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  Subjects -> PHYSICS (Total: 793 journals)
    - ELECTRICITY AND MAGNETISM (10 journals)
    - MECHANICS (20 journals)
    - NUCLEAR PHYSICS (48 journals)
    - OPTICS (90 journals)
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    - THERMODYNAMICS (31 journals)

PHYSICS (572 journals)            First | 1 2 3 4 5 6 | Last

Nanotechnology Magazine, IEEE     Full-text available via subscription   (Followers: 22)
Natural Science     Open Access   (Followers: 9)
Nature Communications     Open Access   (Followers: 88)
Nature Materials     Full-text available via subscription   (Followers: 58)
Nature Physics     Full-text available via subscription   (Followers: 29)
NDT & E International     Hybrid Journal   (Followers: 25)
Neutron News     Hybrid Journal  
New Journal of Physics     Open Access   (Followers: 5)
Niels Bohr Collected Works     Full-text available via subscription  
Noise & Vibration Worldwide     Full-text available via subscription   (Followers: 5)
Noise Notes     Full-text available via subscription   (Followers: 3)
Nondestructive Testing And Evaluation     Hybrid Journal   (Followers: 11)
Nonlinear Dynamics     Hybrid Journal   (Followers: 5)
NTM Zeitschrift für Geschichte der Wissenschaften, Technik und Medizin     Hybrid Journal   (Followers: 3)
Nuclear Engineering and Design     Hybrid Journal   (Followers: 9)
Nuclear Medicine and Biology     Hybrid Journal   (Followers: 1)
Open Journal of Biophysics     Open Access   (Followers: 1)
Open Journal of Fluid Dynamics     Open Access   (Followers: 5)
Open Journal of Microphysics     Open Access  
Open Physics     Open Access   (Followers: 2)
Optical Communications and Networking, IEEE/OSA Journal of     Hybrid Journal   (Followers: 7)
Optofluidics, Microfluidics and Nanofluidics     Open Access   (Followers: 1)
Organic Electronics     Hybrid Journal   (Followers: 5)
Organic Photonics and Photovoltaics     Open Access   (Followers: 2)
PAJ: A Journal of Performance and Art     Hybrid Journal   (Followers: 13)
Papers in Physics     Open Access  
Particle Physics Insights     Open Access   (Followers: 2)
Particuology     Hybrid Journal  
Pattern Recognition in Physics     Open Access   (Followers: 2)
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: 6)
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   (Followers: 2)
Physical Review C     Full-text available via subscription   (Followers: 20)
Physical Review Special Topics - Physics Education Research     Open Access   (Followers: 6)
Physical Review X     Open Access   (Followers: 9)
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: 3)
Physics and Chemistry of Liquids: An International Journal     Hybrid Journal   (Followers: 1)
Physics and Chemistry of the Earth, Parts A/B/C     Hybrid Journal   (Followers: 2)
Physics and Materials Chemistry     Open Access   (Followers: 1)
Physics Essays     Full-text available via subscription   (Followers: 1)
Physics in Medicine & Biology     Full-text available via subscription   (Followers: 11)
Physics in Perspective     Hybrid Journal   (Followers: 1)
Physics International     Open Access   (Followers: 2)
Physics Letters A     Hybrid Journal   (Followers: 11)
Physics Letters B     Open Access   (Followers: 3)
Physics of Fluids     Hybrid Journal   (Followers: 30)
Physics of Life Reviews     Hybrid Journal   (Followers: 1)
Physics of Plasmas     Hybrid Journal   (Followers: 7)
Physics of the Dark Universe     Open Access   (Followers: 1)
Physics of the Solid State     Hybrid Journal   (Followers: 2)
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: 38)
Physics World     Full-text available via subscription   (Followers: 3)
Physics-Uspekhi     Full-text available via subscription  
Physik in unserer Zeit     Hybrid Journal   (Followers: 1)
Physik Journal     Hybrid Journal  
Plasma Physics and Controlled Fusion     Hybrid Journal   (Followers: 2)
Plasma Physics Reports     Hybrid Journal   (Followers: 1)
Pramana     Open Access   (Followers: 10)
Preview     Hybrid Journal  
Proceedings of the National Academy of Sciences     Full-text available via subscription   (Followers: 473)
Proceedings of the National Academy of Sciences, India Section A     Hybrid Journal   (Followers: 3)
Progress in Materials Science     Hybrid Journal   (Followers: 22)
Progress in Planning     Hybrid Journal  
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   (Followers: 2)
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: 4)
Radiological Physics and Technology     Hybrid Journal   (Followers: 2)
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: 12)
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: 20)
Reviews of Modern Physics     Full-text available via subscription   (Followers: 19)

  First | 1 2 3 4 5 6 | Last

Journal Cover Physical Communication
  [SJR: 1.375]   [H-I: 15]   [2 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1874-4907
   Published by Elsevier Homepage  [2801 journals]
  • Performance evaluation of chaotic spreading sequences in a multi-user
           MIMO-OFDM system
    • Abstract: Publication date: Available online 29 January 2016
      Source:Physical Communication
      Author(s): Asma Ahmadinejad, Siamak Talebi
      A transmission with an acceptable performance is an important issue and is a topic of immense interest in wireless communications. In this paper, we propose an innovative solution which hires chaos theory in a “multiple-input-multiple-output, orthogonal frequency division multiplexing, code-division multiple-access (MIMO OFDM-CDMA)” system. The main goal is to improve performance by using chaotic systems as spreading codes. Since autocorrelation is an important criterion in selecting spreading codes, we investigate the autocorrelations of chaotic codes so as to choose proper sequences for spreading. Simulation results have shown that this method has better performance in comparison with other spreading codes such as the Walsh-Hadamard (WH) codes. In other word, bit-error rate has been refined and more possible code sequences are available.


