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Communications Letters, IEEE

Issue 10 • Date October 2013

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Displaying Results 1 - 25 of 40
  • Table of contents

    Publication Year: 2013 , Page(s): c1 - c4
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    Freely Available from IEEE
  • [Staff list]

    Publication Year: 2013 , Page(s): c2
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  • Capture-Aware Estimation for the Number of RFID Tags with Lower Complexity

    Publication Year: 2013 , Page(s): 1873 - 1876
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (140 KB) |  | HTML iconHTML  

    Capture effect is very common in wireless communication systems. In a passive radio frequency identification (RFID) system, even though multiple tags backscatter their signals to a reader simultaneously, one of the tags will be successfully identified due to the capture effect. In this letter, we propose an algorithm which will optimize the identification efficiency of a dynamic frame length ALOHA RFID protocol under capture effect. The proposed algorithm estimates the number of tags and the probability of capture effect. From these parameters, an optimal frame length can be obtained. The advantage of the algorithm is that it does not need many steps to search an extreme value for the estimation. It thus reduces the computational complexity. Computer simulation results show that the proposed method's identification efficiency is almost identical to existing algorithms, but at lower computational complexity. View full abstract»

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  • Human Mobility Patterns in Cellular Networks

    Publication Year: 2013 , Page(s): 1877 - 1880
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (281 KB) |  | HTML iconHTML  

    This letter investigates inter-arrival time, dwell time distributions and other mobility patterns in mobile cellular networks. It has been generally assumed and widely accepted that both inter-arrival time and dwell time distributions can be well approximated by exponential distribution. However, based on real cellular data measurements, we evaluate the fitness of various typical statistical distributions such as power-law, exponential, Weibull, lognormal and Rayleigh distributions, and find that a power-law distribution fits both inter-arrival time and dwell time more precisely. Besides, mobility patterns in daytime, night, rural and urban areas provide further demonstrations of the power-law model. Moreover, new models on the distributions of inter-departure time and the number of arrived subscribers are also proposed to characterize other mobility patterns, and the corresponding simulation results are well consistent with the empirical ones. View full abstract»

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  • A Low Complexity Modulation Classification Algorithm for MIMO Systems

    Publication Year: 2013 , Page(s): 1881 - 1884
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (144 KB) |  | HTML iconHTML  

    A novel algorithm is proposed for automatic modulation classification in multiple-input multiple-output spatial multiplexing systems, which employs fourth-order cumulants of the estimated transmit signal streams as discriminating features and a likelihood ratio test (LRT) for decision making. The asymptotic likelihood function of the estimated feature vector is analytically derived and used with the LRT. Hence, the algorithm can be considered as asymptotically optimal for the employed feature vector when the channel matrix and noise variance are known. Both the case with perfect channel knowledge and the practically more relevant case with blind channel estimation are considered. The results show that the proposed algorithm provides a good classification performance while exhibiting a significantly lower computational complexity when compared with conventional algorithms. View full abstract»

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  • Optimal Discriminant Functions Based on Sampled Distribution Distance for Modulation Classification

    Publication Year: 2013 , Page(s): 1885 - 1888
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (125 KB) |  | HTML iconHTML  

    In this letter, we derive the optimal discriminant functions for modulation classification based on the sampled distribution distance. The proposed method classifies various candidate constellations using a low complexity approach based on the distribution distance at specific testpoints along the cumulative distribution function. This method, based on the Bayesian decision criteria, asymptotically provides the minimum classification error possible given a set of testpoints. Testpoint locations are also optimized to improve classification performance. The method provides significant gains over existing approaches that also use the distribution distance of the signal features. View full abstract»

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  • Hybrid Maximum Likelihood Modulation Classification Using Multiple Radios

    Publication Year: 2013 , Page(s): 1889 - 1892
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (147 KB) |  | HTML iconHTML  

    In this paper, we focus on amplitude-phase modulations and propose a modulation classification framework based on centralized data fusion using multiple radios and the hybrid maximum likelihood (ML) approach. In order to alleviate the computational complexity associated with ML estimation, we adopt the Expectation Maximization (EM) algorithm. Due to SNR diversity, the proposed multi-radio framework provides robustness to channel SNR. Numerical results show the superiority of the proposed approach with respect to single radio approaches as well as to modulation classifiers using moments based estimators. View full abstract»

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  • Partially Connected Interference Networks with No CSIT: Symmetric Degrees of Freedom and Multicast Across Alignment Blocks

    Publication Year: 2013 , Page(s): 1893 - 1896
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (175 KB) |  | HTML iconHTML  

