This paper aims at challenging Bernstein's problem called the "Degrees-of-Freedom problem," which remains unsolved from both the physiological and robotics viewpoints. More than a half century ago A.N. Bernstein observed that "dexterity" residing in human limb motion emerges from accumulated involvement of multi-joint movements in surplus DOF. It is also said in robotics that redundancy of DOFs in robot mechanisms may contribute to enhancement of dexterity and versatility. However, kinematic redundancy incurs a problem of ill-posedness of inverse kinematics from task-description space to joint space. In the history of robotics research such ill-posedness problem of inverse-kinematics has not yet been attacked directly but circumvented by introducing an artificial performance index and determining uniquely an inverse kinematics solution by minimizing it. Instead of it, this paper introduces two novel concepts named "stability on a manifold" and "transferability to a submanifold" in treating the case of human multi-joint movements of reaching and shows that a sensory feedback from task space to joint space together with a set of adequate dampings enables any solution to the overall closed-loop dynamics to converge naturally and coordinately to a lower-dimensional manifold describing a set of joint states fulfilling a given motion task. This means that, without considering any type of inverse kinematics, the reaching task can be accomplished by a sensory feedback with adequate choice of a stiffness parameter and damping coefficients. It is also shown that these novel concepts can cope with annoying characteristics called "variability" of redundant joint motions seen typically in human skilled reaching. Finally, it is pointed out that the proposed control signals can be generated in a feedforward manner in case of human limb movements by referring to mechano-chemical characteristics of activation of muscles. Based on this observation, generation of human skilled movements of reaching can be interpreted in terms of the proposed "Virtual-Spring" hypothesis instead of the traditional "Equilibrium-Point" hypothesis.

We study asynchronous SSMA communication systems using binary spreading sequences of Markov chains and prove the CLT (central limit theorem) for the empirical distribution of the normalized MAI (multiple-access interference). We also prove that the distribution of the normalized MAI for asynchronous systems can never be Gaussian if chains are irreducible and aperiodic. Based on these results, we propose novel theoretical evaluations of bit error probabilities in such systems based on the CLT and compare these and conventional theoretical estimations based on the SGA (standard Gaussian approximation) with experimental results. Consequently we confirm that the proposed theoretical evaluations based on the CLT agree with the experimental results better than the theoretical evaluations based on the SGA. Accordingly, using the theoretical evaluations based on the CLT, we give the optimum spreading sequences of Markov chains in terms of bit error probabilities.

Robust path following is an issue with practical importance to the ship industry. This paper studies the robust tracking problem for an underactuated navigator. The global robust controller is proposed to force the navigator to follow any smooth time-varying trajectory, despite the existence of the environmental disturbances. It is verified that the tracking errors are ultimately confined to an arbitrarily small ball of the origin.

Deflection routing is one of the promising approaches to resolve contention in the optical burst switching networks. In the conventional deflection routing scheme, optical bursts may be unable to traverse the route evaluated to select an outgoing link because of the contention at succeeding downstream transit nodes. As a result, the optical bursts may traverse a different route resulting in a long distance or decreased performance. This paper proposes a deflection routing scheme that considers the possibility of the contention at downstream nodes. This scheme utilizes the "expected route distance" instead of the static route distance toward a destination node. The expected route distance considers the possibility of contention at each downstream transit node and is calculated using measured link blocking probabilities at each downstream transit node. The selection priority of each outgoing link is given dynamically based on its expected route distance toward a destination node. By considering the possibility of contention at downstream nodes, a routing scheme with high performance can be realized. The loss rate of optical bursts is improved when an imbalanced load is applied to the network, and the loss rate of optical bursts is also improved when the network includes links with extremely different distances.

Wireless networks have been rapidly integrated with the wired Internet and considered as the most popular MAC technology for Ad Hoc mobile communications. In WLAN technologies, IEEE 802.11b WLAN is the most widespread wireless network today. The IEEE 802.11b WLAN supports multiple transmission rates and the rate is chosen in an adaptive manner by an auto rate control algorithm. This auto rate control algorithm deeply affects the total system performance of the IEEE 802.11b WLAN. In this paper, we examine the WLAN performance with regard to the auto rate control algorithm, especially the ARF scheme, which is the most popular auto rate control algorithm in 802.11b based WLAN products. The experimental results indicate that the ARF scheme works well in the face of signal noise due to node location. However, the ARF scheme severely degrades system performance when multiple nodes contend to obtain the wireless channel and the packet is lost due to signal collision.

