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Communications Letters, IEEE

Issue 9 • Date September 2011

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Displaying Results 1 - 25 of 44
  • Table of contents

    Publication Year: 2011 , Page(s): c1 - c4
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    Freely Available from IEEE
  • Staff List

    Publication Year: 2011 , Page(s): c2
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    Freely Available from IEEE
  • Call for Papers

    Publication Year: 2011 , Page(s): 905
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    Freely Available from IEEE
  • Aeronautical ICI Analysis and Doppler Estimation

    Publication Year: 2011 , Page(s): 906 - 909
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (238 KB) |  | HTML iconHTML  

    In this letter, we investigate OFDM performance in aeronautical data networks (ADN). In ADN, Doppler spread depicts different characteristics compared to terrestrial channel. The intercarrier interference (ICI) analysis is performed analytically. We investigate the parametric eigenvector decomposition spectrum methods for estimating the Doppler shifts. View full abstract»

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  • Combating Frequency Selectivity of OFDM Radio Channels by Partial Data Spreading

    Publication Year: 2011 , Page(s): 910 - 912
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (177 KB) |  | HTML iconHTML  

    The performance of OFDM transmission over frequency selective fading radio channels can be improved by spreading the data elements of each OFDM symbol over all OFDM subcarriers. This known approach to frequency diversity is termed Full Data Spreading (FDS) and would render data detection prohibitively complex. In order to affordably seize the advantage of frequency diversity by data spreading, we propose the scheme Partial Data Spreading (PDS), in which each data element is spread only over an appropriately chosen subset of the OFDM subcarriers. View full abstract»

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  • Sequential Linear MIMO Precoder Optimization for Hybrid ARQ Retransmission of QAM Signals

    Publication Year: 2011 , Page(s): 913 - 915
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (254 KB) |  | HTML iconHTML  

    Our investigation centers on the issue of linear precoding for hybrid-ARQ retransmissions in linear multi-input-multi-output (MIMO) channels driven by non-Gaussian inputs. Leveraging recent works on single transmission MIMO precoding , we derive the gradient of input-output mutual information with respect to precoder matrix for optimization. We further establish that the right eigenvectors of optimum precoder are determined by the associated minimum mean-square error (MMSE) matrix. We then propose a gradient algorithm for maximizing the mutual information. Compared with precoders designed for Gaussian input, our new precoders can significantly improve the input-output mutual information, especially at low signal-to-noise ratio (SNR) and for lower dimensional constellations. View full abstract»

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  • Channel Coding Diversity with Mismatched Decoding Metrics

    Publication Year: 2011 , Page(s): 916 - 918
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (169 KB) |  | HTML iconHTML  

    We analyze the performance of channel coding diversity with general decoding metrics in terms of the generalized mutual information (GMI). We show that the GMI of the diversity channel is less than or equal to the baud-rate weighted sum of the component GMIs; and equality is achieved only in special cases. We then focus on bit-interleaved coded modulation (BICM) schemes and demonstrate the applicability of our findings by an example of hybrid free-space optical and radio-frequency (FSO-RF) communication. View full abstract»

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  • User Scheduling and Adaptive Multilevel Modulation for SC-FDMA with Iterative Multiuser Detection

    Publication Year: 2011 , Page(s): 919 - 921
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (247 KB) |  | HTML iconHTML  

    This letter investigates the problem of user selection with adaptive multilevel modulation for a single-carrier frequency division multiple access system with iterative multiuser detection. Multiple users sharing a common set of subcarriers, called a chunk, cause multiple access interference (MAI) which degrades quality-of-service (QoS). To guarantee QoSs of the users and achieve multiuser diversity, the proposed algorithm allocates each chunk to users with favorable channel conditions. However, despite this user scheduling, the improvement of spectral efficiency is limited at high SNR due to the MAI. In order to effectively mitigate MAI, we employ adaptive multilevel modulation which adjusts the number of layers at each user selection. Simulation results show that the proposed algorithm improves spectral efficiency compared to conventional algorithms. View full abstract»

