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Communications Letters, IEEE

Issue 1 • Date Jan. 2006

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Displaying Results 1 - 25 of 25
  • IEEE Communications Letters

    Publication Year: 2006 , Page(s): 01 - 67
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    Freely Available from IEEE
  • IEEE Communications Society

    Publication Year: 2006 , Page(s): 02
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    Freely Available from IEEE
  • Optimal pilot sequence design for channel estimation in MIMO OFDM systems

    Publication Year: 2006 , Page(s): 1 - 3
    Cited by:  Papers (22)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (204 KB) |  | HTML iconHTML  

    In orthogonal frequency division multiplexing (OFDM) systems, since virtual subcarriers are not used for transmission, approach of conventional uniformly placed pilot tones is not applicable in some situations. In this letter, based on nonuniform pilot tone placement, we derive optimal pilot sequences, which can achieve the minimum mean square error of the least squares estimate for multiple-input multiple-output (MIMO) OFDM systems. Simulation results demonstrate the effectiveness of the proposed approach. View full abstract»

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  • Constant amplitude multi-code CDMA with built-in single parity check product code

    Publication Year: 2006 , Page(s): 4 - 6
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (271 KB) |  | HTML iconHTML  

    We show that a constant amplitude multi-code (CAMC) CDMA in a recursive structure can be reconfigured into a single parity check, product code (SPCPC). CAMC can benefit from error correction by parity decoding. We present an algorithm which reconfigures CAMC into an SPCPC structure and then refines the log likelihood ratio of the received bits in an iterative way. Computer simulation results show that CAMC has a superior performance of error correction than a generic SPCPC. Hence, CAMC provides both a low PAPR and robustness to bit errors. View full abstract»

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  • Outage probability of MRC with unequal-power cochannel interferers in correlated Rayleigh fading

    Publication Year: 2006 , Page(s): 7 - 9
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (230 KB) |  | HTML iconHTML  

    Under the assumption that the branch gains of the desired user signal and interfering signals experience Rayleigh fading and have the same correlation matrix, the outage probability of maximal ratio combining (MRC) in the presence of unequal-power cochannel interference (CCI) is derived for the two cases that the correlation matrix is equi-correlated and that the correlation matrix has different eigenvalues. View full abstract»

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  • Capacity of complexity-constrained noise-free CDMA

    Publication Year: 2006 , Page(s): 10 - 12
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (175 KB) |  | HTML iconHTML  

    An interference-limited noise-free CDMA downlink channel operating under a complexity constraint on the receiver is introduced. According to this paradigm, detected bits, obtained by performing hard decisions directly on the channel's matched filter output, must be the same as the transmitted binary inputs. This channel setting, allowing the use of the simplest receiver scheme, seems to be worthless, making reliable communication at any rate impossible. We prove, by adopting statistical mechanics notion, that in the large-system limit such a complexity-constrained CDMA channel gives rise to a non-trivial Shannon-theoretic capacity, rigorously analyzed and corroborated using finite-size channel simulations. View full abstract»

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  • Generalized Nakagami-m phase crossing rate

    Publication Year: 2006 , Page(s): 13 - 15
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (286 KB) |  | HTML iconHTML  

    This paper provides simple, exact, new closed-form expressions for the generalized phase crossing rate of Nakagami-m fading channels. Sample numerical results obtained by simulation are presented that validate the formulations developed here. A special case of this formulation is the Rayleigh case, whose result agrees with that obtained elsewhere in the literature. In passing, several new closed-form results concerning the statistics of the envelope, its in-phase and quadrature components, phase, and their time derivatives are obtained. View full abstract»

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  • Capacity of interference-limited ad hoc networks with infrastructure support

    Publication Year: 2006 , Page(s): 16 - 18
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (172 KB) |  | HTML iconHTML  

    In this letter, we consider the capacity of ad hoc networks with infrastructure support. Although Grossglauser-Tse mobile network model enables Θ(1) per-node throughput scaling, the mobility assumption may be too unrealistic to be accepted in some practical situations. One of the key observations we acquired is that the infrastructure support plays the same role played by the mobility in the Grossglauser-Tse model. We show that nodes can utilize the randomly located infrastructure support instead of mobility when nodes are nearly static. In this case, we show that the per-node throughput of Θ(1) is still achievable when the number of access points grows linearly with respect to the number of nodes. View full abstract»

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  • Meeting connectivity requirements in a wireless multihop network

    Publication Year: 2006 , Page(s): 19 - 21
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (251 KB) |  | HTML iconHTML  

