a data signal and generates a constellation size signal and data symbols. The data symbols and constellation size signal can be used by a precoder to produce a variable rate precoded signal. The precoder can be a Tomlinson/Harashima-Miyakawa precoder which uses the constellation size signal as part of the quantization process. The system can also be used to generate a variable rate modulation encoded signal. The invention provides the ability to create a variable rate signal which can be precoded and to which error correcting codes can be readily applied.

Abstract: A transmitter transmits, and a receiver receives, a data frame is transmitted into an 8 MHZ channel. The data frame contains a plurality of data segments, where each of the data segments contain DS symbols. The DS symbols include data symbols, priming symbols, and segment synchronization symbols. The transmitter trellis encodes the data symbols, priming symbols, and segment synchronization symbols. The receiver trellis decodes the 10 data symbols, priming symbols, and segment synchronization symbols. The data frame also contains a mode control ID which the receiver uses in trellis decoding the data symbols, priming symbols, and segment synchronization symbols.

Abstract: A QAM modulation system capable of setting a number of multilevel to approximate 2(p+0.25) (p is an integer equal to or more than 3) or 2(p+q/n). An input data signal of 4p+1 bits are converted into four signals of p+1 bits, there being a predetermined relationship between the input data signal and the converted signals. The converted four signals are assigned to four phase planes, respectively. The four signals are time-division multiplexed and multilevel-modulated. Thereby, it becomes possible to set the number of multilevel to approximate 2(p+0.25).

Abstract: A multilevel coded modulation scheme is provided in which a first portion of input data is encoded by a first-level code and a second portion of input data is encoded by an second-level code, the second-level code being such that the overall multilevel code exhibits a desired level of time diversity of at least 2 and the minimum distance of the overall code is not increased by virtue of the presence of the second-level code.

Abstract: A method of coding a signal for digital optical communication using a symbol formed of N slots [s1, s2, s3, . . . sN], wherein si is either 0 or 1 where i is an integer and l≦i ≦N is provided. The method includes the steps of determining a plurality of symbols which satisfy the following expression, wherein k is an arbitrary positive integer, and p1, q1, p2, q2, . . . , pk and qk are integers which satisfy 1≦p1<q1, 1≦p2<q2, . . . , 1≦pk<qk, and p1/q1<p2/q2<. . .

Abstract: A multi-carrier transmission system such as a DMT based VDSL system. The system uses orthogonal carriers with high order QAM constellations for the transmission of multiple bits per carrier and symbol. This estimate includes digital receiver and transmitter units with the receiver unit including a symbol detection unit. This system is adapted to determine a parameter for each single carrier with the parameter being indicative of a deviation of a received signal from a corresponding constellation point. It compares the parameter with an upper lower limit and if the parameter is outside the limits, changes the constellation used to modulate the carrier to a neighboring constellation. The symbol detection unit may be used to determine a parameter such as the ratio d2/&sgr;2, where d is the shortest distance between neighboring constellations, &sgr; is a standard deviation and &sgr;2 is the variance of the deviations of the input and output signal values of the symbol detection unit.

Abstract: A multi-carrier transceiver, such as a DMT-based ADSL transceiver, has separate processing paths for different information types, such as voice, data, video, etc. Each processing path can include separate scrambling, interleaving, bit loading or tone ordering, and constellation encoding. In this manner, specific bit loading or tone ordering can be performed for each of the different information types, such that transmission carriers are selected for optimal bit rates and error rates.

Abstract: A communication system decoder in which branch metrics are represented using linear distance. An illustrative embodiment for decoding a sequence of received symbols of a QPSK or QAM constellation includes a branch metric calculation unit, an add-compare-select unit, and a traceback unit. The branch metric unit computes branch metrics associated with transitions between states of a multi-stage trellis representation of a state machine. In accordance with the invention, each of the branch metrics correspond to a linear distance between a given one of the received symbols and its nearest codeword in a given stage of the trellis. The add-compare-select unit utilizes the branch metrics of a current stage, along with a previously-generated path metric, for comparison purposes in determining a survivor path and corresponding updated path metric for a current stage of the multi-stage trellis. The traceback unit utilizes the updated path metric to generate a corresponding decoded output.

