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PHYSICS (574 journals)            First | 1 2 3 4 5 6 | Last

Nature Communications     Open Access   (Followers: 80)
Nature Materials     Full-text available via subscription   (Followers: 54)
Nature Physics     Full-text available via subscription   (Followers: 25)
NDT & E International     Hybrid Journal   (Followers: 17)
NEUTRINO     Open Access  
Neutron News     Hybrid Journal  
New Journal of Physics     Open Access   (Followers: 6)
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: 9)
Nonlinear Dynamics     Hybrid Journal   (Followers: 5)
NTM Zeitschrift für Geschichte der Wissenschaften, Technik und Medizin     Hybrid Journal   (Followers: 4)
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: 4)
Open Journal of Microphysics     Open Access  
Open Physics     Open Access   (Followers: 2)
Optical Communications and Networking, IEEE/OSA Journal of     Hybrid Journal   (Followers: 5)
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: 12)
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: 19)
Physical Review Special Topics - Physics Education Research     Open Access   (Followers: 6)
Physical Review X     Open Access   (Followers: 7)
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: 2)
Physics and Chemistry of the Earth, Parts A/B/C     Hybrid Journal   (Followers: 3)
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: 10)
Physics in Perspective     Hybrid Journal   (Followers: 1)
Physics International     Open Access   (Followers: 2)
Physics Letters A     Hybrid Journal   (Followers: 9)
Physics Letters B     Open Access   (Followers: 3)
Physics of Fluids     Hybrid Journal   (Followers: 29)
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: 3)
Physics of Wave Phenomena     Hybrid Journal   (Followers: 1)
Physics Procedia     Partially Free   (Followers: 1)
Physics Reports     Full-text available via subscription   (Followers: 2)
Physics Research International     Open Access   (Followers: 1)
Physics Today     Hybrid Journal   (Followers: 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: 3)
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: 529)
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   (Followers: 1)
Progress of Theoretical and Experimental Physics     Open Access  
Quantum Electronics     Full-text available via subscription   (Followers: 3)
Quantum Measurements and Quantum Metrology     Open Access  
Quantum Studies : Mathematics and Foundations     Hybrid Journal   (Followers: 1)
Quarterly Journal of Mechanics and Applied Mathematics     Hybrid Journal   (Followers: 3)
Radiation Effects and Defects in Solids     Hybrid Journal   (Followers: 1)
Radiation Measurements     Hybrid Journal   (Followers: 2)
Radiation Physics and Chemistry     Hybrid Journal   (Followers: 1)
Radiation Protection Dosimetry     Hybrid Journal   (Followers: 2)
Radiation Research     Full-text available via subscription   (Followers: 3)
Radio Science     Full-text available via subscription   (Followers: 3)
Radiological Physics and Technology     Hybrid Journal   (Followers: 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: 17)
Revista Boliviana de Física     Open Access  

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

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

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

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

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

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

      PubDate: 2015-01-09T02:01:05Z
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