      PubDate: 2016-01-31T14:58:03Z
       
  • Performance evaluation of backhaul bandwidth aggregation using a partial
           sharing scheme
    • Abstract: Publication date: Available online 21 January 2016
      Source:Physical Communication
      Author(s): Valentin Burger, Michael Seufert, Tobias Hoßfeld, Phuoc Tran-Gia
      To cope with the increasing demand of mobile devices and the limited capacity of cellular networks mobile connections are offloaded to WiFi. The access capacity is further increased, by aggregating bandwidth of WiFi access links. To analyse the performance of aggregated access links we model the most simple case of two cooperating systems interchanging capacities using an offloading scheme. The resulting analytic model is computed by means of a two-dimensional birth and death process. It can be used to seamlessly evaluate the performance of systems between partitioning and complete sharing. This allows to optimize the setting of thresholds dependent on the load of the cooperating system. Furthermore the benefit of aggregating bandwidth in different scenarios with homogeneous and heterogeneous workloads is quantified.


      PubDate: 2016-01-24T13:32:11Z
       
  • Unleashing the secure potential of the wireless physical layer: Secret key
           generation methods
    • Abstract: Publication date: Available online 16 January 2016
      Source:Physical Communication
      Author(s): Ahmed Badawy, Tarek Elfouly, Tamer Khattab, Amr Mohamed, Mohsen Guizani
      Within the paradigm of physical layer security, a physical layer characteristic is used as a common source of randomness to generate the secret key. This key is then used to encrypt the data to hide information from eavesdroppers. In this paper, we survey the most recent common sources of randomness used to generate the secret key. We present the steps used to extract the secret key from the estimated common source of randomness. We describe the metrics used to evaluate the strength of the generated key. We follow that with a qualitative comparison between different common sources of randomness along with a proposed new direction which capitalizes on hybridization of sources of randomness. We conclude by a discussion about current open research problems in secret key generation.


      PubDate: 2016-01-20T12:50:06Z
       
  • Cooperative spectrum sharing MIMO systems with successive decoding
    • Abstract: Publication date: Available online 14 January 2016
      Source:Physical Communication
      Author(s): Nikolaos I. Miridakis, Dimitrios D. Vergados, Angelos Michalas
      A spectrum sharing system with primary and secondary nodes, each equipped with an arbitrary number of antennas, is investigated. Particularly, the outage performance of an underlay cognitive system is analytically studied, in the case when the end-to-end ( e 2 e ) communication is established via an intermediate relay node. To better enhance the e 2 e communication, successive interference cancellation (SIC) is adopted, which compensates for both the transmission power constraint and the presence of interference from primary nodes. Both the relay and secondary receiver perform unordered SIC to successively decode the multiple streams, whereas the decode-and-forward relaying protocol is used for the e 2 e communication. New closed-form expressions for the e 2 e outage performance of each transmitted stream are derived in terms of finite sum series of the Tricomi confluent hypergeometric function. In addition, simplified yet tight approximations for the asymptotic outage performance are obtained. Useful engineering insights are manifested, such as the diversity order of the considered system and the impact of interference from the primary nodes in conjunction with the constrained transmission power of the secondary nodes.


      PubDate: 2016-01-15T11:19:49Z
       
  • Further results on multicarrier MFSK based underwater acoustic
           communications
    • Abstract: Publication date: Available online 2 January 2016
      Source:Physical Communication
      Author(s): Xingyu Cai, Lei Wan, Yi Huang, Shengli Zhou, Zhijie Shi
      Multicarrier M -ary frequency shift keying (MFSK), a parallel transmission of multiple MFSK data streams, is one basic reference scheme for underwater acoustic communications due to low-complexity incoherent processing at the receiver and ease of implementation. In this paper, we provide some further results for multicarrier MFSK based on the recent development of coherent orthogonal frequency division multiplexing (OFDM) schemes. Specifically, we adopt an OFDM based representation, develop a residual Doppler shift compensation approach at the receiver, and present different ways of computing the soft likelihood information for multicarrier MFSK transmissions in combination with nonbinary channel coding. As compared with coherent OFDM, simulation and semi-experimental results show that multicarrier MFSK has consistent performance in channels with different numbers of paths and in environments with different types of external noise.


      PubDate: 2016-01-05T07:28:30Z
       
  • Impact of the knowledge of nodes’ positions on spectrum sensing
           strategies in cognitive networks
    • Abstract: Publication date: Available online 22 December 2015
      Source:Physical Communication
      Author(s): Andrea Abrardo, Marco Martalò, Gianluigi Ferrari
      In this paper, we focus on cognitive wireless networking, where a primary wireless network (PWN) is co-located with a cognitive (or secondary) wireless network (CWN). The shared frequency spectrum is divided into disjoint “subchannels” and each subchannel is “freely” assigned (in a unique way) to a node of the PWN, denoted as primary user equipment (PUE). We assume that the nodes of the CWN, denoted as cognitive user equipments (CUEs), cooperate to sense the frequency spectrum and estimate the idle subchannels which can be used by the CWN (i.e., assigned to CUEs) without interfering the PWN. The sensing correlation among the CUEs is exploited to improve the reliability of the decision, taken by a secondary fusion center (FC), on the occupation status (by a node of the PWN) of each subchannel. In this context, we compute the mutual information between the occupation status and the observations at the FC, with and without knowledge of the positions of the nodes in the network, showing a potential significant benefit brought by this side information. Then, we derive the fusion rules at the FC: our numerical results, in terms of the network-wise probabilities of missed detection (MD) and false alarm (FA) at the secondary FC, indicate a significant performance improvement when knowledge of the CUEs’ positions is available at the secondary FC, confirming the mutual information-based theoretical prediction.


      PubDate: 2015-12-24T02:25:39Z
       
  • On the existence of an MVU estimator for target localization with
           censored, noise-free binary detectors
    • Abstract: Publication date: Available online 22 December 2015
      Source:Physical Communication
      Author(s): Arian Shoari, Alireza Seyedi
      The problem of target localization with censored noise-free binary detectors is considered. In this setting only the detecting sensors report their locations to the fusion center. It is proven that if the radius of detection is unknown to the fusion center, a minimum variance unbiased (MVU) estimator does not exist. Also it is shown that when the radius is known the center of mass of the possible target region is the MVU estimator among estimators that are invariant under Euclidean motion. In addition, a sub-optimum estimator is introduced whose performance is close to the MVU estimator but is preferred computationally. Moreover, for the case when the radius of detection is unknown a sub-optimum estimator is proposed that performs close to the Clairvoyant estimator. Furthermore, minimal sufficient statistics have been provided, both when the detection radius is known and when it is not. Simulations confirmed that the derived MVU estimator outperforms several heuristic location estimators.


