IEE Proceedings - Communications
Volume 151, Issue 1, February 2004
Volumes & issues:
Volume 151, Issue 1
February 2004
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- Author(s): S.-J. Park and J.-T. Lim
- Source: IEE Proceedings - Communications, Volume 151, Issue 1, p. 1 –7
- DOI: 10.1049/ip-com:20040107
- Type: Article
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For the major signalling protocols SIP and H.323 in a multimedia communication session, the authors present a systematic method for designing gateways between call setup modes of the protocols using the supervisory control framework for nondeterministic discrete event systems. In particular, it is shown that the nonblockingness of a gateway to be designed is guaranteed by the nonblockingness of a language implementing a given specification described as specific messages. - Author(s): B. Bouallegue ; R. Djemal ; H. Guesmi ; R. Tourki ; J.P. Diguet ; J.-L. Philippe
- Source: IEE Proceedings - Communications, Volume 151, Issue 1, p. 8 –13
- DOI: 10.1049/ip-com:20040357
- Type: Article
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Real-time communication services related to encoded video transmission over a high-speed network such as ATM need a new integrated protocol architecture to meet the required quality. Data cells are exposed to delays and losses, which affect the video signal quality, and so adequate processing is needed in order to keep the quality of service as an acceptable level. The authors propose the design of a new adaptation of MPEG-2 video in ATM networks in order to improve the video visual quality. The approach, based on a new MPEG-2 protocol architecture, tries to overcome the difficulty imposed by traditional random cell discarding due to the bursty aspect of the traffic and the variable bit rate transmission nature of encoded video. The importance of including a dynamic bandwidth reallocation and appropriate interleaving technique for bursty encoded video traffic being carried in an ATM network is shown, by comparing the degradation quality of an MPEG-2 sequence with and without the proposed techniques. The results show that the proposed interface is effective in solving the cell-loss problem and thus enhances the QoS for MPEG-2 video transmission in ATM networks. - Author(s): Y. Zhang and S.A. Kassam
- Source: IEE Proceedings - Communications, Volume 151, Issue 1, p. 15 –19
- DOI: 10.1049/ip-com:20040276
- Type: Article
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Robustness against deviations from nominal source pdf assumptions is very desirable in blind source separation (BSS) algorithms. In the paper, a new approach for robust BSS is proposed. The EASI (equivariant adaptive separation by independence) algorithm (Cardoso and Laheld, 1996) is modified to use ranks of observed signals. The modified EASI algorithm can be applied to both real-valued and complex-valued data. Design guidelines are discussed for the nonlinear rank weighting functions in the modified EASI algorithm. Simulation results for two examples are given, showing very good performance. - Author(s): H.R. Sadjadpour
- Source: IEE Proceedings - Communications, Volume 151, Issue 1, p. 20 –24
- DOI: 10.1049/ip-com:20040404
- Type: Article
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The author considers the use of coding to reduce the peak-to-mean envelope power ratio (PMEPR) for orthogonal frequency division multiplexing (OFDM) systems. Most of the existing schemes that use coding for PMEPR reduction assume a PSK constellation. The author presents the construction of non-square M-QAM symbols from a combination of QPSK and BPSK signals when M=2n and n is an odd number. By using QPSK and BPSK Golay (or Golay-like) sequences, M-QAM sequences with low PMEPR are generated. An upper bound for the instantaneous envelope power of Golay-like M-QAM sequences was derived. After the mean envelope power for these sequences was computed, the general upper bound for one PMEPR of M-QAM sequences with non-square constellations was derived. - Author(s): B. Abdool-Rassool ; M.R. Nakhai ; F. Heliot ; L. Revelly ; H. Aghvami
- Source: IEE Proceedings - Communications, Volume 151, Issue 1, p. 25 –31
- DOI: 10.1049/ip-com:20040403
- Type: Article
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The authors address the problematic issues in generating space–time trellis codes, and propose novel methods for reducing the exponentially growing full code search. It is proved that by exploiting the symmetry in QAM and PSK constellations, together with the modulo operation in the encoder, the number of possible combinations in the generator matrix can be halved when performing a full search to obtain optimal codes. It is also shown that for a fixed set of columns in the generator matrix, interchanging columns yields identical results, hence reducing the full code search by the factorial of the number of transmit antennas. Furthermore, the existing sub-optimal (but fast) method for obtaining codes is investigated and results from this method are compared with those obtained from the two proposed methods. Using the suggested methods, novel space–time codes for both slow and fast fading environments are generated and their performance is evaluated through frame error probabilities obtained by simulation. - Author(s): H. Fu and S. Attallah
