In this paper, a practical adaptive TuCM scheme is proposed, and its adaptive method is described. With some hardware considerations, a suboptimal optimization algorithm which shows that the number of fading regions is variable is put forward. The proposed adaptive TuCM comes within 3 dB of fading channel capacity, exhibits about 3 dB power gain over conventional adaptive TCM, and is easy to realize by hardware. Considering delay and channel estimation error, the BER performance of adaptive TuCM is analyzed and simulated. In the performance analysis, the method of data fitting is applied to obtain the BER expression for TuCM, and a fitting mathematical model is proposed. Results show that adaptive TuCM is very sensitive to delay and channel estimation error. To alleviate these problems, we proposed an improved power adaptation that can make adaptive TuCM practical.

In this letter, the effect of an imperfect channel estimation and carrier frequency offset on the performance of transmit diversity OFDM systems is investigated. For the performance evaluation, the average bit error rate (BER) expression is derived in the presence of the imperfect channel information including both the inherent estimation error and the imperfect windowing error derived in a mismatched channel separation.

The transmission quality in mobile wireless communication systems is affected by not only AWGN but also multi-path fading. Particularly, the Doppler frequency, the delay spread and the Rician factor have a great influence upon the quality over fading channels. This letter proposes the approximate equation for easily calculating the BER in DS-CDMA systems over multi-path fading channels. The validity of the approximate equation is confirmed from the fact that the BER calculated by the equation coincides with that by the computer simulation.

In this letter, we propose a new error protection technique for JPEG2000-coded images and also present its evaluation over an OFDM channel. The method exploits the layer structure of the JPEG2000 codestream, a data embedding technique and a forward error correcting code. The main header and data in the top layer are duplicated and protected by the error correcting code. These data are then embedded into the bottom layer for error recovery purposes. Our method offers several features: preserves the same codestream structure as the one in the JPEG2000 part 1 standard, provides multilevel error protection, and can be combined with the existing error resilience technique. Hence, the method accommodates the new requirements for wireless JPEG2000 (JPWL/JPEG2000 part 11).

In this paper, a spatio-temporal error concealment method of transmission errors for improving visual quality over the wireless channel is proposed, which makes use of geometric information extracted from the surrounding blocks. The geometric information is an isophote that is curves of constant intensity of image. To improve visual quality during video communication, the proposed method smoothly connects the isophotes disconnected due to transmission error using a genetic algorithm (GA) with an isophote constraint. In the proposed method, the error concealment problem is modeled as an optimization problem, which in our case, is solved by a cost function with isophotes constraint that is minimized using a GA. Experimental results shows more visually realistic than other error concealment methods.

A compound error is any combination of burst errors with various burst lengths including random errors. The compound weight of any such error is defined as a kind of combinational metric which is a generalization of Gabidulin's metric. First, we present a fast method for calculating the weight of any word. Based on this method, as an extension of Wadayama's augmenting method in the case of Hamming weight, we propose a method of constructing codes having higher coding rate by augmenting any compound-error-correcting codes. Furthermore, we show some examples of good compound-error-correcting codes obtained by using our augmenting method.

Large number of electronic connectors are widely used in various electronic and telecommunication systems. No matter whether it is optical telecommunications or mobile phone systems, connectors are important links for electronics. Unfortunately connector contacts are exposed in air, they are different from any other electronic components, the contacts are greatly influenced by the environment where they operate. In China, dust and corrosion products are the main contaminants to cause contact failure. Evidently the failed contacts seriously deteriorate the reliability of electronic and telecommunication systems. This paper summarizes the recent achievements obtained by our Lab on the effect of dust and corrosion products to the connector contact failure. Since dust contamination is a very complex problem which is not only popular in China, but also happened in many countries. Continuous studies will be very useful to improve the contact reliability of connectors, setting up new and effective testing methods and standards, building up experimental and computer simulation systems.

This paper deals with a design problem of a robust controller which achieves not only robust stability but also a performance robustness for linear systems with structured uncertainties satisfying matching condition. The performance robustness means that comparing the transient behavior of the uncertain system with a desired one generated by the nominal system, the deterioration of control performance is suppressed. In this approach, the control law consists of a state feedback with the fixed gain designed by using the nominal system, a state feedback with an adaptive gain determined by a parameter adjustment law and a compensation input for the purpose of keeping transient behavior as closely as possible to the desirable one. We show the parameter adjustment law in order to guarantee robust stability and that the condition for the existence of the compensation input is equivalent to the Riccati equation for the standard linear quadratic control problem. Finally, numerical examples are presented.

