IEICE Transactions on Communications
Online ISSN : 1745-1345
Print ISSN : 0916-8516
Volume E95.B, Issue 11
Displaying 1-44 of 44 articles from this issue
Special Section on Satellite Communication Technologies in Conjunction with Main Topics of JC-SAT2011
  • Nei KATO
    2012 Volume E95.B Issue 11 Pages 3377
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
    JOURNAL FREE ACCESS
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  • Naoto KADOWAKI, Takashi TAKAHASHI, Maki AKIOKA, Yoshiyuki FUJINO, Mori ...
    Article type: INVITED PAPER
    2012 Volume E95.B Issue 11 Pages 3378-3384
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    It is well known that satellite communications systems are effective and essential communication infrastructure for disaster relief. NICT sent researchers to Tsunami stricken area in March right after the Great East Japan Earthquake and provided broadband satellite communications link to support rescue activities. Through this experience, we learned many kinds of requirements of communications for such purposes. In this paper, we list up the requirements and report what kind of satellite communications technologies are needed, and research and development issues.
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  • Weixiao MENG, Enxiao LIU, Shuai HAN, Qiyue YU
    Article type: INVITED PAPER
    2012 Volume E95.B Issue 11 Pages 3385-3392
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    With the development of Global Navigation Satellite System (GNSS), the amount of related research is growing rapidly in China. A lot of accomplishments have been achieved in all branches of the satellite navigation field, especially motivated by the BeiDou Program. In this paper, the current status, technologies and developments in satellite positioning and navigation in China are introduced. Firstly, an overview and update of the BeiDou Program is presented, known as the three-step development strategy for different services. Then signal design for the BeiDou system is discussed, including the generation of pseudo-random noise (PRN) codes for currently available signal B1, and the investigation of a new signal modulation scheme for interoperability at open frequency B1C. The B1C signal should comply to Multiplexed Binary Offset Carrier (MBOC) constrains, and a modulation called Quadrature Multiplexed BOC (QMBOC) is presented, which is equivalent to time-multiplexed BOC (TMBOC) for GPS and composite BOC (CBOC) for Galileo, while overcomes the drawback of CBOC. Besides, the inter and intra system compatibility is discussed, based on the effective (C/N0) proposed by International Telecommunication Union (ITU). After that, receiver technologies in challenging environments are introduced, such as weak signal acquisition and assisted GNSS (A-GNSS). Moreover, a method of ambiguity mitigation for adaptive digital beam forming (ADBF) in large spacing antenna arrays is proposed, by which interference suppression is available. Furthermore, cutting edge technologies are brought in, including seamless navigation for indoor and outdoor, and collaborative navigation. After all, GNSS applications in China for industry and daily life are shown, as well as the market prospection.
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  • Katsuya NAKAHIRA, Jun-ichi ABE, Jun MASHINO, Takatoshi SUGIYAMA
    Article type: PAPER
    2012 Volume E95.B Issue 11 Pages 3393-3403
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    This paper proposes a new channel allocation algorithm for satellite communication systems. The algorithm is based on a spectrum division transmission technique as well as a spectrum compression transmission technique that we have developed in separate pieces of work. Using these techniques, the algorithm optimizes the spectrum bandwidth and a MODCOD (modulation and FEC error coding rate) scheme to balance the usable amount of satellite transponder bandwidth and satellite transmission power. Moreover, it determines the center frequency and bandwidth of each divided subspectra depending on the unused bandwidth of the satellite transponder bandwidth. As a result, the proposed algorithm enables flexible and effective usage of satellite resources (bandwidth and power) in channel allocations and thus enhances satellite communication (SATCOM) system capacity.
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  • Akira AKAISHI, Takashi TAKAHASHI, Yoshiyuki FUJINO, Mitsugu OHKAWA, To ...
    Article type: PAPER
    2012 Volume E95.B Issue 11 Pages 3404-3411
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    NICT has developed a test model of an optically controlled beam-forming network (OBF) for a future multiple-beam antenna. The OBF test model consists of an electro-optic converter unit, an OBF unit, and an optoelectronic converter unit. A Ka-band OBF test model was manufactured to demonstrate the OBF. Radiation patterns obtained from the measured OBF data confirmed agreement between the expected and calculated results. Communication tests of the bit error rate (BER) for the digital communication link were performed. The results confirmed the OBF had no serious degradation below 1dB of Eb/N0 on BER performance at 1×10-8.