Abstract: Enhanced slice prediction is based upon ATSC VSB data when robust 8 VSB data are not available and is based upon robust 8 JSB data when robust 8 VSB data are available.

Abstract: A transmitting circuit apparatus has a first digital modulator and a second digital modulator for modulating an I signal and a Q signal which are multi-valued digital baseband modulation signals, into a digital I signal and a digital Q signal, respectively, having the number of bits smaller than that of the baseband modulation signals; and a quadrature modulator for outputting a signal synthesized from the signals generated by modulating (two) carrier waves each having a phase perpendicular to each other by using the modulated I and Q signals, respectively.

Abstract: A transmission device that transmits a signal along a link and method therefor that includes a forward error correction encoder unit to insert error correction information into the signal transmitted along a link and output a corresponding encoded signal. A modulation unit variably modulates the encoded signal and outputs a modulated signal, having a corresponding quadrature amplitude modulation index, to the receiving device. A control unit variably controls the inserted forward error correction information and the quadrature amplitude modulation index based on link quality information with respect to substantially the entire link to increase throughput during periods of reduced environmental degradation.

Abstract: There is disclosed a digital modulator whose modulation parameter can be controlled and in which modulation data or modulated signals are prevented from generating interference signals with adjoining circuits through control when power supply is turned on or system is changed. The digital modulator has a device for detecting that the power supply is turned on, and the transmission data is modulated with fixed data in response to an output of the detecting device for a time required for completing a required system constitution setting. The digital modulator also has a device for detecting the presence of the control for changing the system after the power supply is turned on. In response to an output of the detecting device, modulation is performed with the fixed data for a time from the start till the completion of the setting with a predetermined time added thereto.

Abstract: Techniques for identifying an improved bitloading assignment for a multicarrier communication channel are provided. Generally, bit loadings of the sub-channels are equalized (either completely or partially) by selectively decrementing high bitload sub-channels until a desired degree of equalization between the sub-channel bit loadings is achieved. By reducing the bit loading of high bitload sub-channels relative to other sub-channels, the communication channel is effectively desensitized to non-stationary noise.

Abstract: The subtracter performs subtraction processing between a pointer outputted from the pointer register and code words candidate outputted from the code word count storing circuit, and in accordance with whether the result is negative or positive, determines the code words of input data words. Code word candidates stored in the code word count storing circuit are created according to a finite-state transition diagram stored in the state transition storing circuit. An encoder and a decoder are thus made compact and faster.

Abstract: Encoding and decoding systems and methods for digital data in 24 bit sequences. An encoder generates state variables as a function of four or fewer bits of the 24 bit sequence, and encodes the sequence into 11 and 14 bit codewords. After transmission, the 11 bit and 14 bit codewords are decoded using recovered state variables. The encoding places a run length limit (RLL) of k=7 on a 25 bit codeword comprised of the 11 and 14 bit codewords to limit runs of zeros. Each of the 11 bit and 14 bit codewords are preferably also encoded with a run length limit of interleaved bits is i=7. The encoding and decoding systems and methods can be applied to a magnetic disc drive.

Abstract: QPSK modulated quadrature baseband signal generating section 301 generates a QPSK modulated quadrature baseband signal. 8 PSK modulated quadrature baseband signal generating section 302 generates an 8 PSK modulated quadrature baseband signal. Based on the modulation scheme determined information, in-phase component switching section 304 and quadrature component switching section 305 switch between the QPSK modulated quadrature baseband signal, 8 PSK modulated quadrature baseband signal and pilot symbol to output to radio section 306. Radio section 306 performs the predetermined radio processing on the baseband signal to output a transmission signal. The transmission signal is amplified in power amplifier 307, and the amplified transmission signal is transmitted from transmission antenna 309. It is thereby possible to take into account both the improvement in the data transmission rate, and the benefit and convenience in terminals.

