Online ISSN
1751-8636
Print ISSN
1751-8628
IET Communications
Volume 5, Issue 4, 4 March 2011
Volumes & issues:
Volume 5, Issue 4
4 March 2011
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- Author(s): G. Marchetto ; M.P. Manzillo ; L. Torrero ; L. Ciminiera ; F. Risso
- Source: IET Communications, Volume 5, Issue 4, p. 409 –417
- DOI: 10.1049/iet-com.2010.0624
- Type: Article
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The wide diffusion of network address translators (NATs) (and, in some respect, firewalls) may prevent some applications that require direct end-to-end connectivity (e.g. real-time media) from being able to connect to the remote party. Although the solutions currently adopted rely on centralised nodes as third party relays, the distributed connectivity service (DISCOS) architecture has been recently proposed and aims at distributing such functionalities across a peer-to-peer (P2P) overlay. The original study presented some performance characteristics of the overlay, but the ability to resist to both failures and attacks was not taken into consideration. This study illustrates the robustness feature of the DISCOS overlay and suggests some minor modifications to the original mechanisms, in order to improve the overall robustness. The key component of DISCOS is its dynamic scale-free topology. Hence, the study also extends the existing literature concerning the robustness of scale-free networks, which considers only static graphs. - Author(s): A. Basyouni ; W. Hamouda ; A. Youssef
- Source: IET Communications, Volume 5, Issue 4, p. 418 –424
- DOI: 10.1049/iet-com.2010.0035
- Type: Article
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Cooperative diversity is a powerful tool that can be used to improve the performance of wireless networks. The use of directional antennas has also shown to offer an effective way for efficient bandwidth utilisation. In this study, the authors investigate the effect of both the transmission power and the number of cooperative relays on the maximum achievable throughput in energy-constrained cooperative ad hoc networks with directional antennas. In particular, the authors develop an analytical model for the network throughput in terms of the number of cooperative relays and nodes' transmission power. Using our model, we determine the optimum number of relays for a given transmission power, and the optimum transmission power for a given number of relays. Furthermore, we propose a cooperative relaying protocol that utilises the above optimal values to maximise the achievable throughout in such energy-constrained networks. The obtained analytical results as well as the performance of the proposed protocol are validated by simulations over a Rayleigh fading channel. - Author(s): F.S. Al-kamali ; M.I. Dessouky ; B.M. Sallam ; F. Shawki ; F.E. Abd El-Samie
- Source: IET Communications, Volume 5, Issue 4, p. 425 –433
- DOI: 10.1049/iet-com.2010.0135
- Type: Article
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Similar to the orthogonal frequency division multiple access (OFDMA) system, the single-carrier frequency division multiple access (SC-FDMA) system also suffers from frequency mismatches between the transmitter and the receiver. As a result, in this system, the carrier frequency offsets (CFOs) disrupt the orthogonality between subcarriers and give rise to inter-carrier interference (ICI) and multiple access interference (MAI) among users. The authors present a new minimum mean square error (MMSE) equaliser, which jointly performs equalisation and carrier frequency offsets (CFOs) compensation. The mathematical expression of this equaliser has been derived taking into account the MAI and the channel noise. A low complexity implementation of the proposed equalisation scheme using a banded matrix approximation is presented here. From the obtained simulation results, the proposed equalisation scheme is able to enhance the performance of the SC-FDMA system, even in the presence of estimation errors. - Author(s): C.T. Liu ; H. Huo ; T. Fang ; D.R. Li
- Source: IET Communications, Volume 5, Issue 4, p. 434 –442
- DOI: 10.1049/iet-com.2009.0746
- Type: Article
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Wireless sensor networks (WSNs) can implement complicated tasks through collaboration among multiple sensor nodes. The low-cost sensors in WSNs often generate noisy and even faulty measurements, which will degrade the network performance. Therefore developing collaborative signal processing (CSP) algorithms that has high fault tolerance ability is necessary for the increasingly deployed WSNs. In this study, the authors propose a novel fault tolerant fusion scheme to implement reliable vehicle classification by integrating fault detection and correction with a spatio-temporal fusion structure. Sensor faults are detected at the fusion centre and then the fault detection results are fed back to the local sensors to update subsequent classification results. A Dempster–Shafer theory based fault correction strategy is devised to utilise the fusion centre feedback. Simulation results demonstrate that the proposed scheme ensures more than 95% of the classification results to be correct when no larger than 30% of the sensors are faulty and the scheme achieves improved fault detection rate and false alarm rate than the optimum threshold Bayesian fault detection scheme. - Author(s): S. Salimi ; M. Salmasizadeh ; M.R. Aref
