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Communications Letters, IEEE

Issue 6 • Date June 2014

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Displaying Results 1 - 25 of 51
  • Table of contents

    Publication Year: 2014 , Page(s): C1 - C2
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    Freely Available from IEEE
  • IEEE Communications Letters publication information

    Publication Year: 2014 , Page(s): C2
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    Freely Available from IEEE
  • Least Maintenance Batch Scheduling in Cloud Data Center Networks

    Publication Year: 2014 , Page(s): 901 - 904
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (477 KB) |  | HTML iconHTML  

    Nowadays, to efficiently safeguard the uptime of data centers, system-scale preventive maintenance is necessary. If all servers are under maintenance at the same time, it will completely disrupt the service continuity of all virtual machines that run over servers, thus it necessitates the proposition of an appropriate multi-batch scheme in which during each batch only a partial set of servers are maintained, leaving the remaining servers still on to fully support the virtual machine operations. To enable the cost-saving multi-batch scheme, in this letter, we aim to minimize the total number of batches to implement the system-scale maintenance, meanwhile guaranteeing the system service continuity. We propose a novel heuristic to solve the problem which can well achieve the problem lower bound. View full abstract»

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  • On Optimum Decoding of Certain Product Codes

    Publication Year: 2014 , Page(s): 905 - 908
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (346 KB) |  | HTML iconHTML  

    Optimum decoding of a class of product codes is investigated. The class is the one given by the serial concatenation of a binary single-parity-check code with a low-dimension binary linear block code. It was proved by Wolf that maximum likelihood decoding for this class of product codes can be efficiently performed through the Viterbi algorithm over a compact trellis representation of the code. In this letter, it is showed that the decoding complexity can be further reduced by formulating the decoding problem as a symbol-wise maximum-a-posteriori decision problem. Results illustrated for suitably designed codes show that the proposed algorithm significantly outperforms conventional iterative decoders. Finally, a generalization of the code construction, enjoying the same low-complexity decoding principle is presented and analyzed, achieving tangible coding gains at moderate error rates. View full abstract»

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  • PLC Performance Analysis Assuming BPSK Modulation Over Nakagami- m Additive Noise

    Publication Year: 2014 , Page(s): 909 - 912
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (171 KB) |  | HTML iconHTML  

    In this letter, we derive a maximum likelihood receiver of binary phase shift keying signals over Nakagami-m distributed additive noise in power line communication system. The decision variable is characterized by using copula approach. The analytical average bit error rate of the considered scheme is numerically evaluated by using the cumulative distribution function of the decision variable. It is shown by simulations that the proposed receiver performs significantly better than an existing suboptimal receiver. View full abstract»

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  • On the Use of Photon Arrival-Times for Non-Line-of-Sight Solar-Blind UV Channels

    Publication Year: 2014 , Page(s): 913 - 916
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (526 KB) |  | HTML iconHTML  

    A non-line-of-sight (NLOS) solar-blind UV link can be modelled as a stochastic photon-limited channel with memory. There are two fundamental observations for the received photons: their instantaneous arrival times and their counts during one channel use. In this letter, we compare achievable information rates for NLOS channels with these observables under uniform, binary-input rectangular on-off keying modulation. Simulation results show that gains in information rates can be realized when photon arrival times can be observed rather than only their counts especially for highly dispersive NLOS channels. View full abstract»

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  • Universal Encoding Scheme for General Zig-Zag Network

    Publication Year: 2014 , Page(s): 917 - 920
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (224 KB) |  | HTML iconHTML  

    In recent works, authors discussed upper bound for unequal capacity network called zig-zag network. It shows that there are several variants of upper bounds starting from cut set bound according to topology of the zig-zag network. We propose an universal coding structure, on which the same detection and decoding strategy can be applied to achieve any particular variants of cut set bound. View full abstract»

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  • Topology Inference With Network Tomography Based on t-Test

    Publication Year: 2014 , Page(s): 921 - 924
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (272 KB) |  | HTML iconHTML  

    Network tomography is a promising inference technique for network topology from end-to-end measurements. In this letter, we propose a novel binary tree pruning algorithm based on t-test to infer the network topology. A binary tree topology is first inferred using the existing Agglomerative Likelihood Tree (ALT) method, and then two samples t-test is applied to prune the binary tree, thus a general tree corresponding to the real topology is obtained. A lower bound on the correctly identified probability of the proposed method is derived. Simulation results show that the pruning method based on t-test outperforms the method which prunes the binary tree using a fixed threshold. View full abstract»

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  • A Serial Layered Scheduling Algorithm for Factor Graph Equalization

    Publication Year: 2014 , Page(s): 925 - 928
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (619 KB) |  | HTML iconHTML  

