Showing papers on "Codebook published in 2009"

Recognising action as clouds of space-time interest points

Abstract: Much of recent action recognition research is based on space-time interest points extracted from video using a Bag of Words (BOW) representation. It mainly relies on the discriminative power of individual local space-time descriptors, whilst ignoring potentially valuable information about the global spatio-temporal distribution of interest points. In this paper, we propose a novel action recognition approach which differs significantly from previous interest points based approaches in that only the global spatiotemporal distribution of the interest points are exploited. This is achieved through extracting holistic features from clouds of interest points accumulated over multiple temporal scales followed by automatic feature selection. Our approach avoids the non-trivial problems of selecting the optimal space-time descriptor, clustering algorithm for constructing a codebook, and selecting codebook size faced by previous interest points based methods. Our model is able to capture smooth motions, robust to view changes and occlusions at a low computation cost. Experiments using the KTH and WEIZMANN datasets demonstrate that our approach outperforms most existing methods.

Beyond the Euclidean distance: Creating effective visual codebooks using the Histogram Intersection Kernel

Abstract: Common visual codebook generation methods used in a Bag of Visual words model, e.g. k-means or Gaussian Mixture Model, use the Euclidean distance to cluster features into visual code words. However, most popular visual descriptors are histograms of image measurements. It has been shown that the Histogram Intersection Kernel (HIK) is more effective than the Euclidean distance in supervised learning tasks with histogram features. In this paper, we demonstrate that HIK can also be used in an unsupervised manner to significantly improve the generation of visual codebooks. We propose a histogram kernel k-means algorithm which is easy to implement and runs almost as fast as k-means. The HIK codebook has consistently higher recognition accuracy over k-means codebooks by 2–4%. In addition, we propose a one-class SVM formulation to create more effective visual code words which can achieve even higher accuracy. The proposed method has established new state-of-the-art performance numbers for 3 popular benchmark datasets on object and scene recognition. In addition, we show that the standard k-median clustering method can be used for visual codebook generation and can act as a compromise between HIK and k-means approaches.

Performance of Orthogonal Beamforming for SDMA With Limited Feedback

Abstract: On the multiantenna broadcast channel, the spatial degrees of freedom support simultaneous transmission to multiple users. The optimal multiuser transmission, which is known as dirty paper coding, is not directly realizable. Moreover, close-to-optimal solutions such as Tomlinson-Harashima precoding are sensitive to channel state information (CSI) inaccuracy. This paper considers a more practical design called per user unitary and rate control (PU2RC), which has been proposed for emerging cellular standards. PU2RC supports multiuser simultaneous transmission, enables limited feedback, and is capable of exploiting multiuser diversity. Its key feature is an orthogonal beamforming (or precoding) constraint, where each user selects a beamformer (or precoder) from a codebook of multiple orthonormal bases. In this paper, the asymptotic throughput scaling laws for PU2RC with a large user pool are derived for different regimes of the signal-to-noise ratio (SNR). In the multiuser interference-limited regime, the throughput of PU2RC is shown to logarithmically scale with the number of users. In the normal SNR and noise-limited regimes, the throughput is found to scale double logarithmically with the number of users and linearly with the number of antennas at the base station. In addition, numerical results show that PU2RC achieves higher throughput and is more robust against CSI quantization errors than the popular alternative of zero-forcing beamforming if the number of users is sufficiently large.

Mode switching for the multi-antenna broadcast channel based on delay and channel quantization

Abstract: Imperfect channel state information degrades the performance of multiple-input multiple-output (MIMO) communications; its effects on single-user (SU) and multiuser (MU) MIMO transmissions are quite different. In particular, MU-MIMO suffers from residual interuser 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 in the broadcast channel due to delay and channel quantization. Accurate closed-form approximations are derived for 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 its spatial multiplexing gain with a fixed delay or fixed codebook size. Based on derived achievable rates, a mode switching algorithm is proposed, which switches between SU and MU-MIMO modes to improve the spectral efficiency based on average signal-to-noise ratio (SNR), 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, and they 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.

Antenna location design for generalized distributed antenna systems

Abstract: A squared distance criterion for antenna location design in generalized distributed antenna systems (GDAS) is proposed to maximize the cell averaged ergodic capacity. The criterion requires the antenna port locations minimize the expectation of the squared distance between a randomly distributed user and the nearest antenna port. This is equivalent to codebook design in vector quantization. For uniform user distribution, we can easily derive analytical expressions for antenna locations. For more general user distribution, we can obtain numerical results using the codebook design algorithm. Applying the proposed criterion to circular-layout GDAS with uniform user distribution and linear cell with non-uniform user distribution, we achieve near optimal performance.

