IEICE Transactions on Communications
Online ISSN : 1745-1345
Print ISSN : 0916-8516
Volume E95.B, Issue 12
Displaying 1-43 of 43 articles from this issue
Special Section on Coding and Coding Theory-Based Signal Processing for Wireless Communications
  • Tomoaki OHTSUKI
    2012 Volume E95.B Issue 12 Pages 3653
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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  • Xiaobo ZHOU, Xin HE, Khoirul ANWAR, Tad MATSUMOTO
    Article type: INVITED PAPER
    2012 Volume E95.B Issue 12 Pages 3654-3662
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    In this paper, we reformulate the issue related to wireless mesh networks (WMNs) from the Chief Executive Officer (CEO) problem viewpoint, and provide a practical solution to a simple case of the problem. It is well known that the CEO problem is a theoretical basis for sensor networks. The problem investigated in this paper is described as follows: an originator broadcasts its binary information sequence to several forwarding nodes (relays) over Binary Symmetric Channels (BSC); the originator's information sequence suffers from independent random binary errors; at the forwarding nodes, they just further interleave, encode the received bit sequence, and then forward it, without making heavy efforts for correcting errors that may occur in the originator-relay links, to the final destination (FD) over Additive White Gaussian Noise (AWGN) channels. Hence, this strategy reduces the complexity of the relay significantly. A joint iterative decoding technique at the FD is proposed by utilizing the knowledge of the correlation due to the errors occurring in the link between the originator and forwarding nodes (referred to as intra-link). The bit-error-rate (BER) performances show that the originator's information can be reconstructed at the FD even by using a very simple coding scheme. We provide BER performance comparison between joint decoding and separate decoding strategies. The simulation results show that excellent performance can be achieved by the proposed system. Furthermore, extrinsic information transfer (EXIT) chart analysis is performed to investigate convergence property of the proposed technique, with the aim of, in part, optimizing the code rate at the originator.
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  • Zhonghao ZHANG, Chongbin XU, Li PING
    Article type: INVITED PAPER
    2012 Volume E95.B Issue 12 Pages 3663-3670
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    In this paper, we present a transmission scheme for a multiple-input multiple-output (MIMO) quasi-static fading channel with imperfect channel state information at the transmitter (CSIT). In this scheme, we develop a precoder structure to exploit the available CSIT and apply spatial coupling for further performance enhancement. We derive an analytical evaluation method based on extrinsic information transfer (EXIT) functions, which provides convenience for our precoder design. Furthermore, we observe an area property indicating that, for a spatially coupled system, the iterative receiver can perform error-free decoding even the original uncoupled system has multiple fixed points in its EXIT chart. This observation implies that spatial coupling is useful to alleviate the uncertainty in CSIT which causes difficulty in designing LDPC code based on the EXIT curve matching technique. Numerical results are presented, showing an excellent performance of the proposed scheme in MIMO fading channels with imperfect CSIT.
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  • Meng CHENG, Xiaobo ZHOU, Khoirul ANWAR, Tad MATSUMOTO
    Article type: PAPER
    2012 Volume E95.B Issue 12 Pages 3671-3678
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    In this work, a simple doped accumulator (DACC)-assisted relay system is proposed by using bit-interleaved coded modulation with iterative decoding (BICM-ID). An extrinsic information transfer (EXIT) chart analysis shows that DACC keeps the convergence tunnel of the EXIT curves open until almost the (1, 1) point of the mutual information, which avoids the error floor. In the relay system, errors may happen in the source-relay link (intra-link), however, they are allowed in our proposed technique where the correlation knowledge between the source and the relay is exploited at the destination node. Strong codes are not needed and even the systematic source bits can be simply extracted at the relay even though the systematic part may contain some errors. Hence, the complexity of the relay can be significantly reduced, and thereby the proposed system is energy-efficient. Furthermore, the error probability of the intra-link can be estimated at the receiver by utilizing the a posteriori log-likelihood ratios (LLRs) of the two decoders, and it can be further utilized in the iterative processing. Additionally, we provide the analysis of different relay location scenarios and compare the system performances by changing the relay's location. The transmission channels in this paper are assumed to suffer from additive white Gaussian noise (AWGN) and block Rayleigh fading. The theoretical background of this technique is the Slepian-Wolf/Shannon theorem for correlated source coding. The simulation results show that the bit-error-rate (BER) performances of the proposed system are very close to theoretical limits supported by the Slepian-Wolf/Shannon theorem.
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  • Jungo GOTO, Osamu NAKAMURA, Kazunari YOKOMAKURA, Yasuhiro HAMAGUCHI, S ...
