IEICE Transactions on Communications
Online ISSN : 1745-1345
Print ISSN : 0916-8516
Volume E94.B, Issue 5
Displaying 1-50 of 58 articles from this issue
Special Section on Antenna and Propagation Technologies Contributing to Diversification of Wireless Technologies
  • Toshikazu HORI
    2011 Volume E94.B Issue 5 Pages 1125
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    Download PDF (83K)
  • Kamya YEKEH YAZDANDOOST, Kamran SAYRAFIAN-POUR, Kiyoshi HAMAGUCHI
    Article type: INVITED PAPER
    2011 Volume E94.B Issue 5 Pages 1126-1134
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL FREE ACCESS
    Wireless body area network for sensing and monitoring of vital signs is the one of most rapidly growing wireless communication system and Ultra Wide-Band (UWB) is a favorable technology for wearable medical sensors. The wireless body area networks promise to revolutionize health monitoring. However, designers of such systems face a number of challenging tasks. Efficient transceiver design requires in-depth understanding of the propagation media which in this case is the human body surface. The human body is not an ideal medium for RF wave transmission; it is partially conductive and consists of materials of different dielectric constants, thickness and characteristic impedance. The results of the few measurement experiments in recent publications point to varying conclusions in the derived parameters of the channel model. As obtaining large amount of data for many scenarios and use-cases is difficult for this channel, a detailed simulation platform can be extremely beneficial in highlighting the propagation behavior of the body surface and determining the best scenarios for limited physical measurements. In this paper, an immersive visualization environment is presented, which is used as a scientific instrument that gives us the ability to observe three-dimensional RF propagation from wearable medical sensors around a human body. We have used this virtual environment to further study UWB channels over the surface of a human body. Parameters of a simple statistical path-loss model and their sensitivity to frequency and the location of the sensors on the body are discussed.
    Download PDF (3701K)
  • Uisheon KIM, Jaehoon CHOI
    Article type: INVITED PAPER
    2011 Volume E94.B Issue 5 Pages 1135-1141
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL FREE ACCESS
    This paper proposes a microstrip patch antenna for 2.45GHz Industrial Scientific Medical (ISM) band Wireless Body Area Network (WBAN) applications. To enhance the front-to-back ratio (F/B) and specific absorption rate (SAR), an electrically coupled LC resonator is introduced. The overall dimensions of the proposed antenna are 54mm × 45mm × 2.4mm and it has a gain of over 1dBi for the entire 2.45GHz ISM band. The proposed antenna has an enhanced F/B ratio and specific absorption rate, compared with those of a conventional patch antenna.
    Download PDF (2050K)
  • Tie Jun CUI, Xiao-Yang ZHOU, Xin Mi YANG, Wei Xiang JIANG, Qiang CHENG ...
    Article type: INVITED PAPER
    2011 Volume E94.B Issue 5 Pages 1142-1152
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL FREE ACCESS
    We present a review of several types of microwave antennas made of metamaterials, including the resonant electrically small antennas, metamaterial-substrate patch antennas, metamaterial flat-lens antennas, and Luneburg lens antennas. In particular, we propose a new type of conformal antennas using anisotropic zero-index metamaterials, which have high gains and low sidelobes. Numerical simulations and experimental results show that metamaterials have unique properties to design new antennas with high performance.
    Download PDF (6239K)
  • Tanawut TANTISOPHARAK, Akkarat BOONPOONGA, Chuwong PHONGCHAROENPANICH, ...
    Article type: INVITED PAPER
    2011 Volume E94.B Issue 5 Pages 1153-1160
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL FREE ACCESS
    This paper proposes an adaptive antenna using a combination of on-off and CMA algorithms. With the proposed technique, the on-off algorithm is first employed to search for a desired signal direction in which maximum received power is achieved. Then, interference is suppressed by performing CMA. Simulations are conducted according to the potential application of the proposed adaptive antenna. The simulation results show the SINR improvement implying that the proposed adaptive antenna can be applied to microwave RFID systems in order to resolve reader collision. Furthermore, the proposed adaptive antenna is implemented and then experimented. The experimental results verify that the proposed adaptive antenna can reduce interference resulting in the collision problem.
    Download PDF (1172K)
  • Jun ITOH, Nguyen TUAN HUNG, Hisashi MORISHITA
    Article type: PAPER
    Subject area: Antennas and Antenna Measurement
    2011 Volume E94.B Issue 5 Pages 1161-1167
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    In this study, we propose a method to reduce the mutual coupling between two J-shaped folded monopole antennas (JFMAs), which cover the IEEE 802.11 b/g (2400-2484MHz) band. First, the change in mutual coupling with the spacing between the two antenna elements is investigated by considering two feeding models, and the effects of changes in the coupling on the antenna efficiency are studied. Subsequently, we try the method to reduce mutual coupling, the method involves the use of a bridge line that links the two antennas. The mutual coupling can be significantly reduced and the total antenna efficiency can be improved by linking two shorting strips with the bridge line. In a past study, we had found that in the case of L-shaped folded monopole antennas (LFMAs), the mutual coupling and antenna efficiency vary with the linking location on the bridge line. Moreover, we compare the characteristics of the LFMA and JFMA and show that the JFMA is effective when miniaturized.
    Download PDF (1544K)
  • Mio NAGATOSHI, Shingo TANAKA, Satoru HORIUCHI, Hisashi MORISHITA
    Article type: PAPER
    Subject area: Antennas and Antenna Measurement
    2011 Volume E94.B Issue 5 Pages 1168-1173
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    Various planar folded dipole antennas with feed lines are introduced and analyzed. With the added feed line, the planar folded dipole antenna has two resonance modes. Moreover, adjusting the spacing and width of the feed line improves the broadband characteristics of the antenna. The attached feed line has not only an impedance transforming characteristic but also a bandwidth transforming characteristic. The bandwidth transforming characteristic means that the feed line can broaden the bandwidth of folded dipole antenna. A way to reduce the antenna area is also studied, and the characteristics of the resulting compact antenna are analyzed.
