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PHYSICS (581 journals)

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Journal Cover Physical Communication
  [SJR: 0.552]   [H-I: 19]   [1 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1874-4907
   Published by Elsevier Homepage  [3040 journals]
  • Finite-SNR outage analysis for MIMO channels with imperfect channel state
    • Authors: Nandita Lavanis; Devendra Jalihal; Arun Pachai Kannu; Srikrishna Bhashyam
      Abstract: Publication date: Available online 10 January 2017
      Source:Physical Communication
      Author(s): Nandita Lavanis, Devendra Jalihal, Arun Pachai Kannu, Srikrishna Bhashyam
      In this paper, a point-to-point multiple-input multiple-output (MIMO) channel with imperfect channel state information (CSI) at the receiver and no CSI at the transmitter is considered. Using Monte Carlo simulations, we compute the optimum number of active antennas required at the transmitter ( t opt ) to minimize the outage probability. We show that, apart from the number of transmit antennas, t opt depends on the signal to noise ratio (SNR), multiplexing gain, coherence time, and the number of receive antennas. Our results give insights on the behavior of t opt with respect to these parameters. Specifically, we show that as the multiplexing gain increases, the value of t opt increases from one, and as the multiplexing gain reaches its maxima, the value of t opt equals the minimum of the number of transmit and receive antennas. The intermediate behavior of t opt with respect to multiplexing gain depends on the MIMO channel configuration. t opt for the MIMO channel with perfect CSI at the receiver follows a similar pattern as that with imperfect CSIR. For a multiple-input single-output (MISO) channel with imperfect CSIR, we obtain a tight upper bound on the outage probability. Using this analytical upper bound, we can calculate t opt for any fixed channel configuration. For a MISO channel with imperfect CSIR and fixed SNR, t opt reduces as multiplexing gain increases; however, for fixed multiplexing gain and fixed SNR, t opt monotonically increases with increase in coherence time of the channel.

      PubDate: 2017-01-15T14:25:05Z
      DOI: 10.1016/j.phycom.2016.12.005
  • On the design of a multi-carrier correlation delay-shift keying system
    • Authors: Nguyen Xuan Quyen
      Abstract: Publication date: Available online 15 January 2017
      Source:Physical Communication
      Author(s): Nguyen Xuan Quyen
      This paper presents the design of a multi-carrier correlation delay-shift keying (MC-CDSK) system for the operation in wireless environments. In the proposed system, the sum of a chaotic sequence and it delayed version is considered to be a reference sequence and transmitted through a predefined subcarrier. The input data is divided into multiple pairs of bit sub-sequences, where the first and second ones of each pair are spread in the frequency domain by directly multiplying with the chaotic sequence and the delayed version, respectively. The sum of two resulting signals for each pair is then transmitted on a corresponding subcarrier. In the receiving side, the reference sequence retrieved from the predefined subcarrier and the signal retrieved from each of the remaining subcarriers are correlated with the delayed version of the other ones to recover the corresponding bit sub-sequence pair. The recovered pairs are combined to an output data. Schemes for the transmitter and receiver are designed and their operation over a multipath Rayleigh fading channel is described. The system performance is evaluated via theoretical analysis and then verified by numerical simulation. Our findings show that MC-CDSK system can improve communication features, i.e., bit error rate (BER) performance, energy and spectrum efficiency compared to those of the conventional CDSK.

      PubDate: 2017-01-15T14:25:05Z
      DOI: 10.1016/j.phycom.2016.12.004
  • Distributed power allocation for spectrum sharing in mutually interfering
           wireless systems
    • Authors: Saygın Bakşi; Dimitrie C. Popescu
      Abstract: Publication date: Available online 5 January 2017
      Source:Physical Communication
      Author(s): Saygın Bakşi, Dimitrie C. Popescu
      Allocation of transmit power is critical for spectrum sharing and coexistence of mutually interfering wireless systems. In this paper we present a novel approach for allocation of transmit power, which is based on a non-greedy procedure that aims at maximizing transmission rate while also controlling interference levels. The proposed approach is fully distributed and requires no central control or coordination. Numerical results obtained from simulations are presented to illustrate the performance of the proposed approach in both sparse and dense environments. In sparse wireless environments, where there are fewer mutually interfering wireless links than available frequency bands, the proposed approach yields power allocations which outperform those obtained by applying alternative power allocation strategies, while in dense environments, where there are more interfering links than available frequency bands, the proposed approach yields power allocations with performance similar to those of existing power strategies. Thus, the distributed power allocation procedure based on the proposed approach is a drop-in replacement algorithm that yields better system throughput than existing algorithms for spectrum sharing.

      PubDate: 2017-01-07T12:21:07Z
      DOI: 10.1016/j.phycom.2016.12.003
  • A fractional path-loss compensation based power control technique for
           interference mitigation in LTE-A femtocell networks
    • Authors: Sawsan Ali Saad; Mahamod Ismail; Rosdiadee Nordin; Afaz Uddin Ahmed
      Pages: 1 - 9
      Abstract: Publication date: Available online 15 March 2016
      Source:Physical Communication
      Author(s): Sawsan Ali Saad, Mahamod Ismail, Rosdiadee Nordin, Afaz Uddin Ahmed
      Introduction of Femtocells in heterogeneous network enhances the capacity, indoor coverage of the existing macrocell based network. It also allows high-speed data services for the multi-media application and software. However, in dense co-channel deployment scenarios femtocells cause severe interference to the neighbouring cells users. In this paper, a downlink-power-control scheme is presented for femtocell with no overhead signalling exchange with the macrocell. The femtocell adjusts the transmit power subject to home user equipment (HUE) measurements. The minimum level of transmit power is determined by the target Signal to Interference and Noise Ratio (SINR) of femtocell user that is set according to the required Quality of Service (QoS) of the femtocell users. The system level simulations confirm that, the proposed scheme reduces the outage probability of the nearby macrocell user equipment (MUE) up to 16.7% compared to fixed power setting, while maintaining the spectral efficiency of femtocell users. Furthermore, the transmit power can be reduced by 52.6% which leads to power effective solution of the interference scenario.

