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International Conference on Acoustics, Speech, and Signal Processing (ICASSP)

作者： T. Amada K. Miseki M. Akamine Kansai Research Laboratories Toshiba Corporation Kobe Japan

CELP coders using pulse codebooks for excitations such as ACELP have the advantages of low complexity and high speech quality. At low bit rates, however, the decrease of pulse position candidates and the number of pulses degrades reconstructed speech quality. This paper describes a method for adaptively allocating of pulse position candidates. In the proposed method, N efficient candidates of pulse positions are selected out of all possible positions in a subframe. The amplitude envelope of an adaptive code vector is used for selecting N efficient candidates. The larger the amplitude is, the more pulse positions are assigned. Using an adaptive code vector for the adaptation, the proposed method requires no additional bits for the adaptation. Experimental results show that the proposed method increases WSNRseg by 0.3 dB and MOS by 0.15.

关键词： Speech coding adaptive coding Vectors Shape Bit rate Degradation Speech analysis Speech synthesis Laboratories Signal analysis

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An efficient hybrid ARQ protocol for point-to-multipoint communication and its throughput performance

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 1999年第5期48卷 1688-1698页

作者： Djandji, H Philips Mobile Phones F-72004 Le Mans France

This paper presents a new point-to-multipoint communication protocol, the nonselective repeat (NSR) protocol for error control over broadcast channels [1], [2], It is a hybrid forward-error-correction (FEC)/automatic-repeat-request (ARQ) scheme, based on the adaptive coding technique using incremental redundancy of Mandelbaum [3]. The FEC code is a rate-compatible punctured and shortened Reed-Solomon (RS) code, used for error correction only. The scheme is most attractive in situations where error occurrences are almost independent between the recipients of the messages. The throughput performance of the NSR protocol is analyzed in terms of all the parameters involved. Analysis shows that NSR significantly out-performs all the existing pure ARQ broadcast schemes. It is also shown that, even with a large number of recipients, NSR achieves performance which stays close to the capacity of the broadcast q-ary erasure channel, where q = 2(m) and m is the size in bits of a transmitted packet. Furthermore, on slow Rayleigh fading channels, this protocol is expected to provide better throughput performance than other hybrid ARQ protocols.

关键词： Rayleigh channels Reed-Solomon codes adaptive codes automatic repeat request broadcast channels forward error correction multiuser channels packet radio networks protocols time division multiple access ARQ broadcast schemes FEC code NSR protocol TDMA ada Raleigh fading channels Automatic repeat request multiuser channels Packet radio networks Reed-Solomon codes Forward error correction broadcast channels time division multiple access adaptive coding ADA (PROGRAMMING LANGUAGE) protocols HARQ

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Advanced communications technology satellite (ACTS) fade compensation protocol impact on very small-aperture terminal bit error rate performance

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IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS 1999年第2期17卷 173-179页

作者： Cox, CB Coney, TA NASA Lewis Res Ctr Cleveland OH 44135 USA Analex Corp Brook Pk OH 44142 USA

The Advanced Communications Technology Satellite (ACTS) communications system operates at Ka band. ACTS uses an adaptive rain fade compensation protocol to reduce the impact of signal attenuation resulting from propagation effects. The purpose of this paper is to present the results of an analysis characterizing the improvement in VSAT performance provided by this protocol. The metric for performance is VSAT bit error rate (BER) availability. The acceptable availability defined by communication system design specifications is 99.5% for a BER of 5E-7 or better. VSAT EER availabilities with and without rain fade compensation are presented. A comparison shows the improvement in EER availability realized with rain fade compensation. Results are presented for an eight-month period and for 24 months spread over a three-year period. The two time periods represent two different configurations of the fade compensation protocol.