    Download PDF (1758K)
  • Nozomu ISHII
    Article type: PAPER
    Subject area: Antennas and Antenna Measurement
    2011 Volume E94.B Issue 5 Pages 1174-1183
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    EIRP measurement in the direction of maximum radiation has not always been valid to estimate the radiated power from radio equipments integrated with antennas, for example, integrated radiator with antennas shaped like the notebook-sized PC. Therefore, it is recommended that total radiated power (TRP) from equipment under test (EUT) should be estimated by integrating measured EIRPs on the whole surface of the unit sphere. In this paper, a conventional and some novel sampling methods for the TRP estimation, which were proposed to reduce the number of measurement points, are examined by using a measured EIRP data set and compared with each other. For a simulated radio equipment shaped like a notebook-sized PC, it is found that the equi-area and generalized spiral points methods are superior to the equi-angle method in terms of reducing the number of the measurement points and orthogonal three planes method is another candidate in terms of saving measurement time unless the pattern radiated from EUT is not so complicated.
    Download PDF (2476K)
  • Kazuyuki SEO, Kunio SAKAKIBARA, Nobuyoshi KIKUMA
    Article type: PAPER
    Subject area: Antennas and Antenna Measurement
    2011 Volume E94.B Issue 5 Pages 1184-1193
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    Many kinds of microstrip array antennas have been developed in the millimeter-wave band. In order to avoid feeding loss and the decrease of antenna gain by beam shift due to frequency changes, center-fed array antennas are advantageous. In this case, the element spacing around the feeding circuit of the transition from the waveguide to two microstrip lines is larger than one wavelength. Therefore, the sidelobe level grows significantly. In order to suppress the sidelobe level, we propose transitions with slot radiators. Moreover, any polarization angles can be achieved by changing the slot angle. A wide variety from 1.5% to 70% of slot radiator coupling powers can be achieved. To investigate the performance of the proposed transition, 10, 22 and 30-element center-fed microstrip comb-line antennas with the proposed transition were developed at 76.5GHz, and measured performance was evaluated in the millimeter-wave band.
    Download PDF (2908K)
  • Fuminori SAKAI, Kazuo OHTA, Kunio SAWAYA
    Article type: PAPER
    Subject area: Antennas and Antenna Measurement
    2011 Volume E94.B Issue 5 Pages 1194-1200
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    A UWB impulse array antenna (IAA) utilizing a novel electrical scanning system with tapped delay lines is proposed and its usefulness is experimentally verified. The experimental antenna is composed of impulse generators installed in each antenna element and tapped delay lines used for creating transmitting trigger signals, which is a simple circuit configuration. It is shown that the output phase of the transmitting wave can be controlled by controlling the period of the trigger signal, and beam direction can be controlled from -30deg to +30deg by changing the trigger frequency from Fc -2kHz to Fc+2kHz. Evaluation of this antenna as a short range radar is carried out and distance resolution of 25cm and angle resolution below 10deg are obtained.
    Download PDF (2153K)
  • Hiroyoshi YAMADA, Hiroshi SAKAI, Yoshio YAMAGUCHI
    Article type: PAPER
    Subject area: Antennas and Antenna Measurement
    2011 Volume E94.B Issue 5 Pages 1201-1206
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    High resolution direction-of-arrival (DOA) estimation algorithm for array antennas becomes popular in these days. However, there are several error factors such as mutual coupling among the elements in actual array. Hence array calibration is indispensable to realize intrinsic performance of the algorithm. In the many applications, it is preferable that the calibration can be done in the practical environment in operation. In such a case, the incident wave becomes coherent multipath wave. Calibration of array in the multipath environment is a hard problem, even when DOA of elementary waves is known. To realize array calibration in the multipath environment will be useful for some applications even if reference signals are required. In this report, we consider property of reference waves in the multipath environment and derive a new calibration technique by using the multipath coherent reference waves. The reference wave depends on not only the DOA but also complex amplitude of each elementary wave. However, the proposed technique depends on the DOA only. This is the main advantage of the technique. Simulation results confirm the effectiveness of the proposed technique.
    Download PDF (623K)
  • Yi WANG, Kenji ITO, Yoshio KARASAWA
    Article type: PAPER
    Subject area: MIMO Propagation
    2011 Volume E94.B Issue 5 Pages 1207-1214
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    This paper presents a Multiple-Input Multiple-Output (MIMO) propagation model for independent and identically distributed (i.i.d.) channels in the mixture of none-Line-of-Sight (NLOS) and Line-of-Sight (LOS) environments. The derived model enables to evaluate the system statistical characteristics of Signal-to-Noise-Ratio (SNR) for MIMO transmission based on Maximal Ratio Combing (MRC). An application example applying the model in 2×2 configuration to ITS Inter-Vehicle Communication (IVC) system is introduced. We clarify the effectiveness of the proposed model by comparisons of both computer simulations and measurement results of a field experiment. We also use the model to show the better performance of SNR when applying MIMO to IVC system than SISO and SIMO.
    Download PDF (1364K)
  • Tetsuki TANIGUCHI, Yoshio KARASAWA, Makoto TSURUTA
    Article type: PAPER
    Subject area: MIMO Propagation
    2011 Volume E94.B Issue 5 Pages 1215-1224
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    This paper gives statistical analysis of double fading channels which are typically found in keyhole MIMO (multiple input multiple output) models. First, to investigate the potential of identically distributed double Nakagami-Rice MIMO keyhole channels including LOS (line of sight) environment, the density function of SNR (signal to noise ratio) which corresponds to the only one non-zero eigenvalue of channel correlation matrix is presented. In addition to the exact expression with an infinite series form, an approximation formula with a simple monomial form derived by substituting Nakagami m formula for Rician distribution is also considered. Next, similar equations are introduced for double Rayleigh channels which have correlated branches in both the transmitter and receiver sides (independent but nonidentical case is included here). Through computer simulations, the effectiveness of the proposed formulae is verified, and in double Nakagami-Rice fading case, the advantage of the approximated formula particularly for large array size and/or large Rician factor is demonstrated.