      PubDate: 2016-03-18T13:41:49Z
      DOI: 10.1016/j.phycom.2016.02.003
      Issue No: Vol. 21 (2016)
  • Automatic modulation classification based on high order cumulants and
           hierarchical polynomial classifiers
    • Authors: Ameen Abdelmutalab; Khaled Assaleh; Mohamed El-Tarhuni
      Pages: 10 - 18
      Abstract: Publication date: December 2016
      Source:Physical Communication, Volume 21
      Author(s): Ameen Abdelmutalab, Khaled Assaleh, Mohamed El-Tarhuni
      In this paper, a Hierarchical Polynomial (HP) classifier is proposed to automatically classify M-PSK and M-QAM signals in Additive White Gaussian Noise (AWGN) and slow flat fading environments. The system uses higher order cumulants (HOCs) of the received signal to distinguish between the different modulation types. The proposed system divides the overall modulation classification problem into several hierarchical binary sub-classifications. In each binary sub-classification, the HOCs are expanded into a higher dimensional space in which the two classes are linearly separable. It is shown that there is a significant improvement when using the proposed Hierarchical polynomial structure compared to the conventional polynomial classifier. Moreover, simulation results are shown for different block lengths (number of received symbols) and at different SNR values. The proposed system showed an overall improvement in the probability of correct classification that reaches 100% using only 512 received symbols at 20 dB compared to 98% and 98.33% when using more complicated systems like Genetic Programming with KNN classifier (GP-KNN) and Support Vector Machines (SVM) classifiers, respectively.

      PubDate: 2016-10-16T08:58:51Z
      DOI: 10.1016/j.phycom.2016.08.001
      Issue No: Vol. 21 (2016)
  • Power allocation in multi-hop OFDM transmission systems with
           amplify-and-forward relaying: A unified approach
    • Authors: Amin Azari; Jalil S. Harsini; Farshad Lahouti
      Pages: 19 - 29
      Abstract: Publication date: December 2016
      Source:Physical Communication, Volume 21
      Author(s): Amin Azari, Jalil S. Harsini, Farshad Lahouti
      In this paper, a unified approach for power allocation (PA) in multi-hop orthogonal frequency division multiplexing (OFDM) amplify-and-forward (AF) relaying systems is presented. In the proposed approach, we consider short and long term individual and total power constraints at the source and relays, and devise low complexity PA algorithms when wireless links are subject to channel path-loss and small-scale Rayleigh fading. To manage the complexity, in the proposed formulations, we adopt a two-stage iterative approach consisting of a power distribution phase among distinct subcarriers, and a power allocation phase among different relays. In particular, aiming at improving the instantaneous rate of multi-hop transmission systems with AF relaying, we develop (i) a near-optimal iterative PA algorithm based on the exact analysis of the received SNR at the destination; (ii) a low complexity suboptimal iterative PA algorithm based on an approximate expression of the received SNR at high-SNR regime; and (iii) a low complexity non-iterative PA scheme with limited performance loss. Simulation results show the superior performance of the proposed power allocation algorithms.

      PubDate: 2016-10-16T08:58:51Z
      DOI: 10.1016/j.phycom.2016.07.002
      Issue No: Vol. 21 (2016)
  • A very tight approximate results of MRC receivers over independent Weibull
           fading channels
    • Authors: Abdelmajid Bessate; Faissal El Bouanani
      Pages: 30 - 40
      Abstract: Publication date: December 2016
      Source:Physical Communication, Volume 21
      Author(s): Abdelmajid Bessate, Faissal El Bouanani
      In this paper, we study the performance of L -branch maximal-ratio combining (MRC) receivers operating over independent Weibull-fading channels. Our main result is a very tight approximation of the probability density function (PDF) of the signal-to-noise ratio (SNR) at the output of the combiner. Based on this result, accurate approximation of significant performance criteria, such as outage probability and average symbol error rate (ASER) are derived. We also evaluate the average bit error rate (ABER) for several coherent and non-coherent modulation schemes, using a closed-form expression for the moment-generating function (MGF) of the output SNR for MRC receivers. In addition, we derive some analytical expressions for channel capacity under various adaptation policies such as optimal rate adaptation (ORA), Optimal simultaneous power and rate adaptation (OPRA), Channel inversion with fixed rate (CIFR), and Truncated channel inversion with fixed rate (TCIFR). The proposed mathematical analysis is complemented by numerous numerical results, which point out the effects of fading severity on the overall system performance. Computer simulations are also performed to verify the validity and the accuracy of the proposed theoretical approach.

      PubDate: 2016-10-16T08:58:51Z
      DOI: 10.1016/j.phycom.2016.09.001
      Issue No: Vol. 21 (2016)
  • Editorial: Receiving the baton
    • Authors: Tolga M. Duman
      Abstract: Publication date: September 2016
      Source:Physical Communication, Volume 20
      Author(s): Tolga M. Duman

      PubDate: 2016-10-16T08:58:51Z
      DOI: 10.1016/s1874-4907(16)30080-5
      Issue No: Vol. 20 (2016)
  • Editorial: Passing the baton
    • Authors: Ian F. Akyildiz
      Abstract: Publication date: September 2016
      Source:Physical Communication, Volume 20
      Author(s): Ian F. Akyildiz

      PubDate: 2016-10-16T08:58:51Z
      DOI: 10.1016/s1874-4907(16)30079-9
      Issue No: Vol. 20 (2016)
  • On-demand multimedia data broadcast in MIMO wireless networks
    • Authors: Ping He; Hong Shen
      Pages: 1 - 16
      Abstract: Publication date: Available online 2 May 2016
      Source:Physical Communication
      Author(s): Ping He, Hong Shen
      Given a set of multiple requests from clients equipped with M antennae and a wireless network of m channels, on-demand data broadcast requires to find an optimal schedule of broadcasting (placing) all requested data items of R on a set of channels C as evenly as possible under the constraint that each client may use at most M channels. Such a schedule is important for overcoming the shortcomings of wireless networks such as asymmetric bandwidth between uplink and downlink, and limited battery life of mobile devices. Existing schemes for data broadcast assume single-antenna clients and will result in significant bandwidth wastage and client’s data download time increase. To overcome these problems, we propose a novel approach for disseminating multimedia data in an MIMO wireless network by converting it to the multiprocessor scheduling problem where requests and antennae are regarded as tasks and processors respectively. We present three schemes (LFOS, BFOS and BBOS) under this approach: LFOS scheduling data items of largest sizes, BFOS adopting the best matching between data items and channels, and BBOS partitioning data items properly to balance the broadcast cycles of all channels. In comparison with the existing schemes based on single-antenna broadcast, our schemes improve access latency and channel bandwidth usage significantly. This has been verified through extensive experimental results.

      PubDate: 2016-05-03T02:43:56Z
      DOI: 10.1016/j.phycom.2016.04.003
      Issue No: Vol. 20 (2016)
  • Performance evaluation of FRESH filter based spectrum sensing for
           cyclostationary signals
    • Authors: Ribhu Chopra; Debashis Ghosh; D.K. Mehra
      Pages: 17 - 32
      Abstract: Publication date: Available online 9 May 2016
      Source:Physical Communication
      Author(s): Ribhu Chopra, Debashis Ghosh, D.K. Mehra
      This paper considers the problem of spectrum sensing of cyclostationary signals for cognitive radios. It has been reported earlier using simulation results that FRESH filtering a signal, prior to spectrum sensing, may result in gains of more than 5 dB over the standard energy and cyclostationary detectors. This paper develops a quasi-analytical theory of spectrum sensing based on FRESH filtering. It is shown that significant performance gains are achievable in both energy detection and cyclostationarity detection via FRESH filtering of the received signal prior to the detection step. The aforementioned approach may be shown to reduce the number of samples required to achieve a given detection performance by more than 90% in practice, thereby reducing the sensing time in a cognitive radio system. It is also shown that the FRESH filtering before energy detection may reduce the effects of SNR walls caused due to noise uncertainty. The validity of all the derived observations is verified via simulations.