Codebook generation system and associated methods

Abstract: The invention relates to a codebook generation system and associated methods. The invention are generally directed to communication systems and, more particularly, to a codebook generation system and associated methods. In one embodiment, a device is disclosed and comprises a processor circuit. The processor circuit is arranged to select a pre-coding matrix based on an index which is received from remote equipment through a communication channel of a closed-loop multi-input multi-output (MIMO) orthogonal frequency-division multiplexing (OFDMA) system. The pre-coded matrix is built through applying conversion on one or multiple vectors. Information is precoded through the pre-coding matrix for transmitting through a plurality of transmitter antennae. The invention further discloses the codebook generation system and the associated methods.

BER Analysis and Optimization of Generalized Spatial Modulation in Correlated Fading Channels

Abstract: We propose and analyze a generalized spatial mod- ulation scheme, where depending on the bits to be transmitted a certain data symbol as well as a certain beamforming vector is chosen. The receiver then has to estimate both the used beamforming vector and the transmitted data symbol for being able to reconstruct the originally transmitted bit sequence. We analyze our scheme theoretically by deriving a very tight upper bound on the average bit error rate (BER) for arbitrary symbol constellations and beamforming codebooks in correlated Rayleigh fading channels. Based on this bound, we determine a design criterion for optimizing the used beamforming codebook in presence of spatial correlation at the transmitter-side. Simulation results are shown to be in excellent agreement with our analytical calculated BERs and they illustrate the significant performance gains that can be obtained with our generalized scheme compared to conventional spatial modulation.

Beamforming Codebook Design and Performance Evaluation for 60GHz Wideband WPANs

Abstract: The paper proposes a codebook design to support beamforming mechanism in a wide band millimeter-wave 60GHz wireless personal area networks (60GHz WPANs) in a realistic millimeter-wave environment. The codebooks are designed sym- metrically in order to mitigate the possible beam shift due to the large differences of wave lengthes at different sub-bands of a wide band communication system. In order to provide a high data rate and high performance with minimum power consumption in 60GHz systems, the codebooks are generated with 90 degree phase resolution without amplitude adjustment. The codebooks are designed for different numbers of antenna elements, supporting a multitude of antenna configurations. The paper provides codebook design mechanism, some example codebooks and some analysis on antenna gain loss due to phase shift errors of phase shifters. Simulation results shows that: (1) To keep the gain loss at the intersections of any two patterns inside the codebook lower than 1dB, the number of patterns inside the codebook shall be at least 2 times of the number of antenna elements used for pattern generation; (2) The designed codebooks are robust to phase shift errors: the gain loss is lower than 1dB with only 10% outage probability when standard deviation of phase shift errors at phase shifters is 0.5 (28.6 degree). The proposed codebooks are a feasible design, they are the key basis of the beamforming protocol in 60GHz WPANs (IEEE 802.15.3c).

Method and apparatus for multiple input multiple output (MIMO) transmit beamforming

Abstract: A wireless communications network is provided. A base station including a multiple antenna array for wireless communication, comprising a codebook, a processor to select a codeword from the codebook and to code data with the selected codeword and a transmitter to transmit the coded data, wherein codewords in the codebook are based on values shown in the table of Claim 1.

On-off random access channels: A compressed sensing framework

Abstract: This paper considers a simple on-off random multiple access channel, where n users communicate simultaneously to a single receiver over m degrees of freedom Each user transmits with probability lambda, where typically lambda n < m << n, and the receiver must detect which users transmitted We show that when the codebook has iid Gaussian entries, detecting which users transmitted is mathematically equivalent to a certain sparsity detection problem considered in compressed sensing Using recent sparsity results, we derive upper and lower bounds on the capacities of these channels We show that common sparsity detection algorithms, such as lasso and orthogonal matching pursuit (OMP), can be used as tractable multiuser detection schemes and have significantly better performance than single-user detection These methods do achieve some near-far resistance but--at high signal-to-noise ratios (SNRs)--may achieve capacities far below optimal maximum likelihood detection We then present a new algorithm, called sequential OMP, that illustrates that iterative detection combined with power ordering or power shaping can significantly improve the high SNR performance Sequential OMP is analogous to successive interference cancellation in the classic multiple access channel Our results thereby provide insight into the roles of power control and multiuser detection on random-access signalling

Learning non-redundant codebooks for classifying complex objects

Abstract: Codebook-based representations are widely employed in the classification of complex objects such as images and documents. Most previous codebook-based methods construct a single codebook via clustering that maps a bag of low-level features into a fixed-length histogram that describes the distribution of these features. This paper describes a simple yet effective framework for learning multiple non-redundant codebooks that produces surprisingly good results. In this framework, each codebook is learned in sequence to extract discriminative information that was not captured by preceding codebooks and their corresponding classifiers. We apply this framework to two application domains: visual object categorization and document classification. Experiments on large classification tasks show substantial improvements in performance compared to a single codebook or codebooks learned in a bagging style.