    Download PDF (1165K)
  • Dalin ZHANG, Mitoshi FUJIMOTO, Toshikazu HORI
    Article type: PAPER
    Subject area: Adaptive Array Antennas
    2011 Volume E94.B Issue 5 Pages 1225-1233
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    This paper proposes a novel blind multiuser detection scheme using CMA (Constant Modulus Algorithm) adaptive array. In the proposed scheme, the received signal is processed in two steps. In the primary step, only one user is captured by the CMA adaptive array, and at the same time, the other users' directions of arrival (DOA) are estimated. In the secondary step, initial weight vectors are set based on the estimated DOAs, and it processes with CMAs again to capture the other users in parallel. Thus, all the users are detected exactly and recovered separately. The Least-squares CMA is applied as an optimization algorithm to improve the performance of the proposed scheme, and the performances using the proposed scheme with linear arrays and circular arrays are discussed in detail. Simulation results are presented to verify the performance of the proposed scheme.
    Download PDF (1676K)
  • Abdul Malik NAZARI, Yukihiro KAMIYA, Ko SHOJIMA, Kenta UMEBAYASHI, Yas ...
    Article type: PAPER
    Subject area: Adaptive Array Antennas
    2011 Volume E94.B Issue 5 Pages 1234-1242
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    Hop-timing detection is of extreme importance for the reception of frequency hopping (FH) signals. Any error in the hop-timing detection has a deleterious effect on the performance of the receiver in frequency hopping (FH) communication systems. However, it is not easy to detect the hop-timing under low signal to noise power ratio (SNR) environments. Adaptive array antennas (AAA) have been expected to improve the performance of FH communication systems by beamforming for the direction of arrival of the desired signal. Since the conventional AAA exploits at least the coarse synchronization for dehopping of FH signals before achieving the beamforming, any fault in the hop-timing detection causes the deterioration of the performance of AAA. Using AAA based on the constant modulus algorithm (CMA), this paper proposes a new method for blind beamforming and hop-timing detection for FH signals. The proposed method exploits both the spatial and temporal characteristics of the received signal to accomplish the beamforming and detect the hop-timing without knowing any a priori information such as fine/coarse time synchronization and training signal. The performance verifications of the proposed method based on pertinent simulations are presented.
    Download PDF (899K)
  • Kentaro NISHIMORI, Rocco DI TARANTO, Hiroyuki YOMO, Petar POPOVSKI
    Article type: PAPER
    Subject area: Radio System
    2011 Volume E94.B Issue 5 Pages 1243-1253
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    This paper discusses the possibility of deploying a short-range cognitive radio (secondary communication system) within the service area of a primary system. Although the secondary system interferes with the primary system, there are certain locations in the service area of the primary system where the cognitive radio can reuse the frequency of the primary system without causing harmful interference to it and being disturbed by the primary system. These locations are referred to as having a spatial opportunity for communications in the secondary system, since it can reuse the frequency of the primary system. Simulation results indicate that the antenna gain, beamwidth, and propagation path loss greatly affect the spatial opportunity of frequency reuse for the secondary users. The results show that spatial spectrum reuse can be significantly increased when the primary system users are equipped with directional antennas. An important component in this study is the heterogeneous path loss model, i.e., the path loss model within the primary system is different from the model used to calculate the interference between the primary and the secondary systems. Our results show that the propagation models corresponding to the actual antenna heights in the primary/secondary system can largely impact the possibilities for spectrum reuse by the cognitive radios.
    Download PDF (1942K)
  • Wenshan YIN, Pinyi REN, Zhou SU, Ruijuan MA
    Article type: PAPER
    Subject area: Radio System
    2011 Volume E94.B Issue 5 Pages 1254-1264
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    Multiple antenna is introduced into spectrum sensing in cognitive radios recently. However, conventional multiple antenna spectrum sensing schemes exploited only space diversity. In this paper, we propose a new multiple antenna sensing scheme based on space and time diversity (MASS-BSTD). First, the primary user signal to be sensed is over-sampled at each antenna, and signal samples collected at the same time instant from different antennas are stacked into a column vector. Second, each column vector is utilized to estimate space correlation matrix that exploits space diversity, and two consecutive column vectors are utilized to estimate time correlation matrix that exploits time diversity. Third, the estimated space correlation matrix and time correlation matrix are combined and analyzed using eigenvalue decomposition to reduce information redundancy of signals from multiple antennas. Lastly, the derived eigenvalues are utilized to construct the test statistic and sense the presence of the primary user signal. Since the proposed MASS-BSTD exploits both space diversity and time diversity, it achieves performance gain over the counterparts that only exploit space diversity. Furthermore, the proposed MASS-BSTD requires no prior information on the primary user, the channel between primary user transmitter and secondary user receiver, and is robust to noise uncertainty. Theoretical analysis and simulation results show that the proposed MASS-BSTD can sense the presence of primary user signal reliably.
    Download PDF (786K)
  • Yichen WANG, Pinyi REN, Zhou SU
    Article type: PAPER
    Subject area: Radio System
    2011 Volume E94.B Issue 5 Pages 1265-1275
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    Utilizing available channels to improve the network performance is one of the most important targets for the cognitive MAC protocol design. Using antenna technologies is an efficient way to reach this target. Therefore, in this paper, we propose a novel cognitive MAC protocol, called Polarization-based Long-range Communication Directional MAC Protocol (PLRC-DMAC), for Cognitive Ad Hoc Networks (CAHNs). The proposed protocol uses directional antennas to acquire better spatial reuse and establish long-range communication links, which can support more nodes to access the same channel simultaneously. Moreover, the PLRC-DMAC also uses polarization diversity to allow nodes in the CAHN to share the same channel with Primary Users (PUs). Furthermore, we also propose a Long-range Orientation (LRO) algorithm to orient the long-range nodes. Simulation results show that the LRO algorithm can accurately orient the long-range nodes, and the PLRC-DMAC can significantly increase the network throughput as well as reduce the end-to-end delay.