      PubDate: 2016-05-14T08:11:11Z
      DOI: 10.1016/j.phycom.2016.04.004
      Issue No: Vol. 20 (2016)
  • Radar interference into LTE base stations in the 3.5 GHz band
    • Authors: Mo Ghorbanzadeh; Eugene Visotsky; Prakash Moorut; Charles Clancy
      Pages: 33 - 47
      Abstract: Publication date: Available online 11 May 2016
      Source:Physical Communication
      Author(s): Mo Ghorbanzadeh, Eugene Visotsky, Prakash Moorut, Charles Clancy
      We study the interference from a rotating shipborne radar system that spectrally and spatially coexists with a Long Term Evolution (LTE) cellular communications network in the 3.5 GHz band to investigate the feasibility of LTE deployment in the United States coastal metropolitan cities in that band. First, we simulate the radar systems with realistic operational parameters. Furthermore, we leverage a detailed 3GPP-compliant LTE simulation with a sophisticated air interface modeling and investigate sensitivity of LTE to radar interference in macro cell, outdoor small cell, and indoor small cell scenarios. We simulate the propagation conditions between the radar and LTE system by adopting the Free Space Path Loss and Irregular Terrain Model commonly leveraged by National Telecommunications and Information Administration (NTIA), to account for propagation, diffraction, and troposcatter losses that the radar pulses undergo before they reach the LTE system. As a performance metric, we evaluate the throughput of the LTE system in the uplink direction for various distances between the radar and the cellular system. Our simulation results indicate an LTE link will remain operational even in severe interference conditions. In fact, the LTE system as close as 100 km away from the radar undergoes less than 10 % throughput loss from the LTE total throughput, and the throughput loss is less than 30 % when the radar is only 50 km away from the LTE.

      PubDate: 2016-05-14T08:11:11Z
      DOI: 10.1016/j.phycom.2016.04.005
      Issue No: Vol. 20 (2016)
  • A survey on compressive sensing techniques for cognitive radio networks
    • Authors: Fatima Salahdine; Naima Kaabouch; Hassan El Ghazi
      Pages: 61 - 73
      Abstract: Publication date: Available online 31 May 2016
      Source:Physical Communication
      Author(s): Fatima Salahdine, Naima Kaabouch, Hassan El Ghazi
      In cognitive radio, one of the main challenges is wideband spectrum sensing. Existing spectrum sensing techniques are based on a set of observations sampled by an analog/digital converter (ADC) at the Nyquist rate. However, those techniques can sense only one band at a time because of the hardware limitations on sampling rate. In addition, in order to sense a wideband spectrum, the band is divided into narrow bands or multiple frequency bands. Secondary users (SU) have to sense each band using multiple RF frontends simultaneously, which results in a very high processing time, hardware cost, and computational complexity. In order to overcome this problem, the signal sampling should be as fast as possible, even with high dimensional signals. Compressive sensing has been proposed as one of the solutions to reduce the processing time and accelerate the scanning process. It allows reducing the number of samples required for high dimensional signal acquisition while keeping the important information. Over the last decade, a number of papers related to compressive sensing techniques have been published. However, most of these papers describe techniques corresponding to one process either sparse representation, sensing matrix, or recovery. This paper provides an in depth survey on compressive sensing techniques and classifies these techniques according to which process they target, namely, sparse representation, sensing matrix, or recovery algorithms. It also discusses examples of potential applications of these techniques including in spectrum sensing, channel estimation, and multiple-input multiple-output (MIMO) based cognitive radio. Metrics to evaluate the efficiencies of existing compressive sensing techniques are provided as well as the benefits and challenges in the context of cognitive radio networks.

      PubDate: 2016-06-16T18:20:32Z
      DOI: 10.1016/j.phycom.2016.05.002
      Issue No: Vol. 20 (2016)
  • Utility-based resource allocation for interference limited OFDMA
           cooperative relay networks
    • Authors: Nidhal Odeh; Mehran Abolhasan; Farzad Safaei; Daniel R. Franklin; Guoqiang Mao
      Pages: 74 - 84
      Abstract: Publication date: Available online 25 May 2016
      Source:Physical Communication
      Author(s): Nidhal Odeh, Mehran Abolhasan, Farzad Safaei, Daniel R. Franklin, Guoqiang Mao
      This paper proposes a utility-based resource allocation algorithm for the uplink OFDMA Inter-cell Interference (ICI) limited cooperative relay network. Full channel state information (CSI) is assumed to be available at the resource controller at initial stage, then the work is extended to consider more realistic assumption, i.e., only partial channel state information (PCSI) is available. The proposed algorithm aims to maximize the total system utility while simultaneously satisfying the individual user’s minimum data rate requirements. In the proposed algorithm, relay selection is initially performed based on the consideration of ICI. Then, subcarrier allocation is performed to achieve maximum utility assuming equal power allocation. Finally, based on the amount of ICI, a modified water-filling power distribution algorithm is proposed and used to optimize the per-carrier power allocation across the allocated set of subcarriers. The results show that, compared to conventional algorithms, the proposed algorithm significantly improves system performance in terms of total sum data rate, outage probability and fairness.

      PubDate: 2016-06-16T18:20:32Z
      DOI: 10.1016/j.phycom.2016.05.001
      Issue No: Vol. 20 (2016)
  • Error rate analysis of AF-relay wireless networks under different SNR
    • Authors: Muhammad I. Khalil; Stevan M. Berber; Kevin W. Sowerby
      Pages: 85 - 92
      Abstract: Publication date: September 2016
      Source:Physical Communication, Volume 20
      Author(s): Muhammad I. Khalil, Stevan M. Berber, Kevin W. Sowerby
      This paper presents a new method for analyzing the Bit Error Rate (BER) performance of two-hop Amplify-and-Forward Multiple Relay (AF-MR) networks. This paper considers, a flat-fading channel and a relay selection scheme to select a relay with the highest Signal-to-Noise Ratio (SNR). The method aims to unify the BER calculation under low, high and optimal SNR levels. Asymptotic BER (ABER) performance at high SNR value is calculated first, and standard expressions for exact BER (EBER) performance at low and optimal SNRs are then derived. The analytic method depends on the conventional BER (CBER) approach of one-hop communication systems. The optimal SNR is obtained by balancing energy efficiency and spectral efficiency. The proposed method is found to be effective for calculating the BER of AF-MR network performance under any SNR conditions. Moreover, it improves the accuracy of ABER performance by reducing disparity computation errors between ABER and EBER performances and this allows the BER of AF-MR networks to be accurately calculated using either ABER or EBER. The outcome expressions for the method are validated by simulation results.

