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  Subjects -> PHYSICS (Total: 744 journals)
    - ELECTRICITY AND MAGNETISM (7 journals)
    - MECHANICS (20 journals)
    - NUCLEAR PHYSICS (44 journals)
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PHYSICS (541 journals)            First | 1 2 3 4 5 6 | Last

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: 17)
Physical Review Special Topics - Physics Education Research     Open Access   (Followers: 6)
Physical Review X     Open Access   (Followers: 4)
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  
Physics and Chemistry of the Earth, Parts A/B/C     Hybrid Journal   (Followers: 3)
Physics Essays     Full-text available via subscription  
Physics in Medicine & Biology     Full-text available via subscription   (Followers: 7)
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: 2)
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: 1)
Physics Research International     Open Access   (Followers: 1)
Physics Today     Hybrid Journal   (Followers: 19)
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 and Controlled Fusion     Hybrid Journal   (Followers: 2)
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: 436)
Proceedings of the National Academy of Sciences, India Section A     Hybrid Journal   (Followers: 3)
Progress in Materials Science     Hybrid Journal   (Followers: 18)
Progress in Planning     Hybrid Journal   (Followers: 1)
Progress of Theoretical and Experimental Physics     Open Access  
Quantum Electronics     Full-text available via subscription   (Followers: 2)
Quantum Measurements and Quantum Metrology     Open Access  
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: 2)
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: 9)
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: 16)
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  
Science China Physics, Mechanics and Astronomy     Hybrid Journal   (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: 11)
Selected Topics in Applied Earth Observations and Remote Sensing, IEEE Journal of     Hybrid Journal   (Followers: 16)
Sensor Letters     Full-text available via subscription   (Followers: 1)
Sensors and Actuators A: Physical     Hybrid Journal   (Followers: 28)
Services Computing, IEEE Transactions on     Hybrid Journal   (Followers: 3)
Shock and Vibration     Hybrid Journal   (Followers: 7)
Shock Waves     Hybrid Journal   (Followers: 4)
Small     Hybrid Journal   (Followers: 8)
Software Engineering, IEEE Transactions on     Hybrid Journal   (Followers: 20)
Solid State Physics     Full-text available via subscription  
Solid-State Circuits Magazine, IEEE     Hybrid Journal   (Followers: 1)
South African Journal for Research in Sport, Physical Education and Recreation     Full-text available via subscription   (Followers: 3)
Space Research Journal     Open Access   (Followers: 2)
Space Weather     Full-text available via subscription   (Followers: 3)
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy     Hybrid Journal   (Followers: 7)
Spectrochimica Acta Part B: Atomic Spectroscopy     Hybrid Journal   (Followers: 4)
Spectroscopy     Hybrid Journal   (Followers: 3)
Spectroscopy Letters: An International Journal for Rapid Communication     Hybrid Journal   (Followers: 3)
Sri Lankan Journal of Physics     Open Access  
Strain     Hybrid Journal   (Followers: 2)

  First | 1 2 3 4 5 6 | Last

Journal Cover Physical Communication
   Journal TOC RSS feeds Export to Zotero Follow    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 1874-4907
     Published by Elsevier Homepage  [2570 journals]   [SJR: 1.326]   [H-I: 13]
  • Sum rates for multi-user MIMO vector perturbation precoding with
           regularization
    • 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
           approach
    • 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
           systems
    • 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
       
  • Multiple description transform coded transmission over OFDM broadcast
           channels
    • Abstract: Publication date: September 2014
      Source:Physical Communication, Volume 12
      Author(s): Ashwani Sharma , Swades De , Hari M. Gupta , Ranjan Gangopadhyay
      We consider image transmission using multiple description transform coding (MDTC) over orthogonal frequency division multiplexed (OFDM) wireless broadcast channels, where the system may not have any feedback on channel gains. We investigate the redundancy allocation in MDTC–OFDM system, physical layer frequency diversity, and decoding strategies to maximize the quality of reconstruction. Via mathematical analysis, supported by MATLAB simulations, we show that, error resilience of the descriptions can be increased by suitable assignment of coding redundancy in the transform modules at the source, which can be further optimized if the channel characteristics are known at the transmitter. Additionally, the relative performance of the MDTC–OFDM system is studied with respect to a competitive approach, called forward error correction based multiple description coding (MDC) over OFDM, where we show that, for the same redundancy assignment, the MDTC based system performs better under harsh channel conditions.