- Source: IEE Proceedings - Communications, Volume 151, Issue 1, p. 32 –38
- DOI: 10.1049/ip-com:20040114
- Type: Article
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The problem of CDMA multiuser detection in the presence of a small residual carrier offset is considered, with subspace-based approaches being employed for channel estimation and signal demodulation. The channel response and the carrier offset are estimated separately to avoid the complicated computation in the joint estimation of two parameters. The simulation results show that the separate estimation approach results in lower BER than does a previous subspace-based joint estimation algorithm for a large range of carrier offsets that are generally considered in practical applications. Adaptive channel estimation in a time-variant channel is also considered. A novel adaptive algorithm for subspace estimation, namely the NOOja algorithm, is used to track the channel variations. The NOOja algorithm offers a set of advantages as compared to similar algorithms in the literature; in particular, it can be used for both signal and noise subspace estimation and has a very low computational complexity as compared to the batch eigendecomposition techniques. - Author(s): K. Choi ; K. Kang ; S. Kim
- Source: IEE Proceedings - Communications, Volume 151, Issue 1, p. 39 –43
- DOI: 10.1049/ip-com:20040407
- Type: Article
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A new PAPR (peak-to-average power ratio) reduction scheme is proposed for MC-CDMA (multicarrier-CDMA) using subcarrier scrambling. Based on the fact that the PAPR of the MC-CDMA signal is highly dependent on the scrambling pattern of the subcarriers irrespective of users' data symbols, the optimum fixed scrambling patterns for each combination of user spreading codes are searched to achieve the minimum PAPR. This enables the system to dynamically allocate the optimum scrambling pattern during system operation. The proposed scheme achieves a significant reduction in PAPR compared to random scrambling, especially for a small number of users. A simple suboptimum scrambling scheme is also proposed where a common scrambling pattern is used irrespective of the code combinations. - Author(s): J.M.P. Fortes ; R. Sampaio-Neto ; J.M.O. Goicochea
- Source: IEE Proceedings - Communications, Volume 151, Issue 1, p. 44 –49
- DOI: 10.1049/ip-com:20040348
- Type: Article
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The authors present strategies and modifications to the implementation of the so-called analytical method used in interference analysis involving non-GSO (non-geostationary orbit) systems. The proposed modifications aim at the reduction of the required computer time to values that make the method a practical interference evaluation tool in situations involving multiple non-GSO systems. It is shown that substantial reduction in computer time can be achieved through the adoption of an adaptive step size mechanism for the discretisation of the non-GSO satellite positions and through the use of Gauss quadrature rule numerical integration. Interference computation examples are presented throughout the paper. - Author(s): K. Daikoku
- Source: IEE Proceedings - Communications, Volume 151, Issue 1, p. 50 –58
- DOI: 10.1049/ip-com:20040347
- Type: Article
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The author presents field test results on real-zero single-sideband (RZ SSB) technology carried out over a HF radio channel. The purpose of conducting field tests was to clarify whether the RZ SSB technology can be satisfactorily adapted for HF data communications. During the tests, bit error rate (BER) performances of the RZ SSB were investigated first with an ITU-T Recommendation V.29 modem with bit rates ranging from 2.4 kbit/s to 9.6 kbit/s. Successful results for BER performance led to JPEG/text file transmissions using a facsimile modem as well as the RZ SSB transceivers. Throughout testing, JPEG/text files were transmitted and received with perfect quality even through an HF simplex radio channel between two coastal stations approximately 2000 km apart after completion of normal transmission. Detailed reports on both JPEG/text files and BER transmission performance are given. In conclusion, it appears that the RZ SSB technology can certainly be adapted for HF data communication, and further it is proved that it is superior to conventional SSB technology.
