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Communications, IEE Proceedings-

Issue 4 • Date Aug 2005

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Displaying Results 1 - 20 of 20
  • Concatenated space-time trellis codes with optimal puncturing patterns

    Publication Year: 2005 , Page(s): 385 - 392
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (241 KB)  

    The performance of space-time trellis codes (STTCs) serially concatenated with convolutional codes and Bose-Chaudhuri-Hocquenghem codes is evaluated over quasistatic Rayleigh fading channels. The STTCs are used as inner codes since they provide diversity owing to their multi-antenna nature. The loss in spectral efficiency incurred due to the added redundancy from the outer codes is dealt with by constructing punctured STTCs. Optimal puncturing patterns are obtained based on the required rate of the code that provides full diversity and the best coding gain. This is performed for two-antenna, four-PSK STTCs with a varying number of transitional states. Results show low performance loss when high-state STTCs are punctured but high performance loss in a serially concatenated system. A trade-off is therefore obtained by deploying a concatenated system with a low-state punctured STTC against a high-state punctured STTC that suffers the least performance loss when punctured. View full abstract»

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  • Analysis of network error correction based on network coding

    Publication Year: 2005 , Page(s): 393 - 396
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (175 KB)  

    For network error-correcting codes based on network coding an explicit lower bound on the size of source alphabet is presented. This bound is deduced by a Gilbert-Varshamov greedy algorithm. The difficulty of constructing good error-correcting codes for networks is considered and ways of constructing good codes for small-scale networks are dealt with in detail. View full abstract»

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  • Near-optimum serial concatenation of single-parity codes with convolutional codes

    Publication Year: 2005 , Page(s): 397 - 403
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (220 KB)  

    A class of concatenated codes using convolutional codes and low-density parity check codes as component codes is proposed, extending the author's previous work. A special case is considered serial concatenation of single parity check codes as the outer code, a convolutional code with recursive systematic encoder as the inner code, separated by a random interleaver. A way to design the interleaver 'or the corresponding LDPC code' is presented to minimise the correlation between the extrinsic information. The results show that this parity concatenated code can operate within 0.45 dB of the Shannon limit. Similar to the parity concatenated codes presented in earlier work, these codes are superior in approaching the sphere packing bound (SPB), achieve near-SPB decoding can be achieved for block sizes ranging from 200 (about 0.8 dB) to 10 000 (within 0.6 dB) information bits (for a block error rate of 10-4). The improvement over previous coding schemes is 0.3-0.4 dB for block lengths more than 300 bits, and over JPL turbo codes is 0.3 dB for block lengths less than 1000 bits. A reliable error-detection method is proposed that makes this coding scheme very attractive for communications using short packets. View full abstract»

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  • Authenticated Diffie-Hellman key agreement protocol using a single cryptographic assumption

    Publication Year: 2005 , Page(s): 404 - 410
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (181 KB)  

    In modern communication systems, a popular way of providing authentication in an authenticated Diffie-Hellman key agreement protocol is to sign the result of a one-way hash function (such as MD5) of a Diffie-Hellman public key. The security of such a protocol is based on the weakest of all the cryptographic assumptions of the algorithms involved: Diffie-Hellman key distribution, digital signature and a one-way hash function. If a protocol can be constructed using one cryptographic assumption, it would be at least as secure as that with multiple assumptions. The authors propose three authenticated Diffie-Hellman key-agreement protocols, each of which is based on one cryptographic assumption. In particular, the first protocol is based on a discrete logarithm, the second on an elliptic curve and the third on RSA factoring. The main objective of the paper is to show that the security of a protocol should be assessed at the protocol level as a whole, rather than at the level of individual algorithms that are used to build the protocol. View full abstract»

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  • Convertible ring signature

    Publication Year: 2005 , Page(s): 411 - 414
    Cited by:  Papers (8)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (155 KB)  

    A ring signature scheme enables a signer to produce a signature without revealing their identity. A verifier can verify that the ring signature was made by a ring member, but cannot identify the real signer. A convertible ring signature scheme is proposed that allows the real signer to convert a ring signature into an ordinary signature by revealing secret information about the ring signature. Thus the real signer can prove the ownership of a ring signature if necessary. View full abstract»

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  • Analysis of non-data-aided carrier frequency recovery with Luise-Reggiannini estimators applied to M-PSK schemes

    Publication Year: 2005 , Page(s): 415 - 419
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (216 KB)  

