Sliding mode control (SMC) is known to be robust with respect to matched uncertainties. However, it does not guarantee stability of systems with mismatched uncertainties. In this paper, we propose a new method to design a sliding surface for linear systems with mismatched uncertainties. The proposed sliding surface provides a new stability criterion of the reduced-order system origin with respect to mismatched uncertainties. A numerical example is given to illustrate the effectiveness of the proposed method.

This paper reports the strength of a pseudorandom number generator MUGI, which was published as a stream cipher by Hitachi, Ltd. in 2001, against linear cryptanalysis. MUGI is one of the recommended ciphers of CRYPTREC, which is a project for the e-Government in Japan. It has two internal states called state and buffer, which are updated by a linear function λ and a non-linear function ρ. The non-linear function ρ and the linear function λ have already been analyzed, independently. In this paper, whole MUGI is analyzed by truncated linear cryptanalysis. The analysis of λ function is based on the state variables method. The result is combined to the result of the analysis of ρ function to make a trellis diagram. Viterbi search is conducted on the diagram to find the best possible linear path under 64-bit truncated linear cryptanalysis. As the result, the upper bound of the maximum linear characteristic probability is estimated as less than 2-138. Therefore, MUGI is secure against linear cryptanalysis.

In this study, we propose an object-based multimedia model for specifying the QoS (quality of service) requirements, such as the maximum data-dropping rate or the maximum data-delay rate. We also present a resource allocation model, called the net-profit model, in which the satisfaction of user's QoS requirements is measured by the benefit earned by the system. Based on the net-profit model, the system is rewarded if it can allocate enough resources to a multimedia delivery request and fulfill the QoS requirements specified by the user. At the same time, the system is penalized if it cannot allocate enough resources to a multimedia delivery request. We first investigate the problem of how to allocate resources efficiently, so that the QoS satisfaction is maximized. However, the net-profit may be distributed unevenly among the multimedia delivery requests. Thus, the second problem discusses how to allocate the resource efficiently so that the net-profit difference is minimized between any two multimedia requests. A dynamic programming based algorithm is proposed to find such an optimal solution with the minimum net-profit differences.

In this paper, we propose an efficient protocol for proving the correctness of shuffling and an efficient protocol for simultaneously proving the correctness of both shuffling and decryption. The former protocol is the most efficient in computational and communication complexity among 3-move honest verifier perfect zero-knowledge protocols for proving a shuffling of ElGamal cipher-texts. The latter protocol is the most efficient in computational, communication, and round complexity, as a whole, in proving the correctness of both shuffling and decryption of ElGamal cipher-texts. The proposed protocols will be a building block of an efficient, universally verifiable mix-net, whose application to voting systems is prominent.

When the multipath delay difference exceeds the guard interval (GI), the performance of MIMO-OFDM transmission suffers severely from both the inter-symbol interference (ISI) from the adjacent OFDM symbols and the inter-carrier interference (ICI) within the same symbol. This paper therefore proposes a MIMO-OFDM receiver employing the low-complexity turbo equalization. The proposed receiver initially separates the data streams and suppresses ICI by linear processing. In the iterative processing, it cancels the other data streams as well as ISI and ICI. The MIMO-OFDM turbo equalizer consists of an ISI canceller, an ICI canceller, an optimal detection filter, and a MAP detector. The proposed receiver can improve the transmission performance by exploiting the log-likelihood ratio that the decoding process produces for canceling both ISI and ICI and separating of the spatially multiplexed streams. Computer simulations, which apply the wireless LAN to MIMO, demonstrate that the proposed receiver can provide excellent performance in the severe multipath channels where the delay difference is greater than GI.

To investigate cyber-criminals, Police sometimes asks Administrator of a computer system to disclose the whole transaction log. Administrator, however, wants to protect the privacy of innocent users. This paper presents a solution for the disclosure/privacy problem of transaction log. In this scheme, Police can search over the encrypted records of the transaction log by keywords. The administrator discloses only the records which include the keyword, but nothing more. Police can verify that the administrator faithfully disclosed all the records which include the keyword.

