Codebook

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

Efficient coding of DCT coefficients by joint position-dependent encoding

Abstract: In a typical MC-DCT encoding scheme, a large portion of the bit rate is used to encode the location and amplitude information of the nonzero quantized DCT coefficients. Therefore efficient encoding of the DCT coefficients is extremely important. We describe the joint position-dependent encoding (PDE) approach to encode the DCT coefficients. Joint PDE exploits the variations in statistical properties of the runlengths and amplitudes as a function of position by introducing a set of 2-D codebooks in which each quantized DCT coefficient is assigned to one codebook in the set based on its location. Utilizing an MPEG-2 codec, we compare the bit rates using the joint PDE variable length codes (VLCs) with the bit rates produced by the MPEG-2 VLCs. We also examine how performance is affected by the number of codebooks.

Large-scale robust visual codebook construction

Abstract: The web-scale image retrieval system demands a large-scale visual codebook, which is difficult to be generated by the commonly adopted K-means vector quantization due to the applicability issue. While approximate K-means is proposed to scale up the visual codebook construction it needs to employ a high-precision approximate nearest neighbor search in the assignment step and is difficult to converge, which limits its scalability. In this paper, we propose an improved approximate K-means, by leveraging the assignment information in the history, namely the previous iterations, to improve the assignment precision. By further randomizing the employed approximate nearest neighbor search in each iteration, the proposed algorithm can improve the assignment precision conceptually similarly as the randomized k-d trees, while nearly no additional cost is introduced. The algorithm can be proved to be convergent and we demonstrate that the proposed algorithm improves the quality of the generated visual codebook as well as the scalability experimentally and analytically.

Lexicographic Codebook Design for OFDM With Index Modulation

Abstract: In this paper, we propose a novel codebook design scheme for orthogonal frequency-division multiplexing with index modulation (OFDM-IM) to improve system performance. The optimization process can be implemented efficiently by the lexicographic ordering principle. By applying the proposed codebook design, all subcarrier activation patterns with a fixed number of active subcarriers will be explored. Furthermore, as the number of active subcarriers is fixed, the computational complexity for estimation at the receiver is reduced and the zero-active subcarrier dilemma is solved without involving complex higher layer transmission protocols. It is found that the codebook design can potentially provide a tradeoff between diversity and transmission rate. We investigate the diversity mechanism and formulate three diversity-rate optimization problems for the proposed OFDM-IM system. Based on the genetic algorithm, the method of solving these formulated optimization problems is provided and verified to be effective. Then, we analyze the average block error rate and bit error rate of the OFDM-IM systems applying the codebook design. Finally, all analyses are numerically verified by the Monte Carlo simulations. In addition, a series of comparisons are provided, by which the superiority of the codebook design is confirmed.

Code design for multihop wireless relay networks

Abstract: We consider a wireless relay network, where a transmitter node communicates with a receiver node with the help of relay nodes. Most coding strategies considered so far assume that the relay nodes are used for one hop. We address the problem of code design when relay nodes may be used for more than one hop. We consider as a protocol a more elaborated version of amplify-and-forward, called distributed space-time coding, where the relay nodes multiply their received signal with a unitary matrix, in such a way that the receiver senses a space-time code. We first show that in this scenario, as expected, the so-called full-diversity condition holds, namely, the codebook of distributed space-time codewords has to be designed such that the difference of any two distinct codewords is full rank. We then compute the diversity of the channel, and show that it is given by the minimum number of relay nodes among the hops. We finally give a systematic way of building fully diverse codebooks and provide simulation results for their performance.

Video data compression preprocessor using holographic optical correlation and feedback

Abstract: A method and apparatus for compressing video data images uses optical processing techniques. The method and apparatus perform holographic optical correlation and apply holographic optical correlation in a feedback loop. A codebook of images or primitives for the correlation are stored in a holographic library.