    Article type: PAPER
    2012 Volume E95.B Issue 12 Pages 3679-3687
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    This paper proposes a spectrum-overlapped resource management (SORM) technique where each user equipment (UE) can ideally obtain the frequency selection diversity gain under multi-user environments. In the SORM technique for cellular systems, under assumption of adopting a soft canceller with minimum mean square error (SC/MMSE) turbo equalizer, an evolved node B (eNB) accepts overlapped frequency resource allocation. As a result, each UE can use the frequency bins having the highest channel gain. However, the SORM becomes non-orthogonal access when the frequency bins having high channel gain for UEs are partially identical. In this case, the inter-user interference (IUI) caused by overlapping spectra among UEs is eventually canceled out by using the SC/MMSE turbo equalizer. Therefore, SORM can achieve better performance than orthogonal access e.g. FDMA when the IUI is completely canceled. This paper demonstrates that SORM has the potential to improve transmission performance, by extrinsic information transfer (EXIT) analysis. Moreover, this paper evaluates the block error rate (BLER) performance of the SORM and the FDMA. Consequently, this paper shows that the SORM outperforms the FDMA.
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  • Teruo KAWAMURA, Ryota TAKAHASHI, Hideyuki NUMATA, Nobuhiko MIKI, Mamor ...
    Article type: PAPER
    2012 Volume E95.B Issue 12 Pages 3688-3698
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    This paper presents joint maximum likelihood detection (MLD) using channel coding information for orthogonal code division multiple access (CDMA) to decrease the required average received signal-to-noise power ratio (SNR) satisfying the target block error rate (BLER), and investigates the effect of joint MLD from the conventional coherent detection associated with channel coding. In the paper, we assume the physical uplink control channel (PUCCH) as specified in Release 8 Long-Term Evolution (LTE) by the 3rd Generation Partnership Project (3GPP) as the radio interface for the uplink control channel. First, we clarify the best scheme for combining correlation signals in two frequency-hopped slots and in two receiver diversity branches for joint MLD. Then, we show that the joint MLD without channel estimation, in which correlation signals are combined in squared form, decreases the required average received SNR compared to that for joint MLD with coherent combining of the correlation signals using channel estimation. Second, we show the effectiveness of joint MLD in terms of the decrease in the required average received SNR compared to the conventional coherent detection in various delay spread channels. Third, we present a comparison of the average BLER performance levels between cyclic shift (CS)-CDMA and block spread (BS)-CDMA using joint MLD. We show that when using joint MLD, BS-CDMA is superior to CS-CDMA due to a lower required received SNR in short delay spread environments and that in contrast, CS-CDMA provides a lower required received SNR compared to BS-CDMA in long delay spread environments.
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  • Lianjun DENG, Teruo KAWAMURA, Hidekazu TAOKA, Mamoru SAWAHASHI
    Article type: PAPER
    2012 Volume E95.B Issue 12 Pages 3699-3707
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    This paper proposes applying intra-subframe frequency hopping (FH) to closed-loop (CL) type transmit diversity using codebook based precoding for a shared channel carrying user traffic data in discrete Fourier transform (DFT)-precoded Orthogonal Frequency Division Multiple Access (OFDMA). In the paper, we present two types of precoding schemes associated with intra-subframe FH: individual precoding vector selection between 2 slots where a 1-ms subframe comprises 2 slots among the reduced precoding codebooks, and common precoding vector selection between 2 slots. We investigate the effect of intra-subframe FH on the codebook based transmit diversity in terms of the average block error rate (BLER) performance while maintaining the same number of feedback bits required for notification of the selected precoding vector as that for the conventional CL transmit diversity without FH. Computer simulation results show that the codebook based transmit diversity with intra-subframe FH is very effective in decreasing the required average received signal-to-noise power ratio (SNR) when the fading maximum Doppler frequency, fD, is higher than approximately 50Hz both for 2- and 4-antenna transmission in the DFT-precoded OFDMA.
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  • Lianjun DENG, Teruo KAWAMURA, Hidekazu TAOKA, Mamoru SAWAHASHI
    Article type: PAPER
    2012 Volume E95.B Issue 12 Pages 3708-3718
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    This paper presents comprehensive comparisons based on the block error rate (BLER) of open-loop (OL) transmit diversity schemes considering a cubic metric (CM) for single-carrier (SC)-Frequency Division Multiple Access (FDMA) using discrete Fourier transform (DFT)-precoded OFDMA in uplink frequency-selective fading channels. The OL transmit diversity schemes assumed in the paper are space-time block code (STBC), space-frequency block code (SFBC), single-carrier (SC) - SFBC, cyclic delay diversity (CDD), and frequency switched transmit diversity (FSTD) for two antennas and a combination of STBC, SFBC, SC-SFBC and selection transmit diversity including time switched transmit diversity (TSTD) or FSTD for four antennas. We derive the most appropriate OL transmit diversity scheme for SC-FDMA using a frequency domain equalizer (FDE) with QPSK and 16QAM modulations and with various channel coding rates employing turbo coding. We investigate the best OL transmit diversity scheme under various propagation channel conditions including the fading maximum Doppler frequency and root mean square (r.m.s.) delay spread, and the fading correlation between transmitter/receiver antennas.
