Patents by Inventor Lee-Fang Wei
Lee-Fang Wei has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).
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Patent number: 6233286Abstract: Improved error rate performance of data transmissions systems using both coded and uncoded modulation in the presence of more-than-mild intersymbol interference is achieved in the receiver using M-path joint decision feedback equalizer/decoder in conjunction with a finer partition of the constellation than was used in the transmitter and a refined receiver trellis diagram based on that finer partition.Type: GrantFiled: March 27, 1998Date of Patent: May 15, 2001Assignee: Lucent Technologies Inc.Inventor: Lee-Fang Wei
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Patent number: 6157678Abstract: Signal points from a PCM-derived constellation are selected for transmission via a modulation technique which employs different levels of redundancy coding--including the possibility of no redundancy coding--for respective different sub-constellations of the overall PCM-derived constellation. The coding that is employed for at least one of the sub-constellations is carried out independently from any coding that is employed for any of the other sub-constellations. In preferred embodiments, the sub-constellations are non-overlapping portions of the overall PCM-derived constellation, the redundancy codes are trellis codes, and the trellis codes employed in conjunction with sub-constellations having increasingly smaller minimum distance between signal points provide respectively increasing amounts of decibel gain in that minimum distance in order to compensate for that increasingly smaller minimum distance.Type: GrantFiled: May 12, 1997Date of Patent: December 5, 2000Assignee: Lucent Technologies Inc.Inventor: Lee-Fang Wei
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Patent number: 6151370Abstract: A path-oriented approach is provided to determine surviving paths in a decoder. The paths that are retained as the surviving paths are some number, M, of the paths which have the smallest path metrics, even if two or more of those paths come into a given state. This approach provides significantly improved performance in at least those applications in which branch metrics are a function of the surviving path from which the branch emanates.Type: GrantFiled: February 12, 1998Date of Patent: November 21, 2000Assignee: Lucent Technologies Inc.Inventor: Lee-Fang Wei
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Patent number: 5953376Abstract: Signal points from a PCM-derived constellation are selected for transmission via a modulation technique which employs different levels of redundancy coding--including the possibility of no redundancy coding--for respective different sub-constellations of the overall PCM-derived constellation. The coding that is employed for at least one of the sub-constellations is carried out independently from any coding that is employed for any of the other sub-constellations. In preferred embodiments, the sub-constellations are non-overlapping portions of the overall PCM-derived constellation, the redundancy codes are trellis codes, and the trellis codes employed in conjunction with sub-constellations having increasingly smaller minimum distance between signal points provide respectively increasing amounts of decibel gain in that minimum distance in order to compensate for that increasingly smaller minimum distance.Type: GrantFiled: November 25, 1996Date of Patent: September 14, 1999Assignee: Lucent Technologies Inc.Inventor: Lee-Fang Wei
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Patent number: 5872817Abstract: Decision feedback equalization is used in a communication system which employs coded modulation, such as trellis coded modulation. The transmitted stream of signal points includes first signal points that were generated using a particular coded modulation scheme interspersed with second signal points that were generated without the using of coding, and estimated intersymbol interference components for the second signal points are generated in response to tentative decisions as to the first signal points formed by the Viterbi decoder. Rather than forming immediate final decisions as to the second signal points, there is formed a tentative decision for each one of the second signal points associated with each Viterbi decoder state using an estimated intersymbol interference component provided from a decision feedback equalizer associated with that state. Each second-signal-point tentative decision is used to extend the surviving path for the associated state and to also update its path metric.Type: GrantFiled: September 24, 1997Date of Patent: February 16, 1999Assignee: Lucent Technologies Inc.Inventor: Lee-Fang Wei
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Patent number: 5719875Abstract: A systematic convolutional interleaver arrangement that is obtained by treating the input signals of an associated error correcting encoder as if they had been pre-interleaved in a very particular way so that the order of the input signals of the encoder is not altered when it is transmitted to the channel. By way of example, an interleaver/deinterleaver arrangement is disclosed that uses Reed Solomon code RS(120,116) and employs delay element banks and associated routing to interleave and deinterleave the signals.Type: GrantFiled: June 11, 1996Date of Patent: February 17, 1998Assignee: Lucent Technologies Inc.Inventor: Lee-Fang Wei
