We design a DAB system using space-time coding for reliable transmission in the multipath fading channel. This letter assess the performance evaluation of space-time coded DAB system. For channel estimation in the space-time coded DAB system, we introduce two training sequences and derive the mean square error of each training sequence. We then represent the average symbol error rate of the space-time coded DAB system for the specific cases of two, three, four transmit antennas.

There have been numerous studies on the enhancement of the noisy speech signal. In this paper, We propose a new speech enhancement method, that is, a DFF (Dissonant Frequency Filtering) scheme combined with NR (noise reduction) algorithm. The simulation results indicate that the proposed method provides a significant gain in perceptual quality compared with the conventional method. Therefore if the proposed enhancement scheme is used as a pre-filter, the output speech quality would be enhanced perceptually.

This paper proposes a method to detect buildings and houses whose walls are not parallel to Synthetic Aperture Radar (SAR) flight path. Experimental observations show that it is difficult to detect these targets because of small backscattering characteristics. The detection method is based on the correlation coefficient in the circular polarization basis, taking full advantage of Polarimetric SAR (POLSAR) data. Since the correlation coefficient is real-valued for natural distributed targets with reflection symmetry and for non-natural targets orthogonal to illumination direction, and it becomes a complex number for non-natural targets aligned not orthogonal to radar Line-Of-Sight (LOS), the value seems to be an effective index for detection of obliquely aligned non-natural targets. The detection results are shown using the X-band Polarimetric and Interferometric SAR (Pi-SAR) single-path data set in conjunction with other polarimetric indices.

Recently, a cluster map based blind RBF equalizer (CM-BRE) has been proposed. By utilizing the underlying structure characteristics of RBF equalizer, the CM-BRE can be implemented by the combination of neural-gas algorithm (NGA) with several sorting operations. Although the CM-BRE is able to achieve almost identical performance with the optimal RBF equalizer, the high computational load mainly caused by NGA limits it's application. In this paper, we propose a downsizing method that employs the inter-relation among RBF centers and significantly reduces the NGA's computational load. Furthermore, a method to determine the feedback vector is derived, then CM-BRE is extended to a cluster map based blind RBF decision feedback equalizer (CM-BRDFE). The proposed CM-BRDFE also shows the close performance with the optimal RBF decision feedback equalizer in simulations.

PID control schemes have been widely used for many industrial processes, which can be represented by nonlinear systems. In this paper a new scheme for neural-net based PID controllers is presented. The connection weights and some parameters of the sigmoidal functions of the neural network are adjusted using a real-coded genetic algorithm. The effectiveness of the newly proposed control scheme for nonlinear systems is numerically evaluated using a simulation example.

In this study, a fourth-order cumulants based iterative algorithm for blind channel equalization is introduced, which is robust with respect to the existence of heavy Gaussian noise in a channel and does not require the minimum phase characteristic of the channel. The transmitted signals at the receiver are over-sampled to ensure the channel described by a full-column rank matrix. It changes a single-input/single-output (SISO) finite-impulse response (FIR) channel to a single-input/multi-output (SIMO) channel. Based on the properties of the fourth-order cumulants of the over-sampled channel inputs, the iterative algorithm is derived to estimate the deconvolution matrix which makes the overall transfer matrix transparent, i.e., it can be reduced to the identity matrix by simple reordering and scaling. In simulation studies, both a closed-form and a stochastic version of the proposed algorithm are tested with three-ray multi-path channels, and their performances are compared with the methods based on conventional second-order statistics and higher-order statistics (HOS) as well. Relatively good results with fast convergence speed are achieved, even when the transmitted symbols are significantly corrupted with Gaussian noise.

We have integrated a phase change random access memory (PRAM), completely based on 0.24 µm-CMOS technologies using nitrogen doped GeSbTe films. The Ge2Sb2Te5 (GST) thin films are well known to play a critical role in writing current of PRAM. Through device simulation, we found that high-resistive GST is indispensable to minimize the writing current of PRAM. For the first time, we found the resistivity of GST film can be controlled with nitrogen doping. Doping nitrogen to GST film successfully reduced writing current. A 0.24 µm PRAM using N-doped GST films were demonstrated with writing pulse of 0.8 mA-50 ns for RESET and 0.4 mA-100 ns for SET. Also, the cell endurance has been enhanced with grain growth suppression effect of dopant nitrogen. Endurance performance of fully integrated PRAM using N-doped GST shows no fail bit up to 2E9 cycles. Allowing 1% failures, extrapolation to 85 indicates retention time of 2 years. All the results show that PRAM is one of the most promising candidates in the market for the next generation memories.

