Abstract: A format programmable hardware packetizer (110) receives real-time raw input data (125) from a multimedia data source (103) via an analog to digital converter (105) and a data encoder (120) gated by encoder interrupts (127). The real-time raw input data is buffered in an internal byte collector of the packetizer (110). A main CPU interrupt (117) is issued to the main processor (130) when a packet boundary code is received. The packetizer (110) formats the data according to a desired format selected on line (115) for dump to the main memory (140) while providing a managed, much lower level of interrupts to the main processor (130) on the CPU interrupt line (117). A plurality of hardware packetizers (110) can be deployed according to alternative constructions for efficient real time packetizing in various selected formats.

Abstract: A receiver and a phase extraction circuit are capable of demodulating at high resolution if the sampling frequency is close to the frequency of received signal. In the phase extraction circuit, the received signal modulated in phase is sampled when lowered to an intermediate frequency. When the sampling frequency at this time is selected around the intermediate frequency, a continuous portion appears in one position of the sampling data row. The position of the continuous portion is determined by the phase of the received signal, and therefore a one-to-one correspondence table of the continuous position and phase of received signal is prepared. By detecting the continuous position, the phase information can be obtained from the table. As a result, it is possible to demodulate directly at the intermediate frequency, and therefore the circuit scale is substantially simplified, the number of parts is curtailed, and the size is reduced.

Abstract: A device for detecting a predetermined waveform in a received signal and synchronizing the detected waveform to the predetermined waveform is disclosed. The device includes a memory element for storing a reference set of encoded values. The reference set representing an encoded version of the predetermined waveform. An encoder is used to PCM encode the signal to obtain sets of encoded values representing the received signal. A processor calculates the statistical correlation coefficient of the reference set and the signal sets. The processor then determines the maximum statistical correlation coefficient. The predetermined waveform is detected in the signal if the maximum statistical correlation coefficient is greater than or equal to a predetermined threshold value. The device provides a compact, inexpensive, and fast method for detecting a known reference waveform in a received signal.

Abstract: A pilot signal detection method and a receiver, in which a search window having a predetermined time width is generated at every substantially constant time interval, and pilot signals existing in search window thus generated are detected. The position of the search window of each period is set in accordance with the delay amount between the timing (T_ref) of the first pilot signal and the timing (T_last) of the last pilot signal detected in the immediately preceding search window.

Abstract: The invention relates to a wireless network which includes at least one base station (1 to 3) and a plurality of associated terminals (4 to 14) for the exchange of useful data and control data. According to the invention, the base station (1 to 3) is arranged to transmit the starting instant of a signaling sequence to at least one terminal (4 to 14). In order to evaluate the signaling sequences transmitted by the terminals, the base station (1 to 3) includes a device (21, 22) for correlating a received signaling sequence and for detecting the pulse arising from a received and correlated signaling sequence.

Abstract: A system that measures a segment of a waveform by isolating the segment by virtue of gating. A waveform anomaly may be gated. The gated waveform is supplied to a plurality of frequency information extractors, which yield information regarding the frequency content of the gated waveform at individual frequencies. Distortion introduced into the gated waveform may be measured by applying the same gating function to a reference waveform. The system may measure or gate an incoming waveform at time intervals dictated by a clock signal recovered from the incoming waveform. A segment of the waveform to be measured may be circulated through a fiber loop, with a fraction of the circulated signal split off for presentation to a measurement system with each circulation. The point in time at which the waveform crosses a threshold may be determined by straddle sampling.

Abstract: A method of estimating SNR for a plurality of carriers modulated with digital information, wherein the digital information includes data baud and training baud, comprising the steps of: receiving the plurality of carriers; determining a first SNR for the data baud; determining a second SNR for the training baud; comparing at least one of the first and second SNRs to predetermined selection criteria; and selecting one of the first and said second SNRs based on the comparison step. In the preferred embodiment, the carriers are processed to produce an equalizer output for each of the carriers, and the equalizer output is processed to produce a symbol decision for each of the carriers. The equalizer output is subtracted from the symbol decision when a data baud is received to produce a first difference value, and the first difference value is squared to produce a first signal to noise estimate.