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  • Sensitivity of Quadratic Gaussian Matching to Interference

    Publication Year: 2011 , Page(s): 922 - 924
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (177 KB) |  | HTML iconHTML  

    It is well known that uncoded transmission of a memoryless Gaussian source over a memoryless additive white Gaussian noise channel results in optimal performance theoretically attainable. When there is additional interference in the channel, uncoded transmission is robust. It achieves the same sensitivity performance as optimal performance, measured using sensitivity results of Pinsker, Prelov, and Verdu. View full abstract»

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  • A Note on "A Hybrid Selection/Equal-Gain Combining over Correlated Nakagami-m Fading Channels"

    Publication Year: 2011 , Page(s): 925
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (102 KB) |  | HTML iconHTML  

    We point out that the best combination of branches (BCB) cannot be ensured by using the branch selection scheme proposed in if the number of available diversity branches is greater than two. View full abstract»

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  • Uplink Timing Misalignment in Open and Closed Access OFDMA Femtocell Networks

    Publication Year: 2011 , Page(s): 926 - 928
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (233 KB) |  | HTML iconHTML  

    We focus on an uplink network composing of femtocell access points (FAPs), macrocell users (MUs) and a macrocell base station (MBS) employing orthogonal frequency division multiple access (OFDMA) signaling. Synchronization of MUs at the MBS results in asynchronous signal arrivals at the FAPs which may induce intercarrier interference (ICI). Given a fixed distance between an FAP and the MBS, we derive a closed-form expression for the probability of an MU causing ICI to the FAP. Then, we extend this to obtain the probability of an open and closed access FAP experiencing ICI in the presence of a fixed number of MUs, and the average number of open and closed access FAPs experiencing ICI. View full abstract»

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  • An Effective Pre-Filtering Method with a Propagator for TOA-Based Range Estimation Using Chirp Signal

    Publication Year: 2011 , Page(s): 929 - 931
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (336 KB) |  | HTML iconHTML  

    In this letter, an effective pre-filtering method is proposed with Propagator for accurate time-of-arrival (TOA)-based range estimations. For TOA estimation using subspace fitting techniques such as Propagator, the received signals must be transformed into sinusoid. After the transformation, the bandwidth of the sinusoids is no longer dependent on the transmitted baseband signal but on channel parameters. By applying the pre-filtering method with the sinusoids, we can remove the outband noise of the sinusoids and this leads to more accurate TOA estimation due to the noise reduction. The effectiveness of the proposed pre-filtering method was analyzed and verified through Monte-carlo simulations in additive white Gaussian noise (AWGN) and multipath channels. View full abstract»

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  • Dynamic Spectrum Allocation Algorithm with Interference Management in Co-Existing Networks

    Publication Year: 2011 , Page(s): 932 - 934
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (210 KB) |  | HTML iconHTML  

    This work addresses analytically the impact of multi-cell, multi-operator interference on the overall radio resources when multiple operators co-exist and share a common pool of spectrum. We propose a centralised dynamic spectrum allocation (DSA) scheme that is able to measure the interference level and interact dynamically to minimise interference and enhance spectrum utilisation while maintaining a satisfactory level of QoS. Furthermore, a concise system model and framework able to describe the interaction among different operators is presented. View full abstract»

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  • Outage Analysis of Distributed Scheme on Opportunistic Relaying with Limited CSI

    Publication Year: 2011 , Page(s): 935 - 937
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (240 KB) |  | HTML iconHTML  

    In this letter, we propose a distributed scheme on opportunistic amplify-and-forward (AF) relaying to minimize the system outage probability with low feedback overhead. Only the subset of relays report the calculated outage probability information to the source based on the outage probability threshold with the limited channel state information (CSI). We present the approximate expressions for the system outage probability under two scenarios, the statistical CSI and the statistical quantized CSI of the relay-destination links, respectively. Numerical results indicate that the derived analytic results are reasonable and the outage performance is better for the statistical quantized CSI case with acceptable feedback cost. View full abstract»

