IEICE Transactions on Communications
Online ISSN : 1745-1345
Print ISSN : 0916-8516
Volume E92.B, Issue 7
Displaying 1-33 of 33 articles from this issue
Regular Section
  • Jung-San LEE, Chin-Chen CHANG
    Article type: PAPER
    Subject area: Fundamental Theories for Communications
    2009 Volume E92.B Issue 7 Pages 2365-2373
    Published: July 01, 2009
    Released on J-STAGE: July 01, 2009
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    With the widespread use of Internet applications such as Teleconference, Pay-TV, Collaborate tasks, and Message services, how to construct and distribute the group session key to all group members securely is becoming and more important. Instead of adopting the point-to-point packet delivery, these emerging applications are based upon the mechanism of multicast communication, which allows the group member to communicate with multi-party efficiently. There are two main issues in the mechanism of multicast communication: Key Distribution and Scalability. The first issue is how to distribute the group session key to all group members securely. The second one is how to maintain the high performance in large network groups. Group members in conventional multicast systems have to keep numerous secret keys in databases, which makes it very inconvenient for them. Furthermore, in case that a member joins or leaves the communication group, many involved participants have to change their own secret keys to preserve the forward secrecy and the backward secrecy. We consequently propose a novel version for providing secure multicast communication in large network groups. Our proposed framework not only preserves the forward secrecy and the backward secrecy but also possesses better performance than existing alternatives. Specifically, simulation results demonstrate that our scheme is suitable for high-mobility environments.
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  • Huu Phu BUI, Yasutaka OGAWA, Toshihiko NISHIMURA, Takeo OHGANE
    Article type: PAPER
    Subject area: Fundamental Theories for Communications
    2009 Volume E92.B Issue 7 Pages 2374-2388
    Published: July 01, 2009
    Released on J-STAGE: July 01, 2009
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    In this paper, the performance of multiuser MIMO E-SDM systems in downlink transmission is evaluated in both uncorrelated and correlated time-varying fading environments. In the ideal case, using the block diagonalization scheme, inter-user interference can be completely eliminated at each user; and using the E-SDM technique for each user, optimal resource allocation can be achieved, and spatially orthogonal substreams can be obtained. Therefore, a combination of the block diagonalization scheme and the E-SDM technique applied to multiuser MIMO systems gives very good results. In realistic environments, however, due to the dynamic nature of the channel and processing delay at both the transmitter and the receiver, the channel change during the delay may cause inter-user interference even if the BD scheme is used. In addition, the change may also result in large inter-substream interference and prevent optimal resource allocation from being achieved. As a result, system performance may be degraded seriously. To overcome the problem, we propose a method of channel extrapolation to compensate for the channel change. Applying our proposed method, simulation results show that much better system performance can be obtained than the conventional case. Moreover, it also shows that the system performance in the correlated fading environments is much dependent on the antenna configuration and the angle spread from the base station to scatterers.
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  • Jyh-Horng WEN, Hsi-Chou HSU, Po-Wei CHEN
    Article type: PAPER
    Subject area: Transmission Systems and Transmission Equipment for Communications
    2009 Volume E92.B Issue 7 Pages 2389-2396
    Published: July 01, 2009
    Released on J-STAGE: July 01, 2009
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    Synchronization poses a major challenge in ultra wideband (UWB) systems due to low signal duty cycles in UWB. This study develops an effective synchronization scheme for frame-differential IR-UWB receivers to improve the synchronization speed. The proposed parallel search mechanism reduces the search region of the symbol boundaries to only a single frame duration. Moreover, only one delay element is needed in each branch, since a shared looped delay-line (SLD) is also proposed to lower the implementation complexity of the parallel search mechanism. Simulations and performance analysis show that the proposed scheme achieves a lower mean square error and a higher probability of detection than other alternatives.
