We present a mechanism, named the law of the jungle (LOJ), to improve the Kohonen learning. The LOJ is used to be an adaptive vector quantizer for approximating nonstationary probability distribution functions. In the LOJ mechanism, the probability that each node wins in a competition is dynamically estimated during the learning. By using the estimated win probability, "strong" nodes are increased through creating new nodes near the nodes, and "weak" nodes are decreased through deleting themselves. A pair of creation and deletion is treated as an atomic operation. Therefore, the nodes which cannot win the competition are transferred directly from the region where inputs almost never occur to the region where inputs often occur. This direct "jump" of weak nodes provides rapid convergence. Moreover, the LOJ requires neither time-decaying parameters nor a special periodic adaptation. From the above reasons, the LOJ is suitable for quick approximation of nonstationary probability distribution functions. In comparison with some other Kohonen learning networks through experiments, only the LOJ can follow nonstationary probability distributions except for under high-noise environments.

This paper describes an efficient method to simulate lossy coupled transmission lines based on the delay evaluation technique. First, we review the previous methods, and refer to several problems concerned with these methods. Next, a novel waveform relaxation-based simulation method is proposed, which uses the delay evaluation technique. This method enables to obtain the accurate transient waveforms using smaller number of moments than the other moment methods use, and is modified for acceleration by the generalized line delay window partitioning (GLDW) technique. Finally, this method is implemented in the waveform relaxation-based circuit simulator DESIRE3T+, and the performance is estimated.

In this paper, we present several traffic handling schemes for improving the QoSs (quality-of-services) in a micro-cell based PCS (personal communication services) network. Traffic handling schemes are devised for the efficient use of the limited radio resources with the increasing number of users and multimedia traffic. Both mathematical analysis and computer simulations are carried out for the performance evaluation in terms of the blocking probability of new call, the forced termination probability of handoff voice and data and the average delay of data. Analytical models by bivariate Markov processes are provided. It reveals that a finite queueing scheme for handoff delay sensitive data guarantees QoS metrics, such as the blocking probability of new voice and data and forced termination probability of handoff voice and data, as well as the efficient use of radio resources. The optimal number of reserved channels for handoff delay sensitive data and the optimal number of reserved channels for handoff traffic (in reserved channel scheme) are investigated and obtained. Dynamically controlled reserved channel schemes turn out to provide no significant performance improvement.

Subharmonically Injection-locked oscillators (ILO's) with very wide injection-locking ability are presented. Two types of ILO MMIC's with this ability are proposed. The oscillation frequency tuning function of the ILO MMIC is very useful for expansion of the injection locking range at higher subharmonics. One consists of a shunt varactor diode inserted into the oscillation loop, and the other incorporates a vector-combining configuration with in-phase divider and 90 degree hybrid. Using three-dimensional MMIC's technology which can offer miniature and high-density passive circuits, the vector-combining type ILO is formed in a very compact area of 1. 7 mm2. Fabricated 20 GHz-band ILO achieves a wide tuning ranges of 870 MHz, resulting in a very wide locking range for higher subharmonics. The wide frequency tuning ability also reduces phase noise, shortens a locking time and compensates the center frequency deviation against temperature, as well as increasing locking range. The measured results show that the ILO configuration is extremely suitable for realizing simple, fully monolithic and low phase noise millimeter-wave frequency synthesizers.

This paper describes two dimensional (2D) equalization scheme of orthogonal coding multi-carrier CDMA for reverse link of mobile communication systems. The purpose of the 2D equalization is the reduction of Multiple Access Interference (MAI) which is caused by the random access and the different propagation path from each mobile station. The orthogonal coding multi-carrier CDMA multiplexes all mobile stations' data by Code Division Multiplexing (CDM). The 2D coding scheme spreads a preamble signal at time (in subchannel signals) and frequency (between subchannel signals) domains. The 2D decoding scheme estimates transmission delay time and instantaneous fading frequency from preamble signal for individual mobile stations and compensate the received data using these estimation values to reduce MAI.

This paper presents a technique to transmit 16QAM signals in mobile radio environments by using extended symbol-aided estimation (ESAE) method for compensating the multipath fading effect. The main results of this paper are the symbol error rate (SER) performance analyses for BPSK and 16QAM systems using the proposed estimation method under Rician fading. The analytical results demonstrate better performance of the proposed systems compared with those of the conventional systems under fast and severe fading, especially in the region of high signal to noise ratio.

