International Journal of Antennas and Propagation http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2015 , Hindawi Publishing Corporation . All rights reserved. Advances in Statistical Channel Modeling for Wireless Communications Tue, 24 Mar 2015 07:41:57 +0000 http://www.hindawi.com/journals/ijap/2015/541619/ José F. Paris, Paschalis C. Sofotasios, and Theodoros A. Tsiftsis Copyright © 2015 José F. Paris et al. All rights reserved. Enhancing the Efficiency and Accuracy of MLFMA-PO Hybrid Method for Analyzing Electrically Large Objects Mon, 23 Mar 2015 13:19:34 +0000 http://www.hindawi.com/journals/ijap/2015/826217/ An enhanced hybrid technique combining the multilevel fast multipole algorithm (MLFMA) and the physical optics (PO) is presented for analyzing scattering and radiation by electrically large structures. Based on the previously proposed hybrid technique, an extra octree structure is built for the moment method (MoM) region to accelerate the solving process and an iteration scheme is proposed to further enhance the efficiency compared to the conventional hybrid method. What is more, the modified iterative physical optics (IPO) accelerated by MLFMA technique is adopted to improve the accuracy by simulating complex structures with strong reflections. Numerical results are given to demonstrate the improved accuracy and higher accuracy of the proposed hybrid technique compared to the previous MLFMA-PO method. Hao Ding, Yong Zhang, and Hai Lin Copyright © 2015 Hao Ding et al. All rights reserved. Beamforming and Interference Cancellation in D2D Random Network Mon, 23 Mar 2015 12:27:08 +0000 http://www.hindawi.com/journals/ijap/2015/607563/ Device-to-Device (D2D) communication is an important proximity communication technology. We model the hybrid network of cellular and D2D communication with stochastic geometry theory. In the network, cellular base stations are deployed with multiantennas. Two transmission strategies including beamforming and interference cancellation are proposed to boost system achievable rate in this paper. We derive analytical success probability and rate expression in these strategies. In interference cancellation strategy, we propose the partical BS transmission degrees of freedom (dofs) that can be used to cancel its D2D users (DUEs) interferences around the BS or to boost the desired signal power of associated cellular (CUE). In order to maximize the total area spectral efficiency (ASE), the BS transmission degrees of freedom are allocated according to proper interference cancellation radius around the BS. Monte Carlo simulations are performed to verify our analytical results, and two transmission strategies are compared. Langtao Hu and Chaowei Yuan Copyright © 2015 Langtao Hu and Chaowei Yuan. All rights reserved. On the Effect of Different Grips of Handsets on Data Rate in the Measured Channels Mon, 23 Mar 2015 11:17:05 +0000 http://www.hindawi.com/journals/ijap/2015/593297/ The investigation on the achieved data rate of the cellular system considering different grips of handsets at different frequencies using measurement results of the measurement campaign—which was carried out in the city of Aalborg—is presented in this paper. The achieved data rate of the multiple-input single-output (MISO) interference channel is investigated. A typical propagation environment using two BSs and four handsets, like smart phones, held by four to eight different users was designed and multiple-input multiple-output (MIMO) channels in different scenarios were measured. In this paper, two BSs and two handsets at each measurement time are considered. The impact of the different parameters like correlation, different grips of handsets, and different long term evolution (LTE) frequency bands on the achieved data rate is investigated for different measurements. It could be concluded that the variations in the values of data rate are weakly associated with the different grips of handsets but more correlated with different frequencies. Maryam Rahimi and Ehsan Foroozanfard Copyright © 2015 Maryam Rahimi and Ehsan Foroozanfard. All rights reserved. On the Efficient Generation of -- and -- White Samples with Applications Sun, 22 Mar 2015 13:40:01 +0000 http://www.hindawi.com/journals/ijap/2015/873890/ This paper is concerned with a simple and highly efficient random sequence generator for uncorrelated and variates. The algorithm may yield an efficiency of almost 100%, and this high efficiency can be reached for all special cases such as ,  ,   , Nakagami-m, Nakagami-q, Weibull, Hoyt, Rayleigh, Rice, Exponential, and the One-Sided Gaussian. This generator is implemented via the rejection technique and allows