In this study, the authors propose an optical microwave (MW) radio-over-fibre system in which an integrated dual-parallel Mach–Zehnder modulator (DP-MZM) is biased at the maximum transmission biasing point. A single drive Mach–Zehnder modulator, in series with the DP-MZM, is used to modulate the 1 GHz radio frequency data onto the optical carrier. They characterise the efficiency of the practical system in terms of power penalty and error vector magnitude. Two modulation schemes are investigated, namely binary phase shift keying (BPSK) and quadrature phase shift keying (QPSK) over fibre spans of 10 and 25 km of standard single mode fibre. The results show that the second-order sideband of MW has the potential to provide error free transmission for BPSK and QPSK. The error free communication system is achieved for BPSK at 10 and 25 km fibre spans at optical launch power (OLP) of 7 dBm, whereas for QPSK, the OLP is ∼11 and ∼12 dBm for 10 and 25 km fibre spans, respectively.

The convergence of two popular access technologies, namely Worldwide interoperability for Microwave Access (WiMAX) and passive optical network (PON) is a promising access solution that combines the mobility feature of WiMAX and the ample bandwidth of PONs. In such a converged optical-wireless access network, the provision of quality of service (QoS) support is a challenging issue, mainly because of the different bandwidth allocation mechanisms of the two access technologies. Since the considered convergence seems to be dominant, it deserves assiduous analysis and evaluation. In this study, the authors investigate the delay performance of a converged optical-wireless network that provides QoS support by considering multiple service-classes with different priorities. In the wireless domain, the IEEE 802.16 standard is applied, whereas in the optical domain a wavelength division multiplexing ethernet PON provides connectivity to both wired and wireless users. The authors present an analytical framework for the calculation of the average end-to-end packet delay of each service-class, by developing two queuing models for each domain of the converged network. The end-to-end delay is calculated as the sum of the queuing delay in both domains, and the transmission and propagation delay in the optical domain. The accuracy of the proposed analysis has been verified by simulation and found to be quite satisfactory.

The authors propose a novel traffic prediction method for the minimisation of packet delay in Ethernet passive optical networks. The method relies on traffic monitoring at the optical network units (ONUs) and utilises readily available traffic information to predict the accumulated burst size of each respective ONU in the following cycle. They demonstrate that a significant delay enhancement can be accomplished by reporting the predicted, rather than the current, burst size to the optical line terminal (OLT). The author's simulation results show that a delay improvement of over 25% can be expected by the proposed method without modifying the well-established interleaved polling scheme with adaptive cycle time dynamic bandwidth assignment scheme at the OLT.

This study proposes a new analytical model of a multi-service switching network with overflow links with finite capacity in the first stage of the network. The proposed model assumes that overflow links can service a number of selected call classes from among all classes offered to the network. A particular attention is given to the method for a determination of the effective availability parameter for networks with overflow links. The proposed model can be also used to determine the dependence between the internal blocking probability and the capacity of overflow links. A relevant simulation study has confirmed high accuracy of the proposed method as well as the applicability of the model in engineering practice, in modelling of multi-stage switching networks both optical and electronic.

Managing quality of service (QoS) is an important network operation, especially in hybrid wired and wireless multimedia networks. In this study, a two-stage approach to intelligently manage QoS for multimedia traffic was developed. Voice over Internet protocol (VoIP) was included in the study as an example of a typical multimedia application. Initially an adaptive statistical sampling technique was employed. It determined the traffic's statistics and used them in a fuzzy inference system to determine the optimum interval between every two consecutive sections of the traffic sampled. In the second stage, a fuzzy c-means (FCM) clustering was used to pre-process QoS parameters (delay, jitter and packet loss ratio) obtained from the devised sampling scheme. A multilayer perceptron (MLP) neural network then used the information from FCM to assess the QoS provided for VoIP.

It was shown that the developed adaptive statistical sampling represents the traffic more correctly than the systematic, stratified and random non-adaptive sampling methods. Also, the combination of statistical sampling followed by FCM and MLP accurately indicated the QoS for VoIP.