This letter presents a novel variable-rate vector quantizer (VQ) design algorithm, which is a hybrid approach combining a genetic algorithm with the entropy-constrained VQ (ECVQ) algorithm. The proposed technique outperforms the ECVQ algorithm in the sense that it reaches to a nearby global optimum rather than a local one. Simulation results show that, when applied to the image coding, the technique achieves higher PSNR and image quality than those of ECVQ algorithm.

Quality of service requirements are satisfied conjointly by the service model, which determines how resources are shared and by network engineering, which determines how much capacity is provided. In this paper we consider the impact of the adopted charging scheme on the feasibility of fulfilling QoS requirements. We identify three categories of charging scheme based respectively on flat rate pricing, congestion pricing and transaction pricing.

Cell delay variation (CDV) has been considered as an important performance measure due to the stringent timing requirement for video and multimedia services. In this paper we address the problem of CDV performance guarantee in virtual path (VP)-based ATM multiplexing. We propose a rate-based and non-work-conserving scheduling algorithm, called interleaved round robin (IRR), for serving traffic streams among VPs into the outgoing link. Through our performance analysis, the proposed scheme is capable of providing upper and lower bounds on the inter-visit time (IVT) for each VP, where the difference between the upper bound and the lower bound is simply dependent upon the number of multiplexed VPs. The distribution of VP IVT scheduled by an IRR server can also be well approximated using a random incidence technique. In addition to the VP-level CDV performance, we further examine the virtual connection (VC)-level CDV incurred within a multi-stage network through simulation study. The simulation results show that the IRR server can provide traffic regulation and smoothness at each network node. Moreover, the CDV distribution of a tagged VC is insensitive to the source traffic characteristic, node location, and the hop count traversed in the network.

We have developed and fabricated an LSI called the FMPP-VQ64. The LSI is a memory-based shared-bus SIMD parallel processor containing 64 PEs, intended for low bit-rate image compression using vector quantization. It accelerates the nearest neighbor search (NNS) during vector quantization. The computation time does not depend on the number of code vectors. The FMPP-VQ64 performs 53,000 NNSs per second, while its power dissipation is 20 mW. It can be applied to the mobile telecommunication system.

In a secure partially blind signature scheme, the signer assures that the blind signatures issued by him contains the information he desires. The techniques make it possible to minimize the unlimited growth of the bank's database which storing all spent electronic cash in an anonymous electronic cash system. In this paper we propose an efficient partially blind signature scheme for electronic cash. In our scheme, only several modular additions and modular multiplications are required for a signature requester to obtain and verify a signature. It turns out that the proposed scheme is suitable for mobile clients and smart-card applications because no time-consuming computations are required, such as modular exponentiation and inverse computations. Comparing with the existing blind signature schemes proposed in the literatures, our method reduces the amount of computations for signature requesters by almost 98%.

We analyze the behavior of a finite FIFO buffer in an advanced packet-switched network. It is modeled by a multi-class single-server delay-loss system Σχi MAP i/ PH /1/m. As stochastic process of the system it yields a finite Markov chain with QBD structure and two boundary sets. Our main result is a new representation of its steady-state vector in terms of a linear combination of exactly two matrix-geometric components. Furthermore, we present an efficient algorithm to solve the corresponding matrix-quadratic equations. As second key result we state a new efficient recursive procedure to calculate the congestion characteristics of this delay-loss system.

The Phase Locked Loop (PLL) for clock recovery used in a single chip 155. 52 Mb/s4-Ch CMOS LSI (QPLC) for SONET/SDH termination is described in this letter. This LSI is the first quad-channel ATM physical layer controller chip in which each channel has a clock recovery PLL achieving 55ps rms jitter, using current regulated constant amplitude differential VCO and the triple well structure.

In the wireless ATM network, the key issue is to guarantee various QoS (Quality of Service) under the conditions of the limited radio link bandwidth and error prone characteristics. In this paper, we show a combination method of the error correction schemes, which is suitable to establish multimedia wireless ATM Networks while keeping an efficient use of the limited bandwidth. We consider two levels of FEC; a bit-level and a cell-level to guarantee cell loss probabilities of real time applications. By combining two levels of FEC, various requirements on cell loss can be met. We then apply the bit-level FEC and ARQ protocol for the data communication; tolerant to the delay characteristics. Through the analytical methods, the required overheads of FECs are examined to satisfy the various QoS requirements of CBR connections. The mean delay analysis for the UBR service class is also presented. In numerical examples, we show how the combination scheme to guarantee various cell loss requirements affects the call blocking probability of the CBR service class and the delay of UBR service class.

