This paper proposes a new blind algorithm effective for multiuser detection with an adaptive array antenna. The conventional blind algorithm, known as the Constant Modulus Algorithm (CMA), has two major drawbacks: (i) the convergence speed is not sufficiently fast for usual applications in mobile communications, and (ii) the algorithm is very likely to lock on the path with the largest received power, which means the signal with the second largest power can hardly be extracted. This paper introduces the Recursive Least Squares algorithm for CMA (RLS-CMA) in order to speed the convergence up, and additionally introduces the concept of the orthogonal projection into CMA so as to extract signals with weak power. The proposed CMA with Orthogonal Projection (CMA-OP) sequentially calculates the weight vector of each user under a constraint that the weight vector should be orthogonal to the estimated array response vectors of previously extracted users. Computer simulations demonstrate that the proposed scheme can operate properly in the Rayleigh fading channels under the two-user condition.

The adaptive base station antenna is an attractive candidate for establishing high-speed and highly-reliable wireless communication systems. From a commercial viewpoint, since the cost and complexity of adaptive antennas depend on the number of elements, optimizing the antenna configuration while considering the propagation environment is necessary to reduce the number of elements. This paper first presents the Angle of Arrival (AOA) characteristics of delayed waves in a street microcell environment, typically used in urban microcell systems. Then the antenna configuration and antenna spacing suitable for the street microcell are investigated utilizing bit error rate (BER) performance simulations using practical delay profiles and AOAs. The effectiveness of bidirectional elements with respect to the BER performance is also investigated. As the results, we found that broadside array with the spacing of 2.5 wavelengths is suitable for adaptive base station antennas for high data-rate wireless systems placed in a street microcell environment. We also found that bidirectional elements alleviate the BER degradation due to the grating lobe of the antenna with wide element spacing without increasing the antenna size.

In this paper, a novel chrominance up-sampling algorithm for color post-processing is described. This scheme exploits so-called inter-chrominance coherence, i.e., luminance and chrominance signals share the same structural information. Usually luminance has higher spatial resolution than chrominance in compression coding standards. So the idea is to up-sample chrominance signals using the structural information extracted from the luminance.

Randomly addressed polling was proposed as a multiple access control protocol for wireless local area networks (LANs). However, the protocol has difficulties in supporting real-time services such as voice transmission. We propose a reservation scheme and make it possible to support real-time services. The scheme is described in detail. Efficiency and average access delay are analyzed.

We investigated single flux quantum sinc filters with multistage decimation structure in order to realize high-speed sinc filter operation. Second- and third-order (k=2, 3) sinc filters with a decimation factor N=2 were designed and confirmed their proper operations. These sinc filters with N=2 are utilized as elementary circuit blocks of our multistage decimation sinc filters with N=2M, where M indicates the number of the stage of the decimation. As an example of the multistage decimation filter, we designed a k=2, N=4 sinc filter which was formed from a two-stage decimation structure using k=2, N=2 sinc filters, and confirmed its proper operation. The k=2, N=4 sinc filter consisted of 1372 Josephson junctions with the power consumption of 191 µW.

Batch verification is a useful tool in verifying a large number of cryptographic items all at one time. It is especially effective in verifying predicates based on modular exponentiation. In some cases, however the items can be incorrect although they pass batch verification together. Such leniency can be eliminated by checking the domain of each item in advance. With this in mind, we introduce the strict batch verification and investigate if the strict batch verification can remain more effective than separate verification. In this paper, we estimate the efficiency of such strict batch verification in several types of groups, a prime subgroup of Zp with special/random prime p and prime subgroups defined on elliptic curves over Fp, F2m and Fpm, with are often used in DL-based cryptographic primitives. Our analysis concludes that the efficiency differs greatly depending on the choice of the group and parameters determined by the verifying predicate. Furthermore, we even show that there are some cases where batch verification, regardless of strictness, loses its computational advantage.

This paper proposes a new algorithm to achieve about two-times speedup of modular exponentiation which is implemented by Montgomery multiplication based on Residue Number Systems (RNS). In RNS Montgomery multiplication, its performance is determined by two base transformations dominantly. For the purpose of realizing parallel processing of these base transformations, i. e. "duplicate processing," we present two procedures of RNS Montgomery multiplication, in which RNS bases a and b are interchanged, and perform them alternately in modular exponentiation iteration. In an investigation of implementation, 1.87-times speedup has been obtained for 1024-bit modular multiplication. The proposed RNS Montgomery multiplication algorithm has an advantage in achieving the performance corresponding to that the upper limit of the number of parallel processing units is doubled.