for arbitrary fading parameters. The goodness-of-fit is measured using the Kolmogorov-Smirnov and Anderson-Darling tests. The maximum likelihood parameter estimation for the distribution is proposed and verified against true values of the parameters chosen in the generator. We also provide two important applications for the random sequence generator, the first one dealing with the performance assessment of a digital communication system over the and fading channels and the second one dealing with the performance assessment of the spectrum sensing with energy detection over special cases of these channels. Theoretical and simulation results are compared, validating again the accuracy of the generators. Rausley Adriano Amaral de Souza, Antonio Marcelo Oliveira Ribeiro, and Dayan Adionel Guimarães Copyright © 2015 Rausley Adriano Amaral de Souza et al. All rights reserved. Propagation Measurement on Earth-Sky Signal Effects for High Speed Train Satellite Channel in Tropical Region at Ku-Band Sun, 22 Mar 2015 11:31:31 +0000 http://www.hindawi.com/journals/ijap/2015/270949/ Recent advances in satellite communication technologies in the tropical regions have led to significant increase in the demand for services and applications that require high channel quality for mobile satellite terminals. Determination and quantification of these requirements are important to optimize service quality, particularly in the Malaysian region. Moreover, the tests on current satellite propagation models were carried out at temperate regions whose environmental characteristics are much different from those in Malaysia. This difference renders these propagation models inapplicable and irrelevant to tropical regions in general. This paper presents the link characteristics observations and performance analysis with propagation measurements done in tropical region to provide an accurate database regarding rain and power arches supply (PAs) attenuations in the tropics for mobile scenarios. Hence, an extension for improving the performance assessment and analysis of satellite/transmission has been achieved. The Malaysia propagation measurement for mobile scenario (Malaysia-PMMS) enables first-hand coarse estimation and attenuation analysis, because the attenuation resulting from rain and PAs becomes easily amenable for measurement. Parallel to that, the measured attenuation has been compared with that of the simulated output at noise floor level. The underlying analytical tool is validated by measurements specific at tropical region, for dynamic model of mobile satellite links operating at higher than 10 GHz. Abdulmajeed H. J. Al-Jumaily, A. Sali, J. S. Mandeep, and Alyani Ismail Copyright © 2015 Abdulmajeed H. J. Al-Jumaily et al. All rights reserved. Modeling of the Land Mobile Satellite Channel considering the Terminal’s Driving Direction Sun, 22 Mar 2015 09:26:26 +0000 http://www.hindawi.com/journals/ijap/2015/372124/ A precise characterization of the Land Mobile Satellite (LMS) channel, that is, the channel between a satellite and a mobile terminal, is of crucial importance while designing a satellite-based communication system. State-of-the-art statistical LMS channel models offer the advantage of requiring only a few input parameters, which include the environment type and the elevation angle of the satellite. However, the azimuth angle relative to the driving direction of the mobile terminal is usually ignored, as its proper modeling requires either an extensive measurement campaign or a significant effort from the user, as a precise geometrical description of the scenario is required. In this contribution we show that the impact of the driving direction on the channel statistics is not negligible and requires to be modeled explicitly. Moreover, we propose a statistical LMS channel model whose parameters are obtained via an image-based state estimation method. The image-based method is verified by a comparison with measured radio frequency signal levels. The proposed method allows obtaining a complete statistical description of the channel for arbitrary elevation and azimuth angles. Marie Rieche, Alexander Ihlow, Daniel Arndt, Fernando Pérez-Fontán, and Giovanni Del Galdo Copyright © 2015 Marie Rieche et al. All rights reserved. Tracking- and Scintillation-Aware Channel Model for GEO Satellite to Land Mobile Terminals at Ku-Band Thu, 19 Mar 2015 16:30:45 +0000 http://www.hindawi.com/journals/ijap/2015/392714/ Recent advances in satellite to land mobile terminal services and technologies, which utilize high frequencies with directional antennas, have made the design of an appropriate model for land mobile satellite (LMS) channels a