We consider linearizable implementations of shared FIFO queues and general deterministic objects on a distributed message-passing system which provides a real-time timer. The efficiency of an implementation is measured by the worst-case response time res_time(op) for each operation op of the implemented objects. We show the following results under the assumption that all message delays are in the range [d-u,d] for some constants d and u (0 u d). We first present an implementation of deterministic objects with res_time(opa)=u for any ack-type operation opa and res_time(opv)=2d for any val-type operation opv, where an ack-type operation is an operation which always returns a unique response and a val-type operation is an operation which is not ack-type. We also consider an implementation of FIFO queues, which have two kinds of operations, enq(v) and deq. We show that, for any implementation of FIFO queues, (1) res_time(enq(v)) u(n-1)/n holds for some v where n is the number of processes, and (2) res_time(deq) d+u/2 holds in the case of u (2/3)d.

Multi-recast techniques make it possible for a voter to participate in a sequence of different designated votings by using only one ticket. In a multi-recastable ticket scheme for electronic voting, every voter of a group can obtain an m-castable ticket (m-ticket), and through the m-ticket, the voter can participate in a sequence of m different designated votings held in this group. The m-ticket contains all possible intentions of the voter in the sequence of votings, and in each of the m votings, a voter casts his vote by just making appropriate modifications to his m-ticket. The authority cannot produce both the opposite version of a vote cast by a voter in one voting and the succeeding uncast votes of the voter. Only one round of registration action is required for a voter to request an m-ticket from the authority. Moreover, the size of such an m-ticket is not larger than that of an ordinary vote. It turns out that the proposed scheme greatly reduces the network traffic between the voters and the authority during the registration stages in a sequence of different votings, for example, the proposed method reduces the communication traffic by almost 80% for a sequence of 5 votings and by nearly 90% for a sequence of 10 votings.

We present techniques to implement fair-sharing on both link bandwidth and buffer space in a switch or router. Together they possess the following merits: 1. solving the counter-overflow problem; 2. avoiding the "credit" accumulation issue; 3. integrating bandwidth allocation with buffer management. The simplicity of this method makes it a viable candidate for implementational use on switches and routers.

We examine the effectiveness of shaping and policing mechanisms in reducing the inherent variability of fractal traffic, with the objective of increasing network operating points. Whether a shaper simply spaces a flow or allows small bursts according to a leaky bucket, we show using analytical arguments that, i) the Hurst parameter, which describes the asymptotic variability of the traffic, is unaffected; and ii) while the traffic can be made smoother over time scales smaller than one corresponding to the shapers buffer size, fluctuations over longer time scales cannot be appreciably altered. We further show that if shaping is used to reduce buffer size requirements at a network bottleneck, any savings here are offset by the increased buffer requirements at the shapers. Perhaps the most significant deficiency of shaping identified here is that it is necessary to model individual streams to a level of accuracy that is not feasible in practice. In contrast, statistical multiplexing can achieve reasonable network efficiencies by only requiring characterizations of aggregate traffic.

One of the important challenges in the design of ATM networks is how to provide quality-of-service (QoS) while maintaining high network resource utilization. In this paper, we discuss the role of real-time traffic characterization in QoS control for ATM networks and review several approaches to the problem of resource allocation. We then describe a particular framework for QoS control in which real-time measurements of a connection stream are used to determine appropriate parameters for usage parameter control (UPC). Connection admission control (CAC) is based on the characterization of the aggregate stream in terms of the individual stream UPC descriptors, together with real-time measurements.

The classical max-min policy has been suggested by the ATM Forum to support the available bit rate (ABR) service class. However, there are several drawbacks in adopting the max-min rate allocation policy. In particular, the max-min policy is not able to support the minimum cell rate (MCR) requirement and the peak cell rate (PCR) constraint for each ABR connection. Furthermore, the max-min policy does not offer flexible options for network providers wishing to establish a usage-based pricing criterion. In this paper, we present a generic weight-based rate allocation policy, which generalizes the classical max-min policy by supporting the MCR/PCR for each connection. Our rate allocation policy offers a flexible usage-based pricing strategy to network providers. A centralized algorithm is presented to compute network-wide bandwidth allocation to achieve this policy. Furthermore, a simple switch algorithm using ABR flow control protocol is developed with the aim of achieving our rate allocation policy in a distributed networking environment. The effectiveness of our distributed algorithm in a local area environment is substantiated by simulation results based on the benchmark network configurations suggested by the ATM Forum.