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  • Distributed MIMO Precoding Strategies in a Multicell Environment

    Publication Year: 2011 , Page(s): 938 - 940
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (276 KB) |  | HTML iconHTML  

    We investigate distributed multiple-input multiple-output (MIMO) precoding schemes for coping with the intercell interference in a multicell environment. In particular, we introduce the effective channel matrix for two different precoding strategies, referred to as received interference-aware precoding (RIAP) and generated interference-aware precoding (GIAP). Then, we propose a hybrid precoding scheme and a switching scheme. Simulation results are provided to compare the performance in a multicell environment. View full abstract»

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  • Effects of Antenna Correlation in MIMO Two Hop AF Relay Network over Rayleigh-Rician Channels

    Publication Year: 2011 , Page(s): 941 - 943
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (249 KB) |  | HTML iconHTML  

    In this letter, we investigate the performance of multiple input multiple output (MIMO) amplify-and-forward (AF) relay network over Rayleigh-Rician asymmetric channel with antenna correlation. We consider multiple correlated antennas at all nodes and general correlation matrices are assumed with arbitrary eigenvalue distribution. Specifically we derive the outage probability and the average symbol error rate (SER) for end-to-end signal-to-noise ratio (SNR). Moreover, simple asymptotic results are derived in high SNR in order to obtain the diversity gain variation. Finally, Monte Carlo simulations verify the accuracy of the analytical results. View full abstract»

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  • Ballooning: An Agent-Based Search Strategy in Wireless Sensor and Actor Networks

    Publication Year: 2011 , Page(s): 944 - 946
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (608 KB) |  | HTML iconHTML  

    Due to the actor mobility and duty cycle of sensor nodes, the data forwarding from sensor nodes to mobile actors is a challenging issue. Motivated by the research results in multi-agent systems, we consider the search packet as an agent moving in the network to search mobile actors. Then a strategy called ballooning is proposed to control the search process. The theoretical and numerical results show that the ballooning strategy can forward the search packet to mobile actors with bounded delay and efficient energy consumption. View full abstract»

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  • Universality of Performance Parameters in Vehicular ad hoc Networks

    Publication Year: 2011 , Page(s): 947 - 949
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (172 KB) |  | HTML iconHTML  

    Vehicular ad hoc networks can exist for very short periods of time; in that time data must be transmitted to neighbours and other interested devices. The latency of the data when crossing the medium is an important metric to study when designing intelligent transport systems and safety-of-life applications. We present a study of a substantial parameter space to expose universal behaviours, that enables the efficiency of the network to be measured and analysed. We show that the communication density function, of Jiang et al. , can reduce the complexity of the network behaviours and that average latencies for a network can be calculated from a single function. View full abstract»

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  • Closed-Form Sum-MSE Minimization for the Two-User Gaussian MIMO Broadcast Channel

    Publication Year: 2011 , Page(s): 950 - 952
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (199 KB) |  | HTML iconHTML  

    We study the Gaussian multiple-input, multiple-output broadcast channel, where a base station with N_T antennas transmits K independent messages to K users, each having a single receive antenna. The messages consist of independent, identically distributed Gaussian random variables and we study linear transmission with an end-to-end distortion criterion. By using an already established uplink/downlink duality and a recently discovered special relation between beamforming vectors and channel vectors, we present a closed-form expression for the optimal power allocation in the two-user case. We also outline an iterative algorithm that finds the optimal power allocation for an arbitrary number of users. View full abstract»

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  • Codebook Design for MIMO Retransmission System

    Publication Year: 2011 , Page(s): 953 - 955
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (266 KB) |  | HTML iconHTML  

    This letter proposes a new retransmission structure with multiple retransmission codebooks for a linear precoding-based closed-loop multiple-input multiple-output (CL-MIMO) system. While conventional codebooks are defined only for the initial transmission in CL-MIMO systems, we propose a multiple codebook structure in which a different codebook is used for each retransmission, instead of a single identical codebook for every retransmission. Simulation results indicate that in slowly fading channels the proposed scheme achieves a larger gain over the conventional scheme using a single codebook, especially as the number of antennas increases. View full abstract»

