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Communications Letters, IEEE

Issue 1 • Date January 2014

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Displaying Results 1 - 25 of 36
  • Table of contents

    Page(s): c1 - c4
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    Freely Available from IEEE
  • Staff List

    Page(s): c2
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    Freely Available from IEEE
  • Editorial note and Reviewer Appreciation Program 2013

    Page(s): 1
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    Freely Available from IEEE
  • Optimal Data Rate for Reliable Packet Communications in Laplace Noise

    Page(s): 2 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (156 KB) |  | HTML iconHTML  

    Vehicular, military and industrial field wireless deployments take place in harsh environments affected by impulsive noise. This letter proposes the use of a selective automatic repeat request (SR-ARQ) scheme where the data transmission rate is optimized in order to minimize the mean delay. The optimization procedure is proposed in relation to the use of a soft-limiting detector that eliminates out-of-amplitude noise at the receiving end. The superiority of the optimized SR-ARQ scheme over different alternatives is clearly shown in the letter. View full abstract»

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  • Achievable Degrees of Freedom of the Four-User MIMO Y Channel

    Page(s): 6 - 9
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (138 KB) |  | HTML iconHTML  

    In this letter, we investigate the achievable degrees of freedom (DoF) of four-user MIMO Y channel where four users each with M antennas intend to exchange messages via a relay of N antennas. By adopting the signal space alignment and a new transmission scheme which jointly align the subspace of unpaired signals from three different users among all the four users, we derive that the DoF per user of max{min(M,3/8N), min(6/7M, N/2)} can be achieved for this channel. Since signal space alignment relies on the dimensions of intersection space of two users, we show that the signal space is utilized efficiently without the restriction of two-user intersection space in the proposed scheme. View full abstract»

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  • Optimal Power Allocation for MIMO Fully Cooperative Relay Broadcast Channels

    Page(s): 10 - 13
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (190 KB) |  | HTML iconHTML  

    We investigate a multiple input multiple output (MIMO) relay broadcast channel (RBC) with fully cooperation between users. A beamforming and combining design is proposed based on singular value decomposition (SVD) of the channel matrix between users. Then, users can simultaneously relay each other's information on the same frequency band with zero interference from each antenna's transmit signal on its received signal. Also, two optimal closed-form solutions are derived for power allocation (PA) under both total power and individual power constraints. View full abstract»

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  • Reduced-Complexity Antenna Selection Schemes in Spatial Modulation

    Page(s): 14 - 17
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (292 KB) |  | HTML iconHTML  

    In this paper, we investigate low complexity antenna selection schemes in spatial modulation (SM). Firstly, we propose a reduced complexity antenna selection scheme based on pairwise error probability (PEP). It demonstrates that there is almost no performance loss in the proposed scheme compared to the original algorithm, while the complexity can be significantly reduced especially with high modulation order. Secondly, we propose an antenna selection scheme based on antenna correlation. It is a novel antenna selection criterion which is fundamentally different from those in traditional multiple-input multiple output (MIMO) systems. It also reduces the computation complexity by orders of the square of modulation order. View full abstract»

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  • Bit Error Probability Analysis of SSK in DF Relaying with Threshold-Based Best Relay Selection and Selection Combining

    Page(s): 18 - 21
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (199 KB) |  | HTML iconHTML  

    In this letter, we analyze the end-to-end average bit error probability (ABEP) of space shift keying (SSK) in cooperative relaying with decode-and-forward (DF) protocol, considering multiple relays with a threshold based best relay selection, and selection combining of direct and relayed paths at the destination. We derive an exact analytical expression for the end-to-end ABEP in closed-form for binary SSK, where analytical results agree with simulation results. For non-binary SSK, approximate analytical and simulation results are presented. View full abstract»

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  • Denoising Detection for the Generalized Spatial Modulation System Using Sparse Property

    Page(s): 22 - 25
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (105 KB) |  | HTML iconHTML  

    Generalized spatial modulation (GSM) is a novel scheme developed from the conventional single-active antenna spatial modulation (SA-SM). The challenge of the GSM lies at the receiving end. Since more than one antenna is activated, the complexity of ML detection for GSM is much higher than that for SA-SM, especially if the number of antennas is large. Low complexity sub-optimal detections, such as ZF detection or MMSE detection, can be used to detect GSM. However, the performance of these detections is poor and cannot yet be applied in an underdetermined system. Spatial modulation has an inherent property of sparsity. However, to the best of our knowledge, this property has not been used for GSM. In this paper, we exploit this property and propose a sub-optimal detection algorithm. The traditional algorithm using sparsity is sensitive to noise and not suitable for the application to communication systems. Therefore, we employ a denoising scheme to counter the effect of the background noise. View full abstract»

