Showing papers on "Codebook published in 2008"

Kernel Codebooks for Scene Categorization

Abstract: This paper introduces a method for scene categorization by modeling ambiguity in the popular codebook approach. The codebook approach describes an image as a bag of discrete visual codewords, where the frequency distributions of these words are used for image categorization. There are two drawbacks to the traditional codebook model: codeword uncertainty and codeword plausibility. Both of these drawbacks stem from the hard assignment of visual features to a single codeword. We show that allowing a degree of ambiguity in assigning codewords improves categorization performance for three state-of-the-art datasets.

Unifying discriminative visual codebook generation with classifier training for object category recognition

Abstract: The idea of representing images using a bag of visual words is currently popular in object category recognition. Since this representation is typically constructed using unsupervised clustering, the resulting visual words may not capture the desired information. Recent work has explored the construction of discriminative visual codebooks that explicitly consider object category information. However, since the codebook generation process is still disconnected from that of classifier training, the set of resulting visual words, while individually discriminative, may not be those best suited for the classifier. This paper proposes a novel optimization framework that unifies codebook generation with classifier training. In our approach, each image feature is encoded by a sequence of ldquovisual bitsrdquo optimized for each category. An image, which can contain objects from multiple categories, is represented using aggregates of visual bits for each category. Classifiers associated with different categories determine how well a given image corresponds to each category. Based on the performance of these classifiers on the training data, we augment the visual words by generating additional bits. The classifiers are then updated to incorporate the new representation. These two phases are repeated until the desired performance is achieved. Experiments compare our approach to standard clustering-based methods and with state-of-the-art discriminative visual codebook generation. The significant improvements over previous techniques clearly demonstrate the value of unifying representation and classification into a single optimization framework.

Beamforming in mimo systems

Abstract: A beamforming method comprises transmitting a training sequence from a transmitter array employing a set of beamforming vectors from a beamforming codebook. A receive array employs a combining codebook to acquire channel state information from the received transmissions, and estimates a preferred beamforming vector and a preferred combining vector. At least the preferred beamforming vector (and, optionally, the preferred combining vector) is transmitted back to the transmitter array.

Grassmannian beamforming for MIMO amplify-and-forward relaying

Abstract: We consider the problem of beamforming codebook design for limited feedback half-duplex multiple-input multiple output (MIMO) amplify-and-forward (AF) relay system. In the first part of the paper, the direct link between the source and the destination is ignored. Assuming perfect channel state information (CSI), we show that the source and the relay should map their signals to the dominant right singular vectors of the source-relay and relay-destination channels. For the limited feedback scenario, we prove the appropriateness of Grassmannian codebooks as the source and relay beamforming codebooks based on the distributions of the optimal source and relay beamforming vectors. In the second part of the paper, the direct link is considered in the problem model. Assuming perfect CSI, we derive the optimization problem that identifies the optimal source beamforming vector and show that the solution to this problem is uniformly distributed on the unit sphere for independent and identically distributed (i.i.d) Rayleigh channels. For the limited feedback scenario, we justify the appropriateness of Grassmannian codebooks for quantizing the optimal source beamforming vector based on its distribution. Finally, a modified quantization scheme is presented, which introduces a negligible penalty in the system performance but significantly reduces the required number of feedback bits.

Multi-user mimo feedback and transmission in a wireless communication system

Abstract: The present invention provides a method for feedback and transmission of multi-user (MU) multiple input multiple output (MIMO) in a wireless communication system. The method includes steps of selecting subset codebook or full code book based on traffic load of a base station, and broadcasting the selected codebook to user equipments. In high traffic load, subset codebook is selected, and in low traffic load, full codebook is selected. User stations calculated a channel quality indicator of a spatial codeword vector that is included in the selected codebook. Information of the maximum channel quality indicator is sent to the base station together with a precoder of the user equipment. The base station selects user equipments based on the information of the maximum channel quality indicator and precoder, and transmits precoder signal and data signal to the user equipments. The present invention also provides a system for the base station that causes the base station to perform the above mentioned operations.