A novel postprocessing algorithm for concealing spatial block errors in block-based coded images is proposed using block classification with a variable operating region (VOR). In the proposed algorithm, a missing block is classified as flat, edge, or complex based on local information from the surrounding blocks which is extracted using a Sobel operation in a VOR. In this case, the VOR is determined adaptively according to the number of edge directions in the missing block. Using the classification, the flat blocks are then concealed by the linear interpolation (LI) method, the edge blocks are concealed by the boundary multi-directional interpolation (BMDI) method, and the complex blocks are concealed by a combined linear interpolation and boundary matching (CLIBM) method. Experimental results demonstrated that the proposed algorithm improved the PSNR and visual quality of the concealment for both original images and JPEG compressed images, and produced better results than conventional algorithms.

This paper proposes an enhanced method for multiple description coding (MDC) using whitening transform. The MDC using correlating transform is an error resilient coding technique that explicitly adds correlation between two descriptions to enable the estimation of one set from the other when one set is dropped in channel. This paper proposes a method to overcome practical problems that decoder must know statistics of original image in the conventional correlating transform method. The MDC using whitening transform does not need additional statistical information to reconstruct a image because the coefficients whitening transformed have uni-variance statistics. Our experimental results show that the proposed method achieves a good trade-off between the coding efficiency and the reconstruction quality. We obtain that PSNR of image reconstructed from two descriptions is about 0.93 dB higher at the 1.0BPP and PSNR from only one description is about 1.88 dB higher than conventional method at the same rate of 'Lena' image.

We have developed a low-power, high-performance MPEG-4 codec LSI for mobile video applications. This codec LSI is capable of up to CIF 30-fps encoding, making it suitable for various visual applications. The measured power consumption of the codec core was 9 mW for QCIF 15-fps codec operation and 38 mW for CIF 30-fps encoding. To provide an error-robust MPEG-4 codec, we implemented an error-resilience function in the LSI. We describe the techniques that have enabled low power consumption and high performance and discuss our test results.

This paper proposes a hybrid on-demand content delivery scheme employing modified pyramid broadcasting. Our scheme delivers a fixed-sized head portion of the video content to each client individually via an individual channel and the remaining portion via multiple broadcasting channels by using a modified form of pyramid broadcasting. The feature of this scheme is that it can be used together with forward error correction using block coding. Therefore, it can deliver high-quality content upon request with high network bandwidth efficiency even if data containers, such as Ethernet frames, are lost in the IP network. This is not possible with conventional schemes. Evaluation results show that its network bandwidth performance is still excellent even though it supports well-known FEC schemes using block coding.

Compressed video bitstreams are very sensitive to transmission errors. If we lose packets or receive them with errors during transmission, not only the current frame will be corrupted, but also errors will propagate to succeeding frames. Therefore, we need various mechanisms to protect data and reduce the effects of transmission errors. Error concealment is a data recovery technique that enables the decoder to conceal the effects of transmission errors by predicting the lost or corrupted video data from the previously reconstructed error free information. Motion vector recovery and motion compensation with the estimated motion vector is a good approach to conceal the corrupted macroblock data. In this paper, we show that it is reasonable to use the estimated motion vector to conceal the lost macroblock by providing macroblock distortion models. After we propose a new motion vector recovery algorithm based on optical flow fields, we compare its performance to those of conventional error concealment methods.

This paper proposes a wireless scheduling algorithm that can provide the Internet with delay proportional differentiated services in wireless networks. When considering wireless network environments that include burst and location-dependent channel errors, the proposed WDPS (Wireless Delay Proportional Service) scheduling algorithm can adaptively serve packets in class queues based on the delivered delay performance for each class. The significant characteristics of the WDPS scheduler include support for a fair relative delay service, the provision of graceful throughput and delay compensations, and the avoidance of class queue-blocking problems. Simulations show that the proposed algorithm can achieve the desirable properties for providing delay proportional services in wireless networks.

In this paper, a modified Gardner's timing-error estimation algorithm is proposed for space-time block coding (STBC) schemes. In STBC schemes, the symbol timing-error can be estimated for each received antenna. The proposed algorithm is the diversity combining of all symbol timing-error estimates using Gardner's algorithm with the assumptions of identical channel delay of each SISO sub-stream. Simulation results show the proposed algorithm improves the symbol timing-error estimation performance through diversity gains. Estimation of symbol timing-error in multiple-input and multiple-output (MIMO) antenna systems is an another suitable area of application.