      PubDate: 2015-12-24T02:25:39Z
       
  • Random neural network based novel decision making framework for optimized
           and autonomous power control in LTE uplink system
    • Abstract: Publication date: Available online 17 December 2015
      Source:Physical Communication
      Author(s): Ahsan Adeel, Hadi Larijani, Ali Ahmadinia
      This paper presents a novel decision making framework for cognitive radio networks. The traditional continuous process of sensing, analysis, reasoning, and adaptation in a cognitive cycle has been divided into two levels. In the first level, the process of sensing and adaptation runs over the radio transmission hardware during run-time. In the second level, the process of analysis and reasoning runs in the background in offline mode. This arrangement offloads the convergence time and complexity problem of reasoning process during run-time. For implementation of the first level, a random neural network (RNN) based controller trained on an open loop case based database on the cloud has been designed. For the second level, a genetic algorithm (GA) based reasoning and an RNN based learning has been developed. The proposed framework is used to address the uplink power control problem of long-term evolution (LTE) system. The performance of RNN is compared with artificial neural network (ANN) and state-of-the-art fractional power control (FPC) scheme in terms of essential cognitive engine (CE) design requirements, capacity, and coverage optimization (CCO). The simulation results have shown that RNN based CE can achieve comparable results with faster adaptation, even subject to severe environment changes without the need of retraining.


      PubDate: 2015-12-20T01:30:36Z
       
  • Route selection for interference minimization to primary users in
           cognitive radio ad hoc networks: A cross layer approach
    • Abstract: Publication date: Available online 17 December 2015
      Source:Physical Communication
      Author(s): Surajit Basak, Tamaghna Acharya
      An opportunistic routing problem in a cognitive radio ad hoc network is investigated with an aim to minimize the interference to primary users (PUs) and under the constraint of a minimum end-to-end data rate for secondary users (SUs). Both amplify-and-forward (AF) and decode-and-forward (DF) relaying techniques are considered for message forwarding by SU nodes in the network. Unlike popular transmit power control based solutions for interference management in cognitive radio networks, we adopt a cross layer approach. The optimization problem is formulated as a joint power control, channel assignment and route selection problem. Next, closed form expression for transmission power is derived and corresponding channel selection scheme and routing metric are designed based on this solution. The proposed route selection schemes are shown to depend not only on gains of the interference channels between SUs and PUs but also on the values of the spectrum sensing parameters at the SU nodes in the network. Two distributed routing schemes are proposed based on our analysis; (i) optimal_DF and (ii) suboptimal_AF. The routing schemes could be implemented using existing table driven as well as on demand routing protocols. Extensive simulation results are provided to evaluate performance of our proposed schemes in random multihop networks. Results show significant reduction in PUs’ average interference experience and impressive performance as opportunistic routing schemes can be achieved by our schemes compared to traditional shortest path based routing schemes. Performance improvement is also reported over prominent recent schemes.


      PubDate: 2015-12-20T01:30:36Z
       
  • Self-interference cancellation in full-duplex wireless with IQ imbalance
    • Abstract: Publication date: Available online 19 December 2015
      Source:Physical Communication
      Author(s): Manabu Sakai, Hai Lin, Katsumi Yamashita
      To achieve full-duplex wireless communication, the most essential issue is to eliminate in-band self-interference caused by simultaneous transmission and reception. In this paper, we investigate the impact of transmitter IQ imbalance on digital signal processing (DSP)-assisted analog self-interference cancellation, where two transmitters are used for transmission and cancellation, respectively. Our result implies that the transmitter IQ imbalance results in residual self-interference after conventional DSP-assisted analog cancellation, which still has a much higher power compared to the desired signal. Then, a baseband cancellation signal generated by widely linear (WL) filtering is proposed to effectively handle the transmitter IQ imbalance, and the optimal WL filter and the adaptive algorithm to obtain them can be derived. The impact of receiver IQ imbalance on the proposed adaptive algorithm is analyzed, and we show that the algorithm is capable of obtaining the same optimal WL filter despite receiver IQ imbalance. In addition, for practical implementation, we propose an adaptive algorithm based on the augmented complex least mean squares (ACLMS) method to obtain the WL filter, where no information about the transmitter and receiver IQ imbalances is needed. The steady state behaviors of the proposed adaptive algorithms are analyzed and the performance bounds are derived. Numerical simulation results confirm the validity and superior performance of the proposed ACLMS algorithm in various practical scenarios of transmitter and receiver IQ imbalances. Also, the tolerance of the proposed algorithm to other transceiver impairments was investigated using simulations.


      PubDate: 2015-12-20T01:30:36Z
       
  • DSP based real-time single carrier underwater acoustic communications
           using frequency domain turbo equalization
    • Abstract: Publication date: Available online 2 December 2015
      Source:Physical Communication
      Author(s): Bo Peng, Hefeng Dong
      In this paper, a DSP based real-time single carrier underwater acoustic communication system is developed. The designed receiver system operates in frequency domain for low complexity equalization. The turbo principle is incorporated into channel equalization and channel estimation processes to improve the system reliability. The channel is treated as stable within each small block and iteratively estimated based on LMS method and soft information provided by channel decoder. The soft LMS channel estimation is able to achieve better performance than conventional phase compensation scheme in single carrier frequency domain system. The receiver system is implemented on a floating point DSP running at 350 MHZ. Through careful optimization, the real-time processing is achieved with sufficient margin for both single-hydrophone receiver and multi-hydrophone systems. The designed system has been tested by both tank experiment and sea trials and achieves satisfied performance.