关键词： adaptive coding attenuation propagation rain satellite communication satellites

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adaptive coding for slotted DS-SSMA packet radio systems

Adaptive coding for slotted DS-SSMA packet radio systems

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MILCOM, Military Communications Conference

作者： Qian Zhang T.F. Wong J.S. Lehnert Purdue University West Lafayette IN USA

In order to achieve adaptive coding, the type-II hybrid ARQ protocol is applied to a slotted direct-sequence spread-spectrum multiple-access (DS-SSMA) packet radio system with a finite number of users. Two-dimensional Markov chains are employed to model the system dynamics. Based on this model, the performance of the type-II hybrid ARQ protocol is upper and lower bounded by considering, respectively, a superior scheme and an inferior scheme. The steady state throughput and delay performance of the two bounding schemes are obtained. Moreover, the optimal retransmission policy is found for each fixed input load.

关键词： adaptive coding Packet radio networks Automatic repeat request Protocols Throughput Delay Feedback Radio transmitters Spread spectrum communication Steady-state

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Variable rate adaptive modulation for DS-CDMA

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IEEE TRANSACTIONS ON COMMUNICATIONS 1999年第4期47卷 577-589页

作者： Vincent, VKN Maric, SV Univ Hong Kong Dept Elect & Elect Engn Hong Kong Peoples R China Qualcomm Inc San Diego CA 92121 USA

An adaptive coding scheme is introduced for a discrete sequence code-division multiple-access system. The system uses noncoherent M-ary orthogonal modulation with RAKE receiver and power control. Both a fast fading channel and a combined fast fading, shadowing and power control channel are considered. Analytical bounds and simulations are done to evaluate the performance of the system. It is found that there are significant improvement in the average throughput and the bit-error-rate performance in the adaptive coding scheme. The amount of improvement drops with the increase of diversity branches used, More importantly, it is found that adaptive coding scheme is relatively robust to shadowing, while fix-rate codes are ineffective in the shadowing environment. Finally, adaptive coding scheme is found to be robust to mobile speed, feedback delay, and finite interleaving depth.

关键词： adaptive coding code-division multiple-access modulation

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adaptive coding and modulation for spread-spectrum signals

Adaptive coding and modulation for spread-spectrum signals

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IEEE Conference on Vehicular Technology (VTC)

作者： V. Wen-Kai Cheng W.E. Stark EECS Department University of Michigan Ann Arbor MI USA

We consider coding and edulation schemes for direct-sequence spread-spectrum (DS-SS) systems with multiple-access (MA) interference in a fading environment. Our goal is to be able to adapt the code to different environments. Communication in an environment with a large amount of interference will require a lower transmission (code) rate while small levels of interference will allow a high rate transmission. The following coded modulation systems are considered: a conventional 64-ary orthogonal (M/sub 64/) code, the trellis coded Nordstrom-Robinson (TCNR) code, and the trellis coded Reed-Muller (TCRM) code. Each of these is concatenated with a (63, k) Reed-Solomon (RS) outer code. The performance measure of interest is the error probability and throughput. These are evaluated by making a Gaussian approximation on the multiple-access interference. Our results show, given an error probability requirement, and a certain data rate, a maximum number of users for each of the three DS-SS schemes can be determined. This indicates the receiver can adjust the coding and modulation scheme to achieve the given requirement.

关键词： adaptive coding Modulation coding Spread spectrum communication Multiple access interference Error probability Fading Concatenated codes Reed-Solomon codes Throughput Gaussian approximation

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The construction of Huffman codes is a submodular ("convex") optimization problem over a lattice of binary trees

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SIAM JOURNAL ON COMPUTING 1999年第5期28卷 1875-1905页

作者： Parker, DS Ram, P Univ Calif Los Angeles Dept Comp Sci Los Angeles CA 90095 USA Xerox Corp El Segundo CA 90245 USA

We show that the space of all binary Huffman codes for a finite alphabet defines a lattice, ordered by the imbalance of the code trees. Representing code trees as path-length sequences, we show that the imbalance ordering is closely related to a majorization ordering on real-valued sequences that correspond to discrete probability density functions. Furthermore, this tree imbalance is a partial ordering that is consistent with the total orderings given by either the external path length (sum of tree path lengths) or the entropy determined by the tree structure. On the imbalance lattice, we show the weighted path-length of a tree (the usual objective function for Huffman coding) is a submodular function, as is the corresponding function on the majorization lattice. Submodular functions are discrete analogues of convex functions. These results give perspective on Huffman coding and suggest new approaches to coding as optimization over a lattice.