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  • Sonia MAJID, Kazi AHMED
    Article type: PAPER
    Subject area: Network
    2009 Volume E92.B Issue 7 Pages 2397-2405
    Published: July 01, 2009
    Released on J-STAGE: July 01, 2009
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    A critical problem after a natural/manmade disaster is to provide immediate post-disaster communication links between the disaster victims and some overlay networks. This paper proposes a novel scheme that uses the surviving Mobile handSets (MS) as sensing nodes to form an auto-configured Hierarchical Cognitive Radio Network (H-CRN). The implementation of this H-CRN is explained through detailed problem scenario statement and step-by-step implementation of automatic identification of emergency situation by the MS nodes. An overview of the cross-layer framework used by the MS nodes is also presented. This novel scheme is tested through some hypothesis along with probability calculations for successful identification of emergency situation, formation of ad hoc group and Emergency Beacon Message (EBM) transmission.
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  • Shohei IKEDA, Hiroyuki TSUJI, Tomoaki OHTSUKI
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 7 Pages 2406-2412
    Published: July 01, 2009
    Released on J-STAGE: July 01, 2009
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    This paper proposes an indoor event detection system for homes and offices that is based on electric wave reception such as intrusion into home or office. The proposed system places antenna array on the receiver side and detects events such as intrusion using the eigenvector spanning signal subspace obtained by the antenna array. The eigenvector is based on not received signal strengths (RSS) but direction of arrival (DOA) of incident signals on the antenna array. Therefore, in a static state, the variance of the eigenvector over time is smaller than that of RSS. The eigenvector changes only when the indoor environment of interest changes intermittently and statically, or dynamically. The installation cost is low, because the detection range is wide owing to indoor reflections and diffraction of electric wave and only a pair of transmitter and receiver are used. Experimental results reveal that the proposed method can distinguish the state when no event occurs and that when an event occurs clearly. Since the proposed method has a low false detection rate, it offers higher detection rates than the systems based on RSS.
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  • Kadir TURK, Ismail KAYA
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 7 Pages 2413-2419
    Published: July 01, 2009
    Released on J-STAGE: July 01, 2009
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    An equalizer initialization technique for least mean squares (LMS) algorithm, which can equalize frequency selective multiple input multiple ozutput (MIMO) channels, is presented and analyzed. The proposed method conducts an initial convergence step for superior training prior to running the LMS algorithm. This approach raises the training performance while the complexity of the LMS algorithm, which is known as the simplest training algorithm, is almost the same. The proposed technique is analyzed for the initial convergence and simulated for a possible single carrier MIMO application in single carrier (SC) IEEE802.16-2004 standards. The obtained performance after coding approximates the performance of the recursive least squares (RLS) algorithm as it is presented for 3 × 3 and 5 × 5 MIMO for comparisons.
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  • Chin-Liang WANG, Yuan OUYANG, Ming-Yen HSU
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 7 Pages 2420-2425
    Published: July 01, 2009
    Released on J-STAGE: July 01, 2009
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    One major drawback of orthogonal frequency-division multiplexing is the high peak-to-average power ratio (PAPR) of the output signal. The selected mapping (SLM) and partial transmit sequences (PTS) methods are two promising techniques for PAPR reduction. However, to generate a set of candidate signals, these techniques need a bank of inverse fast Fourier transforms (IFFT's) and thus require high computational complexity. In this paper, we propose two low-complexity multiplication-free conversion processes to replace the IFFT's in the SLM method, where each conversion process for an N-point IFFT involves only 3N complex additions. Using these proposed conversions, we develop several new SLM schemes and a combined SLM & PTS method, in which at least half of the IFFT blocks are reduced. Computer simulation results show that, compared to the conventional methods, these new schemes have approximately the same PAPR reduction performance under the same number of candidate signals for transmission selection.
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  • Ming-Fu SUN, Terng-Yin HSU
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 7 Pages 2426-2432
    Published: July 01, 2009
    Released on J-STAGE: July 01, 2009
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    In direct-conversion orthogonal frequency division multiplexing (OFDM) receivers, the impact of frequency-dependent I/Q mismatch (IQ-M) with carrier frequency offset (CFO) must be considered. A preamble-assisted estimation is developed to circumvent the frequency-dependent IQ-M with CFO. The results of a simulation and an experiment show that the proposed method could provide good estimation efficiency and enhance the system performance. Moreover, the proposed scheme is compatible with current wireless local area network standards.
