Q. Wang

AT&T Labs, Austin, Texas, United States

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Publications (40)34.07 Total impact

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    ABSTRACT: To understand better the genetic basis of the clonal evolution of prostate carcinoma, the authors analyzed the pattern of allelic loss in 25 matched primary and metastatic prostate tumors. Twenty-five cases were selected from the surgical pathology files of the Mayo Clinic from patients who had undergone radical retropubic prostatectomy and bilateral lymphadenectomy between 1987-1991. All patients had regional lymph node metastases at the time of surgery. DNA samples for the analysis of allelic loss pattern were prepared from primary tumors and matched synchronous lymph node metastases by tissue microdissection. The oligonucleotide primer pairs for the microsatellite DNA markers were D8S133, D8S136, D8S137, ANK1 on chromosome 8p12-21, LPLTET on chromosome 8p22, and D17S855 (intragenic to the BRCA1 gene) on chromosome 17q21. One case was not informative at any of the loci tested and was excluded from further analysis. The overall frequency of allelic imbalance was 79% in primary tumors and 88% in paired metastases. Of 24 informative cases, 14 patients (58%) showed the same pattern of allelic loss or retention in matched primary and metastatic tumors at all marker locus; discordant allelic loss was observed in the remaining 10 patients (42%). Four patients showed loss of the same allele at one or more marker loci in both primary and metastatic tumors, but discordant allelic loss was observed at other marker loci. Five patients showed allelic loss in at least one genetic marker in the metastatic tumor but not in its matched primary tumor. Five patients displayed loss of one allele at one or more marker loci in a primary tumor but not in the matched metastases. There was no significant difference in the frequency of allelic imbalance between primary and metastatic tumors at any marker analyzed (P>0.05). These data suggest that different patterns of allelic deletion may be acquired during cancer progression to metastases. The differences in genetic composition between primary prostate carcinoma and its metastases may be related to intrinsic cancer heterogeneity, overall genetic instability, and clonal divergence.
    Cancer 06/1999; 85(9):2017-22. · 5.20 Impact Factor
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    ABSTRACT: Maximum-likelihood diversity combining is investigated for an FFH/MFSK spread spectrum system in partial-band noise (PBN). The structure of maximum-likelihood diversity reception in PBN plus white Gaussian noise is derived. It is shown that signal-to-noise ratio and the noise variance at each hop have to be known to implement this optimum diversity combiner. Several suboptimum diversity combining schemes are also considered. The performance of the optimum combining scheme is evaluated. It is shown that adaptive gain control diversity combining actually achieves the optimum performance when interference is not very weak
    IEEE Transactions on Communications 01/1999; · 1.75 Impact Factor
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    ABSTRACT: We derive a closed-form expression for the power spectral density of amplitude/phase-shift keyed bit sequences randomized through self-synchronizing scrambling when the source sequence is a stationary sequence of statistically independent bits. In addition to the dependence on the symbol pulse shape, duration, and the signal space values with which symbols are represented, we show that the power spectral density is dependent only on the probability of logic ones in the source bit stream, the period of the impulse response of the scrambling shift register, and the number of logic ones in this period. Our results confirm that optimum randomization results with use of primitive scrambling polynomials and poorest randomization occurs with “two-tap” polynomials of the form x<sup>D</sup>+1
    IEEE Transactions on Information Theory 08/1998; · 2.62 Impact Factor
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    ABSTRACT: The authors develop a practical method of evaluating the power spectral density of guided scrambling line-coded sequences. Analysis of block-coded signals is reviewed, and it is shown that it is impractical to analyse continuous guided scrambling coded sequences with expressions presented elsewhere in the literature. Alternative expressions for sequence autocorrelation are derived which depend on the relationship of several code parameters. Two relationships are considered in detail, and it is shown how expressions derived in these instances can be applied to other guided scrambling codes. Using these expressions, the spectral characteristics of several continuous guided scrambling codes are evaluated. These spectra demonstrate the important result that variation in the average statistics of the coded sequences with varying source-stream statistics decreases as the degree of the scrambling polynomial increases
    IEE Proceedings - Communications 05/1997; · 0.32 Impact Factor