necessity. This paper presents LMS channel model at Ku-band with features that enhance accuracy, comprehensiveness, and reliability. The effect of satellite tracking loss at different mobile terminal speeds is considered for directional mobile antenna systems, a reliable tropospheric scintillation model for an LMS scenario at tropical and temperate regions is presented, and finally a new quality indicator module for different modulation and coding schemes is included. The proposed extended LMS channel (ELMSC) model is designed based on actual experimental measurements and can be applied to narrow- and wide-band signals at different regions and at different speeds and multichannel states. The proposed model exhibits lower root mean square error (RMSE) and significant performance observation compared with the conventional model in terms of the signal fluctuations, fade depth, signal-to-noise ratio (SNR), and quality indicators accompanied for several transmission schemes. Ali M. Al-Saegh, A. Sali, J. S. Mandeep, and Alyani Ismail Copyright © 2015 Ali M. Al-Saegh et al. All rights reserved. Key Considerations in the Modeling of Tropical Maritime Microwave Attenuations Thu, 19 Mar 2015 07:53:17 +0000 http://www.hindawi.com/journals/ijap/2015/246793/ This paper presents some key considerations for modeling of over-sea radio-wave propagations in 5 GHz band. The summarized information is based on a series of measurement campaigns which were recently carried out in the tropical maritime environments near Singapore. Multiray propagations and ducting of radio waves have been highlighted and considered in over-sea path loss modeling and prediction. It is noted that the sea-surface reflection is an important contribution in the received field, while the duct layers could enhance the radio-wave propagations. Our studies also show that the refracted ray inside evaporation duct could be a strong ray for short-range near sea-surface applications and needs to be properly evaluated. Yee Hui Lee and Yu Song Meng Copyright © 2015 Yee Hui Lee and Yu Song Meng. All rights reserved. Adaptive Beamforming Based on Compressed Sensing with Smoothed Norm Wed, 18 Mar 2015 14:36:56 +0000 http://www.hindawi.com/journals/ijap/2015/959856/ An adaptive beamforming based on compressed sensing with smoothed norm for large-scale sparse receiving array is proposed in this paper. Because of the spatial sparsity of the arriving signal, compressed sensing is applied to sample received signals with a sparse array and reduced channels. The signal of full array is reconstructed by using a compressed sensing reconstruction method based on smoothed norm. Then an iterative linearly constrained minimum variance beamforming algorithm is adopted to form antenna beam, whose main lobe is steered to the desired direction and nulls to the directions of interferences. Simulation results and Monte Carlo analysis for linear and planar arrays show that the beam performances of our proposed adaptive beamforming are similar to those of full array antenna. Yubing Han and Jian Wang Copyright © 2015 Yubing Han and Jian Wang. All rights reserved. Small Displacement Detection of Biological Signals Using the Cyclic Frequency Method Sun, 15 Mar 2015 09:40:22 +0000 http://www.hindawi.com/journals/ijap/2015/842123/ A new signal processing method called the Cyclic Frequency method is proposed for small displacement detection of vital signals such as heart rate and respiration using the CW radar method. We have presented experimental results of small displacement detection to confirm the validity of the method. The displacement amplitude 2.5 mm can be detected with a propagation frequency of 24.15 GHz. We may increase the propagation frequency for smaller displacement amplitude or target velocity. Dan Zhang, Masahiko Kurata, and Takayuki Inaba Copyright © 2015 Dan Zhang et al. All rights reserved. Outage-Constrained Beamforming for Two-Tier Massive MIMO Downlink with Pilot Reuse Thu, 12 Mar 2015 13:44:19 +0000 http://www.hindawi.com/journals/ijap/2015/840142/ Massive multiple-input multiple-output (MIMO) systems and small cell networks are both regarded as promising candidates to meet the exponential growth of mobile data traffic for the next generation (5G) wireless communications. Hence, a new kind of multitier networks which combine massive MIMO macro cells with a secondary tier of small cells is proposed to resolve the contradiction of large network coverage and high data rate. In such multitier networks, it is inevitable to allocate nonorthogonal uplink pilot sequences to user equipment (UE) due to the large number of users. We propose a pilot reuse scheme by exploiting the unique architecture