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  • Yoshinori SUZUKI, Takatoshi SUGIYAMA, Kiyoshi KOBAYASHI
    Article type: PAPER
    2012 Volume E95.B Issue 11 Pages 3412-3419
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    This paper proposes an On-Ground Polarization-Forming (GPF) technique to realize a novel polarization-tracking-free satellite communication system whose communication satellite uses linear polarizations. In this system, mobile terminals use circular polarization to realize polarization-tracking-free and simplified terminal configuration. To output circular polarization from the satellite's horizontal and vertical polarization antennas, those output signals transmitted from the satellite are controlled by the base station using the GPF technique. We fabricate a GPF transmitter to evaluate its polarization forming performance. Measured results show that the proposed technique achieves very high cross-polarization discrimination, more than 27dB.
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  • Takehiro ISHIGURO, Takao HARA, Minoru OKADA
    Article type: PAPER
    2012 Volume E95.B Issue 11 Pages 3420-3427
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    For effective use of the frequency band, carrier superposing (common band) technique has been introduced to satellite communication systems. On the other hand, satellite's TWTA (Traveling Wave Tube Amplifier) should be operated near its saturation level for power efficiency. However, the TWTA nonlinearity characteristics around that level causes interference in carrier superposing systems. Therefore in this paper, a post-compensation technique for TWTA nonlinear distortion is introduced and verified for practical use in a carrier superposed Point to Point satellite communication system which adopts interference canceller. Simulation results show that it is possible to reduce the bit error rate degradation over the entire range, especially at nonlinear operating point.
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  • Ken HARIMA, Hirobumi SAITO, Takuji EBINUMA
    Article type: LETTER
    2012 Volume E95.B Issue 11 Pages 3428-3431
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    On rocket-borne GPS receivers, the high dynamics make the use of PLL is impractical and a FLL is used. This in turn leads to a string of errors on the demodulated navigation message. The present paper proposes two decoding algorithms for GPS navigation messages suited for strings of errors. The first philosophy uses parity check syndromes to correct demodulation errors. The second philosophy uses Log Correlation Ratio (LCR) comparison along with parity check syndromes to correct for the most probable error pattern. GPS data availability can be significantly improved by using the latter.
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Regular Section
  • Jangwoo PARK, Youngsun HA, Wonzoo CHUNG
    Article type: PAPER
    Subject area: Fundamental Theories for Communications
    2012 Volume E95.B Issue 11 Pages 3432-3436
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    We propose a reduced complexity maximum likelihood sequence detection (MLSD) equalizer for wireless communications using bidirectional decision feedback equalizers (DFEs). We apply reduced-length two-level estimates produced by a bidirectional DFE. Therefore, the computationally expensive MLSD algorithm is applied sparingly for two-level signals with the effective channel length shorter than the original channel, regardless of the original constellation size of the symbols. Simulation results show that the proposed algorithm outperforms existing combination schemes based on bidirectional DFEs, especially for large constellations.
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  • Masashi KONO, Akihiro KANBE, Hidehiro TOYODA, Shinji NISHIMURA
    Article type: PAPER
    Subject area: Transmission Systems and Transmission Equipment for Communications
    2012 Volume E95.B Issue 11 Pages 3437-3444
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    A novel 400-Gb/s (100-Gb/s × 4) physical-layer architecture for the next-generation Ethernet — using 100-Gb/s serial (optical single-wavelength) transmission — is proposed. As for the next-generation 400-Gb/s Ethernet, additional requirements from the market, such as power reduction and further miniaturization in addition to attaining even higher transmission speed, must be satisfied. To satisfy these requirements, a 100-Gb/s×4 Ethernet physical-layer architecture is proposed. This architecture uses a 100-Gb/s serial (optical single-wavelength) transmission Ethernet and low-power technologies for a multi-lane transmission Ethernet. These technologies are implemented on a 100-Gb/s serial (optical single wavelength) transmission Ethernet using field-programmable gate arrays (FPGAs). Experimental evaluation of this implementation demonstrates the feasibility of low-power 400-Gb/s Ethernet.
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  • Shoichiro MATSUMOTO, Koji KAMAKURA
    Article type: PAPER
    Subject area: Optical Fiber for Communications
    2012 Volume E95.B Issue 11 Pages 3445-3455
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    We propose an interference avoidance architecture using uneven spreading as a media access mechanism for optical code division multiple access (OCDMA). While an equal-intensity pulse sequence encoded with the spreading sequence assigned to each node is transmitted for a “1”bit in conventional OCDMA with on-off keying (OOK), the proposed architecture creates an uneven-intensity pulse sequence where one of the pulses has higher intensity than the others. The high-intensity pulse allows source nodes to use increased sensing threshold for channel sensing, which leads to an increase in the number of chip offsets available for collision-free transmission. Our receiver with a hard limiter (HL) allows destination nodes to receive the transmission without false positives. Interference avoidance performance is examined by deriving the collision probability and comparing it with the conventional interference avoidance with equal-intensity spreading. Our numerical results show that our architecture has lower collision probability, shorter time required for channel sensing, higher throughput, higher bit rate, and supports more nodes than the conventional one for a fixed collision probability.