      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
       
  • Physical Resource Block clustering method for an OFDMA cognitive femtocell
           system
    • Abstract: Publication date: June 2014
      Source:Physical Communication, Volume 11
      Author(s): Giulio Bartoli , Romano Fantacci , Dania Marabissi , Marco Pucci
      This paper deals with a heterogeneous Orthogonal Frequency Division Multiple Access (OFDMA) network where a user-deployed low power femtocell operates in the coverage area of a traditional macro-cell using the same frequency band. Femtocells represent a promising solution to increase the network capacity in next-generation wireless networks. However, the arising interference must be mitigated by means of suitable resource allocation policies. In particular, an OFDMA system allows a flexible usage of the resources that are organized in Physical Resource Blocks (PRBs). This flexibility can be fully exploited in a heterogeneous network if the femtocell base station knows how the PRBs are organized and grouped. This paper considers a cognitive femtocell base station that is able to sense the environment and identify the set of PRBs allocated to a given user by the macro-cell base station. A PRBs clustering method is proposed here. Initially, suitable inputs are derived and then provided to the K -means algorithm for a clustering refinement. The method proposed here is able to correctly gather together the PRBs of each user. Performance comparisons with a hierarchical clustering method is presented. The benefits of PRBs clustering on direction of arrival estimation are shown in order to prove the effectiveness of the proposed methods.


      PubDate: 2014-07-24T23:08:08Z
       
  • Uplink CFO compensation for FBMC multiple access and OFDMA in a high
           mobility scenario
    • Abstract: Publication date: June 2014
      Source:Physical Communication, Volume 11
      Author(s): Gustavo J. González , Fernando H. Gregorio , Juan Cousseau , Risto Wichman , Stefan Werner
      We study in this work CFO compensation methods for two multicarrier multiple access techniques in a high mobility scenario. In particular, we consider orthogonal frequency division multiple access (OFDMA) and filter bank multicarrier multiple access (FBMC-MA). The main motivation for this study is not only the different sensitivity these multicarrier techniques have to CFO but also the different methods they use to reduce CFO effect. In a high mobility scenario the CFO is re-estimated to follow its variation. We show that the frequency at which the CFO is re-estimated has a strong influence in the performance and the complexity of the proposed compensation methods. Additionally, we present a low-complexity CFO compensation method for OFDMA that employs a better approximation of the intercarrier interference than previous approaches. Regarding FBMC-MA, we introduce an extension of a CFO-compensation method that allows to consider a multitap channel equalizer. Finally, using simulations, we compare the performance of the compensation methods over several channel and time-varying CFO conditions.


      PubDate: 2014-07-24T23:08:08Z
       
  • Resource block Filtered-OFDM for future spectrally agile and power
           efficient systems
    • Abstract: Publication date: June 2014
      Source:Physical Communication, Volume 11
      Author(s): Jialing Li , Erdem Bala , Rui Yang
      Spectrum sharing is a common paradigm in future communication systems and a spectrally agile baseband waveform with minimal out-of-band emissions is a critical component. In this paper, we propose a new multicarrier modulation technique, called resource block Filtered-OFDM (RB-F-OFDM) and present the transceiver design. This waveform can be used over channels with non-contiguous spectrum fragments and exhibits very low adjacent channel interference, which is required for cognitive radio systems with multi channel carrier aggregation capabilities. As such, regulatory based very stringent adjacent channel leakage ratio (ACLR) and adjacent channel selectivity (ACS) requirements can be met. We show that the transceiver complexity may be reduced by utilizing an efficient polyphase implementation that is commonly used in the filter bank multicarrier (FBMC) modulation. In addition, some efficient peak-to-average power ratio (PAPR) reduction techniques can be naturally applied. The new design is backwards compatible with legacy OFDM based systems. Simulation results to evaluate the performance, including measured bit error rate (BER) in multipath channels, are provided.


      PubDate: 2014-07-24T23:08:08Z
       
  • Joint blind channel shortening and compensation of transmitter I/Q
           imbalances and CFOs for uplink SC-IFDMA systems
    • Abstract: Publication date: June 2014
      Source:Physical Communication, Volume 11
      Author(s): Donatella Darsena , Giacinto Gelli , Francesco Verde
      This paper deals with receiver design for the uplink of a single-carrier interleaved frequency-division multiple-access (SC-IFDMA) system, which is a promising candidate for non-adaptive transmission in next-generation wireless systems. In particular, channel shortening is required in asynchronous SC-IFDMA systems operating over highly-dispersive channels, since the length of the cyclic prefix (CP) is insufficient to compensate for the combined effects of timing offsets and channel dispersion; other major sources of performance degradation are the in-phase/quadrature-phase (I/Q) imbalance introduced at each transmitter, and the carrier frequency offsets (CFOs) between the transmitters and the receiver. The proposed multistage receiver is designed to jointly counteract all these impairments: specifically, the minimum mean-output energy (MMOE) criterion is adopted to synthesize a time-domain equalizer, which performs blind multiuser channel shortening of all the user channels (including the corresponding time offsets), without requiring a priori knowledge of the channel impulse responses to be shortened, or compensation of the CFOs and transmitter I/Q imbalances. Moreover, after channel shortening and (total or partial) CP removal, the MMOE criterion is also employed to compensate for the CFOs and mitigate I/Q impairments. Monte Carlo computer simulations are carried out to assess the effectiveness of the proposed receiver.