Abstract: The invention relates to a method of estimating the frequency offset of a packet of phase modulated symbols received with phase error, the method comprising: applying a phase correction to the symbols of the received packet for all possible pairs of frequency offset and phase offset; and selecting from said offset pairs, the pair which provides the most likely packet of corrected symbols, thereby determining the frequency offset of the received packet. Compared with known solutions, the invention makes it possible to reduce errors concerning estimated frequency. Advantageously, the method comprises a step of quantizing the possible phase corrections, thereby making it possible to reduce the complexity of the calculations to be performed, without degrading performance.

Abstract: A majority decision method for improved frame error rate in the digital enhanced cordless telecommunications (DECT) system. Specifically, one embodiment of the present invention includes a method for improving retransmission efficiency of a data frame within a communication system. The method includes the step of receiving and storing three corrupted versions of a data frame within a memory. Moreover, the method also includes the step of performing a byte-wise comparison of the three corrupted versions of the data frame to locate an inconsistent byte position. In response to locating the inconsistent byte position among the three corrupted versions of the data frame, the method includes the step of performing a byte-wise majority decision among the three corrupted versions of the data frame to select a correct byte value of the inconsistent byte position.

Abstract: A reception synchronization circuit for receiving a unique word transmitted in a predetermined digital pattern. A detection circuit detects the reception electric field intensity as received power. A UW correlation judgment circuit detects the unique word (hereinafter referred to as “UW”) and takes a correlation between the unique word thus detected and a predetermined digital pattern. A memory stores two or more threshold values for the movement average. After the two or more threshold values and the movement average are compared with each other, the correlation is taken by the UW correlation judgment circuit when the movement average is larger than the minimum values of the two or more threshold values.

Abstract: A method and communications receiver is disclosed that removes Doppler frequency shift in a spread spectrum communications signal. A pilot channel rake section has I and Q Doppler estimation channels for estimating the Doppler change in frequency based on a common pilot channel. A data channel rake section has I and Q data channels for receiving the Doppler change in frequency from the pilot channel rake section and canceling any Doppler error.

Abstract: A method and system that reduces the peak-to-average power ratio of a reverse link signal is described. A baseband structure implements a peak reduction technique using peak windowing. A non-rectangular window is used to distort the signal. One embodiment of the window is an inverted-raised cosine with the peak reduction a function of the relative difference in the squared-magnitude of the envelope relative to that of the desired peak-to-average power ratio. Multiple passes through the peak-reduction function may be performed until a desired target peak-to-average power ratio is achieved.

Abstract: An orthogonal frequency division multiplexed wideband communication system provides improved time and frequency synchronization by inserting an unevenly spaced pilot sequence within the constellation data. A receive correlates the received data using the unevenly spaced pilot sequence. The pilot sequence is generated with a maximum length pseudo random noise code and inserted into frequency bins having prime numbers.

Abstract: A system for detecting a burst in a wireless communications system. A signal strength indicator indicates the strength of an incoming signal representative of incoming packets. A signal strength change detector detects changes in the signal strength of the incoming signal. Signal strength detection logic determines if a change in signal strength of a predetermined magnitude has occurred. A pattern detector detects patterns of symbols, or symbol estimates, in the incoming signal to determine if a predetermined pattern of symbols is present. Burst detection logic signals detection of a burst if the signal strength detection logic determines that a change in signal strength of predetermined magnitude has occurred, and the pattern detector determines that a predetermined pattern of symbols is present.

Abstract: A data stream (DS) comprises a time multiplex of coded data (D) and control data (C). The data stream (DS) may be, for example, of the MPEG type representing a sequence of pictures. The coded data (D) is transcoded (T) so as to obtain transcoded data (DT) which differs in size from the coded data (D). The control data (C) is adapted for the transcoded data (DT) so as to obtain adapted control data (CA) which does not substantially differ in size from the control data (C). The transcoded data (DT) and the adapted control data (CA) are written into a transcoder output buffer (TOB) and read from the transcoder output buffer (TOB) so as to obtain a transcoded data stream (DST). This allows an efficient use of a transmission channel via which the transcoded data stream (DST) is to be transmitted and, consequently, it allows a satisfactory transcoding quality.