Codebook design method for multiple input multiple output system and method for using the codebook

Abstract: A multiple input multiple output (MIMO) communication method using a codebook is provided The MIMO communication method may use one or more codebooks and the codebooks may change according to a transmission rank, a channel state of a user terminal, and/or a number of feedback bits The one or more codebooks may be adaptively updated according to a time correlation coefficient of a channel

Real Time Foreground-Background Segmentation Using a Modified Codebook Model

Abstract: Real time segmentation of scene into objects and background is really important and represents an initial step of object tracking. Starting from the codebook method [4] we propose some modifications which show significant improvements in most of the normal and also difficult conditions. We include parameter of frequency for accessing, deleting, matching and adding codewords in codebook or to move cache codewords into codebook. We also propose an evaluation method in order to objectively compare several segmentation techniques, based on receiver operating characteristic (ROC) analysis and on precision and recall method. We propose to summarize the quality factor of a method by a single value based on a weighted Euclidean distance or on a harmonic mean between two related characteristics.

Progressive Feedback For High Resolution Limited Feedback Wireless Communication

Abstract: A system and method is proposed for progressively quantizing channel state information for application in a MIMO (multiple input multiple output) communication system. A method includes computing an estimate of a communications channel between a subscriber unit and a base station, quantizing the estimate with a first codebook, thereby producing a first quantized estimate, quantizing an (n−1)-th quantized estimate with an n-th codebook, thereby producing an n-th quantized estimate, where n is an integer value ranging from 2 to R, R is a total number of quantizations of the estimate, wherein the n-th codebook is a localized codebook. The method also includes incrementing n, repeating the quantizing an (n−1)-th quantized estimate until n=R, and transmitting information based on the R quantized estimates to the base station.

QAM and PSK codebooks for limited feedback MIMO beamforming

Abstract: This paper considers the problem of beamforming in multiple-input multiple-output (MIMO) wireless systems. Assuming perfect channel state information at the receiver, the choice of the beamforming vector is made possible through a noiseless limited-rate feedback of one or more bits per coefficient to the transmitter. This paper proposes the use of beamforming codebooks based on quadrature amplitude modulation (QAM) and phase-shift keying (PSK) constellations, which essentially eliminates the need for storage of the codebook. We show that such codebooks perform arbitrarily close to the perfect feedback case as the constellation size increases, and that full diversity order is achieved. We demonstrate an equivalence between the beamforming codebook search problem with that of noncoherent sequence detection. Based on this we propose fast beamforming vector search algorithms. Monte-Carlo simulations are presented to show that the performance is comparable to the best known codebooks, and that the search complexity can be reduced by several orders of magnitude.

Method and apparatus for channel feedback in a wireless communication system

Abstract: A communication system comprises evolved base nodes (eNBs) communicating via an over-the-air (OTA) link with low mobility user equipment (UE). A network can utilize the eNBs for cooperative beam shaping for interference nulling based upon a number of factors UE (e.g., coordinated multi-point (COMP) optimization for feedback, quality of service (QoS), fairness, etc.). The UE advantageously transmits adaptive rate and payload channel state feedback, trading accuracy versus delay based upon mobility of the UE. Channel coherence across a transmission interval (frequency and/or time invariance) provides an opportunity with sufficiently low mobility for transmitting a larger accuracy feedback report over one or more feedback reports for decoding at the eNB. Reduced quantization error can be realized via multi-level coding, one codebook multiple description coding (MDC), and use of N-best code representations from one codebook with MDC.

Kerdock Codes for Limited Feedback Precoded MIMO Systems

Abstract: Codebook based limited feedback is a practical way to obtain partial channel state information at the transmitter in a precoded multiple-input multiple-output wireless system. In this correspondence, we propose a systematic codebook design. The proposed Kerdock codebook consists of multiple mutually unbiased unitary basis matrices with quaternary alphabet and the identity matrix. We propose to derive the beamforming and precoding codebooks from this base codebook, eliminating the requirement to store multiple codebooks. Furthermore, we show that quaternary alphabet facilitates efficient codebook storage and codeword search. We derive the chordal distance for two and four antenna codebooks, showing that the proposed codebooks compare favorably with prior designs. Monte Carlo simulations compare achievable rates and error rates for different codebooks sizes.