- Source: IET Communications, Volume 5, Issue 4, p. 443 –455
- DOI: 10.1049/iet-com.2009.0777
- Type: Article
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A source model for secret key generation between terminals is considered. Two users, namely users 1 and 2, at one side communicate with another user, namely user 3, while at the other side via a public channel where three users can observe i.i.d. outputs of correlated sources. Each of users 1 and 2 intends to share a secret key with user 3 where user 1 acts as a wiretapper for user 2 and vice versa. In this model, two situations are considered: communication from users 1 and 2 to user 3 (the forward key strategy) and from user 3 to users 1 and 2 (the backward key strategy). In both situations, the goal is sharing a secret key between user 1 and user 3 while leaking no effective information about that key to user 2, and simultaneously, sharing another secret key between user 2 and user 3 while leaking no effective information about the latter key to user 1. This model is motivated by wireless communications when considering user 3 as a base station and users 1 and 2 as network users. For both the forward and backward key strategies, inner and outer bounds of secret key capacity regions are derived. In special situations where one of users 1 and 2 is only interested in wiretapping and not key sharing, the results agree with that of Ahlswede and Csiszar. Also, the authors investigate some special cases in which the inner bound coincides with the outer bound and secret key capacity region is deduced. - Author(s): A. Jamshidi
- Source: IET Communications, Volume 5, Issue 4, p. 456 –466
- DOI: 10.1049/iet-com.2010.0031
- Type: Article
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Owing to multiple access capability, low probability of intercept and immunity against inter symbol interference (ISI) caused by multipath propagation, direct sequence spread spectrum (DSSS) techniques have been utilised in both underwater acoustic (UWA) communication networks and reliable point-to-point communications. To overcome the severe impact of ISI in the UWA channels, we propose a novel multiple pseudo noise (PN) sequence DSSS scheme and analyse its performance in sparse time varying UWA channels. Analytical and simulation results show that using a few PN sequences can remove most of the multipath induced ISI. To further alleviate the ISI effect, we propose a simple ISI reduction algorithm. Numerical results show that our proposed algorithm along with the proposed DSSS scheme can effectively mitigates the effect of remaining ISI, especially in sparse multipath channels. - Author(s): S.H. Hong and W.-S. Song
- Source: IET Communications, Volume 5, Issue 4, p. 467 –475
- DOI: 10.1049/iet-com.2010.0041
- Type: Article
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Digital communication networks are a core technology in advanced building automation systems. Building automation and control network (BACnet), a data communication protocol designed specifically for building automation and control systems, uses the master–slave/token-passing (MS/TP) protocol as one of its field-level networks. Previously, the authors introduced a basic concept of bandwidth allocation for MS/TP to improve its real-time communication capability. In this study, the authors developed a communication module that implements the proposed scheme, and used it in an experimental model to examine the validity of the bandwidth allocation scheme for MS/TP. Experimental results show that the modified MS/TP protocol satisfies the requirements for real-time communications using cyclic and life-safety messages in BACnet communication services. - Author(s): G. Fumat ; P. Chargé ; A. Zoubir ; D. Fournier-Prunaret
- Source: IET Communications, Volume 5, Issue 4, p. 476 –483
- DOI: 10.1049/iet-com.2010.0032
- Type: Article
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Transform domain communication systems (TDCSs) is a technology that avoids frequency underutilisation. Its bit error rate (BER) performance has been well studied until now, but it is still unknown what is the maximum spectrum efficiency one can expect. Focusing on the multidimensional property of the system, the authors show the reachable BER and spectral efficiency they can obtain for any TDCS. Through this article, the authors provide guidelines to ensure that the spectral efficiency is maximised, whereas the BER is minimised. Previous contributions using TDCSs are studied with regard to their dimensionality and they show how their BER and spectral efficiency can be improved. - Author(s): R. Fa and R.C. de Lamare