    This letter proposes a novel factor graph equalization based on a serial layered scheduling (SLS) algorithm of belief propagation, where the channel convolutional matrix is decomposed according to the distribution of its non-zero elements. In the SLS algorithm based factor graph equalization, factor nodes are classified into multiple layers referring to the decomposition of channel convolutional matrix, and the a posteriori probabilities message is updated based on a serial layer-by-layer mechanism. This proposed SLS algorithm clearly decreases the signal-to-noise ratio (SNR) threshold and also increases the convergence speed of equalization process, which results in a higher reliability and a lower latency of equalization process. Compared with current parallel flooding scheduling (PFS) algorithm, the convergence speed of SLS algorithm increases almost by twice, and its SNR threshold reduces by 7 dB over the Proakis-C channel. View full abstract»

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  • Three-Dimensional Channel Characteristics for Molecular Communications With an Absorbing Receiver

    Publication Year: 2014 , Page(s): 929 - 932
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (458 KB) |  | HTML iconHTML  

    Within the domain of molecular communications, researchers mimic the techniques in nature to come up with alternative communication methods for collaborating nanomachines. This letter investigates the channel transfer function for molecular communications via diffusion. In nature, information-carrying molecules are generally absorbed by the target node via receptors. Using the concentration function, without considering the absorption process, as the channel transfer function implicitly assumes that the receiver node does not affect the system. In this letter, we propose a solid analytical formulation and analyze the signal metrics (attenuation and propagation delay) for molecular communication via diffusion channel with an absorbing receiver in a 3-D environment. The proposed model and the formulation match well with the simulations without any normalization. View full abstract»

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  • Outage Probability of Two-Way Full-Duplex Relaying With Imperfect Channel State Information

    Publication Year: 2014 , Page(s): 933 - 936
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (228 KB) |  | HTML iconHTML  

    In this letter, we investigate two-way full-duplex (TWFD) relaying with a residual loop interference (LI). In the TWFD relaying, two full-duplex users exchange data with each other via a full-duplex relay, and each node attempts to subtract the estimate of the residual LI from its received signal. We derive the exact integral and approximate closed-form expressions for the outage probability of the TWFD relaying in case of perfect and imperfect channel state information. Monte Carlo simulations verify the validity of analytical results. View full abstract»

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  • A Secure Information Transmission Scheme With a Secret Key Based on Polar Coding

    Publication Year: 2014 , Page(s): 937 - 940
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (308 KB) |  | HTML iconHTML  

    In this letter, a new secure information transmission scheme based on polar codes with a pre-shared secret key is proposed. In polar codes, after the channel polarization is induced, good split channels are used to transmit the user message and bad channels are utilized to support the reconstruction of the message by sharing fixed information. If the fixed information in bad channels is secret, an adversary gets difficulty in reconstructing the user message in good channels without knowledge of the fixed information. From this observation, we construct a secure information transmission scheme. By appending pre-/post-processing that imposes a dependency between the transmitted message sub-blocks, the adversary's difficulty can be changed to an intractability, since only partial information can be decodable by attackers. A new class of secret key scheme is developed in such a way. View full abstract»

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  • Simplified Compression of Redundancy Free Trellis Sections in Turbo Decoder

    Publication Year: 2014 , Page(s): 941 - 944
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (273 KB) |  | HTML iconHTML  

    It has been recently shown that a sequence of R = q(M - 1) redundancy free trellis stages of a recursive convolutional decoder can be compressed in a sequence of L = M - 1 trellis stages, where M is the number of states of the trellis and q is a positive integer. In this paper, we show that for an M state Turbo decoder, among the L compressed trellis stages, only m = 3 or even m = 2 are necessary. The so-called m-min algorithm can either be used to increase the throughput for decoding a high rate turbo-code and/or to reduce its power consumption. View full abstract»

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  • On Detection Method for Soft Iterative Decoding in the Presence of Impulsive Interference

    Publication Year: 2014 , Page(s): 945 - 948
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (750 KB) |  | HTML iconHTML  

    This paper deals with the performance improvement of soft iterative decoders in impulsive interference modeled by additive noise. In case of α-stable noise, the inputs of the belief propagation decoder are too complex to compute. We propose to use an approximation of the log likelihood ratio in an impulsive environment. Even with this simplification, we show that the performance stays close to the one obtained using the true probability density function. Moreover, the robustness of our solution against the parameter estimation is investigated. View full abstract»

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  • Low-Complexity Sphere Decoding Detector for Generalized Spatial Modulation Systems

    Publication Year: 2014 , Page(s): 949 - 952
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (291 KB) |  | HTML iconHTML  

    This letter presents a sphere decoding strategy for generalized spatial modulation (GSM) systems. The proposed modifications reduce the exhaustive tree search for lattice points and exploits the structure of GSM, restraining the tree branches to those that result in valid antenna combinations. As a result, every found lattice point results in valid GSM transmitted symbols. The numerical results exhibit significant complexity reduction. View full abstract»