    We explore the symmetric degrees of freedom (DoF) of partially connected interference networks for the case in which transmitters have no knowledge of their channel states (channel coefficients and coherence times) but are aware of the network topology. In particular, we consider interference networks which have no internal conflicts in their alignment graph. This class of networks can be used to model various interference scenarios in modern wireless systems. A sufficient condition is established for which half DoF can be achieved per message, which coincide with the best known outer bound, thereby establishing the optimal symmetric DoF. For networks in this class that do not satisfy the sufficient condition, a systematic achievable scheme, termed multicast across alignment blocks, is derived and an analytical expression is obtained for the achieved symmetric DoF. The new scheme is based on our insight that an interference alignment-based scheme may not utilize all available signalling dimensions, and the unused signalling dimensions can be further exploited through multicast transmission. View full abstract»

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  • Design Methodology for Maximum Power Transmission, Optimal BER-SNR and Data Rate in Biomedical Implants

    Publication Year: 2013 , Page(s): 1897 - 1900
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (255 KB) |  | HTML iconHTML  

    Using Pulse-Width Modulation Amplitude-Shift Keying (PWM-ASK) in biomedical implants enables the simultaneous transmission of wireless energy as well as data using a single inductive link. This paper approaches Pulse-Width Modulated Amplitude-Shift Keying (PWM-ASK) from a communication theory point of view. It provides a design methodology to obtain high data rate while maintaining an optimal BER (Bit Error Rate), and optimal power transfer in biomedical implants. View full abstract»

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  • Out-of-Band Power Reduction in NC-OFDM with Optimized Cancellation Carriers Selection

    Publication Year: 2013 , Page(s): 1901 - 1904
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (187 KB) |  | HTML iconHTML  

    In this letter, we propose a computationally efficient method for joint selection of cancellation carriers (CCs) and calculation of their values minimizing the out-of-band (OOB) power in non-contiguous (NC-) OFDM transmission. The proposed new CCs selection method achieves higher OOB power attenuation than algorithms known from literature as well as noticable reception performance improvement. View full abstract»

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  • Efficient and Fair Power and Subchannel Allocation in Multiuser OFDM Networks

    Publication Year: 2013 , Page(s): 1905 - 1907
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (117 KB) |  | HTML iconHTML  

    We present an efficient and fair scheme for allocating resources in the downlink of multiuser OFDMA cellular networks based on Nash Bargaining Solution (NBS). Although NBS provides a fair and optimum approach in order to maximize the total rate of the network, there is no simple solution for the case of K users. The proposed algorithm satisfies the minimum rate requirement of each user first and allocates the excess subchannels by searching over the K × N subchannels to noise ratio matrix based on the bargaining process happening between the base station and the users. Hence, the complexity reduces from order O(KN) to O(N × K). View full abstract»

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  • Optimal Power Allocation in an "Off" Spectrum Sensing Interval for Cognitive Radio

    Publication Year: 2013 , Page(s): 1908 - 1911
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (191 KB) |  | HTML iconHTML  

    Most of the current works about cognitive radio favor a constant power allocation policy during an "off" spectrum sensing interval, which is the time between two spectrum sensing activities when the outcome of the first spectrum sensing indicates "off". However, according to our work, this policy becomes suboptimal with respect to bit error rate minimization, when the traffics of primary user follow an alternating renewal process. Therefore, under this scenario, we suggest the optimal power allocation policy, by solving a convex optimization problem on power allocation of secondary user. Our results provide meaningful insight into the design of transmitting schemes for cognitive radio. View full abstract»

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  • Performance Analysis of AF Based Hybrid Satellite-Terrestrial Cooperative Network over Generalized Fading Channels

    Publication Year: 2013 , Page(s): 1912 - 1915
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (172 KB) |  | HTML iconHTML  

    In this paper, the transmission of signals in a hybrid satellite-terrestrial link is considered. In particular, we address the problem of amplify-and-forward (AF) relaying in a hybrid satellite-terrestrial link, where a masked destination node receives the relayed transmission from a terrestrial link and direct transmission from the satellite link. The satellite-relay and satellite-destination links are assumed to follow the Shadowed-Rician fading; and the channel of the terrestrial link between the relay and destination is assumed to follow the Nakagami-m fading. The average symbol error rate of the considered AF cooperative scheme for M-ary phase shift keying constellation is derived for these generalized fading channels. Moreover, analytical diversity order of the hybrid system is also obtained. View full abstract»

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  • WFRFT Precoding for Narrowband Interference Suppression in DFT-Based Block Transmission Systems

    Publication Year: 2013 , Page(s): 1916 - 1919
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (178 KB) |  | HTML iconHTML  