This study proposes a new method for calculations of the blocking probability in multiservice state-dependent systems. In the method proposed in this study the occupancy distribution is determined on the basis of an appropriately modified convolution operation. This operation is of a universal applicability and provides an opportunity to model approximately any state-dependent systems. The results of the calculations were compared with the results of the simulation experiments of some selected multiservice systems and with the results provided by other analytical methods that are available in the literature of the subject. The study has confirmed high accuracy of the proposed method. The effectiveness of the computational process carried out according to the proposed method can be significantly increased as a result of parallelisation of computation.

In this study, the frequency spectrum of a pulse for ultra wideband impulse radio systems is assumed to be the frequency response of a real valued causal rational infinite impulse response (IIR) filter. This pulse design problem is formulated as a functional inequality constrained optimisation problem. The objective of this optimisation problem is to minimise the sum of the total passband and stopband ripple energy of the pulse. Also, the optimisation problem is subject to the stability condition of the IIR filter as well as to the specifications defined on both the maximum passband and stopband ripple magnitudes and that on the maximum time domain ripple magnitude of the pulse. If the feasible set of the optimisation problem is non-empty, then the designed pulse is guaranteed to be satisfied the specifications suggested by the Federal Communications Commission. Computer numerical simulation results show that the energy compaction performance defined in the frequency domain of the authors’ designed pulse outperforms that of existing pulses. Since the frequency spectrum of the pulse is the same as the frequency response of the designed IIR filter, the pulse can be generated via an excitation of a simple circuit.

To allow users to access networks ubiquitously, more user equipments contain multiple radio transceivers. Because of the proximity of transmit and receive frequencies of in-device wireless technologies, the transmitter (TX) of one in-device wireless technology can interfere with the reception of another technology within the same device, and the spurious emissions of the aggressor TX may result in unacceptable interference at the victim receiver. Hence, it is crucial to detect the in-device interference and adapt strategies to avoid harm. Here, we consider one scenario in 3GPP discussions: the co-existence of Long-Term Evolution (LTE) with WiFi. Different from traditional spectrum sensing which detects signal in the background of Gaussian noise, the WiFi leakage detection in this study aims to detect WiFi leakage in the presence of both LTE signal and noise. Furthermore, most of the WiFi signal features are lost in the WiFi leakage because of the LTE RX filtering which makes the WiFi leakage problem very challenging. By identifying unique features of the WiFi leakage, we investigate this problem thoroughly and propose a suite of detection algorithms, including energy-ratio-based, entropy ratio-based and cyclostationary analysis-based algorithms. Simulations under different scenarios are presented to illustrate the effectiveness and efficiency of the proposed techniques.

In this study, performance of intelligent transportation systems (ITS), which consists of satellite mesh networks, is investigated. These networks are characterised by the absence of the on ground satellite gateway and many power limited user terminals with small antennas which are able to direct connection with a satellite. In such scenario, energy efficiency signals, for example, continuous phase modulation (CPM) should be used for transmission. The authors analyse performance of a mesh ITS which apply multiuser frequency division multiplexed (FDM) transmission with coded CPM via computer simulations. The spectral efficiency of investigated system is improved by reducing the inter-carrier frequency (ICI) spacing and using simple iterative ICI cancellation algorithm at the receiver. The results suggest that FDM CPM transmission might constitute a desirable option in ITS satellite mesh, ad-hoc networks.

In this study the authors present a novel technique for control of signal power transients caused by signal add/drops in optical communication networks with erbium-doped fibre amplifiers (EDFAs). The approach utilises the electronic automatic gain control that combines both feedback and feedforward control of EDFA. Feedback control is non-linear integral control and feedforward control is a steady-state gain scheduling technique. The feedback non-linear control requires information about the average inversion level that is obtained via a simple linearised first-order observer. The scheduling variable used is the nominal pump power needed to keep the average inversion level at the desired value at steady state and the input signal powers given at particular wavelengths. In the simplified gain scheduling version, the scheduling variable is the total input signal power. Simulation examples indicate that the proposed controller completely eliminates at steady state the photon power transients caused by signal add/drops with the steady state being reached within a few milliseconds.