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  • Nagao OGINO, Takuya OMI, Hajime NAKAMURA
    Article type: PAPER
    Subject area: Network
    2012 Volume E95.B Issue 11 Pages 3456-3463
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    Secret sharing schemes have been proposed to protect content by dividing it into many pieces securely and distributing them over different locations. Secret sharing schemes can also be used for the secure delivery of content. The original content cannot be reconstructed by the attacker if the attacker cannot eavesdrop on all the pieces delivered from multiple content servers. This paper aims to obtain secure delivery routes for the pieces, which minimizes the probability that all the pieces can be stolen on the links composing the delivery routes. Although such a route optimization problem can be formulated using an ILP (Integer Linear Programming) model, optimum route computation based on the ILP model requires large amounts of computational resources. Thus, this paper proposes a lightweight route computation method for obtaining suboptimum delivery routes that achieve a sufficiently small probability of all the pieces being stolen. The proposed method computes the delivery routes successively by using the conventional shortest route algorithm repeatedly. The distance of the links accommodating the routes that have already been calculated is adjusted iteratively and utilized for calculation of the new shortest route. The results of a performance evaluation clarify that sufficiently optimum routes can be computed instantly even in practical large-scale networks by the proposed method, which adjusts the link distance strictly based on the risk level at the considered link.
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  • HyunYong LEE, Akihiro NAKAO
    Article type: PAPER
    Subject area: Network
    2012 Volume E95.B Issue 11 Pages 3464-3471
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    In this paper, we examine a new P2P traffic localization approach that exploits peer selection adaptation (i.e., preferring peers who are likely to provide better performance), called Netpherd. Netpherd enables peers to communicate with local domain peers by manipulating networking performance across network domains (i.e., adding an artificial delay to inter-domain traffic). Our feasibility study shows that Netpherd reduces the inter-domain traffic by influencing peer selection adaptation. Netpherd also improves download performance of the peers who know many local domain peers. We discuss one guideline to improve Netpherd based on the feasibility study and verify the guideline with evaluation results.
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  • I Putu Agung BAYUPATI, Yoshiya KASAHARA, Yoshitaka GOTO
    Article type: PAPER
    Subject area: Antennas and Propagation
    2012 Volume E95.B Issue 11 Pages 3472-3479
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    When the Akebono (EXOS-D) satellite passed through the plasmasphere, a series of lightning whistlers was observed by its analog wideband receiver (WBA). Recently, we developed an intelligent algorithm to detect lightning whistlers from WBA data. In this study, we analyzed two typical events representing the clear dispersion characteristics of lightning whistlers along the trajectory of Akebono. The event on March 20, 1991 was observed at latitudes ranging from 47.83° (47,83°N) to -11.09° (11.09°S) and altitudes between ∼2232 and ∼7537km. The other event on July 12, 1989 was observed at latitudes from 34.94° (34.94°N) and -41.89° (41.89°S) and altitudes ∼1420-∼7911km. These events show systematic trends; hence, we can easily determine whether the wave packets of lightning whistlers originated from lightning strikes in the northern or the southern hemispheres. Finally, we approximated the path lengths of these lightning whistlers from the source to the observation points along the Akebono trajectory. In the calculations, we assumed the dipole model as a geomagnetic field and two types of simple electron density profiles in which the electron density is inversely proportional to the cube of the geocentric distance. By scrutinizing the dipole model we propose some models of dispersion characteristic that proportional to the electron density. It was demonstrated that the dispersion D theoretically agrees with observed dispersion trend. While our current estimation is simple, it shows that the difference between our estimation and observation data is mainly due to the electron density profile. Furthermore, the dispersion analysis of lightning whistlers is a useful technique for reconstructing the electron density profile in the Earth's plasmasphere.