We present a design of knowledge circulation framework for quality of service (QoS) control of multimedia communication service (MCS). This framework aims to realizing user oriented and resource aware MCS by enabling effective placement of QoS control knowledge on the network. In this paper, we propose a conceptual design of the framework with knowledge-based multiagent system. In this framework, QoS control knowledge is actively circulated by getting on the agents. We implement a prototype of real-time bidirectional MCS (videoconference system) using this framework, and show initial experiment results using it to evaluate the effectiveness of the framework.

Non-supersingular elliptic curves are important for the security of pairing-based cryptosystems. But there are few suitable non-supersingular elliptic curves for pairing-based cryptosystems. This letter introduces a method which allows the existing method to generate more non-supersingular elliptic curves suitable for pairing-based cryptosystems when the embedding degree is 6.

We have presented a new analytical method for the stub-loaded ridge waveguide that is a candidate of leaky-wave antennas in the millimeter-wave region. This guide has many singular conductor edges, so that its accurate analysis is very difficult. The present method overcomes such difficulty by introducing the singular fields at the edges into the field expressions beforehand. Then we have investigated the dispersion characteristics for various structural parameters, to find a structure suitable to antenna applications. Finally, we have verified their behavioral feature experimentally.

The explicit construction of a universal source code for correlated sources is presented. The construction is based on a technique of simulated random coding algorithms [5]. The proposed algorithm simulates the random generation of linear codes. For every pair of correlated sources whose achievable rate region includes a given pair of encoding rates, the decoding error rate of the proposed algorithm goes to zero almost surely as the block length goes to infinity.

In this letter, we propose a novel approach for use in the analytical modeling of the overall performance of a Hybrid ARQ (type I and II) together with arbitrary channel model, based on Hidden Markov Model (HMM). Using the combined HMM model developed for involved ARQ protocols with the finite state channel model, such critical performance measure as throughput and delay can be derived in closed form. Analytical results are derived for Stop-and-Wait as well as Go-back-N type together with the type I and type II Hybrid ARQ scheme adopted. We compare the analytical results along with the simulation results in order to check the correctness our model, and show the efficiency of our approach by applying it to realistic environments such as the CDMA IS-95 system with its derived equations.

Using several high rate recursive convolutional codes as the basic element and the trace criteria as the designing principle, a new kind of recursive space-time trellis code with more flexible and higher data rate is presented for the serially concatenated space-time code. When 2b-ary modulation and N transmit antennas are used, the data rate of the new code can be arranged from b bps/Hz to Nb-1bps/Hz by modifying the number of recursive convolutional codes and the data rate of each code.

Fast and simple algorithm of a parity checker for a large residue numbers is presented. A new set of RNS moduli with 2r-(2l1) form for fast modular multiplication is proposed. The proposed RNS moduli has a large dynamic range for a large RNS number. The parity of a residue number can be checked by the Chinese remainder theorem (CRT). A CRT-based parity checker is simply organized by the Montgomery reduction method (MRM), implemented by using multipliers and the carry-save adder array. We present a fast parity checker with minimal hardware processed in three clock cycles for 32-bit RNS modulus set.

The resource allocation problem in multi-agent systems is one of the crucial problems hindering the development of multi-agent technologies. This study demonstrates that "time delay" functions as an effective factor in a resource allocation, contrasting to the conventional real-time oriented multi-agent paradigm by 1) introducing a "fickle" agent, whose own strategy fluctuates randomly, and 2) an agent repository mechanism. This study also demonstrates that in the resource allocation process, time delay induces dramatic changes in performance, the specific phenomenon is the so-called "phase transition phenomenon". This finding means emergence of the phase transition is cited as a major factor governing multi-agent system performance. This knowledge is of essential importance in the regulation in multi-agent performance.

In this paper, a refined analytic model is presented for the IEEE 802.11 distributed coordination function (DCF) in a time-varying channel environment. In the proposed model, the channel is modelled using a finite-state Markov (FSM) chain. The saturation throughput and average packet delay are analyzed from the proposed model. It is shown using OPNETTM and UltraSANTM simulations that the proposed model accurately predicts the performance of the IEEE 802.11 DCF.

This letter proposes two very-low-complexity maximum-likelihood (ML) detection algorithms based on QR decomposition for the quasi-orthogonal space-time code (QSTBC) with four transmit antennas [3]-[5], called VLCMLDec1 and VLCMLDec2 decoders. The first decoder, VLCMLDec1, can be used to detect transmitted symbols being extracted from finite-size constellations such as phase-shift keying (PSK) or quadrature amplitude modulation (QAM). The second decoder, VLCMLDec2, is an enhanced version of the VLCMLDec1, developed mainly for QAM constellations. Simulation results show that both of the proposed decoders enable the QSTBC to achieve ML performance with significant reduction in computational load.

