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PHYSICS (557 journals)            First | 1 2 3 4 5 6 | Last

Open Journal of Fluid Dynamics     Open Access   (Followers: 3)
Open Journal of Microphysics     Open Access  
Optical Communications and Networking, IEEE/OSA Journal of     Hybrid Journal   (Followers: 4)
Optofluidics, Microfluidics and Nanofluidics     Open Access  
Organic Electronics     Hybrid Journal   (Followers: 3)
Organic Photonics and Photovoltaics     Open Access   (Followers: 2)
PAJ: A Journal of Performance and Art     Hybrid Journal   (Followers: 11)
Particle Physics Insights     Open Access   (Followers: 2)
Particuology     Hybrid Journal  
Pattern Recognition in Physics     Open Access   (Followers: 1)
Pergamon Materials Series     Full-text available via subscription  
Phase Transitions and Critical Phenomena     Full-text available via subscription   (Followers: 1)
Philosophical Magazine     Hybrid Journal   (Followers: 2)
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences     Full-text available via subscription   (Followers: 5)
Philosophy and Foundations of Physics     Full-text available via subscription  
Physica B: Condensed Matter     Hybrid Journal   (Followers: 5)
physica status solidi (a)     Hybrid Journal   (Followers: 1)
physica status solidi (b)     Hybrid Journal   (Followers: 1)
physica status solidi (c)     Hybrid Journal   (Followers: 1)
Physica Status Solidi - Rapid Research Letters     Hybrid Journal   (Followers: 1)
Physical Communication     Hybrid Journal  
Physical Review C     Full-text available via subscription   (Followers: 18)
Physical Review Special Topics - Physics Education Research     Open Access   (Followers: 6)
Physical Review X     Open Access   (Followers: 6)
Physical Sciences Data     Full-text available via subscription   (Followers: 1)
Physics - spotlighting exceptional research     Full-text available via subscription   (Followers: 1)
Physics and Chemistry of Glasses - European Journal of Glass Science and Technology Part B     Full-text available via subscription   (Followers: 2)
Physics and Chemistry of Liquids: An International Journal     Hybrid Journal   (Followers: 2)
Physics and Chemistry of the Earth, Parts A/B/C     Hybrid Journal   (Followers: 3)
Physics and Materials Chemistry     Open Access  
Physics Essays     Full-text available via subscription  
Physics in Medicine & Biology     Full-text available via subscription   (Followers: 9)
Physics in Perspective     Hybrid Journal   (Followers: 1)
Physics International     Open Access   (Followers: 2)
Physics Letters A     Hybrid Journal   (Followers: 10)
Physics Letters B     Open Access   (Followers: 3)
Physics of Fluids     Hybrid Journal   (Followers: 24)
Physics of Life Reviews     Hybrid Journal   (Followers: 1)
Physics of Plasmas     Hybrid Journal   (Followers: 6)
Physics of the Dark Universe     Open Access  
Physics of the Solid State     Hybrid Journal   (Followers: 3)
Physics of Wave Phenomena     Hybrid Journal   (Followers: 1)
Physics Procedia     Partially Free   (Followers: 1)
Physics Reports     Full-text available via subscription   (Followers: 2)
Physics Research International     Open Access   (Followers: 1)
Physics Today     Hybrid Journal   (Followers: 28)
Physics World     Full-text available via subscription   (Followers: 3)
Physics-Uspekhi     Full-text available via subscription  
Physik in unserer Zeit     Hybrid Journal  
Physik Journal     Hybrid Journal  
Plasma Physics Reports     Hybrid Journal   (Followers: 2)
Pramana     Open Access   (Followers: 9)
Preview     Hybrid Journal  
Proceedings of the National Academy of Sciences     Full-text available via subscription   (Followers: 530)
Proceedings of the National Academy of Sciences, India Section A     Hybrid Journal   (Followers: 3)
Progress in Materials Science     Hybrid Journal   (Followers: 20)
Progress in Planning     Hybrid Journal   (Followers: 1)
Progress of Theoretical and Experimental Physics     Open Access  
Quantum Electronics     Full-text available via subscription   (Followers: 3)
Quantum Measurements and Quantum Metrology     Open Access  
Quantum Studies : Mathematics and Foundations     Hybrid Journal  
Quarterly Journal of Mechanics and Applied Mathematics     Hybrid Journal   (Followers: 3)
Radiation Effects and Defects in Solids     Hybrid Journal   (Followers: 1)
Radiation Measurements     Hybrid Journal   (Followers: 2)
Radiation Physics and Chemistry     Hybrid Journal   (Followers: 1)
Radiation Protection Dosimetry     Hybrid Journal   (Followers: 2)
Radiation Research     Full-text available via subscription   (Followers: 3)
Radio Science     Full-text available via subscription   (Followers: 3)
Radiological Physics and Technology     Hybrid Journal   (Followers: 1)
Reflets de la physique     Full-text available via subscription  
Reports on Mathematical Physics     Full-text available via subscription  
Reports on Progress in Physics     Full-text available via subscription   (Followers: 2)
Research & Reviews : Journal of Physics     Full-text available via subscription  
Research in Drama Education     Hybrid Journal   (Followers: 11)
Research Journal of Physics     Open Access  
Results in Physics     Open Access   (Followers: 1)
Reviews in Mathematical Physics     Hybrid Journal  
Reviews of Accelerator Science and Technology     Hybrid Journal  
Reviews of Geophysics     Full-text available via subscription   (Followers: 19)
Reviews of Modern Physics     Full-text available via subscription   (Followers: 17)
Revista Colombiana de Física     Open Access  
Revista Mexicana de Astronomía y Astrofísica     Open Access  
Revista Mexicana de Física     Open Access  
Revista mexicana de física E     Open Access  
Rheologica Acta     Hybrid Journal   (Followers: 3)
Russian Journal of Mathematical Physics     Hybrid Journal  
Russian Journal of Nondestructive Testing     Hybrid Journal   (Followers: 1)
Russian Physics Journal     Hybrid Journal  
Samuel Beckett Today/Aujourd'hui     Full-text available via subscription   (Followers: 2)
Science and Technology of Nuclear Installations     Open Access   (Followers: 1)
Science China : Physics, Mechanics & Astronomy     Full-text available via subscription   (Followers: 1)
Science Foundation in China     Full-text available via subscription   (Followers: 2)
Scientific Journal of Physical Science     Open Access  
Scientific Reports     Open Access   (Followers: 10)
Selected Topics in Applied Earth Observations and Remote Sensing, IEEE Journal of     Hybrid Journal   (Followers: 17)
Sensor Letters     Full-text available via subscription   (Followers: 1)
Sensors and Actuators A: Physical     Hybrid Journal   (Followers: 56)
Services Computing, IEEE Transactions on     Hybrid Journal   (Followers: 3)
Shock and Vibration     Hybrid Journal   (Followers: 7)
Shock Waves     Hybrid Journal   (Followers: 4)

  First | 1 2 3 4 5 6 | Last

Journal Cover   Physical Communication
  [SJR: 1.326]   [H-I: 13]   Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1874-4907
   Published by Elsevier Homepage  [2589 journals]
  • An overview of shadowed fading wireless channels in terms of a cascaded
    • Abstract: Publication date: Available online 24 February 2015
      Source:Physical Communication
      Author(s): P.M. Shankar
      Wireless channels suffer from short term fading and shadowing simultaneously. While simple models of short term fading are based on the Nakagami-m distribution, short term fading can also be described as a cascading process allowing the modeling of wireless channels having worse fading than what exists in Nakagami-m channels. Shadowing, on the other hand, has been traditionally modeled as a lognormal process, making the analysis of shadowed fading channels cumbersome. Taking note of the fact that the lognormal density arises out of a multiplicative process, it was shown that shadowing can also be modeled as a cascading process. Utilizing such a vision of shadowing, this work provides an overview of a unified cascaded approach to model wireless channels when short term fading and shadowing are simultaneously present. The degradation in such shadowed fading channels is estimated in terms of error rates and outage probabilities. Results are compared to those of the exact model based on lognormal density as well as random number simulation. Analysis demonstrates that error rates and outage probabilities obtained using the exact model (lognormal model for shadowing) agree very well with those obtained through the composite cascaded model as well as random number simulations.