Abstract: A system and method for signal peak reduction in a multiple carrier communication system where the individual carriers are produced from input symbols that are filtered to reduce individual carrier bandwidths, offset in frequency, and combined into an output signal. A multiple carrier peak reduction unit is provided which modifies the input carrier symbols so that the combined output signal does not exceed a predetermined peak limit value. The multiple carrier peak reduction unit includes filter predictors that predict the effect of each channel filter on that carriers input symbols by using filter coefficient values corresponding to the impulse response function of each filter. The filter predictor outputs are then phase shifted, in correspondence to frequency offsets provided for in multiple carrier signal generation, and combined to produce a prediction of the combined signal output which is then processed to determine the corrections required to the individual channel symbol inputs.

Abstract: An innovative channelizer design methodology is provided to adjust the narrowband channel frequency spacing and processing algorithm in order to develop a configurable multi-rate channelizer (20) for multiple applications with different input data rates and input channel group bandwidths. Given an input and output sampling rate and the input channel group bandwidth, the input channel spacing, the discrete Fourier transform (DFT) size, the valid output DFT bins, the dead zone implementation including the number of samples to blank for each chip, which exact samples to blank, the timing error immunity versus performance degradation balance may be derived to design hardware implementation of a configurable multi-rate channelizer for use in applications with different input data rates and input channel group bandwidths.

Abstract: An apparatus for and method of converting soft symbol decision information into soft bit decision information that overcomes the disadvantages of the prior art. The invention is adapted to receive M soft symbol values where each symbol represents m bits (M=2m). The output for each symbol comprises m soft values of bits representing the symbol. The invention is operative to convert the soft symbol values to soft bit values using the log likelihood ratios (LLRs) of a bit and a symbol expressed as conditional probabilities. The method of the invention is presented which can be performed in either hardware or software. A computer comprising a processor, memory, etc. is operative to execute software adapted to perform the soft symbol to bit conversion method of the present invention.

Abstract: The present invention relates to a demodulator which receives a signal transmitted via phase modulation or multivalue QAM modulation, and decides transmitted data based on the received signal. The present invention enhances a transmission-line estimate by using tentatively decided data symbols as pilot symbols and in estimating a transmission line without a decrease in accuracy of transmission-line estimate even when an error rate of the tentatively decided data symbols is increased. The demodulator includes a pilot-based transmission-line estimation unit for estimating transmission-line characteristics by using pilot symbols. A tentative-data-decision unit for tentatively deciding data symbols based on the pilot-based transmission-line estimate. A data-based transmission-line estimation unit for estimating the transmission-line characteristics by using the tentatively decided data.

Abstract: Methods and systems are provided which utilize pilots in an information sequence to periodically retrain a channel estimator. Thus, a channel tracker may be synchronized using a synchronization sequence and then periodically retrained using known pilot symbols. Furthermore, the utilization of pilots may allow for the detection of errors in previous channel estimates. When errors are detected, a new channel estimate may be used based on the retraining using the pilot symbols and, optionally, previous errors in symbol estimation may be corrected. Thus, by retraining based on pilot symbols, the propagation of errors may be reduced.

Abstract: A receiving apparatus receives a digital broadcast signal having been modulated in an orthogonal frequency multiplexing method of which data of each frame is composed of a synchronous reference signal and transmission data and of which data is assigned to a plurality of carriers that are orthogonal to each other. A synchronous TFPR signal is transmitted every frame. An AFC (automatic frequency control) circuit receives the synchronous TFPR signal, and obtains a frequency error and a timing error of the received signal to control the frequency and the timing. To remove an influence of a multi-path to the synchronous TFPR signal, an equalizer is disposed. The influence of the multi-path to the synchronous TFPR signal is removed by the equalizer. Thus, the frequency and the timing of a carrier of the receiver side can be exactly controlled.

Abstract: Methods and apparatuses for iterative parameter estimation are described. The iterative parameter estimation includes performing a first estimation of a first portion of a signal to obtain first parameters of the portion of the signal, wherein the signal contains no known data symbols. The first portion of the signal is demodulated using the first parameters to recover data symbols. The demodulated first portion of the signal is checked to confirm correct demodulation of the first portion of the signal. A second estimation of the first portion of the signal is performed using the recovered data symbols to obtain second parameters of the first portion of the signal. Then, a second portion of the signal is demodulated using the second parameters when the first portion of the signal is correctly demodulated.