Abstract: The invention includes a method of identifying an extremum value and an index in a group of values where each value has an associated index. A count register is initialized to an initial count. A value from the group as well as a predetermined value are provided simultaneously to an arithmetic logic unit and a multiplexer. The value from the group and the predetermined value are compared in the arithmetic logic unit. A selector is set to one of a first or second logic state. In the first logic state the selector selects a minimum; in the second logic state the selector selects a maximum. One of the value and the predetermined value are selected as an extremum based on a flag set by the comparison in the arithmetic logic unit and the selector. The predetermined value is replaced with the extremum and the count register count is stored when the selector is set to a first state and the value is less than the predetermined value.

Abstract: A distortion compensating device provided in a receiver for compensating distortion which is added to a signal in a transmission path. The signal is generated in a multi-level modulator of a transmitter in which a digital signal is mapped to one of a plurality of specified signal points in a signal space diagram. The device includes a signal-point-position averaging circuit for producing an average signal point for each of a plurality of distributions of received signal points in the signal space diagram. A discrimination circuit in the device discriminates the average signal point closest to a received signal point from other average signal points in the signal space diagram.

Abstract: A first group of bits (100, 102, 106), e.g., header symbols/bits, are interleaved to form a first group of interleaved bits. A second group of bits (104), e.g., data symbols/bits, are interleaved to form a second group of interleaved bits. The first and second groups of interleaved bits are mapped to an information burst (114). The first and second groups of interleaved bits may be mapped to the information burst relative to a group of known symbols (116) forming a training sequence. A disadvantaged bit location, i.e., a bit location within the mapping having a relative high probability of incurring a bit error, is identified and an advantaged bit location, i.e., a bit location within the mapping having a relatively low probability of incurring a bit error, is identified.

Abstract: A method and a system for decoding information signals encoded by a multi-state encoding architecture and transmitted over a multi-dimensional transmission channel by computing a distance of a received word from a codeword. One-dimensional (1D) input signals are detected in a symbol decoder, implemented using look-up tables, to produce a pair of 1D errors, with each representing a distance metric between the input signal and a symbol in one of two disjoint symbol-subsets. The symbol decoder is implemented as a pair of slicers, each detecting an input signal with respect to one of two disjoint symbol-subsets. A third slicer detects the input with respect to the union of the two disjoint symbol-subsets. Decisions from the first, second and third slicers are processed to define 1D square error terms expressed in Hamming metrics. Reduced bit count error terms allow follow-on error processing to be performed with a minimum of computational complexity.

Abstract: The mobile telephone detects bad data packets by decoding speech parameters represented by the packets and comparing those speech parameters against acceptable ranges of speech parameters. If the speech parameters do not lie within the acceptable ranges, the packets are discarded. This speech parameter-based detection of bad data packets is particularly useful in mobile telephones receiving variable rate data packets wherein an error in determining the rate of a packet results in the entire packet being decoded at an incorrect rate, thereby likely causing an annoying audible artifact in the decode speech signal. Such rate detection errors can occur even though a CRC or other conventional error detection check fails to detect the bad packet. In an exemplary implementation, the mobile telephone receives signals encoded with TIA/EIA/IS-95-A standards.

Abstract: An automatic gain control (AGC) system that monitors the distortion of the outer constellation points of a complex modulation format such as quadrature amplitude modulation (QAM) and adjusts both the RF and IF AGC gain to minimize such distortion. In particular, the receiver contains at least two stages of AGC gain. Typically, the RF AGC amplifier is contained in the tuner that is followed by an IF AGC amplifier. The IF amplifier is coupled to a mixer and an associated low pass filter which, in combination and when driven by a particular frequency, produces a baseband (or near baseband) signal, The baseband signal is digitized and processed by a gain control circuit. The gain control circuit produces IF and RF AGC signals that control the gain of the respective AGC stages.

Abstract: A system and method for the transmission of additional special marker symbols in a circular signal space constellation allows the communication of additional control information without requiring any additional power to transmit the additional symbol. Additional symbols can include "Start of Message", "End of File", "End of Transmission", "Increase Data Rate", "Decrease Data Rate", "Save State" or "Clear", or any additional command signal desired to be transmitted.