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  • Nested Maximum Likelihood Group Detection in Generalized Spatial Modulation MIMO Systems

    Publication Year: 2014 , Page(s): 953 - 956
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (633 KB) |  | HTML iconHTML  

    This letter presents a new detection scheme for the generalized spatial modulation MIMO system. The strategy is based on the successive use of maximum likelihood detectors, applied in a nested fashion, to variable-length partitions of the post-equalization received signal. The choice of the antenna combination mapping, named spatial constellation, as well as the detection ordering strategy are key design factors to the implementation of the high-performance and low-complexity detector. Simulation results show the substantial performance advantage of the proposed detector compared with current suboptimal receivers. View full abstract»

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  • ANC-ALOHA: Analog Network Coding ALOHA for Satellite Networks

    Publication Year: 2014 , Page(s): 957 - 960
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (433 KB) |  | HTML iconHTML  

    We propose a new random access protocol based on reservation ALOHA (R-ALOHA), called ANC-ALOHA, for applying analog network coding (ANC) to the slotted ALOHA channel of satellite networks (SATNETs). Although ANC promises excellent performance in SATNETs, ANC is not guaranteed in slotted ALOHA owing to the inherent randomness. R-ALOHA can be used to acquire a slot for ANC, but there are still two remaining problems to be overcome. First, the reservation maintenance of R-ALOHA does not work for ANC owing to the superposed signals. Second, a channel estimation scheme for ANC is needed in a slotted ALOHA channel. ANC-ALOHA exploits a keep-on sequence as the preamble and postamble of a burst for ANC to solve the above issues. The reduced payload size and delayed transmission are also proposed to assure the reception of the keep-on sequence. We derived an analytic model to verify the throughput of ANC-ALOHA, and validated it based on the simulation results. The results indicate that ANC-ALOHA significantly improves the channel throughput compared to R-ALOHA. View full abstract»

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  • Spatial Group Based Random Access for M2M Communications

    Publication Year: 2014 , Page(s): 961 - 964
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4121 KB) |  | HTML iconHTML  

    We expect that the number of machine-to-machine (M2M) devices will rapidly increase in the near future due to a growing demand for a wide range of M2M applications such as e-health, public safety, surveillance, remote maintenance and control, and smart metering. Therefore, the future cellular networks should accommodate a large number of M2M devices and their random access (RA) requests at a specific time instant. In this letter, we propose a novel RA scheme to effectively increase the number of available preambles for the future M2M communication environment. The proposed scheme provides additional preambles by spatially partitioning a cell coverage into multiple group regions and reducing cyclic shift size in RA preambles. As a result, the proposed RA scheme can accommodate a significantly larger number of machine nodes with much lower collision probability and shorter random access delay, compared to a conventional RA scheme. View full abstract»

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  • A Downstream Power Back-Off Procedure for Mixed FTTC and FTTDp Scenarios

    Publication Year: 2014 , Page(s): 965 - 968
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (409 KB) |  | HTML iconHTML  

    VDSL2 achieves high bit rates thanks to far-end crosstalk suppression and proper selection of the access network infrastructure. In this paper, we consider one architectural solution, which adopts the standard VDSL2 profile in a Fiber-To-The-Distribution point (FTTDp). During the transition process, FTTDp has to coexist with Fiber-To-The-Cabinet (FTTC) in a mixed VDSL2 scenario. Downstream Power Back-Off (DPBO) for FTTDp is effective to mitigate interference among FTTC and FTTDp. When FTTC terminals are vectored, DPBO leads to reduction of the maximum bit rate for FTTDp as compared to FTTC. In this paper, we propose a modification of the ITU DPBO procedure for FTTC and FTTDp to achieve the same bit rate. The maximum power assigned to FTTDp users is now proportional to the average received power of the vectored FTTC users at the Distribution Point. We obtain the proportionality coefficient, which depends on the number of active FTTC and FTTDp terminals and it is independent of the sub-carrier frequency. View full abstract»

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  • Ergodic Secrecy Sum-Rate for Downlink Multiuser MIMO Systems With Limited CSI Feedback

    Publication Year: 2014 , Page(s): 969 - 972
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB) |  | HTML iconHTML  

    This paper investigates the ergodic secrecy sum-rate for the downlink multiuser MIMO system with independent confidential messages, each of which is intended for one of the users and should keep secret from others. We adopt zero-forcing beamforming with limited channel state information (CSI) feedback at the transmitter, and derive the closed-form expression for the ergodic secrecy sum-rate. Moreover, we analyze some of its asymptotic characteristics, which provide guidance on secure transmission design. Finally, all theoretical results are validated by numerical simulations. View full abstract»

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  • Energy-Efficient RSSI-Based Localization for Wireless Sensor Networks