To improve the DS-CDMA signal transmission performance in a frequency-selective fading channel, the frequency-domain equalization (FDE) can be applied, in which simple one-tap equalization is carried out on each subcarrier component obtained by fast Fourier transform (FFT). Equalization weights for joint FDE and antenna diversity combining based on maximal ratio combining (MRC), zero-forcing (ZF), and minimum mean square error (MMSE) are derived. The conditional bit error rate (BER) is derived for the given set of channel gains in a frequency-selective multipath fading channel. The theoretical average BER performance is evaluated by Monte-Carlo numerical computation method using the derived conditional BER and is confirmed by computer simulation. Performance comparison between DS- and multi-carrier (MC)-CDMA both using FDE is also presented.

This paper presents a novel decoding strategy called combined iterative demapping/decoding (CIDD), for coded M-ary biorthogonal keying-based direct sequence ultra-wideband (MBOK DS-UWB) systems. A coded MBOK DS-UWB system consists of a convolutional encoder, an interleaver, and an MBOK DS-UWB pulse mapper. CIDD improves the error rate performance of MBOK DS-UWB systems by applying the turbo principle to the demapping and decoding processes at the receiver side. To develop the CIDD, a soft-in/soft-out MBOK demapping algorithm, based on the max-log-MAP algorithm, was derived. Simulation results showed that using CIDD siginificantly improved the error rate performance of both static and multipath fading channels. It was also shown that the computational complexity of CIDD is comparable to that of the Viterbi decoding used in [133,171]8 conventional convolutional coding.

In this paper, we propose a transmitter structure in digital QAM systems where pre-compensator compensates for nonlinearity with "memory effects" at the output amplifier. The nonlinearity is modeled as a linear time-invariant filter cascaded by memoryless nonlinearity (Wiener model), whereas the pre-compensator comprises an FIR-type adaptive filter that follows a memoryless predistorter based on a series expansion with orthogonal polynomials for digital QAM data. The predistorter and the adaptive filter of the pre-compensator are stochastically and directly adapted using the error signal. The theoretically optimum parameters of the predistorter are approximately solved whence the steady-state mean square compensation error is calculated. Simulations show that the proposed pre-compensator can be adapted to achieve a sufficiently small compensation error, restoring the original QAM constellation through linearization and equalization of the nonlinearity with memory effects.

Sensor networks, in which a large number of sensor nodes are connected with each other through communication networks, are potential to provide extensive new applications with various research and technical challenges and attracting much attention all over the world. In this paper we describe information and signal processing for sensor networks with emphasis on the concepts of collaboration and fusion as one of the most important issues for the sensor networks. We also review some basic aspects of sensor networks in terms of their features and the network architecture.

The block-based fast transmission scheme, which is one of typical stored video delivery schemes, is reasonable in terms of its bandwidth efficiency and tolerance to the delay jitter, etc. However, it causes packet loss because of its burst data transmission method. Thus, we propose a slotted multicast scheme for MPEG video based on the block transmission scheme to maintain a higher quality and to include time constraints. We define two delivery units, the "GoPs Group" and the "Frame Type," on the basis of the MPEG characteristics with periodical NACK feedback from the clients. The former is tolerant to burst packet loss, and the latter gives priority to important frames. Our block multicast has two phases: a "Transmission Phase" and a "Retransmission Phase." In the former, a server multicasts a block, and in the latter, a server retransmits lost packets using multicast according to the proper delivery unit. We evaluate our proposal from some viewpoints with a computer simulation. We also measure the quality of the video reflected the result of a computer simulation. From these results, we confirm performance effectiveness of our proposal.

We show that the necessary and sufficient condition for the existence of a balanced bowtie decomposition of the symmetric complete multi-digraph is n 5 and λ(n-1) 0 (mod 6). Decomposition algorithms are also given.

This paper presents a voltage-mode WTA/MAX circuit that achieves high-speed and multi-chip features. Based on the efficient averaged-value comparison approach, the time and hardware complexities are proportional to O(log N) and O(N) respectively, where N is the number of inputs. In addition, a voltage comparison element (VCE) circuit is proposed to achieve multi-chip function. In the proposed circuit, the averaged-value calculator is built using resistor array that prevents the matching problem of transistor array. The whole circuit was fabricated with the TSMC 0.35 µm signal-poly quadruple-metal CMOS process. With eight input signals, the measurement results show that the proposed circuit resolved input voltages differing by 10 mV in 30 ns, and the multi-chip capability was also verified.