      PubDate: 2015-02-27T05:38:22Z
  • The combination of QoS, Aggregation and RTS/CTS in Very High Throughput
           IEEE 802.11ac Networks
    • Abstract: Publication date: Available online 10 February 2015
      Source:Physical Communication
      Author(s): Oran Sharon , Yaron Alpert
      We consider a single WiFi cell in which multiple mobile stations transmit multiple QoS constrained Application flows to the Access Point. We investigate the efficiency of using RTS/CTS in the face of the QoS constraints, in various Access Categories that are defined in the WiFi standard, in different number of transmitting stations and in various amounts of aggregation. We show that using RTS/CTS is efficient in terms of Throughput, when there are collisions and the time to recover these collisions is within the Delay/Loss constraints of the Application flows. It turns out that RTS/CTS is most efficient in the Video and Voice Access Categories and Delay constrains in the order of several tens of mili-seconds. For smaller Delay constraints it is more efficient without RTS/CTS. Thus, we show the existence of cross-points: In Delay constraints smaller than the cross points it is more efficient without RTS/CTS and beyond the cross-points the opposite is true.

      PubDate: 2015-02-14T02:19:59Z
  • Enhanced satellite communication model associated with fuzzy channel
    • Abstract: Publication date: Available online 10 February 2015
      Source:Physical Communication
      Author(s): Kamal Harb , Omair Butt , Samir Abdul-Jauwad
      Wireless channel prediction and impairment estimations have always been a popular area for research. Therefore, a composite model for channel induced impairments on satellite communication systems operating at frequencies above 10 GHz has been presented in this paper. Such systems show a high dependency on varying propagation characteristics due to often occurring dust and sand ( DUSA ) storms in the first channel (desert area), and due to rain impairments in the second channel (tropical region). Furthermore, the presented simulations for DUSA storms are based on varying levels of visibility at different altitudes along with the non-uniform DUSA particles distribution. Three-dimensional relationships are then presented for these attenuations with different weather parameters such as visibility, DUSA particles size, rainfall rate ( RR ), frequency, location, and propagation angle, to provide the proposed system with an enhanced view of satellite’s parameters. Finally, this paper proposes Enhanced Weather Alert Control Scheme ( EWACS ), which supports Decision Support System ( DSS ), that can provide the system with more flexibility by adaptively controlling different combinations of modulation, coding, radio signal strength, frame size configuration, and data rate. This system acts to improve QoS and provides an immense support to the designer for dynamic reconfiguration of the operational satellite system parameters under different weather conditions.

      PubDate: 2015-02-14T02:19:59Z
  • Novel selective OFDM-based cooperative techniques for multi-hop systems
    • Abstract: Publication date: Available online 30 January 2015
      Source:Physical Communication
      Author(s): A. Gouissem , M.O. Hasna , R. Hamila
      In multi-hop systems, the theoretical outage probabilities and diversity orders of novel Orthogonal Frequency Division Multiplexing (OFDM) based Decode and Forward (DF) cooperative techniques are derived for different methods that manipulate the subcarriers in order to improve the performance, while overcoming practical implementation issues and using limited number of relays. First, the outage probability of the Basic Selective OFDM technique is derived for a multi-hop system without the high SNR approximations, and the effect of joint selection in the last two hops is investigated. Then, Subcarrier Ordering technique (SO) is introduced and proved its efficiency in substituting the error correction at the intermediate hops while reducing the computation complexity. Furthermore, we propose alike efficient cooperative methods making use of subcarrier mapping to trade-off between outage performance and practical implementation problems. We also analyze the computation complexity of the different algorithms and we prove that, at high SNR, the proposed Improved Selective OFDMA reduces the complexity by up to N (Number of subcarriers) times without affecting the outage performance when compared to Selective OFDMA.

      PubDate: 2015-02-03T00:43:45Z
  • Orthogonal space time block coding over dirty paper channel: Outage
           capacity analysis
    • Abstract: Publication date: Available online 30 January 2015
      Source:Physical Communication
      Author(s): Zouhair Al-qudah
      We analytically prove that the outage capacity of the multiple input multiple output (MIMO) which is affected by interference, that is non-causally available as well as the channel state information (CSI) for all users at the transmitter, has the free interference outage capacity. Specifically, Orthogonal space time block coding (O-STBC) with two transmit antennas and arbitrary number of receive antennas is used for transmission and reception. We modify the random variable U which was proposed by Costa (1983) to account for the availability of the CSI at both the transmitter and receiver. Further, we use lattice dirty paper coding (DPC) to show that an interference free channel capacity can be achieved in the MIMO-OSTBC system. First, we derive the equivalent noise seen by the receiver using an equivalent lattice based dirty paper code. Then the optimal value of the power inflation factor is derived. Next, the channel capacity of the equivalent modulo lattice channel is computed. Finally, performance results in the case of various number of receive antennas are presented and show that significant reduction in frame error probabilities can be obtained over a system that uses no interference cancelation.

      PubDate: 2015-02-03T00:43:45Z
  • Including general environmental effects in K-factor approximation for
           rice-distributed VANET channels
    • Abstract: Publication date: Available online 5 January 2015
      Source:Physical Communication
      Author(s): Craig Cooper , Abhinay Mukunthan , Farzad Safaei , Montserrat Ros , Daniel Franklin , Mehran Abolhasan
      This paper presents a method of approximating the Ricean K-factor based on the instantaneous static environment. The strongest signal propagation paths are resolved in order to determine specular and diffuse powers for approximation. The model is experimentally validated in two different urban areas in New South Wales, Australia. Good agreement between the model and experimental data was obtained over short-range communication links, demonstrating the suitability of the model in urban VANETs. The paper concludes with recommendations for methods to account for vehicles in the simulation and incorporating additional phenomena (such as scattering) in the approximation.

      PubDate: 2015-01-09T02:01:05Z
  • Signal detection enhancement in LTE-a downlink physical layer using
           OSIC-based K-Best algorithm
    • Abstract: Publication date: Available online 27 December 2014
      Source:Physical Communication
      Author(s): M.G. El-Mashed , S. El-Rabaie
      In this paper, the performance of LTE-A downlink physical layer with MIMO detection techniques is presented. We propose a scalable and near optimum OSIC-based K -Best algorithm with higher performance. The proposed OSIC-based K -Best algorithm is characterized by low complexity by dividing a large MIMO detection problem into small sub-problems. The proposed algorithm is divided into several basic building blocks with small dimension to reduce complexity. This algorithm utilizes the K -Best algorithm for first data stream with high SINR, and then applies an OSIC-MMSE to detect the other data streams. This paper investigates the performance of the proposed algorithm and compares its performance with the other algorithms. The performance of the proposed algorithm is mathematically illustrated and evaluated by calculating the BER for a certain range of SNRs with different antennas cases. Simulation results show that the proposed algorithm provides a better performance and gives low BER values. Finally, the OSIC-based K -Best algorithm enhances the performance of the LTE-A downlink physical layer.