Abstract: A method of demodulating voice or data and control information in systems that support multiple modulation schemes modulates voice or data using a first linear modulation scheme, such as 16QAM modulation scheme, and modulates control information using a second linear modulation scheme, for example, QPSK modulation scheme, that has the same symbol rate as that of the first modulation scheme. The first linear modulation scheme has a higher modulation level than the second linear modulation scheme. Information modulated using the second linear modulation scheme, which uses a reduced signal set of the first linear modulation scheme, are demodulated using the same demodulator that is used for demodulating information modulated using the first linear modulation scheme. Also, in-band signalling information within a traffic channel, such as stealing flags, are modulated using the second modulation scheme.

Abstract: An improved squelch circuit and methodology for a multi-level quantizer employing one or more amplifiers to amplify an input signal at different gains. Comparators coupled to corresponding amplifiers or amplifier stages produce pulses based on comparing the amplified signals with a common reference potential. Digital delay lines coupled to the comparators repeatedly delay the pulses.

Abstract: An adaptive gain algorithm allows the maximization of gain of an audio signal that is transmitted with a digital data signal by allowing a trellis decoder to compensate for occasional excursions of the audio and noise signal across a signal space boundary. By measuring the short term energy present in an audio signal, the algorithm of the present invention allows the maximum power to be used to transmit an analog signal without overloading the trellis decoder.

Abstract: A receiver for receiving a cable and terrestrial digital signals of differing VSB modes where the data levels of the various signals have a desired relationship that enables simple data level slicing and error determination. Some of the signals have sync levels that do not conform to the desired relationship and the receiver includes a comb filter for reducing interference when receiving an 8VSB terrestrial signal. The mode of the received signal is determined and a correction factor is applied to the syncs of the signals as needed to reestablish the desired relationship. Operation of the comb filter results in additional levels and a disruption of the desired relationship. For such cases, the comb filtered data levels are modified to make them a subset of the VSB 16 data levels. The modifications are accomplished in feedback paths of the phase tracker after the circuit equalizer and do not affect the data levels passed to the next stage.

Abstract: In a method for realizing carrier wave synchronization in the receptio of a multi-level, two-dimensional modulation signal, the received signal is demodulated by using at least one local oscillator (3) in order to generate the local oscillator frequency. In the method, the local oscillator (3) performs a frequency scanning within the frequency range of the reception; during the frequency scanning, a demodulated signal point system is formed of the received signal by using the frequency generated by the local oscillator (3). Furthermore, the demodulated signal point system in the method is examined in order to determine at which point of time the frequency of the local oscillator is synchronized to the carrier wave frequency of the received modulation signal.

Abstract: VSB data is transmitted in a frame which includes a frame sync, a segment sync, a mode control, and a plurality of data symbols. The mode control indicates the number of modulation levels of the data symbols and includes 2-level symbols forming the following byte: PABCPABC. P is a parity bit, and ABC represents a selected one of a plurality of data constellations defining the modulation levels of the data symbols.

Abstract: A improved multilevel encoder and associated method is described. The encoder includes a device (e.g., serial to parallel converter) for presenting a plurality of information bits in parallel format. A symbol selector having a plurality of inputs and an output, the symbol selector being configured to output a symbol that is defined by a signal constellation, whereby the symbol is defined by a magnitude and phase that are uniquely associated with a state of the plurality of inputs. A first encoder has an input and an output, the input of the first encoder being associated with at least one of the outputs of the device and the output being associated with at least one of the inputs of the symbol selector, the first encoder configured by a code defining a four-way set partition of the signal constellation.

Abstract: The invention concerns a method of controlling the minimal distance between successive errors in digital radio transmissions when multilevel modulations are used. With such a method the errors are spaced according to the needs, with an extremely reduced use of hardware with respect to prior art techniques. The method is characterized in that, in transmission a differential delay, i.e. different from flow to flow, is applied to each parallel flow not yet modulated, and in reception a differential delay is applied to each demodulated flow in such a way that the overall delay applied to each flow, i.e. the sum of the delay applied in transmission and the delay applied in reception, is constant and equal for all the flows.

Abstract: The level of a symbol information in a symbol-sync part transmitted for the purpose of synchronizing a receiver of a digital radio communications system reflects the state of the concurrent transmission. With this factor taken in account, a symbol determining method is provided which comprises the steps of receiving a symbol information extracted from a symbol-sync part of a received signal obtained by demodulating a received wave and digitizing it; generating thresholds for use to determine the value of the received symbol based on the reception level of the symbol information; determining the value of the received symbol in the data part of the received data based on the thresholds; and reproducing the symbol. Therefore, even if a received symbol is deteriorated due to a degradation, etc. of transmission line, a symbol determination can be done with no degradation of the signal reception due to a narrowing of noise margin, etc.