      PubDate: 2016-10-16T08:58:51Z
      DOI: 10.1016/j.phycom.2016.06.002
      Issue No: Vol. 20 (2016)
  • Recent trends in multiuser detection techniques for SDMA–OFDM
           communication system
    • Authors: Kala Praveen Bagadi; Visalakshi Annepu; Susmita Das
      Pages: 93 - 108
      Abstract: Publication date: September 2016
      Source:Physical Communication, Volume 20
      Author(s): Kala Praveen Bagadi, Visalakshi Annepu, Susmita Das
      The space division multiple access–orthogonal frequency division multiplexing (SDMA–OFDM) technique is emerged as a most competitive technology for future wireless communication system as it can provide high spectral efficiency and resistance from inter symbol interference (ISI). The SDMA like multiple access techniques are prone to multiple access interference (MAI) because multiple users transmit their data simultaneously. Such a receiver requires appropriate multiuser detection (MUD) scheme to detect individual user’s signals correctly by mitigating MAI. Further, due to non-linear behaviour of wireless channel, the signals at SDMA receiver often become linearly non-separable. As a result, MUD becomes a challenging multidimensional optimization problem. Considering these challenges, this paper reviews various MUD techniques for SDMA–OFDM system.

      PubDate: 2016-10-16T08:58:51Z
      DOI: 10.1016/j.phycom.2016.07.001
      Issue No: Vol. 20 (2016)
  • Cooperative spectrum sharing MIMO systems with successive decoding
    • Authors: Nikolaos I. Miridakis; Dimitrios D. Vergados; Angelos Michalas
      Pages: 109 - 122
      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
      DOI: 10.1016/j.phycom.2016.01.002
      Issue No: Vol. 20 (2016)
  • On error rate performance of multi-cell massive MIMO systems with linear
    • Authors: Haiquan Wang; Meijun Zhou; Ruiming Chen; Wei Zhang
      Pages: 123 - 132
      Abstract: Publication date: September 2016
      Source:Physical Communication, Volume 20
      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: 2016-10-16T08:58:51Z
      DOI: 10.1016/j.phycom.2015.10.002
      Issue No: Vol. 20 (2016)
  • On achievable rate of massive MIMO multiple access channels via virtual
    • Authors: Yun Xue; Jun Zhang; Shi Jin; Xiqi Gao
      Pages: 133 - 140
      Abstract: Publication date: September 2016
      Source:Physical Communication, Volume 20
      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: 2016-10-16T08:58:51Z
      DOI: 10.1016/j.phycom.2015.10.001
      Issue No: Vol. 20 (2016)
  • Unleashing the secure potential of the wireless physical layer: Secret key
           generation methods
    • Authors: Ahmed Badawy; Tarek Elfouly; Tamer Khattab; Amr Mohamed; Mohsen Guizani
      Pages: 1 - 10
      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
      DOI: 10.1016/j.phycom.2015.11.005
      Issue No: Vol. 19 (2016)
  • Performance evaluation of chaotic spreading sequences in a multi-user
           MIMO-OFDM system
    • Authors: Asma Ahmadinejad; Siamak Talebi
      Pages: 11 - 17
      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
      DOI: 10.1016/j.phycom.2016.01.003
      Issue No: Vol. 19 (2016)
  • From conceptual to operational: Over-the-air-programming of land mobile
    • Authors: Jeremy Carter; Eric Grommon; Phil Harris
      Pages: 18 - 29
      Abstract: Publication date: Available online 24 February 2016
      Source:Physical Communication
      Author(s): Jeremy Carter, Eric Grommon, Phil Harris
      Programming, management, and interoperability of land mobile radios within the public safety sector has long been a salient issue for policymakers, practitioners, service vendors, and scholars. Despite receiving substantial attention in the form of government expenditure and agency task forces, there has only been moderate advancement in this concerning area. Recently, as part of a U.S. Department of Justice-funded effort, an innovative technology known as wireless broadband over-the-air-programming (OTAP) has been translated from a conceptual model to an operational deployment. OTAP technology holds significant promise to enhance the management of public safety communications via land mobile radios. This research presents the concept of OTAP, the engineering behind the recently developed broadband enabled OTAP prototype, and conceptualizes how this technology can impact the processes used to facilitate public safety interoperability within the context of portable radio programming.

      PubDate: 2016-02-26T17:49:59Z
      DOI: 10.1016/j.phycom.2016.01.007
      Issue No: Vol. 19 (2016)
  • Inherent diversity combining techniques to mitigate frequency selective
           fading in chaos-based DSSS systems
    • Authors: Stevan M. Berber; Ankur K. Gandhi
      Pages: 30 - 37
      Abstract: Publication date: Available online 3 March 2016
      Source:Physical Communication
      Author(s): Stevan M. Berber, Ankur K. Gandhi
      Analysis of communication systems with combiners, assuming flat fading channels, is well-known. However, this analysis for a chaos-based DSSS system with a frequency selective channel, giving proper mathematical model and derived expressions for the probability of error, practically does not exist. This paper presents the theoretical model of a chaos-based DSSS system assuming frequency selective channel that is composed of a primary channel and a number of secondary channels. In order to investigate the consequences of delays on signal transmission in these channels, this paper uses presentation of signals in discrete time domain and theoretical frame of discrete time stochastic processes. The channel is represented by a modified Saleh-Valenzuela model, which results in a number of delayed signal replicas at the receiver side. For the sake of explanation, the delays are assumed to remain in a chip interval. For the sake of comparison, the theoretical models and derived expressions are confirmed by the simulation of the system.

      PubDate: 2016-03-08T11:01:57Z
      DOI: 10.1016/j.phycom.2016.02.001
      Issue No: Vol. 19 (2016)
  • Time reversal acoustic communication receivers: DSP implementation and
           fast channel estimation
    • Authors: Sergio Matiz Romero; Mohsen Badiey; Aijun Song
      Pages: 38 - 46
      Abstract: Publication date: Available online 15 March 2016
      Source:Physical Communication
      Author(s): Sergio Matiz Romero, Mohsen Badiey, Aijun Song
      A communication system is implemented on digital signal processors (DSPs) for the underwater acoustic environment. The implemented receiver uses time reversal multi-channel combining followed by a single-channel decision feedback equalizer. Periodic channel estimation is employed to track the channel fluctuations. These techniques are used to mitigate time-varying inter-symbol interference, which is the main challenge in the underwater acoustic channel at operating frequencies greater than 10 kHz. Various optimization tasks are performed to reduce the receiver computational complexity. A fast implementation of the matching pursuit algorithm is tested on the DSP platform. Its performance, in terms of accuracy and run-time, is compared with that of the basic matching pursuit algorithm. Experimental results of the transmission and demodulation of binary phase-shift keying signals at three different symbol rates were obtained in the local Delaware Bay. The low bit error rates demonstrate the effectiveness of our implementation.

