Hussein Charara

Methods for bounding end-to-end delays on an AFDX network

Architectures of avionics networks, such as that of the Airbus A380, currently know important evolutions. This is principally due to the increase in the complexity of the embedded systems, in term of rise in number of integrated functions and their connectivity. The evolution of switched Ethernet technologies allows their implementation as an avionics architecture (AFDX: avionics full duplex switched Ethernet). The problem is then to prove that no frame is lost by the network (no switch queue will overflow) and to evaluate the end-to-end transfer delay through the network. The objective of this paper is to present and shortly compare three methods for the evaluation of end-to-end delays: network calculus, queuing networks simulation and model checking

Modelling and simulation of an avionics full duplex switched Ethernet

Architectures of embedded avionics networks, such as that of the future Airbus A380, currently know important evolutions. This is principally due to the increase in the complexity of the embedded systems, in terms of the rise in the number of integrated functions and their connectivity. The evolution in the technologies of data transmission local area networks makes it possible to convey new answers to airframe manufacturers. In particular, switched Ethernet technologies are being implemented as an avionics architecture, even if the non-deterministic character of certain networks must be compensated by strong assumptions. The paper presents a simulation model for dimensioning an avionics full duplex switched Ethernet network (AFDX) and for studying the performance of this network. Comparison with other deterministic studies which use network calculus is also performed.

Spectrum Sensing for Full-Duplex Cognitive Radio Systems

Full-Duplex (FD) transceiver has been proposed to be used in Cognitive Radio (CR) in order to enhance the Secondary User (SU) Data-Rate. In FD CR systems, in order to diagnose the Primary User activity, SU can perform the Spectrum Sensing while operating. Making an accurate decision about the PU state is related to the minimization of the Residual Self Interference (RSI). RSI represents the error of the Self Interference Cancellation (SIC) and the receiver impairments mitigation such as the Non-Linear Distortion (NLD) of the receiver Low-Noise Amplifier (LNA). In this manuscript, we deal with the RSI problem by deriving, at the first stage, the relation between the ROC curves under FD and Half-Duplex (HD) (when SU stops the transmission while sensing the channel). Such relation shows the RSI suppression to be achieved in FD in order to establish an efficient Spectrum Sensing relatively to HD. In the second stage, we deal with the receiver impairments by proposing a new technique to mitigate the NLD of LNA. Our results show the efficiency of this method that can help the Spectrum Sensing to achieve a closed performance under FD to that under HD.

Spatial and time diversities for canonical correlation significance test in spectrum sensing

In this paper, we present a new detector for cognitive radio system based on the Canonical Correlation Significance Test (CCST). Unlike existing CCST approaches, which can only be applied on Multi-Antenna System (MAS), our algorithm can be extended for both Single Antenna System (SAS) and MAS. For SAS, the proposed algorithm exploits the time diversity of cyclostationary signals in order to detect the Primary User (PU) signal. Our simulation results shows that our algorithm outperforms well-known cyclostationary algorithm [9]. For MAS, our algorithm uses both spatial and time diversities to apply the CCST. Numerical results are given to illustrate the performance of our algorithm and verify its efficiency for special noise cases (spatially correlated and spatially colored). The simulation results show the superiority of the performance of the proposed detector compared to the recently CCST proposed algorithm [1].

Simulation of multipoint to multipoint hierarchy for fast rerouting in Multi Protocol Label Switching networks

Multi-Point to Multi-Point Traffic Engineering (MP2MP-TE) leads to an important scalability in Multi Protocol Label Switching-Traffic Engineering (MPLS-TE) networks. This paper emphasizes on the support of Fast-reroute (FRR) in MPLS-TE networks by using MP2MP bypass TE-tunnels. Hence, one MP2MP bypass TE-tunnel can be used to protect several primary TE-tunnels. During failure, the primary TE-tunnel is encapsulated into the MP2MP bypass TE-tunnel which calls for defining a new type of MPLS hierarchy, i.e. the multipoint to multipoint hierarchy. In this paper we present a simulation study that evaluates several fast rerouting scenarios depending on the number of leaves of a MP2MP bypass TE-tunnel and on the number of primary TE-tunnels that can be encapsulated into one MP2MP bypass TE-tunnel. In particular, the scalability/bandwidth efficiency tradeoff between these schemes is analyzed and valuable comparisons with the existing approaches are presented.

Spectrum Sensing enhancement using Principal Component Analysis

In this paper, Principal Component Analysis (PCA) techniques are introduced in the context of Cognitive Radio to enhance the Spectrum Sensing performance. PCA step increases the SNR of the Primary Users signal and, consequently, enhances the Spectrum Sensing performance. We applied PCA as a combination scheme of a multi-antenna Cognitive Radio system. Analytic results will be presented to show the effectiveness of this technique by deriving the new SNR obtained after applying PCA, which can be considered a pre-processing step for a classical Spectrum Sensing algorithm. The effect of PCA is examined with well known detectors in Spectrum Sensing, where the proposed technique shows its efficiency. The performance of the proposed technique is corroborated through many simulations.

Signalling aspects of optimized inter-domains point to multipoint paths in Multi Protocol Label Switched networks

We propose a method to compute point to multipoint (P2MP) traffic engineered paths that cross several MPLS domains. It relies on the use of multiple Path Computation Elements (PCEs), in the goal of calculating a P2MP tree along a given tree of domains by using a recursive path computation technique. Indeed, the calculation is started by the PCEs of the destination domains, i.e. those ones that are not connected to any domain downstream and it is continued upstream from PCE to PCE until reaching the P2MP tree source. A PCE should determine the total number of paths downstream and send them to an upstream PCE. This is required in order to ensure that the obtained inter domain P2MP tree is optimized, where the optimization criteria is the minimization of the number of links of the tree. A detailed signaling example is hence highlighted and discussed.