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  • A Periodic Frequency Band Rotation Scheme for Multi-Cell Coordination Clustering

    Publication Year: 2011 , Page(s): 956 - 958
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (490 KB) |  | HTML iconHTML  

    Lots of attention to achieve cell edge performance has been made in future wireless networks. Through multi-cell coordination clustering, we can reduce co-channel interference, resulting in cell edge performance improvement. This letter proposes a periodic frequency band rotation clustering scheme for joint transmissions in multi-cell configuration. Through mathematical interference analysis, we show that the inter-cluster interference can be reduced and cell edge data rate is improved over existing schemes. View full abstract»

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  • Optimal Power Allocation for the Two-Way Relay Channel with Data Rate Fairness

    Publication Year: 2011 , Page(s): 959 - 961
    Cited by:  Papers (19)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (206 KB) |  | HTML iconHTML  

    This letter studies data rate fairness on the two-way relay channel. It analytically determines the optimal power values at both nodes and at the relay, that lead to a maximization of the sum rate under the fairness constraint. Amplify-and-Forward (AF) and Decode-and-Forward (DF) relaying protocols are considered. For AF, the optimization problem is turned into a single-variable convex optimization problem. For DF, rate balancing between Multiple Access and broadcast phases must be performed prior to setting nodes powers. Both optimized protocols are compared with reference AF and DF in terms of data rates through numerical simulations. View full abstract»

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  • Optimal Scheduler with Simplified Queue Structure for Multi-Channel Wireless Networks

    Publication Year: 2011 , Page(s): 962 - 964
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (165 KB) |  | HTML iconHTML  

    Advanced link technologies such as OFDMA and MIMO improve the throughput of wireless networks significantly by providing multiple channels operating in parallel. Even though a scheduling algorithm has been presented to attain the optimal throughput in this environment, it does not scale well with the increasing number of channels due to the underlying queue structure at links. We propose a new link scheduler with simplified queue structure, whose throughput is equivalent to the previous scheduler and delay performance is much better. View full abstract»

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  • On Collision Probabilities in Frequency-Domain Scheduling for LTE Cellular Networks

    Publication Year: 2011 , Page(s): 965 - 967
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (224 KB) |  | HTML iconHTML  

    In an Orthogonal Frequency Division Multiple Access (OFDMA) wireless network, inter-cell interference (ICI) is one of the main challenges, and is of special concern for users near the cell edge. ICI arises naturally from collisions of frequency resource assignments among neighboring base stations. An important performance parameter is the probability distribution of assignment collisions. In this paper, an exact analytical expression for the collision probability is derived for an arbitrary number of base stations with non-coordinated schedulers. The expression can be used to determine conditions under which ICI mitigation techniques may be required as well as to establish a baseline for performance comparison with ICI coordination schemes. For the important case of two base stations, the expression is particularly simple. Numerical results are presented to illustrate the analytical results. View full abstract»

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  • On the Performance Analysis of Multi-Hop Cooperative Relay Networks over Generalized-K Fading Channels

    Publication Year: 2011 , Page(s): 968 - 970
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (358 KB) |  | HTML iconHTML  

    This letter analyzes an amplify-and-forward (AF) transmission based multi-hop cooperative relay network (MCRN) over Generalized-K fading channels. In this letter, highly simplified, novel asymptotic expressions for the average symbol error rate and the outage probability of MCRNs over Generalized-K fading channels (with arbitrary fading parameters) are presented. Both theoretical analysis and simulations explicitly reveal that for MCRNs over Generalized-K fading channels, a diversity order of 2k is achieved when shadowing is more severe than fading and a diversity order of 2m is achieved when fading is more severe than shadowing (where k and m represent the Generalized-K distribution shape parameters). View full abstract»

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Aristotle University of Thessaloniki
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