Let G = (V, E) be an undirected graph and C a subset of vertices. If the sets B-r(v) boolean AND C, v is an element of V (respectively, v is an element of V \ C), are all nonempty and different, where B-r(v) denotes t...
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Let G = (V, E) be an undirected graph and C a subset of vertices. If the sets B-r(v) boolean AND C, v is an element of V (respectively, v is an element of V \ C), are all nonempty and different, where B-r(v) denotes the set of all points within distance r from v, we call C an r-identifying code (respectively, an r-locating-dominating code). We prove that, given a graph G and an integer k, the decision problem of the existence of an r-identifying code, or of an r-locating-dominating code, of size at most k in G, is NP-complete for any r. (C) 2002 Elsevier Science B.V. All rights reserved.
We have described an approach to use execution profiles to guide codecompression. Infrequently executed code is compressed using data compression techniques that producecompact representations, and is decompressed dyn...
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We have described an approach to use execution profiles to guide codecompression. Infrequently executed code is compressed using data compression techniques that producecompact representations, and is decompressed dynamically prior to execution as needed. This hasseveral benefits: the compression technique is unhampered by the requirement that the compressedform be executable allowing improvement in the code size reduction achieved; for low executionfrequency thresholds the runtime overheads are small; and finally, no special hardware support isneeded for runtime decompression of compressed code.
A new wavelet-based representation method for arbitrarily-shaped image segments is proposed. The method includes an efficient way to select wavelet basis by using the projection onto convex sets algorithm to approxima...
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A new wavelet-based representation method for arbitrarily-shaped image segments is proposed. The method includes an efficient way to select wavelet basis by using the projection onto convex sets algorithm to approximate the given image segment, with improved image quality.
Because of widespread application in audio and image coding, subband structures are now well understood. Multirate subband implementations provide significant computational advantages while reducing distortion caused ...
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Because of widespread application in audio and image coding, subband structures are now well understood. Multirate subband implementations provide significant computational advantages while reducing distortion caused by sample rate changes. Some so-called perfect reconstruction systems can even eliminate all aliasing distortion caused by tandeming multirate spectral analysis and synthesis, as is the case in coding applications. Despite the widespread popularity in coding, the potential of multirate subband structures for general purpose spectral analysis seems to be largely overlooked. This paper reviews one such structure-the multirate filter bank-and demonstrates its utility as a spectrum analyzer of signals, with particular emphasis on passive sonar. The main advantage of the multirate filter bank is that it provides adjustable time-frequency resolution, and in fact, is shown to be a generalization of the Discrete Fourier Transform. Issues of aliasing, computation, and latency are discussed and passive sonar data sets are used for illustration.
In the matter of channel coding and spectral efficiency, up to the invention of turbo codes, 3 dB or more stood between what the theory promised and what real systems were able to offer. This gap has now been removed,...
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In the matter of channel coding and spectral efficiency, up to the invention of turbo codes, 3 dB or more stood between what the theory promised and what real systems were able to offer. This gap has now been removed, allowing communication systems to be designed with quasi-optimum performance. Ten years after the first publication on this new technique, turbo codes have commenced their practical service.
This article describes enhancements to the physical layer design of single-carrier (1x) cdma2000(R) wireless networks introduced by Revision C of the IS-2000 standard (commonly referred to as 1xEV-DV). These improveme...
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This article describes enhancements to the physical layer design of single-carrier (1x) cdma2000(R) wireless networks introduced by Revision C of the IS-2000 standard (commonly referred to as 1xEV-DV). These improvements are mainly for the support of high-speed wireless packet data service on the forward (base station to mobile station) link. A new shared channel, the forward packet data channel, F-PDCH, is introduced to significantly increase spectral efficiency. This is accomplished through smart, channel-dependent scheduling of base sation, BS, resources by taking advantage of the delay-tolerant nature of data traffic. This shared channel utilizes fast link adaptation through adaptive modulation and coding supported by the feedback of channel quality information. A form of hybrid ARQ Type II technique commonly referred to as asynchronous adaptive incremental redundancy compensates for frame error events due to imperfect link adaptation. The impact of the new channel on voice capacity of the system is designed to be minimal because the F-PDCH utilizes resources that are not consumed by real-time users.