The traffic congestion problem in urban areas is worsening since traditional traffic signal control systems cannot provide] efficient traffic regulation. Therefore, dynamic traffic signal control in Intelligent Transportation System (ITS) recently has received increasing attention. This study devised a multi-agent architecture, the Adaptive and Cooperative Traffic light Agent Model (ACTAM), for a decentralized traffic signal control system. The proposed architecture comprises a data storage and communication layer, a traffic regulation factor processing layer, and a decision-making layer. This study focused on utilizing the cooperation of multi-agents and the prediction mechanism of our architecture, the Forecast Module, to forecast future traffic volume in each individual intersection. The Forecast Module is designed to forecast traffic volume in an intersection via multi-agent cooperation by exchanging traffic volume information for adjacent intersections, since vehicles passing through nearby intersections were believed to significantly influence the traffic volume of specific intersections. The proposed architecture can achieve dynamic traffic signal control. Thus, total delay time of the traffic network under ACTAM can be reduced by 37% compared to the conventional fixed sequence traffic signal control strategy. Consequently, traffic congestion in urban areas can be alleviated by adopting ACTAM.

This letter proposes an efficient and simple stopping criterion for turbo decoding, which is derived by observing the behavior of log-likelihood ratio (LLR) values. Based on the behavior, the proposed criterion counts the number of absolute LLR values less than a threshold and the number of hard decision 1's in order to complete the iterative decoding procedure. Simulation results show that the proposed approach achieves a reduced number of iterations while maintaining similar BER/FER performance to the previous criteria.

This paper deals with broadcast encryption schemes, in which a sender can send information securely to a group of receivers excluding some receivers over a broadcast channel. In this paper we propose modifications of the Complete Subtree (CS), the Subset Difference (SD) and the Layered Subset Difference (LSD) methods based on the Master Key Tree (MKT). Our modifications eliminate log N keys or labels from receivers' storage, in exchange for an increase in the computational overhead, where N is the total number of receivers. We also propose modifications of the SD and LSD methods by applying the Trapdoor One-way Permutation Tree (TOPT) which is originally proposed in order to modify the CS method. Our modifications based on TOPT also eliminate log N labels, and the computational cost is much smaller than MKT based methods.

For fixed initial and destination states (i.e., markings), M0 and Md, there exist generally infinite firing count vectors in a Petri net. In this letter, it is shown that all fundamental particular solutions as well as all minimal T-invariants w.r.t. firing count vectors are needed to express an arbitrary firing count vector for the fixed M0 and Md. An algorithm for finding a special firing count vector which is expressed by using the only one specified fundamental particular solution is also given.

In this paper, we propose a multiuser detection (MUD) scheme for space-time block coded orthogonal frequency division multiplexing (STBC-OFDM) systems. We derive the optimum weight matrix used to decouple simultaneously signals from active multiple access users using the minimum mean square error (MMSE) multiuser detection method. The proposed scheme provides good performance over different models of the frequency selective fading channel. It is also to show that if the length of the cyclic prefix is larger than that of the channel, the performance of the detector depends on only the total energy extracted from multipath components but not the employed channel model, the number of multipath components or the delay of each multipath component.

In this Letter, a dumbbell-shaped patch loaded slotline(PLS) is proposed. Like the conventional defected ground structure(DGS) for a microstrip line, we show that the proposed PLS can provide a wide bandstop characteristic in some frequency bands with only one or small number of unit cells. Also, the equivalent circuit model for a unit section is derived from the analysis of the field distributions in the structure and its circuit parameters are determined by means of full wave numerical simulations. This equivalent circuit is shown to be dual to that of the typical DGS in a microstrip line. A broadband microstrip to slotline transition is incorporated in the PLS in order to measure the characteristics of the structure. The experimental results agree well with the simulations and show the validity of the modeling for the proposed PLS.

A low-complexity step-by-step decoding algorithm for t-error-correcting binary Bose-Chaudhuri-Hocquenghem (BCH) codes is proposed. Using logical analysis, we obtained a simple rule which can directly determine whether a bit in the received word is correct. The computational complexity of this decoder is less than the conventional step-by-step decoding algorithm, since it reduces at least half of the matrix computations and the most complex element in the conventional step-by-step decoder is the "matrix-computing" element.

A new bipolar linear transconductor for low-voltage low-power signal processing is proposed. The proposed circuit has larger input linear range and smaller power dissipation when compared with the conventional bipolar linear transconductor. The experimental results show that the transconductor with a transconductance of 50 µS has a linearity error of less than 0.02% over an input voltage range of 2.1 V at supply voltages of 3 V. The power dissipation of the transconductor is 3.15 mW.

