In this paper, the design of signature waveforms for asynchronous CDMA systems equipped with a correlation receiver is first considered. Optimal signature waveforms that minimize the average multiple access interference (MAI) at the output of a correlation receiver are found, while satisfying the constraint on available transmission bandwidth. Comparison to signature waveforms previously obtained for synchronous systems is also made to justify the superior performance of the designed signature waveforms in asynchronous systems. Furthermore, for direct-sequence CDMA (DS-CDMA) systems with random signature sequences, the use of multiple chip waveforms is also proposed as a means of suppressing MAI. Bandwidth constrained multiple chip waveforms that maximize the signal-to-interference ratio (SIR) at the output of each correlation receiver are found. Numerical results show that by using double chip waveforms instead of a single chip waveform, it is possible to reduce the MAI by 10% for a fixed transmission bandwidth (or equivalently, to save about 10% of transmission bandwidth for a given SIR requirement). The advantage of using double chip waveforms is also demonstrated in terms of the bit error rate (BER), whose calculation is based on our extension to Holtzman's approximation in.

Future mobile communication systems are expected to support multimedia applications (audio phone, video on demand, video conference, file transfer, etc.). Multimedia applications make a great demand for bandwidth and impose stringent quality of service requirements on the mobile wireless networks. In order to provide mobile hosts with high quality of service in the next generation mobile multimedia wireless networks, efficient and better bandwidth reservation schemes must be developed. A novel traffic-based bandwidth reservation scheme is proposed in this paper as a solution to support quality of service guarantees in the mobile multimedia wireless networks. Based on the existing network conditions, the proposed scheme makes an adaptive decision for bandwidth reservation and call admission by employing fuzzy inference mechanism, timing based reservation strategy, and round-borrowing strategy in each base station. The amount of reserved bandwidth for each base station is dynamically adjusted, according to the on-line traffic information of each base station. We use the dynamically adaptive approach to reduce the connection-blocking probability and connection-dropping probability, while increasing the bandwidth utilization for quality of service sensitive mobile multimedia wireless networks. Simulation results show that our traffic-based bandwidth reservation scheme outperforms the previously known schemes in terms of connection-blocking probability, connection-dropping probability, and bandwidth utilization.

In this paper, we study an effective video-on-demand traffic control algorithm using the metadata over the network supporting bandwidth-renegotiations. The proposed algorithm includes bandwidth smoothing, bandwidth-burstiness estimation and rate adaptation algorithms. The proposed video-on-demand server has not only video database but also metadata database that includes coding information of the compressed video in video database and the traffic burst characteristics with respect to control parameters of the bandwidth smoothing algorithm. Thus, we can predict the traffic properties accurately with a low computational complexity by using the stored metadata, and then determine the efficient bandwidth renegotiating variables such as the renegotiating instants and the required bandwidth in terms of network utilization and video-on-demand service quality. In addition, we present a rate adaptation algorithm that pursues an effective trade-off between spatial and temporal qualities of the decoded video to improve the perceptual video quality when the bandwidth request is rejected.

A major challenge in the design of multimedia networks is to meet the quality of service (QoS) requirements of all admitted users. Regulation and scheduling are key factors for fulfilling such requirements. We propose a rate-based regulation-scheduling scheme in which the regulation function is modulated by both the tagged stream's characteristics and the state information fed-back from the scheduler. The rate-jitter and bandwidth share of each tagged connection are controlled appropriately by considering the system time and the queue length of the scheduler. Simulation results have shown that the proposed scheme works better than other rate-based disciplines.

A new concept of changing inductance values has been proposed, where a part of meander inductor is short circuited to reduce effective line length. Microwave characteristics of the short-circuited meander inductors and the meander inductor without the short circuit have been designed and fabricated on resin circuit boards. The reduction of inductance values by 40% has been successfully realized for the microwave frequency range from 0.5 GHz to 5 GHz for both designed and measured results. Using the proposed structure, low pass filters having two different cut-off frequencies have been designed and tested. Measured cut-off frequency changed 3.0 GHz to 4.2 GHz.

The side channel attack (SCA) is a serious attack on wearable devices that have scarce computational resources. Cryptographic algorithms on them should be efficient using small memory--we have to make efforts to optimize the trade-off between efficiency and memory. In this paper we present efficient SCA-resistant scalar multiplications based on window method. Moller proposed an SPA-resistant window method based on 2w-ary window method, which replaces w-consecutive zeros to 1 plus w-consecutive and it requires 2w points of table (or 2w-1 + 1 points if the signed 2w-ary is used). The most efficient window method with small memory is the width-w NAF, which requires 2w-2 points of table. In this paper we convert the width-w NAF to an SPA-resistant addition chain. Indeed we generate a scalar sequence with the fixed pattern, e.g. |00x|00x||00x|, where x is positive odd points < 2w. Thus the size of the table is 2w-1, which is optimal in the construction of the SPA-resistant chain based on width-w NAF. The table sizes of the proposed scheme are 6% to 50% smaller than those of Moller's scheme for w = 2,3,4,5, which are relevant choices in the sense of efficiency for 160-bit ECC.

This paper addresses bitwidth optimization focusing on leakage power reduction for system-level low-power design. By means of tuning the design parameter, bitwidth tailored to a given application requirements, the datapath width of processors and size of memories are optimized resulting in significant leakage power reduction besides dynamic power reduction. Experimental results for several real embedded applications, show power reduction without performance penalty range from about 21.5% to 66.2% of leakage power, and 14.5% to 59.2% of dynamic power.