      PubDate: 2014-12-28T01:33:08Z
  • Bit error rate of RS coded BFSK in broadband powerline channels with
           background nakagami and impulsive noise
    • Abstract: Publication date: Available online 10 December 2014
      Source:Physical Communication
      Author(s): Aniruddha Chandra , Anirban Chattopadhyay , Kalyan Sharma , Sanjay Dhar Roy
      Power line communication (PLC) systems are being standardized over the globe and some of these standards recommended frequency shift keying (FSK) as their modulation choice. Broadband transmission over a PLC channel is mainly affected by the ever-present background noise and the occasional high-amplitude impulses. It has been recently found that the background noise in PLC can be suitably modelled with Nakagami- m distribution while a standard model for characterizing impulses is to assume Gaussian distributed amplitude and Poisson distributed arrivals. Considering such a model, at first, simple analytical bit error rate (BER) expressions of uncoded binary FSK (BFSK) signals are derived in the paper. The derived expressions are simple, involve only elementary functions, and the analytical BER values match perfectly with computer simulations. Next, a unified analytical framework is presented for evaluating BER when a Reed Solomon (RS) code is used to mitigate the noise effects. The results reveal that when the signal to background noise ratio (SBNR) is low, there is a clear impact of the noise parameter m and the choice of demodulation method (coherent/ non-coherent) on the error performance of the coded system. On the contrary, at higher SBNR, impulsive noise dominates over background noise, and these effects vanish as the BER curves become flat. Numerical evaluations dictated that by allowing a lower code rate ( 0.7 ) this error floor may be reduced significantly (up to 1 0 − 15 ). Further, the code gain of the system was found to be an inverse function of the code rate and codeword length.

      PubDate: 2014-12-14T07:29:37Z
  • Optimization for distributed Radar Sensor Network (RSN) and MIMO-RSN in
           flat fading channels
    • Abstract: Publication date: December 2014
      Source:Physical Communication, Volume 13, Part C
      Author(s): Yang Liu , Jing Liang
      Investigation in distributed Radar Sensor Network (RSN) and MIMO-RSN are more like two parallel paths other than one research field in current literature. In this paper, we address the comparison between optimal fusion scheme of distributed-RSN and optimal power control of MIMO-RSN for target detection. We first establish the wireless statistic channel model for these two types of RSNs under flat fading channel condition. Using Jake’s model, Rayleigh flat fading channel is obtained. Then we provide optimization for the fusion scheme and the power control. Both amplitude and phase of the received signals are applied to the optimal/suboptimal fusion schemes for the distributed-RSN. Water-filling, the optimal power control scheme is utilized in the MIMO-RSN, where two suboptimal schemes (equal power and channel inversion) are also investigated to provide a comparison. The detection performance is analyzed and compared in terms of probability of detection ( P d ) and probability of false alarm ( P f a ). The simulation results show that the water-filling in MIMO-RSN achieves the best performance, whereas the optimal fusion scheme for distributed-RSN obtains worse performance than the equal power control in MIMO-RSN, and the channel inversion in MIMO-RSN gets the worst performance, which has almost the same performance as the suboptimal fusion scheme in distributed-RSN.

      PubDate: 2014-12-06T06:56:06Z
  • Sense-through-wall human detection using the UWB radar with sparse SVD
    • Abstract: Publication date: December 2014
      Source:Physical Communication, Volume 13, Part C
      Author(s): Xiaoyang Li , Qilian Liang , Francis C.M. Lau
      In this paper, a method for through-wall human detection based on the singular values decomposition of the measurement matrices is presented. After demonstrating the sparsity of the matrices using the CLEAN algorithm, an SVD algorithm based on the Lanczos process is applied to compute their singular values. We also analyze the singular values of matrices constructed by difference square techniques for different types of walls and compare our algorithm with a 2-D imaging approach proposed by researchers in Time Domain Company. Detection results show that our method performs well in the gypsum wall, brick wall, and wooden door.

      PubDate: 2014-12-06T06:56:06Z
  • Editorial Board
    • Abstract: Publication date: December 2014
      Source:Physical Communication, Volume 13, Part C

      PubDate: 2014-12-06T06:56:06Z
  • Radar sensor network for target detection using Chernoff information and
           relative entropy
    • Abstract: Publication date: December 2014
      Source:Physical Communication, Volume 13, Part C
      Author(s): Ishrat Maherin , Qilian Liang
      In this paper, we propose to apply information theory to Ultra wide band (UWB) radar sensor network (RSN) to detect target in foliage environment. Information theoretic algorithms such as Maximum entropy method (MEM) and mutual information are proven methods, that can be applied to data collected by various sensors. However, the complexity of the environment poses uncertainty in fusion center. Chernoff information provides the best error exponent of detection in Bayesian environment. In this paper, we consider the target detection as binary hypothesis testing and use Chernoff information as sensor selection criterion, which significantly reduces the processing load. Another strong information theoretic algorithm, method of types, is applicable to our MEM based target detection algorithm as entropy is dependent on the empirical distribution only. Method of types analyzes the probability of a sequence based on empirical distribution. Based on this, we can find the bound on probability of detection. We also propose to use Relative entropy based processing in the fusion center based on method of types and Chernoff Stein Lemma. We study the required quantization level and number of nodes in gaining the best error exponent. The performance of the algorithms were evaluated, based on real world data.

      PubDate: 2014-12-06T06:56:06Z
  • Synthetic Aperture Radar image nonlinear enhancement algorithm based on
           NSCT transform
    • Abstract: Publication date: December 2014
      Source:Physical Communication, Volume 13, Part C
      Author(s): Ying Tong , Meirong Zhao , Zilong Wei , Leilei Liu
      Due to the imaging mechanism, Synthetic Aperture Radar (SAR) images are susceptible to speckle noise, which affects radar image interpretation. So image denoising and enhancement are important topics of improving SAR image performance. A nonlinear image enhancement algorithm based on nonsubsampled contourlet transform (NSCT) is proposed in this paper. The image is decomposed into coefficients of different scales and directions through nonsubsampled contourlet transform. It is denoised by the threshold method of the multi-scale product of NSCT coefficients. Then thresholds of the nonlinear enhancement function are determined according to the coefficients of each scale. The two parameters of the function, among which one is used to control the range of enhancement and the other can determine the strength of enhancement, are obtained by solving nonlinear equations. The coefficients processed by the enhancement function are used to reconstruct the image. The simulation results on the Matlab platform show that the algorithm has a good effect of enhancing details of images and suppressing noise signals meanwhile.

      PubDate: 2014-12-06T06:56:06Z
  • Synthetic aperture radar image de-noising based on Shearlet transform
           using the context-based model
    • Abstract: Publication date: December 2014
      Source:Physical Communication, Volume 13, Part C
      Author(s): Shuaiqi Liu , Mingzhu Shi , Shaohai Hu , Yang Xiao
      As the synthetic aperture radar (SAR) has been widely used in agriculture, forestry, hydrology, mining, marine, mapping and other fields, the method to improve the image quality and visual effect of the SAR image has become a hot research issue. The suppression and removal of the speckle of SAR image have become more and more important. This paper analyzes how the noises of the SAR image are generated and the models are appropriate for the characteristics of SAR images. Then based on the advantages of the Shearlet transform, we proposed an SAR image de-noising algorithm which combines the improved Shearlet transform with a cycle spinning de-noising algorithm by using an adaptive threshold method based on the context model. Simulation results show that the proposed algorithm can significantly suppress the speckle noise and improve the peak signal-to-noise ratio (PSNR) of the image; it also holds the characteristics of translational invariance (which can keep the edges of the image detail signal well and inhibit Gibbs phenomenon caused by noise reduction), and it can greatly improve the visual effect.

      PubDate: 2014-12-06T06:56:06Z
  • Nested sparse sampling and co-prime sampling in sense-through-foliage
           target detection
    • Abstract: Publication date: December 2014
      Source:Physical Communication, Volume 13, Part C
      Author(s): Na Wu , Qilian Liang
      This paper firstly introduces nested sampling and co-prime sampling, which were proposed recently, but have never been applied to real world target detection. We apply nested sampling and co-prime sampling to target detection in UWB radar sensor networks (RSN), based on a differential approach. The non-stationary UWB signal needs to be decomposed into several approximate wide sense stationary (WSS) signals so that nested sampling could be used in this situation. We also compare the performance of nested sampling and co-prime sampling against uniform under-sampling. The results show that in terms of good quality data and poor quality data, both nested sampling and co-prime sampling work better.