    In this letter, we present a new approach to narrowband interference (NBI) suppression utilizing the weighted-type fractional Fourier transform (WFRFT) as a precoding scheme in the DFT-based communications systems. The proposed scheme can degenerate into a single carrier (SC) or a multi-carrier (MC) frequency division multiple access block transmission system by means of WFRFT parameter selection, which also leads to a variation of residual energy distribution of NBI following a frequency domain avoidance strategy. By virtue of parameter optimization of the WFRFT, the proposed system can outperform both SC and MC systems with regards to NBI suppression. View full abstract»

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  • An Inter Symbol Interference Estimation and Cancellation Scheme for Asynchronous Distributed Differential Space-Time Code

    Publication Year: 2013 , Page(s): 1920 - 1923
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (330 KB) |  | HTML iconHTML  

    In cooperative communication systems, as poor synchronization of different relays may induce inter symbol interference (ISI) and lead to substantial performance degradation, it is necessary to cancel ISI. In this letter, a simple ISI estimation and cancellation scheme is proposed for asynchronous distributed differential space-time code, where the destination node does not need to know the channel state information (CSI) from the source node to different relays or the CSI from the relays to the destination node. Simulation results show that the proposed scheme can cancel ISI effectively and obtain good bit error rate performance. View full abstract»

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  • Energy Efficiency and Spectral Efficiency Tradeoff in Interference-Limited Wireless Networks

    Publication Year: 2013 , Page(s): 1924 - 1927
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (176 KB) |  | HTML iconHTML  

    This letter investigates the fundamental tradeoff between energy efficiency (EE) and spectral efficiency (SE) for interference-limited wireless networks (IWNs), which is a nonconvex optimization and NP-hard problem. A general algorithm procedure (GAP) embedded with an iterative power allocation algorithm (IPAA) is proposed, which has good performance with the advantages of fast convergence, low complexity and insensitivity to initial values. Simulation results explicitly depict the EE-SE tradeoff curve for IWNs. View full abstract»

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  • A Small World Network Model for Energy Efficient Wireless Networks

    Publication Year: 2013 , Page(s): 1928 - 1931
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (110 KB) |  | HTML iconHTML  

    Wireless ad hoc networks can be modeled as small world networks based on the complex network theory. In this letter, we propose a new energy efficient small world network model which considers the battery energy of the wireless nodes, the multi-hop transmission distance and the geographical distance between wireless nodes. In order to quantify the energy efficiency of the proposed model, we propose a new energy efficiency metric which jointly considers: 1) the energy efficiency of the wireless links, and 2) the impact of a wireless node on the entire network. By adopting the proposed metric, we evaluate the energy efficiency of each wireless node and the entire network. Our results show that the proposed model: 1) follows the small world feature, and 2) is more energy efficient compared to a random network. View full abstract»

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  • Error Rates of M-PAM and M-QAM in Generalized Fading and Generalized Gaussian Noise Environments

    Publication Year: 2013 , Page(s): 1932 - 1935
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (147 KB) |  | HTML iconHTML  

    This letter investigates the average symbol error probability (ASEP) of pulse amplitude modulation and quadrature amplitude modulation coherent signaling over flat fading channels subject to additive white generalized Gaussian noise. The new ASEP results are derived in a generic closed-form in terms of the Fox H function and the bivariate Fox H function for the extended generalized-K fading case. The utility of this new general closed-form is that it includes some special fading distributions, like the Generalized-K, Nakagami-m, and Rayleigh fading and special noise distributions such as Gaussian and Laplacian. Some of these special cases are also treated and are shown to yield simplified results. View full abstract»

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  • Power Minimization for Cognitive Relay Networks with Interference-Based Strategy

    Publication Year: 2013 , Page(s): 1936 - 1939
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (397 KB) |  | HTML iconHTML  

    For the cognitive relay networks, an optimal power allocation algorithm is proposed to minimize the total power consumption, under the promise for the anti-interference performance of the primary subsystem and throughput constraints of the secondary subsystem. An interference-based strategy is presented to use different power allocation methods according to the interferences created by the secondary subsystem to the primary subsystem, comparing with the location-aware strategy in which the channel conditions are considered only with the location information. A kind of computing algorithm joint the subgradient and Newton's methods is also given to resolve the complex optimization problem. The numerical results demonstrate the strength of our proposed schemes. View full abstract»

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  • Interference Mitigation through Cross Polarized Transmission in Femto-Macro Network

    Publication Year: 2013 , Page(s): 1940 - 1943
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (172 KB) |  | HTML iconHTML  