In this paper, a novel technique using proportional current feedback is proposed to improve dynamic response of digital PWM DC-DC converters. Generally, digital controllers are implemented using microprocessors or DSPs. Additional A/D converters are required to sense feedback signals. Proposed simple structure makes it feasible to integrate both A/D converter and digital controller on a single chip. System complexity and hardware cost are therefore greatly reduced. A behavioral time domain circuit model is proposed and analyzed using MATLAB. Both simulation and experimental results showed satisfactory performance to meet power requirements of microprocessors.

The new frequency bands that will be allocated to W-CDMA cellular networks might open the possibility to use higher bandwidths than the 5 MHz specified in 3GPP. In this paper the temporal channel properties, i.e., power delay profile, in terms of number of Rake receiver fingers and their characteristics, are analyzed for 5, 10, 20, and 30 MHz bandwidths. The lower bandwidth impulse responses are obtained by filtering measurement results obtained with a channel sounder having a bandwidth of 30 MHz.

As a lot of programs and contents such as movie files are being delivered via the Internet, and copies are often stored in distributed servers in order to reduce the load on the original servers, to ease network congestion, and to decrease response time. To retrieve an object file, existing methods simply select one or more servers. Such methods divide a file into equal pieces whose size is determined a priori. This approach is not practical for networks that offer variable bandwidth. In order to more utilize variable bandwidth, we propose an adaptive downloading method. We evaluate it by experiments conducted on the Internet. The results show that the new method is effective and that it will become an important network control technology for assurance.

ESPAR (Electronically Steerable Passive Array Radiator) antennas were proposed as candidates for low-cost analog adaptive beamforming. The radiation pattern is controlled in an azimuthal plane by variable reactors loaded on each passive element. This paper estimates the frequency bandwidth of an ESPAR antenna in a single beam scanning operation. Bandwidth in terms of gain is predicted statistically as functions of beam direction and dynamic range of variable reactance. The -3 dB bandwidth of 7-element ESPAR antennas can be about 30%, 25% and 15% for the range of reactance of -100Ω Xn 100Ω, -50Ω Xn 50Ω and -100Ω Xn 0Ω, respectively, while the improper choice of reactance sets results in narrow bandwidth less than 5%.

In an attempt to enhance the impedance bandwidth and gain, a notched patch antenna is proposed that has a pair of L-strip feeders, and it has been experimentally studied. The enhanced features were confirmed and proved by comparing the proposed antenna with the antennae that have been reported in the relevant literatures. The experimental results showed that the impedance bandwidth (SWR2) of 35.74% and the peak gain of 8.69 dBi (at 2.17 GHz) were obtained by the frequency band under 2.5 GHz. Designed originally for PCS and IMT-2000 service band, the proposed antenna, with its simple structure, may easily be mass-produced and may have various commercial applications.

A decentralized estimation system usually contains a number of remotely located local sensors that can pre-process observed signal and convey the processed data to a fusion center that makes a final estimation. The local sensors are linked to the data fusion center by transmission channels. When the observation (or estimate of parameter) is quantized at the peripheral sensors and an assumption of conditionally independent sensor data is made, due to potential communication constraints on the channels, the problem of quantization design and bandwidth allocation among the channels linking local sensors to the fusion center is studied in this letter.

In this letter, we evaluate the performance of several adaptive and non-adaptive AQM schemes for congestion control in a dynamic network environment with variable bandwidth links. The AQM schemes examined are RED, BLUE, Adaptive RED, REM, AVQ and PI controller. We compare their queueing performance and show that none of them can derive stable queue length and low packet drop rate simultaneously in networks where both input traffic and available output bandwidth are time varying. Adaptive and efficient algorithms should be designed and applied in order to improve the adaptiveness and robustness of congestion control in dynamic networks such as Internet.

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.

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.

This paper presents our experimental results in transmission of MB34 coded signal at the rate of 9.95 Gb/s over the conventional single mode fiber. The test results showed considerable improvement in receiver sensitivity, signal-to-noise-ratio (SNR), and timing margin with MB34.

In this paper, we propose a new minimum-bandwidth line code, MB810+ (MB810 plus), which is designed by statistically controlling the ASV (Alternate Sum Variation) or the DSV (Digital Sum Variation) of a line code. The proposed MB810+ retains dc-free and minimum-bandwidth characteristics, whereas it consumes only 2k gates for implementing the encoder and decoder, respectively. Therefore MB810+ can be used as a line code for high-speed data, of which speed is limited by processing delays.

A simple nation-wide core network architecture based on the optimized combination of WDM and OTDM technologies in a two-tier structure network is proposed. The dynamic timeslot allocation in a fixed length frame structure associated with the wavelength routing scheme creates a virtual path with variable bandwidth for edge-to-edge transport of any type of packet protocol without O-E-O conversion. The simulation results show that dynamic timeslot assignment with bandwidth reservation is the best alternative for the network bandwidth utilization efficiency. The influence of the delay caused by the physical size of the network during the request-acknowledgement process is also discussed.

This paper studies the optimization of signature waveforms and power allocation for synchronous code-division multiple access (CDMA) systems under the root-mean-square (RMS) bandwidth constraint. The optimization is considered for two types of receivers, namely the conventional matched filter (MF) receiver and the minimum mean-square error (MMSE) receiver. For both cases, the optimization criterion is to maximize the average signal to interference ratios (SIRs) at the receivers' outputs. For a given RMS bandwidth constraint and an arbitrary power allocation scheme, a procedure to obtain the optimal signature waveforms is provided. Based on this procedure, it is then shown that the optimal power allocation is achieved when all the received powers are equal. With the optimal power allocation, solutions for the optimal signature waveforms are presented and discussed in detail. It is also demonstrated that, compared to the previously obtained Welch-bound-equality (WBE) signature waveforms, the proposed signature waveforms can significantly improve the user performance.