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  • Huan-Chun WANG, De-Jhen HUANG
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2012 Volume E95.B Issue 11 Pages 3480-3491
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    This paper proposes a low-complexity concatenated (LCC) soft-in soft-out (SISO) detector for spreading OFDM systems. The LCC SISO detector uses the turbo principle to compute the extrinsic information of the optimal maximum a priori probability (MAP) SISO detector with extremely low complexity. To develop the LCC SISO detector, we first partition the spreading matrix into some concatenated sparse matrices separated by interleavers. Then, we use the turbo principle to concatenate some SISO detectors, which are separated by de-interleavers or interleavers. Each SISO detector computes the soft information for each sparse matrix. By exchanging the soft information between the SISO detectors, we find the extrinsic information of the MAP SISO detector with extremely low complexity. Simulation results show that using the LCC SISO detector produces a near-optimal performance for both uncoded and coded spreading OFDM systems. In addition, by using the LCC SISO detector, the spreading OFDM system significantly improves the BER of the conventional OFDM system.
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  • Jinyong LEE, Younglok KIM
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2012 Volume E95.B Issue 11 Pages 3492-3497
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    In orthogonal frequency division multiplexing (OFDM) based systems, intercarrier interference (ICI) created by the time varying property of wireless fading channels, degrades the data detection performance. This degradation strengthens especially when the mobile speed is relatively high or the number of subcarriers is large. Here, we interpret the time varying channel as the linear transformation of the time invariant channel impulse response. By using this new channel model, the time varying component can be reduced in the time domain by applying the inverse transformation to the received sequence. Then, the remaining time invariant channel component is removed by the equalization in the frequency domain. Some complexity reduction schemes are also proposed to make the proposed method feasible for practical implementation. The simulation results show that the new method offers a significant improvement in terms of bit error rate performance, especially when the number of subcarriers is larger than about 500.
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  • Minjee KIM, Gia Khanh TRAN, Kei SAKAGUCHI, Kiyomichi ARAKI
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2012 Volume E95.B Issue 11 Pages 3498-3508
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    MIMO-OFDM combining OFDM and MIMO techniques achieves high spectral efficiency and is able to increase throughput. MIMO-OFDM systems can be classified into either “open loop” or “closed loop” depending on whether the CSI is fed back from the Rx to the Tx. As a closed loop scheme, SVD-MIMO is the optimal single user MIMO-OFDM transmission scheme while it requires knowledge of the CSI at both the Tx and Rx. In practical systems, Tx weight is fed back from the Rx to the Tx by limited bits and with feedback delay, which causes mismatch between the weight and the real channel especially if the channel exhibits time variation. Hence, the transmission performance of the SVD-MIMO scheme degrades. Therefore, the performance comparison between open loop and closed loop schemes against channel variation is very important for practical deployment of MIMO-OFDM systems. For that purpose, a unified performance calculation method for the open loop and the closed loop MIMO-OFDM schemes with finite and delayed feedback is developed in this paper. The method is effective for analysis of both STBC for the open loop and SVD-MIMO using codebook for the closed loop with per stream layer AMC. Also, to combat frequency selective fading in practical wireless channels, an interleaver is employed in this paper. In numerical analyses, it is found that simulation results agree well with the derived theoretical performance results. Secondly, from these results, the cross-over point of the throughput performance of two schemes in terms of UE velocity and SNR is found.
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  • Hsin-De LIN, Tzu-Hsien SANG, Jiunn-Tsair CHEN
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2012 Volume E95.B Issue 11 Pages 3509-3518
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    For advanced mobile communication systems that adopt orthogonal frequency-division multiple access (OFDMA) technologies, intercarrier interference (ICI) significantly degrades performance when mobility is high. Standard specifications and concerns about complexity demand low-cost methods with deployment readiness and decent performance. In this paper, novel zero forcing (ZF) and minimum mean-square error (MMSE) equalizers based on per-subcarrier adaptive (PSA) processing and perturbation-based (PB) approximation are introduced. The proposed equalizers strike a good balance between implementation cost and performance; therefore they are especially suitable for OFDMA downlink receivers. Theoretical analysis and simulations are provided to verify our claims.
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  • Kyujin LEE, Dongho CHA, Kyesan LEE
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2012 Volume E95.B Issue 11 Pages 3519-3526
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    MIMO-OFDM systems are widely used in next generation wireless communications due to their high data rates, spatial division multiplexing, and robustness against channel fading. Moreover, multimedia video service is developing very quickly, as are service demands. Consequently, in order to satisfy these demands, we use a MIMO-OFDM system with SDM characteristic to transmit Scalable Video Coding (SVC) signals; our approach maximizes throughput and greatly improves video quality. We propose an Unequal Antenna Power Allocation (UAPA) scheme to improve system performance by increasing the PSNR compared to that of conventional equal power transmission systems and to efficiently utilize the power. We evaluate the performance of the proposed scheme using simulations. The results show that the proposed system provides superior performance compared to conventional systems.
