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Communications, IET

Issue 1 • Date January 5 2010

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Displaying Results 1 - 12 of 12
  • Fair incentive mechanism with pyramidal structure for peer-to-peer networks

    Page(s): 1 - 12
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (367 KB)  

    Free-riding is a grave threat against the existence and efficient operation of peer-to-peer networks. This study proposes a rank-based fair incentive mechanism to restrain free-riding and solve the problem of the tragedy of the commons. In this mechanism, each user has a rank according to its utility value and it can just visit the corresponding rating files with its rank in the system. The utility function in this study takes the absolute contribution value and the physical performance into account for fairness and their values are calculated by the analytic hierarchy process. Besides, a pyramidal rank structure is constructed in this mechanism, and the computation formula for the node's transfer in each layer is established. In addition, the four defects in other restrain mechanisms are resolved in this incentive mechanism. The simulations in three aspects have verified that this mechanism is effective and practical. View full abstract»

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  • Bit error rate analysis of diversity M-phase-shift keying receivers in weibull fading with cochannel interference

    Page(s): 13 - 25
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (299 KB)  

    In this study, the effect of introducing cochannel interference (CCI) on the performance of diversity receivers operating over the Weibull fading channel is thoroughly investigated. More specifically, the authors derive novel bit error rate (BER) expressions for the dual-branch selection combining (SC) and post-detection equal gain combining (EGC) diversity M-PSK receivers with possibly correlated branches operating over Weibull fading channels in presence of CCI. A characteristic function (CF)-based approach is used to achieve this goal. For the EGC correlated branches case, because of lack of existence of a closed-form expression for the CF of the sum of two Weibull random variables (RVs), the authors revert to using the Pade?? approximation (PA) technique to approximate this CF by a rational function and hence an approximate BER expression is obtained. Various results pertaining to the effect of fading severity of both the desired signal and the interferers, the effect of the number of interferers and the effect of correlation between diversity branches for different M-PSK modulations are presented. The obtained results are verified by comparison with Monte Carlo simulations and excellent agreement is observed. View full abstract»

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  • Bandwidth efficient concatenated coding schemes

    Page(s): 26 - 31
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (205 KB)  

    Concatenated coded modulation is a powerful method for constructing coding schemes with large coding gain and low decoding complexity. For the concatenated scheme, the outer code has redundancy and the overall transmission rate is reduced. The problem of bandwidth expansion can be overcome by two procedures. First, the code rate of inner codes is increased with a special coding design. Second, a two-level concatenated scheme is constructed to compensate the rate loss. This way, the low-complexity concatenated coded modulation schemes can be designed without bandwidth expansion as compared with the uncoded scheme. View full abstract»

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  • Quality of service supporting downlink scheduling scheme in worldwide interoperability for microwave access wireless access systems

    Page(s): 32 - 38
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (743 KB)  

    IEEE 802.16 is a standardisation for a broadband wireless access in metropolitan area networks (MAN). Since the IEEE 802.16 standard defines the concrete quality of service (QoS) requirement, a scheduling scheme is necessary to achieve the QoS requirement. Many scheduling schemes are proposed with the purpose of throughput optimisation and fairness enhancement, however, few scheduling schemes support the delay requirement. In this study, the authors propose a new scheduling scheme reflecting the delay requirement. Specifically, the authors add the delay requirement term in the proportional fair scheduling scheme and the scheduling parameters are optimised with respect to the QoS requirement. Therefore the QoS requirement is achieved without the excessive resource consumption. View full abstract»

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  • Adaptive modelling and long-range prediction of mobile fading channels

    Page(s): 39 - 50
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (540 KB)  

    A key element for many fading-compensation techniques is a (long-range) prediction tool for the fading channel. A linear approach, usually used to model the time evolution of the fading process, does not perform well for long-range prediction applications. An adaptive fading channel prediction algorithm using a sum-sinusoidal-based state-space approach is proposed. This algorithm utilises an improved adaptive Kalman estimator, comprising an acquisition mode and a tracking algorithm. Furthermore, for the sake of a lower computational complexity, an enhanced linear predictor for channel fading is proposed, including a multi-step AR predictor and the respective tracking algorithm. Comparing the two methods in our simulations show that the proposed Kalman-based algorithm can significantly outperform the linear method, for both stationary and non-stationary fading processes, and especially for long-range predictions. The performance and the self-recovering structure, as well as the reasonable computational complexity, makes the algorithm appealing for practical applications. View full abstract»

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  • Directional modelling of ultra wideband communication channels

    Page(s): 51 - 62
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (508 KB)  

    Ultra wideband (UWB) propagation is antenna-dependent, and multipath components experiencing specular diffraction or arriving at different angles have different shapes. To utilise the diversity of the multipath components, this study proposes a statistical model which incorporates directional parameters, such as elevation and azimuth angles by extending the IEEE802.15.3a model. Based on this model, a UWB directional simulator is developed. A novel multi-template subtractive deconvolution is applied to an extensive measurement campaign and simulated profiles. The use of multi-templates makes possible the directional estimation of the multipath components with a single receive antenna, and the use of subtractive deconvolution allows for the resolution of overlapping components and higher energy capture. Directional characterisation of UWB channels facilitates performance evaluation studies and achieves more accurate positioning, imaging and Rake receiver design. View full abstract»

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  • Outage probability of multiuser transmit antenna selection/maximal-ratio combining systems over arbitrary nakagami-m fading channels

    Page(s): 63 - 68
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (554 KB)  