    Luise and Reggiannini introduced a data-aided feedforward estimator for carrier frequency recovery in an all-digital receiver. For M-PSK as a modulation scheme, the concept is easily extended to the non-data-aided case. In this context, a closed-form solution for computation of the jitter variance is provided, which agrees with the simulation results for medium-to-high SNR values and frequency offsets representing a smaller fraction of the operational range. In the sequel, the analytical result is used for comparison purposes and parameter optimisation. View full abstract»

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  • Fast, stable simulation of power-law packet traffic using concatenated acceleration techniques

    Publication Year: 2005 , Page(s): 420 - 426
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (206 KB)  

    In recent papers a traffic aggregation (TA) technique for power-law traffic has been investigated. It has been shown that TA provides very significant acceleration with highly stable results, when simulating packet network traffic with Markovian or power-law distributed activity periods. How the well-known rare-event simulation technique RESTART (repetitive simulation trials after reaching thresholds) can be applied in conjunction with TA is investigated. Applying for the first time two combined acceleration methods it is shown that this idea provides a technique that is robust, efficient and effective, allowing stable estimates of tail probabilities faster than with either individually. The results show that concatenating these acceleration techniques can provide speedup in excess of that provided by the sum of them individually. Because TA abridges the level of complexity involved in using RESTART, using them together is simpler than just applying RESTART to the same (original) network. This combination provides a powerful tool for tackling otherwise prohibitively time-consuming simulations of the sort of power-law governed packet traffic patterns frequently reported in the recent literature. View full abstract»

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  • Survivable GMPLS networks with QoS guarantees

    Publication Year: 2005 , Page(s): 427 - 431
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (182 KB)  

    A scheme is proposed to provide multiple QoS guarantees for survivable generalised multiprotocol label switching (GMPLS) networks. The shared risk link group (SRLG) information is considered to provide failure-independent protection. Based on the problem formulation, the service level agreement (SLA) parameters, such as the expected recovery failure probability, the expected recovery time and the expected signal loss are analysed to reveal the bound of the backup path length. Under the constraint of such a backup path length limit, a heuristic algorithm is further proposed for online path configuration. The simulation results demonstrate that the heuristic algorithm provides recovery quality guaranteed backup paths with high bandwidth multiplexing gain. View full abstract»

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  • Complexity-reduced iterative MAP receiver for spatial multiplexing systems

    Publication Year: 2005 , Page(s): 432 - 438
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (231 KB)  

    A complexity-reduced iterative algorithm for joint maximum a posteriori (MAP) detection and channel estimation for spatial multiplexing systems is presented. To reduce the complexity of the MAP detection, which increases exponentially with the number of transmit antennas and the modulation order, a modified sphere decoding (SD) algorithm is proposed. It just enumerates the symbol sequences with high a priori probabilities, which fall inside a sphere centred at the received signal point. Extensive simulations demonstrate that the proposed algorithm, combined with convolutional code, reduces the complexity as compared to that of the MAP detection with moderate performance degradation. The effects of design parameters, e.g. sphere radius and the number of symbol sequences with high a priori probabilities, on the performance/complexity trade-offs are also discussed. View full abstract»

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  • Providing absolute differentiated services for optical burst switching networks: loss differentiation

    Publication Year: 2005 , Page(s): 439 - 446
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (233 KB)  

    The provision of absolute differentiated services for optical burst switching (OBS) networks based on dynamic wavelength assignment is investigated. Unlike existing quality of service (QoS) schemes, such as buffer-based and offset-time based ones, the proposed dynamic virtual lambda partitioning (DVLP) scheme does not mandate any buffer or extra offset time, but can achieve absolute service differentiation between classes. This new DVLP scheme shares wavelength resources based on several different class priorities in an efficient and QoS guaranteed manner. Furthermore, DVLP is robust: this means that each traffic class, with a loss probability conforming to the target value, continues to receive the required QoS, despite the presence of misbehaving packets, such as bursty arrival traffic. The conditions in which the DVLP scheme is feasible are stated, and the performance results are given for the proposed scheme, which effectively guarantees the target loss probability of each traffic class, both in Poisson and self-similar traffic environments. View full abstract»

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  • Channel statistical multiplexing in SDH/SONET networks

    Publication Year: 2005 , Page(s): 447 - 451
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (149 KB)  

    The new technologies of virtual concatenation, the link capacity adjustment scheme and the generic framing protocol make SDH/SONET survivable in the next-generation transport networks. However, based on synchronous time-division multiplexing, SDH/SONET only creates a private point-to-point path for a particular user that cannot be shared by other users when the path is in the idle state. Therefore it results in bandwidth inefficiency for accommodating bursty services. A new scheme called 'channel statistical multiplexing' is proposed. It is simple and practical for use when there are several data streams from the same source node to the same destination node in SDH/SONET networks. View full abstract»