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  • Tomoaki TAKEUCHI, Hiroyuki HAMAZUMI, Kazuhiko SHIBUYA
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2012 Volume E95.B Issue 11 Pages 3527-3535
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    As many digital terrestrial broadcasting stations have been installed and are now broadcasting, the problem of poor reception has become serious even though the receiving powers are high. Although we had developed a interference canceller for broadcast-wave relay stations, an adaptive array is desirable to be more robust against low-D/U multipath environment as a receiver for the service area. In this paper, we propose a weighting coefficient optimization algorithm for post-FFT adaptive array using the reciprocals of weighting coefficients. Numerical examples show the effectiveness of the proposed method.
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  • Jaehyun PARK, Yunju PARK, Sunghyun HWANG, Byung Jang JEONG
    Article type: PAPER
    Subject area: Terrestrial Wireless Communication/Broadcasting Technologies
    2012 Volume E95.B Issue 11 Pages 3536-3544
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    In this paper, low-complexity generalized singular value decomposition (GSVD) based beamforming schemes are proposed for a cognitive radio (CR) network in which multiple secondary users (SUs) with multiple antennas coexist with multiple primary users (PUs). In general, optimal beamforming, which suppresses the interference caused at PUs to below a certain threshold and maximizes the signal-to-interference-plus-noise ratios (SINRs) of multiple SUs simultaneously, requires a complicated iterative optimization process. To overcome the computational complexity, we introduce a signal-to-leakage-plus-noise ratio (SLNR) maximizing beamforming scheme in which the weight can be obtained by using the GSVD algorithm, and does not require any iterations or matrix squaring operations. Here, to satisfy the leakage constraints at PUs, two linear methods, zero forcing (ZF) preprocessing and power allocation, are proposed.
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  • Jing MA, Hiroo SEKIYA, Atsushi NAGASAKI, Nobuyoshi KOMURO, Shiro SAKAT ...
    Article type: PAPER
    Subject area: Terrestrial Wireless Communication/Broadcasting Technologies
    2012 Volume E95.B Issue 11 Pages 3545-3555
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    We herein propose a MAC protocol for the smart antenna network, which applies pulse/tone exchange prior to the RTS/CTS handshake process. RTS frame collisions are drastically reduced with little additional overhead due to pulse/tone exchange in the proposed protocol. In addition, the number of exposed nodes is reduced by using smart antennas. Furthermore, since the occurrence of the deafness problem can be identified by pulse/tone exchange failure, retransmission is conducted using a fixed contention window value. Therefore, the wastage of wireless resources due to the deafness problem is reduced. As a result, the network throughput can be effectively improved compared with that for previous protocols. Simulation results demonstrate the validity and effectiveness of the proposed protocol.
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  • Tetsuhiro OKANO, Shouhei KIDERA, Tetsuo KIRIMOTO
    Article type: PAPER
    Subject area: Sensing
    2012 Volume E95.B Issue 11 Pages 3556-3562
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    Blind source separation (BSS) techniques are required for various signal decomposing issues. Independent component analysis (ICA), assuming only a statistical independence among stochastic source signals, is one of the most useful BSS tools because it does not need a priori information on each source. However, there are many requirements for decomposing multiple deterministic signals such as complex sinusoidal signals with different frequencies. These requirements may include pulse compression or clutter rejection. It has been theoretically shown that an ICA algorithm based on maximizing non-Gaussianity successfully decomposes such deterministic signals. However, this ICA algorithm does not maintain a sufficient separation performance when the frequency difference of the sinusoidal waves becomes less than a nominal frequency resolution. To solve this problem, this paper proposes a super-resolution algorithm for complex sinusoidal signals by extending the maximum likelihood ICA, where the probability density function (PDF) of a complex sinusoidal signal is exploited as a priori knowledge, in which the PDF of the signal amplitude is approximated as a Gaussian distribution with an extremely small standard deviation. Furthermore, we introduce an optimization process for this standard deviation to avoid divergence in updating the reconstruction matrix. Numerical simulations verify that our proposed algorithm remarkably enhances the separation performance compared to the conventional one, and accomplishes a super-resolution separation even in noisy situations.