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  • Seigo NAKAO, Tomohumi TAKATA, Masaru FUKUOKA, Daichi IMAMURA, Katsuhik ...
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 7 Pages 2433-2441
    Published: July 01, 2009
    Released on J-STAGE: July 01, 2009
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    Hybrid automatic repeat request (HARQ) is employed for the Evolved Universal Terrestrial Radio Access (E-UTRA) downlink. Each user equipment (UE) sends its ACK/NACK corresponding to the downlink data reception to the base station via a physical uplink control channel (PUCCH). The ACK/NACK signals from the UE are first code spread by the cyclic shift (CS) sequences, and then code spread again by the orthogonal cover (OC) sequences. The ACK/NACK signals from each UE are multiplexed by means of code division multiple access (CDMA), however, it is difficult for the conventional PUCCH code design to satisfy the required bit error rate (BER) of 10-3 [1] in fast-fading environments because of inter-code interference (ICI) among the OC sequences. Therefore, resource management of PUCCH is required depending on the mobility of the UEs to maximize the performance of the ACK/NACK signals and the capacity of PUCCH simultaneously. In this paper, we propose a novel code design for PUCCH, which can suppress the effects of ICI among the OC sequences, and thus can simplify the resource management of PUCCH. The simulation evaluations confirm that the proposed code design can significantly improve the performance of the ACK/NACK signals via PUCCH in fast-fading environments, and any complicated resource management based on the mobility of the UEs are not necessary.
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  • Masaaki FUJII
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 7 Pages 2442-2451
    Published: July 01, 2009
    Released on J-STAGE: July 01, 2009
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    An antenna-permutation (AP) scheme is described for channel-vector quantization (CVQ) in zero-forcing beamforming (ZFBF) multiuser multiple-input and multiple-output orthogonal frequency-division multiplexing systems with multiple receive antennas. Different sets of multiple channel sub-matrices are selected for different subcarriers and then quantized to multiple quantization vectors for finite rate feedback. Based on the quantization vectors, ZFBF provides a single stream or multiple streams to users while increasing frequency selectivity. Simulation results demonstrate that AP-CVQ with four-bit quantization that incorporates with pre-whitening maximum likelihood detection for two stream reception achieved better average packet error rates than minimum mean square error receive beamforming for single stream reception when the frequency selectivity was not severe.
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  • Maduranga LIYANAGE, Iwao SASASE
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 7 Pages 2452-2460
    Published: July 01, 2009
    Released on J-STAGE: July 01, 2009
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    Kalman filters are effective channel estimators but they have the drawback of having heavy calculations when filtering needs to be done in each sample for a large number of subcarriers. In our paper we obtain the steady-state Kalman gain to estimate the channel state by utilizing the characteristics of pilot subcarriers in OFDM, and thus a larger portion of the calculation burden can be eliminated. Steady-state value is calculated by transforming the vector Kalman filtering in to scalar domain by exploiting the filter charactertics when pilot subcarriers are used for channel estimation. Kalman filters operate optimally in the steady-state condition. Therefore by avoiding the convergence period of the Kalman gain, the proposed scheme is able to perform better than the conventional method. Also, driving noise variance of the channel is difficult to obtain practical situations and accurate knowledge is important for the proper operation of the Kalman filter. Therefore, we extend our scheme to operate in the absence of the knowledge of driving noise variance by utilizing received Signal-to-Noise Ratio (SNR). Simulation results show considerable estimator performance gain can be obtained compared to the conventional Kalman filter.
