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In order to overcome the negotiation procedure bottleneck of the standard DCF in wireless mesh networks, the authors propose a new channel reservation function (CRF) that reduces the negotiation overhead of the DCF, which as a result reduces the overall transmission delay effectively without of any extra bandwidth consumption. Furthermore, the authors provide an analytical model for the proposed scheme for which the simulation results measure the amount that the new method can reduce the average total delay for both regular and fragmented mesh topologies demonstrating superiority of the new method over the classic 802.11 solution. Additionally, the authors extend the scheme to multichannel CRF upon which the proposed method can be used for multichannel applications. [ABSTRACT FROM AUTHOR]

Adaptation of QoS in DWDM optical networks routing and the wavelength assignment (RWA) problem, known as an NP-hard problem, are addressed. The QoS constraint based routing RWA computes lightpaths for the original-destination node pair, (O, D), to meet the QoS propagation delay requirements. A heuristic algorithm based on a genetic algorithm (GA) is then developed to solve this problem. A simulation program is developed to demonstrate the efficiency of the GA for the COST 239 network. The trade-off between the capacity and the propagation delay has been analysed. Results show that the trade-off is 8.7% of the average capacity, increasing to 10.6% decrease for the average delay. [ABSTRACT FROM AUTHOR]

In guaranteed-type applications the bandwidth planning and cost management are two important issues in deployment of optical core networks. A two-stage fuzzy-based approach is proposed for accommodating long-term demand uncertainties in dense wavelength division multiplexing optical networks. Here, the uncertainties are modelled using the Gaussian fuzzy membership functions. First, the forecasted part of demand matrix is introduced to Dijkstra shortest path-based routing algorithm. Then, the available wavelengths are assigned to demand uncertainties. Unlike existing algorithms, different bandwidth cost factors are assigned to the links of a lightpath according to network and links state information. The performance of proposed approach is evaluated on a typical optical link for uncertain traffic loads in Erlang mode. Simulation results show that the proposed fuzzy-based approach is up to 29% cost-effective for accommodating network demands in real-world applications comparing to existing algorithms. [ABSTRACT FROM AUTHOR]

In network virtualisation, which enables multiple virtual routers to share one physical router, how to ensure the scalability and performance of concurrent virtual routers is a challenging problem in virtual router design. Since physical router only has limited memory resource, it is significant to efficiently store multiple forwarding tables for virtual routers. Motivated by the idea of diminishing the dissimilarities in forwarding tables, the authors propose a novel trie shifting scheme with depth adjusting, and finally obtain a memory-efficient shared trie for all forwarding tables. In this scheme, by diminishing the dissimilarity in the depth and in the shape, memory is saved by reducing the trie nodes needed in the shared trie. In the simulation, the scheme needs only 10% of trie nodes, compared with storing forwarding tables separately. Extensive simulation based on three sets of forwarding tables, which are collected from five backbone routers, shows that the scheme saves memory by reducing the number of trie nodes between 4.7 and 7.8%, compared with the latest scheme in related work. Moreover, this scheme achieves more improvement when the dissimilarity is increasing. [ABSTRACT FROM AUTHOR]

Study the effects of concurrent voice connections on the performance metrics of communication network such as queue length, waiting time, packets service time and is very important. Mathematical analysis of such network especially with long-tail traffic will help us for a good capacity planning and also lead to an accurate admission control algorithms. In this study a mathematical model of a communication network supporting VoIP and back-ground traffic with long-tail service time is considered. Some problems of previous mathematical models are identified and a new queueing system is proposed in which specifically the coexisting of heavy-tail and voice flows is addressed. The long-tail service time is approximated via hyper-Erlang distribution and also to achieving an accurate performance model a Markov reward model is introduced. The available bandwidth for long-tail distribution varies according to the Markov chain, describing the utilisation factor of voice connection. Numerical results show a comparison between exponential and heavy-tail service time and finally the effects of concurrent voice connections on the service time of heavy-tailed back-ground packets is shown. [ABSTRACT FROM AUTHOR]

As a potential future technology, impulse radio is a promising new reliable data transmission method for time-sensitive applications. However, owing to the complex nature of ultra-wideband (UWB) channels used in practice, there are many design problems that remain to be resolved. This study looks into some UWB channels classified as waveform distortion for which the authors present an implementation-oriented analysis to investigate the performance of impulse radio systems using antennas for a special class of deterministic multipath channels. This study analyses the waveform distortion along signal path to identify the effect of non-idealities in the system and evaluates overall performance of system in terms of bit error ratio observing the waveforms received at the correlator. Through simulation results practical aspects of the impulse-radio transceivers are discussed. From some of the results, the authors provide an antenna selection strategy for some propagation environments. [ABSTRACT FROM AUTHOR]

In this study, the authors propose a new method for constructing irregular low-density parity-check codes (LDPC codes) with midterm or short block lengths. It is a Monte-Carlo simulation-based optimisation procedure called downhill simplex which uses progressive edge growth method for Tanner graph construction in cost function evaluations. It outperforms the density evolution (DE) method in both efficiency and performance. The efficiency of the authors' proposal mostly depends on the Monte-Carlo simulation time which owing to the midterm block lengths is relatively small compared to the time delay of the conventional DE method. Simulation results show that for block length of 3200 and a relatively low code rate 3/8, LDPC codes constructed using the authors' proposal noticeably outperform those constructed with DE method by more than 0.2 dB in the entire signal to noise ratio (SNR) range under AWGN channel. [ABSTRACT FROM AUTHOR]

In practice, because of their saturating affects, potentially all traditional transmission control protocol (TCP) congestion estimators effectively degrade the operational performance and efficiency of virtually all high-speed networks. Here the authors adopt a novel idea of using queueing-based estimator to estimate the TCP operating points ahead of their occurrence of network congestion. For this purpose the authors employ recent work of packet time-series analysis. In order to demonstrate the effectiveness of the idea, the authors embed the new estimator into several TCP variants in NS-2 and Linux kernel. For this evaluation the authors have programmed the simulation system to simulate a wide range of classic operating environments and setup many practical test-bed emulators for measurements. The authors results show that the idea of using a queueing-based estimator provides us far more earlier, sensitive and consistent estimation for the operating point than the classic loss/delay-based TCP traffic estimators. The authors then show that the new approach improves the overall estimation efficiency and provides higher performance and fairness when monitoring TCP traffic. [ABSTRACT FROM AUTHOR]

Owing to the growing demand for low-cost ‘networkable’ sensors in conjunction with recent developments of micro-electro mechanical system (MEMS) and radio frequency (RF) technology, new sensors come with advanced functionalities for processing and communication. Since these nodes are normally very small and powered with irreplaceable batteries, efficient use of energy is paramount and one of the most challenging tasks in designing wireless sensor networks (WSN). A new energy-aware WSN routing protocol, reliable and energy efficient protocol (REEP), which is proposed, makes sensor nodes establish more reliable and energy-efficient paths for data transmission. The performance of REEP has been evaluated under different scenarios, and has been found to be superior to the popular data-centric routing protocol, directed-diffusion (DD) (discussed by Intanagonwiwat et al. in ‘Directed diffusion for wireless sensor networking’ IEEE/ACM Trans. Netw., 2003, 11(1), pp. 2–16), used as the benchmark. [ABSTRACT FROM AUTHOR]