This paper proposes the application of tree-structured clustering to the processing of noisy speech collected under various SNR conditions in the framework of piecewise-linear transformation (PLT)-based HMM adaptation for noisy speech. Three kinds of clustering methods are described: a one-step clustering method that integrates noise and SNR conditions and two two-step clustering methods that construct trees for each SNR condition. According to the clustering results, a noisy speech HMM is made for each node of the tree structure. Based on the likelihood maximization criterion, the HMM that best matches the input speech is selected by tracing the tree from top to bottom, and the selected HMM is further adapted by linear transformation. The proposed methods are evaluated by applying them to a Japanese dialogue recognition system. The results confirm that the proposed methods are effective in recognizing digitally noise-added speech and actual noisy speech issued by a wide range of speakers under various noise conditions. The results also indicate that the one-step clustering method gives better performance than the two-step clustering methods.

Overlay multicast schemes for Mobile Ad hoc Networks (MANET) [1] have been proposed to remove non group members' dependency for multicast forwarding. However, since all packets are relayed from one group member to other group member in a form of unicast packet, they sometimes cause a lot of packets' collision and low resource utilization particularly where group members densely locate. In this paper, we propose a new forwarding scheme, DESIRE (Density awarE heterogeneouS overlay multIcast foRwarding schemE in MANET), for overlay multicast in MANET. DESIRE is significantly different from previous overlay multicast schemes in that it creates separate data forwarding path over overlay DDT (Data Delivery Tree) depending on density of group members. In dense environment, a zone is constructed and a scoped flooding is applied within it. On the other hand, in sparse environment, data dissemination is accomplished in a form of unicast packet similar to previous overlay multicast. By adapting scoped flooding in dense environment, it can reduce a lot of packets' collision and balance battery consumption by making use of mobile node's broadcast capability entirely. Also, in sparse environment, DESIRE can cope with network mobility very well since overlay DDT can remain static regardless of changes in physical topology. Such distinct advantages are evaluated by simulation. Generally, better performance is shown with large group members than small group members.

Flooding is usually utilized to find a multi-hop route toward a node which is not within transmission range. However, existing flooding schemes deteriorate the performance of network because of periodic message exchanges, frequent occurrence of collisions, and redundant packet transmission. To resolve the problem, a lightweight and novel flooding scheme is proposed in this paper. The scheme employs ongoing packets for constructing a cluster architecture as the existing on-demand clustering scheme. Unlike to the existing schemes, it makes use of unicast packet transmission to reduce the number of collisions and to find the flooding candidates easily. As a result, the proposed scheme yields fewer flooding nodes than other schemes. Simulation results prove that it causes fewer packet transmissions and fewer collisions than those of two other schemes.

We propose a novel routing algorithm for reverse proxy servers, called load balancing content address hashing (LB-CAH), and evaluate the performance of the proposed routing algorithm compared with that of the content address hashing (CAH) and the hash and slide (HAS) routing algorithms. The proposed LB-CAH routing algorithm calculates the popularity of pages in the load balancer using an LFU caching technique and periodically makes a popularity list. Using this popularity list, the proposed routing algorithm selects a reverse proxy server as follows. When the requested page appears in the popularity list, the request is routed according to the round robin method; otherwise, it is routed according to the content address hashing method. We evaluate and compare the LB-CAH, CAH and HAS routing algorithms by simulation experiments from the viewpoints of load balancing, consumed cache space and cache hit rate. Simulation experiments show that the proposed LB-CAH routing algorithm achieves almost the same degree of load balancing as the HAS algorithm and the same cache hit rate as the CAH algorithm for reverse proxy servers in various web site environments.

ERS-1/2 wind scatterometers (WSC) data sets may contain cells in which two, instead of three, measurements are available. These data sets are called incomplete. Operational inversion procedures discard such data sets and therefore no wind field is estimated. This is very limiting in semi-closed seas such as the Mediterranean Sea. In this paper we propose a new inversion procedure capable to retrieving near surface wind fields from incomplete data sets. This procedure is an enhancement of an algorithm already proposed and tested by the authors. A set of comprehensive experiments are presented and discussed. It is shown that the inversion procedure gets to remarkable results even in presence of a large number of doublets.