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    ABSTRACT: We derive several properties of guided scrambling (GS) encoders and the sequences they generate. We first highlight symmetrical aspects of the GS encoding mechanisms proposed to date, and then show that the existence of discrete components in the power spectrum of the pulse-amplitude-modulated encoded sequence can be predicted from the weight of the scrambling polynomial. We also show that with equiprobable source words, the block or continuous nature of the code has no effect on the statistics of the encoded sequence. We conclude by demonstrating how these properties simplify evaluation of the spectral characteristics of GS coded sequences
    IEEE Transactions on Information Theory 02/1997; · 2.62 Impact Factor
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    ABSTRACT: The application of the concatenated orthogonal/PN spreading scheme for integrated traffic is introduced. Bhargava (1994) proposed using a single line rate (adjusted data rate before spreading) to accommodate traffic with a wide range of source rates. For traffic with source rates higher than the line rate, the authors propose using concatenated orthogonal/PN spreading sequences to subdivide a high rate stream into several parallel line rate streams. The performance of the concatenated orthogonal-PN spreading sequence for homogenous voice traffic in various cellular mobile environments with multipath fading, log-normal shadowing and path loss, is first analyzed and compared with that of the conventional non-concatenated long PN sequence. The authors then evaluate the performance of a system with integrated traffic of voice and video. In conjunction with this, they propose the use of cosets of Walsh-Hadamard (WH) codes to reduce the multi-user interference. Different methods of assigning the spreading sequences among the cosets which improve the capacity of both voice and video users, are investigated
    Communications, 1995. ICC '95 Seattle, 'Gateway to Globalization', 1995 IEEE International Conference on; 07/1995
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    ABSTRACT: A wireless multimedia network using a novel channel equalizer on a TDD CDMA/TDMA scheme is proposed. The uplink employs a CDMA scheme to transmit low speed human interface signals, and the downlink employs a TDMA scheme to transmit high speed signals including video and images. The control signals for equalization are calculated by using the output of the matched filters of the CDMA receiver. Theoretical analysis has been carried out to evaluate the BER performance. Numerical results show that a low BER of less than 10<sup>-6</sup> is achieved for the downlink by employing the proposed channel equalizer
    Communications, Computers, and Signal Processing, 1995. Proceedings. IEEE Pacific Rim Conference on; 06/1995
  • Source
    B. Wu, Q. Wang
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    ABSTRACT: In synchronous CDMA systems, the optimal multiuser detection is equivalent to an unconstrained quadratic bivalent optimization problem. This detector has an exponential computational complexity with the number of users which makes it impractical. We propose several sub-optimal detectors based on a local minimization algorithm. The performance of these detectors are compared with those of the optimal and several other sub-optimal solutions. It is shown that the optimal performance is closely approached by one of our solutions with greatly reduced computational complexity
    Communications, Computers, and Signal Processing, 1995. Proceedings. IEEE Pacific Rim Conference on; 06/1995
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    ABSTRACT: A packet CDMA protocol intended for carrying two types of traffic in the cellular environment of an integrated wireless access network (IWAN) is presented. We examine the performance of the protocol and present numerical results for the equilibrium system state
    Communications, Computers, and Signal Processing, 1995. Proceedings. IEEE Pacific Rim Conference on; 06/1995
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    ABSTRACT: Guided scrambling (GS) is a line coding technique developed specifically for high bit rate fiber optic transmission systems. This paper continues the development of GS coding by introducing more scrambling polynomials that can be used with this technique. First, a method is presented for constructing polynomials which can be used with balanced encoding. Then it is shown that these polynomials can be used as bases for large families of polynomials, an expansion whose usefulness is demonstrated with the presentation of power spectra for several code configurations. These results indicate that polynomials can be selected from these families to exercise control over average as well as worst-case statistics of the encoded bit stream, a property not available with any other single efficient, balanced line coding technique developed to date. Criteria for polynomial selection are given, and polynomials are recommended for several GS code configurations
    IEEE Journal on Selected Areas in Communications 05/1995; · 3.12 Impact Factor