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  • Tan-Hsiung HO, Wei-Jen CHEN, Shyh-Jong CHUNG
    Article type: PAPER
    Subject area: Antennas and Propagation
    2009 Volume E92.B Issue 7 Pages 2461-2467
    Published: July 01, 2009
    Released on J-STAGE: July 01, 2009
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    This paper proposes a new circuit-fed 2-D amplifying array architecture using the multi-ported aperture-coupled patch antennas. The power distribution achieved by this array is formed by stacking three kinds of basic cells repeatedly. Each cell, which serves as a radiator and also a power relay, has a multi-ported patch antenna and one or two amplifiers. The signal transmission coefficient of the cell from the input port to the output port is designed with a power level of 0dB and a phase of 360°. An X-band 4 × 3 element array with uniform amplitude distribution is demonstrated. The measured results, such as the antenna gain and the radiation patterns, agree very well with the predicted ones, due to the precision design of the basic cells. The measured gain of the antenna array is 27.7dBiA at the frequency of 10.4GHz on the H-plane, with a half-power beamwidth of 14° in the H-plane and 16° in the E-plane.
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  • Takashi MIWA, Shun OGIWARA, Yoshiki YAMAKOSHI
    Article type: PAPER
    Subject area: Sensing
    2009 Volume E92.B Issue 7 Pages 2468-2476
    Published: July 01, 2009
    Released on J-STAGE: July 01, 2009
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    Recently, it has become important to rapidly detect human subjects buried under collapsed houses, rubble and soil due to earthquakes and avalanches to reduce the casualties in a disaster. Such detection systems have already been developed as one kind of microwave displacement sensors that are based on phase difference generated by the motion of the subject's breast. Because almost all the systems consist of single transmitter and receiver pair, it is difficult to rapidly scan a wide area. In this paper, we propose a single-frequency multistatic radar system to detect breathing human subjects which exist in the area surrounded by the transmitting and receiving array. The vibrating targets can be localized by the MUSIC algorithm with the complex amplitude in the Doppler frequency. This algorithm is validated by the simulated signals synthesized with a rigorous solution of a dielectric spherical target model. We show experimental 3D localization results using a developed multistatic Doppler radar system around 250MHz.
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  • Hironori ITO, Kazunori OZAWA
    Article type: PAPER
    Subject area: Multimedia Systems for Communications
    2009 Volume E92.B Issue 7 Pages 2477-2483
    Published: July 01, 2009
    Released on J-STAGE: July 01, 2009
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    This paper proposes a method of low complexity speech mixing with speech codecs based on predictive coding for multimedia conferences. The proposed method applies a filter state management (FSM) technique to a partial mixing method in order to avoid inconsistency of the filter states of encoders. The inconsistency is created by switching of the encoders when the speakers to be mixed are switched. The results of subjective evaluations of speech quality show that the proposed method avoids the inconsistency, and achieves significantly higher speech quality than the conventional partial mixing method without the FSM and almost the same speech quality as the full mixing method. The complexity evaluation results show that the proposed method achieves much lower complexity than the full mixing method.
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  • Min-Ho JANG, Beomkyu SHIN, Woo-Myoung PARK, Jong-Seon NO, Dong-Joon SH ...
    Article type: LETTER
    Subject area: Fundamental Theories for Communications
    2009 Volume E92.B Issue 7 Pages 2484-2487
    Published: July 01, 2009
    Released on J-STAGE: July 01, 2009
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    In this letter, we analyze the convergence speed of layered decoding of block-type low-density parity-check codes and verify that the layered decoding gives faster convergence speed than the sequential decoding with randomly selected check node subsets. Also, it is shown that using more subsets than the maximum variable node degree does not improve the convergence speed.
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  • Min Li HUANG, Hyung-Joun YOO, Sin-Chong PARK
    Article type: LETTER
    Subject area: Devices/Circuits for Communications
    2009 Volume E92.B Issue 7 Pages 2488-2491
    Published: July 01, 2009
    Released on J-STAGE: July 01, 2009
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    This paper presents a reconfigurable multi-band class E power amplifier designed in CMOS technology. The proposed class E power amplifier operates efficiently over sparsely separated frequency bands by switching the capacitance of the load network. Simulation results showed a stable and high power added efficiency of 60% with 18.5dB gain, and 83% with 14.5dB gain for 2.4GHz and 5GHz WLAN applications, respectively.