    Download PDF (528K)
  • QuocDinh NGUYEN, Naobumi MICHISHITA, Yoshihide YAMADA, Koji NAKATANI
    Article type: LETTER
    Subject area: Antennas
    2011 Volume E94.B Issue 5 Pages 1276-1279
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    For the easy design of very small normal-mode helical antennas (NMHAs), an equation that helps determine the self-resonant structures of these antennas is developed. For this purpose, the expression for the capacitance of an NMHA is established. The accuracy of this design equation is confirmed by comparing the results obtained using the equation with the simulation results.
    Download PDF (449K)
  • Hiroshi HIRAYAMA, Gen MATSUI, Nobuyoshi KIKUMA, Kunio SAKAKIBARA
    Article type: LETTER
    Subject area: Antennas
    2011 Volume E94.B Issue 5 Pages 1280-1283
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    A new structure to improve channel capacity of short-range MIMO is proposed. The proposed structure consists of back reflector and side reflector. FDTD simulation demonstrates a role of back reflector and side reflector. The back reflector increases all eigen values. The side reflector equalizes eigen value distribution. Consequently, the proposed structure enhances the channel capacity.
    Download PDF (693K)
  • Dazhi PIAO, Guizhen LU, Zhixing YANG
    Article type: LETTER
    Subject area: MIMO Propagation
    2011 Volume E94.B Issue 5 Pages 1284-1287
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    The polarization degrees of freedom (DOF) of the hexapolarized multiple input multiple output (MIMO) system over the ground reflected channel is studied in this paper by the deterministic field solution. Using the simple two-ray model, we could get some basic understandings for the influence of a single reflecting surface on the polarization DOF of the multipolarized MIMO system. Computation results show that the number of parallel independent channels in a multipolarized MIMO system depends mainly on the communication range and the height of antennas. In free space transmission, with equal height of transmitter and receiver antennas, large polarization DOF value only occurs in the near field case and it drops sharply to 2 with the increase of transmission range. Whereas for the ground reflect channel, there will be a polarization DOF larger than 4 occurring at longer communication distance with an unequal transmitter and receiver antenna height.
    Download PDF (251K)
Regular Section
  • Kazutomo KOBAYASHI, Yukio TAKAHASHI, Hiroyuki TAKADA
    Article type: PAPER
    Subject area: Fundamental Theories for Communications
    2011 Volume E94.B Issue 5 Pages 1288-1294
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    Admission control is a procedure to guarantee a given level of Quality of Service (QoS) by accepting or rejecting arrival connection requests. There are many studies on backlog or loss rate evaluation formulas for admission control at a single node. However, there are few studies on end-to-end evaluation formulas suitable for admission control. In a previous paper, the authors proposed a new stochastic network calculus for many flows using an approach taken from large deviations techniques and obtained asymptotic end-to-end evaluation formulas for output burstiness and backlog. In this paper, we apply this stochastic network calculus to a heterogeneous tandem network with many forwarding flows and cross traffic flows constrained by leaky buckets, and obtain a simple evaluation formula for the end-to-end backlog. In this formula, the end-to-end backlog can be evaluated by the traffic load at the bottle neck node. This result leads us to a natural extension of the evaluation formula for a single node.
    Download PDF (471K)
  • Anmin FU, Yuqing ZHANG, Jingyu FENG
    Article type: PAPER
    Subject area: Fundamental Theories for Communications
    2011 Volume E94.B Issue 5 Pages 1295-1302
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    The recent IEEE 802.16j-2009 adds multi-hop relay capabilities to IEEE 802.16 systems, which aims to offer improved coverage and capacity over single-hop radio access systems. In this paper, we point out several security issues, including non-authenticated privacy and key management messages, insecure relay multicast rekeying algorithm and insecure Multicast and Broadcast Rekeying Algorithm (MBRA), of the key management protocols in IEEE 802.16j-2009 and give some solutions. In particular, we propose a new Secure MBRA (SMBRA) based on identity and logical key tree to solve the security issues of MBRA. SMBRA can not only provide backward and forward secrecy of communications but also avoid key forgery. Furthermore, our theoretical analysis and simulation indicate that SMBRA is much more efficient and adequate, especially in a large group.
    Download PDF (810K)
  • Toshiya MATSUDA, Takeshi KAWASAKI, Tomoyoshi KATAOKA, Akira NAKA, Kazu ...
    Article type: PAPER
    Subject area: Fiber-Optic Transmission for Communications
    2011 Volume E94.B Issue 5 Pages 1303-1310
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    We propose a polarization mode dispersion (PMD) design for high-speed wavelength-division multiplexing (WDM) backbone network systems based on field PMD measurements on installed optical fibers for long-term commercial use. Implementing a high-speed network system on an installed fiber requires measuring PMD, because the PMD characteristics of most installed fibers are unknown. For enhanced practicality, we must be able to precisely evaluate PMD characteristics precisely with just one measurement. To understand the statistical properties of measured PMD values, we use the Jones Matrix Eigenanalysis (JME) method to conduct long-term (12 months) PMD measurements on installed fibers. We statistically analyze the measurement results and confirm that the measured values match the theory that considers the accuracy of the measurement instrument. This enables a PMD design of desired outage probability based on PMD measurements of installed fibers. We also carry out a 43-Gb/s return-to-zero differential quadrature phase shift keying (RZ-DQPSK) signal transmission with high PMD fibers in order to confirm the effectiveness of our PMD design. The PMD values of the in-line amplifier transmission line are settled so as to meet the worst value of the design. We confirm that 43-Gb/s RZ-DQPSK signals are stably transmitted at the design value.