      PubDate: 2016-03-18T13:41:49Z
      DOI: 10.1016/j.phycom.2016.02.002
      Issue No: Vol. 19 (2016)
  • ECM and SAGE based joint estimation of timing and frequency offset for
           DMIMO-OFDM system
    • Authors: Sucharita Chakraborty; Debarati Sen
      Pages: 47 - 60
      Abstract: Publication date: Available online 8 April 2016
      Source:Physical Communication
      Author(s): Sucharita Chakraborty, Debarati Sen
      Distributed multiple-input multiple-output (DMIMO) technology is a key enabler of coverage extension and enhancement of link reliability in wireless networks through distributed spatial diversity. DMIMO employs classic relay channels in between the source and the destination to opportunistically form a virtual antenna array (VAA) for emulating cooperative diversity. Use of multiple antennas at the relays further increases capacity and reliability of the relay-destination channel through multiplexing and diversity of MIMO antennas respectively. In such network, the signal received at the destination is characterized by multiple timing offsets (MTO) due to different propagation delay and multiple carrier frequency offsets (MCFO) due to independent oscillators of the relays. Hence, synchronization becomes a crucial issue in DMIMO in order to realize the distributed coherence. In this paper, we address joint estimation of MCFO and MTO in DMIMO orthogonal frequency division multiplexing (OFDM) with MIMO configuration at the relays for estimate-and-forward (EF) relaying protocol. Two iterative algorithms, based on expectation conditional maximization (ECM) and space alternating generalized expectation-maximization (SAGE) are proposed for joint estimation in presence of inter carrier interference (ICI). The robustness of both the estimators to ICI is evaluated by mathematical analysis and supported by extensive simulations. The performance of the proposed estimators are assessed in terms of mean square error (MSE) and bit error rate (BER). The theoretical Cramer-Rao lower bound (CRLB) of estimator error variance is also derived.

      PubDate: 2016-04-08T18:19:31Z
      DOI: 10.1016/j.phycom.2016.03.003
      Issue No: Vol. 19 (2016)
  • Full-duplex communication for future wireless networks: Dynamic resource
           block allocation approach
    • Authors: Chandan Pradhan; Garimella Rama Murthy
      Pages: 61 - 69
      Abstract: Publication date: Available online 13 April 2016
      Source:Physical Communication
      Author(s): Chandan Pradhan, Garimella Rama Murthy
      In this paper, we discuss a full-duplex (FD) communication scenario, where multiple FD user equipments (UEs) share same spectrum resources (or resource blocks) simultaneously. The FD eNodeB deploys digital precoding and successive interference cancellation with optimal ordering algorithm, to allow coexistence of multiple UEs in downlink and uplink, respectively. The sharing of same resource blocks, results in co-channel interference (CCI), in downlink of a UE, from uplink signals of other UEs. To mitigate the interference, a smart antenna approach is adopted. The approach includes using multiple antennas at UEs to form directed beams towards eNodeB and nulls towards other UEs. However, the approach fails when the UEs due to their mobility align themselves in the same direction with respect to the eNodeB (eNB). In this paper, we propose a dynamic resource block allocation (DRBA) algorithm for avoiding CCI due to mobility of UEs, sharing the spectrum resource, in a FD communication scenario. The proposed algorithm shows significant improvement of the quality of service (QoS) of the communication links.

      PubDate: 2016-04-17T22:34:31Z
      DOI: 10.1016/j.phycom.2016.03.002
      Issue No: Vol. 19 (2016)
  • Models, statistics, and rates of binary correlated sources
    • Authors: Marco Martalò; Riccardo Raheli
      Pages: 70 - 80
      Abstract: Publication date: Available online 19 April 2016
      Source:Physical Communication
      Author(s): Marco Martalò, Riccardo Raheli
      This paper discusses and analyzes various models of binary correlated sources, which may be relevant in several distributed communication scenarios. These models are statistically characterized in terms of joint Probability Mass Function (PMF) and covariance. Closed-form expressions for the joint entropy of the sources are also overviewed. The asymptotic entropy rate for very large number of sources is shown to converge to a common limit for all the considered models. This fact generalizes recent results on the information-theoretic performance limit of communication schemes which exploit the correlation among sources at the receiver.

      PubDate: 2016-04-21T23:28:35Z
      DOI: 10.1016/j.phycom.2016.04.002
      Issue No: Vol. 19 (2016)
  • Guest Editorial for the special issue on Self-optimizing Cognitive Radio
    • Authors: Muhammad R.A. Khandaker; Kai-Kit Wong; Haitao Zhao; Shamik Sengupta
      Pages: 81 - 83
      Abstract: Publication date: Available online 22 March 2016
      Source:Physical Communication
      Author(s): Muhammad R.A. Khandaker, Kai-Kit Wong, Haitao Zhao, Shamik Sengupta

      PubDate: 2016-03-23T14:07:14Z
      DOI: 10.1016/j.phycom.2016.03.001
      Issue No: Vol. 19 (2016)
  • Cooperative spectrum sensing protocols and evaluation with IEEE 802.15.4
    • Authors: Tahir Akram; Tim Esemann; Horst Hellbrück
      Pages: 93 - 105
      Abstract: Publication date: Available online 10 February 2016
      Source:Physical Communication
      Author(s): Tahir Akram, Tim Esemann, Horst Hellbrück
      Spectrum Sensing is one of the important tasks for wireless devices. By sensing the spectrum, wireless devices sense their radio environment and perform spectrum access accordingly to reduce collisions. Due to radio propagation effects and inherent noise in the measurements, performance of todays wireless technologies with individual spectrum sensing cannot solve the hidden node problem. Cooperative sensing is seen as a way to improve the performance of wireless devices improving the radio bandwidth utilization and minimizing interference among wireless devices. To the best of our knowledge, this is the first work which provides protocols for cooperative sensing and presents experimental results with IEEE 802.15.4 devices. We present and implement protocols and applications for primary, secondary and cooperative users with a dedicated control channel. Thereby, the secondary user receiver serves as a first cooperative node in the system which reduces collisions between primary and secondary users. We evaluate the system performance with receiver sensing and additional cooperative nodes. We also propose a mechanism to extend the protocol for multiple secondary users sharing the same control channel. Based on the evaluations, we also provide recommendations for usage of cooperative sensing with focus on IEEE 802.15.4.