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  • Secret Key Agreement by LLR Thresholding and Syndrome Feedback over AWGN Channel

    Page(s): 26 - 29
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (394 KB) |  | HTML iconHTML  

    In this paper we propose novel advantage distillation and reconciliation approaches for secret key agreement (SKA) over additive white Gaussian noise (AWGN) (possibly fading) channels, using binary phase shift keying (BPSK) constellations. For advantage distillation Bob selects bits having an absolute log-likelihood ratio (LLR) larger than some threshold. For reconciliation, Alice transmits the syndrome of the selected bits with respect to a globally pre-shared forward error correcting (FEC) code. We show that the syndrome transmission does not diminish the advantage of Bob over Eve on the key knowledge, thus being an efficient solution. For the proposed scheme we derive both a lower bound on the achievable secret key rate with ideal wiretap coding, and the effective throughput achieved by using practical codes. View full abstract»

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  • Energy-Efficient Opportunistic Interference Alignment

    Page(s): 30 - 33
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (135 KB) |  | HTML iconHTML  

    We introduce an energy-efficient distributed opportunistic interference alignment (OIA) scheme that greatly improves the sum-rates in multiple-cell uplink networks while reducing the transmit power consumption compared to the conventional OIA scheme. In the proposed scheme, each user employs optimal transmit vector design and power control strategy in the sense of minimizing the amount of generated interference to other-cell base stations while satisfying a given required signal quality. Our main result indicates that owing to the reduced interference level, the proposed OIA method attains larger sum-rates than those of OIA with no power control (i.e., with full transmit power) for almost all signal-to-noise ratio regions, thus resulting in improved energy efficiency. View full abstract»

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  • Interference Coordination with Vertical Beamforming in 3D MIMO-OFDMA Networks

    Page(s): 34 - 37
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (252 KB) |  | HTML iconHTML  

    This paper investigates interference coordination for 3-dimension (3D) antenna array systems in multicell multiple-input multiple-output (MIMO) and orthogonal frequency division multiple-access (OFDMA) wireless networks. Cell-center user and cell-edge user specific downtilts are accordingly partitioned through dynamic vertical beamforming in the 3D MIMO-OFDM communication systems. Taking these user specific downtilts into consideration, the objective of our proposed interference coordination scheme is to maximize both the cell-center users' and cell-edge users' throughput, subject to per evolved NodeB (eNB) power and downtilt constraints. To solve the interference coordination problem, a novel partial joint processing (JP) coordinated multiple point (COMP) based dual decomposition method (JC-DDM) is proposed, where resource block (RB) assignment, power allocation (RAPA) and downtilt adjustment are jointly optimized. Simulation results demonstrate the efficacy of our proposed JC-DDM. View full abstract»

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  • Traffic-Aware Energy Optimization in Green LTE Cellular Systems

    Page(s): 38 - 41
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (139 KB) |  | HTML iconHTML  

    Commercial deployment of 4G LTE networks and rapid penetration of smart phones have exponentially increased the wireless data traffic, thus increasing the energy consumption and greenhouse (CO2) gas emission. The concept of green 4G LTE networks lies in the development of energy efficient LTE systems for reducing the greenhouse emissions as well as operators' energy bill. In this letter we first identify the complexity of the optimal traffic awareness in LTE networks and subsequently design a cooperative communication framework for traffic-aware energy optimization. The LTE eNBs explore an information theoretic approach to capture the dynamics and uncertainty of network traffic. Subsequently, using an online, stochastic game theoretic algorithm, the eNBs communicate amongst themselves to optimize the traffic awareness. Optimal traffic awareness helps in reducing the network energy consumption. Simulation results demonstrate that our framework results in almost 22% (40 KW-Hr) daily energy savings across a LTE network of 400 cells. View full abstract»

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  • Compressed Sensing Based Protocol for Interfering Data Recovery in Multi-Hop Sensor Networks

    Page(s): 42 - 45
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (314 KB) |  | HTML iconHTML  

