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Communications, IET

Issue 14 • Date Sept. 23 2011

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Displaying Results 1 - 18 of 18
  • Performance analysis of joint single transmit and receive antenna selection in non-identical nakagami-m fading channels

    Publication Year: 2011 , Page(s): 1947 - 1953
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (511 KB)  

    In this study, joint single transmit and receive antenna selection systems are examined for independent but non-identically distributed flat Nakagami-m fading channels. Exact bit/symbol error rate expressions are derived for binary and M-ary signals by using the conventional probability density function-based analysis method and the moment generating function based analysis method for arbitrary and integer values of the fading parameters, respectively. Upper bounds are obtained in order to show that the investigated systems achieve full diversity order at high SNRs. Also, outage probability analysis has been carried out for examining system capacity. Theoretical results are validated by Monte Carlo simulations. View full abstract»

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  • Throughput analysis of IEEE 802.11-based vehicular ad hoc networks

    Publication Year: 2011 , Page(s): 1954 - 1963
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (528 KB)  

    In this study, the authors propose an analytical model to evaluate the maximum stable throughput for unicast services in vehicular ad hoc networks. In this respect, the authors employ two queueing networks (QNs) to model the mobility patterns of the vehicles as well as the multi-hop packet transmission scenario. In the proposed model, the authors map the features of IEEE 802.11, as well as the details of multi-hop packet transmission, regarding the dynamic status of vehicles, onto suitable parameters of the QNs. In the authors' modelling approach, they take the details of MAC and routing schemes into account by classifying the vehicles based on their mobility patterns and considering their dynamic status in average. By writing traffic equations and applying the stability condition, the authors compute the maximum stable throughput of the network, that is, the maximum rate of packets successfully received at the destinations while all vehicles are in stable conditions. In the last part of the study, the authors show the effect of some network parameters onto the maximum stable throughput and confirm the validity of their model by simulation. View full abstract»

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  • Joint maximum-likelihood estimation of frequency offset and channel coefficients in multiple-input multiple-output orthogonal frequency-division multiplexing systems with timing ambiguity

    Publication Year: 2011 , Page(s): 1964 - 1970
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (426 KB)  

    In this study, the authors consider a multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing system operating over unknown frequency-selective fading channels. Based on two different signal models, two maximum-likelihood schemes for joint carrier frequency offset (CFO) and MIMO channel estimation under timing ambiguity have been derived. The first estimator jointly estimates the timing offset, CFO and channel coefficients, but the complexity is high owing to the need of two-dimensional searches. The second estimator has a reduced complexity, but its performance slightly degrades compared with the first one. The performance of proposed estimators was benchmarked with Cramer-Rao bounds (CRB), and investigated by computer simulations. The simulation results show that the proposed estimators achieve almost ideal performances compared with the CRB. View full abstract»

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  • Average capacity and signal-to-noise ratio analysis of multi-antenna regenerative cooperative relay in rayleigh fading channel

    Publication Year: 2011 , Page(s): 1971 - 1977
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (606 KB)  

    Performance of infrastructure-based fixed relay having multiple antennas has been analysed. Closed form expressions of average capacity and end-to-end received signal-to-noise ratio for such system are derived for Rayleigh fading channels. Here, relay and destination may perform either maximum ratio combining or selection combining of the signals. The effect of relay position and number of relay antennas in various path-loss conditions have been studied for all four combinations of combining schemes. The investigations reported in this study are expected to be useful in design of multi-antenna cooperative relay system. View full abstract»

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  • Statistical analysis of H.264 video frame size distribution

    Publication Year: 2011 , Page(s): 1978 - 1986
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (585 KB)  

    H.264 video traffic is expected to account for the majority of multimedia traffic to be carried in future heterogeneous networks. Modelling video frame sizes is highly useful in simulation studies, mathematical analysis and generating synthetic video traces for the purpose of testing and compliance. In this study, a statistical analysis is performed to determine an appropriate distribution of video frame sizes generated by the popular H.264 video codec. The study makes use of a number of real video traces with the goal of evaluating and fitting their frame sizes with well-known distributions. In the literature, it is reported that the Gamma and Weibull distributions give the best fit for frame sizes in the most popular video codecs including H.264. Our statistical analysis shows that both Gamma and Weibull distributions are very close to each other in terms of goodness-of-fit results and they give the best fit. The authors also show that the Inverse Gaussian distribution is ranked second after Gamma and Weibull distributions. Finally, they show that the distributions of Pearson Type V and Lognormal are ranked third and fourth in terms of goodness-of-fit. View full abstract»

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  • Resource management scheme for multicasting in orthogonal frequency division multiple access-based single frequency networks