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  • Shouhei KIDERA, Tetsuo KIRIMOTO
    Article type: PAPER
    Subject area: Sensing
    2012 Volume E95.B Issue 11 Pages 3563-3571
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    Microwave imaging techniques, in particular synthetic aperture radar (SAR), are able to obtain useful images even in adverse weather or darkness, which makes them suitable for target position or feature estimation. However, typical SAR imagery is not informative for the operator, because it is synthesized using complex radio signals with greater than 1.0m wavelength. To deal with the target identification issue for imaging radar, various automatic target recognition (ATR) techniques have been developed. One of the most promising ATR approaches is based on neural network classification. However, in the case of SAR images heavily contaminated by random or speckle noises, the classification accuracy is severely degraded because it only compares the outputs of neurons in the final layer. To overcome this problem, this paper proposes a self organized map (SOM) based ATR method, where the binary SAR image is classified using the unified distance matrix (U-matrix) metric given by the SOM. Our numerical analyses and experiments on 5 types of civilian airplanes, demonstrate that the proposed method remarkably enhances the classification accuracy, particular in lower S/N situations, and holds a significant robustness to the angular variations of the observation.
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  • Zhiliang HUANG, Ming CHEN, Chunjuan DIAO, Jiamin LI
    Article type: LETTER
    Subject area: Fundamental Theories for Communications
    2012 Volume E95.B Issue 11 Pages 3572-3575
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    This letter presents a novel weighted reliability-based (WRB) algorithm for decoding low-density parity-check (LDPC) codes. Viewing the well-known normalized min sum (NMS) algorithm as reliability-based, the WRB algorithm can be seen as a simplified version of the NMS algorithm. Unlike the NMS algorithm, the WRB algorithm does not update the soft information sent between the variable nodes and check nodes, which greatly reduces the decoding complexity. For finite geometry LDPC codes with larger row redundancy and column weights, simulation results show that the WRB algorithm almost matches the error performance of the NMS algorithm.
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  • Xiaodong SUN, Shihua ZHU, Zhenjie FENG, Hui HUI
    Article type: LETTER
    Subject area: Fundamental Theories for Communications
    2012 Volume E95.B Issue 11 Pages 3576-3579
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    In this letter, we derive a lower bound on the diversity multiplexing tradeoff (DMT) in multiple-input multiple-output (MIMO) nonorthogonal amplify-and-forward (NAF) cooperative channels with resolution-constrained channel state feedback. It is shown that power control based on the feedback improves the DMT performance significantly in contrast to the no-feedback case. For instance, the maximum diversity increase is exponential in K with K-level feedback.
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  • Juinn-Horng DENG, Sheng-Yang HUANG
    Article type: LETTER
    Subject area: Transmission Systems and Transmission Equipment for Communications
    2012 Volume E95.B Issue 11 Pages 3580-3584
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    The single carrier block transmission (SCBT) system has become one of the most popular modulation systems because of its low peak to average power ratio (PAPR). This work proposes precoding design on the transmitter side to retain low PAPR, improve performance, and reduce computational complexity on the receiver side. The system is designed according to the following procedure. First, upper-triangular dirty paper coding (UDPC) is utilized to pre-cancel the interference among multiple streams and provide a one-tap time-domain equalizer for the SCBT system. Next, to solve the problem of the high PAPR of the UDPC precoding system, Tomlinson-Harashima precoding (THP) is developed. Finally, since the UDPC-THP system is degraded by the deep fading channels, the dynamic channel on/off assignment by the maximum capacity algorithm (MCA) and minimum BER algorithm (MBA) is proposed to enhance the bit error rate (BER) performance. Simulation results reveal that the proposed precoding transceiver can provide excellent BER and low PAPR performances for the SCBT system over a multipath fading channel.
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  • Seok-Kap KO, Hakjeon BANG, Kyungran KANG, Chang-Soo PARK
    Article type: LETTER
    Subject area: Network
    2012 Volume E95.B Issue 11 Pages 3585-3589
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    Existing forwarding strategies for delay tolerant networks aim at network throughput maximization. They provide forwarding opportunities to more reachable destinations. This results in the long end-to-end delay and low throughput of less reachable destinations. In this paper, we propose two forwarding strategies to improve the throughput of less reachable nodes with little throughput degradation of more reachable nodes. Evaluation results show that the proposed forwarding strategies can control the levels of fairness among the destinations while maintaining high throughput, compared with the legacy forwarding strategies.
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  • Kyungkoo JUN
    Article type: LETTER
    Subject area: Internet
    2012 Volume E95.B Issue 11 Pages 3590-3593
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    An active queue management (AQM) scheme is proposed to reduce throughput bias for UDP flows over TCP. It is argued that existing AQM methods partially involve a flow-indifferent factor that does not take into account of bandwidth usage of flows when they determine packet drop, thus resulting in unfairness. The proposed scheme replaces the flow-indifferent part with a flow-wise one by approximating per-flow fair share, which permits the discrimination of unresponsive flows. Since it is a stateless process, it avoids the overhead of tracking the statistics of flows and implementation is simple. A performance evaluation shows that it effectively limits the bandwidth of unresponsive flows to their fair share of bandwidth. In addition, it can also encourage RTT-fairness among TCP flows with different delays.
