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Communications Letters, IEEE

Issue 3 • Date March 2005

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Displaying Results 1 - 25 of 36
  • Non-dominance in QoS routing: an implementational perspective

    Publication Year: 2005 , Page(s): 267 - 269
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (581 KB) |  | HTML iconHTML  

    In QoS routing, the problem of finding paths subject to multiple constraints, is NP-complete. Therefore, efficient search-space reducing techniques are needed. The concept of dominance is such a technique. Contrary to the popularity of using dominance verification, the dominance implementation issues are hardly studied. This letter provides such a study. View full abstract»

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  • A hierarchical FLP model for broadband networks

    Publication Year: 2005 , Page(s): 282 - 284
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (517 KB) |  | HTML iconHTML  

    In next generation networks (NGNs), broadband networks include various layer 2 and layer 3 devices, e.g., Ethernet switches and routers. When deploying broadband networks, how the devices are appropriately located is an important issue. The device location problem could be treated as a hierarchical facility location problem (FLP). We present detailed mathematical models for the hierarchical FLP encountered in broadband network planning. Through experiments based on real networks, we demonstrate that the linearity of the model could significantly improve both the computational complexity and the optimality. View full abstract»

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  • Delta compression with fixed-length substring coding for fast content download

    Publication Year: 2005 , Page(s): 243 - 245
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (605 KB) |  | HTML iconHTML  

    Delta compression algorithms take advantage of the statistical correlations between different files or packets so that common sequences between two files can be encoded using a copy reference. Delta compression forms the core of fast and efficient content download. We present for the first time, a theoretical framework for delta compression based on information theory and Markov models, including insights into the compression bounds. We also simulated and implemented a generic delta compression scheme and demonstrated its realtime and non realtime performance by applying the scheme on binary data. View full abstract»

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  • An analytical model for reverse link rate control in cdma2000 1xEV-DO systems

    Publication Year: 2005 , Page(s): 270 - 272
    Cited by:  Papers (4)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (555 KB) |  | HTML iconHTML  

    The cdma2000 1xEV-DO standard has a distributed rate control on the reverse link. If a mobile has data to transmit, it determines the data rate of the next frame in response to a reverse activity bit broadcast by the base station. This paper proposes an analytical framework for the 1xEV-DO rate control by adopting the noise rise as the reverse traffic load, and by modeling the rate control as a discrete Markov process. We validate the proposed model through a simulation, in which 1xEV-DO reverse power control is applied to a Rayleigh fading channel. In addition, we illustrate the operation principle of the 1xEV-DO rate control based on the data rate distribution of mobiles. View full abstract»

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  • Trellis source codes based on linear congruential recursions

    Publication Year: 2005 , Page(s): 198 - 200
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (490 KB) |  | HTML iconHTML  

    We evaluate a new class of rate-distortion codes based on simple linear congruential recursions. Codes are demonstrated for the memoryless uniform, Gaussian, Laplacian and gamma sources, whose performance often exceeds that so far reported in the literature, including that for TCQ codes. At a source coding rate of one bit per sample, the performance at 512 states is 0.24 dB from the Shannon limit for the memoryless Gaussian source. View full abstract»

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  • Bit-interleaved turbo-coded modulation using shaping coding

    Publication Year: 2005 , Page(s): 246 - 248
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (580 KB) |  | HTML iconHTML  

    We present a new and simple method for combining constellation shaping and bit-interleaved turbo-coded modulation (BITCM). By considering the example of a 3-bit/dim 16-PAM BITCM, it is shown that this technique can provide shaping gains of 0.64 dB, and error performance within 1.51 dB of the continuous-input channel capacity limit is achieved. View full abstract»

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  • Heterogeneous bursty traffic dispersion over multiple server clusters

    Publication Year: 2005 , Page(s): 261 - 263
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (477 KB) |  | HTML iconHTML  

    This letter presents performance analysis of multiple subnets, each representing a cluster of computing server nodes, that are introduced with non-uniformly distributed bursty packet arrivals. In particular, we study the case of a multi-state Markov-modulated arrival process, heterogeneously dispersed among designated queues. Cluster processing is modeled by employing a batch service discipline. The probability generating functions of the interarrival times distributions are utilized to derive closed-form expressions for each of the queue size distributions. View full abstract»

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  • Exact analysis of bit error probability for trellis coded QPSK

    Publication Year: 2005 , Page(s): 237 - 239
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (609 KB) |  | HTML iconHTML  

    This letter presents an exact analysis of bit error probability for trellis coded modulation with soft decision Viterbi decoding. It is shown that this analytical technique is effective for low signal-to-noise power ratio where bounds are useless. The extension to asymmetric constellation is also investigated. View full abstract»

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  • Average packet delay of CSMA/CA with finite user population

    Publication Year: 2005 , Page(s): 273 - 275
    Cited by:  Papers (8)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (617 KB) |  | HTML iconHTML  

    In this paper, a simple closed form solution for the packet delays of the basic carrier sense multiple access with collision avoidance system is derived. Simulation results confirm the applicability and correctness of the derivation. View full abstract»