    This paper investigates the connectivity probability of 1-dimensional ad hoc networks in which nodes have random, non-identically distributed locations, this leads to optimization of the number of nodes required. An empirical approach is used. We fit a parametric distribution to the CDF of the maximum distance between adjacent nodes. Special and extreme cases which are not covered by the empirical approach are treated separately. View full abstract»

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  • Wireless sensor networks for intrusion detection: packet traffic modeling

    Publication Year: 2006 , Page(s): 22 - 24
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (387 KB) |  | HTML iconHTML  

    Performance evaluation of wireless sensor network (WSN) protocols requires realistic data traffic models since most of the WSNs are application specific. In this letter, a sensor network packet traffic model is derived and analyzed for intrusion detection applications. Presented analytical work is also validated using simulations. View full abstract»

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  • Power delay profile and noise variance estimation for OFDM

    Publication Year: 2006 , Page(s): 25 - 27
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (226 KB) |  | HTML iconHTML  

    In this letter, we present cyclic-prefix (CP) based noise-variance and power-delay-profile estimators for Orthogonal Frequency Division Multiplexing (OFDM) systems. Signal correlation due to the use of the CP is exploited without requiring additional pilot symbols. A heuristic estimator and a class of approximate maximum likelihood (ML) estimators are proposed. The proposed algorithms can be applied to both unitary and non-unitary constellations. These algorithms can be readily used for applications such as minimum mean-square error (MMSE) channel estimation. View full abstract»

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  • A multiobjective approach for energy consumption and link stability issues in ad hoc networks

    Publication Year: 2006 , Page(s): 28 - 30
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (149 KB) |  | HTML iconHTML  

    This letter presents a novel analytical framework that jointly accounts the energy consumption and the link stability of mobile nodes. Two indexes for energy and link-lifetime are defined and a multiobjective integer linear programming problem has been defined. The proposed target function separates the energy and the link-stability contributions in order to differently change the weights of two opposite characteristics of mobile ad hoc networks. Some simulation results has been presented and the jointed impact of energy and stability has been evaluated. View full abstract»

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  • Price-based max-min fair rate allocation in wireless multi-hop networks

    Publication Year: 2006 , Page(s): 31 - 33
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (182 KB) |  | HTML iconHTML  

    The interaction between links in wireless multihop networks introduces extra constraints on the combinations of achievable flow rates. Algorithms have been proposed to achieve max-min fairness under these additional constraints. This letter provides a simple price-based max-min fair rate allocation scheme, building on a utility maximization scheme recently proposed for such networks. View full abstract»

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  • Queue length distribution of network packet traffic: Tsallis entropy maximization with fractional moments

    Publication Year: 2006 , Page(s): 34 - 36
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (120 KB) |  | HTML iconHTML  

    A framework based on maximization of Tsallis entropy constrained by fractional moments is proposed to model queue length distribution of number of packets in network traffic exhibiting long-range behavior. For appropriate range of the Tsallis entropy parameter q, it is found that the first moment of number of packets may not exist Based on Euler summation formula, explicit expressions for mean queue length and buffer overflow probability exhibiting power law behavior are obtained. It is shown that in the limiting case as q tends to 1, one recovers the asymptotic results for buffer overflow probability depicting Weibull-like tail. View full abstract»

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  • Exact crossing rates of dual diversity over unbalanced correlated Rayleigh channels

    Publication Year: 2006 , Page(s): 37 - 39
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (248 KB) |  | HTML iconHTML  

    General exact expressions for the level crossing rate of dual-branch selection, equal-gain, and maximal-ratio combiners operating over unbalanced correlated Rayleigh channels are derived. Sample numerical results are presented by specializing the general expressions to a space-diversity system with horizontally spaced omnidirectional antennas at the mobile station. It is observed that, whereas power imbalance is invariably prejudicial, fading correlation may be advantageous with closely spaced antennas arranged parallel to the direction of motion. View full abstract»

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  • Bit-interleaved space-time trellis coding for frequency selective block fading channels

    Publication Year: 2006 , Page(s): 40 - 42
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (236 KB) |  | HTML iconHTML  

    In this paper, the performance of a bit-interleaved space-time trellis coding (BISTTC) scheme is investigated for orthogonal frequency division multiplexing (OFDM) systems utilizing multiple antennas. The BISTTC scheme considered here concatenates the outer code with the well-known spacetime trellis code (STTC) through a bit interleaver. Compared to existing concatenation of BICM with space-time block code (STBC), BISTTC has significant performance advantage in applications with low spectral efficiency and simple outer code, due to its ability to exploit available diversity resources more efficiently. View full abstract»

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  • New results on unequal error protection using LDPC codes

    Publication Year: 2006 , Page(s): 43 - 45
    Cited by:  Papers (11)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (183 KB) |  | HTML iconHTML  