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  • Chang-Hwan PARK, Yo-Han KO, Yeong-Jun KIM, Kyung-Won PARK, Won-Gi JEON ...
    Article type: LETTER
    Subject area: Transmission Systems and Transmission Equipment for Communications
    2009 Volume E92.B Issue 7 Pages 2492-2495
    Published: July 01, 2009
    Released on J-STAGE: July 01, 2009
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    In this paper, we propose a new digital duplexing scheme, called synchronous digital duplexing (SDD), which can increase data efficiency and flexibility of resource by transmitting uplink signal and downlink signal simultaneously in wireless communication. In order to transmit uplink and downlink signals simultaneously, the proposed SDD obtains mutual information among subscriber stations (SSs) with a mutual ranging symbol. This information is used for selection of transmission time, decision on cyclic suffix (CS) insertion, determination of CS length, and re-establishment of FFT starting point.
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  • SangHoon PARK, Jaeyong YOO, JongWon KIM
    Article type: LETTER
    Subject area: Network
    2009 Volume E92.B Issue 7 Pages 2496-2499
    Published: July 01, 2009
    Released on J-STAGE: July 01, 2009
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    In this letter, we propose a network-adaptive video streaming scheme based on cross-layered hop-by-hop video rate control in wireless multi-hop networks. We argue that existing end-to-end network-adaptive video rate control schemes, which utilize end-to-end statistics, exhibit serious performance degradation in severely interfered wireless network condition. To cope with this problem, in the proposed scheme, intermediate wireless nodes adjust video sending rate depending upon wireless channel condition measured at MAC (Medium Access Control) layer. Extensive experimental results from an IEEE 802.11a-based testbed show that the proposed scheme improves the perceptual video quality compared to an end-to-end scheme.
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  • Yi WAN, Takuya ASAKA, Tatsuro TAKAHASHI
    Article type: LETTER
    Subject area: Network
    2009 Volume E92.B Issue 7 Pages 2500-2502
    Published: July 01, 2009
    Released on J-STAGE: July 01, 2009
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    Searching mechanisms employed in unstructured overlay networks typically hit multiple peers for the desired content. We propose the use of a simple method that raises the hit rates of unpopular contents and balances the loads by choosing the peer holding the least contents as the provider when multiple candidates exist.
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  • Ang FENG, Qinye YIN, Jiancun FAN
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 7 Pages 2503-2506
    Published: July 01, 2009
    Released on J-STAGE: July 01, 2009
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    A single-carrier multiple-input multiple-output (MIMO) system with frequency-selective channels suffers from the inter-symbol interference (ISI) and the co-channel interference (CCI). To eliminate both type of interference, we propose in this letter a hybrid two-stage decision-feedback equalizer (HTS-DFE), which performs the frequency-domain equalization (FDE) in the first stage and the layered serial interference-cancellation (SIC) in the second stage. Since the decision-feedback (DF) or noise-prediction (NP) architecture can be employed in FDE or SIC, the proposed equalizer actually can have four variations that achieve the same mean square error (MSE) under the assumption of perfect feedback. Further, we combine HTS-DFE with the decoded decision-feedback (DDF) scheme to mitigate the error-propagation encountered in the practice. Simulation results confirm that the proposed HTS-DFE can outperform the existing equalizers significantly.
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  • Zhenzhen GAO, Shihua ZHU, Jing XU, Zhimeng ZHONG
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 7 Pages 2507-2511
    Published: July 01, 2009
    Released on J-STAGE: July 01, 2009
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    In this letter, a relay-assisted transmission scenario over frequency-selective fading channels perturbed by different random carrier frequency offsets is considered. OFDM and block-double differential (BDD) design are implemented to overcome the problem of intersymbol interference (ISI) and carrier frequency offsets (CFOs). We analyze the symbol error rate (SER) performance of decode-and-forward relaying with BDD design in wireless cooperative communications over frequency-selective fading channels and derive a theoretical upper bound for average SER when the relay (R) is error free. It can be seen from our analysis that the system performance is influenced by the ability of R to decode, and when R decodes without error, both spatial and multipath diversity can be obtained without requiring any knowledge of channel state information and CFO information at the receivers. Numerical examples are provided to corroborate our theoretical analysis.
