A generic multilevel quality-of-service (QoS) model for distributed multimedia applications is presented. QoS mapping mechanisms are required to translate the QoS parameters among the hierarchical levels. One QoS mapping mechanism based on the spline functions is proposed, hence two splines are compared. One is natural splines and the other is B-splines. QoS measurement experiments were conducted, and it is found that the B-splines give more accurate mapping results than the natural splines once the knots for the splines are selected appropriately.

We investigated the electrical properties of hole transport materials such as TPD, α-NPD and m-MTDATA using in-situ field effect measurement. TPD, α-NPD and m-MTDATA films showed p-type semiconducting properties, and their electrical parameters such as conductivity, carrier mobility and carrier concentration were obtained. We also examined the effect of the substrate temperature during vacuum deposition and the thermal treatment after deposition, on the electrical parameters of the films. Experimental results showed that conductivity and carrier mobility decreased as the substrate temperature increased over the glass transition temperature. These decreases in conductivity and carrier mobility as a result of thermal treatment appear to be strongly related to the degradation mechanism of organic electroluminescent devices.

The surface potential built across vacuum deposited phthalocyanine (Pc) films on aluminum electrode was investigated by means of electro-modulation spectroscopy. The sandwich-type cells with thin air gap, which becomes a good insulator were used in order to avoid the influence of charge injection. The existence of the surface potential at the metal/organic-material interface induced 1f referenced electro-reflectance (ER) signals. As a result, the surface potential built across vacuum deposited Pc films on aluminum electrode was estimated to be 1.25 V.

Wavelength division multiplexed (WDM) routed optical networks represent the direction towards future high-capacity wide-area network applications. A serious issue in WDM-routed networks, though, is light-path allocation which requires a combination of optical routing and wavelength assignment. While near-optimal-routing and wavelength-assignment algorithms aimed at minimizing network wavelength requirements have been reported, the practicability of wavelength-routed optical networks depends on the number of wavelengths required to satisfy a given traffic demand. In this paper, we proposed two symmetrical routing and wavelength-assignment methods for optical networks with a Grid or ShuffleNet physical topology. Here, we consider the case of non-adaptive wavelength routing systems, where the operations performed in nodes are independent of the network traffic load. In this case, the routing differs somewhat from that in adaptive routing networks where the routing function may produce different results at different times. The path followed by a wavelength never changes in non-adaptive wavelength-routing networks. When all N(N-1) node-pairs are to be connected, our methods lower the wavelength requirement to (or close to) its calculated minimum. Symmetry is a basic feature of both these regular topologies, but there are differences in the features within the topologies. Our goal has been to try to make use of the symmetry, and the differences in the native symmetry features, of these regular topologies to yield a lower wavelength requirement.

This letter presents a code which corrects single bit errors in any location of the word as well as l-bit burst errors occurred in an important part of the word. The proposed code is designed by product of the parity check matrix of the l-bit burst error correcting codes and the matrix which converts input unequal errors into equal errors. This letter also demonstrates the evaluation of the code, and presents the extended codes with two-level burst error correcting capabilities by interleaving.

Traditional watermarking methods based on spectrum manipulation use watermark bit as a colored noise. However, those methods show poor robustness for filtering and audio compression because of only a few spectrum coefficients being modified. In this paper, we propose a new algorithm for robust audio watermarking by using spectrum warping. Our watermark-embedding scheme is not based on spectrum coefficient manipulation, but based on warping spectrum that shifts a block of spectrum coefficients nonlinearly. The host audio signal is divided appropriately into small segments and then a non-orthogonal transform, such as bi-linear transform, is used for each segment to embed as well as to extract watermarks. Because the proposed scheme uses small segment length, we can afford to embed signature information many times into audio signal without severe degradation of SNR. Our multiple embedding scheme increases robustness against abnormal distortion of watermarked signal and has no bit error rate in MPEG1 Layer-3 128 kbps and 96 kbps compression as well as low/high pass filtering.