Systematic design of gateways between multimedia signalling protocols using supervisors
Protocol architecture for MPEG-2 video over a high speed network
Robust rank-EASI algorithm for blind source separation
Construction of non-square M-QAM sequences with low PMEPR for OFDM systems
Search for space – time trellis codes: novel codes for Rayleigh fading channels
Fast blind channel and carrier offset estimation in multiuser CDMA
Peak power reduction scheme based on subcarrier scrambling for MC-CDMA systems
Fast computation of interference statistics in multiple non-GSO satellite systems environments using the analytical method
Field test results on JPEG/text file transmission employing RZ SSB transceivers through HF radio channel
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- Author(s): John Schormans
- Source: IEE Proceedings - Communications, Volume 151, Issue 1, p. 59 –61
- DOI: 10.1049/ip-com:20040329
- Type: Article
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- Author(s): A. Daniel
- Source: IEE Proceedings - Communications, Volume 151, Issue 1, p. 62 –70
- DOI: 10.1049/ip-com:20040133
- Type: Article
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IP virtual private networks (IP VPNs) provide the emerging network and service opportunities for telecommunication operators such as BT. The use of intranets within businesses, coupled to the success and ubiquitous deployment of Internet and IP technologies, has generated a burgeoning demand for IP VPNs. - Author(s): Y. Qin and C.K. Siew
- Source: IEE Proceedings - Communications, Volume 151, Issue 1, p. 71 –76
- DOI: 10.1049/ip-com:20040326
- Type: Article
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The authors explore the problem of dynamic virtual private networks (VPNs) over wavelength division multiplexing (WDM) networks to facilitate the guarantee of diverse quality of service (QoS) requirements of different traffic streams, especially those with very stringent delay jitter requirements and with bursty characteristics. Each VPN consists of different traffic streams with various quality sensitivities. The proposed QoS model provides three types of QoS services for various VPNs: static, optical burst switching (OBS) and alternative VPNs. All the three types provide transmission in the optical core networks without any O/E/O conversion. The static type has a set of dedicated or shared lightpaths which have been pre-allocated and the traffic from this VPN has a constant bit rate (CBR). The OBS type need to setup the lightpath using so-called optical burst switching while a traffic stream with variable bit rate (VBR) request, is occurring. The alternative type has to set up a lightpath based on two-way reservation protocols such as tell-and-wait (TAW) for the traffic with unspecified bit rate (UBR) or available bit rate (ABR). The proposed model is suitable for carrying the multimedia applications which have various sensitivities to delay and jitter. By employing dynamic VPNs directly over the WDM layer, one can eliminate the often complex QoS related functions in the upper protocol layers, and thus increase the overall communication efficiency. Furthermore, this could be the first step towards providing fine grained service over optical wide area networks. In addition, basic performance analysis and preliminary results are presented, based on simulation, and the network designer is provided with a quantitative assessment of proportion for different traffic types with different QoS service requirements. - Author(s): J. Yang ; J. Ye ; S. Papavassiliou
- Source: IEE Proceedings - Communications, Volume 151, Issue 1, p. 77 –81
- DOI: 10.1049/ip-com:20040334
- Type: Article
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The DiffServ model is considered as a scalable and viable solution to provide QoS in the Internet. However, the current DiffServ model can only provide a coarse end-to-end QoS granularity to individual data flows. This is undesirable for many network services such as the virtual private network (VPN), since it may result in low resource utilisation to guarantee the required QoS. In the paper the concept of service vector is proposed to provide finer QoS granularity in DiffServ networks through the framework of a distributed admission control scheme referred to as explicit endpoint admission control (EEAC). Specifically, by applying the proposed service vector and EEAC scheme, a data flow is allowed to choose different services at different nodes to achieve fine QoS granularity and architectural scalability. The models and solutions that represent the users' behaviour in selecting the appropriate network services are also discussed. The performance evaluation of the proposed approach demonstrates that the service vector and EEAC scheme can result in lower request drop ratio, satisfactory end-to-end performance, fine end-to-end QoS granularity, and lower cost for each user. - Author(s): J.-S. Li and C.-S. Mao
- Source: IEE Proceedings - Communications, Volume 151, Issue 1, p. 82 –88
- DOI: 10.1049/ip-com:20040393
- Type: Article