      PubDate: 2014-12-06T06:56:06Z
  • SC-FDMA user pairing and frequency allocation with imperfect channel state
    • Abstract: Publication date: Available online 23 October 2014
      Source:Physical Communication
      Author(s): M.A. Ruder , A. Moldovan , W.H. Gerstacker
      We consider user pairing for a single-carrier frequency-division multiple-access (SC-FDMA) transmission in the uplink of a Long Term Evolution (LTE) system. Two single-antenna users each are multiplexed to the same time and frequency resource within one cell. A virtual multiple-input multiple-output (V-MIMO) system arises for each user pair if multiple receive antennas are employed at the base station. For user pairing and frequency allocation, knowledge about the channel state is necessary. According to the LTE standard sounding reference signals are used for channel acquisition and transmitted with interleaved frequency-division multiple-access (I-FDMA). In channel state acquisition, the subcarriers not included in the channel sounding procedure should be taken into account by interpolation in frequency direction in a first step. Then a prediction in time direction for the time instant of the considered subframe is required. Channel interpolation and prediction are revisited in this paper, and the influence of channel interpolation and prediction errors on the achievable data rate of the system with user pairing and frequency resource allocation is studied. Simulation results show that joint user pairing and frequency allocation combined with channel interpolation and prediction is always beneficial for static or slowly moving users. However, for high user velocity the performance approaches that of random pairing and frequency allocation or becomes even worse.

      PubDate: 2014-11-19T05:29:21Z
  • Modified leakage-based transmit filter designs for multi-user MIMO systems
    • Abstract: Publication date: Available online 4 November 2014
      Source:Physical Communication
      Author(s): Piya Patcharamaneepakorn , Simon Armour , Angela Doufexi
      This paper proposes two modified definitions of signal-to-leakage-plus-noise ratio (mSLNR) as criteria for linear transmit filter design in Multi-User MIMO systems. The proposed criteria incorporate receiver structures and priority weight matrices into the precoder design, which can effectively exploit unused receive signal spaces, in the case that available eigenmodes are not fully transmitted, and can potentially prioritise users’ data streams. Iterative SLNR (iSLNR) precoding algorithms based on the proposed mSLNR definitions are also presented. Further, the variations of the iSLNR algorithms are thoroughly studied. In particular, the impact of the mSLNR defnitions, choices of receive filters and iteration types on the convergence property and sum-rate performance is discussed. Moreover, the effect of weight matrices on users’ prioritisation is elaborated. For extreme weight values, the proposed algorithms are shown to converge to either eigenbeamforming or null-space decomposition techniques. Further, a robust design of the proposed schemes for the case of imperfect channel state information (CSI) is presented. It is shown that adequate knowledge of effective receive subspaces can be attained by simply assuming matched filters (MF) in the iterative precoding process, while further improvement can be obtained by an actual implementation of interference-mitigation-capable receivers.

      PubDate: 2014-11-19T05:29:21Z
  • Resource allocation for LTE-based cognitive radio network with queue
           stability and interference constraints
    • Abstract: Publication date: Available online 18 November 2014
      Source:Physical Communication
      Author(s): Alia Asheralieva , Kaushik Mahata
      We consider the problem of interference management and resource allocation in a cognitive radio network (CRNs) where the licensed spectrum holders (primary users) share their spare capacity with the non-licensed spectrum holders (secondary users). Under such shared spectrum usage the transmissions of the secondary users should have a minimal impact on the quality of service (QoS) and the operating conditions of the primary users. Therefore, it is important to distinguish the two types of users, and formulate the problem of resource allocation considering hard restrictions on the user-perceived QoS (such as packet end-to-end delay and loss) and physical-layer channel characteristics (such as noise and interference) of the primary users. To achieve this goal, we propose to assign the bandwidth and transmission power to minimize the total buffer occupancy in the system subject to capacity constraints, queue stability constraints, and interference requirements of the primary users. We apply this approach for resource allocation in a CRN built upon a Third Generation Partnership Project (3GPP) long-term evolution (LTE) standard platform. Performance of the algorithm is evaluated using simulations in OPNET environment. The algorithm shows consistent performance improvement when compared with other relevant resource allocation techniques.

      PubDate: 2014-11-19T05:29:21Z
  • Editorial Board
    • Abstract: Publication date: December 2014
      Source:Physical Communication, Volume 13, Part B

      PubDate: 2014-11-19T05:29:21Z
  • Sum rates for multi-user MIMO vector perturbation precoding with
    • Abstract: Publication date: Available online 11 October 2014
      Source:Physical Communication
      Author(s): Adeel Razi , Daniel J. Ryan , Jinhong Yuan , Iain B. Collings
      In this paper, we analyze the sum rate performance of multiuser multi-antenna downlink channel. We consider Rayleigh fading environment when regularized vector perturbation precoding (R-VPP) method is used at the transmitter. We derive expressions for the sum rate in terms of the variance of the received signal. We also provide a closed form approximation for the mean squared error (MSE) which is shown to work well for the whole range of SNR. Further, we also propose a simpler expression for R-VPP sum rate based on MSE. The simulation results show that the proposed expressions for R-VPP sum rate closely match the sum rate found by the entropy estimation. Our results show that when compared with other linear and non-linear precoding methods (like zero-forcing precoder, linear minimum mean square error (MMSE) precoder and VPP), R-VPP sum rate performance is very close to DPC for all SNR values. It is also noted that the sum rate performance of the linear MMSE precoder is very close to the R-VPP at low to medium SNR range. Finally we also compared the merits of performing regularization for VPP as compared to the greedy rate maximizing user scheduling. It turns out that the R-VPP with or without user selection performs better than the VPP systems with user selection.

      PubDate: 2014-10-12T09:45:03Z
  • A dynamic subcarrier exchange scheme for SFR-aided LTE networks
    • Abstract: Publication date: Available online 11 October 2014
      Source:Physical Communication
      Author(s): Zhaokun Qin , Lin Zhang , Ming Jiang
      In the orthogonal frequency division multiplexing (OFDM) aided long term evolution (LTE) system, the intra-cell interference can be effectively suppressed by excellent orthogonality between the subcarriers within the same serving cell. However, the inter-cell interferences (ICI) still exist, since the neighbor cells employ the same frequency bands as the serving cell does, deteriorating the system performance especially at the cell edge. Soft frequency reuse (SFR) schemes have therefore been proposed to mitigate the ICI issue for capacity improvements at cell edge. Nonetheless, the allocation of subcarriers in SFR reduces spectral efficiency in specific cell areas, for both cell center and cell edge scenarios, resulting in the decrease of the system throughput. In this paper, we propose to improve the system throughput by dynamically allocating and exchanging the subcarriers among different cells. In the proposed dynamic subcarrier exchange (DSE) scheme, the same major subcarriers are not allowed to be used by the adjacent cell edge for ICI suppression purpose. In each scheduling period, each cell dynamically determines its own major subcarriers based on the available spectrum usage information. Thus, the spectrum bands are allocated distributedly and the multiple cells share the spectrum bands in a cooperative way. Simulation results demonstrate that the proposed DSE scheme significantly improves the spectrum utilization and achieves higher system throughput than its SFR counterpart.