    Publication Year: 2011 , Page(s): 1987 - 1998
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (510 KB)  

    In this study, the authors present a resource allocation scheme that determines both a set of multicast basestations and a transmission scheme minimising the aggregate number of multicast resources in all of the multicast basestations while satisfying the multicast coverage requirement in an orthogonal frequency division multiple access-based single frequency networks (SFNs). In particular, the proposed scheme consists of two phases. In the first phase, a multicast basestation set and a transmission scheme are initially found to minimise the aggregate number of multicast resources. Then, in the second phase, the transmission scheme is adjusted according to the multicast users' performance reports. In addition, the multicast basestation set is adaptively updated if the aggregate number of multicast resources significantly changes as compared to that after the set was most recently updated. Using computer simulations, the authors demonstrate that the proposed scheme can efficiently utilise the radio resources for multicast transmission. View full abstract»

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  • Bit error rate minimising pilot symbol arrangement in closed-loop orthogonal frequency division multiplexing systems

    Publication Year: 2011 , Page(s): 1999 - 2008
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (602 KB)  

    The use of a feedback link in wireless orthogonal frequency division multiplexing (OFDM) systems is analysed. Although open-loop scenarios have been rigorously investigated in the literature, closed-loop scenarios, in which there is a feedback link from a strong to a weak user, have not been thoroughly studied. The study mainly focus on the recently proposed dynamic pilot symbol arrangement strategy. It was shown in a recent paper that for coherent OFDM transmission, this strategy is capable of delivering substantial gains in the performance. Pilot symbols are used to sample channel behaviour so that data symbols can be decoded correctly. However, these pilots do not need to be arranged so as to estimate the channel in the best possible way. In this work, the authors propose a pilot symbol arrangement strategy that minimises the bit error rate, we analyse the solution in detail and propose a low complexity search that maintains most of the quality of an exhaustive search. This low complexity search makes the pilot symbol method viable for medium to large-scale OFDM systems. The authors also analyse the use of a Wiener filter for channel estimation combined with the dynamic pilot symbol strategy and show that it delivers good gains in comparison to a simple maximum likelihood channel estimate. View full abstract»

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  • Novel spectral efficient cooperative relaying protocols with low communication overhead

    Publication Year: 2011 , Page(s): 2009 - 2017
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (359 KB)  

    In this study, the authors propose two high spectral efficient relaying protocols with low communication overhead including: the priority-based relay selection (PRS), and the priority-based relay selection with incremental transmission (PRSIT). Relay selection and scheduling are integrated in the proposed protocols to achieve full diversity order as well as high spectral efficiency. The authors then define the communication overhead per allocated time slot to a user as the number of required signalling bits for channel estimation and implementing corresponding communication procedures. In this study, the authors show that their proposed protocols have much lower communication overhead comparing with other high spectral efficient cooperative protocols such as opportunistic relaying (OR) and OR with incremental transmission while their achieved diversity-multiplexing trade off performances are the same as those protocols. The authors further show that the average communication overhead for the PRS and PRSIT is a logarithmic function of the number of users while it is a linear function in OR and OR with incremental transmission. Simulation results also show that however, the authors proposed protocols impose much lower communication overhead, they either outperform or act closely to the existing cooperative protocols in the outage probability. View full abstract»

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  • Performance of hybrid decode-amplify-forward protocol for multiple relay networks over independent and non-identical flat fading channels

    Publication Year: 2011 , Page(s): 2018 - 2027
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (424 KB)  

    In this study, the authors investigate the hybrid decode-amplify-forward (HDAF) relaying protocol for the multiple parallel relays over independent and non-identical distribution flat Rayleigh fading channels using maximum ratio combining at the destination. They derive closed-form tight bounds for the outage probability and bit error rate (BER) of the HDAF relaying protocol. They also show that the outage probability performance of this protocol outperforms decode-forward (DF) protocol, and is very close to amplify-forward (AF) scheme. On the other hand, the BER of the HDAF scheme is superior to AF protocol, and is close to BER of DF scheme. From practical point of view, when taking into account outage and BER performance of a system together, the HDAF protocol performs better than AF and DF schemes by combining the merits of both. Also, the authors investigate power allocation among the relay nodes to minimise the system outage probability and BER under total and individual power constraints. Numerical results are provided to show the correctness of our analytical expressions. View full abstract»

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  • Variable neighbourhood search for resolving routing and wavelength assignment problem in optical wavelength-division multiplexing networks

    Publication Year: 2011 , Page(s): 2028 - 2034
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (321 KB)  