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    ABSTRACT: Guided scrambling (GS) line codes augment the source bit stream prior to self-synchronizing scrambling to ensure that the scrambling process generates an encoded bit sequence with good line code characteristics. With arithmetic from the ring of polynomials over GF(2), self-synchronizing scrambling can be interpreted as division of the source bit sequence by the scrambling polynomial and transmission of the resulting quotient. When augmenting bits are inserted in fixed, periodic positions, GS codes can be interpreted as block line codes which encode source words to quotients. In particular, block guided scrambling (BGS) generates a transmitted bit stream which is a concatenation of finite-length quotients chosen from sets of quotients which represent each source word. Alternatively, in continuous guided scrambling (CGS), the transmitted sequence appears to be a continuous quotient due to the fact that the encoder shift registers are updated following quotient selection to contain the remainder associated with the selected quotient. The quotient selection mechanisms of both BGS and CGS encoders can be modeled as finite state machines with quotient sets as input and the selected quotient as output. In CGS encoding, the selection mechanism also outputs the remainder associated with the selected quotient. In this paper we describe several characteristics of GS encoders and their coded sequences
    01/1995;
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    ABSTRACT: This paper considers the application of rate-adaptive coding (RAC) to a spread spectrum multiple access (SSMA) communication system. Specifically, RAC using a variable rate Reed-Solomon (RS) code with a single decoder is applied to frequency-hopped SSMA. We show that this combination can accommodate a larger number of users compared to that with conventional fixed-rate coding. This increase is a result of a reduction in the channel interference from other users. The penalty for this improvement in most cases is a slight increase in the delay (composed of propagation and decoding delay). The throughput and the undetected error probability for a M-ary symmetric channel are analyzed, and performance results are presented
    IEEE Journal on Selected Areas in Communications 07/1994; · 3.12 Impact Factor
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    ABSTRACT: Maximum-likelihood diversity combining for an FFH/MFSK spread spectrum system on a partial-band noise (PBN) interference channel is investigated. The structure of maximum-likelihood diversity reception on a PBN channel with additive white Gaussian noise (AWGN) is derived. It is shown that signal-to-noise ratio and the noise variance at each hop have to be known to implement this optimum diversity combining. The performance of the maximum-likelihood combining can be used as a standard in judging the performance of other suboptimum, but more practical diversity combining schemes. The performance of the optimum combining scheme is evaluated. It is shown that the performance difference between some of the known diversity combining schemes, which do not require channel information to operate, and the optimum scheme is not small when the diversity order is low
    Military Communications Conference, 1993. MILCOM '93. Conference record. 'Communications on the Move'., IEEE; 11/1993
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    ABSTRACT: Line codes are used in digital communication systems to control the characteristics of transmitted symbol sequences. Recently, an efficient and easily implemented family of codes called guided scrambling (GS) codes has been introduced. Previous work indicated that continuous GS (CGS) codes can be configured to generate encoded sequences with statistics nearly independent from those of the source bit stream, a property not available with any other efficient line code technique developed to date. This paper presents analysis of the spectral characteristics of these codes which confirms this conjecture. The principle of guided scrambling is reviewed. Then, by showing that the scrambling polynomials currently recommended for GS codes can be regarded as base polynomials for large families of polynomials, expanded sets of scrambling polynomials are proposed. Evaluation of the power spectral density of CGS codes which use scrambling polynomials from these expanded sets is then considered, under the condition only that the input bit stream is stationary. Expressions which limit required computation to practical limits are developed, and results for several code configurations are given. Here it is demonstrated that when scrambling polynomials of high degree are used, the characteristics of the transmitted symbol sequence become nearly independent of the source bit stream statistics
    Electrical and Computer Engineering, 1993. Canadian Conference on; 10/1993
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    ABSTRACT: The coded performance of a slow-frequency hopped differential PSK (SFH/DPSK) system in the presence of both tone jamming and additive white Gaussian noise (AWGN) is studied. The error correlation due to DPSK demodulation and the effect of tone jamming is considered when evaluating the block and decoded error probabilities. The decoded error probabilities in some special cases are computed. The effect of interleaving on system performance is addressed under various conditions. A nearly optimum code rate for a Reed-Solomon code is determined for systems employing interleaving techniques. The effect of partial-band tone jamming is demonstrated.< >
    Communications, Speech and Vision, IEE Proceedings I 09/1993;