- Source: IET Communications, Volume 5, Issue 4, p. 484 –494
- DOI: 10.1049/iet-com.2009.0843
- Type: Article
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In this study, the authors propose a novel successive interference cancellation (SIC) strategy for multiple-input multiple-output spatial multiplexing systems based on a structure with multiple interference cancellation branches. The proposed multi-branch SIC (MB-SIC) structure employs multiple SIC schemes in parallel and each branch detects the signal according to its respective ordering pattern. By selecting the branch which yields the estimates with the best performance according to the selection rule, the MB-SIC detector, therefore, achieves higher detection diversity. The authors consider three selection rules for the proposed detector, namely, the maximum likelihood (ML), the minimum mean square error and the constant modulus criteria. An efficient adaptive receiver is developed to update the filter weight vectors and estimate the channel using the recursive least squares algorithm. Furthermore a bit error probability performance analysis is carried out. The simulation results reveal that the authors' scheme successfully mitigates the error propagation and approaches the performance of the optimal ML detector, while requiring a significantly lower complexity than the ML and sphere decoder detectors. - Author(s): H. Zhou and P. Xiao
- Source: IET Communications, Volume 5, Issue 4, p. 495 –504
- DOI: 10.1049/iet-com.2009.0566
- Type: Article
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The authors propose some robust adaptive multiuser detection schemes for direct-sequence code-division multiple-access multipath frequency-selective fading channels. Multiple access interference (MAI) and intersymbol interference (ISI) are presented in an identical format using expanded signal subspace, which facilitates multiuser detection in a symbol-by-symbol fashion. This study contributes to the theoretical aspect of adaptive multiuser detection by proving that the optimum linear multiuser detectors that achieve maximum signal-to-interference-plus-noise ratio (SINR) must exist in the signal subspace, and the theoretic SINR upper bound is also derived. Another contribution of this study is to propose the design of multiuser detectors in an expanded signal subspace, and introduce subspace estimation and Kalman filtering algorithms for their adaptive implementation. To robustify the adaptive detectors against subspace estimation and channel estimation errors, a modified projection approximation subspace tracking (PAST) algorithm is proposed for subspace tracking. It is demonstrated by simulations that these adaptive detectors effectively suppress both MAI and ISI and converge to the optimum SINR. They are robust against subspace estimation errors and channel estimation errors compared to the conventional Wiener minimum mean square error (MMSE) detector. - Author(s): B.M. Heravi ; S.R. Kariyawasam ; G. Vongas ; B. Honary
- Source: IET Communications, Volume 5, Issue 4, p. 505 –511
- DOI: 10.1049/iet-com.2010.0201
- Type: Article
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A switchable-rate quasi-cyclic low-density parity-check (QC-LDPC) coding scheme has been proposed for integration within the legacy and next-generation high-frequency internet protocol (HF-IP) systems. The novelty in this work is based upon using a class of switchable-rate short-block-length (<1500 bits) QC-LDPC codes for the HF fading channel modelled by the ITU-R F.1487 for all latitudes and conditions. The QC-LDPC codes are constructed using a switchable-rate approach based on finite fields which provides the ability to switch among three rates to combat varying channel conditions using a single encoder/decoder structure. The proposed structure enables low-complexity implementation of the low-density parity-check encoder/decoder for use within the existing data link (DL) layer of the standardisation agreement (STANAG) 5066 profile. The performance of the proposed scheme has been evaluated comprehensively for all the HF channel conditions and latitudes. A comparison between the proposed and the current coding scheme in HF-IP systems (based on convolutional coding) shows an improvement in error-rate performance. - Author(s): A. Bhise and P.D. Vyavahare
- Source: IET Communications, Volume 5, Issue 4, p. 512 –518
- DOI: 10.1049/iet-com.2009.0611
- Type: Article