      PubDate: 2015-12-06T20:49:01Z
       
  • Radio access technology selection in heterogeneous networks
    • Abstract: Publication date: Available online 2 December 2015
      Source:Physical Communication
      Author(s): Kinda Khawam, Samer Lahoud, Marc Ibrahim, Mohamad Yassin, Steven Martin, Melhem El Helou, Farah Moety
      The migration of wireless networking towards the 5G era is distinguished by the proliferation of various Radio Access Technologies (RAT). As no existing technology can be surrogated by another one, the coexistence of today wireless networks is the best solution at hand when dealing with the incessantly growing user demand for bandwidth. Hence, in this heterogeneous environment, users will be able to utilize services through diverse RATs. RAT selection is crucial and must be designed astutely to avoid resource wastage. In this paper, we consider the downlink of a heterogeneous network with two broadband RATs: a primary RAT such as LTE, and a secondary RAT such as WiFi. We start by formulating a centralized approach for the RAT selection as an optimization problem. Then, two distributed approaches are proposed for adequate RAT selection: first, we put forward distributed heuristic algorithms based on the peak rate perceived by users from available RATs. Second, we devise a distributed RAT selection scheme portrayed as a non-cooperative game with a learning-based algorithm to reach the Nash Equilibriums of the RAT selection game. Extensive simulation results show that the proposed distributed algorithms give efficient results compared to the centralized optimal approach. The analysis of the simulation results enables to define pertinent use cases that delimit the scope of the proposed optimal centralized and distributed approaches.


      PubDate: 2015-12-06T20:49:01Z
       
  • Editorial Board
    • Abstract: Publication date: December 2015
      Source:Physical Communication, Volume 17




      PubDate: 2015-12-01T19:27:12Z
       
  • Doppler-aided localization of mobile nodes in an underwater distributed
           antenna system
    • Abstract: Publication date: Available online 1 December 2015
      Source:Physical Communication
      Author(s): Patrick Carroll, Katherine Domrese, Hao Zhou, Shengli Zhou, Peter Willett
      In this paper, we consider a problem of localizing a moving object in the context of an underwater distributed antenna system. All the distributed nodes record the time-of-arrivals of a single message from the moving object and obtain the Doppler speed estimates used in the decoding process. Conventional methods have relied only on the time-of-arrival measurements to obtain position estimates, on top of which filtering methods can be further applied for tracking purposes. In this work, we explore the usefulness of Doppler speed information. The combination of time-of-arrival measurements and Doppler speed estimates associated with a single message enhances the accuracy of position estimation and provides an estimate of the velocity of the mobile object. A Kalman Filter (KF) and a Probabilistic Data Association Filter (PDAF) are further implemented processing the point estimates. Simulations show that the proposed Doppler-aided methods improve both the point estimation and tracking filter performance, which is verified using data from pool tests.


      PubDate: 2015-12-01T19:27:12Z
       
  • Inter-cellular scheduler for 5G wireless networks
    • Abstract: Publication date: Available online 1 December 2015
      Source:Physical Communication
      Author(s): Cédric Gueguen, Mahdi Ezzaouia, Mohamad Yassin
      Enhancing the Quality of Experience (QoE) in wireless networks is a crucial issue. Many acknowledged works focus on intra-cellular scheduling. They have shown that when the channel impairment is taken into consideration by the opportunistic scheduling approaches, it allows to reach higher throughputs and, for the most efficient ones, a higher fairness. However, if some of these works provide results near to optimum considering a single cell, high QoE cannot be guaranteed for scenarios where the cells are overloaded. In this article, we propose a new inter-cellular scheduler able to help the overloaded cells thanks to a dynamic cell bandwidth allocation. Our resource allocation technique is based on an adequate emergency parameter called Mean Cell Packet Delay Outage Ratio (MCPDOR). Performance evaluation shows that the proposed scheduler widely outperforms existing solutions in various scenarios. A variant of our solution that does not consider MCPDOR is also proposed and evaluated.


      PubDate: 2015-12-01T19:27:12Z
       
  • Special issue on radio access network architectures and resource
           management for 5G
    • Abstract: Publication date: Available online 23 November 2015
      Source:Physical Communication
      Author(s): J. Pérez-Romero, X. Lagrange, J. Nasreddine, J. Marquez-Barja



      PubDate: 2015-11-27T18:45:13Z
       
  • SDN/NFV-enabled satellite communications networks: Opportunities,
           scenarios and challenges
    • Abstract: Publication date: Available online 10 November 2015
      Source:Physical Communication
      Author(s): R. Ferrús, H. Koumaras, O. Sallent, G. Agapiou, T. Rasheed, M.-A. Kourtis, C. Boustie, P. Gélard, T. Ahmed
      In the context of next generation 5G networks, the satellite industry is clearly committed to revisit and revamp the role of satellite communications. As major drivers in the evolution of (terrestrial) fixed and mobile networks, Software Defined Networking (SDN) and Network Function Virtualisation (NFV) technologies are also being positioned as central technology enablers towards improved and more flexible integration of satellite and terrestrial segments, providing satellite network further service innovation and business agility by advanced network resources management techniques. Through the analysis of scenarios and use cases, this paper provides a description of the benefits that SDN/NFV technologies can bring into satellite communications towards 5G. Three scenarios are presented and analysed to delineate different potential improvement areas pursued through the introduction of SDN/NFV technologies in the satellite ground segment domain. Within each scenario, a number of use cases are developed to gain further insight into specific capabilities and to identify the technical challenges stemming from them.


      PubDate: 2015-11-18T16:16:32Z
       
  • What will interference be like in 5G HetNets?
    • Abstract: Publication date: Available online 23 October 2015
      Source:Physical Communication
      Author(s): Janne Riihijärvi, Petri Mähönen, Marina Petrova
      In this paper we discuss challenges in interference modeling for performance analysis of future wireless networks. We show through detailed numerical and simulation case studies as well as through measurements that many of the commonly used models result in potentially highly inaccurate predictions of interference and performance. In particular, we identify correlations in node locations, three-dimensional structure of future network deployments, and complexity of in-building and inter-building radio propagation as key domains where further research is needed. We also discuss in detail potential approaches to be taken as starting points for new research in these domains.


      PubDate: 2015-11-18T16:16:32Z
       
  • On achievable rate of massive MIMO multiple access channels via virtual
           representation
    • Abstract: Publication date: Available online 27 October 2015
      Source:Physical Communication
      Author(s): Yun Xue, Jun Zhang, Shi Jin, Xiqi Gao
      This paper investigates the uplink achievable rates of massive multiple-input multiple-output (MIMO) systems in correlated fading channels via virtual representation. The fast fading MIMO channel matrix is assumed to have a Rayleigh-distributed random component with variance profile. Under the minimum mean-squared error receiver employed, we first derive the first and second asymptotic moments of signal-to-interference-plus-noise ratio (SINR). Then, we propose that the probability distribution function of SINR, which can be well approximated by a Gamma distribution. Finally, we derive a lower bound on the SINR and approximation of achievable rate. Numerical results demonstrate that both the lower bound on the SINR and the approximated rate apply for a finite number of antennas and remain tight.