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    ABSTRACT: An error-correction scheme for an M -ary symmetric channel ( M SC) characterized by a large error probability p <sub>e</sub> is considered. The value of p <sub>e</sub> can be near, but smaller than, 1-1/ M , for which the channel capacity is zero, such as may occur in a jamming environment. The coding scheme consists of an outer convolutional code and an inner repetition code of length m that is used for each convolutional code symbol. At the receiving end, the m inner code symbols are used to form a soft-decision metric, which is passed to a soft-decision decoder for the convolutional code. The effect of finite quantization and methods to generate binary metrics for M >2 are investigated. Monte Carlo simulation results are presented. For the binary symmetric channel (BSC), it is shown that the overall code rate is larger than 0.6 R <sub>0</sub>, where R <sub>0</sub> is the cutoff rate of the channel. New union bounds on the bit error probability for systems with a binary convolutional code on 4-ary and 8-ary orthogonal channels are presented. For a BSC and a large m , a method is presented for BER approximation based on the central limit theorem
    IEEE Transactions on Communications 07/1993; · 1.75 Impact Factor
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    ABSTRACT: An exponential form of non-ideal power control in the reverse links of a CDMA (code division multiple access) cellular network is presented. It is shown that there exists an optimum non-ideal power control system which leads to an increased capacity of the cellular system. This kind of non-ideal power control might also be called soft-limiting power control
    Communications, Computers and Signal Processing, 1993., IEEE Pacific Rim Conference on; 06/1993
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    ABSTRACT: The scheme is based on the rate-adaptive RS (Reed-Solomon) Code As The Outer Code, And The Convolutional Code, as the inner code. The throughput and error probability for this scheme are derived. As an example, the scheme is applied to the Rayleigh fading channel and is compared to the system using only the rate-adaptive RS code. In both cases a maximum of four transmissions for each codeword is assumed. It is shown that, by using a 1/2 rate memory m = 3 systematic convolutional code (with hard decision decoding) in conjunction with a (60,26) RS code, a 2-dB improvement is achievable, compared to a rate-adaptive RS code. It is also shown that applying soft decision to the Viterbi decoder has a 4-dB advantage over the hard decision decoding
    Communications, Computers and Signal Processing, 1993., IEEE Pacific Rim Conference on; 06/1993
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    ABSTRACT: A frequency-hopped spread-spectrum multiple-access (FH-SSMA) communication system with a rate-adaptive coding scheme is considered. The scheme uses a variable-rate Reed-Solomon code, with a single decoder. Two cases are considered: N -ary frequency-shift keying (FSK) without erasure and N -ary FSK with perfect side information as to whether a channel symbol is hit or not. It is shown that FH-SSMA with this rate-adaptive coding scheme can serve a higher number of users than with fixed-rate coding for the above mentioned cases. This increase in the number of users is due to the higher throughput which results in less interference for the other users. It is shown that perfect side information increases the capacity of the system. The number of users can further increase if more time delay is allowed in the system
    Global Telecommunications Conference, 1992. Conference Record., GLOBECOM '92. Communication for Global Users., IEEE; 01/1993
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    ABSTRACT: In direct sequence (DS) spread-spectrum systems, correlation techniques are used to extract information from the received signal. The various correlation procedures used in established DS systems offer a tradeoff between acquisition time, correlator complexity, and system performance. The paper introduces a new spread-spectrum technique which employs an easily implemented spreading/despreading mechanism that despreads the received signal immediately upon its reception. The data signal is spread through modulo-2 division using shift register techniques and despread through multiplication using a delay-and-multiply circuit. Since the sequence transmitted is a quotient, the technique is called transmitted-quotient direct sequence (TQ-DS). Preliminary performance results indicate that the cost of zero-acquisition time and low complexity is a significant degradation in system bit error rate (BER) performance relative to that of established spread-spectrum systems
    Wireless Communications, 1992. Conference Proceedings., 1992 IEEE International Conference on Selected Topics in; 07/1992

Publication Stats

153 Citations
1k Views
34.07 Total Impact Points

Institutions

  • 1999
    • AT&T Labs
      Austin, Texas, United States
  • 1986–1995
    • University of Victoria
      • Department of Electrical and Computer Engineering (ECE)
      Victoria, British Columbia, Canada
  • 1994
    • Carleton University
      • Department of Systems and Computer Engineering
      Ottawa, Ontario, Canada
  • 1992
    • University of Waterloo
      Waterloo, Ontario, Canada