On transceiver design and channel quantization for downlink multiuser MIMO systems with limited feedback

Abstract: We consider a MIMO broadcast channel where both the transmitter and receivers are equipped with multiple antennas. Channel state information at the transmitter (CSIT) is obtained through limited (i.e., finite-bandwidth) feedback from the receivers that index a set of precoding vectors contained in a predefined codebook. We propose a novel transceiver architecture based on zero-forcing beamforming and linear receiver combining. The receiver combining and quantization for CSIT feedback are jointly designed in order to maximize the expected SINR for each user. We provide an analytic characterization of the achievable throughput in the case of many users and show how additional receive antennas or higher multiuser diversity can reduce the required feedback rate to achieve a target throughput.We also propose a design methodology for generating codebooks tailored for arbitrary spatial correlation statistics. The resulting codebooks have a tree structure that can be utilized in time-correlated MIMO channels to significantly reduce feedback overhead. Simulation results show the effectiveness of the overall transceiver design strategy and codebook design methodology compared to prior techniques in a variety of correlation environments.

Codebook generating method and apparatus for generating a codebook for multi-polarized multiple-input multiple-output (mimo) systems

Abstract: A method of generating a codebook for a multiple-input multiple-output (MIMO) system is provided. The codebook generation method includes: assigning a single-polarized precoding matrix to diagonal blocks among a plurality of blocks arranged in a block diagonal format in which a number of diagonal blocks corresponds to a number of polarization directions of transmitting antennas; and assigning a zero matrix to remaining blocks excluding the diagonal blocks.

An Approach to Information Hiding in Low Bit-Rate Speech Stream

Abstract: In this paper we introduce a novel codebook partition algorithm for quantization index modulation (QIM), which is applied to information hiding in instant low bit-rate speech stream. The QIM method divides the codebook into two parts, each representing '0' and '1' respectively. Instead of randomly partitioning the codebook, the relationship between codewords is considered. The proposed algorithm - complementary neighbor vertices (CNV) guarantees that every codeword is in the opposite part to its nearest neighbor, and the distortion is limited by a bound. The feasibility of CNV is proved with graph theory. Moreover, in our work the secret message is embedded in the field of vector quantization index of LPC coefficients, getting the benefit that the distortion due to QIM is lightened adaptively by the rest of the encoding procedure. Experiments on iLBC and G.723.1 verify the effectiveness of the proposed method. Both objective and subjective assessments show the proposed method only slightly decreases the speech quality to an indistinguishable degree. The hiding capacity is no less than 100 bps. To the best of our knowledge, this is the first work adopting graph theory to improve the codebook partition while using QIM in low bit-rate streaming media.

Variable codebook for mimo system

Abstract: A MIMO wireless communication system employing a variable size preceding codebook is provided. The size of the codebook may be determined by the quality of the wireless transmission channel between a transmitter and a receiver associated with the MIMO wireless communication systems or some other codebook selection criteria. A larger codebook can be employed when the channel quality is high, allowing for significant gains in overall system throughput. In contrast, a smaller codebook can be employed when the cannel quality is poor, so that the added channel overhead associated with a larger code book does not reduce the channel efficiency under circumstances in which a larger codebook would not significantly improve system throughput.

Improving the rates in wireless relay systems through superposition coding

Abstract: We introduce a new two-step relaying scheme based on superposition coding, SC-relaying. In Step 1, the source AS broadcasts a message, created by superposition coding, to the relay AR and the destination AD. After decoding the information from AS, AR relays a part of this message in Step 2, by using a codebook that is adapted to the link AR - AD. The information-theoretic design shows that the proposed scheme can improve the spectral efficiency, attaining almost optimal value. We demonstrate that the SC-relaying can be ported even to the case of uncoded systems, where it is shown how to select the transmission scheme in order to maximize the throughput between the source and the destination.