关键词： Huffman coding adaptive coding prefix codes enumeration of trees lattices combinatorial optimization convexity submodular functions entropy tree imbalance Schur convex functions majorization Moebius inversion combinatorial inequalities Fortuin-Kasteleyn-Ginibre (FKG) inequality quadrangle inequality Monge matrices dynamic programming greedy algorithms

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A byte-wise normalization method in arithmetic coding

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SOFTWARE-PRACTICE & EXPERIENCE 1999年第4期29卷 299-309页

作者： Wu, PC Natl Penghu Inst Marine & Management Technol Dept Informat Management Penghu Taiwan Natl Penghu Inst Marine & Management Technol Dept Comp Sci & Informat Engn Penghu Taiwan

Allocating small code space to frequent symbols can achieve data compression. The well-known Huffman coding technique is the optimal method that allocates code space in an integral number of bits. By allocating code space precisely to a fraction of a bit, arithmetic coding achieves a better efficiency than Huffman coding. In arithmetic coding, the range of the code points is usually kept in [1/2, 1) by applying a normalization technique. This paper proposes a method that adjusts the range in [1/2(d), 1), The range is allowed to decrease below 1/2 without applying normalization each time. This method reduces the number of shifts in normalization to lid. When d = 8, normalization can be implemented byte-by-byte. This is particularly advantageous to applications where inputs and outputs are handled in bytes. We apply this method both to adaptive coding and semi-static coding. Timing results on four platforms are presented. Copyright (C) 1999 John Whey & Sons, Ltd.

关键词： data compression efficiency adaptive coding semi-static coding file compression

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Variable-length constrained-storage tree-structured vector quantization

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IEEE TRANSACTIONS ON IMAGE PROCESSING 1999年第3期8卷 321-331页

作者： Bayazit, U Pearlman, WA Toshiba Amer Elect Comp & Syst Engn San Jose CA 95131 USA Rensselaer Polytech Inst Dept Elect Comp & Syst Engn Troy NY 12180 USA

Constrained storage vector quantization, (CSVQ), introduced by Chan anti Gersho [2]-[4], allows for the stagewise design of balanced tree-structured residual vector quantization codebooks with low encoding and storage complexities, On the other hand, it has been established in [9], [11], and [12] that variable-length tree-structured vector quantizer (VLTSVQ) yields better coding performance than a balanced tree-structured vector quantizer and mag even outperform a full-search vector quantizer due to the nonuniform distribution of rate among the subsets of its input space, The variable-length constrained storage tree-structured vector quantization (VLCS-TSVQ) algorithm presented in this paper utilizes the codebook sharing by multiple vector sources concept as in CSVQ to greedily grow an unbalanced tree structured residual vector quantizer with constrained storage. It is demonstrated by simulations on test sets from various synthetic one-dimensional (I-D) sources and real-world images that the performance of VLCS-TSVQ, whose codebook storage complexity varies linearly with rate, can come very close to the performance of greedy growth VLTSVQ of [11] and [12], The dramatically reduced size of the overall codebook allows the transmission of the codevector probabilities as side information for source adaptive entropy coding.

关键词： adaptive coding tree data structures vector quantization

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An improved data structure for cumulative probability tables

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SOFTWARE-PRACTICE & EXPERIENCE 1999年第7期29卷 647-659页

作者： Moffat, A Univ Melbourne Dept Comp Sci & Software Engn Parkville Vic 3052 Australia

In 1994 Peter Fenwick at the University of Auckland devised an elegant mechanism for tracking the cumulative symbol frequency counts that are required for adaptive arithmetic coding. His structure spends O(log n) time per update when processing the sth symbol in an alphabet of n symbols. In this note we propose a small but significant alteration to this mechanism, and reduce the running time to O O(log (1 + s)) time per update. If a probability-sorted alphabet is maintained, so that symbol s in the alphabet is the sth most frequent, the cost of processing each symbol is then linear in the number of bits produced by the arithmetic coder. Copyright (C) 1999 John Wiley & Sons, Ltd.

关键词： compression adaptive coding dynamic coding arithmetic coding data structure

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