    Download PDF (833K)
  • Yukio HAYASHI, Yasumasa ONO
    Article type: PAPER
    Subject area: Network
    2011 Volume E94.B Issue 5 Pages 1311-1322
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    For realistic scale-free networks, we investigate the traffic properties of stochastic routing inspired by a zero-range process known in statistical physics. By parameters α and δ, this model controls degree-dependent hopping of packets and forwarding of packets with higher performance at more busy nodes. Through a theoretical analysis and numerical simulations, we derive the condition for the concentration of packets at a few hubs. In particular, we show that the optimal α and δ are involved in the trade-off between a detour path for α < 0 and long wait at hubs for α > 0; In the low-performance regime at a small δ, the wandering path for α < 0 better reduces the mean travel time of a packet with high reachability. Although, in the high-performance regime at a large δ, the difference between α > 0 and α < 0 is small, neither the wandering long path with short wait trapped at nodes (α = -1), nor the short hopping path with long wait trapped at hubs (α = 1) is advisable. A uniformly random walk (α = 0) yields slightly better performance. We also discuss the congestion phenomena in a more complicated situation with packet generation at each time step.
    Download PDF (918K)
  • Pa HSUAN, Chyi-Ren DOW, Kuen-Chu LAI, Pei-Jung LIN, Shiow-Fen HWANG
    Article type: PAPER
    Subject area: Network
    2011 Volume E94.B Issue 5 Pages 1323-1331
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    To provide convenient wireless access, wireless mesh networks (WMNs) can be rapidly deployed and connected for mobile clients. Although route redirection traffic control schemes and dynamic routing metrics can be used to improve the performance of WMNs, more of the available network bandwidth will be consumed by control message exchange. This paper proposes a capacity-aware and multipath supported traffic control framework in WMNs. The proposed framework can be used to dispatch data traffic in a multipath manner to improve the utilization of wireless links and forwarding latency. A hierarchical queue architecture is proposed to monitor and classify network traffic without the effort of control message exchange. Our traffic control strategy, which is based on local minimization of the forwarding latency, consists of two phases to automatically adapt to the utilization rate of the network links. In the first phase, the incoming packets are dispatched to the lower level queues according to the Internet gateway capacity. In the second phase, the packets are dispatched to the related network links according to the link load. The current study implements the proposed traffic control system on NS2 for simulation and on Linux 2.6 for real traffic analysis. Experimental results show that the proposed framework improves the throughput and reduces forwarding delay with an approximate minimum delay time. The results also show that the behavior of the long-term delay model can be applied to short-term traffic control methods in WMNs.
    Download PDF (1109K)
  • Chang-Seok CHOI, Hyo-Jin AHN, Hanho LEE
    Article type: PAPER
    Subject area: Network
    2011 Volume E94.B Issue 5 Pages 1332-1338
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    This paper presents a high-throughput low-complexity four-parallel Reed-Solomon (RS) decoder for high-rate WPAN systems. Four-parallel processing is used to achieve 12-Gbps data throughput and low hardware complexity. Also, the proposed pipelined folded Degree-Computationless Modified Euclidean (fDCME) algorithm is used to implement the key equation solver (KES) block, which provides low hardware complexity for the RS decoder. The proposed four-parallel RS decoder is implemented 90-nm CMOS technology optimized for a 1.2V supply voltage. The implementation result shows that the proposed RS decoder can be operated at a clock frequency of 400MHz and has a data throughput 12.8-Gbps. The proposed four-parallel RS decoder architecture has high data processing rate and low hardware complexity. Therefore it can be applied in the FEC devices for next-generation high-rate WPAN systems with data rate of 10-Gbps and beyond.
    Download PDF (1350K)
  • Takeshi YAGI, Naoto TANIMOTO, Takeo HARIU, Mitsutaka ITOH
    Article type: PAPER
    Subject area: Internet
    2011 Volume E94.B Issue 5 Pages 1339-1347
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    Vulnerabilities in web applications expose computer networks to security threats. For example, attackers use a large number of normal user websites as hopping sites, which are illegally operated using malware distributed by abusing vulnerabilities in web applications on these websites, for attacking other websites and user terminals. Thus, the security threats, resulting from vulnerabilities in web applications prevent service providers from constructing secure networking environments. To protect websites from attacks based on the vulnerabilities of web applications, security vendors and service providers collect attack information using web honeypots, which masquerade as vulnerable systems. To collect all accesses resulting from attacks that include further network attacks by malware, such as downloaders, vendors and providers use high-interaction web honeypots, which are composed of vulnerable systems with surveillance functions. However, conventional high-interaction web honeypots can collect only limited information and malware from attacks, whose paths in the destination URLs do not match the path structure of the web honeypot since these attacks are failures. To solve this problem, we propose a scheme in which the destination URLs of these attacks are corrected by determining the correct path from the path structure of the web honeypot. Our Internet investigation revealed that 97% of attacks are failures. However, we confirmed that approximately 50% of these attacks will succeed with our proposed scheme. We can use much more information with this scheme to protect websites than with conventional high-interaction web honeypots because we can collect complete information and malware from these attacks.
    Download PDF (642K)
  • Hui SHEN, Bin LIN, Yi LUO, Feng LIU
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2011 Volume E94.B Issue 5 Pages 1348-1354
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    In this paper, we propose a new interference alignment (IA) scheme that jointly designs the linear transmitter and receiver for the 2-user MIMO X channel system, using minimum total mean square error criterion, subject to each transmitter power constraint. We show that transmitters and receivers under such criteria could be realized through a joint iterative algorithm. Considering the imperfection of channel state information (CSI), we also extend the minimum mean square error interference alignment schemes for the MIMO X channel with CSI estimation error. A robust iterative algorithm which is insensitve to CSI estimation error is proposed. Simulation results are also provided to demonstrate the proposed algorithm.