    Femtocells use co-channel allocation with macrocells resulting in cross-tier interference which eventually degrades the system performance. Cross-polarized data transmission is proposed as a potential approach towards improving the spectral efficiency and at the same time permitting co-channel allocation in cellular systems. This letter evaluates a scenario where femtocell network makes use of right-hand circular polarization (RHCP) and macrocell network makes use of left-hand circular polarization (LHCP) for simultaneous transmissions even when using the same frequency spectrum. The polarizations being orthogonal to each other due to their sense of rotation ensure isolation between the networks and hence promotes interference-free independent operation with better coverage and higher throughput. View full abstract»

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  • Low-Complexity Energy-Efficient Power and Subcarrier Allocation in Cooperative Networks

    Publication Year: 2013 , Page(s): 1944 - 1947
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (204 KB) |  | HTML iconHTML  

    This letter addresses the joint subcarrier and power allocation problem in downlink multiuser OFDM cooperative networks. The sum of the logarithmic per user time-averaged bits-per-Joule is maximized. The optimization problem is decomposed into two subproblems. First, the solution for the subcarrier allocation considering the proportional fairness is obtained. Second, an alternating power allocation (PA) scheme with separate transmit power constraints at the source and relays is derived under frequency selective fading channels. Then the complexity of the proposed scheme is analyzed. Finally, numerical results present the convergence, energy efficiency and outage probability performance of the proposed scheme. View full abstract»

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  • Opportunistic Cooperative Communication in the Presence of Co-Channel Interferences and Outdated Channel Information

    Publication Year: 2013 , Page(s): 1948 - 1951
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (251 KB) |  | HTML iconHTML  

    This paper investigates the impacts of co-channel interference and outdated channel state information (CSI), two main issues in practical operating environment, on the performance of opportunistic decode-and-forward cooperative networks. First, the distribution function of the effective signal-to-interference-plus-noise ratio at the end receiver is derived. Then, exact closed-form expressions for the error and outage probabilities are obtained. Furthermore, simple asymptotic expressions for the error probability, which explicitly show the coding and the diversity gains, are derived and discussed. In particular, it is demonstrated that the diversity order of the system is reduced to unity when CSI is outdated, and to zero when the ratio of the interference energy to the signal energy is constant. View full abstract»

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  • On the Performance of Interference-Aware Cognitive Ad-Hoc Networks

    Publication Year: 2013 , Page(s): 1952 - 1955
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (145 KB) |  | HTML iconHTML  

    In this paper we analyze the effects of channel availability on channel access delay and service probability of cognitive networks using a modified IEEE 802.11 Media Access Control Protocol (MAC). For the designed cognitive network, cognitive communication is limited by the interference imposed on primary users. We determine the probability of accessing the channel under Rayleigh fading condition for this opportunistic network. We then use this probability to determine the embedded Markov model of the cognitive nodes. We use this Markov model to determine the average channel access delay, and service rate of cognitive nodes. Both simulation and analytical results are presented to access the system performance. View full abstract»

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  • Max-Min Energy Efficient Beamforming for Multicell Multiuser Joint Transmission Systems

    Publication Year: 2013 , Page(s): 1956 - 1959
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (141 KB) |  | HTML iconHTML  

    Energy efficient communication technology has attracted much attention due to the explosive growth of energy consumption in current wireless communication systems. In this letter we focus on fairness-based energy efficiency and aim to maximize the minimum user energy efficiency in the multicell multiuser joint beamforming system, taking both dynamic and static power consumptions into account. This optimization problem is a non-convex fractional programming problem and hard to tackle. In order to find its solution, the original problem is transformed into a parameterized polynomial subtractive form by exploiting the relationship between the user rate and the minimum mean square error, and using the fractional programming theorem. An iterative algorithm with proved convergence is then developed to achieve a near-optimal performance. Numerical results validate the effectiveness of the proposed solution and show that our algorithm significantly outperforms the max-min rate optimization algorithm in terms of maximizing the minimum energy efficiency. View full abstract»

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  • Enhanced Non-Seamless Offload for LTE and WLAN Networks

    Publication Year: 2013 , Page(s): 1960 - 1963
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (318 KB) |  | HTML iconHTML  

    Non-seamless WLAN offload is a currently available approach to the data explosion issue in cellular networks without requiring new hardware and functional deployment on network sides. In this article, we propose two enhanced offloading methods that guarantee session continuity for non-seamless WLAN offload. We describe how the proposed methods manipulate multi-radio (LTE and WiFi) interfaces to maintain IP sessions in the dynamics of available radios. We present a performance analysis that studies the throughput and energy consumption of smart devices. View full abstract»

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Aristotle University of Thessaloniki
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