A voltage-controlled ring oscillator with an RC delay as an additional delay to vary the oscillation frequency is proposed. The use of MOS resistors provides a wide range tuning ability from 40 Hz to 366 MHz. The proposed circuit also enables implementation of a low frequency voltage-controlled ring oscillator with relatively smaller devices than the conventional one.

Adaptive Battery Conservation Management (ABCM), an effective form of power conservation for mobile terminals in an always-connected environment, was proposed and evaluated in a previous published work. The ABCM method employs three states: active, dormant, and the Battery Saving Mode (BSM). The BSM is defined as a battery-saving state; in the BSM, the mobile terminal saves power by intermittently receiving paging notifications via a paging channel between the packet bursts of a session. Two control parameters, the sleep-timer and paging interval, are set up according to packet class and are the keys to the performance of a system with this method. In real-time communications, a long sleep-timer and short paging interval are selected to minimize buffering delay. In non-real-time communications, on the other hand, a short sleep-timer and long paging interval are chosen to reduce power consumption by the mobile terminal. Our previous evaluation showed that the method is effective as a means for power conservation in non-real-time communications. In real-time communications, on the other hand, the ABCM method provides shorter buffering delays and the same battery-conservation performance as the conventional method. To further improve the ABCM method's performance, we now propose an enhanced ABCM method that employs multiple BSM sub-modes, each of which has a different paging interval. As dormant periods become longer, the mobile terminal makes transition to successive sub-modes, each of which has a longer interval than the previous one. In this paper, we evaluate the battery conservation effect of the ABCM method through theoretical analysis and computer simulation. Numerical evaluation indicates that the ABCM method will be suitable for the broadband multimedia packet-radio systems of the future.

The equidistortion principle[1] has recently been proposed as a basic principle for design of an optimal vector quantization (VQ) codebook. The equidistortion principle adjusts all codebook vectors such that they have the same contribution to quantization error. This paper introduces a novel VQ codebook design algorithm based on the equidistortion principle. The proposed algorithm is a variant of the law-of-the-jungle algorithm (LOJ), which duplicates useful codebook vectors and removes useless vectors. Due to the LOJ mechanism, the proposed algorithm can establish the equidistortion condition without wasting learning steps. This is significantly effective in preventing performance degradation caused when initial states of codebook vectors are improper to find an optimal codebook. Therefore, even in the case of improper initialization, the proposed algorithm can achieve minimization of quantization error based on the equidistortion principle. Performance of the proposed algorithm is discussed through experimental results.

This paper deals with the wave scattering from a periodic surface with finite extent. Modifying a spectral formalism, we find that the spectral amplitude of the scattered wave can be determined by the surface field on only the corrugated part of the surface. The surface field on such a corrugated part is then expanded into Fourier series with unknown Fourier coefficients. A matrix equation for the Fourier coefficients is obtained and is solved numerically for a sinusoidally corrugated surface. Then, the angular distribution of the scattering, the relative power of each diffraction beam and the optical theorem are calculated and illustrated in figures. Also, the relative powers of diffraction are calculated against the angle of incidence for a periodic surface with infinite extent. By comparing a finite periodic case with an infinite periodic case, it is pointed out that relative powers of diffraction beam are much similar in these of diffraction for the infinite periodic case.

Fingerprinting is one of the digital watermarking techniques, and is becoming more important as a copyright protection technique. Fingerprinting must resist collusion attacks. As a security index, "c-secureness" has been proposed, but it has been known that there is indeed no c-secure code. In this paper, we introduce a new index to measure the resilience of fingerprinting for collusion attacks and obtain some upper bounds and a lower bound on the index.

In a bidirectional wavelength-reused system, polarization control is used to reduce power penalty induced by coherent mixing of the signal with Rayleigh backscattering. The reduction of the effect of Rayleigh backscattering is theoretical study and experimental demonstration. For a 50km, 10Gb/s bidirectional transmission system, an error floor of about 510-10 under the worst polarization state is occurred. Nevertheless, the power penalty is reduced from 3.5dB to only 0.3dB when the signals are under optimum polarization control. The results indicate that the proposed technique may find vast applications in bidirectional ring networks with add/drop as well as cross-connect nodes using wavelength-reused technology.

We propose a novel pixel pattern-based approach for texture classification, which is independent of the variance of illumination. Gray scale images are first transformed into pattern maps in which edges and lines, used for characterizing texture information, are classified by pattern matching. We employ principal component analysis (PCA) which is widely applied to feature extraction. We use the basis functions learned through PCA as templates for pattern matching. Using PCA pattern maps, the feature vector is comprised of the numbers of the pixels belonging to a specific pattern. The effectiveness of the new feature is demonstrated by applications to the image retrievals of the Brodatz texture database. Comparisons with multichannel and multiresolution features indicate that the new feature is quite time saving, free of the influence of illumination, and has comparable accuracy.