      PubDate: 2014-10-12T09:45:03Z
  • Terrain based system design and SNR variability prediction in multi-hop
           transparent relay transmission systems
    • Abstract: Publication date: Available online 6 October 2014
      Source:Physical Communication
      Author(s): Cibile K. Kanjirathumkal , S.M. Sameer , Lillykutty Jacob
      The challenging issue of assessing the impact of fading distribution and hop count on the system performance of multi hop transparent cooperative network for indoor as well as outdoor communications is addressed in this article. As the received signal fluctuations depend on the compound channel variations, a cost effective link design and power budget of fixed relaying systems based on the evaluated terrain dependent statistical properties are presented. Subsequently, hop count selection and theoretical prediction of variability of signal-to-noise-ratio (SNR) are performed in a particular application scenario. The proposed approach eliminates the need for continuous monitoring of the time varying SNR on each branch of the receiver diversity system. The impact of hop count on the bit error rate performance of the designed system, under two different per-hop distributions–Nakagami- m and Weibull, which can adequately characterise the terrain fading effects on empirical data–are also studied using simulations. The effectiveness of the derived metrics in selecting appropriate branches of sufficient channel quality in selection combining diversity systems are also investigated.

      PubDate: 2014-10-09T08:47:58Z
  • Green and fast DSL via joint processing of multiple lines and
           time-frequency packed modulation
    • Abstract: Publication date: Available online 5 October 2014
      Source:Physical Communication
      Author(s): Stefano Buzzi , Chiara Risi , Giulio Colavolpe
      In this paper, strategies to enhance the performance, in terms of available data-rate per user, energy efficiency, and spectral efficiency, of current digital subscriber lines (DSL) lines are proposed. In particular, a system wherein a group of copper wires is jointly processed at both ends of the communication link is considered. For such a scenario, a resource allocation scheme aimed at energy efficiency maximization is proposed, and, moreover, time-frequency packed modulation schemes are investigated for increased spectral efficiency. Results show that a joint processing of even a limited number of wires at both ends of the communication links brings remarkable performance improvements with respect to the case of individual point-to-point DSL connections; moreover, the considered solution does represent a viable means to increase, in the short term, the data-rate of the wired access network, without an intensive (and expensive) deployment of optical links.

      PubDate: 2014-10-09T08:47:58Z
  • Editorial Board
    • Abstract: Publication date: December 2014
      Source:Physical Communication, Volume 13, Part A

      PubDate: 2014-10-04T07:48:49Z
  • Sensor-based dead-reckoning for indoor positioning
    • Abstract: Publication date: December 2014
      Source:Physical Communication, Volume 13, Part A
      Author(s): Ian Sharp , Kegen Yu
      This paper presents a method of indoor position determination using an accelerometer, compass and gyroscope which are typically available in devices such as smart phones. The method makes use of measurements from such a device worn on the body, such as attached to a belt. The accelerometer in the device estimates the stride length indirectly from the vertical acceleration associated with walking, while the compass and gyroscope measure the heading angle. The position of the subject is then determined by combining the stride length distance estimates and the heading information, but corrected periodically at known checkpoints within the building. The method was tested with a range of both males and females wearing the device, at different walking speeds and styles. The experimental results demonstrate that the stride length estimation can be accurate to about 7 percent. The measured data agree closely with a theoretical dynamical model of walking. The results also show that the position of the subject can be determined with an accuracy of 0.6 m when walking along an indoor path.

      PubDate: 2014-10-04T07:48:49Z
  • Optimal multisensor integrated navigation through information space
    • Abstract: Publication date: December 2014
      Source:Physical Communication, Volume 13, Part A
      Author(s): Yong Li
      Although the centralized Kalman filtering (CKF) solution is widely accepted as providing the globally optimal parameter estimation for multisensor navigation systems, it has inherent defects such as heavy communication and computational load and poor fault tolerance. To address these problems decentralized Kalman filtering (DKF) methods have been proposed. The DKF is configured as a bank of filters instead of the central filter, and aims to achieve the same level of accuracy as the CKF. This CKF-based approach however is found to be too rigorous to limit the further development of DKF algorithms. This paper proposes an alternative framework for resolving the optimal state estimation problem of multisensor integration. The data fusion algorithm is implemented through a series of transformations of vectors from one space into another. In this way, the vectors in the source information spaces are transformed into the estimate information space, where the globally optimal solution is obtained simply by a sum of these transformed vectors. The paper demonstrates how easy it is to derive the conventional DKF algorithms, such as the federated Kalman filter that has been widely applied in the multisensor navigation community. A new global optimal fusion algorithm is derived from the proposed approach. Simulation results demonstrate that the algorithm has higher accuracy than the CKF.

      PubDate: 2014-10-04T07:48:49Z
  • Seamless outdoor/indoor navigation with WIFI/GPS aided low cost Inertial
           Navigation System
    • Abstract: Publication date: December 2014
      Source:Physical Communication, Volume 13, Part A
      Author(s): Jiantong Cheng , Ling Yang , Yong Li , Weihua Zhang
      This paper describes an integrated navigation system that can be used for pedestrian navigation in both outdoor and indoor environments. With the aid of Global Positioning System (GPS) positioning solutions, an Inertial Navigation System (INS) can provide stable and continuous outdoor navigation. When moving indoors, WIFI positioning can replace the GPS in order to maintain the integrated system’s long-term reliability and stability. On the other hand, the position from an INS can also provide a priori information to aid WIFI positioning. Signal strength-based WIFI positioning is widely used for indoor navigation. A new fingerprinting method is proposed so as to improve the performance of WIFI stand-alone positioning. For pedestrian navigation applications, a step detection method is implemented to constrain the growth of the INS error using an Extended Kalman Filter (EKF). Experiments have been conducted to test this system and the results have demonstrated the feasibility of this seamless outdoor/indoor navigation system.

      PubDate: 2014-10-04T07:48:49Z
  • Single frequency network based mobile tracking in NLOS environments
    • Abstract: Publication date: December 2014
      Source:Physical Communication, Volume 13, Part A
      Author(s): Jun Yan , Kegen Yu , Lenan Wu
      In single frequency network (SFN) positioning, base station (BS) identification is inevitable and non-line-of-sight (NLOS) propagation is usually dominant especially for indoor scenarios. BS identification and NLOS mitigation are two challenging problems which have significant impact on the SFN positioning performance. In this paper, a mobile tracking scheme is proposed to deal with these challenging issues. Specifically, BS identification is first formulated as a data validation problem. Each time-of-arrival (TOA) measurement is tentatively associated with a specific BS so that a number of TOA–BS relationship sets are produced. The gate technique is adapted to evaluate all the TOA–BS relationship sets and the set with the smallest gate parameter value is selected. This identification technique is suited for both line-of-sight (LOS) and NLOS propagation scenarios. The interacting multiple model (IMM) smoother is then utilized to smooth the identified TOA measurements at each BS to reduce the NLOS errors. In addition, the position determination and BS identification are jointly considered to enhance position estimation accuracy. Simulation results demonstrate that the proposed SFN positioning approach can perform satisfactorily in different propagation scenarios and has better performance than other SFN positioning algorithms.

      PubDate: 2014-10-04T07:48:49Z
  • Capacity analysis of spectrum sharing spatial multiplexing MIMO systems
    • Abstract: Publication date: Available online 28 September 2014
      Source:Physical Communication
      Author(s): Liang Yang , Khalid Qaraqe , Erchin Serpedin , Mohamed-Slim Alouini
      This paper considers a spectrum sharing (SS) multiple-input multiple-output (MIMO) system operating in a Rayleigh fading environment. First the capacity of a single-user SS spatial multiplexing system is investigated in two scenarios that assume different receivers. To explicitly show the capacity scaling law of SS MIMO systems, some approximate capacity expressions for the two scenarios are derived. Next, we extend our analysis to a multiple user system with zero-forcing receivers (ZF) under spatially-independent scheduling and analyze the sum-rate. Furthermore, we provide an asymptotic sum-rate analysis to investigate the effects of different parameters on the multiuser diversity gain. Our results show that the secondary system with a smaller number of transmit antennas N t and a larger number of receive antennas N r can achieve higher capacity at lower interference temperature Q , but at high Q the capacity follows the scaling law of the conventional MIMO systems. However, for a ZF SS spatial multiplexing system, the secondary system with small N t and large N r can achieve the highest capacity throughout the entire region of Q . For a ZF SS spatial multiplexing system with scheduling, the asymptotic sum-rate scales like N t log 2 ( Q ( K N t N p − 1 ) / N t ) , where N p denotes the number of antennas of primary receiver and K represents the number of secondary transmitters.