      PubDate: 2015-11-18T16:16:32Z
       
  • On error rate performance of multi-cell massive MIMO systems with linear
           receivers
    • Abstract: Publication date: Available online 4 November 2015
      Source:Physical Communication
      Author(s): Haiquan Wang, Meijun Zhou, Ruiming Chen, Wei Zhang
      For an uplink of multi-cell multiuser (MU) Multiple-Input, Multiple-Output (MIMO) system, where each cell has a Base Station (BS) with M antennas and K users with single antenna, the Zero-Forcing (ZF) decoder and the Minimal Mean-Square Error (MMSE) decoder are considered. Upper bounds, lower bounds on Pair-wise Error Probability (PEP) of these decoders are derived. Moreover, analytic expressions of approximations on PEP are given. These show that, if the BS knows Channel State Information (CSI) in its own cell only and does not have CSI in other cells, error floors will occur even when Signal-to-Noise Ratio (SNR) goes to infinity for both the ZF decoder and the MMSE decoder, while these error floors disappear when M goes to large. All theoretical results above are confirmed by simulations. Especially, the approximations of PEP match up with simulation results very well.


      PubDate: 2015-11-18T16:16:32Z
       
  • A survey on 5G: The next generation of mobile communication
    • Abstract: Publication date: Available online 11 November 2015
      Source:Physical Communication
      Author(s): Nisha Panwar, Shantanu Sharma, Awadhesh Kumar Singh
      The rapidly increasing number of mobile devices, voluminous data, and higher data rate are pushing to rethink the current generation of the cellular mobile communication. The next or fifth generation (5G) cellular networks are expected to meet high-end requirements. The 5G networks are broadly characterized by three unique features: ubiquitous connectivity, extremely low latency, and very high-speed data transfer. The 5G networks would provide novel architectures and technologies beyond state-of-the-art architectures and technologies. In this paper, our intent is to find an answer to the question: “what will be done by 5G and how?” We investigate and discuss serious limitations of the fourth generation (4G) cellular networks and corresponding new features of 5G networks. We identify challenges in 5G networks, new technologies for 5G networks, and present a comparative study of the proposed architectures that can be categorized on the basis of energy-efficiency, network hierarchy, and network types. Interestingly, the implementation issues, e.g., interference, QoS, handoff, security-privacy, channel access, and load balancing, hugely effect the realization of 5G networks. Furthermore, our illustrations highlight the feasibility of these models through an evaluation of existing real-experiments and testbeds.


      PubDate: 2015-11-18T16:16:32Z
       
  • Design and implementation of spectrum sensing for cognitive radios with a
           frequency-hopping primary system
    • Abstract: Publication date: Available online 30 September 2015
      Source:Physical Communication
      Author(s): Sanjeev Gurugopinath, Raghavendra Akula, Chandra R. Murthy, R. Prasanna, Bharadwaj Amruthur
      In this work, spectrum sensing for cognitive radios is considered in the presence of multiple Primary Users (PU) using frequency-hopping communication over a set of frequency bands. The detection performance of the Fast Fourier Transform (FFT) Average Ratio (FAR) algorithm is obtained in closed-form, for a given FFT size and number of PUs. The effective throughput of the Secondary Users (SU) is formulated as an optimization problem with a constraint on the maximum allowable interference on the primary network. Given the hopping period of the PUs, the sensing duration that maximizes the SU throughput is derived. The results are validated using Monte Carlo simulations. Further, an implementation of the FAR algorithm on the Lyrtech (now, Nutaq) small form factor software defined radio development platform is presented, and the performance recorded through the hardware is observed to corroborate well with that obtained through simulations, allowing for implementation losses.


      PubDate: 2015-10-03T16:11:04Z
       
  • QPSK waveform for MIMO radar with spectrum sharing constraints
    • Abstract: Publication date: Available online 25 September 2015
      Source:Physical Communication
      Author(s): Awais Khawar, Ahmed Abdelhadi, T. Charles Clancy
      Multiple-input multiple-output (MIMO) radar is a relatively new concept in the field of radar signal processing. Many novel MIMO radar waveforms have been developed by considering various performance metrics and constraints. In this paper, we show that finite alphabet constant-envelope (FACE) quadrature-pulse shift keying (QPSK) waveforms can be designed to realize a given covariance matrix by transforming a constrained nonlinear optimization problem into an unconstrained nonlinear optimization problem. In addition, we design QPSK waveforms in a way that they don’t cause interference to cellular system, by steering nulls towards a selected base station (BS). The BS is selected according to our algorithm which guarantees minimum degradation in radar performance due to null space projection (NSP) of radar waveforms. We design QPSK waveforms with spectrum sharing constraints for stationary and moving radar platform. We show that the waveform designed for stationary MIMO radar matches the desired beampattern closely, when the number of BS antennas N BS is considerably less than the number of radar antennas M , due to quasi-static interference channel. However, for moving radar the difference between designed and desired waveforms is larger than stationary radar, due to rapidly changing wireless channel.


      PubDate: 2015-09-25T14:26:58Z
       
  • Multiple trellis-coded modulation, per-survivor processing and
           Reed-Solomon coding in the presence of phase noise
    • Abstract: Publication date: Available online 25 September 2015
      Source:Physical Communication
      Author(s): Markku Kiviranta, Aarne Mämmelä
      The aim of this paper is to consider trellis coded modulation (TCM) in the presence of phase noise. The starting point is a two-dimensional 32 point cross (32-CR) signal set that has served as a benchmark for other power and bandwidth efficient modulation schemes. Per-survivor processing (PSP) is used for carrier phase estimation, and both the phase acquisition (transient state) and phase tracking (steady state) performances are considered in an additive white Gaussian noise (AWGN) channel, in which phase offset or time varying phase noise is introduced. Based on the theoretical and simulation results it can be said that the 32-CR constellation is itself more sensitive to a phase error rather than the PSP algorithm. Due to the phase error the TCM scheme becomes a catastrophic code. Possible solutions include stringent phase noise requirements for oscillators, multiple trellis-coded modulation (MTCM) and concatenated TCM and Reed-Solomon (RS) coding. Our simulation results show that a simple combined MTCM, PSP and RS scheme has around 3 dB advantage at compared to the pure TCM and PSP in the presence of phase noise. A semianalytical approach is used for performance evaluation, and the method is a particularly convenient tool to determine the rate of RS coding in detail.