of this networks and analyse the special mixed channel state information (CSI) yielded by the pilot reuse scheme. Based on the mixed CSI, we formulate a downlink transmit beamforming problem of minimizing the total power consumption while satisfying the quality of service (QoS) requirements with outage constraints. After decomposing the original problem into simpler subproblems, we provide an efficient algorithm to combine these subproblems and solve them iteratively for generating the beamforming vectors. Monte Carlo simulations show that the average power consumption of the proposed pilot reuse scheme and its associated beamforming algorithm is close to that of the perfect CSI case. Guozhen Xu, An Liu, Wei Jiang, Haige Xiang, and Wu Luo Copyright © 2015 Guozhen Xu et al. All rights reserved. Compact Wake-Up Module Design Based on an Energy-Harvesting Rectenna for Wireless Sensor Receivers Thu, 12 Mar 2015 11:06:46 +0000 http://www.hindawi.com/journals/ijap/2015/976875/ A new compact energy-harvesting module is proposed with compact design techniques. The rectifying circuit eliminates the band-pass filter and matching circuit, based on an active antenna concept and a direct matching technique. For exact circuit impedance, via holes are processed with precise fabrication techniques. The implemented circuit has achieved a circuit size reduction of 76.7%. The proposed system has been applied to a wireless wake-up receiver system with excellent operating performance. Sang-Min Han, Yongwan Lee, Taemin Choi, Seok-Jae Lee, Jung-Woo Baik, Jongsik Lim, and Dal Ahn Copyright © 2015 Sang-Min Han et al. All rights reserved. A Novel Multiband Miniature Planar Inverted F Antenna Design for Bluetooth and WLAN Applications Mon, 09 Mar 2015 06:49:36 +0000 http://www.hindawi.com/journals/ijap/2015/970152/ A novel compact planar inverted F antenna (PIFA) optimized using genetic algorithms for 2.4 GHz (Bluetooth) and 5 GHz (UNII-1, UNII-2, UNII-2 extended, and UNII-3) bands is presented. The patch with a shorting pin is on a  mm3 substrate, which is suspended in air 5 mm above a  mm2 ground plane. Genetic algorithm optimization (GAO) is used to optimize the patch geometry, feed position, and shorting pin position simultaneously. Simulations are carried out by using HFSS and a prototype antenna is fabricated to compare the measurements with the simulations. The antenna shows fractional impedance bandwidths of 4% and 21% and gains of 2.5 dB and 3.2 dB at lower and upper bands, respectively. J. M. Jeevani W. Jayasinghe and Disala Uduwawala Copyright © 2015 J. M. Jeevani W. Jayasinghe and Disala Uduwawala. All rights reserved. Advances in Device-to-Device Communications and Networks Sun, 08 Mar 2015 12:53:24 +0000 http://www.hindawi.com/journals/ijap/2015/279128/ Lingyang Song, Yan Zhang, Stephen Wang, and Cheng-Xiang Wang Copyright © 2015 Lingyang Song et al. All rights reserved. Modeling of a Plasma Antenna with Inhomogeneous Distribution of Electron Density Wed, 04 Mar 2015 10:11:07 +0000 http://www.hindawi.com/journals/ijap/2015/736090/ The distribution of the electron density along a plasma antenna can influence the antenna’s performance. But little has been done in this regard in former studies. In this paper, a model of a practical plasma antenna with an inhomogeneous distribution of electron density is founded according to the transmission-line equivalent theory of a metal monopole, from which the current distribution and the radiation pattern of a plasma antenna with appropriate parameters are calculated. The results show that the electrical current distribution, the maximum radiation direction, and the beamwidth of a plasma antenna vary with electron density distributions. To validate the model, the plasma antenna with the same parameters is also simulated based on electromagnetic software HFSS. It is found that the results from the two ways are almost consistent. Zong-sheng Chen, Li-fang Ma, and Jia-chun Wang Copyright © 2015 Zong-sheng Chen et al. All rights reserved. Wireless Underground Sensor Networks: Channel Modeling and Operation Analysis in the Terahertz Band Wed, 04 Mar 2015 06:58:51 +0000 http://www.hindawi.com/journals/ijap/2015/780235/ Wireless underground sensor networks (WUSNs) are networks of sensor nodes operating below the ground surface, which are envisioned to provide real-time monitoring capabilities in the complex underground environments consisting of soil, water, oil, and other components. In this paper, we investigate the possibilities and limitations of using WUSNs for increasing the efficiency of oil recovery processes. To realize this, millimeter scale sensor nodes with antennas at the same scale