      PubDate: 2014-09-29T06:39:47Z
  • Out-of-band power reduction by using computationally efficient
           cancellation pulses
    • Abstract: Publication date: Available online 6 September 2014
      Source:Physical Communication
      Author(s): Mohammad Aliasgari , Aliazam Abbasfar , Sied Mehdi Fakhraie
      Cancellation carrier technique is a well-known out-of-band (OOB) power suppressing method in orthogonal frequency-division multiplexing (OFDM) overlay systems. In this technique, OOB power emission reduction is achieved by employing additional carriers, known as cancellation carriers (CCs), and optimizing their amplitude and phase in order to satisfy the desired spectral mask. The more CCs we employ, the deeper spectrum mask we achieve; however, it is shown in this paper that the computational complexity of this optimization algorithm dramatically grows by increasing the number of total employed CCs. In order to reduce the complexity of this method, a class of unique offline-optimized cancellation pulses is introduced which can perform as well as conventional sinc-shaped CC, but with considerably less computational complexity. In fact for a particular set of reserved cancellation tones, we need fewer proposed cancellation pulses to suppress a certain amount of OOB radiations. Therefore, the number of parameters in the optimization algorithm is reduced and consequently the computational complexity is decreased. This complexity reduction has been achieved at no extra side cost in system performances.

      PubDate: 2014-09-08T02:55:29Z
  • Comparison of sparse recovery algorithms for channel estimation in
           underwater acoustic OFDM with data-driven sparsity learning
    • Abstract: Publication date: Available online 13 August 2014
      Source:Physical Communication
      Author(s): Yi Huang , Lei Wan , Shengli Zhou , Zhaohui Wang , Jianzhong Huang
      Through exploiting the sparse nature of underwater acoustic (UWA) channels, compressed sensing (CS) based sparse channel estimation has demonstrated superior performance compared to the conventional least-squares (LS) method. However, a priori information of channel sparsity is often required to set a regularization constraint. In this work, we propose a data-driven sparsity learning approach based on a linear minimum mean square error (LMMSE) equalizer to tune the regularization parameter for the orthogonal frequency division multiplexing (OFDM) transmissions. A golden section search is used to accelerate the sparsity learning process. In the context of the intercarrier interference (ICI)-ignorant and ICI-aware UWA OFDM systems, the block error rates (BLERs) using different sparse recovery algorithms for channel estimation under the L 0 , L 1 / 2 , L 1 , and L 2 constraints are compared. Simulation and experimental results show that the data-driven sparsity learning approach is effective, overcoming the drawback of using a fixed regularization parameter in different channel conditions. When the sparsity parameter for each approach is optimized based on the data-driven approach, the L 1 / 2 recovery algorithm and the considered four L 1 recovery algorithms: SpaRSA, FISTA, Nesterov, and TwIST, have nearly the same BLER performance, outperforming L 0 and L 2 algorithms.

      PubDate: 2014-08-17T01:20:17Z
  • Robust joint fine timing synchronization and channel estimation for MIMO
    • Abstract: Publication date: Available online 25 July 2014
      Source:Physical Communication
      Author(s): Te-Lung Kung
      This paper proposes a joint timing synchronization and channel estimation scheme for multiple-input single-output or multiple-input multiple-output communication systems. All timing offsets and channel impulse responses (CIR) of different transmit-receive links are obtained based on a well-designed training sequence arrangement. The proposed approach consists of three stages at each receive antenna. First, a coarse timing offset (CTO) estimation algorithm is performed to estimate the CTO and the inter-transmitter delays. Then, relative timing indices and the corresponding CIR estimates of all transmit-receive links at the second stage are obtained using the generalized maximum-likelihood estimation based on a sliding observation vector. Finally, the fine time adjustment based on the minimum mean-squared error criterion is performed. From the simulation results, the proposed approach has excellent timing synchronization performance under several channel models at very low signal-to-noise ratio which is smaller than 1 dB. Also, the channel estimation performance in the proposed scheme approaches to the Cramér-Rao bound.

      PubDate: 2014-07-29T23:13:30Z
  • Editorial Board
    • Abstract: Publication date: September 2014
      Source:Physical Communication, Volume 12

      PubDate: 2014-07-24T23:08:08Z
  • Fast efficient spectrum allocation and heterogeneous network selection
           based on modified dynamic evolutionary game
    • Abstract: Publication date: Available online 28 April 2014
      Source:Physical Communication
      Author(s): Jianrui Chen , L.C. Jiao , Jianshe Wu , Xiaohua Wang
      Dynamic evolutionary game has attracted a lot of attention in cognitive network because it can adaptively learn during the strategy under changing conditions adopting replicator dynamics equation. But the information required by the original replicator dynamics equation is large. In this paper, we provide a modified replicator dynamics equation, which can adaptively converge to the desired stable state with faster speed. Noted that, the necessary information transmission in the evolutionary process is much less than that of the original replicator dynamics equation. Moreover, we apply the modified dynamics equation to (i) opportunistic spectrum access with multiple primary users selling free spectrum opportunities to multiple secondary users; (ii) heterogeneous network selection. Simulation results show that the evolving time is cut down greatly and equal maximal payoff is obtained. Besides, the proposed method is robust even if there is large time delay in the process of information transmission.

      PubDate: 2014-07-24T23:08:08Z
  • A novel recognition system for human activity based on wavelet packet and
           support vector machine optimized by improved adaptive genetic algorithm
    • Abstract: Publication date: Available online 2 May 2014
      Source:Physical Communication
      Author(s): Jin Jiang , Ting Jiang , Shijun Zhai
      A new human activities recognition system based on support vector machine (SVM) optimized by improved adaptive genetic algorithm (IAGA) and wavelet packet is proposed. Wavelet packet transform (WPT) is applied to extract the signatures from various actions. SVM is a powerful tool for solving the classification problem with small sampling, nonlinearity and high dimension. Genetic algorithm (GA) is employed to determine the two optimal parameters for SVM with highest predictive accuracy and generalization ability. Moreover, the IAGA adopts the dynamic cross rate and mutation rate according to the group fitness, thus effectively avoiding the disadvantages of the standard GA, such as premature convergence and low robustness. The average recognition accuracy rate goes up to 97.6%. In addition, the result of suggested method is also compared with other feature extraction methods which further demonstrate the superiority of WPT and generalization ability of IAGA. The aforementioned results clearly demonstrate that the proposed method is superior to the traditional method in activity recognition.

      PubDate: 2014-07-24T23:08:08Z
  • Spectral and energy efficiency analysis of uplink heterogeneous networks
           with small-cells on edge
    • Abstract: Publication date: Available online 2 May 2014
      Source:Physical Communication
      Author(s): Muhammad Zeeshan Shakir , Hina Tabassum , Khalid A. Qaraqe , Erchin Serpedin , Mohamed-Slim Alouini
      This paper presents a tractable mathematical framework to analyze the spectral and energy efficiency of an operator initiated deployment of the small-cells (e.g., femtocells) where the small-cell base stations are deliberately positioned around the edge of the macrocell. The considered deployment facilitates the cell-edge mobile users in terms of their coverage, spectral, and energy efficiency and is referred to as cell-on-edge (COE) configuration. The reduction in energy consumption is achieved by considering fast power control where the mobile users transmit with adaptive power to compensate the path loss, shadowing and fading. In particular, we develop a moment generating function (MGF) based approach to derive analytical bounds on the area spectral efficiency and exact expressions for the energy efficiency of the mobile users in the considered COE configuration over generalized- K fading channels. Besides the COE configuration, the derived bounds are also shown to be useful in evaluating the performance of random small-cell deployments, e.g., uniformly distributed small-cells. Simulation results are presented to demonstrate the improvements in spectral and energy efficiency of the COE configuration with respect to macro-only networks and other unplanned deployment strategies.