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  • Xinzheng WANG, Ming CHEN, Pengcheng ZHU
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 7 Pages 2512-2515
    Published: July 01, 2009
    Released on J-STAGE: July 01, 2009
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    Threshold-based ordered successive interference cancellation (OSIC) detection algorithm is proposed for per-antenna-coded (PAC) two-input multiple-output (TIMO) orthogonal frequency division multiplexing (OFDM) systems. Successive interference cancellation (SIC) is performed selectively according to channel conditions. Compared with the conventional OSIC algorithm, the proposed algorithm reduces the complexity significantly with only a slight performance degradation.
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  • Ann-Chen CHANG, Shiaw-Wu CHEN
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 7 Pages 2516-2519
    Published: July 01, 2009
    Released on J-STAGE: July 01, 2009
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    This letter deals with robust interference suppression based on eigenanalysis interference canceller (EIC) with the joint code-aid and noise subspace-based correcting approach. It has been shown that the EIC is very sensitive to pointing error, especially when the interference number is overestimated. Based on the corrected steering angle, a proper blocking matrix of the EIC can be obtained to suppress the leakage of desired signal. Therefore, desired signal cancellation does not occur; even if the interference number is overestimated in constructing the interference subspace. Several computer simulations are provided to demonstrate the effectiveness of the proposed approach.
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  • Guomei ZHANG, Shihua ZHU, Shaopeng WANG, Feng LI
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 7 Pages 2520-2524
    Published: July 01, 2009
    Released on J-STAGE: July 01, 2009
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    An improved iterative minimum mean-squared error (MMSE) channel estimation method is proposed for joint coding and precoding OFDM systems. Compared with the traditional simplified estimator, the proposed scheme provides higher estimation quality with slight complexity increment at low signal-to-noise ratio (SNR) values. The performance of the iterative receiver including the proposed estimator approaches that of the perfect MMSE estimator without any simplification.
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  • Xuan GENG, Ling-ge JIANG, Chen HE
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 7 Pages 2525-2528
    Published: July 01, 2009
    Released on J-STAGE: July 01, 2009
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    A reduced complexity quantization error correction method for lattice reduction aided (LRA) vector precoding is proposed. For LRA vector precoding, Babai's approximation procedure can generate quantization errors leading to performance loss. Instead of making a list to correct all possible errors as is done in the existing scheme, we propose a novel method in which only a subset of all possible errors are corrected. The size of the subset is determined by the probability distribution of the number of actual errors. Thus, the computation complexity of our correction procedure is reduced with little performance loss compared with the existing correction scheme.
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  • Masaaki FUJII
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 7 Pages 2529-2532
    Published: July 01, 2009
    Released on J-STAGE: July 01, 2009
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    We describe a co-channel interference rejection scheme that is suitable for QR-decomposition maximum likelihood detection (MLD) in multiple-input and multiple output (MIMO) systems. A pre-whitening matrix for interference rejection is decomposed into a triangular matrix and its Hermitian matrix by using a complex Gaxpy version of the Cholesky algorithm. The decomposed triangular matrix is used as a spatial pre-filter to whiten co-channel interference. Simulation results demonstrate that the proposed scheme can suppress co-channel interference streams at the cost of receive diversity order and achieves better transmission performance than QR-decomposition MLD itself in MIMO channels with co-channel interference.
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  • Kichun CHO, Mihyun LEE, Jaeweon CHO, Hokyu CHOI, Dong Seek PARK, Seong ...
