Codebook

About: Codebook is a research topic. Over the lifetime, 8492 publications have been published within this topic receiving 115995 citations.

Fundamental issues of multiple accessing

Abstract: : Fundamental issues of multiple accessing are identified. These issues include transmitter asynchronism, variability of the set of active users, feedback, and degree of codebook knowledge among the users. Various multiple access schemes are examined under these issues. These issues are subsequently modeled and analysed using an information theoretic framework. We discover that the capacity region of the asynchronous multiple access channel is different from that of the synchronous channel. For communication systems with users having random message generation time, we demonstrate that its channel capacity resembles that of an asynchronous channel even though the users are synchronous, if decoding delay is constrained to be much smaller than the message inter- arrival time. We investigate communication with restricted decoder structure. New information theoretic quantities that incorporate the decoding metric used are discovered and examined. Using these quantities, we provide a rigorous and novel treatment for the theory of jamming. These mathematical techniques provide insight for achieving reliable communication in a multiple access environment where each user may not know the codebook of the other users and a jammer may be present. We then apply the general theory developed to three specific asynchronous channel without feedback, namely the OR channel, the spread spectrum channel and the collision channel. Practical and novel coding schemes are suggested. Maximum throughput, error rate and decoding complexity are analysed.

Hierarchical Method for Foreground Detection Using Codebook Model

Abstract: This paper presents a hierarchical scheme with block-based and pixel-based codebooks for foreground detection. The codebook is mainly used to compress information to achieve a high efficient processing speed. In the block-based stage, 12 intensity values are employed to represent a block. The algorithm extends the concept of the block truncation coding, and thus it can further improve the processing efficiency by enjoying its low complexity advantage. In detail, the block-based stage can remove most of the backgrounds without reducing the true positive rate, yet it has low precision. To overcome this problem, the pixel-based stage is adopted to enhance the precision, which also can reduce the false positive rate. Moreover, the short-term information is employed to improve background updating for adaptive environments. As documented in the experimental results, the proposed algorithm can provide superior performance to that of the former related approaches.

A Perturbation Method for Evaluating Background Subtraction Algorithms

Abstract: We introduce a performance evaluation methodology called Perturbation Detection Rate (PDR) analysis, for measuring performance of background subtraction (BGS) algorithms. It has some advantages over the commonly used Receiver Operation Characteristics (ROC) analysis. Specifically, it does not require foreground targets or knowledge of foreground distributions. It measures the sensitivity of a BGS algorithm in detecting low contrast targets against background as a function of contrast, also depending on how well the model captures mixed (moving) background events. We compare four algorithms having similarities and differences. Three are in [2, 3, 5] while the fourth is recently developed, called Codebook BGS. The latter algorithm quantizes sample background values at each pixel into codebooks which represent a compressed form of background model for a long image sequence.

Encoder, decoder, encoding method, and decoding method

Abstract: An encoder, decoder, encoding method, and decoding method enabling acquisition of high-quality decoded signal in scalable encoding of an original signal in first and second layers even if the second or upper layer section performs low bit-rate encoding In the encoder, a spectrum residue shape codebook (305) stores candidates of spectrum residue shape vectors, a spectrum residue gain codebook (307) stores candidates of spectrum residue gains, and a spectrum residue shape vector and a spectrum residue gain are sequentially outputted from the candidates according to the instruction from a search section (306) A multiplier (308) multiplies a candidate of the spectrum residue shape vector by a candidate of the spectrum residue gain and outputs the result to a filtering section (303) The filtering section (303) performs filtering by using a pitch filter internal state set by a filter state setting section (302), a lag T outputted by a lag setting section (304), and a spectrum residue shape vector which has undergone gain adjustment

DFT-Based Beamforming Weight-Vector Codebook Design for Spatially Correlated Channels in the Unitary Precoding Aided Multiuser Downlink

Abstract: The DFT-based beamforming weight-vector codebook is considered as an effective design for spatially correlated channels. In this paper, we demonstrate that when the antenna elements are uniformly spaced as well as linearly arranged, and the channels are spatially correlated, the codewords in a DFT-based beaforming weight-vector codebook approximately match the distribution of the optimal beamforming weight-vectors. As a result, the DFT-based codebook is indeed effective. Furthermore, we also demonstrate that if the antenna elements are uniformly spaced and circulary arranged, the statistical distribution of the optimal beamforming weight-vectors becomes different. We will demonstrate that in this scenario the DFT-based codebook will no longer outperform the Grassmannian codebook, which has not been shown in previous studies. Finally, an algorithm is proposed for constructing the DFT-based precoding matrix, which outperforms the conventional algorithm by ensuring the orthogonality of the precoding matrix.