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DiffServ provides class-based differentiated quality of service (QoS). For perception of users, flow-based service differentiation is much more important than class-based. Class-based QoS per-hop behaviour (PHB) is ensured in a DiffServ router. However, a flow in a higher class may get worse QoS than a flow in a lower class due to unbalanced traffic conditions. Therefore, a novel scheme with a Bloom-filter-based estimator for number of active flows, a dynamic weighted fair queueing (WFQ) scheduler, and a queue management mechanism to provide flow-based proportional QoS differentiation is proposed. This scheme dynamically adapts the WFQ weight of each class according to estimations of numbers of active flows in each class to provide proportional bandwidth differentiation for flows in different classes. Furthermore, a queue management mechanism with estimation of numbers of active flows and queue length feedback control is employed to control the queue length of each class around a target value to achieve delay differentiation. Through detailed simulations, the proposed scheme is shown to be able to provide flow-based proportional bandwidth and delay differentiations for flows in different classes at the same time. - Author(s): T. Timotijevic ; C.M. Leung ; J. Schormans
- Source: IEE Proceedings - Communications, Volume 151, Issue 1, p. 89 –94
- DOI: 10.1049/ip-com:20040333
- Type: Article
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Where VPNs are supported by packet based networks they will be monitored using both active and passive measurement techniques. A passive monitoring scheme that offers very significant levels of accuracy and stability, without traffic overhead, and regardless of the network utilisation, is developed and analysed. Where a VPN is carried over a number of different packet networks active measurement (active probing) is needed for performance monitoring. By analysis, validated using simulation, the effect of using active probing, in terms of the additional load implied by the desired level of accuracy, using typical models of packet traffic is investigated. Active packet probing is found to begin to require too much of the link bandwidth, at the desired level of accuracy, somewhere between a load of 60% and 80%, depending on the inherent burstiness of the traffic, and whether the probing packets have to determine just the mean delay, or the delay distribution (jitter) too. The increase in probing load with increasing network utilisation is highly nonlinear; while returning accurate results for moderate loads, under higher loads a sudden increase occurs, requiring so much bandwidth that this form of monitoring would become highly inaccurate. - Author(s): M.E. Woodward and M.M.M. Al-Fawaz
- Source: IEE Proceedings - Communications, Volume 151, Issue 1, p. 95 –100
- DOI: 10.1049/ip-com:20040150
- Type: Article
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A new scheme is presented for partitioning a network having a specific number of nodes and degree of connectivity such that the number of operations required to find a constrained path between a source node and destination node, averaged over all source–destination pairs, is minimised. The scheme can speed up the routing function, possibly by orders of magnitude under favourable conditions, at the cost of a sub-optimal solution. - Author(s): S.H. Lim ; M.H. Yaacob ; K.K. Phang ; T.C. Ling
- Source: IEE Proceedings - Communications, Volume 151, Issue 1, p. 101 –106
- DOI: 10.1049/ip-com:20040335
- Type: Article
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In the paper, a traffic engineering enhancement to the QoS-OSPF routing protocol is proposed and used as the path selection algorithm in a DiffServ-MPLS network. The proposed scheme, TE-QOSPF, exploits the use of non-shortest paths to improve load-balancing and avoid network congestion. Simulation results show that the algorithm outperforms the QoS-OSPF scheme in terms of loss ratio, link utilisation, and delay. - Author(s): Y.-C. Chan ; C.-T. Chan ; Y.-C. Chen
- Source: IEE Proceedings - Communications, Volume 151, Issue 1, p. 107 –111
- DOI: 10.1049/ip-com:20040229
- Type: Article
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TCP Vegas detects network congestion in its early stage and successfully prevents the periodic packet loss that usually occurs in traditional schemes. It has been demonstrated that TCP Vegas achieves a much higher throughput than TCP Reno. However, TCP Vegas cannot prevent unnecessary throughput degradation when congestion occurs on the backward path. A router-based congestion avoidance scheme for TCP Vegas is proposed. By distinguishing whether or not congestion occurs in the forward path, it significantly improves the connection throughput when the backward path is congested.
Editorial: Superhighways technology and broadband VPN
IP virtual private networks – a service provider perspective
Framework for dynamic optical virtual private networks (VPNs): architecture and analysis
Enhancing end-to-end QoS granularity in DiffServ networks via service vector and explicit endpoint admission control
Providing flow-based proportional differentiated services in class-based DiffServ routers
Accuracy of measurement techniques supporting QoS in packet-based intranet and extranet VPNs
Partitioning techniques for reducing computational effort of routing in large networks
Traffic engineering enhancement to QoS-OSPF in DiffServ and MPLS networks
Design and performance evaluation of an improved TCP congestion avoidance scheme
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