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  • Reo KOBAYASHI, Teruo KAWAMURA, Nobuhiko MIKI, Mamoru SAWAHASHI
    Article type: PAPER
    2012 Volume E95.B Issue 12 Pages 3719-3727
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    This paper presents comprehensive comparisons of the achievable throughput between the 32-/64-ary amplitude and phase shift keying (APSK) and cross 32QAM/square 64QAM schemes based on mutual information (MI) considering the peak-to-average power ratio (PAPR) of the modulated signal. As a PAPR criterion, we use a cubic metric (CM) that directly corresponds to the transmission back-off of a power amplifier. In the analysis, we present the best ring ratio for the 32 or 64APSK scheme from the viewpoint of minimizing the required received signal-to-noise power ratio (SNR) considering the CM that achieves the peak throughput, i.e., maximum error-free transmission rate. We show that the required received SNR considering the CM at the peak throughput is minimized with the number of rings of M =3 and 4 for 32-ary APSK and 64-asry APSK, respectively. Then, we show with the best ring ratios that the (4, 12, 16) 32APSK scheme with M =3 achieves a lower required received SNR considering the CM compared to that for the cross 32QAM scheme. Similarly, we show that the (4, 12, 20, 28) 64APSK scheme with M =4 achieves almost the same required received SNR considering the CM as that for the square 64QAM scheme.
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  • Yousuke SANO, Yusuke OHWATARI, Nobuhiko MIKI, Yuta SAGAE, Yukihiko OKU ...
    Article type: PAPER
    2012 Volume E95.B Issue 12 Pages 3728-3738
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    This paper investigates the dominant impact on the interference rejection combining (IRC) receiver due to the downlink reference signal (RS) based covariance matrix estimation scheme. When the transmission modes using the cell-specific RS (CRS) in LTE/LTE-Advanced are assumed, the property of the non-precoded CRS is different from that of the data signals. This difference poses two problems to the IRC receiver. First, it results in different levels of accuracy for the RS based covariance matrix estimation. Second, assuming the case where the CRS from the interfering cell collides with the desired data signals of the serving cell, the IRC receiver cannot perfectly suppress this CRS interference. The results of simulations assuming two transmitter and receiver antenna branches show that the impact of the CRS-to-CRS collision among cells is greater than that for the CRS interference on the desired data signals especially in closed-loop multiple-input multiple-output (MIMO) systems, from the viewpoint of the output signal-to-interference-plus-noise power ratio (SINR). However, the IRC receiver improves the user throughput by more than 20% compared to the conventional maximal ratio combining (MRC) receiver under the simulation assumptions made in this paper even when the CRS-to-CRS collision is assumed. Furthermore, the results verify the observations made in regard to the impact of inter-cell interference of the CRS for various average received signal-to-noise power ratio (SNR) and signal-to-interference power ratio (SIR) environments.
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  • Yousuke SANO, Yusuke OHWATARI, Nobuhiko MIKI, Akihito MORIMOTO, Yukihi ...
    Article type: PAPER
    2012 Volume E95.B Issue 12 Pages 3739-3751
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    The interference rejection combining (IRC) receiver, which can suppress inter-cell interference, is effective in improving the cell-edge user throughput. The IRC receiver is typically based on the minimum mean square error (MMSE) criteria, and requires a covariance matrix including the interference signals, in addition to a channel matrix from the serving cell. Therefore, in order to clarify the gain from the IRC receiver, the actual estimation error of these matrices should be taken into account. In a system performance evaluation, the link performance modeling of the IRC receiver, i.e., the output signal-to-interference-plus-noise power ratio (SINR) after IRC reception including the estimation errors, is very important in evaluating the actual performance of the IRC receiver in system level simulations. This is because these errors affect the suppression of the interference signals for the IRC receiver. Therefore, this paper investigates and proposes IRC receiver modeling schemes for the covariance matrix and channel estimation errors. As the modeling scheme for the covariance matrix, we propose a scheme that averages the conventional approximation using the complex Wishart distribution in the frequency domain to address issues that arise in a frequency selective fading channel. Furthermore, we propose a modeling scheme for the channel estimation error according to the ideal channel response of all cells and a channel estimation filter to address channel fading fluctuations. The results of simulations assuming the LTE/LTE-Advanced downlink with two transmitter and receiver antenna branches show that the proposed modeling scheme for the covariance matrix estimation error accurately approximates the performance of a realistic IRC receiver, which estimates the covariance matrix and channel matrix of the serving cell based on the demodulation reference signal (DM-RS), even in a frequency selective fading channel. The results also show that the proposed modeling scheme for the channel estimation error is a robust scheme in terms of the r.m.s. delay spread of a channel model compared to the scheme using the mean square error (MSE) statistic of the estimated channel coefficients based on a channel estimation filter.