Nested precoding codebook structures for mino systems

Abstract: Embodiments of the disclosure provide a transmitter (100), a receiver and methods of operating a transmitter and a receiver. In one embodiment, the transmitter is for use with NT transmit antennas and includes a precoder unit (104) configured to precode data for transmission using a precoding matrix selected from a nested codebook (105), wherein the nested codebook provides codebooks corresponding to different transmission layers that are derived from column subsets of multiple NT X NT precoding matrices. The transmitter also includes a transmit unit (106) configured to transmit the precoded data. In another embodiment, the receiver includes a receive unit configured to receive precoded data. The receiver also includes a precoder selection unit configured to select a precoding matrix from a nested codebook for the precoded data, wherein the nested codebook provides codebooks corresponding to different transmission layers that are derived from column subsets of multiple NT X NT precoding matrices.

Technique for encoding/decoding of codebook indices for quantized mdct spectrum in scalable speech and audio codecs

Abstract: Codebook indices for a scalable speech and audio codec may be efficiently encoded based on anticipated probability distributions for such codebook indices. A residual signal from a Code Excited Linear Prediction (CELP)-based encoding layer may be obtained, where the residual signal is a difference between an original audio signal and a reconstructed version of the original audio signal. The residual signal may be transformed at a Discrete Cosine Transform (DCT)-type transform layer to obtain a corresponding transform spectrum. The transform spectrum is divided into a plurality of spectral bands, where each spectral band having a plurality of spectral lines. A plurality of different codebooks are then selected for encoding the spectral bands, where each codebook is associated with a codebook index. A plurality of codebook indices associated with the selected codebooks are then encoded together to obtain a descriptor code that more compactly represents the codebook indices.

Mode Switching for MIMO Broadcast Channel Based on Delay and Channel Quantization

Abstract: Imperfect channel state information degrades the performance of multiple-input multiple-output (MIMO) communications; its effect on single-user (SU) and multi-user (MU) MIMO transmissions are quite different. In particular, MU-MIMO suffers from residual inter-user interference due to imperfect channel state information while SU-MIMO only suffers from a power loss. This paper compares the throughput loss of both SU and MU MIMO on the downlink due to delay and channel quantization. Accurate closed-form approximations are derived for the achievable rates for both SU and MU MIMO. It is shown that SU-MIMO is relatively robust to delayed and quantized channel information, while MU MIMO with zero-forcing precoding loses spatial multiplexing gain with a fixed delay or fixed codebook size. Based on derived achievable rates, a mode switching algorithm is proposed that switches between SU and MU MIMO modes to improve the spectral efficiency, based on the average signal-to-noise ratio (SNR), the normalized Doppler frequency, and the channel quantization codebook size. The operating regions for SU and MU modes with different delays and codebook sizes are determined, which can be used to select the preferred mode. It is shown that the MU mode is active only when the normalized Doppler frequency is very small and the codebook size is large.

Beamforming with limited feedback in amplify-and-forward cooperative networks - [transactions letters]

Abstract: A relay selection approach has previously been shown to outperform repetition-based scheduling for both amplify-and-forward (AF) and decode-and-forward (DF) cooperative networks. The selection method generally requires some feedback from the destination to the relays and the source, raising the issue of the interplay between performance and feedback rate. In this letter, we treat selection as an instance of limited feedback distributed beamforming in cooperative AF networks, and highlight the differences between transmit beamforming in a traditional multi-input single-output (MISO) system and the distributed case. Specifically, Grassmannian line packing (GLP) is no longer the optimal codebook design, and orthogonal codebooks are no longer equivalent to each other. We derive the high signal-to-noise ratio expressions for outage probability and probability of symbol error for unlimited-feedback and selection schemes, which are then used for performance comparisons. The selection protocol is compared to a limited-feedback distributed beamformer that assigns codebooks based on the Generalized Lloyd algorithm (GLA), and one that uses random beam-vectors. The main conclusion is that the performance improvement to be seen using the very complex GLA is small, and that many more feedback bits are required with random beamforming than selection for the same performance. These results indicate that the selection protocol is a very attractive protocol, with low complexity, that provides excellent performance relative to other known methods.