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Turbo convolutional codes (TCC) are excellent error correcting codes for wireless channels. However, TCC decoders require large decoding complexity. Moreover, complexity of TCC decoder does not reduce even if puncturing is used to change the coding rate. Modified turbo codes require lower decoding complexity than TCC as they use multiple concatenations of simple block codes and convolutional codes. Recently, a class of modified turbo codes called low complexity hybrid turbo codes (LCHTC) and improved low complexity hybrid turbo codes (ILCHTC) have been proposed. It has been shown that LCHTC and ILCHTC achieve bit error rate (BER) which is comparable to TCC and have much lower decoding complexity. Simulation results show that BER performance of ILCHTC is better than that of LCHTC. Rate-1/3 ILCHTC achieve BER of 10−5 at bit energy-to-noise ratio (Eb/N0) of 1.9 dB, which is 0.4 dB higher than Eb/N0 for TCC adopted by third generation partnership project (3GPP). Moreover, ILCHTC and LCHTC decoders require half the number of computations as compared to those required for TCC decoder. In this study, union-bound analysis of ILCHTC is presented to investigate BER performance<10−6. For large interleaver lengths, analysis of theoretical union bound requires numerous computations. Therefore approximate analysis of union bound is derived from theoretical union bound. It is shown that the analysis of approximate union bound achieves reasonable accuracy. Moreover, approximate union bound can be evaluated with significantly less computational complexity than the theoretical union bound. - Author(s): J. Wang ; S. Zhang ; C. Maple
- Source: IET Communications, Volume 5, Issue 4, p. 519 –533
- DOI: 10.1049/iet-com.2010.0006
- Type: Article
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Synchronous bandwidth, defined as the maximum time a node is allowed to send its synchronous messages while holding the token, is a sensitive parameter for deadline guarantees of synchronous messages in a timed token network. In order to offer such guarantees, synchronous bandwidth has to be allocated carefully. The allocation of synchronous bandwidths to a general synchronous message set with the minimum message deadline (Dmin) larger than the target token rotation time is studied. A new approach for allocating synchronous bandwidth, which can be easily implemented in practice, is proposed. It is demonstrated, through simulations and numerical examples, that the proposed approach performs better than any of previously proposed local synchronous bandwidth allocation schemes, in terms of its ability in guaranteeing hard real-time traffic. - Author(s): Z. Mei ; Z. Yang ; X. Li ; L. Wu
- Source: IET Communications, Volume 5, Issue 4, p. 534 –541
- DOI: 10.1049/iet-com.2010.0294
- Type: Article
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The authors investigate the performance of the probabilistic data association (PDA) detector in a cooperative system that consists of a source, a relay and a destination, which are all multiantenna nodes. Taking advantage of the soft information provided by the PDA detector at the relay, the authors present a relaying scheme in light of which the relay can just transmit signals to the destination under the condition of having high detection reliability. Characterised by the means on how to exploit the information provided by both the source and the relay at the destination, two detectors named as combing PDA (C-PDA) and iterative PDA (I-PDA) are developed, respectively. C-PDA adopts one PDA detector to retrieve the transmit signals by combining the received signals from the source and the relay. I-PDA employs two concatenated PDA detectors to perform detection with respect to the received signals from the source and the relay, respectively. Just as in turbo decoding, soft information is iteratively exchanged between these two concatenated PDA detectors to enhance the performance of I-PDA. Simulation results have shown that significant performance gains can be achieved by both C-PDA and I-PDA over the conventional zero-forcing detector. - Author(s): T.-Y. Wu and W.-F. Weng
- Source: IET Communications, Volume 5, Issue 4, p. 542 –553
- DOI: 10.1049/iet-com.2010.0195
- Type: Article
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Wireless access in vehicular environments (WAVE) can offer service to improve traffic safety and efficiency, and to reduce vehicle pollution. Compared with handheld devices, the chief terminals in vehicular environments, vehicles, have higher mobility. Thus, it can be anticipated that in such environments, the terminal devices may often move from one WAVE mode basic service set (WBSS) to another to exchange data and its probability for the handoff to occur is undoubtedly higher than handheld terminal devices. However, without taking high mobility into consideration, traditional IEEE 802.11 wireless transmissions were insufficient under acute moves. Furthermore, vehicular communications usually take place outdoors and the transmission quality might be influenced by other factors, like the weather. Based on different vehicular environments, this paper probes into the handoff and proposes to establish the geographical fingerprint by artificial neural network (ANN) and adjust the transmitted power of access points (APs) according to the weathers to maintain the service region and signal strength. By the measurements in advance, the handoff points can be established to reduce the handoff delay and the suitable handoff points be adjusted in accordance with vehicle speed. - Author(s): H. Nishimura ; M. Inamori ; Y. Sanada ; M. Ghavami