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  • Nobuaki OTSUKI, Takatoshi SUGIYAMA
    Article type: PAPER
    2012 Volume E95.B Issue 12 Pages 3752-3759
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    This paper presents the feasibility of a wireless network coding prototype system based on time division multiple access using the global positioning system to facilitate the time synchronization of wireless nodes. We evaluate the system throughput of the prototype system with wireless network coding and Ethernet frame aggregation in the full buffer traffic environment assuming web browsing and voice over Internet protocol. The experimental results show that the prototype system improves the system throughput by approximately 1.85-fold compared to a system without wireless network coding or aggregation even in a multipath Rician fading environment.
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  • Jonghoon RYU
    Article type: LETTER
    2012 Volume E95.B Issue 12 Pages 3760-3762
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    Permutation polynomial based interleavers over integer rings, in particular quadratic permutation polynomials have been widely studied. In this letter, higher degree permutation polynomials for interleavers are considered for interleavers and permutation polynomials superior to quadratic permutation polynomials are found for some lengths.
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  • Kazuyuki MORIOKA, David ASANO
    Article type: LETTER
    2012 Volume E95.B Issue 12 Pages 3763-3767
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    In this letter, the tradeoff between symbol rate and diversity gain of Space-Time Block Codes (STBCs) with linear receivers is considered. It is known that Group Orthogonal-Toeplitz Codes (GOTCs) can achieve a good tradeoff with linear receivers. However, the symbol rate of GOTCs is limited to that of the base Orthogonal Space-Time Block Codes (OSTBCs). We propose to simply change the GOTC base codes from OSTBCs to Quasi-Orthogonal Space-Time Block Codes (Q-OSTBCs). Q-OSTBCs can improve the symbol rate of GOTCs at the expense of diversity gain. Simulation results show that Q-OSTBC based GOTCs can improve the tradeoff between symbol rate and diversity gain over that of the original GOTCs.
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  • Ruohan CAO, Tiejun LV, Hui GAO, Yueming LU, Yongmei SUN
    Article type: LETTER
    2012 Volume E95.B Issue 12 Pages 3768-3771
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    A specific physical layer network coding (PNC) scheme is proposed for the two-way relay channel. Unlike the traditional binary PNC that focuses mainly on BPSK modulation, the proposed PNC scheme is tailored for general MPSK modulation. In particular, the product of the two modulated signals is considered as a network-coded symbol. The proposed network coding operation occurs naturally in the inner or outer product of the received signal. A novel PNC-specific detection principle is then developed to estimate the network-coded symbol. Simulations show that the proposed scheme achieves almost optimal performance in terms of end-to-end bit error rate (BER), where the relay node is equipped with multiple antennas.
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Regular Section
  • Nobuaki OTSUKI, Takatoshi SUGIYAMA
    Article type: PAPER
    Subject area: Fundamental Theories for Communications
    2012 Volume E95.B Issue 12 Pages 3772-3785
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    In this paper, we propose a wireless network coding diversity technique based on hybrid amplify-and-forward/decode-and-forward relay method employing adaptive power control for two-hop wireless networks in order to improve relay node position flexibility. Wireless network coding diversity based on hybrid relay method selects either modulation symbol level wireless network coding diversity or bit sequence level wireless network coding diversity as its wireless network coding diversity scheme according to the cyclic redundancy check result at the relay node. Moreover, the adaptive power control scheme proposed here controls the relay node's transmit power according to its position. Computer simulations verify that wireless network coding diversity based on hybrid relay method employing the adaptive power control scheme can expand the area wherein the relay node can be located while satisfying the required communication quality by 4.56 times compared to the conventional wireless network coding diversity scheme. Therefore, we confirm that our proposed scheme can increase relay node position flexibility.
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  • Yong WANG, Jian-hua GE, Jun HU, Bo AI
    Article type: PAPER
    Subject area: Transmission Systems and Transmission Equipment for Communications
    2012 Volume E95.B Issue 12 Pages 3786-3792
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    An accurate and rapid synchronization scheme is a prerequisite for achieving high-quality multimedia transmission for wireless handheld terminals, e.g. China multimedia mobile broadcasting (CMMB) system. In this paper, an efficient orthogonal frequency division multiplexing (OFDM) timing synchronization scheme, which is robust to the doubly selective fading channel, is proposed for CMMB system. TS timing is derived by performing an inverse sliding correlation (ISC) between the segmented Sync sequences in the Beacon, which possesses the inverse conjugate symmetry (ICS) characteristic. The ISC can provide sufficient correlative gain even in the ultra low signal noise ratio (SNR) scenarios. Moreover, a fast fine symbol timing method based on the auto-correlation property of Sync sequence is also presented. According to the detection strategy for the significant channel taps, the specific information about channel profile can be obtained. The advantages of the proposed timing scheme over the traditional ones have been demonstrated through both theoretical analysis and numerical simulations.
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  • Tatsumi TAKAGI, Hiroshi HASEGAWA, Ken-ichi SATO, Yoshiaki SONE, Akira ...
