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Online ISSN 1751-8636 Print ISSN 1751-8628

IET Communications

Volume 4, Issue 13, 3 September 2010

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Volume 4, Issue 13

3 September 2010

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  • Satellite systems, applications and networking

    • Editorial: Satellite systems, applications and networking
      Broadband satellite multimedia
      • Author(s): Y.F. Hu ; M. Berioli ; P. Pillai ; H. Cruickshank ; G. Giambene ; K. Kotsopoulos ; W. Guo ; P.M.L. Chan
      • Source: IET Communications, Volume 4, Issue 13, p. 1519 –1531
      • DOI:  10.1049/iet-com.2009.0453
      • Type: Article
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      • p. 1519 –1531 (13)
        The broadband satellite multimedia (BSM) architecture standardised by ETSI defines a satellite independent service access point (SI-SAP) interface layer that separates the satellite independent features of the upper layers from the satellite dependant features of the lower layers, and provides a mechanism to carry IP-based protocols over these satellite dependent lower layers. This enables interoperability at the IP layer between satellite systems of different physical and link layers technologies that fully comply with the SI-SAP concept. This study reviews past and current standardisation activities including the BSM quality of service (QoS) architecture, security architecture, network management that have been carried out by the ETSI Technical Committee-Satellite Earth Stations and Systems (TC-SES)/BSM working group and looking into the future to extend current SI-SAP functions that can enhance existing QoS provision and security management capabilities as well as proposing a mobility management architecture that complies with the IEEE 802.21 media independent handover framework to support BSM mobility and to allow integration of satellite networks with fixed and mobile network infrastructures. A service-based network management architecture is also proposed to allow management flexibility and integration of business and operation support functions, paving the way for satellite integration into the Internet of the future.
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      Medium access control scheme for supporting user mobility in digital video broadcasting-return channel via satellite/satellite second generation – general architecture and functionalities
      • Author(s): N. Celandroni ; F. Davoli ; E. Ferro ; A. Gotta
      • Source: IET Communications, Volume 4, Issue 13, p. 1532 –1543
      • DOI:  10.1049/iet-com.2009.0429
      • Type: Article
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      • p. 1532 –1543 (12)
        This study aims at summarising the work done in the SatNEx project for the development and the performance evaluation of a new access scheme for multimedia data transmissions in digital video broadcasting-return channel via satellite (DVB-RCS)/satellite second generation (S2), applied to a mobile environment. The work has been stimulating because, as far as the authors know, this research topic has not yet been fully addressed in the literature. The authors started thinking about a realistic scenario of mobility, where novel services could be offered; having defined the scenario, the authors developed a satellite access scheme suitable for transmission control protocol (TCP) sessions and video streams in mobility. In this study, the authors present the reference architecture, the access scheme, the choice of the most suitable transmission parameters and the simulation results that are obtained when transmitting the two different types of data.
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      Delivery of triple-play services over broadband satellite networks
      • Author(s): G. Fairhurst ; A. Sathiaseelan ; C. Baudoin ; E. Callejo
      • Source: IET Communications, Volume 4, Issue 13, p. 1544 –1555
      • DOI:  10.1049/iet-com.2009.0205
      • Type: Article
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      • p. 1544 –1555 (12)
        Digital video broadcast return channel via satellite system (RCS) is a key European standard that specifies a broadband satellite system using dynamic capacity assignment and multi-frequency time-division multiple access. This study introduces new architectural components for an RCS system to support advanced Internet protocol (IP)-oriented multimedia. This will allow closer integration of satellite networks with the next generation of multimedia-enabled networks enabling operators to offer triple-play services that simultaneously support voice over IP, television-over IP and other services. These types of services are particularly suited to next generation satellite systems that combine transparent and multi-spot beam satellites with on-board regenerative signal processing, and can evolve to use adaptive coding and modulation.
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      Feasibility analysis of zero-overhead near video-on-demand protocols in satellite channels
      • Author(s): H. Cerezo-Costas ; R. Asorey-Cacheda ; J. Tejada-Fuentes ; F.J. Gil-Castiñeira
      • Source: IET Communications, Volume 4, Issue 13, p. 1556 –1562
      • DOI:  10.1049/iet-com.2009.0451
      • Type: Article
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      • p. 1556 –1562 (7)
        In the nVoD (near video-on-demand) paradigm, video is distributed through broadcast channels with constrained bandwidth, so that at reception there is a bounded playback start time that is independent of the number of users. In other words, there is unlimited scalability for low bandwidth cost, at the expense of a bounded start time. Thus, regarding bandwidth, nVoD schemas are well suited for satellite channels, so packet losses have not been considered in their context for a long time. Recent research based on digital fountains and intrinsic redundancy of nVoD transmissions has produced nVoD protocols with correction capabilities, which have little or zero impact on bandwidth usage. The authors analyse the most recent proposals using satellite channel models and compare them in terms of error correction performance and client and server resources.