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  • HyunJin KIM
    Article type: LETTER
    Subject area: Network Management/Operation
    2012 Volume E95.B Issue 11 Pages 3594-3596
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    This paper proposes a bit-split string matcher architecture for a memory-efficient hardware-based parallel pattern matching engine. In the proposed bit-split string matcher, multiple finite-state machine (FSM) tiles share match vectors to reduce the required number of stored match vectors. By decreasing the memory size for storing match vectors, the total memory requirement can be minimized.
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  • Tae-Hak LEE, Jung-Woo BAIK, Junho CHOI, Young-Sik KIM
    Article type: LETTER
    Subject area: Antennas and Propagation
    2012 Volume E95.B Issue 11 Pages 3597-3600
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    In this letter a circular polarization microstrip antenna with switchable polarization is proposed. The switchable polarization sense characteristic is realized via a shunt connected varactor tuning diode. The appropriate capacitance of the diode at the reverse bias voltage can alter two circular polarizations, as the tuning diode, which is located near the rectangular slot in the circular patch, is utilized in a perturbation element. The switchable polarization is analyzed using the equivalent circuit model representing the resonances of each orthogonal mode. Simulation, calculated, and measured results agree well.
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  • Masao MASUGI, Norihito HIRASAWA, Yoshiharu AKIYAMA, Kazuo MURAKAWA
    Article type: LETTER
    Subject area: Electromagnetic Compatibility (EMC)
    2012 Volume E95.B Issue 11 Pages 3601-3604
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    This paper observes electrostatic discharge (ESD) events in terms of electromagnetic interference (EMI) assessments. To characterize the high frequency oscillations present in ESD waveforms, we use two kinds of discharge electrodes: copper and stainless steel spheres. Based on data gathered under charging voltages of 0.25, 0.5, and 1.0kV, we examine the energy levels of ESD waveforms. As a result, we find that the high-frequency energy, which is related to the high frequency oscillations in the ESD waveform, was affected by the material of discharge electrodes and the fast movement of discharge electrodes.
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  • Sang Goo KIM, Dongweon YOON, Janghoon OH
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2012 Volume E95.B Issue 11 Pages 3605-3608
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    The Multiple-Input Multiple-Output (MIMO) Zero-Forcing (ZF) receiver requires accurate Channel State Information (CSI), which is impacted by channel estimation error, to perform properly. Moreover, interference occurs due to the change of channel coefficients between the channel estimation events in fading channels. Thus, in practice, both channel estimation error and interference greatly influence Bit Error Rate (BER) performance. In this letter, we derive an Signal-to-Interference-and-Noise Ratio (SINR) expression considering both channel estimation error and interference and develop approximate closed-form BER expressions of M-PSK and M-QAM for the MIMO ZF receiver in Nakagami-m fading channels. We then analyze the effects of channel estimation error, interference, and the numbers of transmit and receive antennas.
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  • Bong Keol SHIN, Ju Wook JANG
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2012 Volume E95.B Issue 11 Pages 3609-3612
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    We observe that the state-of-the-art power-saving mechanisms (PSM) for IEEE 802.16e is neither optimal in terms of delay nor in terms of energy consumption. We propose a new PSM which achieves the optimality in terms of the average buffering delay without increasing energy consumption. In order to do so, we derive a formula which relates the average buffering delay to sleep intervals. Simulation results show that our scheme surpasses the BTE algorithm (used by the current IEEE 802.16e Mobile Stations) by 56.75-76% and the PSID algorithm by 8.52-24.39% in terms of the delay-energy consumption product.
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  • Benzhou JIN, Sheng ZHANG, Jian PAN, Xiaokang LIN
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2012 Volume E95.B Issue 11 Pages 3613-3616
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    Without recourse to the Shannon-Nyquist sampling theorem, a novel information sampling (IS) concept is proposed for ultra-wideband (UWB) communications. To implement IS, a random pre-coding system architecture is designed and system performance is studied. Simulation results from one of UWB channel models show that the proposed system is effective to detect UWB signals with a low-sampling-rate analog-to-digital converter (ADC) at the receiver. Moreover, it can operate in a regime of heavy inter-symbol interference (ISI).