    In this letter, we propose a new scheme to construct low-density parity-check (LDPC) codes that are suitable for unequal error protection (UEP). We derive UEP density evolution (UDE) formulas for the proposed ensemble over the binary erasure channel (BEC). Using the UDE formulas, high performance UEP codes can be found. Simulation results depict an improvement in the bit error rate of more important bits in comparison with previous results on UEP-LDPC codes. View full abstract»

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  • Rateless coding over fading channels

    Publication Year: 2006 , Page(s): 46 - 48
    Cited by:  Papers (55)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (187 KB) |  | HTML iconHTML  

    We propose a framework for communication over fading channels utilizing rateless codes. An implementation using fountain codes is simulated, demonstrating that such a scheme has advantages in efficiency, reliability and robustness over conventional fixed-rate codes, particularly when channel state information is not available at the transmitter. View full abstract»

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  • BER prediction using EXIT charts for BICM with iterative decoding

    Publication Year: 2006 , Page(s): 49 - 51
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (174 KB) |  | HTML iconHTML  

    A method for the prediction of bit-error rates (BER) of bit-interleaved coded modulation systems with iterative decoding (BICM-ID) is presented, which is based solely upon the extrinsic information transfer (EXIT) chart and avoids extensive BER simulations. Comparisons show an accurate prediction, even for low BERs down to 10-6. Furthermore, an easy procedure to obtain the optimum rotation angle for a signal constellation set in conjunction with IQ Interleaving is described. Both methods can be applied to all types of channels. View full abstract»

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  • Comment on "Efficient maximum-likelihood decoding of q-ary modulated Reed-Muller codes"

    Publication Year: 2006
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (107 KB) |  | HTML iconHTML  

    It is shown that in the letter by Grant and van Nee (IEEE Commun. Lett., vol.2, p.134-6, 1998) the decoding algorithm was derived incorrectly, and therefore, maximum.-likelihood decoding performance is not achieved. The correct version of the decoding algorithm is then given. View full abstract»

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  • Optimal control of source and channel rate for VBR video transmission over VBR channels

    Publication Year: 2006 , Page(s): 53 - 55
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (132 KB) |  | HTML iconHTML  

    In this letter we propose a control-theoretic approach for the joint source and channel rate control problem of transporting variable bit-rate (VBR) compressed video over VBR channels. Compared with traditional solutions, our solution has no special requirements for the encoder and decoder buffer sizes, and can use much less memory and calculation time to achieve the optimal control. The proposed algorithm can be used in both off-line and on-line coding. View full abstract»

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  • Computation of bit-error probabilities for optical receivers using thin avalanche photodiodes

    Publication Year: 2006 , Page(s): 56 - 58
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (212 KB) |  | HTML iconHTML  

    The large-deviation-based asymptotic-analysis and importance-sampling methods for computing bit-error probabilities for avalanche-photodiode (APD) based optical receivers, developed by Letaief and Sadowsky [IEEE Trans. Inform. Theory, vol. 38, pp. 1162-1169, 1992], are extended to include the effect of dead space, which is significant in high-speed APDs with thin multiplication regions. It is shown that the receiver's bit-error probability is reduced as the magnitude of dead space increases relative to the APD's multiplication-region width. The calculated error probabilities and receiver sensitivities are also compared with those obtained from the Chernoff bound. View full abstract»

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  • Movement detection analysis in mobile IPv6

    Publication Year: 2006 , Page(s): 59 - 61
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (207 KB) |  | HTML iconHTML  

    Determining whether or not an IPv6 node has moved to a new subnet is not a simple issue in IETF Mobile IPv6. In this letter, we analyze the movement detection process of IPv6 mobile nodes qualitatively and quantitatively, and present the results of our performance analysis in terms of latency caused by the process. View full abstract»

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  • Reduce chord routing latency issue in the context of IPv6

    Publication Year: 2006 , Page(s): 62 - 64
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (156 KB) |  | HTML iconHTML  

    Due to the mismatch between an overlay and its underlying physical network, the routing latency in existing DHT systems such as Chord and CAN is rather high. We note the fact that the IPv6 address hierarchical structure can aggregate route entries in Internet, and thus propose that nodes in an overlay can cluster together by taking advantage of the shared IPv6 prefix of specific length. While utilizing DHT systems themselves to store and retrieve the IPv6 prefix information, we adapt it to Chord and thus construct an improved version dubbed eChord. Analysis and simulation results confirm that eChord can significantly reduce routing latency. View full abstract»

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  • IEEE Communications Society - 2006 Board of Governors

    Publication Year: 2006 , Page(s): 65
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    Freely Available from IEEE

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Aristotle University of Thessaloniki
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