Wafa Ben Hassen

OMTDR using BER estimation for ambiguities cancellation in ramified networks diagnosis

Nowadays, increasing demands for on-line wire diagnosis using reflectometry have imposed serious challenges on signals processing, bandwidth control and interference mitigation. On-line diagnosis aims at detecting and locating faults accurately while the target system is running. In this work, a new reflectometry method, named “Orthogonal Multi-Tone Time Domain Reflectometry” (OMTDR), is proposed. OMTDR, based on Orthogonal Frequency Division Multiplexing (OFDM), is a suitable candidate for on-line diagnosis as it permits interference avoidance, bandwidth control and data rate increase thanks to the use of orthogonal tones and guard intervals. Over the diagnosis function, OMTDR adds communication between sensors to more accurately determine faults position in a multi-branch network using a distributed strategy. OMTDR was tested on a branched network consisting of three cables with different lengths, with sensors at each cable end. Here, the sensors signals are carefully constructed using a resource allocation scheme to use frequencies below and above the prohibited bandwidth, used by the target system, for communication and diagnosis. Simulation results show that the proposed method performs well in a branched wiring network as it permits to detect and locate faults accurately even when the target system is operating.

Diagnosis sensor fusion for wire fault location in CAN bus systems

This paper proposes a new method for distributed wire diagnosis using reflectometry. It not only uses the reflected part of the test signal to extract information about the fault position, but it also investigates the transmitted part to enable sensors communication. The major novelty is to inject a signal carrying additional information about the fault position as a test signal using Orthogonal Multi-Tone Time Domain Reflectometry (OMTDR) method. While the reflected signal permits to determine the fault position at time t, the transmitted one sends the fault position at time (i-1) to the master sensor. Finally, the latter takes the location decision based on the information gathered from its slaves. This removing location ambiguities in branched networks. Time Division Multiple Access (TDMA) is used to avoid noise interference.

A Gain-Computation Enhancements Resource Allocation for Heterogeneous Service Flows in IEEE 802.16 m Mobile Networks

This paper deals with radio resource allocation in fourth generation (4G) wireless mobile networks based on Orthogonal Frequency Division Multiple Access (OFDMA) as an access method. In IEEE 802.16 m standard, a contiguous method for subchannel construction is adopted in order to reduce OFDMA system complexity. In this context, we propose a new subchannel gain computation method depending on frequency responses dispersion. This method has a crucial role in the resource management and optimization. In a single service access, we propose a dynamic resource allocation algorithm at the physical layer aiming to maximize the cell data rate while ensuring fairness among users. In heterogeneous data traffics, we study scheduling in order to provide delay guaranties to real-time services, maximize throughput of non-real-time services while ensuring fairness to users. We compare performances to recent existing algorithms in OFDMA systems showing that proposed schemes provide lower complexity, higher total system capacity, and fairness among users.

OMTDR based integrated cable health monitoring system SmartCo: An embedded reflectometry system to ensure harness auto-test

This paper presents the first embedded health monitoring system able to analyze network/harness health using OMTDR (Orthogonal Multi-tone Time Domain Reflectometry) technology. OMTDR is a suitable candidate for on-line diagnosis as it permits interference avoidance by bandwidth control. Thanks to OMTDRs communication capability, network analysis as well as sensors intelligence can be easily distributed without any impact on network traffic. Complex network can be analyzed and fault location ambiguity can be solved thanks to distributed analysis. This enables to aggregate diagnosis information from several sensors and make a high level decision. Even for a simple network, OMTDR obtains a better fault location accuracy by combining different location data. In this paper, we analyze the benefit of integrating OMTDR into the harness. The demonstrator embeds both real time distributed wire diagnosis and sensor communication in 2 standard aerospace connectors. Thanks to this intelligence and capability added into commercial connectors, we call this innovative proposed solution: SmartCo for Smart-Connector. Hardware, software and demonstrator interface are presented in details.

Embedded wire diagnosis sensor for intermittent fault location

This paper presents an EMC (Electromagnetic Compatibility) compliant sensor able to detect and locate intermittent faults longer than 300 μs in wires in real time. The proposed System On Chip can diagnose any wire using different reflectometry-based methods. The injected signals spectrum is designed to ensure a continuous harmless diagnosis. The ASIC integrates the whole processing chain, i.e. the analog cells, in particular ADC/DAC, and the digital processing elements based on a custom processing unit (DSP-like) that analyzes in real time the reflected signal. An integrated oversampling system increases the ADC performance more than 20 times, enhancing the location accuracy down to 3 cm. The ASIC was realized in 130 nm TSMC technology and has a surface of 3 mm2. This paper presents intermittent fault detection and location results in a real network.