This article presents a tutorial overview of the class of concatenated convolutional codes with interleavers, also known as turbo-like codes. They are powerful codes, formed by a number of encoders connected through i...
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This article presents a tutorial overview of the class of concatenated convolutional codes with interleavers, also known as turbo-like codes. They are powerful codes, formed by a number of encoders connected through interleavers, endowed by a decoding algorithm that splits the decoding burden into separate decoding of each individual code. Refinement of successive estimates of the information sequence is obtained by iterating the procedure of passing from one decoder to the other likelihood information decorrelated by the interleaver action. The key issues of code analysis and design are covered at the level of broad comprehension, without paying attention to analytical details.
Error control coding is a key element of any digital wireless communication system, minimizing the effects of noise and interference on the transmitted signal at the physical layer. In 3G mobile cellular wireless syst...
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Error control coding is a key element of any digital wireless communication system, minimizing the effects of noise and interference on the transmitted signal at the physical layer. In 3G mobile cellular wireless systems, error control coding must accommodate both voice and data terms of latency, throughput, and the impact of errors on the user application. At the base station, dedicated hardware or readily reconfigurable components area needed to address the concurrent coding and decoding demands of a large number of users with different call parameters. In contrast, the encoder,and decoder at the UE are dedicated to a single call setup which changes infrequently. In designing encoder and decoder solutions for 3G wireless systems, not only are the performance issues important, but also the costs. Cellular wireless infrastructure manufacturers need to reduce costs, maximize system reuse, and increased flexibility in order to compete in the market. Furthermore, future-proofing a network is a primary concern due to the high cost of deployment. For the UE, power consumption (battery life) and size are key constraints in addition to manufacturing costs. This article considers the 3G decoder design problem and, using case studies, describes two 3G decoder solutions using ASICs. The first device is targeted for base station deployment and is based on a unified architecture for convolutional and turbo decoding. The second device is a dedicated high-speed radix-4 logMAP turbo decoder targeted for UE, motivated by the requirements for high-speed downlink packet access. Both devices have been fabricated in 0.18 mum CMOS technology, and while optimized for either base station or UE, may be used in both applications.
Low-density parity-check codes, turbo codes, and indeed most practically decodable capacity-approaching error correcting codes can all be understood as codes defined on graphs. Graphs not only describe the codes, but,...
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Low-density parity-check codes, turbo codes, and indeed most practically decodable capacity-approaching error correcting codes can all be understood as codes defined on graphs. Graphs not only describe the codes, but, more important, they structure the operation of the sum-product decoding algorithm (or one of many possible variations), which can be used for iterative decoding. Such coding schemes have the potential to approach channel capacity, while maintaining reasonable decoding complexity. In this tutorial article we review factor graphs, which can be used to describe codes and the joint probability distributions that must be dealt with in decoding. We also review the sum-product algorithm, and show how this algorithm leads to iterative decoding algorithms for codes defined on graphs.
The optimal placement of a run-length coding extension to a dictionary-based lossless data compression algorithm is investigated. A hardware implementation of the proposed extension is completed and integrated into an...
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The optimal placement of a run-length coding extension to a dictionary-based lossless data compression algorithm is investigated. A hardware implementation of the proposed extension is completed and integrated into an existing design. The new hardware is benchmarked against commercially available software and hardware compression methods. Run-length coding replaces repetitive, identical sequences of a symbol with a pair formed by a code indicating the repeating symbol plus a code indicating the length or number of repetitions that occurred. This method of coding is of limited use for general compression due to its relatively poor performance. However, good results can be achieved when used as an extension to a general lossless data compression algorithm where it can improve compression, targeting the coding of repetitive data formats such as zeroes in memory or fax pages or a uniform colour in image backgrounds. It is shown that the run-length coding method can be extended to support more complex repeating patterns with little extra cost in terms of hardware or speed but providing significant superior compression performance.
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