Progressive refinement of beamforming vectors for high-resolution limited feedback

Abstract: Limited feedback enables the practical use of channel state information in multiuser multiple-input multiple-output (MIMO) wireless communication systems. Using the limited feedback concept, channel state information at the receiver is quantized by choosing a representative element from a codebook known to both the receiver and transmitter. Unfortunately, achieving the high resolution required with multiuser MIMO communication is challenging due to the large number of codebook entries required. This paper proposes to use a progressively scaled local codebook to enable high resolution quantization and reconstruction for multiuser MIMO with zero-forcing precoding. Several local codebook designs are proposed including one based on a ring and one based on mutually unbiased bases; both facilitate efficient implementation. Structure in the local codebooks is used to reduce search complexity in the progressive refinement algorithm. Simulation results illustrate sum rate performance as a function of the number of refinements.

Fast codebook search algorithm for vector quantization using sorting technique

Abstract: In this paper we propose partial yet efficient codebook search algorithm which uses sorting technique and uses only comparison. Our proposed algorithm does not use Euclidean distance computation and hence it is fastest as compared to other search methods ES, HOSM, DTPC. Form the results it is observed that proposed algorithm gives more MSE as compared to the exhaustive search method but with good execution speed. We also discuss codebook design methods LBG and FCG. The codebooks of different sizes 128, 256, 512 and 1024 are generated using LBG and FCG algorithm. Both the codebook generation algorithms are compared with respect to the execution speed. All the various search algorithms are implemented on the codebooks of different sizes 128, 256, 512 and 1024 obtained from LBG and FCG algorithms. From the results it is observed that FCG codebook gives better performance parameters MSE and PSNR as compared to LBG codebook and among the search algorithm proposed algorithm gives least time to encode the image with slight degradation in image quality.

On the trade-off between feedback and capacity in measured MU-MIMO channels

Abstract: In this work we study the capacity of multi-user multiple-input multiple-output (MU-MIMO) downlink channels with codebook-based limited feedback using real measurement data. Several aspects of MU-MIMO channels are evaluated. Firstly, we compare the sum rate of different MU-MIMO precoding schemes in various channel conditions. Secondly, we study the effect of different codebooks on the performance of limited feedback MU-MIMO. Thirdly, we relate the required feedback rate with the achievable rate on the downlink channel. Real multi-user channel measurement data acquired with the Eurecom MIMO OpenAir Sounder (EMOS) is used. To the best of our knowledge, these are the first measurement results giving evidence of how MU-MIMO precoding schemes depend on the precoding scheme, channel characteristics, user separation, and codebook. For example, we show that having a large user separation as well as codebooks adapted to the second order statistics of the channel gives a sum rate close to the theoretical limit. A small user separation due to bad scheduling or a poorly adapted codebook on the other hand can impair the gain brought by MU-MIMO. The tools and the analysis presented in this paper allow the system designer to trade-off downlink rate with feedback rate by carefully choosing the codebook.

Method of transmitting precoding information in multiple antenna system

Abstract: A method of transmitting precoding information in a multiple antenna system includes selecting M subbands from a plurality of subbands constituting a whole frequency band in a descending order of a channel quality indicator (CQI), where M is an integer satisfying M>0, and transmitting a first precoding matrix indicator (PMI) for the M subbands and a second PMI for a remaining band, wherein the first PMI is a PMI of a codebook selected from a first codebook set including a plurality of codebooks and the second PMI is a PMI of a codebook selected from a second codebook set including a part of the plurality of codebooks of the first codebook set. Accordingly, precoding information can be effectively transmitted by separately preparing a codebook for a best band and a codebook for a non-selected band.

A multi-sample, multi-tree approach to bag-of-words image representation for image retrieval

Abstract: The state-of-the-art content based image retrieval systems has been significantly advanced by the introduction of SIFT features and the bag-of-words image representation. Converting an image into a bag-of-words, however, involves three non-trivial steps: feature detection, feature description, and feature quantization. At each of these steps, there is a significant amount of information lost, and the resulted visual words are often not discriminative enough for large scale image retrieval applications. In this paper, we propose a novel multi-sample multi-tree approach to computing the visual word codebook. By encoding more information of the original image feature, our approach generates a much more discriminative visual word codebook that is also efficient in terms of both computation and space consumption, without losing the original repeatability of the visual features. We evaluate our approach using both a ground-truth data set and a real-world large scale image database. Our results show that a significant improvement in both precision and recall can be achieved by using the codebook derived from our approach.