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  • Space-time block codes from cyclic design

    Publication Year: 2005 , Page(s): 231 - 233
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (540 KB) |  | HTML iconHTML  

    It has been proved that full-rate complex orthogonal space-time block codes do not exist for systems with more than two transmit antennas. In this paper, we present a space-time block coding scheme based on cyclic design. The proposed codes provide full rate and full diversity for quaternary phase shift keying (QPSK) symbols in systems with three or four transmit antennas. View full abstract»

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  • A simple, intuitive expression for the BER of a jointly optimal single cochannel interferer BPSK receiver

    Publication Year: 2005 , Page(s): 201 - 203
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (555 KB) |  | HTML iconHTML  

    A simple and intuitive new expression for the bit error rate (BER) performance of a synchronous jointly optimum receiver is derived. The receiver is used to detect a binary phase-shift keying (BPSK) signal in the presence of an identical cochannel interferer and additive white Gaussian noise (AWGN). The new expression separates into the BER of BPSK in AWGN plus a term due to the interference. The term due to interference approaches zero when the interference power or its correlation with the desired signal tends to zero, as expected. View full abstract»

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  • Outage and BER of MRC diversity in bandlimited micro-cellular systems with CCI

    Publication Year: 2005 , Page(s): 207 - 209
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (607 KB) |  | HTML iconHTML  

    Maximal ratio combining for bandlimited BPSK in micro-cellular systems with cochannel interference is considered. A Nakagami/Rayleigh fading model is assumed. Spectrum raised-cosine and Beaulieu-Tan-Damen pulse shapes are employed. Exact closed-form expressions for outage probability with equal and different interferer powers are derived. An average bit error rate approximation is derived using a Gaussian assumption for the cochannel interference. Monte-Carlo simulation is used to validate the Gaussian assumption. The results are valid for arbitrary diversity order and desired user fading parameter. Slow flat fading, asynchronous timing and independent fading gains are assumed. View full abstract»

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  • A simple convergence comparison of Gallager codes under two message-passing schedules

    Publication Year: 2005 , Page(s): 249 - 251
    Cited by:  Papers (5)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (633 KB) |  | HTML iconHTML  

    The convergence rate of iterative decoding of Gallager codes on the additive white Gaussian noise (AWGN) channel using the sum-product algorithm (SPA) under the flooding schedule (FS) is compared with that under the turbo-decoding schedule (TDS). Analyses using extrinsic information transfer (EXIT) charts show that TDS exhibits a much faster convergence behavior than FS. View full abstract»

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  • Breaking an improved password authenticated key exchange protocol for imbalanced wireless networks

    Publication Year: 2005 , Page(s): 276 - 278
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (463 KB) |  | HTML iconHTML  

    Yeh et al. (2003) proposed a password-authenticated key exchange protocol which is claimed to be an improvement of Zhu et al.'s (2002) password-authenticated key exchange protocol to defend against the so-called undetectable on-line password guessing attack. In this paper, we show that the improved protocol of Yeh et al. is insecure. In fact, an adversary can recover the password, off-line, by executing a single run of the improved protocol. We also point out the misconception of the so-called undetectable on-line password guessing attack. View full abstract»

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  • A novel long-span traffic predictor for real-time VBR videos via ρ-domain rate model

    Publication Year: 2005 , Page(s): 279 - 281
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (610 KB) |  | HTML iconHTML  

    To predict the traffic of frames that may be far from the current frame, this letter extends the use of the ρ-domain rate model from macroblock-based source rate control to frame-based long-span traffic prediction. Moreover, this work enhances the linearity and convergence speed of ρ-domain frame-based rate function by adding a parameter that is the number of nonzero motion vectors. Simulation results reveal that the proposed predictor can significantly lower the prediction error compared with two conventional LMS methods. More importantly, the process of the proposed predictor is unique but simple for different video contents and prediction spans. View full abstract»

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  • A closed form solution of Bernoullian two-classes priority queue

    Publication Year: 2005 , Page(s): 264 - 266
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (608 KB) |  | HTML iconHTML  

    We investigate the effect of a two-priority policy when serving slotted traffic arriving with Bernoulli statistics. We are able to give explicit closed-form expressions for the distribution of the lengths of the high- and low-priority queue. View full abstract»

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  • Generalization of Tanner's minimum distance bounds for LDPC codes

    Publication Year: 2005 , Page(s): 240 - 242
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (528 KB) |  | HTML iconHTML  

    Tanner derived minimum distance bounds of regular codes in terms of the eigenvalues of the adjacency matrix by using some graphical analysis on the associated graph of the code. In this letter, we generalize Tanner's results by deriving a bit-oriented bound and a parity-oriented bound on the minimum distances of both regular and block-wise irregular LDPC codes. View full abstract»

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  • Probability of an arbitrary wedge-shaped region of the MPSK system in the presence of quadrature error

    Publication Year: 2005 , Page(s): 196 - 197
    Cited by:  Papers (1)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (494 KB) |  | HTML iconHTML  