      PubDate: 2015-09-25T14:26:58Z
       
  • Direction Finding of rogue Wi-Fi access points using an off-the-shelf
           MIMO-OFDM receiver
    • Abstract: Publication date: Available online 25 September 2015
      Source:Physical Communication
      Author(s): Asaf Tzur, Ofer Amrani, Avishai Wool
      Elimination of rogue Access Points (APs) is a challenging security goal of growing interest and practical importance. However, even when network administrators suspect that such devices are indeed present to attack their organization, physically locating their whereabout is an intricate task. In this work a method is suggested for implementing autonomous Direction Finding (DF), i.e., an apparatus for passively identifying the Angle-of-Arrival (AoA) of a received Wi-Fi signal, using a standard off-the-shelf Wi-Fi receiver. Modern wireless communication standards, such as Wi-Fi (e.g. IEEE 802.11n), are based on Orthogonal Frequency Division Multiplexing (OFDM) and Multiple-Input Multiple-Output (MIMO) technologies. The key contribution of the current work is an approach of employing the multiple receiving antennas jointly with OFDM Channel State Information (CSI) as the basis for implementing an interferometry DF tool. This approach is theoretically investigated via numeric analysis, and practically validated by a working prototype. The performance of the prototype was evaluated both in the laboratory, in a sterile environment, as well as in field trials. In realistic indoor setting the prototype was able to acquire the AoA with a median error of 8–15 degrees.


      PubDate: 2015-09-25T14:26:58Z
       
  • Error exponent analysis of energy-based Bayesian decentralized spectrum
           sensing under fading
    • Abstract: Publication date: Available online 7 September 2015
      Source:Physical Communication
      Author(s): Sanjeev Gurugopinath, Chandra R. Murthy, Vinod Sharma
      This paper considers decentralized spectrum sensing, i.e., detection of occupancy of the primary users’ spectrum by a set of Cognitive Radio (CR) nodes, under a Bayesian set-up. The nodes use energy detection to make their individual decisions, which are combined at a Fusion Center (FC) using the K -out-of- N fusion rule. The channel from the primary transmitter to the CR nodes is assumed to undergo fading, while that from the nodes to the FC is assumed to be error-free. In this scenario, a novel concept termed as the Error Exponent with a Confidence Level (EECL) is introduced to evaluate and compare the performance of different detection schemes. Expressions for the EECL under general fading conditions are derived. As a special case, it is shown that the conventional error exponent both at individual sensors, and at the FC is zero. Further, closed-form lower bounds on the EECL are derived under Rayleigh fading and lognormal shadowing. As an example application, it answers the question of whether to use pilot-signal based narrowband sensing, where the signal undergoes Rayleigh fading, or to sense over the entire bandwidth of a wideband signal, where the signal undergoes lognormal shadowing. Theoretical results are validated using Monte Carlo simulations.


      PubDate: 2015-09-12T11:10:35Z
       
  • A novel user pairing scheme for functional decode-and-forward multi-way
           relay network
    • Abstract: Publication date: Available online 11 September 2015
      Source:Physical Communication
      Author(s): Shama N. Islam, Salman Durrani, Parastoo Sadeghi
      In this paper, we consider a functional decode and forward (FDF) multi-way relay network (MWRN) where a common user facilitates each user in the network to obtain messages from all other users. We propose a novel user pairing scheme, which is based on the principle of selecting a common user with the best average channel gain. This allows the user with the best channel conditions to contribute to the overall system performance. Assuming lattice code based transmissions, we derive upper bounds on the average common rate and the average sum rate with the proposed pairing scheme. Considering M -ary quadrature amplitude modulation with square constellation as a special case of lattice code transmission, we derive asymptotic average symbol error rate (SER) of the MWRN. We show that in terms of the achievable rates, the proposed pairing scheme outperforms the existing pairing schemes under a wide range of channel scenarios. The proposed pairing scheme also has lower average SER compared to existing schemes. We show that overall, the MWRN performance with the proposed pairing scheme is more robust, compared to existing pairing schemes, especially under worst case channel conditions when majority of users have poor average channel gains.


      PubDate: 2015-09-12T11:10:35Z
       
  • Outlier-aware cooperative spectrum sensing in cognitive radio networks
    • Abstract: Publication date: Available online 9 September 2015
      Source:Physical Communication
      Author(s): Gaurav Kapoor, Ketan Rajawat
      This paper considers the problem of cooperative spectrum sensing in cognitive radio networks (CRN). Communication in CRNs may be disrupted due to the presence of malicious secondary users (SU) or channel impairments such as shadowing. This paper proposes a spatio-frequency framework that can detect and track malicious users and anomalous measurements in CRNs. The joint problem of spectrum sensing and malicious user identification is posed as an optimization problem that aims to exploit the sparsity inherent to both, spectrum occupancy and malicious user occurrence. Proposed scheme obtains improved performance by utilizing node location information, and can handle missing or inaccurate location information, and noisy SU reports. A distributed block-coordinate descent-based algorithm is proposed that is shown to outperform the state-of-the-art PCA-based approach, and is flexible enough to defeat a variety of attacks encountered in SU networks. An online algorithm, that can handle incorporate multiple SU readings sequentially and adapt to time-varying channels, primary user, and malicious user activity, is also proposed and shown to be consistent. Simulation results demonstrate the efficacy of the proposed algorithms.