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  • Iterative reconstruction-based method for clipping noise suppression in OFDM systems

    Publication Year: 2005 , Page(s): 452 - 456
    Cited by:  Papers (7)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (177 KB)  

    An iterative reconstruction-based method for suppression of clipping distortion in OFDM systems is proposed. Analysing the performance of the proposed method in Rician fading channels shows that it outperforms similar techniques, i.e. DFT-based reconstruction and iterative cancellation methods, on both BER performance and computational complexity. View full abstract»

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  • Spectrally efficient transmit diversity scheme for differentially modulated multicarrier transmissions

    Publication Year: 2005 , Page(s): 457 - 462
    Cited by:  Papers (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (174 KB)  

    Cyclic delay diversity is a simple, yet effective, transmit diversity scheme for multicarrier based transmissions employing coherent digital linear modulation schemes. It is shown that, for satisfactory operation, the scheme requires additional channel estimation overhead compared to single antenna and traditional space-time coded transmissions owing to the inherent increase in frequency selective fading. The authors analyse the additional channel estimation overhead requirement for a Hiperlan #2 style system with two transmit antennas operating in a NLOS indoor environment. The analysis shows that an additional overhead of 500% is required for the candidate system compared to a single antenna system. It is also shown that by employing differential modulation the channel estimation overhead can be eliminated with significant performance improvement compared to a system employing a practical channel estimation scheme. This novel combination, termed 'differentially modulated cyclic delay diversity', is shown to yield a highly spectral efficient, yet simple transmit diversity solution for multi-carrier transmissions. View full abstract»

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  • Optimal precoder for block transmission over frequency-selective fading channels

    Publication Year: 2005 , Page(s): 463 - 468
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (202 KB)  

    The authors consider the design of a precoder for block transmission over a frequency-selective fading channel that minimises the worst-case averaged pairwise error probability (PEP) of the maximum likelihood detector. In applications in which the transmitter does not know the channel, the scaled identity matrix is shown to be an optimal precoder for the general uncorrelated frequency-selective Rayleigh fading channel. Such precoded communication systems automatically guarantee that the maximum likelihood detector extracts full diversity and that the optimal coding gain is achieved. A comparison of the error performance of the optimal precoded system with that of other systems with unitary precoders shows that the optimal system obtains a significant SNR gain (2-4 dB). View full abstract»

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  • Suboptimal multiple-symbol differential detection of MPSK with diversity reception

    Publication Year: 2005 , Page(s): 469 - 475
    Cited by:  Papers (2)  |  Patents (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (214 KB)  

    Simon and Alouini (2001) have derived the structure of the optimal N-length differential detector for differentially encoded M-ary phase-shift keying signals, transmitted over a slow fading diversity channel. Even though there is no explicit phase estimation and compensation being performed at the receiver, it was demonstrated that as N increases, the error performance of this multiple-symbol differential detector approaches that of maximal-ratio combining (with differential encoding). Unfortunately, efficient implementation of this optimal receiver is not possible, and it exhibits a computational complexity exponential in N. The computational complexity can be reduced dramatically to N log N if the receiver first performs coherent combining of the received multichannel baseband signals, followed by single-channel multiple-symbol differential detection (MSDD). A coherent combiner is introduced that is capable of cophasing the multichannel signals without violating the fundamental nature of differential detection, i.e. to avoid explicit phase estimation. The proposed suboptimal coherent combining MSDD (CC-MSDD) receiver essentially consists of two differential detectors: one operating across diversity branches, and one operating across time. Owing to the dramatic reduction in complexity, a very large observation window is used with the CC-MSDD. With window size N=64, the asymptotic performance of the CC-MSDD is only 0.5 dB away from maximal-ratio combining with differential encoding. This translates into a 1.5 dB gain in power efficiency over conventional equal gain combining for a second-order diversity system. The authors also investigate suboptimal receivers which perform selection combining, followed by single-channel MSDD. Although these selection combining MSDD receivers provide less than satisfactory performance in stand-alone mode, they are promising candidates for the initial detector in blind, iterative coherent detectors that operate on the principle of decision feedback. View full abstract»

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  • Spread-spectrum sequence estimation for DSSS signal in non-cooperative communication systems

    Publication Year: 2005 , Page(s): 476 - 480
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (187 KB)  

    An innovative and effective algorithm is proposed to estimate the spread-spectrum sequence of a direct spread-spectrum sequence (DSSS) signal in non-cooperative communication systems. In particular, a measurement function, which is used for sequence synchronisation, and a detection statistic, which is for sequence estimation chip by chip, are developed based on the idea of correlation. Only linear complex addition and multiplication are required for the implementation of the algorithm. Theoretical analysis and computer simulations verify the effectiveness of the algorithm. View full abstract»