    Publication Year: 2014 , Page(s): 973 - 976
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB) |  | HTML iconHTML  

    Sensor positioning is a fundamental block in many location-dependent applications of wireless sensor networks. Although the main objective in localization is primarily enhancing the positioning accuracy, the importance of energy consumption and localization accuracy poses new challenges. The localization is usually assisted with some self-known position sensors called anchor nodes. In this letter, optimal power allocation for the anchor nodes in a sense of minimizing the energy consumption considering estimation errors is investigated. To have a better estimation of the relative distance between the anchor and unknown nodes using received signal strength indicator (RSSI), average energy of the received beacon is introduced as a new decision metric. Based on this, a squared position error bound as an accuracy parameter is derived, and an optimization problem is proposed to maximize the localization performance. More specifically, the optimal power allocation policy is first derived for the case that the anchor nodes estimate their own locations with no error. Since there are unavoidable errors in the positions of the anchor nodes, the optimization problem is then modified by including uncertainty in the positions of the anchor nodes. The results show that a substantial reduction in power consumption can be achieved by optimal allocation of the transmission power. View full abstract»

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  • Energy Efficient Network Deployment With Cell DTX

    Publication Year: 2014 , Page(s): 977 - 980
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (499 KB) |  | HTML iconHTML  

    Cell discontinuous transmission (DTX) is a new feature that enables sleep mode operations at base station (BS) side during the transmission time intervals when there is no traffic. In this letter, we analyze the maximum achievable energy saving of the cell DTX. We incorporate the cell DTX with a clean-slate network deployment and obtain optimal BS density for lowest energy consumption satisfying a certain quality of service requirement considering daily traffic variation. The numerical result indicates that the fast traffic adaptation capability of cell DTX favors dense network deployment with lightly loaded cells, which brings about considerable improvement in energy saving. View full abstract»

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  • Comments on “IEEE 1588 Clock Synchronization Using Dual Slave Clocks in a Slave”

    Publication Year: 2014 , Page(s): 981 - 982
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (103 KB) |  | HTML iconHTML  

    In the above letter, Chin and Chen proposed an IEEE 1588 clock synchronization method based on dual slave clocks, where they claim that multiple unknown parameters-i.e., clock offset, clock skew, and master-to-slave delay-can be estimated with only one-way time transfers using more equations than usual. This comment investigates Chin and Chen's dual clock scheme with detailed models for a master and dual slave clocks and shows that the formulation of multi-parameter estimation is invalid, which affirms that it is impossible to distinguish the effect of delay from that of clock offset at a slave even with dual slave clocks. View full abstract»

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  • An Enhanced Signal-Timing-Offset Compensation Algorithm for Coordinated Multipoint-to-Multiuser Systems

    Publication Year: 2014 , Page(s): 983 - 986
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (892 KB) |  | HTML iconHTML  

    In coordinated multipoint-to-multiuser systems, since coordinated base stations (BSs) may transmit their signals simultaneously to multiple user equipments (UEs) and a UE may receive signals with different signal timing offsets (STOs) from different BSs at given time-slots and subcarriers, it is impossible for BSs to pre-compensate or for UEs to post-compensate the STOs as they do it in multipoint-to-user or point-to-multiuser systems, respectively. In this letter, we convince by demonstrations that the STOs cannot be completely eliminated by any compensation algorithm. In addition, we propose a novel STO compensation algorithm associated with tolerant residual STOs to minimize the STOs, and discuss in details how to calculate the pre-compensation vector at BSs. Simulation results indicate that the proposed algorithm is capable of mitigating the STOs effectively to tolerable values, and outperforms state of the art approaches. View full abstract»

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  • Guard Beacon: An Energy-Efficient Beacon Strategy for Time Synchronization in Wireless Sensor Networks

    Publication Year: 2014 , Page(s): 987 - 990
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (367 KB) |  | HTML iconHTML  

    In this paper, we present Guard Beacon, which is a beacon strategy to reduce the energy consumption of time synchronization in wireless sensor networks (WSNs). In a low duty-cycled sensor network, a node may miss incoming synchronization beacons because of wrong active/sleep mode due to clock drift. Therefore, it is critical to guarantee that beacons arrive at the receiver at the right time. The proposed method, i.e., Guard Beacon, can reduce the overall power consumption of synchronization while guaranteeing a very high probability that the synchronization packet is received, by sending multiple beacons within a synchronization round. By investigating on the energy tradeoff between sending and receiving beacons, we find an optimal iterative solution as well as a suboptimal analytical solution as to how many beacons should be sent and when to send them. The strategy is implemented in a real-world testbed for experiment validation. The results show that the proposed Guard Beacon may save more than 40% synchronization power consumption compared with the existed Single Beacon strategy and is also more energy efficient than RTSP in multihop networks. View full abstract»

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George K. Karagiannidis
Aristotle University of Thessaloniki
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