should be deployed in the confined oil reservoir fractures. This necessitates the sensor nodes to be operating in the terahertz (THz) range and the main challenge is establishing reliable underground communication despite the hostile environment which does not allow the direct use of most existing wireless solutions. The major problems are extremely high path loss, small communication range, and high dynamics of the electromagnetic (EM) waves when penetrating through soil, sand, and water and through the very specific crude oil medium. The objective of the paper is to address these issues in order to propose a novel communication channel model considering the propagation properties of terahertz EM waves in the complex underground environment of the oil reservoirs and to investigate the feasible transmission distances between nodes for different water-crude-oil-soil-CO2 compositions. Mustafa Alper Akkaş and Radosveta Sokullu Copyright © 2015 Mustafa Alper Akkaş and Radosveta Sokullu. All rights reserved. Frequency Resource Sharing and Allocation Scheme Based on Coalition Formation Game in Hybrid D2D-Cellular Network Tue, 03 Mar 2015 07:17:54 +0000 http://www.hindawi.com/journals/ijap/2015/301932/ A distributed cooperation scheme on frequency resource sharing is proposed to improve the quality of service (QoS) in device-to-device (D2D) communications underlaying cellular networks. Specifically, we formulate the resource allocation problem as a coalition formation game with transferable utility, in which all users have the incentive to cooperate with some others and form a competitive group to maximize the probability of obtaining their favorite spectrum resources. Taking the cost for coalition formation into account, such as the path loss for data sharing, we prove that the core of the proposed game is empty, which shows the impossibility of grand coalition. Hence, we propose a distributed merge-and-split based coalition formation algorithm based on a new defined Max-Coalition order to effectively solve the coalition game. Compared with the exhaustive search, our algorithm has much lower computer complexity. In addition, we prove that stability and convergence of the proposed algorithm using the concept of a defection function. Finally, the simulation results show that the proposed scheme achieves a suboptimal performance in terms of network sum rate compared with the centralized optimal resource allocation scheme obtained via exhaustive search. Qing Ou, Rongqing Zhang, Xi Luan, Yuxin Cheng, Jun Wu, and Jianjun Wu Copyright © 2015 Qing Ou et al. All rights reserved. BDS Multipath Parameter Estimation in the Presence of Impulsive Noise Mon, 02 Mar 2015 10:04:40 +0000 http://www.hindawi.com/journals/ijap/2015/864327/ This study focuses on mitigating the multipath, especially the short-delay multipath of the BeiDou navigation satellite system under impulsive noise conditions. A modified least mean -norm (LMP) algorithm is developed to reduce the convergence time with the same steady-state error by predicting the updating trend of weights. The modified normalized power and the normalized polynomial least mean th power are also directly provided according to a similar principle. According to the research work, an average filter has been utilized to improve the processing gain of designed mitigation scheme. Some significant simulation results verified the performance of the proposed adaption algorithm. Multipath parameter estimation tests have been conducted under different noise levels. Some comparative statistics performance assessments are quantified and verified under impulsive and additional white Gaussian noise environments. Results with various window widths of the average filtering and carrier-to-noise ratios indicate that the proposed scheme is able to improve the performance of the short-delay multipath mitigation under normal and degraded environments. Jicheng Ding, Lin Zhao, Chun Jia, and Zhibin Luo Copyright © 2015 Jicheng Ding et al. All rights reserved. Phantoms for Development of Microwave Sensors for Noninvasive Blood Glucose Monitoring Sun, 01 Mar 2015 14:25:37 +0000 http://www.hindawi.com/journals/ijap/2015/570870/ A suitability of two different liquid phantoms of blood-glucose solutions as phantoms for development of microwave sensors for noninvasive blood glucose monitoring is compared. The two phantoms are physiological saline-glucose and pig blood-glucose solutions. For this purpose a simple microwave sensor is developed for in vitro monitoring of blood glucose levels. The sensor consists of a microstrip antenna and of a small rectangular container on the top of the antenna. The container is filled with