- Source: IET Communications, Volume 5, Issue 4, p. 554 –562
- DOI: 10.1049/iet-com.2010.0693
- Type: Article
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To achieve diversity with a single antenna, a fractional sampling (FS) scheme in OFDM has been proposed. FS achieves path diversity with a higher sampling rate and multiple demodulation branches. In the previous literatures for FS, the sampling interval is fixed even though the initial phase selection of the sampling has been investigated. The fixed sampling interval limits the diversity gain through FS. Thus, in this study, a non-uniform sampling point selection scheme according to the frequency response of a channel is proposed. Numerical results through computer simulation show that the proposed scheme improves the BER performance by about 2 dB when the number of the demodulation branches is 2. While the proposed scheme further improves bit error rate (BER) performance it requires a larger rate and more computational complexity for the selection of the sampling points. Therefore the complexity reduction for the sampling point selection is also investigated. The complexity reduction scheme eliminates the specific sets of the sampling points and reduces the computational complexity of the sampling point selection for the proposed scheme by a factor of 2. Computer simulation also shows that the low complexity version of the proposed scheme even achieves the equivalent BER compared to the original proposed scheme. - Author(s): L. Cong ; L. Zhao ; H. Zhang ; K. Yang ; G. Zhang ; W. Zhu
- Source: IET Communications, Volume 5, Issue 4, p. 563 –573
- DOI: 10.1049/iet-com.2010.0186
- Type: Article
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A pricing-based non-cooperative game is proposed to stimulate cooperation and perform spectrum allocation in multi-relay cooperative transmission networks. The authors construct a buyers' market competition model to consider that multiple relays are willing to share their spectrum resources with a single user. Both the benefits of the relays and the user are concerned in the game. First, according to the current user's demand, the relays as sellers compete with each other to determine the price of relaying that can maximise their profits. Then to maximise its utility, the user purchases the optimal amount of spectrum resources from each relay. The existence of the Nash equilibrium (NE), that is, the solution of the game, is proved. Even though the NE can be obtained in a centralised manner, a distributed algorithm to search for the NE is developed, which is more applicable in practical systems. Also, the convergence conditions of the algorithm are also analysed. Furthermore, the authors have also proved that the NE is not efficient when considering the total relays' profits. Thus, a general method to find the global optimal solution that maximises the total relays' profits is given. Simulation results show, by using the game, that a reasonable spectrum allocation can be performed between the relays and the user.
Robustness analysis of an unstructured overlay for media communication
Cooperative relaying protocol for energy-constrained ad hoc networks
Uplink single-carrier frequency division multiple access system with joint equalisation and carrier frequency offsets compensation
Fault tolerant spatio-temporal fusion for moving vehicle classification in wireless sensor networks
Rate regions of secret key sharing in a new source model
Direct sequence spread spectrum point-to-point communication scheme in underwater acoustic sparse channels
Experimental evaluation of bandwidth allocation for the master–slave/token-passing protocol
Transform domain communication systems from a multidimensional perspective, impacts on bit error rate and spectrum efficiency
Multi-branch successive interference cancellation for MIMO spatial multiplexing systems: design, analysis and adaptive implementation
Robust multiuser detection using Kalman filter and windowed projection approximation subspace tracking algorithm
Switchable-rate quasi-cyclic low-density parity-check codes for internet protocol over high-frequency systems
Improved low complexity hybrid turbo codes and union bound analysis
Guaranteeing the timely transmission of periodic messages with arbitrary deadline constraints using the timed token media access control protocol
Probabilistic data association detectors for multi-input multi-output relaying system
Reducing handoff delay of wireless access in vehicular environments by artificial neural network-based geographical fingerprint
Non-uniform sampling point selection in orthogonal frequency division multiplexing receiver with fractional sampling
Pricing-based game for spectrum allocation in multi-relay cooperative transmission networks
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