    We consider a multi-hop wireless sensor network that measures sparse events and propose a novel protocol based on Compressed Sensing (CS) as an alternative to traditional Media Access Control (MAC) scheduling and routing protocol. Instead of avoiding collisions, our CS-based protocol exploits interferences by superimposing the data measurements "over-the-air", simultaneously received at any node. Thanks to our protocol design, each node is able to recover and forward only new data towards the sink. Our protocol achieves near zero reconstruction errors at the sink, while greatly reducing overhead and delays compared to conventional methods. These results reveal a new and promising approach to protocol design through CS. View full abstract»

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  • A Novel Adaptive Digital Phase-Lock-Loop for Modern Digital GNSS Receivers

    Page(s): 46 - 49
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1039 KB) |  | HTML iconHTML  

    This paper presents a novel adaptive digital phase-lock-loop for modern digital global navigation satellite system receivers. A Kalman filtering method with an adaptive scheme to adjust the noise statics is employed to change the equivalent noise bandwidth by using empirical knowledge of the signal-to-noise ratio and the signal dynamics in response to the faded signals and the user dynamics. View full abstract»

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  • On Ergodic Secrecy Rate for MISO Wiretap Broadcast Channels with Opportunistic Scheduling

    Page(s): 50 - 53
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (148 KB) |  | HTML iconHTML  

    In this letter, we study on-off opportunistic beamforming for the multiuser downlink channel with a passive eavesdropper. Two opportunistic scheduling schemes exploiting multiuser diversity are investigated which require limited feedback of the effective signal-to-noise ratio (SNR) from the legitimate users. For the two scheduling schemes, we derive new closed-form expressions for the ergodic secrecy rate with on-off beamforming over Rayleigh fading channels. Numerical results are provided to verify our analytical results and illustrate the impact of multiuser diversity on the secrecy performance. View full abstract»

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  • On the Closed-Form Performance Analysis of Maximal Ratio Combining in Shadowed-Rician Fading LMS Channels

    Page(s): 54 - 57
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (467 KB) |  | HTML iconHTML  

    In this paper, the maximal ratio combining (MRC) scheme in Shadowed-Rician (SR) fading land mobile satellite (LMS) channels is studied. The MRC scheme for SR fading LMS channels has been studied in existing literature; however, most of the existing analytical results are in the form of infinite power series, which are not in closed-form. In this paper, we derive approximate closed-form expressions of the probability density function and cumulative distribution function of the received signal-to-noise ratio of the MRC based receiver in SR fading LMS channels. Then we provide approximate closed-form expressions of the bit error rate (BER), outage probability, and capacity of the considered scheme. One of the derived closed-form BER expressions is found useful for obtaining the analytical diversity order and coding gain of the considered MRC scheme. View full abstract»

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  • Improving the Packet Delivery Performance for Concurrent Packet Transmissions in WSNs

    Page(s): 58 - 61
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (633 KB) |  | HTML iconHTML  

    In this letter, we investigate the properties of packet collisions in IEEE 802.15.4-based wireless sensor networks when packets with the same content are transmitted concurrently. While the nature of wireless transmissions allows the reception of a packet when the same packet is transmitted at different radios with (near) perfect time synchronization, we find that in practical systems, platform specific characteristics, such as the independence and error of the crystal oscillators, cause packets to collide disruptively when the two signals have similar transmission powers (i.e., differences of <;2 dBm). In such scenarios, the packet reception ratio (PRR) of concurrently transmitted packets falls below 10%. Nevertheless, we empirically show that the packet corruption patterns are easily recoverable using forward error correction schemes and validate this using implementations of RS and convolutional codes. Overall, our results show that using such error correction schemes can increase the PRR by more than four-fold. View full abstract»

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  • Outage Probability and DMT Performance of Underlay Cognitive Networks with Incremental DF and AF Relaying over Nakagami-m Fading Channels

    Page(s): 62 - 65
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (177 KB) |  | HTML iconHTML  

    This letter studies the outage performance of cognitive radio systems with incremental decode-and-forward (DF) and amplify-and-forward (AF) relaying in a Nakagami-m fading environment. The outage behavior and diversity-multiplexing tradeoff (DMT) are investigated. These results indicate that the DMT is irrelevant to the primary user and the secondary system can achieve the full diversity order. Simulation results substantiate the accuracy of our analysis. The presented method/steps for performance evaluation are applicable to other fading channels. View full abstract»

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  • Performance Optimization of MIMO Y Channels: Interference Alignment and Signal Detection