One of the difficulties in routing problem is in wirability which is to guarantee a physical connection of a given topological route. Wirability often fails since the width of a wire is relatively large compared with the size of modules. As a possible solution, this paper proposes an incremental wiring algorithm which generates wires net-by-net without overlapping other pre-placed circuit elements. The idea is to divide a wire into a series of rectangles and handles them as modules with additional constraints to keep the shape of the wire. The algorithm was implemented and experimented on a small instance to show its promising performance.

Assume that each edge e of a graph G is assigned a list (set) L(e) of colors. Then an edge-coloring of G is called an L-edge-coloring if each edge e of G is colored with a color contained in L(e). In this paper, we prove that any series-parallel simple graph G has an L-edge-coloring if |L(e)| max{3,d(v),d(w)} for each edge e = vw, where d(v) and d(w) are the degrees of the ends v and w of e, respectively. Our proof yields a linear algorithm for finding an L-edge-coloring of series-parallel graphs.

We demonstrate a multi-wavelength (40WDM 10Gbit/s) optical packet router capable of processing 4 Gigapackets/s based on all-optical label generation and recognition using 16-bit, 20Gbit/s four-level phase coding superstructure fibre Bragg gratings. Error free operation is obtained for the switched packets when all 40 channels are transmitting simultaneously.

It is found that the supercontinuum spectrum is generated from cross-phase modulated soliton pulses which are propagated through a dispersion-flattened/decreasing fiber with low birefringence. The cross-phase modulation is achieved by exciting two orthogonally polarized modes in a birefringent fiber and the effect of input azimuth of linearly polarized pulses is discussed theoretically and numerically.

Karger, Motwani and Sudan presented a graph coloring algorithm based on semidefinite programming, which colors any k-colorable graph with maximum degree Δ using (Δ1-2/k) colors. This algorithm leads to an algorithm for k-colorable graph using (n 1-3/(k+1)) colors. This improved Wigderson's algorithm, which uses O(n1-1/(k-1)) colors, containing as a subroutine an algorithm using (Δ+1) colors for graphs with maximum degree Δ. It is easy to imagine that an algorithm which uses less colors in terms of Δ leads to an algorithm which uses less colors in terms of n. In this paper, we consider this influence assuming that we have an algorithm which uses (Δ 1-x/k) colors for 2

A virtual private network (VPN) service is likely to be used by customers as a replacement for networks constructed using private lines, and thus its functionality should include the performance guarantee provided to those customers. To provide guaranteed services, the network provider allocates appropriate capacities to multiple virtual backbone networks such that the underlying network can be shared among them. As VPN users are demanding reliable and dynamic allocation of capacities, recently the capacity resizing approach has been considered as a cost efficient way of providing virtual network services. We propose a new scheme for dynamic allocation of virtual link capacities. The allocated capacities are adjusted dynamically according to the users' requests such that their capacities are increased in a fair manner and the total reservation does not overwhelm the underlying network. Depending on the network's status and allocation policy, a virtual link may increase or decrease its capacity, for example, for a monetary incentive. VPN users send control packets whenever they want to resize their capacities, and the network handles them in an efficient and fair way. The simulation and analytic results in this paper show that our scheme is simple and robust such that the users and the network communicate using simple control packets and the link capacities are allocated efficiently.

A broadband access network is required for supporting the increased Internet data traffic. One of the most cost-effective solutions is the Ethernet Passive Optical Networks (E-PONs) with the efficient bandwidth assignment function by which the upstream bandwidth can be shared among access users. To satisfy the services with heterogeneous QoS characteristics, it is very important to provide QoS guaranteed network access while utilize the bandwidth efficiently. In this paper, a dual DEB-GPS scheduler in E-PON is presented to provide delay-constraint and lossless QoS guarantee to QoS service and maximize the bandwidth to best-effort service. Simulation results show our scheme outperforms the conventional bandwidth allocation scheme in E-PON system.

In this paper we study traffic engineering in Multiprotocol Label Switching (MPLS) networks. We consider off-line computation of disjoint working and restoration paths where path rerouting is used as the restoration scheme. We first compute maximum number of paths for each demand such that paths satisfy diversity requirements. Using the generated path set we study four different approaches for selecting working and restoration paths, and formulate each method as an Integer Linear Programming (ILP) problem. The first two methods treat working and restoration path design problems separately. We propose two new path design methods that jointly optimize the working and restoration paths. A traffic uncertainty model is developed in order to evaluate performances of these four approaches based on their robustness with respect to changing traffic patterns. We compare these design approaches based on the number of additional demands carried and the distribution of residual capacity over the network. It is shown through simulations that the weighted load balancing method proposed in this paper outperforms the other three methods in handling traffic demand uncertainty.