      PubDate: 2016-02-15T14:14:26Z
      DOI: 10.1016/j.phycom.2016.01.001
      Issue No: Vol. 19 (2016)
  • Special issue on D2D-based offloading techniques
    • Authors: Vincenzo Mancuso; Omer Gurewitz
      Pages: 133 - 134
      Abstract: Publication date: Available online 8 April 2016
      Source:Physical Communication
      Author(s): Vincenzo Mancuso, Omer Gurewitz

      PubDate: 2016-04-08T18:19:31Z
      DOI: 10.1016/j.phycom.2016.04.001
      Issue No: Vol. 19 (2016)
  • Joint optimization of component carrier selection and resource allocation
           in 5G carrier aggregation system
    • Authors: Weidong Gao; Lin Ma; Gang Chuai
      Abstract: Publication date: Available online 24 December 2016
      Source:Physical Communication
      Author(s): Weidong Gao, Lin Ma, Gang Chuai
      In this paper, we consider joint optimization of Component Carrier (CC) selection and resource allocation in 5G Carrier Aggregation (CA) system. Firstly, the upper-bound system throughput with determined number of CCs is derived and it is proved by using graph theory that the throughput optimization problem is NP hard. Then we propose a greedy based algorithm to solve this problem and prove that the proposed algorithm can achieve at least 1/2 of the optimal performance in the worst case. At last, we evaluate the throughput and computational complexity performance through a variety of simulations. Simulation results show that the proposed algorithm can obtain better performance comparing with existing schemes while keeping the computation complexity at an acceptable level.

      PubDate: 2016-12-27T11:17:52Z
      DOI: 10.1016/j.phycom.2016.12.002
  • Cognitive radio network with secrecy and interference constraints
    • Authors: Hung Tran; Georges Kaddoum; François Gagnon; Louis Sibomana
      Abstract: Publication date: Available online 14 December 2016
      Source:Physical Communication
      Author(s): Hung Tran, Georges Kaddoum, François Gagnon, Louis Sibomana
      In this paper, we investigate the physical-layer security of a secure communication in single-input multiple-output (SIMO) cognitive radio networks (CRNs) in the presence of two eavesdroppers. In particular, both primary user (PU) and secondary user (SU) share the same spectrum, but they face with different eavesdroppers who are equipped with multiple antennas. In order to protect the PU communication from the interference of the SU and the risks of eavesdropping, the SU must have a reasonable adaptive transmission power which is set on the basis of channel state information, interference and security constraints of the PU. Accordingly, an upper bound and lower bound for the SU transmission power are derived. Furthermore, a power allocation policy, which is calculated on the convex combination of the upper and lower bound of the SU transmission power, is proposed. On this basis, we investigate the impact of the PU transmission power and channel mean gains on the security and system performance of the SU. Closed-form expressions for the outage probability, probability of non-zero secrecy capacity, and secrecy outage probability are obtained. Interestingly, our results show that the strong channel mean gain of the PU transmitter to the PU’s eavesdropper in the primary network can enhance the SU performance.

      PubDate: 2016-12-20T06:34:32Z
      DOI: 10.1016/j.phycom.2016.12.001
  • Enabling simultaneous cooling and data transmission in the terahertz band
           for board-to-board communications
    • Authors: Vitaly Petrov; Joonas Kokkoniemi; Dmitri Moltchanov; Janne Lehtomäki; Yevgeni Koucheryavy
      Abstract: Publication date: Available online 21 November 2016
      Source:Physical Communication
      Author(s): Vitaly Petrov, Joonas Kokkoniemi, Dmitri Moltchanov, Janne Lehtomäki, Yevgeni Koucheryavy
      A system enabling simultaneous cooling and board-to-board communications is proposed and analyzed. It is shown that hollow pipes used in computer cooling systems can be applied for communications with extreme data rates at distances up to tens of centimeters. This is done by using wireless communications in the terahertz frequency band, 0.1 – 10 THz. The experiments were performed in order to observe how straight and curved pipes of different diameters and lengths affect THz signals propagating inside the pipes. The measured pulses were recorded and used in numerical evaluation of bit error rate and throughput taking into account the effect of all possible combinations of N previous symbols. The numerical results show the dependency of the intersymbol interference on the delay profile of the channel and on the symbol period. The results demonstrate that even with simple on-off keying modulation the throughput reaches few terabits per second with qualitatively low bit error rates. This enables communications between rate-hungry electronics inside computers such as central and graphical processing units while simultaneously providing the cooling functionality.

      PubDate: 2016-11-27T23:03:47Z
      DOI: 10.1016/j.phycom.2016.11.002
  • Wireless Information-Theoretic Security: Theoretical analysis &
           experimental measurements with multiple eavesdroppers in an outdoor
           obstacle-dense MANET
    • Authors: Theofilos Chrysikos; Konstantinos Birkos; Tasos Dagiuklas; Stavros Kotsopoulos
      Abstract: Publication date: Available online 22 November 2016
      Source:Physical Communication
      Author(s): Theofilos Chrysikos, Konstantinos Birkos, Tasos Dagiuklas, Stavros Kotsopoulos
      Wireless Information-Theoretic Security (WITS) has been suggested as a robust security scheme, especially for infrastructure-less networks. Based on the physical layer, WITS considers quasi-static Rayleigh fading instead of the classic Gaussian wiretap scenario. In this paper, they key parameters of WITS are investigated by implementing an 802.11n ad-hoc network in an outdoor obstacle-dense topology. Measurements performed throughout the topology allow for a realistic evaluation of a scenario with multiple moving eavesdroppers. Low speed user movement has been considered, so that Doppler spread can be discarded. A set of discrete field test trials have been conducted, based on simulation of human mobility throughout an obstacle-constrained environment. Average Signal-to-Noise Ratio (SNR) values have been measured for all moving nodes, and the Probability of Non-Zero Secrecy Capacity has been calculated for different eavesdropping cooperative schemes (Selection Combining and Maximal-Ratio Combining). In addition, the Outage Probability has been estimated with regard to a non-zero target Secrecy Rate for both techniques. The results have been compared with the respective values of WITS key parameters derived from theoretical analysis.