Abstract: A method and apparatus for decoding a signal in the presence of linear or nonlinear interference, correlated noise or a combination thereof. The method involves a concatenated decoder comprising an inner decoder and a postprocessor. N most likely paths are generated by the inner decoder, or a combination of the inner decoder and an error event generator. These paths are then presented to the postprocessor which computes metrics for each path based on information about the signal, not considered by the inner decoder. These metrics can be based on linear or nonlinear model of the channel and optionally, a noise whitened signal for noise decorrelation. The path with the best metric is selected as the concatenated decoder output. The postprocessor can also be implemented in the presence of channel codes. It is also shown that the postprocessor is especially suited for a trellis implementation. When applied to magnetic recording channels, the method of the present invention allows for increased recording capacity.

Abstract: A high power RF transmitter that uses high power modulators that perform quadrature amplitude modulation (QAM) on a carrier signal after power amplification that is performed in the RF carrier source. The present invention transposes the locations of the modulators and power amplifier, and thus directly modulates a high power carrier signal. An RF carrier source generates a high power RF carrier signal that is split by a power splitter. A lookup table containing 2.sup.B words by K bits receives transmit data and mapping data and generates K-tuple modulating data. A plurality of phase key modulators are respectively coupled to outputs of the power splitter and to the lookup table and phase key modulate each of the signal components of the carrier signal using the K-tuple modulating data. A power combiner is coupled to outputs of the phase key modulators for outputting a high power QAM constellation from the transmitter.

Abstract: An encoder for encoding binary data bits supplied by a data source into pulse amplitude modulated multilevel symbols. The encoder includes a bit stuffer for receiving the data bits from the data source at a first data bit rate, which at most equals a maximum data bit rate. The bit stuffer then adds descriptive bits to the data bits at a descriptive bit rate, which at most equals a maximum descriptive bit rate. The encoder also includes a multilevel pulse amplitude modulator for receiving the data and descriptive bits from the bit stuffer and for converting the data and descriptive bits into pulse amplitude modulated multilevel symbols. When these multilevel PAM symbols are transmitted, they have a spectral energy characteristic which is below a predetermined low level threshold at a predetermined baseband bandwidth frequency. In addition, these multilevel PAM symbols have a symbol rate (i.e.

Abstract: For demodulation of higher-level MQAM signals without knowledge of the transmitted symbols, the clock phase error is calculated first after the sampling of the baseband signal with a clock frequency corresponding to the MQAM signal, and the corresponding time shift of the baseband signal is compensated therewith by interpolation (clock synchronization). Subsequently, the carrier frequency deviation and the carrier phase deviation are calculated feedback-free according to the principle of the maximum likelihood theory using Fourier transformation or by convolution in the time domain, and thus the data sequence is compensated.

Abstract: An Ethernet-type local area network having multiport repeaters and nodes within a specified distance of the hub is able to communicate high speed digital data over multiple pairs of twisted-pair wires using long symbol group-type ternary coding. Bundle mode termination minimize impedance mismatches. Low-frequency collision detection circuitry permits detection of packet collisions on an a.c.-coupled network. Precise serialized digital to analog conversion is realized using chains of gates to form delay elements with precise delays.

Abstract: A system for reproducing data recorded on a magnetic recording medium at high density is provided as a simple configuration. Quadripartite reproduction data is output from a Viterbi detection circuit to an adder, which then subtracts the quadripartite reproduction data from a signal before PR4-ML method data determination. An adder is used to perform a (1+D) process for the result. An error signal pattern detection circuit performs maximum likelihood estimation for an PR4-ML method detection error. Further, when a detected determination error matches an actual reproduction data string, a data correction circuit corrects the reproduction data string.