      PubDate: 2014-07-24T23:08:08Z
       
  • Editorial Board
    • Abstract: Publication date: June 2014
      Source:Physical Communication, Volume 11




      PubDate: 2014-07-24T23:08:08Z
       
  • Radio Access Beyond OFDM(A)
    • Abstract: Publication date: June 2014
      Source:Physical Communication, Volume 11
      Author(s): Huseyin Arslan , Kwang-Cheng Chen , Petri Mähönen



      PubDate: 2014-07-24T23:08:08Z
       
  • Intrinsic interference reduction in a filter bank-based multicarrier using
           QAM modulation
    • Abstract: Publication date: June 2014
      Source:Physical Communication, Volume 11
      Author(s): Rostom Zakaria , Didier Le Ruyet
      The offset QAM-based filter-bank multicarrier (FBMC/OQAM) has recently attracted a lot of research interest thanks to its high spectral efficiency. The data in the FBMC/OQAM are carried by real-valued symbols transmitted at each half period ( T / 2 ). At the receiver side, the received symbols are corrupted by pure imaginary intrinsic interference terms which prevent the application of some well-known schemes such as Alamouti coding and maximum likelihood (ML) detection in spatial multiplexing (SM) systems. Receiver schemes with interference cancellation are not always effective, due to error propagation. Interference cancellation can be effective when the signal-to-interference ratio is beyond a certain threshold. In this paper, we propose reducing the intrinsic interference power by modifying the conventional FBMC/OQAM system by transmitting QAM data symbols instead of OQAM ones. Consequently, the real orthogonality condition is no longer satisfied. On the other hand, we can show that, by using receivers based on iterative interference cancellation, we can successfully remove the intrinsic interference. We test the proposed FBMC/QAM in both schemes: 2 × 1 Alamouti coding scheme and 2 × 2 SM with ML detection. The bit-error rate performance is assessed and illustrated by Monte Carlo simulations.


      PubDate: 2014-07-24T23:08:08Z
       
  • One-bit time reversal using binary pulse sequence for indoor
           communications
    • 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
       
  • Mobile relays for enhanced broadband connectivity in high speed train
           systems
    • Abstract: Publication date: September 2014
      Source:Physical Communication, Volume 12
      Author(s): Elias Yaacoub , Rachad Atat , Ahmad Alsharoa , Mohamed-Slim Alouini
      With the introduction of wireless modems and smart phones, the passenger transport industry is witnessing a high demand to ensure not only the safety of the trains, but also to provide users with Internet access all the time inside the train. When the Mobile Terminal (MT) communicates directly with the Base Station (BS), it will experience a severe degradation in the Quality of Service due to the path loss and shadowing effects as the wireless signal is traveling through the train. In this paper, we study the performance in the case of relays placed on top of each train car. In the proposed approach, these relays communicate with the cellular BS on one hand, and with the MTs inside the train cars on the other hand, using the Long Term Evolution (LTE) cellular technology. A low complexity heuristic LTE radio resource management approach is proposed and compared to the Hungarian algorithm, both in the presence and absence of the relays. The presence of the relays is shown to lead to significant enhancements in the effective data rates of the MTs. In addition, the proposed resource management approach is shown to reach a performance close to the optimal Hungarian algorithm.


      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
       
  • Resource allocation in relay-assisted MIMO MAC systems with statistical
           CSI
    • Abstract: Publication date: September 2014
      Source:Physical Communication, Volume 12
      Author(s): Alessio Zappone , Eduard Jorswieck
      In this work, the issue of non-cooperative resource allocation in the uplink of a relay-assisted MIMO MAC (multiple input multiple output multiple access channel) system with statistical CSI (channel state information) is considered. The mobile transmitters pursue individual achievable ergodic rate maximization, whereas the relay aims at optimizing the global performance of the system. The problem is formulated as a Stackelberg game with the relay as the leader, and the multiple access users as the followers. Moreover, necessary and sufficient conditions for beamforming optimality at the relay are derived, which simplifies the resource allocation process. Finally, numerical results corroborate the theoretical findings.