    Download PDF (550K)
  • Nguyen H. TRAN, Choong Seon HONG, Sungwon LEE
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2011 Volume E94.B Issue 5 Pages 1355-1365
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    The aggregate throughput of wireless mesh networks (WMNs) can be significantly improved by equipping the mesh routers with multiple radios tuned to orthogonal channels. Not only the links using orthogonal channels can be activated at a time, but some links in the same channel also can be activated concurrently if the Signal-to-Interference-and-Noise Ratio (SINR) at their receivers is not lower than the threshold, which is the spatial-reuse characteristic. STDMA is considered as one of the medium access schemes that can exploit spatial reuse to improve network throughput. Past studies have shown that optimizing the performance of STDMA is NP-Hard. Therefore, we propose a STDMA-based scheduling algorithm that operates in a greedy fashion for WMNs. We show that the proposed algorithm enhances not only the throughput but also the fairness by capturing the essence of spatial-reuse approach of STDMA and giving medium access opportunities to each network element based on its priority. We furthermore validate our algorithm through theoretical analysis and extensive simulations and the results show that our algorithm can outperform state-of-the-art alternatives.
    Download PDF (742K)
  • Tatsunori OBARA, Kazuki TAKEDA, Fumiyuki ADACHI
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2011 Volume E94.B Issue 5 Pages 1366-1375
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    Frequency-domain equalization (FDE) based on minimum mean square error (MMSE) is considered as a promising equalization technique for a broadband single-carrier (SC) transmission. When a square-root Nyquist filter is used at a transmitter and receiver to limit the signal bandwidth, the presence of timing offset produces the inter-symbol interference (ISI) and degrades the bit error rate (BER) performance using MMSE-FDE. In this paper, we discuss the mechanism of the BER performance degradation in the presence of timing offset. Then, we propose joint MMSE-FDE & spectrum combining which can make use the excess bandwidth introduced by transmit filter to achieve larger frequency diversity gain while suppressing the negative effect of the timing offset.
    Download PDF (1852K)
  • Maduranga LIYANAGE, Iwao SASASE
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2011 Volume E94.B Issue 5 Pages 1376-1385
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    Quantization is an important operation in digital communications systems. It not only introduces quantization noise but also changes the statistical properties of the quantized signal. Furthermore, quantization noise cannot be always considered as an additive source of Gaussian noise as it depends on the input signal probability density function. In orthogonal-frequency-division-multiplexing transmission the signal undergoes different operations which change its statistical properties. In this paper we analyze the statistical transformations of the signal from the transmitter to the receiver and determine how these effect the quantization. The discussed process considers the transceiver parameters and the channel properties to model the quantization noise. Simulation results show that the model agrees well with the simulated transmissions. The effect of system and channel properties on the quantization noise and its effect on bit-error-rate are shown. This enables the design of a quantizer with an optimal resolution for the required performance metrics.
    Download PDF (568K)
  • Tetsuya YAMAMOTO, Kazuki TAKEDA, KyeSan LEE, Fumiyuki ADACHI
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2011 Volume E94.B Issue 5 Pages 1386-1395
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    Recently, assuming ideal brick-wall transmit filtering, we proposed a frequency-domain block signal detection (FDBD) with maximum likelihood detection employing QR decomposition and M-algorithm (called QRM-MLD) for the reception of single-carrier (SC) signals transmitted over a frequency-selective fading channel. QR decomposition (QRD) is applied to a concatenation of the propagation channel and discrete Fourier transform (DFT). However, a large number of surviving paths is required in the M-algorithm to achieve sufficiently improved bit error rate (BER) performance. The introduction of filtering can achieve improved BER performance due to larger frequency diversity gain while keeping a lower peak-to-average power ratio (PAPR) than orthogonal frequency division multiplexing (OFDM). In this paper, we develop FDBD with QRM-MLD for filtered SC signal reception. QRD is applied to a concatenation of transmit filter, propagation channel, and DFT. We evaluate BER and throughput performances by computer simulation. From performance evaluation, we discuss how the filter roll-off factor affects the achievable BER and throughput performances and show that as the filter roll-off factor increases, the required number of surviving paths in the M-algorithm can be reduced.
    Download PDF (1282K)
  • Kazuki TAKEDA, Fumiyuki ADACHI
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2011 Volume E94.B Issue 5 Pages 1396-1404
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    In this paper, we propose a novel iterative transmit/receive equalization technique for single-carrier (SC) block transmission in a severe frequency-selective fading channel. Iterative frequency-domain inter-symbol interference (ISI) cancellation (FDIC) is introduced to the previously proposed joint iterative transmit/receive frequency-domain equalization (FDE) based on the minimum mean square error (MMSE) criterion. 1-tap FDE is employed at the transmitter. At the receiver, a 1-tap FDE and FDIC are jointly used and they are updated in an iterative manner. The transmit FDE weight is derived based on the MMSE criterion by taking into account the reduction of residual ISI in the receiver. To derive the weight, the transmitter assumes that the receiver can partially reduce the residual ISI after the FDIC. We conduct a computer simulation to investigate the achievable bit error rate (BER) performance to confirm the effectiveness of our proposed technique.
    Download PDF (1013K)
  • Kan ZHENG, Hang LONG, Fangxiang WANG, Wenbo WANG
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2011 Volume E94.B Issue 5 Pages 1405-1415
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    Simple half-duplex repetition-based relaying protocols can achieve spatial diversity at the expense of additional relaying signals in the time domain. In this paper, a linear unitary precoder based on a singular vector for cooperative systems with the amplify-and-forward (AF) relaying protocol is proposed in order to improve spectral efficiency. An exact expression of the precoder design is first derived for the case of equal power allocation. Then, water-filling power allocation is used in conjunction with the precoder to further increase the system capacity, where the precoder matrix is generated with an iterative process. From the implementation point of view, the channel state information (CSI) has to be estimated and quantized in systems, the detail of which is described in the sequel. The adaptive modulation and coding (AMC) technique with the proposed precoder is also discussed to achieve high throughput performance. Finally, numerical and simulation results are presented to demonstrate the effectiveness of the proposed technique in improving capacity and throughput.