    The issue of finding optimal signal routes is one of the main challenges within the framework of optimal networks. This study aims at illustrating the development of a new, mixed-integer mathematical model for solving the static routing and wavelength assignment (RWA) problem in optical wavelength-division multiplexing (WDM) networks and presents the comparison of results obtained by heuristics and CPLEX commercial software. The objective function of the mathematical model is to minimise the blocking probability by maximising the number of successfully connected lightpaths. In this paper two WDM networks with full wavelength conversion nodes were tested. The proposed heuristics are the variable neighbourhood search (VNS) and tabu search (TS). Firstly, the authors compare the results obtained by these two heuristics and CPLEX on a low-complexity WDM network, aiming to determine whether these heuristics may yield results which approximate optimal results. Secondly, having illustrated that the heuristics provide satisfactory results, the authors run these heuristics on a high-complexity WDM network. The results indicate minor differences in blocking probability and show that in majority cases, VNS spends ten times less CPU time as opposed to TS. In conclusion, the authors argue that VNS heuristic is appropriate for resolving this static RWA problem. View full abstract»

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  • Fast subspace approach for mobile positioning with time-of-arrival measurements

    Publication Year: 2011 , Page(s): 2035 - 2039
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (219 KB)  

    Mobile station (MS) localisation, which plays an important role in the process of target continuous localisation, has received considerable attention. In this study, a new framework based on subspace approach for positioning an MS at three or more base stations (BSs) with the use of time-of-arrival (TOA) measurements is introduced. It is shown that the proposed approach is a generalisation of the mobile localisation method based on multidimensional scaling (MDS) analysis. Through computer simulations and computational complexity analysis, the authors can see that the proposed algorithm has a comparable performance with conventional MDS localisation method, however, the computational complexity has been greatly reduced. View full abstract»

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  • Power allocation in wireless multiuser multi-relay networks with distributed beamforming

    Publication Year: 2011 , Page(s): 2040 - 2051
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (480 KB)  

    This article studies optimal power allocation schemes in a multi-relay cooperating network employing amplify-and-forward (AF) protocol with multiple source-destination pairs. It is assumed that full channel state information is available at the relays. As such, distributed beamforming is employed in forwarding signals to the destinations. In this context, the authors extend recent works on distributed beamforming for a single source-destination pair to the scenario where multiple source-destination pairs are competing for the power resource at the relays. Under orthogonal transmissions of each source-destination pair, considered are the two following power allocation problems: (i) minimise the sum relay power with guaranteed quality of service (QoS) in terms of signal-to-noise ratio (SNR) at the destinations, and (ii) jointly maximise the SNR margin at the destinations subject to individual power constraints at the relays. Although these optimisation problems can be formulated as second-order conic programs (SOCP), the main contribution of this work are proposals of simple and fast converging numerical algorithms, based on the fixed point iteration framework, to efficiently solve these two problems. View full abstract»

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  • Transmit beamforming and interference shaping in cellular cognitive radio networks

    Publication Year: 2011 , Page(s): 2052 - 2058
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (543 KB)  

    Optimising the quality-of-service for secondary users and minimising interference to the primary users are two important objectives of cognitive radio networks. In this study, the authors address these issues by introducing interference shaping criteria into orthogonal transmit beamforming (OTBF) strategies. Then, the authors formulate this problem using semi-definite programming (SDP) and find the optimal beamforming weight vectors at the secondary base station. The authors also introduce a resource allocation strategy which enables the base station to ensure a weighted fairness among the secondary users, hence, optimising the network for heterogeneous traffic patterns. The authors show that in terms of satisfying the signal-to-interference-plus-noise-ratio (SINR) requirements at the secondary users, their modified maximin SINR and modified minimum transmit power strategies produce fairly close results at the same transmit powers. However, in terms of minimising interference seen by the primary users, the former outperforms the latter. Finally, the authors study the impact of various interference shaping margins (ISMs) on the OTBF strategies. The authors show that the allocated power by the modified minimum transmit power strategy and the SINRs achieved by the modified maximin SINR strategy are inversely and directly proportional with the ISMs, respectively. View full abstract»

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  • Relay selection and beamforming for cooperative bi-directional transmissions with physical layer network coding

    Publication Year: 2011 , Page(s): 2059 - 2067
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (363 KB)  

    Application of network coding in wireless communications has enabled the development of physical layer network coding (PLNC). Applying the principle of PLNC to wireless cooperative networks for spectral efficiency improvement has recently received tremendous attention from the research community. The best relay selection is extensively investigated in the literature for PLNC cooperative networks with multiple relays. However, the authors study the problem of signal beamforming and relay selection for a cooperative bi-directional relay network using PLNC and consider signal beamforming and relay selection for (i) multiple relays each equipped with single antenna and (ii) multiple relays with multiple antennas on uncoded amplify-and-forward scheme for PLNC transmission. The authors derive the optimal design criteria and provide low-complexity sub-optimal solutions for relay selection and beamforming to minimise the symbol error probability. View full abstract»