one of the liquid phantoms. Both phantoms with different glucose concentrations ranging from 0 to 500 mg/dL are considered. Dependence of sensor’s resonant frequency on glucose concentration of LUTs is both estimated by aid of numerical simulations and measured. The results are discussed and compared with some results reported in the literature. Jan Vrba, Jakub Karch, and David Vrba Copyright © 2015 Jan Vrba et al. All rights reserved. Distributed Joint Cluster Formation and Resource Allocation Scheme for Cooperative Data Collection in Virtual MIMO-Based M2M Networks Sun, 01 Mar 2015 11:15:57 +0000 http://www.hindawi.com/journals/ijap/2015/348086/ An efficient data collection scheme plays an important role for the real-time intelligent monitoring in many machine-to-machine (M2M) networks. In this paper, a distributed joint cluster formation and resource allocation scheme for data collection in cluster-based M2M networks is proposed. Specifically, in order to utilize the advantages of cooperation, we first propose a hierarchical transmission model which contains two communication phases. In the first phase, the intracluster information sharing is carried out by all the nodes within the same cluster. Then these nodes transmit the total information to the BS cooperatively with virtual-MIMO (VMIMO) protocol in the second phase. To grasp the properties and advantages of this cooperative transmission strategy, the theoretical analysis results are provided. The key issue in this system is to form the clusters and allocate resources efficiently. Since the optimization problem on this issue is an NP-hard problem, a feasible joint scheme for the cluster formation and resource allocation is proposed in this paper, which is carried out via coalition formation game with a distributed algorithm. This scheme can reduce the complexity while keeping an attractive performance. Simulation results show the properties of the proposed scheme and its advantages when comparing with the noncooperative scheme for the data collection in a practical scenario. Xi Luan, Jianjun Wu, Yuxin Cheng, and Haige Xiang Copyright © 2015 Xi Luan et al. All rights reserved. Asynchronous Two-Way Relaying Networks Using Distributed Differential Space-Time Coding Sun, 01 Mar 2015 11:14:03 +0000 http://www.hindawi.com/journals/ijap/2015/563737/ A signal detection scheme is proposed for two-way relaying network (TWRN) using distributed differential space-time coding (DDSTC) under imperfect synchronization. Unlike most of existing work, which assumed perfect synchronization and channel state information (CSI) at all nodes, a more realistic scenario is investigated here by considering the signals transmitted from the two source nodes arriving at the relay not exactly at the same time due to the distributed nature of the nodes, and no CSI is available at any node. The proposed signal detection scheme is then demonstrated to remove the imperfect synchronization effect significantly through simulation results. Furthermore, pairwise error probability (PEP) of the asynchronous TWRN is analyzed and derived for both source nodes. Based on the simplified PEP expression, an optimum power allocation (OPA) scheme is then determined to further improve the whole system performance, when neither the source nor the relay has any knowledge of the CSI. Minjie Qian, Yanliang Jin, Zhuo Wu, and Tao Wang Copyright © 2015 Minjie Qian et al. All rights reserved. Chaotic Stream Cipher-Based Secure Data Communications over Intelligent Transportation Network Sun, 01 Mar 2015 11:13:14 +0000 http://www.hindawi.com/journals/ijap/2015/315721/ Intelligent transportation systems (ITS) are advanced applications in which the transportation industry is adapted to the information technology revolution. As an important development direction of ITS, the electronic toll collection (ETC) subsystem, which enables an efficient and speedy toll collection, has gained widespread popularity in the world. In an ETC system, toll transaction data are transmitted over intelligent transportation networks, which is vulnerable to eavesdropping, interfering, and tampering attacks. To address the above security problems, we proposed a chaotic stream cipher-based cryptographic scheme to realise secure data communications over wireless sensor network (WSN), which is a part of ITS. The proposed cryptographic scheme allowed ITS to achieve key negotiation and data encryption between sensor nodes in the WSN, whileas reduced computational costs and power consumption. Security analysis and experimental results showed that the proposed scheme could protect data transmission between wireless sensor nodes from being attacked, and