An Efficient Fast Algorithm to Generate Codebook for Vector Quantization

Abstract: In this paper we present a very simple and yet effective algorithm to generate codebook. The algorithm uses sorting method to generate codebook and the codevectors are obtained by using median approach. The proposed algorithm was experimented on six different images each of size 512 x 512 and four different codebooks of sizes 128, 256, 512 and 1024 are generated. The proposed algorithm is found to be much faster than the LBG and KPE algorithm. The performance of this algorithm is better than LBG and KPE algorithms considering MSE, PSNR and execution time. The proposed algorithm gives less MSE as compared to the LBG for the codebooks of sizes 128, 256, 512 & 1024 respectively. It also gives higher PSNR as compared to LBG for the codebooks of various sizes.

Method for codebook design and beamforming vector selection in per-user unitary rate control (pu2rc) system

Abstract: A base station includes a storage unit to store a codebook, wherein the codebook includes a plurality of matrices; a control unit to perform beamforming using the codebook to generate a signal; and a multi-antenna to transmit the signal. For all of the plurality of matrices, all column vectors of a same matrix of the plurality of matrices are orthogonal to each other. For all columns of the plurality of matrices, all column vectors of a same column of all of the plurality of matrices satisfy a Grassmannian line packing (GLP) criterion.

Method and apparatus of codebook-based single-user closed-loop transmit beamforming (SU-CLTB) for OFDM wireless systems

Abstract: A method includes broadcasting, at a transmitter, messages comprising antenna configuration, antenna spacing and a number of antenna of the transmitter and reference signals; generating, at a receiver, a codebook comprising a plurality of antenna beams based on the broadcasted messages; receiving, at the receiver, the broadcasted reference signals; selecting, at the receiver, an antenna beam among the plurality of antenna beams within the codebook in dependence upon a predetermined performance criteria of a data communication system and in dependence upon the broadcasted reference signals; feedbacking to the transmitter, at the receiver, information comprising the antenna beam selected by the receiver; optimizing, at the transmitter, a beamforming process by utilizing the feedback information from the receiver; transmitting, at the transmitter, data signals by utilizing the optimized beamforming process; and receiving and processing, at the receiver, the data signals in dependence upon the selected antenna beams within the codebook.

Cdd precoding for open loop su mimo

Abstract: A method for data transmission, comprises the steps of modulating data to be transmitted via a transmitter into a plurality of modulated symbols, generating a codebook comprising a plurality of codewords, selecting a codeword from the codebook as a precoding matrix by a predetermined cycling selection, precoding the modulated symbols with the precoding matrix selected, and transmitting the precoded modulated symbols.

Codebook selection for transmit beamforming

Abstract: A method select a codebook for transmit beamforming. The method constructs an estimated channel matrix based on a codebook, selects a channel submatrix from the estimated channel matrix, calculates a selection matrix from the channel submatrix; and assigns a steering matrix based on the selection matrix. There may be multiple codebooks and the method may construct an estimated channel matrix, select a channel submatrix, and calculate a selection matrix for each of the codebooks, then select an optimal codebook. The steering matrix is assigned based on the optimal codebook. The steering matrix may be used in steering a transmitted packet. The method may also calculate a post-MIMO equalizer signal-to-noise ratio for a data stream, based on the estimated channel matrix and the selected codebook. A related system is also disclosed. Other embodiments are provided, and each of the embodiments described herein can be used alone or in combination with one another.

Multi-input multi-output space multiplexing precoding method of wireless communication system

Abstract: Using precoded space multiplexing of limited fed back, the method defines a group of set of precoded matrix (i.e. precoded codebook) known by transmitter and receiver. Using algorithm of channel estimation to obtain current state information of channel, the receiver selects an optimal precoded matrix from precoded codebooks according to minimized principles of trace of mean square error matrix as well as through a feedback channel, feeds index of the precoded matrix back to the transmitter within coherence time of channel. Based on the said index of the precoded matrix, the transmitter obtains the precoded matrix, and then carries out precoded operations on vectors of transmit signal based on the precoded matrix. Precoded codebook can be designed based on maximized principle of minimum distance between two norms of projections of subspaces. Using limited bit number fed back, the invention raises communication performance.