    Article type: PAPER
    Subject area: Fiber-Optic Transmission for Communications
    2012 Volume E95.B Issue 12 Pages 3793-3801
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    We propose optical path routing and frequency slot assignment algorithms that can make the best use of elastic optical paths and the capabilities of distance adaptive modulation. Due to the computational difficulty of the assignment problem, we develop algorithms for 1+1 dedicated/1:1 shared protected ring networks and unprotected mesh networks to that fully utilize the characteristics of the topologies. Numerical experiments elucidate that the introduction of path elasticity and distance adaptive modulation significantly reduce the occupied bandwidth.
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  • Jean Marc Kouakou ATTOUNGBLE, Kazunori OKADA
    Article type: PAPER
    Subject area: Network
    2012 Volume E95.B Issue 12 Pages 3802-3810
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    In this paper, we present Greedy Routing for Maximum Lifetime (GRMax) [1],[2] which can use the limited energy available to nodes in a Wireless Sensor Network (WSN) in order to delay the dropping of packets, thus extend the network lifetime. We define network lifetime as the time period until a source node starts to drop packets because it has no more paths to the destination [3]. We introduce the new concept of Network Connectivity Aiming (NCA) node. The primary goal of NCA nodes is to maintain network connectivity and avoid network partition. To evaluate GRMax, we compare its performance with Geographic and Energy Aware Routing (GEAR) [4], which is an energy efficient geographic routing protocol and Greedy Perimeter Stateless Routing (GPSR) [5], which is a milestone among geographic routing protocol. We evaluate and compare the performance of GPSR, GEAR, and GRMax using OPNET Modeler version 15. The results show that GRMax performs better than GEAR and GPSR with respect to the number of successfully delivered packets and the time period before the nodes begin to drop packets. Moreover, with GRMax, there are fewer dead nodes in the system and less energy is required to deliver packets to destination node (sink).
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  • Shohei KAMAMURA, Daisaku SHIMAZAKI, Atsushi HIRAMATSU, Hidenori NAKAZA ...
    Article type: PAPER
    Subject area: Network
    2012 Volume E95.B Issue 12 Pages 3811-3821
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    IP fast rerouting has widely been studied for realizing millisecond-order recovery on pure IP networks. This paper proposes IP fast rerouting using backup topologies against concurrent double failures. The main issue in recovering from multiple failures is avoiding forwarding loops. To avoid forwarding loops, we propose a deterministic forwarding algorithm, which estimates the concurrently occurring failures from the packet header information. We also propose an efficient backup topology design algorithm which is both loop-free and which reduces the number of backup topologies. Our key idea is preparing the adequate diversity of backup routes for arbitrary source and destination pairs by combination of backup topologies. For efficient computation of diverse routes, we propose a similarity comparison-based algorithm between the original topology and the backup topologies. Our algorithm can achieve nearly optimal loop-free restoration from double failures on realistic topologies without explicit failure notification.
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  • Daisuke ANZAI, Sho AOYAMA, Masafumi YAMANAKA, Jianqing WANG
    Article type: PAPER
    Subject area: Electromagnetic Compatibility (EMC)
    2012 Volume E95.B Issue 12 Pages 3822-3829
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    Wireless capsule endoscopy (WCE) is now one of most important applications in implant body area networks (BANs). WCE requires high throughput performance due to its real-time data transmission, whereas the communication performance depends much on the transmit power, which is strictly regulated in order to satisfy a safety guideline in terms of specific absorption rate (SAR). Spatial diversity reception is well known to improve the wireless performance without any temporal and spectral resource expansion. Additionally, applying spatial diversity reception to WCE systems can be expected to not only improve the wireless communication performance but also to reduce SAR. Therefore, this paper investigates the impact of spatial diversity reception on SAR levels for the 400MHz medical implant communication service (MICS) band. To begin with, based on finite-difference time-domain (FDTD) simulations for implant BAN propagation with a numerical human body model, we first calculate the BER performance and derive the required transmit power to secure a permissible BER. Then, this paper calculates the local peak SAR under the required transmit power when the implant transmitter moves through the digestive organs. Finally, our simulation results demonstrate that applying spatial diversity reception can significantly reduce SAR in implant BANs.
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  • Takenori YASUZUMI, Shunki KATO, Yuya ISHII, Ryosuke SUGA, Osamu HASHIM ...
    Article type: PAPER
    Subject area: Electromagnetic Compatibility (EMC)
    2012 Volume E95.B Issue 12 Pages 3830-3836
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    A new wideband wave absorber with translucent structure using carbon fibers is presented in this paper. The absorber is composed of bundled short carbon fibers which are arranged in front of a back metal and a spacer. Absorption characteristics of the one-layered absorber showed that matching frequencies can be controlled by the thickness of the spacer and the length of the carbon fibers. To further improve the characteristics, multi-layered absorbers are designed with the same procedure as one-layered absorber. The designed absorber showed 15dB absorption characteristics from 1.0 to 10.0GHz. Then a small anechoic chamber with the inside dimension of 200cm × 200cm × 200cm was fabricated using ninety-six proposed absorbers. The electrical power in the chamber was measured at 2.45GHz and the results showed that the variation of the power was less than 4dB inside a circle with radius of 60cm as work space for electromagnetic measurements.