    Download PDF (1056K)
  • Xiang-bin YU, Quan KUANG, Qing-min MENG, Shu-hung LEUNG
    Article type: PAPER
    Subject area: Wireless Communication Technologies
    2011 Volume E94.B Issue 5 Pages 1416-1423
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    In this paper, an optimal power control for minimizing bit error rate (BER) subject to a power constraint for space-time block coded MIMO systems with beamforming over Rayleigh fading channels under imperfect channel state information (CSI) is presented. The optimal power control procedure is developed. It is shown that the Lagrange multiplier for the constrained optimization does exist and is unique. To simplify the power control procedure, a closed-form suboptimal power control scheme is drived based on the asymptotic performance analysis of the optimal power control and Taylor's series expansion. The calculation of the suboptimal power control is straightforward with low computational complexity. Moreover, the suboptimal scheme can provide the BER performance close to that of the optimal power control and is lower than that of the existing suboptimal scheme. Simulation results show that the proposed two power control schemes can provide BER lower than that of the equal power allocation and the existing suboptimal scheme under imperfect CSI.
    Download PDF (486K)
  • Sang Hyuk KANG
    Article type: PAPER
    Subject area: Terrestrial Wireless Communication/Broadcasting Technologies
    2011 Volume E94.B Issue 5 Pages 1424-1431
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    We consider wireless interactive data broadcasting environments consisting of the broadcast channel for data dissemination and the communication channels for client requests. Modeling client impatience as the soft deadline of client requests, we propose a broadcast scheduling based on a combination of periodic scheduling and priority-based scheduling. The server partitions data items into hot and cold-item sets according to the optimized cut-off point. We apply periodic and priority-based scheduling to hot and cold item sets, respectively, in order to maximize the average utility of the items. We investigate the optimized cut-off point by analyzing the average utility of items as a function of the cut-off point. Simulation results show that our proposed algorithm outperforms existing methods in various circumstances in terms of average utility as well as average response time.
    Download PDF (390K)
  • Kenichi MIZUGAKI, Tatsuo NAKAGAWA, Ryosuke FUJIWARA, Shinsuke KOBAYASH ...
    Article type: PAPER
    Subject area: Sensing
    2011 Volume E94.B Issue 5 Pages 1432-1437
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    An original asynchronous Ultra Wideband — Impulse Radio (UWB-IR) wireless location system for sensor network is developed and evaluated through experiments. The system enables wireless nodes to be located and communicated with simultaneously at low power and low cost. The proposed system does not need system synchronization. Each access point of the proposed location system measures the time difference between two signals' received timing: one is from target node, and the other is from an access point, the position of which is already known. Then the position of the target nodes is calculated by a pseudo Time Difference of Arrival (TDOA) method. We first introduce the system configuration and asynchronous TDOA method adopted in this system. Next, we estimate the received-signal-timing measurement accuracy of UWB-IR signal and evaluate it in experiments using prototype UWB-IR transceivers. Then we estimate the location accuracy by the horizontal dilution of precision (HDOP) metric and show the field trial results of using the prototype UWB-IR location system.
    Download PDF (738K)
  • Hyun-Seok RYU, Jun-Seok LEE, Chung-Gu KANG
    Article type: LETTER
    Subject area: Transmission Systems and Transmission Equipment for Communications
    2011 Volume E94.B Issue 5 Pages 1438-1441
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    We provide a BER analysis of the well-known rotation code, which has been applied to various transmission schemes, such as coordinate-interleaved design (CID) for space-time block codes and trans-modulation or constellation rearrangement for a cooperative relay system. An upper bound on the BER of the rotation code under a fading channel is derived. It turns out to be much tighter than the existing one, which relies on the Chernoff bound. More specifically, the proposed bound is virtually identical to simulation result when Eb/No is larger than 4dB.
    Download PDF (204K)
  • Yong LI, Depeng JIN, Li SU, Lieguang ZENG
    Article type: LETTER
    Subject area: Network
    2011 Volume E94.B Issue 5 Pages 1442-1446
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    Due to the lack of end-to-end paths between the communication source and destination, the routing of Delay Tolerant Networks (DTN) exploits the store-carry-and-forward mechanism. This mechanism requires nodes with sufficient energy to relay and forward messages in a cooperative and selfless way. However, in the real world, the energy is constrained and most of the nodes exhibit selfish behaviors. In this paper, we investigate the performance of DTN routing schemes considering both the energy constraint and selfish behaviors of nodes. First, we model the two-hop relay and epidemic routing based on a two-dimensional continuous time Markov chain. Then, we obtain the system performance of message delivery delay and delivery cost by explicit expressions. Numerical results show that both the energy constraint and node selfishness reduce the message delivery cost at the expense of increasing the message delivery delay. Furthermore, we demonstrate that the energy constraint plays a more important role in the performance of epidemic routing than that of two-hop relay.
    Download PDF (585K)
  • Yun Won CHUNG, Ji Hoon KIM
    Article type: LETTER
    Subject area: Network
    2011 Volume E94.B Issue 5 Pages 1447-1451
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    In the vehicular ad hoc network (VANET), broadcast is used to disseminate emergency warning messages (EWM) in public safety applications and delay is one of the most stringent requirements. Although flooding is the simplest broadcast scheme, it introduces a broadcast storm problem, and numerous broadcast protocols have been proposed forVANET in order to improve the performance of broadcast. In this letter, we analyze the tradeoff between two location-based broadcast protocols, i.e., distance-based relay selection (DBRS) and range-based relay selection (RBRS) schemes under various vehicular densities. Then, we propose a dynamic broadcast scheme, which selects an appropriate scheme from DBRS and RBRS, based on the estimation of vehicle density. The results of a performance analysis show that the proposed scheme dynamically selects the better scheme for varying vehicle density.
    Download PDF (208K)
  • Hyun Jong KIM, Seong Gon CHOI
    Article type: LETTER
    Subject area: Network
    2011 Volume E94.B Issue 5 Pages 1452-1455
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    We propose a scheduling method called SCQ (Smoothly Changing Queue) which can control service rate by bulk size of video streaming services such as IPTV and VoD. Since SCQ allows queue length to change smoothly, video streaming services can be stably provided with low jitter. Queueing analysis results show that SCQ can more stably deliver video streaming with low jitter and loss than existing AQMs or queue length-based rate control methods.