Abstract: A method is provided for identifying a training baud in a digital audio broadcasting signal. The method includes the steps of receiving a plurality of carrier signals modulated by a plurality of data baud, wherein the data baud include normal baud and training baud. The data baud received on the carriers are compared with predetermined data signals to produce a plurality of difference signals. The difference signals are then used to produce a plurality of distance signals, which are combined to produce group distance signals. One of the group distance signals is selected and used to determine if the data baud corresponding to the selected group distance signal is a training baud or a normal baud. This determination is performed by storing successive selected group distance signals until at least one training baud has been received, and using the stored group distance signals to determine normal/training synchronization.

Abstract: A spread spectrum phased array receiver has a set of phased array antennas. The set of phased array antennas receive a spread spectrum signal containing a plurality of channels. The receiver outputs timed versions of the received signal. Each timed version is associated with a respective one out of the set of phased array antennas. A plurality of despread signals is produced by despreading each timed version of the received signal using a plurality of chip code sequences associated with the channels. The despread signals are combined as a despread signal. A magnitude of the combined despread signal is determined for obtaining a present and a prior magnitude. The present and prior magnitude are compared. A delay associated with the timed versions is adjusted in response to the comparison so antenna beams are steered towards components of the spread spectrum signal with a highest combined magnitude.

Abstract: A frequency demodulating circuit for demodulating a frequency-modulated signal expressing digital data. The circuit includes a waveform shaping circuit for acquiring a binary signal from the frequency-modulated signal and a detector for decoding the binary signal and response to clock signals to obtain the digital data. A circuit also includes a clock signal generating circuit for generating the clock signals which have a frequency of the frequency-modulated signal corresponding to “one” of the digital data and a frequency higher than the frequency of the frequency-modulated signal by a multiple, which corresponds to a “zero” of the digital data.

Abstract: In order to increase accuracy of DC-offset compensation within radio receivers and to ensure that such compensation does not erode the dynamics of the decoders located within the receivers, the present invention separately performs mean value estimation and channel estimation. Additionally, a bias DC offset value caused by the use of a training sequence to perform mean value estimation can be corrected for in the channel estimator and equalizer.

Abstract: Methods and systems are provided for receiving a modulated signal including symbols representing both encoded and unencoded bits from a data (e.g., speech) frame where a received slot is first demodulated and the encoded bits are decoded. The decoded bits are then utilized to constrain demodulation during a second demodulation of a received slot. The encoded bit positions from the constrained second demodulation are, in turn, encoded to generate bit estimates for the received slot. This information is combined with the output of the constrained second demodulation for unencoded bits to provide a received data frame estimate which has been shown to have improved reliability for both encoded and unencoded bits. The methods and systems further provide for recursively repeating the demodulation and decoding steps until a counter expires or a desired reliability is obtained.

Abstract: A method and concomitant apparatus for adapting a logic threshold level in response to a background noise level in an information signal. Information signal excursions beyond the logic threshold are indicative of the presence of an information packet in the information signal. In this manner, a relatively low dynamic range information packet processor may reliably receive information packets.

Abstract: A method and apparatus for encoding/decoding data, wherein for one embodiment, during [During] encoding, a microprocessor (201) calculates Ym by standard Reed-Solomon encoding techniques. The microprocessor (201) then utilizes Ym as an index to a look-up table (203), and is returned G0Ym, G1Ym, . . . , GK−1Ym, from the look-up table (203). During syndrome calculation, a second set of parity symbols are generated from the information symbols using the method similar to the encoder, in particular, values for G0Ym, . . . , GK-,Y. are obtained from a first look-up table (503) in a similar manner as encoder to determine the values for G0Ym, G1Ym, . . . , GK−1Ym. A second look-up table (505) is set up to determine roots of the error locator polynomial. The second look-up table consists of several tables and each table contains (Q−1) elements, where Q is the size of the GF(Q) field.