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      Routing metrics for store and forward satellite constellations
      • Author(s): H. Cruz-Sánchez ; L. Franck ; A.-L. Beylot
      • Source: IET Communications, Volume 4, Issue 13, p. 1563 –1572
      • DOI:  10.1049/iet-com.2009.0460
      • Type: Article
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      • p. 1563 –1572 (10)
        Route computation relies on the definition of performance indicators called routing metrics. Popular metrics are the number of hops, throughput, end-to-end delay and jitter. However, in a store and forward network displaying link disruptions, these metrics are questionable. This contribution defines seven metrics for characterising routes in a store and forward network. These metrics are: number of hops, route lifetime, end-to-end delay, capacity, synchronicity, simultaneousness and discontinuity. Some of these metrics are borrowed or adapted from classical networks, others are specifically conceived for store and forward networks. Simulations for routing in a satellite constellation show that these metrics help to capture the specifics of store and forward networks and therefore improve routing decisions.
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      Quality of experience in multicast hybrid networks: avoiding bandwidth wasting with a double-stage FEC Scheme
      • Author(s): P. Barsocchi  and  G. Oligeri
      • Source: IET Communications, Volume 4, Issue 13, p. 1573 –1579
      • DOI:  10.1049/iet-com.2009.0440
      • Type: Article
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      • p. 1573 –1579 (7)
        Quality of experience is becoming an important parameter for estimating the end user perceived video quality. Video coding algorithms are currently increasing the compression performances by exploiting the temporal and spatial correlations of multimedia information. Such a trend is self-defeating in hybrid networks, due to the frequent channel impairments experienced. Here, the authors present a double-stage forward error correction (FEC) scheme to reduce the channel impairments that a multimedia communication undergoes when broadcasting a video stream through an hybrid infrastructure constituted by satellite and terrestrial wireless links. The authors present a detailed statistical description of the terrestrial wireless channel and exploit it to design the parameters for tuning the algorithm. Simulations results show that this approach not only performs better than the error recovery techniques currently used in the literature, but it also experiences a significant reduction in the bandwidth overhead.
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      Linear quadratic control of service rate allocation in a satellite network
      • Author(s): R. Secchi ; P. Barsocchi ; F. Davoli
      • Source: IET Communications, Volume 4, Issue 13, p. 1580 –1593
      • DOI:  10.1049/iet-com.2009.0448
      • Type: Article
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      • p. 1580 –1593 (14)
        The real-time control of multiple queues handling traffic of different nature is obtaining increasing relevance in both the uplink and downlink of wireless telecommunication networks, characterised by the presence of a central access point. Such is the case of satellite networks, with either on-board processing or double-hop configuration, besides a number of terrestrial local and metropolitan wireless networks. Given a certain amount of available bandwidth, the problem is that of deciding, within a certain time frame, the allocation of bandwidth partitions for each traffic queue, whose packets are awaiting transmission; eventually, this determines the transmission rates to be passed to the scheduler and to the physical layer adaptive coding and modulation devices. In a satellite network, where this task is accomplished by a master station, residing at the access point, it is possible to take such decisions by means of a centralised controller, based on real-time instantaneous (in the downstream direction) or delayed (in the upstream) information on the queues' state. The study derives a control law to be used in this task, by adopting an approach based on optimal linear quadratic regulation. Both cases of un-delayed and delayed information are considered. The control laws are tested in a geo-stationary satellite scenario of digital video broadcasting – return channel via satellite (DVB-RCS), and the queues are considered at the medium access control level. Simulation results under real-traffic traces are also presented to highlight the effectiveness of the control and to compare alternative solutions.
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      Satellite constellation networks for aeronautical communication: traffic modelling and link load analysis
      • Author(s): A. Donner ; C. Kissling ; R. Hermenier
      • Source: IET Communications, Volume 4, Issue 13, p. 1594 –1606
      • DOI:  10.1049/iet-com.2009.0260
      • Type: Article
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      • p. 1594 –1606 (13)
        The authors examine two different non-geostationary satellite constellation networks with inter-satellite links for global air traffic control and air passenger communication. After developing a traffic model for aeronautical communication services, the authors derive bandwidth requirements for such a global system. The influence of different routing policies is discussed and they show that link loads are comparable for both medium earth orbit and low earth orbit constellations. All considerations are based on real global flight data of all commercial flights during 1 day.
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  • General articles