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  • Zhaoxi FANG, Feng LIANG, Shaozhong ZHANG, Xiaolin ZHOU
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2012 Volume E95.B Issue 11 Pages 3617-3620
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    Timing asynchronism strongly degrades the performance of analog network coded (ANC) bi-directional transmission. This letter investigates receiver design for asynchronous broadband bi-directional transmission over frequency selective fading channels. Based on time domain oversampling, we propose fractionally spaced frequency domain minimum mean square error (MMSE) equalizers for bi-directional ANC based on orthogonal frequency division multiplexing (OFDM) and cyclic prefixed single carrier (CP-SC) radio access. Simulation results show that the proposed fractionally spaced equalizer (FSE) can eliminate the negative effect of timing misalignment in bi-directional transmissions.
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  • Seokhyun YOON, Kangwoon SEO, Taehyun JEON
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2012 Volume E95.B Issue 11 Pages 3621-3624
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    This letter addresses antenna ordering to improve the performance of the MIMO detectors in [4], where two low complexity MIMO detectors have been proposed based on either fully-connected or ring type pair-wise Markov random field (MRF). The former was shown to be better than the latter, while being more complex. The objective of this letter is to make the performance of the detector based on ring-type MRF (with complexity of O(2M·22m)) close to or better than that of fully-connected MRF (with complexity of O(M·(M-1)·22m)), by applying appropriate antenna ordering. The simulation results validate the proposed antenna ordering methods.
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  • Taejin JUNG, Hyoungsoo LIM
    Article type: LETTER
    Subject area: Terrestrial Wireless Communication/Broadcasting Technologies
    2012 Volume E95.B Issue 11 Pages 3625-3628
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    In this letter, we propose a new 4-dimensional constellation-rotation (CR) modulation method that achieves diversity gain of 4 in Rayleigh fading channels. The proposed scheme consists of two consecutive CR operations for QAM symbols unlike the conventional 2-dimensional CR method based on only one CR operation. Computer simulation results show that the new method exhibits much better performance than the conventional one in terms of code rate and channel erasure ratio.
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  • Jeong Woo LEE
    Article type: LETTER
    Subject area: Terrestrial Wireless Communication/Broadcasting Technologies
    2012 Volume E95.B Issue 11 Pages 3629-3632
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    A novel cooperative spectrum sensing scheme suitable for wireless cognitive radio system with imperfect reporting channels is proposed. In the proposed scheme, binary local decision bits are transmitted to the fusion center and combined to form a soft-valued decision statistics in the fusion center. To form a decision statistics, a majority-decision-aided weighting rule is proposed. The proposed scheme provides a reliable sensing capability even with poor reporting channels.
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  • Wei LIU, Yuan HU, Xingqun ZHAN
    Article type: LETTER
    Subject area: Navigation, Guidance and Control Systems
    2012 Volume E95.B Issue 11 Pages 3633-3636
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    In the framework of the modernization plan of COMPASS system, the existing COMPASS signals should be transmitted along with the modernized signals to maintain backward compatibility. In this paper, an efficient multiplexing scheme based on the optimal aligning method for combining COMPASS Phase II B3 and Phase III B3 signals is proposed, which offers significantly higher efficiency than Interplex and Generalized Majority Voting (GMV) multiplexing methods. The proposed scheme can provide potential opportunities for COMPASS system and other global navigation satellite systems (GNSS) modernization and construction plans.
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  • Wenting CHANG, Jintao WANG, Bo AI
    Article type: LETTER
    Subject area: Multimedia Systems for Communications
    2012 Volume E95.B Issue 11 Pages 3637-3641
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    A scheme that modulates the training sequence is proposed to support two-layer data streams in the time domain synchronous orthogonal frequency division multiplex (TDS-OFDM) systems. A theoretical analysis and computer simulation show that the proposed scheme works well and that the two layer data streams are compatible with each other.
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  • Sungjin KIM, Sangwon KANG
    Article type: LETTER
    Subject area: Multimedia Systems for Communications
    2012 Volume E95.B Issue 11 Pages 3642-3645
    Published: November 01, 2012
    Released on J-STAGE: November 01, 2012
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    In this paper, a block-constrained trellis coded vector quantization (BC-TCVQ) algorithm is combined with an algebraic codebook to produce an algebraic trellis vector code (ATVC) to be used in ACELP coding. ATVC expands the set of allowed algebraic codebook pulse position, and the trellis branches are labeled with these subsets. The Viterbi algorithm is used to select the excitation codevector. A fast codebook search method using an efficient non-exhaustive search technique is also proposed to reduce the complexity of the ATVC search procedure while maintaining the quality of the reconstructed speech. The ATVC block code is used as the fixed codebook of AMR-NB (12.2kbps), which reduces the computational complexity compared to the conventional algebraic codebook.
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