Abstract: A method, apparatus, and system determine a location of a frequency synchronization signal in a frame of data transmitted from a transmitter and received by a receiver in a communication system including at least one transmitter and at least one receiver. A peak value representing a detected frequency synchronization signal transmitted from the transmitter to the receiver is calculated. A frequency offset between a carrier frequency of the transmitter and a frequency reference of the receiver is estimated, along with a quality factor for the estimated frequency offset. A determination is made whether the peak value is greater than or equal to a peak threshold and whether the quality factor is less than or equal to a quality threshold. When both of the predetermined threshold conditions are met, the peak value, frequency offset, and quality factor are stored.

Abstract: An improvement to a code-division-multiple-access (CDMA) system employing spread-spectrum modulation, with the CDMA system having a base station (BS) and a plurality of remote stations. The base station has a BS-spread-spectrum transmitter and a BS-spread-spectrum receiver. A remote station has an RS-spread-spectrum transmitter and an RS-spread-spectrum receiver. The BS transmitter transmits a broadcast common-synchronization channel, which includes a frame-timing signal. The broadcast common-synchronization channel has a common chip-sequence signal, which is common to the plurality of remote stations. In response to the RS-spread-spectrum receiver receiving the broadcast common-synchronization channel, and determining frame timing from the frame-timing signal, an RS-spread-spectrum transmitter transmits an access-burst signal. The BS-spread-spectrum transmitter, responsive to the BS-spread-spectrum receiver receiving the access-burst signal, transmits an acknowledgment signal.

Abstract: Provided is a circuit that has a simple circuit configuration and can detect zero values in a 1-bit digital signal irrespective of a recording medium such as SACD. DSD data forming the 1-bit digital signal are successively sent to a shift register (1) whose number of stages corresponds to the number of bits of an idle pattern such as “101010101” which appears when assuming a zero value. For example, the shift register (1) is an 8-bit shift register. An adder (2) sums up the values at each stages of the shift register (1). A zero decision circuit (4) produces an output indicating decision of zero if the sum value is half of the number of bits. A counter (5) keeps counting while the output indicating zero decision is being delivered. If the count value of the counter exceeds a given value, the counter produces an output indicating detection of a zero value.

Abstract: Apparatus for extracting a primary signal from a GSM signal containing co-channel interference partitions a signal burst into successive segments. Known characteristics of the GSM signal channel are used to estimate propagation path characteristics in respect of the first segment, and these are used to demodulate the segment. The demodulated signal is then used in a recursive process to estimate revised propagation path characteristics which are used for demodulating the subsequent segment. The demodulated segments and the estimated path characteristics are also used to derive segment signals representing the primary signal component alone, and these segment signals are used to reconstitute the primary signal. The derived primary signal can be subtracted from the received signal to extract the co-channel interfering signal. The apparatus functions with an omni-directional antenna, mounted for example on a moving vehicle.

Abstract: Methods and systems are provided for channel tracking utilizing multi-pass demodulation in which, during the second pass, decoded symbols are treated as known symbols which are used to calculate the error term used in updating the propagation characterization during the second pass. This allows a higher bandwidth to be used for updating the propagation characterization while known symbols are being processed. In particular, the propagation characterization may be provided by a channel tracker or a multi-antenna receiver, such as an interference rejection/combining (IRC) system, with an impairment correlation matrix estimator or a combination of both.

Abstract: The invention provides a method of sampling precision measurement signals to achieve an accurate measurement position at a particular measurement time, such that the measurement accuracy is unaffected by the velocity of motion. The method involves sampling each signal during a predetermined sampling period such that a signal from one sensor is sampled first, a signal from a second sensor sampled second, etc., and then the signals are sampled in reverse order such that the first signal sampled is sampled last. These sampled signals are averaged and produce a precision measurement at a time measured at one-half of the sampling time. In addition, this method can be applied to the use of separate scale tracks where each scale track is alternately sampled, or alternatively, where one scale track is sampled in the middle of the sampling period of another scale track.

Abstract: Linear space-time multiuser detectors are described that combine array processing, rake detection, and multiuser detection and that satisfy a minimum mean-squared error criteria. Both embodiments can be implemented adaptively so as to account for unknown sources of interference. The adaptive implementation of the first embodiment of a linear space-time detector requires explicit estimates of the channel coefficients. On the other hand, the adaptive implementation of the second embodiment does not require these estimates since they can be adaptively obtained. Both of these detectors provide significant performance advantages over single-user space-time detectors and over multiuser detectors which do not account for CDMA interference from unknown sources.