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  • Space-alternating generalised expectation-maximisation-based h-infinity channel estimator for multiple-input multiple-output-orthogonal frequency division multiplexing systems

    Publication Year: 2011 , Page(s): 2068 - 2074
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (332 KB)  

    This study presents a low-complexity and robust H-infinity channel estimator for multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. The H-infinity estimator, which has never been devoted to MIMO-OFDM systems, could be implemented by applying a multiple-order auto-regression (AR) model. However, it may increase the design complexity of receivers and lead to poor real-time property when this model is used for MIMO-OFDM systems, which makes the authors abandon AR model. In order to reduce the number of matrices manipulations because of the each received OFDM symbols from different transmit antennas, the iterative space-alternating generalised expectation-maximisation (SAGE) algorithm is adopted. Furthermore, to deal with the effect of non-Gaussian noise (NGN) channels, because of various natural or man-made impulsive sources, an equivalent signal model (ESM) is introduced to alleviate the effect of this issue and enhance the robust of SAGE-based H-infinity estimator. Simulation results show that H-infinity estimator has almost the same bit error rate performance as optimal maximum a posteriori estimator. The performance gain afforded by using ESM can be substantial when compared with using the traditional signal model, which dramatically enhance the robustness of SAGE-based H-infinity estimator against NGN channels. View full abstract»

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  • Optimal resource allocation for orthogonal frequency division multiplexing-based multi-destination relay systems

    Publication Year: 2011 , Page(s): 2075 - 2081
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (355 KB)  

    The authors propose an optimal resource allocation (RA) scheme for wireless multi-destination relay systems with orthogonal frequency division multiplexing (OFDM) modulation. The authors work is different in that they consider a practical downlink OFDM-based relay network, where a relay is used to help the source (base station) communicate with multiple out-of-range destinations (users), rather than a single destination (user) as assumed in most previous work. The proposed optimal RA scheme consists of subchannel allocation (SA), subchannel pairing and joint source-relay power allocation (PA). In particular, it is shown that both SA and joint source-relay PA play a dominant role in the three steps of RA. It is also demonstrated that the shorter the distance between the source and the relay, the more impact of multiuser diversity on the system capacity. By employing SA and joint source-relay PA only, a near-optimal performance can be achieved. This work can be extended to the multi-hop, multi-relay and multi-destination uplink/downlink OFDM system. View full abstract»

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  • Synchronisation-based, multi-channel multi-interface medium access scheme in ad hoc network

    Publication Year: 2011 , Page(s): 2082 - 2090
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (560 KB)  

    Multi-channel multi-interface (MCMI) medium access can provide high-throughput services for wireless ad hoc networks. However, the multi-channel hidden terminal problem and the rendezvous problem must be addressed. This study aims to design a low-cost integrated solution to address the two problems, so as to fully exploit the available wireless interfaces and channels to enhance the network performance, especially the network aggregated throughput. The authors propose a new MCMI synchronisation-based media access control (SMAC) protocol with the operation of two interfaces. Unlike other studies, the authors propose a novel interface classification using a synchronisation interface (SynIF) and a normal interface (NorIF). A synchronisation mechanism and a new channel coordination procedure are operated on SynIF, and data packets can be transmitted on SynIF and NorIF concurrently. All control messages occur only in a variable-length channel coordination window (CCW) on a common control channel. The maximum length of CCW and network throughput are analysed mathematically and the performance of the protocol is validated in ns-2 simulator through comparisons with few other MCMI-MAC protocols. In IEEE 802.11-based multi-interface ad hoc networks, when using MCMI-SMAC, the results show that the network aggregated throughput is enhanced significantly and the protocol overhead is very low. View full abstract»

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  • Wavelet-based downlink scheduling and resource allocation for long-term evolution cellular systems

    Publication Year: 2011 , Page(s): 2091 - 2095
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (326 KB)  

    This study proposes the use of wavelet transform in long-term evolution (LTE) cellular systems. Mathematical expressions are derived to represent data rate in LTE downlink transmission based on Wavelet and Fourier Transforms. Furthermore, a comparison between these two systems is provided. Simulation results show the proposed orthogonal wavelet division multiplexing (OWDM) approach outperforms the traditional orthogonal frequency division multiplexing-based systems. The data rate can also be increased by the amount of CyclicPrefix/SymbolTime%, as there is no need for a channel prefix in an OWDM-based system. View full abstract»

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