In this paper, we present a noble pattern synthesis method of linear and planar array antennas, with non-uniform spacing, for simultaneous reduction of their side-lobe level and pattern distortion during beam steering. In the case of linear array, the Gauss-Newton method is applied to adjust the positions of elements, providing an optimal linear array in the sense of side-lobe level and pattern distortion. In the case of planar array, the concept of thinned array combined with non-uniformly spaced array is applied to obtain an optimal two dimensional (2-D) planar array structure under some constraints. The optimized non-uniformly spaced linear array is extended to the 2-D planar array structure, and it is used as an initial planar array geometry. Next, we further modify the initial 2-D planar array geometry with the aid of thinned array theory in order to reduce the maximum side-lobe level. This is implemented by a genetic algorithm under some constraints, minimizing the maximum side-lobe level of the 2-D planar array. It is shown that the proposed method can significantly reduce the pattern distortion as well as the side-lobe level, although the beam direction is scanned.

We discuss a typical profile of the k-error linear complexity for balanced binary exponent periodic sequences and the number of periodic distinct sequences by their profiles. A numerical example with period 16 is also shown.

In orthogonal frequency division multiplexing (OFDM) systems with differential phase shift keying (DPSK), it is possible to apply differential modulation either in the time or frequency domain depending on the condition of fading channels, such as the Doppler frequency shift and the delay spread. This paper proposes a simple calculation method, that is, an approximate closed-form equation of the bit error rate (BER) in DPSK/OFDM systems mentioned above over both time and frequency selective Rician fading channels. The validity of the proposed method is demonstrated by the fact that the BER performances given by the derived equation coincide with those by Monte Carlo simulation.

Cowen gave a universal compact routing algorithm with a stretch factor of three and table-size of O(n2/3log4/3n) based on a simple and practical model. (The table-size is later improved to O(n1/2log3/2n).) This paper considers, using the same model, how the necessary table-size differs if the stretch factor must be less than three. It is shown that: (i) There is a routing algorithm with a stretch factor of two whose table-size is (n -+ 2)log n. (ii) There is a network for which any routing algorithm that follows the model and with a stretch factor of less than three needs a table-size of (n - 2)log n in at least one node. Thus, we can only reduce roughly an additive log n (i.e., table-entries) from the trivial table-size of n log n which obviously enables shortest-path routing. Furthermore it turns out that we can reduce only an additive log n (i.e., only one table-entry) from the trivial n log n if we have to achieve a stretch factor of less than two. Thus the algorithm (i) is (roughly) tight both in its stretch factor and in its table-size.

This paper presents an efficient scaling-simulation algorithm that simulates operations of the reconfigurable mesh (RM) of size n n using the mesh with multiple partitioned buses (MMPB) of size m m (m < n). The RM and the MMPB are the two-dimensional mesh-connected computers equipped with broadcasting buses. The broadcasting buses of the RM can be used to dynamically obtain various interconnection patterns among the processors during the execution of programs, while those of the MMPB are placed only to every row and column and are statically partitioned in advance by a fixed length. We show that the RM of size n n can be simulated in steps by the MMPB of size m m (m < n), where L is the number of broadcasting buses in each row/column of the simulating MMPB. Although the time-complexity of our algorithm is less efficient than that of the fastest RM scaling-simulation algorithm, the simulating model of our algorithm is the MMPB model where the bus-reconfiguration is not allowed.

Inoue et al. introduced an automaton on a two-dimensional tape, which decides acceptance or rejection of an input tape by scanning the tape from various sides by various automata which move one way, and investigated the accepting power of such an automaton. This paper continues the investigation of this type of automata, especially, -type automata (obtained by combining four three-way two-dimensional deterministic finite automata (tr2-dfa's) in "or" fashion) and -type automata (obtained by combining four tr2-dfa's in "and" fashion). We first investigate a relationship between the accepting powers of -type automata and -type automata, and show that they are incomparable. Then, we investigate a hierarchy of the accepting powers based on the number of tr2-dfa's combined. Finally, we briefly describe a relationship between the accepting powers of automata obtained by combining three-way two-dimensional deterministic and nondeterministic finite automata.