      PubDate: 2016-11-27T23:03:47Z
      DOI: 10.1016/j.phycom.2016.11.003
  • A Cost-effective approach for spectrum sensing using beamforming
    • Authors: Kaïs Bouallegue; Iyad Dayoub; Mohamed Gharbi; Kaïs Hassan
      Abstract: Publication date: Available online 16 November 2016
      Source:Physical Communication
      Author(s): Kaïs Bouallegue, Iyad Dayoub, Mohamed Gharbi, Kaïs Hassan
      Spectrum sensing (SS) is one of the principal challenges on which the mobile communication is based on. Identifying the available frequency bands, also called white spaces, is the main issue. A novel blind approach for SS in the narrowband context is proposed in order to improve the signal detection. Considering a channel with its angle of arrival (AoA), we use beamforming technique to exploit the maximum and minimum angular energy. Both theoretical developments of the threshold and performance analysis are developed. To validate our contribution, the analytical results of the performance developed in this paper are compared with those from simulation. A comparison of state-of-the-art SS method using the eigenvalue decomposition is provided which brings an interesting trade-off between complexity and performance. Finally, simulation results considering the probability of misdetection under very low signal-to-noise ratio (SNR) are presented.

      PubDate: 2016-11-20T21:19:30Z
      DOI: 10.1016/j.phycom.2016.11.001
  • Bit error rate analysis of the scheduled TAS with MRC for CR-MIMO systems
    • Authors: Donghun Lee
      Abstract: Publication date: Available online 11 November 2016
      Source:Physical Communication
      Author(s): Donghun Lee
      In this paper, we investigate the bit error rate (BER) analysis of the scheduled transmit antenna selection (TAS) with maximal ratio combining (MRC) for the cognitive radio multiple-input multiple-output (CR-MIMO) systems. As a first step, this paper derives approximate probability density functions (PDFs) of the effective signal to noise ratio (SNR) of the proposed scheduled TAS with MRC in CR-MIMO systems. Next, the tight closed-form expressions of the BER for the M -ary QAM and M -ary PSK modulations are presented, respectively. Using asymptotic analysis, we approximate the BER for the scheduled system, and quantify the diversity order and SNR gain, respectively. Analytical results show that the diversity order of the scheduled system is the product of spatial diversity (SD) and multiuser diversity (MUD). Thus, BER performance of the proposed system is improved as the number of users increases by MUD regardless of modulation types. Also, the SNR gain is getting worsen as the number of received antennas at the primary system increases regardless of modulation types.

      PubDate: 2016-11-13T19:54:10Z
      DOI: 10.1016/j.phycom.2016.10.002
  • OFDM symbol detection integrated with channel multipath gains estimation
           for doubly-selective fading channels
    • Authors: Wang Harry; Leib
      Abstract: Publication date: Available online 2 November 2016
      Source:Physical Communication
      Author(s): Wang Yi, Harry Leib
      Orthogonal Frequency Division Multiplexing (OFDM) is a technique for wideband transmission that is commonly used in modern wireless communication systems because of its good performance over frequency selective channels. However OFDM systems are sensitive to channel time variations resulting in Inter-Carrier Interference (ICI), that without suitable detection methods can degrade performance significantly. Channel State Information (CSI) is essential to various OFDM detection schemes, and its acquisition is a critical factor over time varying channels. This work considers a Kalman filter channel multipath gains estimation technique for time varying environments, integrated with a novel detection scheme for OFDM based on a Sphere Decoding (SD) algorithm derived to exploit the banded structure of the channel matrix. This combined scheme employs decision-feedback from the SD requiring only a low pilot symbol density, and hence improves bandwidth efficiency. Three techniques for integrating the Kalman filter operating in decision-feedback mode, with SD data detection that produces these decisions, are considered in this paper. When compared with other competing schemes, this integrated symbol detection and channel multipath gains estimation approach for OFDM provides performance advantages over time varying channels. Furthermore, it is shown that for moderate Doppler shifts the degradation that carrier phase noise induces in this scheme is small.

      PubDate: 2016-11-06T17:53:32Z
  • Adaptive threshold spectrum sensing based on expectation maximization
    • Authors: Daniel Malafaia; Vieira Ana
      Abstract: Publication date: Available online 3 November 2016
      Source:Physical Communication
      Author(s): Daniel Malafaia, José Vieira, Ana Tomé
      In this article we address a novel method for spectrum sensing, based on the Expectation Maximization algorithm applied to the histogram of the moving average signal power. The method enables the estimation of the number of active users in a given frequency band, the power received from each user, the occupied time slots and the front-end noise floor. The proposed approach takes advantage of the statistical properties of the averaging estimator output, which allows to model the received estimated power as a Gaussian mixture. This model represents the distributions of the users transmitted signal power as well as the system noise floor. Moreover, the Gaussian with the lowest mean that is related with the noise floor, can be used to estimate an adaptive threshold for a constant false alarm rate detector. Finally, the method was validated in a Wi-Fi experimental setup, where real-world data was acquired with a software defined radio.

      PubDate: 2016-11-06T17:53:32Z
  • Spectrum-sharing DF generalized order relay selection with interference
           and multiple primary users using orthogonal spectrums
    • Authors: Anas M. Salhab; Salam A. Zummo
      Abstract: Publication date: Available online 27 October 2016
      Source:Physical Communication
      Author(s): Anas M. Salhab, Salam A. Zummo
      In this paper, we propose and evaluate the performance of cognitive decode-and-forward (DF) generalized order relay selection network where the primary user (PU) receivers utilize orthogonal spectrums in the presence of interference. We consider a new scenario where the primary receivers utilize orthogonal spectrum bands and the spectrum of the primary receiver whose channel enhances the performance of the secondary system is shared with the secondary user (SU) nodes. Using orthogonal spectrum bands in cellular networks aims to reduce the interference between users as in the downlink transmission where orthogonal frequency bands are used by the base station (BS) in transmitting the data for the different users. The generalized order relay selection scheme is efficient in situations where the opportunistic relaying scheme could fail such as in conditions of imperfect channel-state-information, outdated channel information, and in cases where the best relay is busy in some scheduling and load balancing duties in other parts of the network. Closed-from expression is derived for the end-to-end (e2e) outage probability assuming Rayleigh fading channels. Furthermore, to get more insights about the system behavior, the performance is studied at the high signal-to-noise ratio (SNR) regime where the diversity order and coding gain are derived. Monte-Carlo simulations are given to verify the achieved results. The main results show that the number of primary receivers affects the system performance through affecting the coding gain and not the diversity order. Unlike the existing papers where the same spectrum band is assumed to be shared by the primary receivers with the secondary users, our findings demonstrate that increasing the number of primary receivers in the proposed scenario enhances the system performance. Finally, results illustrate that when the interference at the secondary relays or destination or at both scales with SNR, the system achieves a zero diversity order and a noise floor appears in the results due to the effect of interference on the system performance.