Multi-rank beamforming precoding apparatus and method

Abstract: A multi-rank beamforming (MRBF) scheme in which the downlink channel is estimated and an optimal precoding matrix to be used by the MRBF transmitter is determined accordingly. The optimal precoding matrix is selected from a codebook of matrices having a recursive structure which allows for efficient computation of the optimal precoding matrix and corresponding Signal to Interference and Noise Ratio (SINR). The codebook also enjoys a small storage footprint. Due to the computational efficiency and modest memory requirements, the optimal precoding determination can be made at user equipment (UE) and communicated to a transmitting base station over a limited uplink channel for implementation over the downlink channel.

Method and apparatus for feedback in closed loop transmitting

Abstract: A method an apparatus is described for providing feedback for closed-loop transmitting with multiple transmit and receive antennas. The method includes a first step 900 of providing a codebook containing sets of weightings for each data stream of the multiple transmit antennas with each set identified by an index known to a transmitter and a receiver. The same codebook is utilized for any number of data streams up to the number of transmit antennas. A next step 902 includes measuring a composite channel between the transmitter and receiver. A next step 904 includes determining at least one performance metric for each set of weightings in the codebook. A next step 906 includes selecting preferred weightings for each data stream in response to the performance metrics. A next step 908 includes feeding back an index of the preferred weightings to the transmitter for use in subsequent transmissions.

Color Image Segmentation Using Kekre-s Algorithm for Vector Quantization

Abstract: In this paper we propose segmentation approach based on Vector Quantization technique. Here we have used Kekre’s fast codebook generation algorithm for segmenting low-altitude aerial image. This is used as a preprocessing step to form segmented homogeneous regions. Further to merge adjacent regions color similarity and volume difference criteria is used. Experiments performed with real aerial images of varied nature demonstrate that this approach does not result in over segmentation or under segmentation. The vector quantization seems to give far better results as compared to conventional on-the-fly watershed algorithm. Keywords—Image Segmentation,, Codebook, Codevector, data compression, Encoding

Real-time Background Modeling/Subtraction using Two-Layer Codebook Model

Abstract: In this paper, a real-time method for foreground-background segmentation is proposed. This method extracts structure of background and models it in layered codebook. Layered codebook is a simple data structure containing two codebooks that is defined per pixel. The first layer is main codebook, other is cache codebook, and both contain some codewords relative to a pixel. Main codebook models the current background images and cache codebook is used to model new background images during input sequence. Initially main and cache codebooks are empty. Main codebook is constructed during train sequence. During input sequence, foreground-background is segmented and two-layered codebook is updated. Proposed algorithm can model moving backgrounds, multi backgrounds and illumination changes and this is efficient in both memory and computational complexity.

Practical Codebook Design for Limited Feedback Spatial Multiplexing

Abstract: Codebook design for limited feedback Spatial Multiplexing commonly relies on the assumption of i.i.d. Rayleigh fading. It is well known that realistic MIMO channels may exhibit large correlation and/or dominant components and that antennas could be dual-polarized. Hence there is much appeal to come up with design criteria that can cope with such a large distribution of propagation conditions. In this paper, efficient ways to design high-performance and low-complexity codebooks for limited feedback-based Spatial Multiplexing evolving in various environments are provided. In particular, new design criteria are derived for transmit correlated and dual-polarized scenarios. Some of the codebook structures derived in this paper are components of the codebooks accepted in 3GPP LTE. Simulation examples are provided to confirm the proposed criteria.

Efficient MIMO precoding feedback scheme

Abstract: Methods and apparatus for efficiently feeding back preceding information in a multiple input multiple output (MIMO) system. A codebook including a plurality of codebook entries is constructed. A plurality of subsets of codebook entries are defined for the codebook. Each subset includes a plurality of codebook entries. A subset of codebook entries is selected for precoding data in dependence upon a channel condition, and a codebook entry is selected from the subset. Then, a subset index corresponding to the selected subset, and a codebook entry index corresponding to the selected codebook entry within the selected subset, is transmitted as feedback information.