significantly reduced the communication overhead for the whole system compared to the existing ECC_AES scheme, thus satisfying the real-time data transmission requirement of ITS. Wei Zhang, Shanyu Tang, Liping Zhang, Zhao Ma, and Jun Song Copyright © 2015 Wei Zhang et al. All rights reserved. Balancing Long Lifetime and Satisfying Fairness in WBAN Using a Constrained Markov Decision Process Sun, 01 Mar 2015 09:53:47 +0000 http://www.hindawi.com/journals/ijap/2015/657854/ As an important part of the Internet of Things (IOT) and the special case of device-to-device (D2D) communication, wireless body area network (WBAN) gradually becomes the focus of attention. Since WBAN is a body-centered network, the energy of sensor nodes is strictly restrained since they are supplied by battery with limited power. In each data collection, only one sensor node is scheduled to transmit its measurements directly to the access point (AP) through the fading channel. We formulate the problem of dynamically choosing which sensor should communicate with the AP to maximize network lifetime under the constraint of fairness as a constrained markov decision process (CMDP). The optimal lifetime and optimal policy are obtained by Bellman equation in dynamic programming. The proposed algorithm defines the limiting performance in WBAN lifetime under different degrees of fairness constraints. Due to the defect of large implementation overhead in acquiring global channel state information (CSI), we put forward a distributed scheduling algorithm that adopts local CSI, which saves the network overhead and simplifies the algorithm. It was demonstrated via simulation that this scheduling algorithm can allocate time slot reasonably under different channel conditions to balance the performances of network lifetime and fairness. Yingqi Yin, Fengye Hu, Ling Cen, Yu Du, and Lu Wang Copyright © 2015 Yingqi Yin et al. All rights reserved. Capacity Enhancement in 60 GHz Based D2D Networks by Relay Selection and Scheduling Sun, 01 Mar 2015 09:49:52 +0000 http://www.hindawi.com/journals/ijap/2015/205163/ Millimeter-wave or 60 GHz communication is a promising technology that enables data rates in multigigabits. However, its tremendous propagation loss and signal blockage may severely affect the network throughput. In current data-centric device-to-device (D2D) communication networks, the devices with intended data communications usually lay in close proximity, unlike the case in voice-centric networks. So the network can be visualized as a naturally formed groups of devices. In this paper, we jointly consider resource scheduling and relay selection to improve network capacity in 60 GHz based D2D networks. Two types of transmission scenarios are considered in wireless personal area networks (WPANs), intra and intergroup. A distributed receiver based relay selection scheme is proposed for intragroup transmission, while a distance based relay selection scheme is proposed for intergroup transmission. The outage analysis of our proposed relay selection scheme is provided along with the numerical results. We then propose a concurrent transmission scheduling algorithm based on vertex coloring technique. The proposed scheduling algorithm employs time and space division in mmWave WPANs. Using vertex multicoloring, we allow transmitter-receiver () communication pairs to span over more colors, enabling better time slot utilization. We evaluate our scheduling algorithm in single-hop and multihop scenarios and discover that it outperforms other schemes by significantly improving network throughput. Waheed ur Rehman, Tabinda Salam, Jin Xu, and Xiaofeng Tao Copyright © 2015 Waheed ur Rehman et al. All rights reserved. Analog Beamforming and Digital Beamforming on Receive for Range Ambiguity Suppression in Spaceborne SAR Thu, 26 Feb 2015 08:21:47 +0000 http://www.hindawi.com/journals/ijap/2015/182080/ For future spaceborne synthetic aperture radar (SAR) missions, digital beamforming (DBF) on receive in elevation to form a sharp high receive beam will be adopted to improve the signal to noise ratio (SNR) level and suppress range ambiguities. However, in some special cases, range ambiguities may be received by grating lobes with the high receive beam gain, and range ambiguities would not be well suppressed and even may be increased. In this paper, a new receiving approach based on analog beamforming (ABF) and DBF is proposed. According to the spaceborne SAR imaging geometry and the selected pulse repetition frequency (PRF), the antenna patterns of all subapertures of the whole receive antenna in elevation are adjusted by ABF at first. Afterwards, signals from all subapertures in elevation