    The paper presents a new and simple expression for computing the probability on an arbitrary wedge-shaped region between two different phase angles when the signal vector is perturbed by two-dimensional Gaussian noise in the presence of a quadrature error. The two-dimensional Gaussian Q-function is used to characterize the expression. The expression can be very useful for computing the analytical error probability of the M-ary phase shift keying system operating in various channel environments. View full abstract»

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  • Simple reconfigurable low-density parity-check codes

    Publication Year: 2005 , Page(s): 258 - 260
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (563 KB) |  | HTML iconHTML  

    Low-density parity-check codes (LDPCC) have been recently investigated as a possible solution for high data rate applications, for both space and terrestrial wireless communications. A main issue is the research of low complexity encoding and decoding schemes. In this letter we present a class of reconfigurable LDPCC characterized by low encoding and decoding complexity: we call them generalized irregular repeat-accumulate (GeIRA) codes. View full abstract»

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  • Clustering coefficient of wireless ad hoc networks and the quantity of hidden terminals

    Publication Year: 2005 , Page(s): 234 - 236
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (631 KB) |  | HTML iconHTML  

    The clustering coefficient has been proposed to characterize complex networks. Hidden terminals may degrade the performance of the CSMA (carrier sense multiple access) protocol. This letter computes analytically the clustering coefficient and the quantity of hidden terminals for ad hoc networks. The former turns out to be a constant and the latter is proportional to n3 p2, where n is the number of nodes and p is the link probability. The connection between them has been established, and simulation results confirm our analytical work. View full abstract»

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  • Intra-superframe power management for IEEE 802.15.3 WPAN

    Publication Year: 2005 , Page(s): 228 - 230
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (515 KB) |  | HTML iconHTML  

    Power management (PM) is critical for the portable devices in IEEE 802.15.3 wireless personal area networks (WPAN). Due to the property of TDMA based MAC of 802.15.3, one of the key issues for PM is to schedule the order of the multiple streams among multiple users to minimize the total wakeup times. In this paper, we reveal that this PM problem is in general a Hamilton path problem. With the aid of graph theory, we derive the lower bound and upper bound for the minimum wakeup times. Then, an efficient MDS (min-degree searching) algorithm is proposed to find the suboptimal order. The simulation results show that the MDS algorithm is usually near-optimal and can actually achieve the lower bound in most cases and performs much better than the existing approach. View full abstract»

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  • Extended tail-biting schemes for turbo codes

    Publication Year: 2005 , Page(s): 252 - 254
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (529 KB) |  | HTML iconHTML  

    In this letter, we investigate the problem of using tailbiting recursive systematic convolutional (RSC) codes in turbo codes. Tailbiting is not always possible for a given RSC code with fixed length. We propose an extended tailbiting method for RSC codes and compare it with another extension method proposed by Van Stralen, et al. (IEE Electron. Lett., vol. 35, pp. 1461-1462, 1999). Several schemes using these extended tailbiting RSC codes in turbo code systems are developed and compared. View full abstract»

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  • Statistical characterization of the service time in saturated IEEE 802.11 networks

    Publication Year: 2005 , Page(s): 225 - 227
    Cited by:  Papers (15)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (632 KB) |  | HTML iconHTML  

    In this paper, we propose an analytical model for the service time in saturated IEEE 802.11 DCF networks. We derive a closed-form probability generating function for the packet service time of a cluster of IEEE 802.11 terminals, both for the RTC/CTS and the basic access mode. The probability generating function is inverted by numerical methods, providing the probability distribution function of the service time. Interestingly, it catches certain features of the DCF service time, which cannot be revealed with the second order analysis known in the literature. Finally, this analytical model is validated by means of extensive simulation outcomes. View full abstract»

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  • Peer-to-peer middleware for bandwidth allocation in sensor networks

    Publication Year: 2005 , Page(s): 285 - 287
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (525 KB) |  | HTML iconHTML  

    In sensor networks, both bandwidth allocation and bandwidth-on-demand (BoD) schemes may be adopted, on top of a generic multiple access protocol, for the purpose of differentiating various categories of devices that produce non-homogeneous data flows. At the same time, the modern Internet exhibits a trend toward an even more distributed architecture approach; decentralized architectures are gaining more and more popularity, and middleware solutions are widely adopted. Among them, the peer-to-peer (p2p) networking paradigm allows a redundant architecture that reacts well against failure to be obtained. Starting from p2p principles, the paper introduces a novel middleware-based algorithm for configuring and managing bandwidth in a sensor network. View full abstract»

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  • Implications of power control and successive interference cancellation on indoor DS-CDMA system deployment and performance

    Publication Year: 2005 , Page(s): 204 - 206
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (545 KB) |  | HTML iconHTML  

    We investigate the optimal combination of power control and successive interference cancellation to yield performance gains in a multi-floor indoor DS-CDMA system. Using measured indoor propagation data and a Monte Carlo simulation, it is shown that the performance gains achieved are significantly influenced by the base station deployment strategy chosen. View full abstract»

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George K. Karagiannidis
Aristotle University of Thessaloniki
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