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Patent number: 5706312Abstract: Coding gain is improved by employing an N-dimensional trellis encoder incorporating an N'-dimensional convolutional encoder where N' is less than N. The additional coding gain is realized as a shaping gain. This unique modulator encodes a digital signal by generating a sequence of N-dimensional symbols as a function of the digital signal using an N'-dimensional convolutional encoder within the trellis encoder more than once (integer N/N' times) during each N-dimensional symbol interval. This allows the trellis encoder to produce an output of higher dimensionality than would normally be expected from the lower dimensionality convolutional encoder. The trellis encoder is applicable to television transmission.Type: GrantFiled: March 31, 1997Date of Patent: January 6, 1998Assignee: Lucent Technologies Inc.Inventor: Lee-Fang Wei
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Patent number: 5598432Abstract: A reduced speed equalizer is provided which receives signal samples at a first rate but performs the equalizing operation at a second, lower rate which is below the rate at which symbols are transmitted across the channel. The equalizer is docked to receive samples in a shift register at the first rate. Samples stored in the shift register are clocked into a set of buffers at the second rate. The equalizer coefficients are applied to the samples stored in the buffer set to generate a sequence of equalized symbols at the second rate.Type: GrantFiled: April 2, 1996Date of Patent: January 28, 1997Assignee: Lucent Technologies Inc.Inventor: Lee-Fang Wei
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Patent number: 5559561Abstract: An HDTV transmission system includes a Tomlinson precoder in the transmitter in order to compensate for forced intersymbol interference introduced by an NTSC rejection filter used in the receiver. The system employs one of a family of four-dimensional coded modulation schemes based on a six-signal-point, one-dimensional base constellation. The various schemes exhibit different amounts of so-called shaping gain and support respective different payload data rates. The characteristics of the Tomlinson precoder are such as to preserve the substantial portion of the shaping gain. The system may switch its operation among the various coded modulation schemes to account for changes in channel conditions and/or to accommodate different source signal bit rates.Type: GrantFiled: July 15, 1994Date of Patent: September 24, 1996Assignee: Lucent Technologies Inc.Inventor: Lee-Fang Wei
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Patent number: 5548615Abstract: A rotationally invariant, multilevel coded modulation scheme is provided by partitioning a constellation, such as an M-PSK or QAM constellation, into several trellis-subsets, each of which is further partitioned into block subsets. The input bits are then encoded to select a signal point from the constellation. A first portion of the input bits are differentially encoded. A second portion of the input bits, together with at least one of the differentially encoded bits, are trellis encoded to select a trellis subset of the constellation. A third portion of the input bits--excluding any differentially encoded bits --are block encoded to select a block subset from the selected trellis subset. A fourth portion of the input bits, together with the remaining differentially encoded bits, are used to select a signal point from the selected block subset.Type: GrantFiled: May 3, 1993Date of Patent: August 20, 1996Assignee: AT&T Corp.Inventor: Lee-Fang Wei
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Patent number: 5473621Abstract: In a modulation scheme involving differential encoding and Reed-Solomon encoding, the differential encoding is performed before the Reed-Solomon encoding in the transmitter. In the receiver, a differential decoding operation is performed after an RS decoding operation. The overall coding scheme and the RS decoding are so arranged as to ensure that the RS decoding will be proper in the presence of phase rotations, notwithstanding the fact that the differential encoding is performed before the RS encoding in the transmitter and the fact that the RS decoding is performed before the differential decoding in the receiver.Type: GrantFiled: April 16, 1992Date of Patent: December 5, 1995Assignee: AT&T Corp.Inventor: Lee-Fang Wei
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Patent number: 5442626Abstract: A cost-effective, bandwidth-efficient, and power-efficient system is provided in which data streams received from several different video sources are converted into sequences of symbols selected from a predetermined constellation and are multiplexed on a symbol-by-symbol basis into a single sequence of symbols for transmission on a channel. Using a symbol multiplexer helps to mitigate the effect of bursty noise in the receiver and reduces the processing speed requirement in the receiver.Type: GrantFiled: August 24, 1993Date of Patent: August 15, 1995Assignee: AT&T Corp.Inventor: Lee-Fang Wei
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Patent number: 5418798Abstract: A trellis-coded modulation system is provided in which the output of the trellis encoder is used to select a subset of a multidimensional QAM constellation. The selection process is performed such that a) the minimum square Euclidean distance between valid sequences of successive selected subsets is maximized, b) the resulting code is rotationally invariant, and c) the selected subset corresponding to a transition of the trellis encoder from a present state i to a different next state j is different from the selected subset that corresponds to a transition of the trellis encoder from a present state j to a next state i.Type: GrantFiled: April 19, 1993Date of Patent: May 23, 1995Assignee: AT&T Corp.Inventor: Lee-Fang Wei