      PubDate: 2014-07-24T23:08:08Z
  • One-bit time reversal using binary pulse sequence for indoor
    • Abstract: Publication date: Available online 16 June 2014
      Source:Physical Communication
      Author(s): A. Khaleghi , I. Balasingham , R. Chávez-Santiago
      Time reversal (TiR) is a pre-filtering technique that exploits the propagation channel state information in order to reduce the complexity of a user’s terminal in a communication system. TiR transfers the system complexity to the base station and has been proposed for ultra wideband (UWB) communications in highly dispersive multipath environments. In TiR-UWB two complex tasks must be carried out by the base station. The first is the estimation of the channel state information of the user’s terminal, and the second is the generation of the time reversed channel signal. In this paper, the use of a correlation receiver for the estimation of the multipath components (MPCs) of the propagation channel is proposed. Then, a novel binary time reversal (BTiR) method that makes use of the resolvable MPCs to simplify the transceiver tasks is introduced. When using BTiR the communication system can be regarded as a direct sequence spread spectrum (DSSS) scheme in which the spreading chips are provided by the propagation channel. The performance of the proposed BTiR scheme is assessed by using measurements of UWB spatial channels in a typical indoor environment.

      PubDate: 2014-07-24T23:08:08Z
  • Target identification in foliage environment using UWB radar with hybrid
           wavelet–ICA and SVM method
    • Abstract: Publication date: Available online 2 June 2014
      Source:Physical Communication
      Author(s): Xiangbo He , Ting Jiang
      This paper proposes a method of target identification in foliage environment, specifically to identify the number of people present in foliage environment. This method is based on the ultra-wideband (UWB) radar sensor networks (RSNs) model. UWB technology can be used for target identification and intrusion detection, we can integrate UWB-IR technology and passive radar theory directly into target detection and identification in the foliage environment through analyzing and processing of the received UWB signal. Firstly, extensive Wideband Impulse Radio (UWB-IR) was sent and received within RSNs in foliage environment. Subsequently, we used hybrid Wavelet Analysis (WA) and Independent Component Analysis (ICA) method to extract features that can reflect the scenario characteristic. Finally, those extracted features are used to train Support Vector Machine (SVM) and to classify the number of people in foliage environment. The result with an average identification rate of no less than 95% shows the effectiveness of the proposed method.

      PubDate: 2014-07-24T23:08:08Z
  • Special issue on Heterogeneous and small cell networks
    • Abstract: Publication date: Available online 24 June 2014
      Source:Physical Communication
      Author(s): Jemin Lee , Marios Kountouris , Tony Q.S. Quek , Vincent Lau

      PubDate: 2014-07-24T23:08:08Z
  • Terahertz band: Next frontier for wireless communications
    • Abstract: Publication date: September 2014
      Source:Physical Communication, Volume 12
      Author(s): Ian F. Akyildiz , Josep Miquel Jornet , Chong Han
      This paper provides an in-depth view of Terahertz Band (0.1–10 THz) communication, which is envisioned as a key technology to satisfy the increasing demand for higher speed wireless communication. THz Band communication will alleviate the spectrum scarcity and capacity limitations of current wireless systems, and enable new applications both in classical networking domains as well as in novel nanoscale communication paradigms. In this paper, the device design and development challenges for THz Band are surveyed first. The limitations and possible solutions for high-speed transceiver architectures are highlighted. The challenges for the development of new ultra-broadband antennas and very large antenna arrays are explained. When the devices are finally developed, then they need to communicate in the THz band. There exist many novel communication challenges such as propagation modeling, capacity analysis, modulation schemes, and other physical and link layer solutions, in the THz band which can be seen as a new frontier in the communication research. These challenges are treated in depth in this paper explaining the existing plethora of work and what still needs to be tackled.

      PubDate: 2014-04-27T19:25:27Z
  • Indoor navigation and tracking
    • Abstract: Publication date: Available online 24 February 2014
      Source:Physical Communication
      Author(s): Kegen Yu , Ian Oppermann , Eryk Dutkiewicz , Ian Sharp , Guenther Retscher

      PubDate: 2014-04-27T19:25:27Z
  • Design protocol and performance analysis of indoor fingerprinting
           positioning systems
    • Abstract: Publication date: Available online 26 February 2014
      Source:Physical Communication
      Author(s): Vahideh Moghtadaiee , Andrew G. Dempster
      Location fingerprinting is a technique widely suggested for indoor positioning. Given specific positioning requirements, this paper provides methods for setting up the network elements such that those requirements can be met by the location fingerprinting method. In particular, the paper aims to optimize indoor fingerprinting systems such that the positioning performance gets close to the optimal performance indicated by the lower bound of the system. The Weiss–Weinstein bound (WWB) and Extended Ziv–Zakai bound (EZZB) are suggested for indoor environments, as they are shown to have superior predictive performance for this application. The effects of the number and geometry of access points (APs), the number and spatial arrangement of reference points (RPs), and the number of signal strength samples taken per location are presented, both through simulations and analytical lower bound estimates. The impact of the path-loss exponent, the standard deviation of the signal strength measurement, and size of the operating area are also investigated. These theoretical/simulation estimates are also assessed using experimental data. By utilizing these tools, a system designer is able to set appropriate parameters to optimize the compromise between positional accuracy and the costs associated with the setting up of the fingerprinting measurements database.

      PubDate: 2014-04-27T19:25:27Z
  • Energy and delay constrained scheduling of real time traffic over OFDM
           communication system with non-causal channel information
    • Abstract: Publication date: Available online 18 April 2014
      Source:Physical Communication
      Author(s): Ritesh Kumar Kalle , Debabrata Das
      A point to point wireless communication system based on Orthogonal Frequency Division Multiplexing (OFDM) is considered, wherein R bits of information have to be scheduled within a hard delay deadline of T time slots over a frequency selective slow fading channel. The scheduling objective is to minimize the energy expenditure with non-causal knowledge of channel state over a limited time horizon, number of bits to be served and delay constraints. We assume a convex monomial energy-bit cost function and propose novel efficient two stage heuristic algorithm that allocate the R bits on the time slots, followed by greedy optimal bit loading over the OFDM subcarriers. Analytical model is developed and numerical simulations are performed to validate the proposed approach as well as the results show that our algorithms outperform existing approaches in published literature by up to 10dB in power margin on an average in high load conditions while meeting the deadline of T timeslots.