Smart connectors fusion for incipient defect diagnosis on aging aircraft wiring systems

This paper introduces the first embedded Smart Connector (SmartCo) able to detect and locate incipient defect caused by various origins such as chafing, bending radius, pinching, cable movement, etc., and this even in complex wiring networks. Based on Orthogonal Multi-tone Time Domain Reflec-tometry (OMTDR) technology, the SmartCo uses the test signal not only to generate the reflectometry signal, but also to transmit useful information. To the best of our knowledge the simultaneous combination of communication and cable assessment has never been done with reflectometry-based systems. Our approach permits to aggregate data from a set of slave connectors. These smart connectors are set at strategic points in the network and send their information to the master. Indeed, since incipient defect is hard to distinguish from noise, the master performs an advanced post-processing to eliminate false alarms. A demonstrator has been developed where wire diagnosis and data communication are embedded into a board card.

A Recursive Resource Allocation Algorithm for MIMO-OFDMA Systems in Multi-user Context

This paper presents a new resource allocation algorithm for downlink multi-user MIMO-OFDMA systems. The main objective is to maximize the total system capacity and to guarantee the fairness among users with a low complexity. The proposed algorithm is based on a recursive sub-carriers allocation procedure aiming to satisfy Quality of Service (QoS) requirements for each mobile user. Simulation results demonstrate that the proposed algorithm performs well in terms of system capacity and fairness when the number of users in the cell is important closing to the practical case.

A sliding window method for subchannels gain computation in OFDMA wireless systems: Context IEEE 802.16m

In the IEEE 802.16 recommendations family, the adjacent method for construction of the subchannel is adopted. In order to reduce the system complexity, the available subcarriers are grouped into equal groups of contiguous subcarriers, where each group is called a subchannel. The adaptive modulation and coding schema, AMC, is used in order to maximize the number of bit per symbol. In this case, subcarriers of subchannel present different SNR and the fundamental question is how to choose the best AMC for each subchannel. In this paper, an enhancement algorithm is proposed to response at this question in the context of Orthogonal Frequency Division Multiple Access, OFDMA, wireless systems in the downlink sense. The scheduler located at the base station computes subchannel gain based on the responses frequency dispersion, then the quality of the channel. This gain has a great importance in resource management. Numerical results show that the proposed algorithm outperforms an allocation scheme in terms of a lower BLOC Error Rate (BLER) and a higher system Capacity, compared to others methods.

Adaptive resource allocation scheme using sliding window subchannel gain computation: Context of OFDMA wireless mobiles systems

Multiuser diversity combined with Orthogonal Frequency Division Multiple Access (OFDMA) are a promising technique for achieving high downlink capacities in new generation of cellular and wireless network systems. The total capacity of OFDMA based-system is maximized when each subchannel is assigned to the mobile station with the best channel to noise ratio for that subchannel with power is uniformly distributed between all subchannels. A contiguous method for subchannel construction is adopted in IEEE 802.16 m standard in order to reduce OFDMA system complexity. In this context, new subchannel gain computation method, can contribute, jointly with optimal assignment subchannel to maximize total system capacity. In this paper, two new methods have been proposed in order to achieve a better trade-off between fairness and efficiency use of resources. Numerical results show that proposed algorithms provide low complexity, higher total system capacity and fairness among users compared to others recent methods.

A novel heuristic method for resource allocation in downlink OFDMA systems: Context IEEE 802.16 m

In this paper we have proposed a new heuristic method for subchannels allocation problem in the context of WiMAX release 2.0, IEEE 802.16m. In this system, OFDM transmission method has been used, in order to reduce the effect of multipath fading and OFDMA in order to achieve multiple access schemes and flexibility in resource allocation. An adaptive method for subchannels allocation is necessary in order to exploit the multiuser diversity, to respect real time constraints and to maximize the capacity system. The proposed algorithm is based in the channel state information (CSI) of total mobiles stations present in the cell. The idea of this method is based in the statistic parameters, mean, variance, root mean square or RMS of the gain of frequency response channel for every mobile station. These parameters are the key to organize the different MSs and subchannels priority. Numerical results show that the proposed algorithm outperforms an allocation scheme in terms of Bloc Error Rate, higher system capacity and fairness among active users, compared to others previous methods.