A method of error concealment for JPEG2000 images is proposed in this paper. The proposed method uses the layer structure that is a feature of the JPEG2000. The most significant layer is hidden in the lowest layer of the JPEG2000 bit stream, and this embedded layer is used for error concealment. The most significant layer is duplicated because JPEG2000 uses bit-plane coding. In this coding, when the upper layers are affected by errors, the coefficients of the lower layers become meaningless. A bit stream encoded using the proposed method has the same data structure as a standard JPEG2000. Therefore, it can be decoded by a standard decoder. Our simulation results demonstrated the effectiveness of the proposed method.

In this paper, we describe an adaptive integration method for an audio-visual speech recognition system that uses not only the speaker's audio speech signal but visual speech signals like lip images. Human beings communicate with each other by integrating multiple types of sensory information such as hearing and vision. Such integration can be applied to automatic speech recognition, too. In the integration of audio and visual speech features for speech recognition, there are two important issues, i.e., (1) a model that represents the synchronous and asynchronous characteristics between audio and visual features, and makes the best use of a whole database that includes uni-modal, audio only, or visual only data as well as audio-visual data, and (2) the adaptive estimation of reliability weights for the audio and visual information. This paper mainly investigates two issues and proposes a novel method to effectively integrate audio and visual information in an audio-visual Automatic Speech Recognition (ASR) system. First, as the model that integrates audio-visual speech information, we apply a product of hidden Markov models (product HMM), the product of an audio HMM and a visual HMM. We newly propose a method that re-estimates the product HMM using audio-visual synchronous speech data so as to train the synchronicity of the audio-visual information, while the original product HMM assumes independence from audio-visual features. Second, for the optimal audio-visual information reliability weight estimation, we propose a Gaussian mixture model (GMM) based-MCE-GPD (minimum classification error and generalized probabilistic descent) algorithm, which enables reductions in the amount of adaptation data and amount of computations required for the GMM estimation. Evaluation experiments show that the proposed audio-visual speech recognition system improves the recognition accuracy over conventional ones even if the audio signals are clean.

A soft-decision decoding scheme of low-density parity-check codes (LDPC) is proposed for hard-detected signals of optical fiber communication (OFC) systems. Based on the error detection, the proposed scheme converts the received hard-decision into soft reliability for the input of the LDPC decoder, and soft-decision decoding is performed. Simulation results under OFC channels are shown and superior performance is obtained by using the proposed decoding scheme of the LDPC codes.

This paper reviews the historical development of adaptive antennas in Japan. First of all, we watch basic adaptive algorithms. In 1980s, particularly, the following issues were a matter of considerable concern to us; (a) behavior to the coherent interference like multipath waves or radar clutters, (b) signal degradation in case that the direction of arrival (DOA) of desired signal is different from the DOA specified beforehand in the adaptive antennas with the DOA of the desired signal as a prior knowledge, and (c) performance of adaptive antennas when the desired signal and interference are broadband. Although there are a lot of development and modification of adaptive algorithms in Japan, we refer in this paper only to the above-mentioned topics. Secondly, our attention is paid to implementation of adaptive antennas and advanced technologies. A large number of researches on the subjects have been carried out in Japan. Particularly, we focus on the initiative studies in Japan toward mobile communication application. They include researches of mobile radio propagation for adaptive antennas, calibration methods, and adaptive antenna for mobile terminals. As a matter of course, we also refer to adaptive antenna technologies for advanced communication schemes such as CDMA, SDMA, OFDM and so on. Finally, we take notice of some pilot products which were developed to verify the effect of the adaptive antenna in the practical environments. As the initiative ones, a couple of equipments are introduced in this paper.

We propose a method to realize soft-decision decoding for hard-detected signals. In this paper, a novel concept is introduced as "error-detected reliability. " The method is very useful for optical fiber communications (OFC) as hard detection is the only detection method for the OFC systems. We demonstrate our proposed method using the turbo code in which soft information is required for decoding. As a result, the simulation shows slight difference in the range of moderate to high signal-to-noise ratio between the proposed decoding scheme and the conventional turbo decoding scheme. Moreover, the bit error rate of 10-11 can be achieved by serial concatenation of a Reed-Solomon code and a turbo code for Q-factor lower than 8.0 dB with a bandwidth expansion ratio of 33.3%.