      PubDate: 2016-10-30T14:41:38Z
      DOI: 10.1016/j.phycom.2016.10.001
  • Cyclic feature suppression for physical layer security
    • Authors: Z. Esat Ankaralı; Hüseyin Arslan
      Abstract: Publication date: Available online 22 September 2016
      Source:Physical Communication
      Author(s): Z. Esat Ankaralı, Hüseyin Arslan
      Cyclic prefix (CP) deploying techniques such as orthogonal frequency division multiplexing (OFDM) and single carrier frequency domain equalization (SC-FDE) offer considerable advantages in terms of equalizing time dispersive effect of wireless channel at the expense of a reasonable spectral redundancy. However, CP introduces cyclic features to the signal which can also be exploited for signal interception, blind parameter estimation and synchronization, and therefore, compromises the security of the signal against eavesdropping attacks. In order to provide a covert communication against such attacks, in this paper, we present two novel techniques that suppress the cyclic features of the CP utilizing signals while maintaining their advantages in equalization without reducing spectral efficiency. The first technique is built on a CP selection strategy while the second one is based on randomizing the symbol time. We also performed peak-to-average power ratio mitigation and out-of-band leakage suppression along with the cyclic feature concealing in the second technique at the expense of a reasonable complexity and signaling. Subsequent to the presentation of the proposed techniques, their performances are discussed and compared for OFDM and SC-FDE in terms of complexity and bit-error-rate along with cyclic feature suppression. 1 1 A part of this study is presented in IEEE Military Communication Conference (MILCOM), 2014.

      PubDate: 2016-10-16T08:58:51Z
      DOI: 10.1016/j.phycom.2016.09.003
  • Power allocation for cognitive underlay networks with spectrum band
    • Authors: Hung Tran; Georges Kaddoum; François Gagnon
      Abstract: Publication date: Available online 5 October 2016
      Source:Physical Communication
      Author(s): Hung Tran, Georges Kaddoum, François Gagnon
      In this paper, we study the cooperative communication of a cognitive underlay network by utilizing the diversity of multiple spectrum bands. In particular, we assume that the transmission power of the secondary user (SU) is subject to different joint constraints, such as peak interference power of the multiple primary users (PUs), peak transmission power of the SU, outage tolerate interference, and outage probability threshold. Accordingly, two power allocation schemes are considered on the basis of the minimum interference channel from the SU to the PU and the channel state information of the primary user link. Furthermore, the SU can select one of the three transmission modes following the channel state conditions, namely as cellular, device-to-device, or switching mode, to transmit the signal to the secondary user receiver. Given this setting, two power allocation schemes over a spectrum band selection strategy are derived. In addition, closed-form expressions for the outage probability of three modes are also obtained to evaluate the performance of the secondary network. Most importantly, a closed-form expression for the peak interference power level of the PU, which is considered as one of the most important parameters to control the SU’s transmission power, is derived by investigating the relation of two considered power allocation schemes in the practise. Finally, numerical examples show that the outage performance of secondary network in the switching mode outperforms the one of the cellular and device-to-device (D2D) mode for all considered power allocation schemes.

      PubDate: 2016-10-16T08:58:51Z
      DOI: 10.1016/j.phycom.2016.09.004
  • Secure degrees of freedom in cooperative K-helper MIMO cognitive radio
    • Authors: Hua Ping; Jitendra Tugnait
      Abstract: Publication date: Available online 21 September 2016
      Source:Physical Communication
      Author(s): Hua Mu, Ping Lu, Jitendra K. Tugnait
      We study the achievable secure degrees of freedom (DoF) in a cooperative MIMO cognitive radio system comprised of one primary source–destination pair, multiple secondary source–destination pairs and an eavesdropper against whom the primary user intends to secure its data. In this system, multiple secondary user pairs help to secure primary user’s data against eavesdropping. In return, these secondary users are allowed to access primary user’s spectrum. All users, including primary user pair, K ≥ 2 secondary user pairs and the eavesdropper are equipped with M antennas. We investigate the secure DoF without the knowledge of eavesdropper’s channel state information (CSI), using the interference alignment concept combined with a zero inter-user interference constraint. A beamforming design is proposed to achieve secure DoF d for the primary user and DoF d for all secondary users if K d ≤ M . The case of untrusted secondary users is also investigated where the secondary users may potentially eavesdrop. Simulation examples corroborating the theoretical results are presented.

      PubDate: 2016-10-16T08:58:51Z
  • Secure communications in cognitive underlay networks over Nakagami-m
    • Authors: Nam-Phong Nguyen; Lam Thanh Trung Duong Nallanathan
      Abstract: Publication date: Available online 16 June 2016
      Source:Physical Communication
      Author(s): Nam-Phong Nguyen, Tu Lam Thanh, Trung Q. Duong, A. Nallanathan
      In this paper, the secure communication of a cognitive radio network (CRN) over Nakagami- m fading channel is investigated. An underlay protocol is used in the considered network, where the unlicensed users or secondary users (SUs) can operate simultaneously with the primary users (PUs) in the same spectrum bands providing that the transmit power of the SUs is constrained by not only the maximum tolerance interference at the PU’s receiver but also the maximum transmit power at the SU’s transmitter. The exact closed-form expressions of important secure performance metrics, i.e., secrecy outage probability (SOP) and secrecy capacity (SC), are derived. In addition, to give a deep insight into the secure performance trends, the asymptotic expression of the SOP is also obtained when the average signal-to-noise ratio (SNR) of the legitimate channel is high. It is proven that the considered system achieves full diversity gain regardless of the number of antennas at the eavesdropper. Finally, the correctness of our mathematical framework is verified by Monte Carlo simulations.

      PubDate: 2016-06-16T18:20:32Z
  • Algebraic soft decoding of Reed-Solomon codes with improved progressive
    • Authors: Lyu Chen
      Abstract: Publication date: Available online 10 June 2016
      Source:Physical Communication
      Author(s): Lyu Yi, Chen Li
      The algebraic soft decoding (ASD) algorithm for Reed-Solomon (RS) codes can correct errors beyond the half distance bound with a polynomial time complexity. However, the decoding complexity remains high due to the computationally expensive interpolation that is an iterative polynomial construction process. By performing the interpolation progressively, the progressive ASD (PASD) algorithm can adapt the decoding computation to the need, leveraging the average complexity of multiple decoding events. But the complexity reduction is realised at the expense of system memory, since the intermediate interpolation information needs to be memorised. Addressing this challenge, this paper proposes an improved PASD (I-PASD) algorithm that can alleviate the memory requirement and further reduce the decoding complexity. A condition on expanding the set of interpolated polynomials will be introduced, which excepts the need of performing iterative updates for the newly introduced polynomial. Further incorporating the re-encoding transform, the I-PASD algorithm can reduce the decoding complexity over the PASD algorithm by a factor of 1 / 3 and its memory requirement is at most half of the PASD algorithm. The complexity and memory requirement will be theoretically analysed and validated by numerical results. Finally, we will confirm that the complexity and memory reductions are realised with preserving the error-correction capability of the ASD algorithm.

      PubDate: 2016-06-16T18:20:32Z
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