Abstract: A new method makes the most efficient use of the scarce spectral bandwidth in a wireless discrete multitone spread spectrum communications system. Each remote station and each base station in the network prepares an error detection field, such as a cyclic code (CRC), on each block of data to be transmitted over the traffic channels. The sending station prepares an error detection message for transmission over the link control channel of the network. The sending station prepares the error detection message by forming a link control channel vector that will be spread using the discrete multitone spread spectrum (DMT-SS) protocol to distribute the data message over a plurality of discrete tone frequencies, forming a spread signal for the link control channel. A link control channel is associated with communications session using the traffic channels. The instant of transmission of the error detection message is allowed to be different from the instant of transmission of the data message.

Abstract: A leading wave position detecting unit and method etc. is provided for detecting the position of the leading wave in a delay profile. Time spaces between sampled values (&tgr;1-&tgr;13) in the delay profile are measured. Among the measured time spaces, a maximum time space (&tgr;8) is determined, and the position of its immediately following sampled value (sampled value (h)) is detected as a leading position. The initial peak of the sampled values after the leading position detected (position of sampled value (j)) is determined as a leading wave position.

Abstract: Methods are provided for determining whether any slots of a modem frame are subject to robbed bit signaling (RBS), and whether the robbed bit signaling is &bgr;-codec robbed bit signaling. From an obtained DIL sequence, an ordered table of level values for each slot is generated. In determining whether any slots are RBS slots, distances between adjacent levels of the table for each slot are obtained and are compared to a “zero distance” threshold value in order to determine the number of distances which exceed the “zero distance” value. For each slot, the number of zero distances are compared to a threshold value, and if the number of zero distances exceeds the threshold value, the slot is declared to be a RBS slot. Zero distance thresholds for each slot are generated by finding a function of a maximum distance for that slot among the adjacent levels. In determining whether any RBS slots are &bgr;-codec slots, distances are found between corresponding levels of the ordered tables.

Abstract: A dual-mode receiver uses a hybrid cost function that provides for automatic constellation phase recovery regardless of whether a CAP signal or a QAM signal has been transmitted. In one embodiment, the receiver uses a hybrid cost function that is the superposition of a QAM-based cost function and a CAP-based cost function. In another embodiment, the receiver comprises an adaptive filter that alternates between a QAM-based cost function and a CAP-based cost function. In addition, a method is described that uses information about (a) the expected constellations, and (b) the values before and after a rotator of the receiver for deciding what type of signal is being received.

Abstract: An improved apparatus for implementing shell mapping in a PCM modem incorporates u-law signal mapping points. An improved signal point encoding technique effectively employs ring-indices that are generated in accordance with known principles. The ring indices are applied to a reordering module, which rearranges the ring indices produced by a conventional shell mapping algorithm. A preferred reordering scheme takes advantage of the non-uniform probability distribution provided by the conventional shell-mapping algorithm. The rings are rearranged such that the sets of signal points having relatively small separation distances are assigned to rings with relatively low frequencies of occurrence, while the sets of signal points having relatively large separation distances are assigned to rings with relatively high frequencies of occurrence. The reordering scheme optimizes the signal point assignment while maintaining acceptable limits for average transmission power.

Abstract: The back end position of a pulse, which is transmitted from a remote control, varies according to the transmission distance, and the pulse width changes. A remote control receiver of the present invention detects the pulse width of a header, which is formed at the head of each frame in a remote control signal from the remote control, so as to detect the transmission distance of the remote control signal and a change in back end position of each pulse in a data part, which is transmitted after the header. Then, the back end position of each pulse is corrected to original. This eliminates the change in pulse width resulting from a change in transmission distance, and increases the allowable range of the transmission distance of the remote control.

Abstract: A cellular mobile telephone system includes a first carrier estimation stage that estimates carrier signals using pilot symbols that have been inserted a signal received by the telephone system. The pilot symbols have a known code pattern. The first carrier estimation stage produces a data symbol train. A second carrier estimation stage estimates the carrier signals using the data symbol train and the pilot symbols. In this way, the telephone system can reproduce a highly precise carrier used in coherent detection in a cellular mobile CDMA system.