      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
       
  • Editorial Board
    • Abstract: Publication date: March 2014
      Source:Physical Communication, Volume 10




      PubDate: 2014-04-27T19:25:27Z
       
  • Price-bandwidth dynamics for WSPs in heterogeneous wireless networks
    • Abstract: Publication date: Available online 18 April 2014
      Source:Physical Communication
      Author(s): S. Anand , S. Sengupta , R. Chandramouli
      This paper presents a comprehensive approach to spectrum pricing and bandwidth management for wireless service providers (WSPs) in heterogeneous wireless networks. Most approaches to spectrum management focus on revenue maximization for the WSPs. However, the key issue of the competitive edge held by a WSP over the others (i.e., its market share) is hardly addressed. The market shares of the WSPs depend on the prices they advertise and the bandwidths they provide. We develop a three phase game between WSPs. The first phase called the WSP-WSP price game enables WSPs determine the optimal price they must advertise. In the second phase, called the WSP-WSP bandwidth game, the WSPs use the Nash equilibrium of the WSP-WSP price game, to determine the optimal bandwidths they should advertise in order to maximize their market share. Finally, in the third phase, we develop a WSP-WSP trading game model the fact that users that start off with a WSP can not only demand bandwidth from that WSP, but also demand bandwidth from other WSPs in order to make best use of the available bandwidth at all the WSPs.


      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
           environment
    • 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
       
  • Macrocell–femtocells resource allocation with hybrid access
           motivational model
    • Abstract: Publication date: Available online 23 December 2013
      Source:Physical Communication
      Author(s): Hanaa Marshoud , Hadi Otrok , Hassan Barada
      Femtocell technology has emerged as an efficient cost-effective solution not only to solve the indoor coverage problem but also to cope with the growing demand requirements. This paper investigates two major design concerns in two tier networks: resource allocation and femtocell access. Base station selection together with dual bandwidth and power allocation among the two tiers are investigated under shared spectrum usage. To achieve fair and efficient resource optimization, our model assumes that hybrid access mode is applied in the femtocells. Hybrid access mode is beneficial for system performance as (1) it lessens interference caused by nearby public users, (2) it allows public users to connect to near femtocells and get better Quality of Service (QoS) and (3) it increases system capacity as it allows the macrocell to serve more users. However, femtocells’ owners can behave selfishly by denying public access to avoid any performance reduction in subscribers’ transmissions. Such a problem needs a motivation scheme to assure the cooperation of femtocells’ owners. In this paper, we propose a game-theoretical hybrid access motivational model. The proposed model encourages femtocells’ owners to share resources with public users, thus, more efficient resource allocation can be obtained. We optimize the resource allocation by means of the Genetic Algorithm (GA). The objective of the formulated optimization problem is the maximization of network throughput that is calculated by means of Shannon’s Capacity Law. Simulations are conducted where a modified version of the Weighted Water Filling (WWF) algorithm is used as a benchmark. Our proposed model, compared to WWF, achieves more efficient resource allocation in terms of system throughput and resources utilization.


      PubDate: 2013-12-28T04:32:38Z
       
  • Receiver structure and estimation of the modulation index for tamed
           frequency modulated (TFM) signals
    • Abstract: Publication date: Available online 7 December 2013
      Source:Physical Communication
      Author(s): Markku Kiviranta , Aarne Mämmelä
      Tamed frequency modulation (TFM) is a spectrally efficient constant amplitude continuous phase modulation (CPM) scheme which can be simply realized by using a frequency modulator (FM). In the implementation the modulation index of TFM is calibrated to have a nominal value of 0.5, but due to temperature variations it can drift causing time varying phase jitter. In this paper we present novel algorithms and performance results to measure and control the modulation index in a coherent receiver based on joint reduced state sequence detector (RSSD) and per-survivor processing (PSP) carrier phase estimation. The modulation index estimator measures phase transitions in the receiver and derives estimates by comparing the result to the coding rule of the TFM signal. The estimator has acquisition and tracking ability, and the current estimate can be used to replace the nominal index value. Our simulation results show that the proposed coherent receiver with the novel modulation index estimator has less than 1 dB performance degradation compared to around 4.5 dB exploiting only the PSP carrier phase estimation.