      PubDate: 2014-04-27T19:25:27Z
  • A framework for leakage-based autonomous uplink inter-cell interference
           coordination in OFDMA/LTE heterogeneous networks
    • Abstract: Publication date: Available online 26 April 2014
      Source:Physical Communication
      Author(s): Mai B.S.A. Kafafy , Khaled M.F. Elsayed
      The inter-cell interference (ICI) problem in OFDMA wireless systems is a major impediment to attain high rates particularly for cell-edge users in reuse-1 systems. Using centralized resource allocation to combat ICI is not practical, particularly in heterogeneous networks (HetNets), as they require intensive signalling about interference and channel state information that may not always be practically available. The main contribution of this paper is devising efficient autonomous power allocation schemes such that the interference produced by each cell is below a certain limit. We develop two inter-cell interference coordination (ICIC) frameworks; the overall interference limit (OIL), and the interference limit per resource block (ILR). The first framework imposes an overall interference limit on each cell, while the second imposes different interference limits on different resource blocks in each cell. We propose a closed form solution, and an iterative solution for the OIL framework, and a closed form solution for the ILR framework which has an additional advantage of possible autonomous application at each terminal rather than at the base station. We present two semi-autonomous heuristic and optimal adaptive schemes that use the overload indicator (OI) signal in LTE to adjust the values of the interference limits in the ILR scheme. They attempt to alleviate the interference seen by overloaded cells in order to achieve fairness among different cells, which is very important especially in HetNets. A method based on the Kalman filter is introduced to predict the values of the OI in the intervals between the OI exchanges. This estimation can be applied to the adaptive schemes almost autonomously as it requires very infrequent signalling between cells. Simulations show that the proposed schemes exhibit better performance than equal power allocation. Comparison with centralized optimal allocation that uses global information shows good performance with acceptable degradation in the spectral efficiency which decreases as the interference limit increases. Simulations also show that the ILR and the OIL schemes almost have the same performance, and the adaptive schemes achieve fairness among different cells especially in a HetNet environment.

      PubDate: 2014-04-27T19:25:27Z
  • A model based on poison point process for downlink K tiers fractional
           frequency reuse heterogeneous networks
    • Abstract: Publication date: Available online 26 April 2014
      Source:Physical Communication
      Author(s): He Zhuang , Tomoaki Ohtsuki
      Modern cellular networks are currently transitioning from homogeneous networks to heterogeneous networks (HetNets). Unlike homogeneous networks, HetNets comprise of K tiers of random base stations (BSs), where each tier may differ in terms of transmit power, BSs’ deployment density and target signal to interference plus noise ratio (SINR). Although HetNets significantly increase spatial frequency efficiency and transmit capacity, they also introduce two main problems: introducing cross-tier interference, and increasing the difficulty of modeling and analysis, due to the increase of randomness of BSs’ locations, particularly, user-deployed femto BSs. For the first problem, fractional frequency reuse (FFR), as an interference management technique, can mitigate effectively the impact of interference. Recently, Poisson point process (PPP) is more and more used to model HetNets, because it can naturally capture the randomness of the BSs’ locations. In this work, we develop a general downlink model based on PPP for HetNets utilizing FFR. We derive tractable expressions of coverage probability under both open and closed access schemes, which even can be simplified to a simple closed form for interference-limited HetNets (neglect noise). We also show the impact of the main parameters on the coverage probability.

      PubDate: 2014-04-27T19:25:27Z
  • A Survey of QoS/QoE mechanisms in heterogeneous wireless networks
    • Abstract: Publication date: Available online 26 April 2014
      Source:Physical Communication
      Author(s): Jason B. Ernst , Stefan C. Kremer , Joel J.P.C. Rodrigues
      Heterogeneous Wireless Networks (HWNs) are an important step in making connectivity ubiquitous and pervasive. Leveraging the increasing variety of connectivity options available to devices solves many problems such as capacity, spectrum efficiency, coverage and reliability. Anytime decisions are made for selection, handover, scheduling or routing many performance metrics along with energy efficiency and cost for access must be considered. The increased number of choices in a HWN makes the problem more difficult than traditional homogeneous networks since each Radio Access Technology (RAT) has unique characteristics. For instance, Bluetooth networks have low range and speed but are cheap compared to 4G networks. These types of observations can be factored into decision making in HWNs. Quality of Service and Experience should be considered so that the best possible configuration of connectivity, price and user application is made. All of this should occur autonomously. This paper provides a survey of recent works in HWNs with these ideas in mind. Existing approaches are categorized by function. Limitations and strengths of solutions are highlighted and comparisons between approaches are made to provide a starting point for further research in the area.

      PubDate: 2014-04-27T19:25:27Z
  • Cell selection for open-acces femtocell networks: Learning in changing
    • Abstract: Publication date: Available online 26 April 2014
      Source:Physical Communication
      Author(s): Chaima Dhahri , Tomoaki Ohtsuki
      This paper addresses the problem of cell selection in dynamic open-access femtocell networks. We model this problem as decentralized restless multi-armed bandit (MAB) with unknown dynamics and multiple players. Each channel is modelled as an arbitrary finite-state Markov chain with different state space and statistics. Each user tries to learn the best channel that maximizes its capacity and reduces its number of handovers. This is a classic exploration/exploitation problem, where the reward of each channel is considered to be Markovian. In addition, the reward process is restless because the state of each Markov chain evolves independently of the user action. This leads to a decentralized restless bandit problem. To solve this problem, we refer to the decentralized restless upper confidence bound (RUCB) algorithm that achieves a logarithmic regret over time for MAB problem (proposal 1). Then, we extend this algorithm to cope with dynamic environment by applying a change point detection test based on Page–Hinkley test (PHT) (proposal 2). However, this test would entail some waste of time if the change-point detection was actually a false alarm. To face this problem, we extend our previous proposal by referring to a meta-bandit algorithm (proposal 3) to solve the dilemma between Exploration and Exploitation after the change-point detection occurs. Simulation results show that • our proposal come close to the performance of opportunistic method in terms of capacity, while fewer average number of handovers is required. • The use of a change point test and meta-bandit algorithm allow better performance than RUCB in terms of capacity particularly in a changing environment.

      PubDate: 2014-04-27T19:25:27Z
  • Fuzzy Logic Classifier design for air targets recognition based on HRRP
    • Abstract: Publication date: Available online 26 April 2014
      Source:Physical Communication
      Author(s): Jing Liang , Fangqi Zhu
      The paper describes a Fuzzy Logic Classifier (FLC) to achieve the recognition for air targets. We first acquire the high range resolution profiles (HRRP) of three types of air targets from the measurements. We extract two typical features, namely, the length of the air targets and the difference between adjacent two HRRP based on HRRP from the measurements. Then we design the FLC to synthesize the two characters and identify the type of air targets. Simulation results show that our FLC can achieve the function of target recognition with a high ratio of recognition and also shows a robust performance to some extent.

      PubDate: 2014-04-27T19:25:27Z
  • MAC level Throughput comparison: 802.11ac vs. 802.11n
    • Abstract: Publication date: September 2014
      Source:Physical Communication, Volume 12
      Author(s): Oran Sharon , Yaron Alpert
      We compare between the Throughput performance of IEEE 802.11n and IEEE 802.11ac under the same PHY conditions and in the three aggregation schemes that are possible in the MAC layer of the two protocols. We find that for an error-free channel 802.11ac outperforms 802.11n due to its larger frame sizes, except for the case where there is a limit on the number of aggregated packets. In an error-prone channel the bit error rate sometimes determines the optimal frame sizes. Together with the limit on the number of aggregated packets, these two factors limit the advantage of 802.11ac.

      PubDate: 2014-04-27T19:25:27Z
  • Redundant residue number system based space–time block codes
    • Abstract: Publication date: Available online 22 January 2014
      Source:Physical Communication
      Author(s): Avik Sengupta , Balasubramaniam Natarajan
      In this paper, we propose a novel application of Redundant Residue Number System (RRNS) codes to Space–Time Block Codes (STBCs) design. Based on the so-called “Direct Mapping” and “Indirect Mapping” schemes, the link between residues and complex signal constellations is optimized. We derive upper bounds on the codeword error probability of RRNS–STBC and characterize its achievable diversity gain assuming maximum likelihood decoding (MLD). The knowledge of apriori probabilities of residues is utilized to implement a probability based Distance-Aware Direct Mapping scheme. Using simulation results, we demonstrate that the Distance-Aware Direct Mapping scheme provides performance gain, relative to a traditional direct mapping scheme, that increases with decreasing code rate.

      PubDate: 2014-01-25T03:07:54Z
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