The transfer characteristic of an integrator is affected by excess-phase shift caused by the parasitic capacitance. The phase compensation is obtained by introducing zeros to generate phase lead. This paper proposes a phase compensation technique for the differential signal input integrator. The proposed technique is employing feedforward signal current source. The fifth-order leapfrog Chebyshev low-pass filter with 0.5 dB passband ripple is designed using the integrator with the proposed phase compensation. Further, an autotuning phase compensation system using the proposed technique is realized by applying a PLL system. The effectiveness of the proposed technique is confirmed by PSPICE simulation. The simulation results of the integrator with the proposed phase compensation shows that excess-phase cancellation is obtained at various unity gain frequencies. The accurate filter characteristic of the fifth-order leapfrog filter is obtained by using the autotuning phase compensation system. The passband of the filter is improved over wide range of frequencies. The proposed technique is suitable for low voltage application.

In an Multi-Protocol Label Switching (MPLS) network domain, Asynchronous Transfer Mode--Label Switch Routers (ATM-LSRs) are considered the best candidate for providing the highest forwarding capability. ATM-LSRs implement a VC-merging scheme that allows many IP routes to be mapped into the same VPI/VCI label, hence supporting scalability. The VC-merging requires reassembly buffers to reconstruct an original packet from its segmented but interleaved AAL-5 cells. In this paper, we analyze the performance of an ATM-LSR with partial VC-merging capability and investigate the impact of VC-merging on the requirement of the reassembly and output buffer. The numerical computation complexity of the mathematical analysis can be reduced from O(M4) to O(M2), where M is the total number of ON-OFF sources. We also propose a closed-form equation, which approximates the distribution of the output buffer with satisfactory accuracy. Numerical results show that when incoming cells are severely interleaved, the VC-merging needs the reassembly buffer size to be of the same order as the output buffer size, which cannot be ignored.

The IETF Mobile IP defines two multicast options: remote subscription (RS) and bi-direction tunneling (BT). In order to synthesize the strong points of these two IETF multicast options, we propose a hybrid approach, mMOM, which selectively uses two IETF multicast options based on the mobility of mobile hosts. Whenever a mobile host requests its first registration to a certain foreign agent, the corresponding foreign agent starts the service using the BT option. Afterwards, if it requests re-registration to the same foreign agent, the foreign agent considers it to be relatively immobile and continues services using the RS option. We propose a new metric to compare heterogeneous algorithms. Simulation results show that our approach outperforms all others.

In positioning systems NLOS (Non-Line of Sight) errors always cause remarkable positive bias and directly increase range measurement errors. In this paper, a new method is proposed to calibrate NLOS errors in positioning systems by using the relationship between mean excess delay and delay spread measured at a mobile station. The computer simulations showed that the proposed calibration technique effectively reduces the positioning error caused by urban NLOS environment.

In this paper, we present a method to analyze the steady-state performance of a complex coefficient adaptive IIR notch filter which is useful for the rejection of multiple narrow-band interferences from broad-band signals in quadrature phase shift keying (QPSK) spread-spectrum communication systems. The adaptive notch filter based on the simplified gradient algorithm is considered. Analytical expressions have been developed for the conditional mean and variance of notch filter output. The signal-to-noise ratio improvement factor is also obtained from which the validity of the use of the notch filter can be concluded. Finally, the results of computer simulations are shown which confirm the theoretical predictions.

In this paper the authors propose a method for designing the Virtual Private Network (VPN) that guarantees a strict Quality of Service (QoS) over IP networks. The assumed QoS metric is PLP (Packet Loss Probability), and it is guaranteed probabilistically by the provision of an appropriate equivalent bandwidth. We consider two network architectures for constructing VPN, the customer pipe scheme and the Hose scheme, and we present an analytic model to compute the amount of the required bandwidth for the two schemes. Finally, we investigate the validity of the proposition via numerical experiments.

A VLSI algorithm for division in GF(2m) with the canonical basis representation is proposed. It is based on the extended Binary GCD algorithm for GF(2m), and performs division through iteration of simple operations, such as shifts and bitwise exclusive-OR operations. A divider in GF(2m) based on the algorithm has a linear array structure with a bit-slice feature and carries out division in 2m clock cycles. The amount of hardware of the divider is proportional to m and the depth is a constant independent of m.

