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Multihop relaying is one of the promising techniques in future generation wireless networks. The adaptive modulation and coding (AMC) mechanisms can be applied in order to increase the spectral efficiency of wireless multihop networks. However, most of these mechanisms concentrate on the physical layer without taking the queuing effects at the data link layer into account, whose performances are overestimated. Therefore the cross-layer analytical framework is presented in analysing the quality-of-service (QoS) performances of the decode-and-forward (DF) relaying wireless networks, where the AMC is employed at the physical layer under the conditions of unsaturated traffic and finite-length queue at the data link layer. Considering the characteristics of DF relaying protocol at the physical layer, the authors first propose modelling a two-hop DF relaying wireless channel with AMC as an equivalent Finite State Markov Chain (FSMC) in queuing analysis. Then, the performances in terms of queuing delay, packet loss rate and average throughput are derived. The numerical results show that the proposed analytical method can be efficiently applied for studying the issues including the relay deployment and the cross-layer design in the multihop relaying networks. [ABSTRACT FROM AUTHOR]

First, the optical burst switching (OBS) network with limited wavelength conversion capability (LWCC) is decomposed into multiple wavelength continuous segments according to the position of wavelength converters. Based on the decomposed network model, two reservation signalling mechanisms for OBS-LWCC networks, namely wavelength-amend-on-demand (WAoD) and contention-based limited signalling protocol (CLSP), are proposed to reduce the blocking probability in the OBS-LWCC networks. In WAoD, the congested node sends a feedback message to the closest upstream switch with wavelength conversion capability. The notified switch will change the burst wavelength to the one assigned by the congested node to avoid collision in advance. Extensive simulation results indicate that by applying the wavelength reconfiguration method to the core nodes without wavelength conversion capability, the proposed WAoD scheme can improve the blocking performance in the OBS-LWCC networks significantly. Furthermore, CLSP, which combines the burst time-slot reconfiguration with the wavelength reconfiguration of WAoD, always has the lowest burst loss probability when compared with both the conventional and the proposed reservation mechanisms. [ABSTRACT FROM AUTHOR]

A strategy for minimising the probability of contention in optical burst-switching (OBS) networks, by combining traffic engineering in the wavelength domain with delayed burst scheduling at the ingress nodes, has been proposed. The implementation of this strategy only requires an increase on the processing and electronic buffering capacities of the ingress nodes, while avoiding the use of complex and expensive optical buffers at the core nodes. The performance evaluation study has shown that the proposed strategy outperforms the burst-scheduling strategies described in the literature by several orders of magnitude, in terms of burst-blocking probability. Moreover, the performance improvements have been shown to depend on the average offered traffic load, number of wavelengths per link and maximum delay allowed at the ingress nodes. [ABSTRACT FROM AUTHOR]

The author evaluates the performance of bufferless optical packet switches equipped with shared tuneable optical wavelength converters (TOWC) and supporting the quality of service (QoS). The TOWCs are shared per output fibre and, hence each output fibre has a dedicated pool of TOWCs. The TOWCs are not completely shared within the node. The QoS, expressed in terms of the packet loss probability, is differentiated by giving the packets different priorities in accessing both the output wavelengths and the TOWCs. A scheduling algorithm is proposed and its complexity is evaluated. The QoS technique's effectiveness is studied by means of an analytical model based on a probabilistic approach and validated by simulation results. The results show that the proposed technique to support the QoS facilitates a good differentiation of the QoS offered to packets. [ABSTRACT FROM AUTHOR]

Most of the previous works on optical burst switching (OBS) assume in their analysis that signalling does not affect network performance. It is analysed here, under which conditions the effect of signalling is actually negligible, taking into account the effect of signalling in the evaluation of burst discard probability. First, analytical models for two different signalling approaches in an OBS network are presented: ‘out-of-band’ and ‘in-band’ techniques. The impact of these two signalling strategies in terms of the probability of burst discard are evaluated, identifying the component of bursts discarded as a consequence of control message losses or of excessive signalling delay. A new method is also discussed, based on the previous models, to assign the correct amount of resources to the control plane. To verify the accuracy of the analytical results, these are compared with results based on discrete-event simulationns: results are found to be in a highly satisfactory agreement with simulations. [ABSTRACT FROM AUTHOR]

In this paper we study the accuracy achievable when using probing to measure packet loss probability. Active monitoring using packet probing is widely used to measure network performance at the packet level, especially where direct measurements from network nodes is not possible. In this paper we develop an analytical solution that allows us to predict the number of samples (probes) needed to measure packet loss probability. This formula relates the number of probes needed to the networking scenario, the traffic characteristics, the target packet loss probability and the accuracy to which this loss probability must be resolved. We show that the number of probes required to accurately measure the packet loss probability is a highly sensitive function of the link bandwidth, the traffic load and burstiness, and the packet loss probability itself. We quantify how many probes are needed in certain typical scenarios involving either VoIP or generic data traffic models. [ABSTRACT FROM AUTHOR]