Array antennas are employed at the receiver for a variety of purposes such as to combat fading or to reduce co-channel interference. To evaluate the performance of a wireless communications system using antenna arrays it becomes necessary to have spatial channel models that describe the Angle of Arrival (AOA), Time of Arrival (TOA) and the Angle Spread (AS) of the multipath components. Among the most widely used radio propagation models is the single bounce scattering geometric model, where propagation between the transmitting and receiving antennas is assumed to take place via single scattering from an intervening obstacle. Currently, several geometric models are available such as circular and elliptical scattering models, with each model being applicable to a specific environment type. This paper addresses the modeling, simulation and evaluation of the angle spread in smart antenna systems taking into account the Gaussian density model, and proves that the model finds use both in a micro cell as well as in a macro cell environment. Moreover, we show statistics for the angle and time of arrival.

This paper presents a beamspace-time transmit diversity scheme that uses a space-time block code (STBC) and a fixed multi-beam transmit array with low sidelobes for time-domain spreading orthogonal frequency-division multiplexing code-division multiplexing (OFDM-CDM) downlink transmission. The scheme assigns space-time-coded signals to a pair of neighboring beams via closed-loop beam selection. Time-domain spreading provides non-frequency selectivity in each spreading region, which makes it possible for multiple STBCs to share any beam and to be decoded after despreading. Simulation results demonstrated that multiple transmit beams and multiple receive antennas provide large beam gains and/or a high order of diversity gains. In addition, the proposed scheme spatially separates users by beam and thus alleviates multi-user interference.

This paper proposes a symbol-by-symbol-based multilevel transmit power control (MTPC) scheme for orthogonal frequency division multiplexing (OFDM) based adaptive modulation system (AMS) to achieve high quality broadband wireless transmission for high mobility terminals. In the proposed system, delay profile for each OFDM symbol is estimated by linearly extrapolating previously received delay profile information (DPI) sequence to improve tracking ability of OFDM based AMS with MTPC to the fast fading variation. Moreover, 2-branch reception diversity is applied to reduce dynamic range and variation speed of the multipath fading. Computer simulation confirms that the proposed system is effective in supporting higher mobility terminals with keeping high transmission quality.

A key problem under imperfect power control in multimedia DS-CDMA networks is how to guarantee the differentiated outage probabilities of different traffic classes resulted from the uncertainty of received powers. In addition, in order to utilize the scarce wireless resource efficiently, as many users as possible should be admitted into the network while providing guaranteed quality-of-service support for them. In this work, a call admission control scheme, Differentiated Outage Probabilities CAC or DOP-CAC, is proposed to achieve the above goals for imperfectly power-controlled multimedia CDMA networks. Two important features of CDMA systems are considered in our scheme: one is the power multiplexing among bursty traffics and the other is the power allocation scheme employed at the physical layer. The validity and efficiency of DOP-CAC are verified by numerical examples. Two power allocation schemes, Limited Optimal Power Allocation (LOPA) proposed in [3] and Quasi-Optimal Power Allocation (QOPA) we proposed in [6], are considered respectively and compared in the performance evaluation of DOP-CAC. The results show that DOP-CAC achieves much better resource utilization under QOPA than it does under LOPA. By employing QOPA at the physical layer and DOP-CAC at the link layer, our work suggests a high efficiency solution for QoS support of multimedia traffic under imperfect power control environment.

Many services on ITS (Intelligent transport system) have been proposed, which include the ETC (electronic toll collection) system. In this paper, we first present some assumptions we can assume on ITS. Then we construct a light electronic ticket system which is suitable for payment on ITS. In our system, (1) only two moves are required to use a ticket, (2) the shop can check the validity of the ticket with only a few applying of hash functions. Further, we prove that forgery of a ticket by a user or a shop is detected with almost one probability.

This paper proposes a multipath interference canceller (MPIC) employing multipath interference (MPI) replica generation (MIG) utilizing previously transmitted packet combining (PTPC), which is well-suited to incremental redundancy, in order to achieve a peak throughput of nearly 8 Mbps in a multipath fading environment in high-speed downlink packet access (HSDPA). In our scheme, more accurate MPI replica generation is possible by generating MPI replicas utilizing the soft-decision symbol sequence of the previously transmitted packets in addition to that of the latest transmitted packet. Computer simulation results elucidate that the achievable throughput of the MPIC employing MIG-PTPC is increased by approximately 100 kbps and 200 kbps and the required average received signal energy per symbol-to-background noise power spectrum density ratio (Es/N0) per antenna at the throughput of 0.8 normalized by the maximum throughput is improved by about 0.3 and 0.7 dB compared to that of the MPIC using the soft-decision symbol sequence after Rake combining of the last transmitted packet both in 2- and 3-path Rayleigh fading channels for QPSK and 16QAM data modulations, respectively. Furthermore, we clarify that the maximum peak throughput using the proposed MPIC with MIG-PTPC coupled with incremental redundancy achieves approximately 7 Mbps and 8 Mbps with 16QAM and 64QAM data modulations in a 2-path Rayleigh fading channel, respectively, within a 5-MHz bandwidth.