Computer systems are constantly under attack and illegal access is a constant threat which makes security even more critical. A system can be broken into and secret information, e.g. decryption key, may be exposed, resulting in a total break of the system. Recently, a new framework for the protection against such key exposure problem was suggested and was called, Key-Insulated Encryption (KIE). In our paper, we introduce a novel approach to key insulated cryptosystems that offers provable security without computational assumptions. For the model of Information-Theoretically Secure Key-Insulated Encryption (ISKIE), we show lower bounds on required memory sizes of user, trusted device and sender. Our bounds are all tight as our concrete construction of ISKIE achieves all the bounds. We also extend this concept further by adding an extra property so that any pair of users in the system is able to communicate with each other and still have the same security benefits as the existing KIE based on intractability assumptions. We called this, Dynamic and Mutual Key-Insulated Encryption (DMKIE), and concrete implementations of DMKIE will be shown as well. In the end, we discuss the relationship of DMKIE against Key Predistribution Schemes (KPS) and Broadcast Encryption Schemes (BES), that is, we show that DMKIE can be constructed from either KPS or BES.

Optimistic coding is a coding in which we require the existence of reliable codes for infinitely many block length. In this letter we consider the optimistic source coding theorems for a general source Z from the information-spectrum approach. We first formulate the problem to be considered clearly. We obtain the optimistic infimum achievable source coding rate Tε (Z) for the case where decoding error probability εn is asymptotically less than or equal to an arbitrarily given ε [0,1). In fact, Tε (Z) turns out to be expressed in a form similar to the ordinary infimum achievable source coding rate. A new expression for Tε (Z) is also given. In addition, we investigate the case where εn = 0 for infinitely many n and obtain the infimum achievable coding rate.

Efficient general secure multiparty computation (MPC) protocols were previously proposed, and the combination with the efficient auction circuits achieves the efficient sealed-bid auctions with the full privacy and correctness. However, the combination requires that each bidder submits ciphertexts of bits representing his bid, and their zero-knowledge proofs. This cost amounts to about 80 multi-exponentiations in usual case that the bid size is 20 bits (i.e. about 1,000,000 bid prices). This paper proposes sealed-bid auction protocols based on the efficient MPC protocols, where a bidder can submit only a single ciphertext. The bidder's cost is a few multi-exponentiations, and thus the proposed protocols are suitable for mobile bidders. A novel technique for the realization is a bit-slicing conversion by multiple servers, where a single ciphertext for a bid is securely converted into ciphertexts of bits representing the bid.

In this paper, the CSK/SSMA ALOHA system with nonorthogonal sequences which combines the ALOHA system with Code Shift Keying (CSK) using nonorthogonal sequences is proposed. The throughput performance was evaluated by theoretical analysis. Moreover, the throughput performance of the system is compared with those of the DS/SSMA ALOHA and M-ary/SSMA ALOHA systems. It is found that the throughput performance of our system to be better than those of the other two systems.

In many cryptosystems incorporating human beings, the users' limited memories and their indifference to keeping the systems secure may cause some severe vulnerability of the whole systems. Thus we need more studies on personal entropy, from an information theoretical point of view, to capture the characteristics of human beings as special information sources for cryptosystems. In this paper, we discuss and analyze the use of personal entropy for generating cryptographic keys. In such a case, it is crucially important to precisely evaluate the amount of personal entropy that indicates the actual key length. We propose an advanced key generation scheme based on the conventional graphical passwords proposed in [12]. We improve them to make the most of the secret information extracted in one drawing, i.e., we incorporate the on-line pen pressure and pen inclination information in addition to utilize more secret information. We call the scheme dynamic graphical passwords, and propose a practical construction of them. We also show a precise way of quantifying their entropy, and finally, as an experimental result, we can generate a key of over 110-bit long, using the data of a single drawing. When quantifying their entropy, we need to precisely evaluate the entropy of graphical passwords as well as that of the on-line information of pen movements. We need to precisely evaluate the entropy of graphical passwords by considering the users' biased choices of their graphical passwords. It is expected that they tend to choose their passwords that are memorable as easily as possible, thus we quantify the burden of memorizing each graphical password by the length of its description using a special language based on [12]. We improve the approach in [12] by more directly reflecting how easily each graphical password can be memorized.

The hybrid fiber coax (HFC) technology enables the conventional cable-television (CATV) network to provide subscribers with Internet access services. In this paper, we propose a new preemptive priority scheme (PPS) for IEEE 802.14 hybrid fiber coax (HFC) networks with the intelligent nodes (INs). The INs are placed between the headend controller and stations. By using INs, that stand for downstream subscribers to contend for the demand resources, the collision probability, and the collision resolving period can be reduced. In this paper, we further extend such network architecture to support multi-priority access. In each IN or individual station, the proposed PPS will prevent a higher priority request from colliding with requests of lower priority. Moreover, in PPS, the granted bandwidth for lower priority requests can be preempted by the waiting request with higher priority. This will speedup the channel capture by priority data. The efficiency of PPS is investigated by simulations. Simulation results show that by adopting INs with PPS to be an agent for subscribers can not only shorten the collision resolving period but also minimize the average request delay of priority data.