are combined by a real time DBF processor onboard. Since grating lobes could be suppressed by the antenna pattern of the subapertures via ABF, range ambiguities would be well suppressed even if ambiguities are received by grating lobes. Simulation results validate the proposed approach. Pingping Huang and Wei Xu Copyright © 2015 Pingping Huang and Wei Xu. All rights reserved. Circularly Polarized Triband Printed Quasi-Yagi Antenna for Millimeter-Wave Applications Wed, 25 Feb 2015 14:04:09 +0000 http://www.hindawi.com/journals/ijap/2015/329453/ This paper describes the design and development of a triband with circularly polarized quasi-Yagi antenna for ka-band and short range wireless communications applications. The proposed antenna consists of an integrated balun-fed printed dipole, parasitic folded dipole and a short strip, and a modified ground plane. The antenna structure, together with the parasitic elements, is designed to achieve circular polarization and triband operating at resonant frequencies of 13.5 GHz, 30 GHz, and 60 GHz. Antenna design was first simulated using HFSS ver.14, and the obtained results were compared with experimental measurements on a prototype developed on a single printed circuit board. Achieved characteristics include −10 dB impedance bandwidth at the desired bands, circular polarization axial ratio  dB, front to back ratio of 6 dB, gain value of about 4 dBi, and average radiation efficiency of 60%. The paper includes comparison between simulation and experimental results. Dalia M. Elsheakh and Magdy F. Iskander Copyright © 2015 Dalia M. Elsheakh and Magdy F. Iskander. All rights reserved. A Novel CP Horn Antenna with Switchable Polarization by Single Port Feeding Tue, 24 Feb 2015 16:31:44 +0000 http://www.hindawi.com/journals/ijap/2015/562521/ A novel CP horn antenna with switchable polarization by single port feeding is presented. The antenna is composed of a coaxial-waveguide converter and a balance-cavity, a horn, a square-to-circular waveguide transition, and a stepped-septum polarizer, which simplify the feeding and can work on the left-hand or right-hand circular polarizations by manual exchanging the mounting position of the coaxial-waveguide converter and the balance-cavity. The antenna achieves an impedance bandwidth (3.88~5.12 GHz) of 27.5% and a 3 dB-AR (Axial Ratio) bandwidth of 18.6%, with the 3 dB-AR beamwidth of about 149°, and the antenna gain is over 13.3 dB in the available band. Yangzhen Huang, Junping Geng, Xianling Liang, Ronghong Jin, and Xudong Bai Copyright © 2015 Yangzhen Huang et al. All rights reserved. Effects of Metamaterial Slabs Applied to Wireless Power Transfer at 13.56 MHz Tue, 24 Feb 2015 13:45:23 +0000 http://www.hindawi.com/journals/ijap/2015/840135/ This paper analyzes the effects of a metamaterial slab (or a practical “perfect lens”) with negative permeability applied to a two loop magnetically coupled wireless power transfer (WPT) system at 13.56 MHz, based on theory, full-wave electromagnetic- (EM-) simulations, and measurements. When using lossless slabs with ideal negative permeability in EM-simulations, the WPT efficiencies have been found to be enhanced close to 100% due to the magnetic field focusing. For the case of using a realistic slab made of ring resonators (RR) with (s: slab width, d: distance between the transmitting and receiving loops), the WPT efficiency has been found to significantly decrease to about 20%, even lower than that of a free space case (32%) due to the heavy power absorption in the slab. However, some efficiency enhancement can be achieved when is optimized between 0.1 and 0.3. Overall, the significant enhancement of efficiencies when using a lossless slab becomes moderate or only marginal when employing a realistic slab. Gunyoung Kim, Taek-Kyu Oh, and Bomson Lee Copyright © 2015 Gunyoung Kim et al. All rights reserved. A Bandpass Filter Based on Half Mode Substrate Integrated Waveguide-to-Defected Ground Structure Cells Mon, 23 Feb 2015 07:22:49 +0000 http://www.hindawi.com/journals/ijap/2015/969035/ A half mode substrate integrated waveguide-to-defected ground structure (HMSIW-DGS) cell and its embedded form are proposed to miniaturize a bandpass filter. Both cells can purchase wideband frequency response and low insertion loss, as well as simple and easy fabrication. By cascading two of them according to design requirement, an X-band bandpass filter is designed and measured to meet compact size, low insertion loss, good return loss, second harmonic suppression, and linear phase. Yong Mao Huang, Zhenhai Shao, Zhaosheng He, Chang Jiang You, and Di Jiang Copyright © 2015 Yong Mao Huang et al. All rights reserved.