    Download PDF (834K)
  • Thuc KIEU-XUAN, Insoo KOO
    Article type: LETTER
    Subject area: Network
    2011 Volume E94.B Issue 5 Pages 1456-1459
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    This letter proposes a novel decision fusion algorithm for cooperative spectrum sensing in cognitive radio sensor networks where a reinforcement learning algorithm is utilized at the fusion center to estimate the sensing performance of local spectrum sensing nodes. The estimates are then used to determine the weights of local decisions for the final decision making process that is based on the Chair-Vashney optimal decision fusion rule. Simulation results show that the sensing accuracy of the proposed scheme is comparable to that of the Chair-Vashney optimal decision fusion based scheme even though it does not require any knowledge of prior probabilities and local sensing performance of spectrum sensing nodes.
    Download PDF (348K)
  • SangWoo LEE, Seon-Ho SHIN, MyungKeun YOON
    Article type: LETTER
    Subject area: Network Management/Operation
    2011 Volume E94.B Issue 5 Pages 1460-1462
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    A new network measurement primitive was recently proposed, known as long duration flows (LDF). LDF deserves special attention for network management and security monitoring. This kind of traffic appears periodically and persistently through a long period, but its total amount of traffic is not necessarily large. This feature makes detection difficult especially when the resources of detection system are limited or the detection should cover high-speed networks. In this paper, we propose a new lightweight data structure and streaming algorithm to detect such traffic.
    Download PDF (78K)
  • Sai-Wing LEUNG, Kwok-Hung CHAN, Chi-Kit TANG
    Article type: LETTER
    Subject area: Electromagnetic Compatibility (EMC)
    2011 Volume E94.B Issue 5 Pages 1463-1466
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    Owing to the concerns about electromagnetic interference (EMI) from wireless local area networks (WLAN), an investigation into its impact on medical equipment is carried out. The results indicate that there is no evidence of 802.11 Wireless LAN systems being unsafe for installation inside hospital premises and only one piece of equipment was found to be susceptible to IEEE 802.11b standard.
    Download PDF (1082K)
  • Yu TAKASE, Osamu MUTA, Yoshihiko AKAIWA
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2011 Volume E94.B Issue 5 Pages 1467-1471
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    A major drawback in OFDM systems is that the transmit-signal exhibits a high Peak-to-Average Power Ratio (PAPR) which causes nonlinear distortion at the output of power amplifier. To achieve high efficiency in OFDM systems, it is important to suppress PAPR of the transmit signal. In IEEE802.16e (mobile WiMAX) based systems, it is desirable to employ a simple PAPR reduction method such as clipping & filtering (C&F) or peak windowing (PW). The purpose of this paper is to evaluate PAPR reduction performance of C&F and PW and compare them in an IEEE802.16e based OFDM system. In addition, we also show a repeated PW method which reduces PAPR by repeatedly applying a smooth window function to the transmit signal. Computer simulation results show that the repeated PW can achieve almost the same PAPR reduction performance as that of the repeated C&F with significantly lower computational complexity.
    Download PDF (583K)
  • Xiaofeng WAN, Yu ZHANG, Zhixing YANG
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2011 Volume E94.B Issue 5 Pages 1472-1475
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    A zig-zag Gardner algorithm with parallel architecture is presented in this letter. This algorithm performs timing adjustment in each individual burst independently for high speed wireless burst communication with a short guard. Over sampling data are stored in RAM initially and read forward and backward alternately later. The proposed algorithm has distinct symmetric characteristic in the forward and backward process, which makes the alternate sequences achieve nearly the same effect as a continuous sequence. The performance of the proposed algorithm is very close to the theoretical curve.
    Download PDF (235K)
  • Jin REN, Sukhui LEE, Seokhyun YOON
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2011 Volume E94.B Issue 5 Pages 1476-1482
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    Recent works on MIMO receiver design were mainly focused on sphere decoding, which provides a trade-off between the performance and complexity by suitably choosing the “radius” or the number of candidates in the search space. Meanwhile, another approach, called poly-diagonalization and trellis detection, has been proposed to compromise the complexity and performance. In this paper, we compare various MIMO receiver algorithms in terms of both performance and complexity. The performance is evaluated in a frequency selective fading channel environment on the basis of orthogonal frequency division multiplexing with channel coding, for which the generation of soft decision values is crucial. The simulations show that the poly-diagonalization approach matches the performance of sphere decoding at similar computational complexity.
    Download PDF (327K)
  • Jinglei LI, Qinghai YANG, Kyung Sup KWAK, Fenglin FU
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2011 Volume E94.B Issue 5 Pages 1483-1486
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    In this letter, an AGV based relay selection mechanism is developed to ensure relays reporting true information in wireless relay networks. The source selects relays based on the channel state information (CSI) of relay-destination links. Selfish relays may report fake CSI in order to obtain a better chance of being selected, whereas the source is not able to tell the reported in real or in false. In the proposed scheme, a relay node receives some payoffs from the destination with respect to the achievable data rate and also some compensations from the others in terms of the reported CSI of all relays. This mechanism not only enforces truth-telling upon relay nodes with maximum payoff but also ensures fairness among them. The equilibrium of payoff is attained when relay nodes report their true CSI. Simulation results demonstrate the theoretical solutions.
    Download PDF (173K)
  • Joontae KIM, Dong-Jo PARK
    Article type: LETTER
    Subject area: Wireless Communication Technologies
    2011 Volume E94.B Issue 5 Pages 1487-1490
    Published: May 01, 2011
    Released on J-STAGE: May 01, 2011
    JOURNAL RESTRICTED ACCESS
    We analyze linear channel estimation for MIMO-OFDM systems and propose a spherical linear interpolator in closed-form for the beamforming codewords. We also suggest a hybrid interpolator using a simplified version of the derived interpolator. Simulation results show that the proposed schemes are efficient and competitive with respect to the feedback overhead and have low complexity.
    Download PDF (183K)
feedback
Top