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  • Hiroyuki OSADA, Mamiko INAMORI, Yukitoshi SANADA
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2012 Volume E95.B Issue 12 Pages 3837-3844
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    A diversity scheme with Fractional Sampling (FS) in OFDM receivers has been investigated recently. FS path diversity makes use of the imaging components of the desired signal transmitted on the adjacent channel. To increase the diversity gain with FS the bandwidth of the transmit signal has to be enlarged. This leads to the reduction of spectrum efficiency. In this paper non-orthogonal access over multiple channels in the frequency domain with iterative interference cancellation (IIC) and FS is proposed. The proposed scheme transmits the imaging component non-orthogonally on the adjacent channel. In order to accommodate the imaging component, it is underlaid on the other desired signal. Through diversity with FS and IIC, non-orthogonal access on multiple channels is realized. Our proposed scheme can obtain diversity gains for non-orthogonal signals modulated with QPSK.
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  • Xiaoyan HUANG, Yuming MAO, Supeng LENG, Yan ZHANG, Qin YU
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2012 Volume E95.B Issue 12 Pages 3845-3854
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    This paper focuses on power control in relay-enhanced multicell networks with universal frequency reuse for maximizing the overall system throughput, subject to interference and noise impairments, and individual power constraints at both BSs and RSs. With a high signal-to-interference-plus-noise ratio (SINR) approximation, an energy efficiency based power allocation algorithm is proposed to achieve the maximum sum throughput with the least power consumption. Moreover, an iterative quasi-distributed power allocation algorithm is also presented, which is suitable for any SINR regime. Numerical results indicate that the proposed algorithms approach the optimal power allocation and the system performance can be significantly improved in terms of network throughput and energy efficiency.
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  • Qi ZHAO, Zhijie WU
    Article type: PAPER
    Subject area: Terrestrial Wireless Communication/Broadcasting Technologies
    2012 Volume E95.B Issue 12 Pages 3855-3862
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    Based on a proposed frame structure with an unequal sensing slot duration for each channel, and two sensing scenarios (with or without cooperation), a joint channel and sensing time assignment is suggested to maximize the uplink throughput of the centralized multi-band cognitive radio network with the consideration of the mutual interference among the secondary users (SUs). Firstly, the channel assignment is performed by using the proposed Delta Non-square Hungarian (DNH), which is a modified iterative Hungarian algorithm distinguished by throughput increment maximization and non-square weight matrix. Simulation results illustrate that DNH has significant advantages in enhancing the throughput and reducing the computational complexity. Moreover, a hybrid channel assignment, also performed by DNH, is improved based on the two sensing scenarios to maximize the throughput while efficiently limiting the interference power to primary users. Secondly, the convexity of the throughput functions within the range of sensing time is proved under the proposed frame structure, and then the maximum throughput is achieved through the steepest descent method-based sensing time assignment. Both of these results are corroborated by simulations.
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  • Nima M. POURNEJATIAN, Mohammad M. NAYEBI, Mohammad R. TABAN
    Article type: PAPER
    Subject area: Sensing
    2012 Volume E95.B Issue 12 Pages 3863-3872
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    Accurate modeling of sea clutter and detection of low observable targets within sea clutter are the major goals of radar signal processing applications. Recently, fractal geometry has been applied to the analysis of high range resolution radar sea clutters. The box-counting method is widely used to estimate fractal dimension but it has some drawbacks. We explain the drawbacks and propose a new fractal dimension based detector to increase detection performance in comparison with traditional detectors. Both statistically generated and real data samples are used to compare detector performance.
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  • HyunYong LEE, Akihiro NAKAO
    Article type: LETTER
    Subject area: Network
    2012 Volume E95.B Issue 12 Pages 3873-3874
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    In this letter, we argue that user resources will be still useful in the information-centric network (ICN). From this point of view, we first examine how P2P utilizing user resources looks like in ICN. Then, we identify challenging research issues to utilize user resources in ICN.
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  • Dong-Won KUM, Ajmal KHAN, You-Ze CHO
    Article type: LETTER
    Subject area: Network
    2012 Volume E95.B Issue 12 Pages 3875-3878
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    This paper proposes an efficient broadcast scheme based on traffic density measurement to mitigate broadcast storms in Vehicular Ad Hoc Networks (VANETs). In a VANET, the number of vehicles that rebroadcasts a message is closely related with the collision ratio of the message, so a well-designed broadcast scheme should consider traffic density when rebroadcasting a message. The proposed scheme introduces a traffic density measurement scheme and broadcast scheme for VANET. It is based on the slotted p-persistence scheme, but the rebroadcast procedure is enhanced and the rebroadcast probability p is controlled dynamically according to the estimated traffic density. Simulation results demonstrate that the proposed scheme outperforms existing schemes in terms of the end-to-end delay and collision ratio.