We have exploited a high-power-tolerant variable optical attenuator (VOA) based on the fused fiber coupler in the all-fiber structure. A newly designed VOA employs the external modulation by forcing an axial stress in the tapered region of the fused fiber coupler. In the tapered region, the axial stress changes the refractive index of silica glasses resulting in a change in the coupling coefficient of the coupler. In this paper, we explain the principle of the novel device, VOA, and the optimized fabrication of the fused fiber coupler for the attenuation. The changes of the transmission spectrum for the coupler and the optical power spectrum for pump laser diode (LD), whose center wavelength is 1.47µm, versus the axial displacement were verified by experiment. The possibility of the wavelength uniformity less than 1dB over the range of 1460-1500nm was also obtained by another coupler under a different fabrication condition. The polarization-dependent loss (PDL) at 1.47µm wavelength was 0.65dB for a maximum displacement of 150µm. The designed device has an attractive feature of another output port of the coupler available as a monitoring tap. The device showed a high attenuation above 34dB and an insertion loss below 0.15dB. The all-fiber structure can provide less alignment, which in turn provides a high power tolerance. This novel design, moreover, has a simple and cost-effective structure.

The c-Secure CRT code is a collusion-secure fingerprinting code whose code length is reduced by using the Chinese Remainder Theorem. The tracing algorithm for the c-secure CRT code drops its performance of traitor tracing when random errors are added to the codewords. In this paper, we show two approaches to enhance random-error-resilience to the tracing algorithm of the c-secure CRT code. The first approach is introducing thresholds for the distinction of the detected part of the embedded data called detected blocks. We propose a method to derive appropriate values of the thresholds on an assumption that the tracer can estimate the random error rate. This modification extends the capability of traitor tracing to the attacks in which the alteration rate of the detected blocks is not fixed to 0.5. The second approach is extending the scope of the search for the detected blocks. With numerical results by computer simulations, we confirmed an impressive improvement of random-error-resilience of a c-secure CRT code.

Ring networks have been extensively studied and installed for communication services. In actual ring networks, nodes are usually allocated at random positions. Two nodes separated far from each other along the route of a ring network may be physically allocated near each other. Adding a supplementary link directly connecting such nodes can shorten the connection paths between the two nodes as well as between other neighboring node pairs. Aggregated length of connection paths of the network can be reduced. Although such a network can be regarded as being composed of two small ring networks sharing the supplementary link, we regarded the network as being modified from a single regular ring network by adding a supplementary link, and thus we quantitatively evaluated the effect of the network modification. We analyzed, for the first time, number of connection paths in the links of networks with or without a supplementary link. A full-mesh topology was assumed, and two types of connection were examined: a single-path and a 2-path connection. The results of this analysis were then used to evaluate system costs and reliability of the networks. The evaluation confirmed that adding a supplementary link is effective in terms of cost reduction and reliability improvement under certain conditions.

This paper presents an innovative 155Mb/s burst-mode laser transmitter chip, which was designed and successfully demonstrated, and contains several new subsystems: a digitally programmed current source, programmable up to 120mA with a resolution of 0.1mA, a fast but accurate intermittent optical level monitoring circuit, and a digital Automatic Power Control (APC) algorithm. This generic and intelligent chip was developed in a standard digital 0.35µm CMOS process. Extensive testing showed a high yield and algorithm stability, as well as excellent performance. During initialization, when the transmitter is connected to the Passive Optical Network (PON) for the first time, maximum three Laser Control Fields (LCF) are needed, with a length of 17bytes (0.88microsecond at 155Mb/s), to stabilize the laser output power. In this short time, the chip can regulate the launched optical output power of any FSAN (Full Service Access Network) compliant laser diode to the required level, even in the extreme circumstances caused by outdoor operation or by battery backup operation during power outages. Other tests show that the chip can further stabilize and track this launched optical power with a tolerance lower than 1dB over a wide temperature range, during the burst mode data transmission. The APC algorithm intermittently adjusts the optical power to be transmitted in a digital way, starting from loosely specified but safe preset values, to the required stable logic "1" and "0" level. No laborious calibration of the laser characteristic curve and storage of the calibration values in lookup tables are needed, nor any off-chip adjustable component. The power consumption is significantly reduced by disabling inactive circuitry and by gating the digital high-speed clock. Although this laser transmitter was developed for FSAN PON applications, which are standardized at a speed of 155Mb/s upstream, the design concept is quite generic and can be applied for developing a wide range of burst mode laser transmitters, such as required for Gigabit PON systems or other TDMA networks.

In this paper, we present an Internet personal live-broadcasting server system. Our solution is not only for experts but also for amateur users who want to broadcast using simple multimedia equipment. For scalable broadcasting services, we developed multiple-channel establishment and channel expansion. Concurrent services for a large number of broadcasting channels are effectively provided. Also, the capacity of channels can be expanded as the number of participants increases. Furthermore, for the sake of complete live broadcasting with high-quality transmission, the system supports both TCP (transmission control protocol) and UDP (user datagram protocol) according to the status of network environments as well as the received packet loss in the user system. The performance of the system is effectively evaluated at such practical commercial sites as well-known community and E-business sites.