    • Distributed precoder with a novel version of particle swarm optimisation algorithm in QR decomposition-based multi-relay systems
      • Author(s): H. Long ; K. Zheng ; F. Wang ; M. Wei ; W. Wang
      • Source: IET Communications, Volume 4, Issue 13, p. 1607 –1616
      • DOI:  10.1049/iet-com.2009.0513
      • Type: Article
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      • p. 1607 –1616 (10)
        The QR decomposition (QRD)-based relaying protocol can achieve both the distributed array gain and the intra-node array gain in multi-input multi-output multi-relay systems. In this paper, the distributed precoding technique is first utilised in the QRD-based multi-relay system to further improve the capacity performance of the system. In order to find the optimum distributed precoder, a novel version of the particle swarm optimisation (PSO) algorithm is presented by redefining the evolution of particles on the spherical surface. Then, the complexity analysis of the proposed PSO algorithm is carried out to show its feasibility. Finally, numerical and simulation results demonstrate the performance gain of the proposed design in terms of the ergodic capacity.
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      Low-complex energy-efficient localisation algorithm for wireless sensor networks using directional antenna
      • Author(s): B. Zhang  and  F. Yu
      • Source: IET Communications, Volume 4, Issue 13, p. 1617 –1623
      • DOI:  10.1049/iet-com.2009.0763
      • Type: Article
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      • p. 1617 –1623 (7)
        The accuracy in location estimation of ad hoc deployed sensor nodes for a wireless sensor network in the presence of noisy environment and obstacle is discussed. Considering estimation accuracy, energy efficiency and range independency, the authors propose a localisation scheme using a mobile anchor node equipped with a directional antenna. Without increasing hardware and computational complexity, sensor nodes estimate their positions using the minimum number of beacon points. Each sensor node estimates its location based on the intersection point of the greatest gain direction of directional antenna. The proposed localisation scheme is verified using OPNET simulation software. The simulation results show that the proposed scheme has higher accuracy and energy efficiency than other localisation schemes.
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      Signal transmission with unequal error protection in relay selection networks
      • Author(s): H.X. Nguyen ; H.H. Nguyen ; T. Le-Ngoc
      • Source: IET Communications, Volume 4, Issue 13, p. 1624 –1635
      • DOI:  10.1049/iet-com.2009.0521
      • Type: Article
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      • p. 1624 –1635 (12)
        A relaying technique based on single-relay selection is studied for multiple-relay networks when hierarchical modulation is employed for unequal error protection. A single-relay selection scheme achieves a higher bandwidth efficiency while maintaining the same diversity order as when all the relays are selected in a multiple-relay network. Specifically, a cooperative network with one source, K relays, and one destination is considered in which two different protection information classes are modulated by a hierarchical 2/4-amplitude shift keying (ASK) constellation at the source. After selecting a relay to cooperate with the source, based on the instantaneous received signal-to-noise ratio, the selected relay decides to retransmit both classes by using a hierarchical 2/4-ASK constellation, or the more protection class by using a 2-ASK constellation, or remains silent. The approximated bit error rate (BER) of each information class is derived. Optimal thresholds are chosen to minimise the BER of one class while the BER of the other class satisfies a requirement. Numerical and simulation results are provided to validate the analysis. The results also show that the optimal thresholds can improve the error performance significantly.
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      Frequency-domain adaptive detectors for single-carrier frequency-domain equalisation in multiuser direct-sequence ultra-wideband systems based on structured channel estimation and direct adaptation
      • Author(s): S. Li  and  R.C. de Lamare
      • Source: IET Communications, Volume 4, Issue 13, p. 1636 –1650
      • DOI:  10.1049/iet-com.2009.0621
      • Type: Article
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      • p. 1636 –1650 (15)
        Here, the authors propose two adaptive detection schemes based on single-carrier frequency-domain equalisation (SC‐FDE) for multiuser direct-sequence ultra-wideband systems, which are termed structured channel estimation (SCE) and direct adaptation (DA). Both schemes use the minimum mean square error (MMSE) linear detection strategy and employ a cyclic prefix. In the SCE scheme, adaptive channel estimation is performed in the frequency domain and the despreading is implemented in the time domain after the FDE. In this scheme, the MMSE detection requires the knowledge of the number of users and the noise variance. For this purpose, simple algorithms are proposed for estimating these parameters. In the DA scheme, the interference suppression task is fulfilled with only one adaptive filter in the frequency domain and a new signal expression is adopted to simplify the design of such a filter. Least mean squares, recursive least squares and conjugate gradient adaptive algorithms are then developed for both schemes. A complexity analysis compares the computational complexity of the proposed algorithms and schemes, and simulation results for the downlink illustrate their performance.
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