Abstract: A method and an apparatus is provided for a multi-level quadrature amplitude modulation system, in which the DC level of the output is "0" even when the modulation multi-level number is varied and mean electric power becomes almost the same. The multi-level quadrature amplitude modulation system is capable of modulating at different modulation multi-level numbers. The method of operating the system includes the steps of converting all of the input bit numbers into the same bit number based on a prescribed conversion rule for each orthogonal channel irrespective of the modulation multi-level number of the system, filtering the converted signal by a digital filter, converting the output of the digital filter into an analog signal by a D/A converter, and modulating the analog signal by a quadrature modulator.

Abstract: Source symbols are encoded for use in a higher level modulator by partitioning the source symbols into a number of classes. This principle is applied in a number of alternative transmitter and receiver embodiments. In one embodiment, a corresponding encoder is provided for each of the classes, and for each class, each of the source symbols is supplied to the corresponding encoder. For each encoder, coded symbols are supplied at an encoder output and the coded symbols are partitioned into a number of levels associated with the corresponding class, wherein at least one of the classes has at least two levels assigned to it. The partitioned coded symbols are then supplied to a mapper that generates amplitude coefficient signals. Corresponding receivers perform inverse operations to those performed by the transmitters.

Abstract: A transmission system is disclosed which permits the receiving end to demodulate multi-valued modulated symbols successfully under fading conditions and reduces the amount of transmitted reference data to improve data transmission efficiency. At the transmitting end, a multiplexing section, a modulating section, and a transmitting section are provided. In transmitting an OFDM transmission frame, null symbols and reference symbols are placed in the beginning portion of the frame and QPSK symbols are placed in an information symbol data region in the frame with equal spacings in time and frequency. At the receiving end, a receiving section, a demodulation section, an equalizing section, and a demultiplexing section are provided. An error detector detects amplitude and phase errors of each carrier from the reference symbols, and a variation detector detects variations in the amplitude and phase of a received signal from the QPSK symbols.

Abstract: A quadrature amplitude modulation demodulator for receiving a quadrature amplitude modulated signal having a suppressed pilot signal. In the demodulator, a receiver unit converts received quadrature amplitude modulated signal into a frequency converted signal and a signal at a phase 90 degrees shifted from this frequency converted signal. A synchronous detector unit performs synchronous detection on the signals outputted by the receiver unit by detecting a frequency difference between a carrier of the frequency converted signal and a reference signal. Then, a phase detector unit performs phase detection on the synchronous detected signals by detecting a phase difference included in the synchronous detected signals. A detector unit detects transmitted data from the phase detected signal.

Abstract: Method and apparatus for efficient encoding of symbols with multilevel encoding, where components of the symbols that are more susceptible to errors are encoded more robustly than components that are less susceptible to error. A non-binary constellation of symbols is handled with a fractional bit rate converter that combines with the multilevel encoder to create an effective and efficient constellation of symbols. Illustratively, digital data is encoded and mapped onto a set of symbols, with the two least significant bits of the symbols being encoded with a multi-level code. The least significant bit is encoded with a code that is more robust than the code of the next-to-least significant bit, in recognition of the fact that errors in the least significant bit are much more likely. The most significant bits are mapped with the aid of a fractional bit rate mapper that optimizes a selected aspect of the symbol constellation, such as average power.

Abstract: In a transmission system or a recording systems often codes are used to make the coded signal (C.sub.k) DC free. To simplify the detector (16), block codes can be preferable. To exploit the redundancy inherently present in such a code a symbol wise Viterbi detector (24,26) is used to detect the symbols without largely enlarging the complexity of the system.

Abstract: A communication system (100) encodes and decodes information utilizing at least four modulation levels for transmitting the information as symbols representing symbol bits in symbol bit positions. At least one of the symbol bit positions exhibits an error rate higher than that of another of the positions. A processor (204) encodes (702) the information into an even number of code words and transmits the code words as an interleaved data stream. The processor (204) rearranges (706, 708) the transmission order of the code word bits in a predetermined way to form a modified transmission order such that the code words are transmitted (710) with substantially equal error rates. A receiver (110) receives and demodulates (712) the interleaved data stream to derive the code word bits, and then reorders (714, 716) the code word bits to undo bit modifications resulting from the modified transmission order, thereby restoring the code words. The receiver then decodes the code words to recover the information.