      PubDate: 2013-12-08T10:55:58Z
       
  • Detection and countermeasure of interference in slow FH/MFSK systems over
           fading channels
    • Abstract: Publication date: Available online 2 December 2013
      Source:Physical Communication
      Author(s): Aye Aung , Kah Chan Teh , Kwok Hung Li
      In this paper, we present an algorithm to detect unknown interference in slow frequency-hopped M -ary frequency-shift-keying (SFH/MFSK) systems over fading channels. Both partial-band noise interference (PBNI) and multitone interference (MTI) are considered. The proposed algorithm performs the detection process after dehopping by making use of square-law detectors. We first analyze the statistical property of the outputs of the square-law detectors over one hop duration, and an appropriate threshold level is derived for detecting the interference based on a binary hypothesis testing. We also formulate the closed-form expressions for the probabilities of detection of both types of interference experienced in any particular frequency hop. The analytical results are validated by the simulation results and they reveal that the proposed algorithm is able to provide good detection performance for both types of interference and outperforms the conventional ratio-threshold test (RTT) method.


      PubDate: 2013-12-04T04:40:03Z
       
  • LTE-Advanced and the evolution to beyond 4G (B4G) systems
    • Abstract: Publication date: Available online 20 November 2013
      Source:Physical Communication
      Author(s): Ian F. Akyildiz , David M. Gutierrez-Estevez , Ravikumar Balakrishnan , Elias Chavarria-Reyes
      Cellular networks have been undergoing an extraordinarily fast evolution in the past years. With commercial deployments of Release 8 (Rel-8) Long Term Evolution (LTE) already being carried out worldwide, a significant effort is being put forth by the research and standardization communities on the development and specification of LTE-Advanced. The work started in Rel-10 by the Third Generation Partnership Project (3GPP) had the initial objective of meeting the International Mobile Telecommunications-Advanced (IMT-Advanced) requirements set by the International Telecommunications Union (ITU) which defined fourth generation (4G) systems. However, predictions based on the wireless traffic explosion in recent years indicate a need for more advanced technologies and higher performance. Hence, 3GPP’s efforts have continued through Rel-11 and now Rel-12. This paper provides a state-of-the-art comprehensive view on the key enabling technologies for LTE-Advanced systems. Already consolidated technologies developed for Rel-10 and Rel-11 are reviewed while novel approaches and enhancements currently under consideration for Rel-12 are also discussed. Technical challenges for each of the main areas of study are pointed out as an encouragement for the research community to participate in this collective effort.


      PubDate: 2013-11-22T03:07:43Z
       
  • Performance evaluation of random linear network coding using Vandermonde
           matrix
    • Abstract: Publication date: Available online 19 November 2013
      Source:Physical Communication
      Author(s): Pallavi R. Mane , Sudhakar G. Adiga , M. Sathish Kumar
      This paper discusses random linear network coding with and without the use of a Vandermonde matrix to obtain the coding coefficients. Performance comparison of such random linear network coded networks with networks employing traditional store and forward technique are also provided. It is shown that random linear network coding using Vandermonde matrix can improve the network utilization factor by reducing the overhead compared to random linear coding that does not use Vandermonde matrix. Our numerical results show that random linear network coding with Vandermonde matrix provides considerable improvement in throughput and delay when compared to a network employing traditional store and forward strategy. An inherent feature of random linear network coding which makes it possible to employ simple encryption techniques is as well discussed.


      PubDate: 2013-11-22T03:07:43Z
       
  • Maximizing capacity with trellis exploration aided limited feedback
           precoder design for multiuser MIMO-MAC
    • Abstract: Publication date: Available online 9 November 2013
      Source:Physical Communication
      Author(s): Sayak Bose , Balasubramaniam Natarajan , Dalin Zhu
      In this paper, a linear trellis based precoding technique is proposed for maximizing multiuser MIMO capacity in a multiple access channel with inter symbol interference (ISI). We use the trellis exploration algorithm to design a precoding matrix that minimizes the interference from other users by allocating power in the appropriate eigen modes. Employing a finite number of phases, the precoder matrix for each user is first custom designed at the receiver. Then a bit sequence indicating the phase indices of the optimized precoding matrix elements for the corresponding user is fed back to the transmitter. We show that under this approach, the sum rate capacity achieved is comparable to the optimal sum-rate capacity employing the well-known water filling solution with complete channel knowledge at the transmitter for spatio-temporal vector coding (STVC). Our simulations for various multiuser MIMO cases, show that the per user precoding with limited feedback and equal power allocation strategy achieves desirable capacity gains relative to eigen beamforming and Grassmannian precoding.


      PubDate: 2013-11-10T04:30:02Z
       
 
 
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