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  • Yousic LEE, Jae-Dong LEE, Taekeun PARK
    Article type: LETTER
    Subject area: Network
    2012 Volume E95.B Issue 12 Pages 3879-3881
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    In this letter, for offloading traffic to Wireless Local Area Network (WLAN) with transport layer mobility where WLAN service is intermittently available, we propose a novel scheme to freeze and melt the timeout handling procedure of SCTP. Simulation results show that the proposed scheme significantly improves the performance in terms of file transfer completion time.
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  • Tao LIU
    Article type: LETTER
    Subject area: Network
    2012 Volume E95.B Issue 12 Pages 3882-3885
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    In wireless sensor networks, unbalanced energy consumption and transmission collisions are two inherent problems and can significantly reduce network lifetime. This letter proposes an unequal clustering and TDMA-like scheduling mechanism (UCTSM) based on a gradient sinking model in wireless sensor networks. It integrates unequal clustering and TDMA-like transmission scheduling to balance the energy consumption among cluster heads and reduce transmission collisions. Simulation results show that UCTSM balances the energy consumption among the cluster heads, saves nodes' energy and so improves the network lifetime.
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  • Sangwon PARK, Youchan JEON, Myeongyu KIM, Sanghoon SONG, Jinwoo PARK
    Article type: LETTER
    Subject area: Antennas and Propagation
    2012 Volume E95.B Issue 12 Pages 3886-3889
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    In this letter, we present a method for improving the front-to-back ratio (FBR) of a broadcast antenna. The digitalization of terrestrial TV demands more efficient channel usage due to the reduction in TV bands after the switch-over. Thus, we designed an antenna with an FBR improved over -45dB as compared to the -20 to -25dB FBR range of existing antennas. We show experimentally that this antenna satisfies the required performance.
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  • Dong-Jun KIM, Tae-Hak LEE, Jun-Ho CHOI, Young-Sik KIM
    Article type: LETTER
    Subject area: Antennas and Propagation
    2012 Volume E95.B Issue 12 Pages 3890-3894
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    In this letter, a novel ultra-wideband circular quasi-fractal monopole antenna with a six-petaled lotus pattern is presented. The CPW-fed technique and quasi-fractal concept are used to achieve ultra-wideband characteristics. The size of the proposed antenna is 42×50mm2 with a lotus diameter of 19.8mm. The proposed antenna exhibits ultra-wideband characteristics from 2.65 to 12.72GHz, which corresponds to a fractional bandwidth of 131%. The measured radiation pattern of the proposed antenna is nearly omnidirectional.
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  • Xiaoli XI, Yongxing DU, Jiangfan LIU, Jinsheng ZHANG
    Article type: LETTER
    Subject area: Antennas and Propagation
    2012 Volume E95.B Issue 12 Pages 3895-3897
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    The unconditional stable finite-difference time-domain (US-FDTD) method based on Laguerre polynomial expansion and Galerkin temporal testing is used to model thin-film bulk acoustic wave resonators (TFBAR). Numerical results show the efficiency of the US-FDTD algorithm.
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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 12 Pages 3898-3901
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    To clarify the characteristics of high-speed electrostatic discharge (ESD) events, we use two kinds of discharge electrodes: sphere- and cylinder-shape ones. We measure the energy level of ESD waveforms with charging voltages of 0.25, 0.5, and 1.0kV. We find that the cylindrical electrode yields higher high-speed ESD energies, especially when the charging voltage is high; this indicates that the discharge gap shape is an important factor in ESD events.
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  • Jong-Kwan LEE, Kyu-Man LEE, JaeSung LIM
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2012 Volume E95.B Issue 12 Pages 3902-3905
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    In this letter, we propose a fast dynamic slot assignment (F-DSA) protocol to reduce timeslot access delay of a newly arrived node in ad hoc networks. As there is no central coordinator, a newly arrived node needs separate negotiation with all the neighboring nodes for assigning slots to itself. Thus, it may result in network join delay and this becomes an obstacle for nodes to dynamically join and leave networks. In order to deal with this issue better, F-DSA simplifies the slot assignment process. It provides frequent opportunities to assign slots by using mini-slots to share control packets in a short time. Numerical analysis and extensive simulation show that F-DSA can significantly reduce the timeslot access delay compared with other existing slot assignment protocols. In addition, we investigate the effect of the mini-slot overhead on the performance.
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  • Xuan GENG, Fang CAO, Qi-ming SHI
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2012 Volume E95.B Issue 12 Pages 3906-3910
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    In this letter, non-orthogonal amplify-and-forward (NAF) is considered in a half-duplex two-way system. We derive the closed-form outage probability in the high signal-to-noise ratio (SNR) region, and approximate it with a simpler version to enable power allocation. Then a closed-form power allocation scheme is proposed to improve the outage performance; it uses only statistical channel knowledge (SCK). It is validated that our analyses agree with simulation results and the proposed power allocation approaches the optimal power allocation.