Methods and apparatus to generate multiple antennas transmit precoding codebook

Abstract: A device and method for generating a codebook. The device includes a generator. The codebook generator is configured to generate a precoding codebook using an 8-Phase Shift keying (PSK) alphabet-based 4 bits four transmitter (4 TX) and eight transmitter (8 TX) antennas for use in a closed-loop Single User-MIMO(SU-MIMO) scheme. According to aspects of the present disclosure, it is possible to generate a precoding codebook for use in 8 Transmission Antenna systems.

Using a pitch-synchronous residual codebook for hybrid HMM/frame selection speech synthesis

Abstract: This paper proposes a method to improve the quality delivered by statistical parametric speech synthesizers. For this, we use a codebook of pitch-synchronous residual frames, so as to construct a more realistic source signal. First a limited codebook of typical excitations is built from some training database. During the synthesis part, HMMs are used to generate filter and source coefficients. The latter coefficients contain both the pitch and a compact representation of target residual frames. The source signal is obtained by concatenating excitation frames picked up from the codebook, based on a selection criterion and taking target residual coefficients as input. Subjective results show a relevant improvement compared to the basic technique.

Method for avoiding inter-cell interference in multi-cell environment using multiple codebooks

Abstract: A method is disclosed for avoiding inter-cell interference in a closed-loop multiple-input multiple-output (MIMO) system using a plurality of codebooks. A base station of a serving cell transmits information about codebooks used in an interfering cell among the plurality of codebooks to a mobile station. The transmission of the information may be made at the request of the mobile station. Alternatively, the mobile station may directly measure information about codebooks used in the interfering cell among the plurality of codebooks. The mobile station measures restricted precoding matrix indexes (PMIs) or requested PMIs based on the codebook information. The measured PMIs are transmitted to the interfering cell and are used to restrict the use of a PMI in the interfering cell.

Fast Codevector Search Algorithm for 3-D Vector Quantized Codebook

Abstract: This paper presents a very simple and efficient algorithm for codebook search, which reduces a great deal of computation as compared to the full codebook search. The algorithm is based on sorting and centroid technique for search. The results table shows the effectiveness of the proposed algorithm in terms of computational complexity. In this paper we also introduce a new performance parameter named as Average fractional change in pixel value as we feel that it gives better understanding of the closeness of the image since it is related to the perception. This new performance parameter takes into consideration the average fractional change in each pixel value. Keywords—Vector Quantization, Data Compression, Encoding, Searching.

Method and apparatus for performing multiple-input multiple-output wireless communications

Abstract: A method and an apparatus for performing multiple-input multiple-output (MIMO) wireless communications are disclosed. A Node-B may receive an index to a pre-coding matrix in a single user MIMO (SU-MIMO) pre-coding codebook from wireless transmit/receive units (WTRUs) and adaptively perform one of SU-MIMO or multi-user MIMO (MU-MIMO) based on a predetermined criterion. Channel information for performing MU-MIMO may be obtained based on the pre-coding matrix of the SU-MIMO pre-coding codebook. A rank requested by the WTRU may be overridden if the unitary MU-MIMO codebook is a subset of the SU-MIMO pre-coding codebook. If not, a MU-MIMO pre-coding matrix with a largest correlation to the pre-coding matrix may be selected. A WTRU may send a pre-coding matrix for transmission to the WTRU along with a preferred interference matrix. A WTRU may send rank information and multiple right singular vectors for MU-MIMO.

Hybrid beam-forming and beam-switching for OFDM based wireless personal area networks

Abstract: In this paper, we propose a hybrid beam-forming and beam-switching technique for OFDM based wireless personal area networks (WPAN). In order to compromise between performance and computational cost and overheads for the channel side information feedback, the proposed system employs hybrid beam-forming and beam-switching, where the block beam-switching using a predefined beam codebook is used at the transmitter while the optimum per-subcarrier beam-forming is used at the receiver. To verify the performance of the proposed scheme, the effective SNR gain over the single antenna transmission system is investigated along with the spectral efficiency bound for some of the channels developed by the IEEE 802.15.3c task group. For comparison, the performance of the optimum per-subcarrier beam-forming and the block beam-switching are also examined.