Abstract: Apparatus and methods for puncturing and recovering a code in a spread spectrum communication system are provided. Repeated symbols are punctured in predetermined locations and different data is inserted in the punctured locations, in a transmitter. Then, in a receiver, the punctured symbols are recovered by separating the inserted data from input data and filling previous unpunctured symbols in the punctured locations. In another embodiment, the transmitter simply punctures repeated symbols in predetermined locations to obtain an intended symbol rate. Then, the receiver recovers the punctured symbols by filling previous unpunctured symbols in the punctured locations. Therefore, errors at channel decoding are reduced.

Abstract: In a burst mode communication system bursts arrive at a receiver which must correctly acquire and track carrier and clock phases in order to recover the transmitted symbols. A burst mode receiver is used to recover the clock and carrier phase. The detection of an initiator pulse indicates the presence of a burst signal, and a cross-coupled fractionally spaced digital filter structure is used with a known preamble to perform symbol sampling phase recovery and carrier phase acquisition, and during the normal mode of operation results in a tracking of the symbol and carrier phases.

Abstract: A communication system (11) uses concatenated coding in which an inner code is configured to match the needs of an outer code. The inner code is implemented through a pragmatic trellis coded modulation encoder (18) and decoder (34). A parser (50) of the encoder (18) distributes fewer than one user information bit per unit interval (66) to a convolutional encoder (58) which generates at least two convolutionally encoded bits for each user information bit it processes. Exactly one of the convolutionally encoded bits is phase mapped (56) with at least two user information bits during each unit interval (66). The decoder (34) detects a frame sync pattern (48) inserted into the user information bits to resolve phase ambiguities. Phase estimates are convolutionally decoded (100) to provide decoded data estimates that are then used to selectively rotate the phase estimates prior to routing the phase estimates to a slice detector (118).

Abstract: A method for determining the best time to sample data bits of a data bit stream of a received information signal in a digital communication system includes the steps of determining the current derivative of a respective sample of the information signal, weighting the sample by a predetermined amount, determining an accumulated derivative value for the same sample number of a previous symbol of the information signal, weighting the previous accumulated derivative value by another predetermined amount, summing the two weighted values together and assigning this accumulated derivative value to the respective sample. The method further includes the step of comparing the accumulated derivative values of a predetermined number of consecutive samples to determine which sample has the greatest accumulated derivative value. The sample having the greatest accumulated derivative value substantially corresponds to the beginning of a symbol.

Abstract: A method and apparatus for receiving an input digital data signal representing a sequence of values in which samples of the waveform of the data signal are taken a plurality of times during each of the values. A plurality of the samples are stored as they are received, in a known order in locations at a sequence of addresses in a memory. A digital signal representing the difference in phase between the input data signal and a reference signal is derived. The digital phase signal is decoded and the location at the address of the memory represented by the digital phase signal is accessed so as to select samples remote from edges in the waveform of the input data signal.

Abstract: A circuit for restoring bits transmitted by an asynchronous signal includes a first comparator for comparing the level of the asynchronous signal with a first threshold adjusted as a function of the output of the first comparator during synchronization bursts of the asynchronous signal, and at least a second comparator for comparing the level of the asynchronous signal with a second threshold correlated to the first threshold.

Abstract: A burst demodulator prevents transmission efficiency from being lowered, and a dynamic range of an input strength from being narrowed, by providing a stable frame signal even if the reaction is rapid against the input and the input strength is low. A logarithm amplifier outputs an electric power strength of a modulated input signal as a logarithm value, and an integrator smooths the output of the logarithm amplifier and outputs the smoothed output as an RSSI. The comparator compares the RSSI with the appropriate reference value REF while including some margin within the noise level, and outputs the frame signal of an `LO` state when the RSSI is lower than the REF, that is, during the non-signal zone, of an `HI` state when the RSSI is higher than the REF, that is, during the signal zone. The period of the comparator output continuously remaining in the `LO` state cannot exceed one clock period even if the comparator output flutters within one time slot.