      PubDate: 2015-09-12T11:10:35Z
       
  • A low complexity detection/decoding algorithm for NB-LDPC coded PRCPM
           system
    • Abstract: Publication date: Available online 11 September 2015
      Source:Physical Communication
      Author(s): Xiying Liu, Shancheng Zhao, Xiao Ma
      This paper studies the combination of non-binary low-density parity-check (NB-LDPC) codes and M -ary partial response continuous phase modulation (PRCPM). A low-complexity joint detection/decoding algorithm is proposed, which is referred to as the Max-Log-MAP/ X -EMS algorithm. In this joint algorithm, the CPM detector is implemented by the Max-Log-MAP algorithm while the LDPC decoder is implemented by the Extended Min-Sum (EMS) algorithms. Three kinds of EMS algorithms, including D -EMS, T -EMS, and M -EMS algorithms, are compared, which are referred to as X -EMS algorithm for convenience. Simulation results show that the Max-Log-MAP/ X -EMS algorithm performs as well as the traditional iterative detection/decoding algorithm based on the BCJR algorithm and the QSPA algorithm, but with lower complexity. In addition, comparison of the proposed NB-LDPC coded PRCPM system with the eBCH coded PRCPM system is given, which shows the performance advantages of our system.


      PubDate: 2015-09-12T11:10:35Z
       
  • A DEC-MDP model for joint uplink/downlink resource management in
           OFDMA-based networks
    • Abstract: Publication date: Available online 5 September 2015
      Source:Physical Communication
      Author(s): Ahmad M. El-Hajj, Dusit Niyato, Zaher Dawy
      With the advent of mobile services with asymmetric and symmetric quality of service (QoS) requirements, traditional single link resource allocation techniques have started to show some limitations in handling the complex requirements. To address these issues, joint uplink/downlink resource management approaches were recently introduced where both communications links are jointly considered in the resource management process. One direct consequence of this coupling is a modification of the underlying queueing behavior since the decision making process in one direction in terms of transmission rate now depends on the performance achieved in the opposite direction. In this paper, we present a modeling approach of the decision making process that takes place under the joint uplink/downlink resource management framework. Using decentralized Markov decision processes (DEC-MDP) as a model and gradient ascent methods as an optimization technique, we formulate and solve the joint uplink/downlink decision making process. The uplink and downlink of each user are considered as agents. Assuming certain subcarrier and power allocation schemes, we investigate the resource usage in the uplink and downlink to achieve a certain delay balancing constraint where the total delay in the uplink and downlink is bound by a pre-determined threshold. The approach followed starts by modeling the problem in hand using DEC-MDPs. After discussing the different aspects of the model, the solution using gradient ascent is described. Simulation results illustrate the different dimensions of the problem and their impact on the resource management process.


      PubDate: 2015-09-07T10:11:29Z
       
  • Performance evaluation of improved double-threshold energy detector over
           Rayleigh-faded sensing and imperfect reporting channels
    • Abstract: Publication date: Available online 21 August 2015
      Source:Physical Communication
      Author(s): Ramtin Rabiee, Kwok Hung Li
      Cognitive radio (CR) has been viewed as a promising solution to spectrum scarcity. In order to design a reliable CR system, many improvements have been proposed to enhance spectrum sensing performance of secondary users (SUs) in a CR network (CRN). Sensing reliability and transmission throughput of SUs are two important performance criteria, which should be optimized to enhance signal protection of primary user (PU) as well as spectrum utilization rate. In this paper, we consider Rayleigh-faded sensing channels and SUs use improved energy detector (IED) to make their local decisions. The final decision is made in a fusion center (FC) through the cooperative spectrum sensing (CSS) scheme with erroneous reporting channels. We show that the improved double-threshold energy detector (IDED) outperforms the conventional energy detector (CED) in terms of the total error rate. Furthermore, we evaluate the transmission throughput of the CRN through various ED schemes with detection constraints over both perfect and imperfect reporting channels. We show that the IDED has the highest achievable throughput among different ED schemes over imperfect reporting channels.


      PubDate: 2015-08-25T08:35:52Z
       
  • Communicate to illuminate: State-of-the-art and research challenges for
           visible light communications
    • Abstract: Publication date: Available online 24 August 2015
      Source:Physical Communication
      Author(s): Ozgur Ergul, Ergin Dinc, Ozgur B. Akan
      In the near future, the available radio-frequency (RF) bandwidth will not be sufficient to meet the ever increasing demand for wireless access. Visible light communication (VLC) is an alternative method to reduce the burden of RF-based communication, especially in indoor communications. 70 % of the communication is indoors, and light emitting diode (LED) arrays are spreading for illumination purposes thanks to their low energy and higher lifetime. VLC can be realized as a secondary application in LED arrays that are placed for lighting. In this way, some of the wireless traffic can be sent using light, with less cost and less carbon footprint. For these reasons, VLC attracts significant research interests. We provide an extensive survey of the current literature by outlining challenges and future research areas in order to facilitate future research in this area.


      PubDate: 2015-08-25T08:35:52Z
       
  • Editorial Board
    • Abstract: Publication date: September 2015
      Source:Physical Communication, Volume 16




      PubDate: 2015-07-27T14:07:38Z
       
  • The combination of aggregation, ARQ, QoS guarantee and mapping of
           Application flows in Very High Throughput 802.11ac networks
    • Abstract: Publication date: Available online 17 July 2015
      Source:Physical Communication
      Author(s): Oran Sharon, Yaron Alpert
      We investigate the performance of the IEEE 802.11ac MAC layer Aggregation schemes in light of QoS guarantee with the use of an ARQ protocol, and in very high PHY rates. The investigation is done in different models of mapping Application flows into Traffic Streams and Access Categories. We show that when the IEEE 802.11ac ARQ protocol is used with relatively high bit error rates, it is not effective to use the full aggregation capability. Second, we show that there is not one best model of mapping Application flows into Traffic Streams and Access Categories. In particular, using two Access Categories is sometimes less efficient than using one.