    The outage probability of multiuser diversity (MUD) in transmit antenna selection/maximal-ratio combining (TAS/MRC) systems is derived as an exact closed expression in independent and identically distributed (i.i.d.) Nakagami-m channels with an integer fading parameter. For a non-integer fading parameter, the exact outage probability is derived as a single infinite series of incomplete Gamma function. At high signal-to-noise ratios (SNRs), the analytical results deduce that the multiuser TAS/MRC systems can achieve a full diversity order equal to the product of the fading parameter, number of users, number of transmit antennas and number of receive antennas. The advantage of the total diversity gain becomes more pronounced on a severe fading channel. The achieved results provide an analytical framework for the assessment of multiuser TAS/MRC systems. All the derived expressions are verified by Monte Carlo simulations. View full abstract»

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  • Transceiver scheme for single-carrier frequency division multiple access implementing the wavelet transform and peak-to-average-power ratio reduction methods

    Page(s): 69 - 79
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1116 KB)  

    Single-carrier frequency division multiple access (SC-FDMA) has been adopted as a possible air interface for future wireless networks. It combines most of the advantages of orthogonal frequency division multiple access (OFDMA) and the low peak-to-average-power ratio (PAPR) of single-carrier transmission. This study proposes a new transceiver scheme for SC-FDMA systems implementing the wavelet transform to decompose the transmitted signal into approximation and detail components. The approximation component can be clipped or companded whereas the detail component is left unchanged because of its sensitivity to noise. Wavelet filter banks at the transmitter and the receiver demonstrate the ability to reduce the distortion in the reconstructed signal while retaining all the significant features present in the signal. The performance of the proposed scheme is investigated with different PAPR reduction methods. Simulation results show that the proposed scheme with the hybrid clipping and companding method provides a significant performance enhancement when compared with the conventional SC-FDMA system, while the complexity of the system is slightly increased. View full abstract»

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  • Fair scheduling with rate control for IEEE 802.16 broadband wireless networks

    Page(s): 80 - 90
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (520 KB)  

    Although the scheduling problem of the uplink transmission in the IEEE 802.16 broadband wireless access network is extensively discussed, most of the results are limited to the quality of service (QoS) upon throughput and delay requirement. But as in practice only limited wireless resources are made available, a fairness-based scheduling upon each connection's QoS provides better outcomes. In this study, the authors propose a new fair uplink scheduling for real-time polling service and non-real-time polling service with the proportional sharing of excess bandwidth of the network. To implement the proposed fair scheduling that satisfies the delay requirement and full bandwidth utilisation, the authors introduce the rate control algorithm. With the proposed scheduling, we guarantee the fairness, delay requirement and full bandwidth utilisation which are not fully achieved in the existing results. View full abstract»

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  • Coverage probability analysis of IEEE 802.16 system with smart antenna system over stanford university interim fading channels

    Page(s): 91 - 101
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (712 KB)  

    The IEEE 802.16 system, a promising wireless communication system, has a maximum transmission range of 50 km according to the IEEE 802.16 standard. In reality, the transmission range and coverage probability of an IEEE 802.16 system vary for different wireless scenarios. Evaluating the transmission range and coverage probability of an IEEE 802.16 system prior to implementation is important. Hence, the Stanford University Interim (SUI) channel model in IEEE 802.16 specifications is suitable for evaluating the performance of IEEE 802.16 systems. To generate an effective method for predicting coverage, this study uses the SUI channel model to analyse the coverage probability of an IEEE 802.16 system. Furthermore, this study utilises a smart antenna system (SAS) to enhance IEEE 802.16 system performance. In terms of different antenna heights of the Base Transceiver Station and Customer Premises Equipment, the performance evaluation results show that the cell radius with the SAS is at least 30 more than that without the SAS. View full abstract»

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  • Energy-efficient directional routing between partitioned actors in wireless sensor and actor networks

    Page(s): 102 - 115
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (851 KB)  

    Actor-actor communication is an important part of the functioning of wireless sensor-actor networks and enables the actor nodes to take coordinated action on a given event. Owing to various reasons such as actor mobility and low actor density, the actor network tends to get partitioned. The authors propose to use the underlying sensor nodes, which are more densely deployed, to heal these partitions. In order to maximise the utilisation of the limited energy available with the sensor nodes, a new routing protocol for actor-actor communication using directional antennas on the actor nodes is proposed. The authors contribution is threefold. First, using simulations they show that the problem of partitioning in the actor networks is significant and propose an architecture with directional antennas on actor nodes and sensor bridges to heal these partitions. Second, they identify the routing problem for this architecture based on a theoretical framework and propose centralised as well as distributed solutions to it. Third, they develop a routing protocol based on the distributed solution and show, using network simulations, that the proposed protocol not only heals the network partitions successfully, but also achieves high throughput and fairness across different flows, in addition to maximising the network lifetime. View full abstract»

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  • Cascaded generalised-K fading channel

    Page(s): 116 - 124
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (503 KB)  

    A versatile fading distribution that generalises many commonly used models for multi-path and shadow fading is the so-called generalised-K (KG) distribution. By considering the product of N independent but not necessarily identically distributed (n.i.d.) squared KG random variables (RVs), we derive exact closed-form expressions for the moment generating function, probability density function, cumulative distribution function and the moments of the cascaded KG fading channel. Expressions for the ergodic capacity and the error performance of different digital modulation schemes are also obtained. Based on the above mentioned formulas, we analyse the performance of orthogonal space-time block codes over multiple-input multiple-output keyhole KG fading channels. Various performance evaluation results demonstrate the proposed mathematical analysis. View full abstract»

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IET Communications covers the theory and practice of systems, networks and applications involving line, mobile radio, satellite and optical technologies for telecommunications, and Internet and multimedia communications.

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