For ubiquitous computing and communication, a mobile node needs to change upon movements its network- and link-layer points of attachment to the Internet. Conventionally, the network-layer protocol is unaware of the link-layer changes, so IP datagrams to and from a moving node could be lost. Considerable system performance degradation might therefore result. This paper presents a scheme to integrate the handoff procedures of the two layers in the context of Mobile IP with route optimization. Experiment results show that our scheme is promising and can reduce packet loss due to host migrations substantially.

This paper addresses a classic question about whether transmit power control (TPC) can increase the spectrum efficiency of a TDMA system and an FDMA cellular system as in the case of a DS-CDMA cellular system. Two types of TPC schemes are considered; one is slow TPC that regulates the distance dependent path loss and shadowing loss, while the other is fast TPC that regulates multipath fading as well as path loss and shadowing loss. In addition to TPC, antenna diversity reception is considered. The allowable interference rise factor χ, which is defined as the interference plus background noise-to-background noise power ratio, is introduced. The simple expressions for the signal-to-interference plus background noise power ratio (SINR) at the diversity combiner output using maximal-ratio combining (MRC) are derived to obtain the reuse distance by computer simulations. The impact of joint use of TPC and antenna diversity reception on the spectrum efficiency is discussed. It is found that the joint use of fast TPC and antenna diversity is advantageous and larger spectrum efficiency can be achieved than with no TPC. On the other hand, the use of slow TPC is found advantageous only for small values of standard deviation of shadowing loss; however, the improvement in the spectrum efficiency is quite small.

A novel power spectral density accumulation (PSDA) method for estimating the bandwidth of the clutter spectra is proposed, based on a priori knowledge of the shape of the clutter spectra. The comparison of the complexity and the performance between the PSDA method and the general ones is presented. It is shown that the PSDA method is effective for the short-time clutter data in the practical application.

Cutoff frequencies and the modal fields in hollow conducting waveguides of arbitrary cross section are frequently calculated by the method of solving integral equations. This paper presents some improvements for the method by the integral equations. The improved method can calculate the cutoff frequencies and the modal fields only by using the real number, and this method can remove extraneous roots when calculating the cutoff frequencies. The former method calculates the cutoff frequency and the fields only at the cutoff frequency, but the improved method can calculate the fields at arbitrary phase constants.

In this paper we introduce a bottom-up pushdown tree transducer (b-PDTT) which is a bottom-up tree transducer with pushdown storage (where the pushdown storage stores the trees) and may be considered as a dual concept of the top-down pushdown tree transducer (t-PDTT). After proving some fundamental properties of b-PDTT, for example, any b-PDTT can be realized by a linear stack with single state and converted into G-type normal form which corresponds to Greibach normal form in a context-free grammar, and so on, we compare the translational capability of a b-PDTT with that of a t-PDTT.

In interconnection networks, deadlock recovery has been studied in routing strategy. The routing strategy for the deadlock recovery is intended to optimize the routing performance when deadlocks do not occur. On the other hand, it is important to improve the routing performance by handling deadlocks if they occur. In this paper, a routing strategy for suspensive deadlock recovery called an escape-restoration routing is proposed and its performance is evaluated. In the principle of the proposed techniques, a small amount of exclusive buffer (escape-buffer) at each router is prepared for handling one of deadlocked packets. The transmission of the packet is suspended by temporarily escaping it to the escape-buffer. After the other deadlocked packets were sent, the suspended transmission resumes by restoring the escaped packet. Evaluation results show that the proposed techniques can improve the routing performance more than that of the previous recovery-based techniques in handling deadlocks.

With increasing Internet traffic congestion, the provision of reliable transmission and packet loss recovery continues to be of substantial importance. In this paper, we analyze a new recovery method using punctured convolutional codes, demonstrating the simplicity and efficiency of the proposed method for the recovery of lost packets. The analysis provides a method for determining the recoverability and the post-reconstruction receiving rate for a given convolutional code. The exact expressions for calculating the recovery rate are derived for a number of convolutional codes and the (2, 1, m) punctured convolutional code. Where packet loss probabilities are in the range typically found in Internet transmissions, the convolutional code-based method delivers superior performance over the traditional parity method with the same redundancy.