      PubDate: 2015-07-19T08:33:46Z
       
  • Optimal downlink power allocation in cellular networks
    • Abstract: Publication date: Available online 9 July 2015
      Source:Physical Communication
      Author(s): Ahmed Abdelhadi , Awais Khawar , T. Charles Clancy
      In this paper, we introduce a novel approach for power allocation in cellular networks. In our model, we use sigmoidal-like utility functions to represent different users’ modulation schemes. Each utility function is a representation of the probability of successfully transmitted packets per unit of power consumed by a user, when using a certain modulation scheme. We consider power allocation with utility proportional fairness policy, where the fairness among users is in utility percentage i.e. percentage of successfully transmitted packets of the corresponding modulation scheme. We formulate our power allocation optimization problem as a product of utilities of all users and prove that it is convex and therefore the optimal solution is tractable. We present a distributed algorithm to allocate base station powers optimally with priority given to users running lower modulation schemes while ensuring non-zero power allocation to users running higher modulation schemes. Our algorithm prevents fluctuation in the power allocation process and is capable of traffic and modulation dependent pricing policy. This can be used to flatten traffic and decrease the service price for users. We also compare our results with a benchmark algorithm and show that our algorithm performs better in allocating powers fairly to all users without dropping any user in order to maximize performance.


      PubDate: 2015-07-15T05:16:53Z
       
  • Analysis of degrees of freedom under mixture Gaussian model in cognitive
           radio systems
    • Abstract: Publication date: September 2015
      Source:Physical Communication, Volume 16
      Author(s): Ahsan-Abbas Ali , Shuangqing Wei
      We propose a mixture-Gaussian model for a cognitive radio channel to analyze the interplay between the interference in the system and the degrees-of-freedom (DOF), i.e., the average number of channel uses per transmission frame, used by the secondary user (SU) for communications in the long run. In contrast to the conventional studies, we assume that the SU receiver (SU-RX) does not precisely know whether the primary-user (PU) transmitter is on or off. Due to this assumption the resulting interference channel is mixture-Gaussian. Our objective is to find the optimal sensing threshold and sensing time for the signal detector used by the SU transmitter (SU-TX). Our formulation of the optimization problem reflects the trade-off between SU-TX’s DOF for communications and that for detection. Both the DOFs affect PU’s interference to SU, and SU’s interference to PU. The latter interference causes PU performance degradation, which is kept within tolerable range as a constraint. As a further contribution, we define interference regimes for SU performance on the basis of PU transmission power level. We also address the scenario when PU receiver uses the nearest neighbor decoding while wrongly anticipating that the channel is Gaussian. Finally, we demonstrate that even if SU-TX’s signal detector performs suboptimally, SU can still achieve the optimal detector’s performance in the high interference regime by adjusting the sensing parameters.


      PubDate: 2015-07-09T01:54:33Z
       
  • Adaptive RAKE receiver in chaos based pilot-added DS-CDMA system
    • Abstract: Publication date: Available online 27 May 2015
      Source:Physical Communication
      Author(s): Meher Krishna Patel , Stevan M. Berber , Kevin W. Sowerby
      This paper presents the theoretical analysis of adaptive multiuser RAKE receiver scheme in frequency selective fading channel for direct-sequence code division multiple access (DS-CDMA) system. Least mean square (LMS) algorithm is used to estimate the channel coefficients. Chaotic sequences are used as spreading sequence and corresponding bit error rate (BER) in closed form is derived for imperfect channel estimation conditions. Performances of chaotic sequences are compared with pseudorandom noise (PN) sequences. Under perfect synchronization assumption, various simulation results are shown to investigate the performance of the proposed system.


      PubDate: 2015-05-27T12:42:21Z
       
  • QoS enhancement in OFDM based systems under transceiver impairments
    • Abstract: Publication date: Available online 25 April 2015
      Source:Physical Communication
      Author(s): Priyadarshi Ashok Dahat , Suvra Sekhar Das
      Broadband wireless systems generally use orthogonal frequency division multiplexing (OFDM) with link adaptation (LA) to achieve high throughput while meeting bit error rate (BER) constraint. OFDM systems are known to be affected by non-linearity of high power amplifier (HPA) at transmitter, carrier frequency offset (CFO), symbol timing offset (STO) and channel estimation error at the receiver. The delay in feedback of channel state information (CSI) further affects the performance of LA procedures. The focus of this work is on performance analysis in presence of simultaneous affect of all these impairments on LA based OFDM systems. The results are found to be useful for threshold readjustment which is essential for successful implementation of LA scheme to counter the effects of change in operating conditions from ideal to as listed above.


      PubDate: 2015-04-30T16:10:05Z
       
  • Power management in heterogeneous networks with energy harvesting base
           stations
    • Abstract: Publication date: Available online 7 April 2015
      Source:Physical Communication
      Author(s): Chang Liu , Balasubramaniam Natarajan
      In this paper, heterogeneous cellular networks (HCNs) with base stations (BSs) powered from both renewable energy sources and the grid power are considered. Based on a techno-economic analysis, we demonstrate that by controlling both transmit power and stored energy usage of BSs, energy costs can be effectively reduced. Specifically, we propose a two-stage BS operation scheme where an optimization and control subproblem is solved at each stage, respectively. For the first subproblem, transmit power of BSs is adjusted while quality of service (QoS) experienced by users is preserved. In the second subproblem, we consider the strategic scheduling of renewable energy used to power the BSs. That is, harvested energy may be reserved in the battery for future use to minimize the cost of on-grid power that varies in real-time. We propose: (1) an optimization approach built on a lattice model with a method to process outage rate constraint, and (2) a control algorithm based on nonlinear model predictive control (NMPC) theory to solve the two subproblems, respectively. Simulation results include a collection of case studies that demonstrate as to how operators may manage energy harvesting BSs to reduce their electricity costs.


      PubDate: 2015-04-09T09:33:37Z
       
  • Editorial Board
    • Abstract: Publication date: June 2015
      Source:Physical Communication, Volume 15




      PubDate: 2015-04-09T09:33:37Z
       
  • Editorial Board
    • Abstract: Publication date: March 2015
      Source:Physical Communication, Volume 14




      PubDate: 2015-03-07T23:25:26Z
       
  • 2014 Editorial for PHYCOM Journal
    • Abstract: Publication date: March 2015
      Source:Physical Communication, Volume 14
      Author(s): Ian F. Akyildiz



      PubDate: 2015-03-07T23:25:26Z
       
  • An overview of shadowed fading wireless channels in terms of a cascaded
           approach
    • 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
       
 
 
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