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Patent number: 5398073Abstract: A modulation scheme for HDTV, for example, uses a concatenated code comprised of a Reed-Solomon coder followed by an N-dimensional trellis coder whose N-dimensional output symbols with N>1, are used to modulate a one-dimensional vestigial sideband modulator. Specifically, each N-dimensional symbol is a sequence of N one-dimensional signal points--specifically signal points of a one-dimensional VSB constellation.Type: GrantFiled: April 12, 1994Date of Patent: March 14, 1995Assignee: AT&T Corp.Inventor: Lee-Fang Wei
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Patent number: 5329551Abstract: A multilevel coded modulation scheme trellis encodes a portion of the input data and the resulting encoded stream is used to identify a particular one of a predetermined number of subsets of symbols of a predetermined signal constellation. The remaining input data is coded using a Reed-Solomon (RV) code whose output is used to select for transmission a particular symbol from the identified subset. In applications in which phase hits or other channel phenomena may cause the received signal points to be phase-rotated versions of the signal points that were transmitted, differential encoding is included in the overall coded modulation scheme. In different embodiments, the differential encoding/decoding and RV encoding/decoding are in different orders. In one such embodiment, overlapped multilevel codes are used to preserve the advantages afforded by taking a multilevel coding approach.Type: GrantFiled: April 16, 1992Date of Patent: July 12, 1994Assignee: AT&T Bell LaboratoriesInventor: Lee-Fang Wei
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Patent number: 5311547Abstract: Digital data is transmitted over partial-response channels using a precoding technique which allows for the use of a wide variety of transmit constellations. A sequence of signal points is selected from a predetermined base constellation meeting particular criteria. A so-called combined signal point is developed for a present symbol interval by a) selecting a signal point from the base constellation as a function of input bits associated with the present symbol interval and b) combining the signal point thus selected with a feedback signal which is a function of one or more combined signal points that were developed for previous symbol intervals, that function being determined by the characteristic of the partial-response channel. A transmit signal which represents the combined signal points is then provided. In one implementation, the processing steps are performed explicitly using an integrated precoder/constellation mapper. In another implementation those steps are performed implicitly using table look-up.Type: GrantFiled: February 3, 1992Date of Patent: May 10, 1994Assignee: AT&T Bell LaboratoriesInventor: Lee-Fang Wei
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Patent number: 5301209Abstract: The decoding depth of a multidimensional trellis-coding scheme with X-fold time diversity is reduced, or minimized. As a result, an improvement in error rate performance is achieved for the multidimensional trellis code, which can then be favorably applied to a fading channel application.Type: GrantFiled: October 9, 1991Date of Patent: April 5, 1994Assignee: AT&T Bell LaboratoriesInventor: Lee-Fang Wei
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Patent number: 5258987Abstract: A multilevel coded modulation scheme trellis encodes a portion of the input data and the resulting encoded stream is used to identify a particular one of a predetermined number of subsets of symbols of a predetermined signal constellation. The remaining input data is coded using a Reed-Solomon (RS) code whose output is used to select for transmission a particular symbol from the identified subset. In applications in which phase hits or other channel phenomena may cause the received signal points to be phase-rotated versions of the signal points that were transmitted, differential encoding is included in the overall coded modulation scheme. In different embodiments, the differential encoding/decoding and RS encoding/decoding are in different orders. In one such embodiment, overlapped multilevel codes are used to preserve the advantages afforded by taking a multilevel coding approach.Type: GrantFiled: April 16, 1992Date of Patent: November 2, 1993Assignee: AT&T Bell LaboratoriesInventor: Lee-Fang Wei
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Patent number: 5243629Abstract: A high definition television (HDTV) signal is transmitted by a multi-subcarrier transmission scheme in which each subcarrier is used to carry a different class of HDTV information.Type: GrantFiled: September 3, 1991Date of Patent: September 7, 1993Assignee: AT&T Bell LaboratoriesInventor: Lee-Fang Wei
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Patent number: 5216694Abstract: A trellis-coded communications system for encoding a fractional number of bits is described. In this system, the number of allowed state transitions, originating from each state of a trellis encoder, is restricted to a number that is not an integral power of an integer. Furthermore, not all state transitions are used with equal probability.Type: GrantFiled: September 12, 1991Date of Patent: June 1, 1993Assignee: AT&T Bell LaboratoriesInventor: Lee-Fang Wei