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  • Sufficient statistic and reduced-dimensionality equivalent symbol-space model for frequency-flat MIMO channel with spatially nonuniform delay

    Publication Year: 2005 , Page(s): 481 - 488
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (220 KB)  

    An equivalent symbol-space discrete channel model for a frequency-flat block-fading MIMO spatial diversity channel with spatially nonuniform path delays is derived. A general nonlinear modulation scheme is assumed by allowing channel symbols to be multidimensional per one antenna. The sufficient symbol-spaced statistic dimensionality is shown to be a product of transmit, receive and symbol dimensions unlike for a traditional frequency-flat MIMO model where the dimension is a product of receive and symbol dimensions. The traditional model is valid only for spatially uniform delays. It is shown that the spatially nonuniform path delays cause spatial interbranch interference (IBI). A reduced-dimensionality equivalent system is introduced. The spatial IBI can be reduced by using a linear minimum mean square error spatial-temporal preprocessor (equaliser). Numerical results show that this dimensionality-reducing preprocessing significantly lowers the residual self-noise mean square in comparison with the case of deliberately ignoring the higher dimensionality of the sufficient statistic. The spatial processing is found to be the essential one; additional temporal processing has only a small impact on the residual self-noise. View full abstract»

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  • MIMO frequency-selective channels with multiple-frequency offsets: estimation and detection techniques

    Publication Year: 2005 , Page(s): 489 - 494
    Cited by:  Papers (17)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (191 KB)  

    Channel gains and frequency offsets are estimated in a multiple input and multiple output (MIMO) scenario, allowing for more than one path between the transmit and the receive antennas, with each path possibly having a different frequency offset. Such a scenario may arise due to Doppler shift associated with various multipaths. Here, the general case is examined and an approximate maximum likelihood (AML) estimator is derived by exploiting the correlation property of the pilot signal. The AML estimator can be written as the sum of nTL one-dimensional maximisations, where nT is the number of transmit antennas and L is the total number of paths. The proposed estimator is validated by comparing the results with the Crame´r-Rao lower bound (CRLB). Further, a minimum mean square error recursive (MMSER) equaliser is proposed for the considered scenario. Finally, the performance of the MMSER equaliser is compared with the equaliser not accounting for frequency offsets. View full abstract»

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  • Multiple antenna options for high data rate CDMA systems

    Publication Year: 2005 , Page(s): 495 - 503
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (263 KB)  

    1xEV-DO (1xEVolution-Data Only) is a method for transmission of wireless packet data at high rates which is based on code division multiple access (CDMA) technology. Adaptive modulation and coding is used together with proportional fairness scheduling to take full advantage of the channels between the base stations and mobile stations when they are at their best. Methods such as receive antenna diversity and multiple input multiple output (MIMO) have the potential to improve the performance of such a system. A model which simulates an 1xEV-DO network with multiple transmit and receive antennas has been developed to investigate this. Results are given showing how the throughput varies with the number of users per cell for different numbers of transmit and receive antennas. The performance of MMSE (minimum mean square error) and MRC (maximal ratio combining) algorithms are also investigated. The effects of introducing multiple paths and Rayleigh and Rician fading are compared. Simulation results for multiple transmit and receive antennas are compared with the channel capacity predicted by the Shannon capacity equation. View full abstract»

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  • Performance analysis of high-speed packet data in an integrated voice/data CDMA system

    Publication Year: 2005 , Page(s): 504 - 510
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (199 KB)  

    In order to support high data-rate service in an integrated CDMA system, it is required to allocate resources for data users in the consideration of high spectral efficiency. The author analyses the performance of a simultaneous resource allocation (SRA) scheme and a dedicated resource allocation (DRA) scheme in the reverse link of an integrated voice/data CDMA system. In the DRA scheme, the throughput of data users can be maximised when one user among data users is allowed to transmit information at any given time. Using the DRA scheme, resources for data users are allocated with high spectral efficiency. To apply this scheme to an integrated voice/data CDMA system, resources are first allocated to voice users and then residual resources are allocated to data users based on the throughput maximisation strategy. For a more practical approach, the transmission power of the mobile station (MS) is assumed to be limited. Owing to this assumption, the performance of SRA and DRA schemes is varied according to the location of the MS. The performance is also shown under perfect power control and imperfect power control. In order to verify the analysis results, the simulation was performed under the same environment. Simulation and analysis results show that the DRA scheme has higher throughput than the SRA scheme under the conditions that the mobile is located in a limited cell coverage and the variation of Eb/N0 is minimised. View full abstract»

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