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 7 Pages 2533-2537
    Published: July 01, 2009
    Released on J-STAGE: July 01, 2009
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    IEEE802.16m standard is based on the MIMO-OFDM technology to provide high speed packet data service both in downlink and uplink. For the downlink broadcasting of control information, in order to extend the coverage of a cell, the nominal operating point should be set for the user at the edge of a cell, and no feedback should be used. For broadcasting that information, the MIMO technology should take a transmit diversity form targeted for low SNR. Several transmit diversity schemes are presented and preferable modes of operations for the broadcasting channel are proposed with numerical analysis.
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  • Seung Su HAN, Jongho PARK, Tae-Jin LEE, Hyun Gi AHN, Kyunghun JANG
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2009 Volume E92.B Issue 7 Pages 2538-2541
    Published: July 01, 2009
    Released on J-STAGE: July 01, 2009
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    Some wireless OFDMA communication systems support the frequency reuse factor of 1. In order to reduce co-channel interference (CCI) caused by neighbor cells, the fractional frequency reuse (FFR) can be employed. A promising frequency partitioning policy and subcarrier allocation for FFR are essential. In this letter, we employ an efficient frequency partitioning mechanism with less interference and propose an efficient subcarrier allocation algorithm to maximize the sum of users capacity under FFR. We show that the proposed algorithm has higher spectral efficiency than the conventional method as well as significantly high system fairness.
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  • Yeong-Jun KIM, Hyun-Il YOO, Kyung-Soo WOO, Jung-Ryun LEE, Heesoo LEE, ...
    Article type: LETTER
    Subject area: Terrestrial Radio Communications
    2009 Volume E92.B Issue 7 Pages 2542-2545
    Published: July 01, 2009
    Released on J-STAGE: July 01, 2009
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    In a cellular system, efficient power saving techniques for a mobile station (MS) are necessary because of its inherently limited battery capacity. The paging indicator (PI) transmission scheme in CDMA cellular systems is known to be an effective power saving strategy. However, in OFDM-based cellular systems, the MS has to operate FFT for PI symbol detection, resulting in a significant power consumption. In this letter, a PI transmission technique with reduced power consumption using the preamble in OFDM-based cellular systems, especially for mobile WiMAX systems, is proposed for the MS under power saving mode. Simulations indicate a 30-50% power saving from our proposed PI transmission technique, at the expense of a slight increase in paging response delay.
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  • Young Kil KWAG
    Article type: LETTER
    Subject area: Antennas and Propagation
    2009 Volume E92.B Issue 7 Pages 2546-2549
    Published: July 01, 2009
    Released on J-STAGE: July 01, 2009
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    This letter proposes a high-performance single-sided horn-shaped tapered bowtie antenna which is compact and covers more than the whole UWB frequency band. This design implements a bowtie radiating element and tapered strip-line feeder element on a single-sided dielectric substrate, which offers a measured return loss of less than -10dB over the whole UWB frequency band of 3.0-10.8GHz. The measured radiation pattern is bi-directional with consistent gain over the above frequency band. This compact-size design shows much enhanced performance, compared to the previously reported antenna, which is useful for UWB radar and communication applications.
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  • Jong Hwa KWON, Jong Gwan YOOK
    Article type: LETTER
    Subject area: Electromagnetic Compatibility (EMC)
    2009 Volume E92.B Issue 7 Pages 2550-2553
    Published: July 01, 2009
    Released on J-STAGE: July 01, 2009
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    In this paper, a novel method of partially placing electromagnetic band-gap (EBG) unit cells on both the power and ground planes in multi-layer PCBs and packages is proposed; it can not only sufficiently eliminate simultaneous switching noise (SSN), but also prevent severe degradation of signal quality in high-speed systems with imperfect reference planes resulting from the perforated structures of uni-planar EBG unit cells. On the assumption that the noise sources and noise-sensitive devices exist only in specific areas, the proposed method partially arranges the EBG unit cells on both the power and ground planes, but only around the critical areas. The SSN suppression performance of the proposed structure is verified by a simulation and measurements.
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