    Page(s): 66 - 69
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (210 KB) |  | HTML iconHTML  

    In this letter, we propose a combined scheme of interference alignment and signal detection to optimize the performance of a multiple-input multiple-output (MIMO) Y channel, which consists of three users and a middle relay equipped with nU and nR antennas, respectively. First, an iterative interference alignment algorithm is introduced to optimize both beamforming and combining vectors by minimizing the spillage of the interference signals, and ensuring that the desired signals fall into the orthogonal complement of the interference subspace. Then, a signal detection scheme, which employs feed-forward and feedback filters, is applied at the relay to further deal with system interferences. Simulation results show that the proposed combined scheme for MIMO Y channels produces a significant improvement over the existing schemes. View full abstract»

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  • Aspiration Level-Based Strategy Dynamics on the Coexistence of Spectrum Cooperation and Leasing

    Page(s): 70 - 73
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (369 KB) |  | HTML iconHTML  

    As an emerging approach in alleviating mobile data explosion, cognitive radio is adopted with diverse network models to promote wireless spectrum sharing between primary users (PUs) and secondary users (SUs). However, owing to PUs' priority, SUs may have to suspend their transmission before it is finished. Therefore, this letter considers the coexistence of cooperative cognitive radio networks and spectrum leasing markets which can offer SUs fixed transmission opportunity for their transmission. By adopting aspiration level to model SUs' behavior, we formulate SUs' strategy dynamics as a Discrete Time Markov Chain and illustrate the existence of stable state of the system under different cases through preliminary results. View full abstract»

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  • Smart Relaying for Selection Combining Based Decode-and-Forward Cooperative Networks

    Page(s): 74 - 77
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (282 KB) |  | HTML iconHTML  

    This letter proposes three smart relaying strategies, including power allocation, continuous power control, and discrete power control strategies, to mitigate the error propagation problem for single-relay decode-and-forward cooperative networks using selection combining at the destination. By fully exploiting the channel state information at the relay, these relaying strategies can optimize transmit power so as to minimize the bit error rate of the system, as well as allowing the source and relay nodes to use different modulation levels to improve spectral efficiency. Simulation results demonstrate that the proposed smart relaying strategies can effectively mitigate erroneous relaying and achieve diversity orders close to two. View full abstract»

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  • Outage Performance of Two-Way Fixed Gain Amplify-and-Forward Relaying Systems with Asymmetric Traffic Requirements

    Page(s): 78 - 81
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (144 KB) |  | HTML iconHTML  

    In this letter, we investigate the outage performance of two-way relaying system based on the fixed gain amplify-and-forward protocol and asymmetric traffic requirements. At first, we propose a three-step scheme to obtain the channel state information with a low-complexity relay. Then, the exact expression of system outage performance is derived and we further investigate the asymptotic performance at high signal-to-noise ratio. Finally, numerical results are given to verify the analytical results. View full abstract»

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  • Joint Beamforming and User Selection in Multicast Downlink Channel under Secrecy-Outage Constraint

    Page(s): 82 - 85
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (255 KB) |  | HTML iconHTML  

    In this letter, we study the beamforming and user selection problem in multicast MISO wiretap-channel, where a base station (BS) with Nt antennas broadcasts a common confidential message to M legitimate users (Bobs) and N unauthorized users (Eves) attempt to eavesdrop the message. We target at maximizing the minimum secrecy-outage rate of Bobs and propose an iterative successive convex approximation (SCA) algorithm to tackle the original nonconvex problem. We further develop joint semidefinite programming (SDP) and SCA algorithm to find a feasible subset where legitimate users are guaranteed to their requirements. Simulation results are provided to evaluate the proposed approaches. View full abstract»

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  • Lowering the Error Floor of LDPC Codes Using Multi-Step Quantization

    Page(s): 86 - 89
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (117 KB) |  | HTML iconHTML  

    A multi-step scheme is proposed for the input quantization of message-passing decoders for low-density parity-check (LDPC) codes. The proposed scheme, which is applicable to both regular and irregular codes, lowers the error floor significantly at the cost of small increase in complexity, memory and latency. View full abstract»

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IEEE Communications Letters  is aimed at satisfying the need for rapid dissemination of information, offering a vehicle for authors to expose their results to be used in future developments. This ensures early recognition of work. 

 

 

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Editor-in-Chief
George K. Karagiannidis
Aristotle University of Thessaloniki
Greece