This paper presents laboratory and field experimental results of the coherent adaptive antenna array diversity (CAAAD) receiver employing receiver antenna-weight generation common to all Rake-combined paths (hereafter path-common weight generation method) in the W-CDMA reverse link, in order to elucidate the suitability of the path-common weight generation method in high-elevation antenna environments such as cellular systems with a macrocell configuration. Laboratory experiments using multipath fading simulators and RF phase shifters elucidate that even when the ratio of the target Eb/I0 of the desired to interfering users is Δ Eb/I0=-12 dB, the increase in the average transmit Eb/N0 employing the CAAAD receiver coupled with fast transmission power control (TPC) using outer-loop control from that for Δ Eb/I0=0 dB is within only 1.0 dB owing to the accurate beam and null steering associated with fast TPC. Furthermore, field experiments demonstrate that the required transmission power at the average block error rate (BLER) of 10-2 employing the CAAAD receiver with four antennas is reduced by more than 2 dB compared to that using a four-branch space diversity receiver using maximum ratio combining (MRC) with the fading correlation between antennas of 0 when Δ Eb/I0=-15 dB and that the loss in the required transmission power of the CAAAD receiver in the same situation as that in a single-user environment is approximately 1 dB. The field experimental results in an actual propagation environment suggest that the CAAAD receiver is effective in suppressing multiple access interference, thus decreasing the required transmission power when the gap in the direction of arrival between the desired user and interfering users is greater than approximately 20 degrees.

This paper investigates transmission power control for packet transmissions by using code division multiplexing (CDM) in the downlink common (shared) channel of CDMA cellular packet systems and proposes a transmission power control scheme to improve throughput performance and geographical fairness of communication services. In the proposed scheme, downlink transmission power is controlled based on the signal-to-interference ratio predicted at mobile stations. Throughput performance and transmission delay are evaluated under perfect power control conditions. Simulation results show that by using site diversity technique the proposed scheme improves the downlink throughput for light load conditions and geographical fairness for all offered channel loads under both non-fading and fading environments.

This paper proposes an Orthogonal Frequency Division Multiplexing system with Grouping Adaptive Modulation method (GAM-OFDM). The salient feature of the proposed system is to enable the reduction of required transmission bits for adaptive modulation information (AMI) that is required in the demodulation process at the receiver. This paper also proposes an efficient AMI transmission method for the GAM-OFDM system to enable the efficient transmission of AMI bits by using only two preamble symbols, and the Multi-Carrier Spectrum Spreading (MC-SS) technique to achieve the excellent performance of AMI transmission even under severe multi-path fading environments. This paper presents the various computer simulation results to verify the performance of proposed GAM-OFDM system.

We propose a new multiple access communication system based on finite field wavelet spread signature (FFWSS). In addition to the function of frequency diversity and multiple access, which are typically provided by traditional spreading codes, the FFWSS spreads data symbols in time, resulting in robustness against frequency selective slow fading. Using the FFWSS to spread a data symbol so that it is overlapped with neighboring symbols, a FFWSS-CDMA system is developed. It is observed that the ratio of the maximum nontrivial value of periodic correlation function to the code length of FFWSS is the same as that of a Sidelnikov sequence. Using RAKE-based receivers, simulation results show that the proposed FFWSS-CDMA system yields lower bit error rate (BER) than conventional DS-CDMA and MT-CDMA systems in multipath fading channels.

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.

In this paper, two types of multi-stage partial parallel interference cancellation (PIC) receivers are considered for multi-rate DS-CDMA system: multi-stage PIC receiver with partial cancellation factors and multi-stage PIC receiver with decision thresholds. Bit error rate (BER) of the multi-stage partial PIC receivers is obtained by simulation in a Rayleigh fading channel. It is shown that the multi-stage partial PIC receivers achieve smaller BER than the matched filter (MF) receiver, multi-stage PIC receiver, group-wise successive interference cancellation (GSIC) receiver, and extended GSIC receiver (EGSIC) for the multi-rate DS-CDMA system in a Rayleigh fading channel.

Due to saturable nature of gain or absorption of Er doped fiber, a dynamic grating is formed by standing wave produced by interference between two laser beams traveling in opposite directions in the fiber. In this letter, we propose a variable optical filter using the dynamic grating in Er doped fiber controlled by synthesis of optical coherence function. Simulations and experimental verifications are also shown.