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  • Bin SHENG, Pengcheng ZHU, Xiaohu YOU
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2012 Volume E95.B Issue 12 Pages 3911-3914
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    In OFDM systems, the correlation of cyclic prefix (CP) with its corresponding part at the end of the symbol can be used to estimate the maximum Doppler spread. However, the estimation accuracy of this CP based method is seriously affected by the inter-symbol interference (ISI) generated in the multipath channel. In this letter, we propose an enhanced CP based method which is immune to the ISI and can hence obtain an unbiased estimate of the auto-correlation function in multipath channels.
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  • Chuiqiang SUN, Jianhua GE, Rong SUN, Xinxin BAO
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2012 Volume E95.B Issue 12 Pages 3915-3917
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    A multiuser precoding algorithm based on matching weighted signal-to-leakage-and-noise ratio (SLNR) is proposed for multiuser MIMO downlink systems. In the proposed algorithm, the matching weight factor is selected based on the effective channel gain, and the leakage power caused by each user is weighted by the factor. The precoding vector is obtained by maximizing the matching weighted SLNR. Simulation results show the superiority of the proposed scheme in terms of bit error rate over the conventional SLNR schemes.
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  • Youchan JEON, Haesoo KIM, Jinwoo PARK
    Article type: LETTER
    Subject area: Terrestrial Wireless Communication/Broadcasting Technologies
    2012 Volume E95.B Issue 12 Pages 3918-3921
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    We propose three operation modes, namely, DCF uplink, Downlink, and CTS uplink modes to solve the unfairness problem between uplink and downlink as well as improve the performance of delay and throughput. The proposed scheme only requires modifying AP's functionalities without any changes of STAs, and is fully backward compatible to the legacy DCF. Its analytical result is validated against simulation and performance evaluation shows the proposed scheme is superior to the traditional IEEE 802.11 WLAN.
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  • Ruifeng MA, Zhaocheng WANG, Zhixing YANG
    Article type: LETTER
    Subject area: Terrestrial Wireless Communication/Broadcasting Technologies
    2012 Volume E95.B Issue 12 Pages 3922-3924
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    This letter presents a flexible signal structure supporting localization service for time domain synchronous OFDM (TDS-OFDM) in multi-service transmission applications. Localization is treated as one specific service and the corresponding data is allocated within the physical layer pipe (PLP) of the first subframe. The concept of variable sub-carrier spacing to combat Doppler spread is also introduced for the localization service. Simulation results indicate that the proposed scheme outperforms the conventional scheme and at the same time achieves high positioning accuracy.
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  • Sungwook KIM
    Article type: LETTER
    Subject area: Terrestrial Wireless Communication/Broadcasting Technologies
    2012 Volume E95.B Issue 12 Pages 3925-3928
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    Recently, cooperative spectrum sensing is being studied to greatly improve the sensing performance of cognitive radio networks. To develop an adaptable cooperative sensing algorithm, an important issue is how to properly induce selfish users to participate in spectrum sensing work. In this paper, a new cognitive radio spectrum sharing scheme is developed by employing the trust-based bargaining model. The proposed scheme dynamically adjusts bargaining powers and adaptively shares the available spectrum in real-time online manner. Under widely different and diversified network situations, this approach is so dynamic and flexible that it can adaptively respond to current network conditions. Simulation results demonstrate that the proposed scheme can obtain better network performance and bandwidth efficiency than existing schemes.
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  • Reza SAADAT, Maryam ASADI
    Article type: LETTER
    Subject area: Terrestrial Wireless Communication/Broadcasting Technologies
    2012 Volume E95.B Issue 12 Pages 3929-3932
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    We focus on the cooperative mobile positioning based on the received signal strength for heterogeneous environments. We use the least squares method to estimate the channel attenuation coefficients, and hyperbolic method to determine the position. For increasing accuracy, we use different weighting to the adjacent users' data in the attenuation coefficients estimation.
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  • Xiangdong CHEN, Gwanggil JEON, Jechang JEONG
    Article type: LETTER
    Subject area: Multimedia Systems for Communications
    2012 Volume E95.B Issue 12 Pages 3933-3936
    Published: December 01, 2012
    Released on J-STAGE: December 01, 2012
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    In this letter, an intra-field deinterlacing algorithm based on a gradient inverse weighted filtering (GIWF) interpolator is proposed. The proposed algorithm consists of three steps: We first interpolate the missing line with simple strategies in the working window. Then we calculate the coefficients of the gradient-weighted filters by exploiting the local gray gradients among the neighboring pixels. In the last step, we interpolate the missing line using the proposed GIWF interpolator. Experiments show that the proposed algorithm provides superior performances in terms of both objective and subjective image qualities.
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