2019 International Conference on Military Communications and Information Systems (ICMCIS), 2019
A realistic troop deployment scenario for tactical MANET was developed within the NATO IST-124. T... more A realistic troop deployment scenario for tactical MANET was developed within the NATO IST-124. The NAT0 IST-150, which relies on Anglova for benchmarking, has recognized a potential drawback in a subset of this scenario: there is a lack of long (> 4) multi-hop paths. Our contribution confirms this drawback using, for the first time, to the best of our knowledge, EMANE emulations based on realistic TDMA radio models combined with the OLSRd implementations. In addition, we propose a scenario, called 1km-chain, which is shown to be quite challenging for low power radios and might be of interest for future profiling of MANET performances. Our 1kmchain scenario simply modifies the Anglova Company 1 scenario based on stopping particular nodes and on using a dual-slope propagation model.
279 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1988.The communication channel ... more 279 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1988.The communication channel established with HF waves reflected by the ionosphere is investigated. The background ionosphere is modeled by a horizontally stratified medium. This model is superimposed with random irregularities. The resulting channel is characterized by a random transfer function. Each frequency component of this transfer function is determined from the received wave field, knowing the transmitted wave field. The computation of the random fluctuations of the received wave field is performed by using the phase screen-diffraction layer method. This scheme simulates the propagation of an HF wave in the turbulent ionosphere. Based on the forward-scatter approximation, the scheme computes sequentially the effects of phase fluctuations due to the irregularities and the effects of diffraction due to phase mixing. Stepping along the ray path, phase fluctuations are imbedded into a number of phase screens. Diffraction effects are then computed between phase screens using FFT techniques. Special attention is given to the reflection region where the classical WKB approximations are invalid. The simulated received wave field is processed to determine some of the skywave channel characteristics. The computed statistics of the received signal include probability distribution, power spectrum, correlation function and scintillation index. For communication purposes, the pulse distortion is of major interest. The two-frequency mutual coherence function is computed to determine the statistical behavior of the received signal. The coherence bandwidth resulting from this computation is used to assess the ionospheric effects on HF spread spectrum systems.Ope
2011 15th International Conference on Intelligence in Next Generation Networks, 2011
The Universal Postal Union is motivated to develop a new platform: .post, to offer digital servic... more The Universal Postal Union is motivated to develop a new platform: .post, to offer digital services secured from SPAM and cybercriminal activities such as phishing and identity theft. Assuming that strong authentication, network security and QoS must be offered on the international .post platform, the use of national authentication tokens and IMS (IP Multimedia Subsystem) networks is proposed and discussed. A prototype architecture for the .post platform is proposed and the development of an IMS/SIP client to enable the exchange of secured and authenticated mail is described as a sample service to demonstrate the feasibility of the concept.
Proceedings of the Third International Workshop on the Web of Things, 2012
ABSTRACT With the generalization of network-enabled devices such as smart phones, slate computers... more ABSTRACT With the generalization of network-enabled devices such as smart phones, slate computers and tablets, new challenges await the eHealth research community. Indeed, these devices should not only integrate seamlessly into the daily workflow, but their usage must appear as ordinary as possible to the different caregivers. Using RESTful architectures, it is possible to model custom objects in the health domain as resources, interact with them and combine them to mashup applications, enhancing and facilitating in a natural way the work of caregivers. We claim that embedding eHealth workflows into the Web of Things is not only possible, but even enhances the whole process. An alert is no more an isolated event, but becomes connected to other resources providing additional information about its general context. In this paper, we illustrate some of the challenges of bringing REST to the eHealth domain by studying an existing hospital laboratory alerts system and by proposing to generalize it in order to encompass the whole escalating process and exchanges of information among caregivers, patients and their medical records.
We consider an interface between dielectric and semiconductor semispaces, curved along the direct... more We consider an interface between dielectric and semiconductor semispaces, curved along the direction of propagation and infinite in the transverse direction. The semiconductor is magnetically polarized in the Voigt configuration. We give approximate expressions for the loss due to curvature.
The Radio Access Network (RAN) architecture evolves with different generations of mobile communic... more The Radio Access Network (RAN) architecture evolves with different generations of mobile communication technologies and forms an indispensable component of the mobile network architecture. The main component of the RAN infrastructure is the base station, which includes a Radio Frequency unit and a baseband unit. The RAN is a collection of base stations connected to the core network to provide coverage through one or more radio access technologies. The advancement towards cloudnative networks has led to centralizing the baseband processing of radio signals. There is a trade-off between the advantages of RAN centralization (energy efficiency, power cost reduction, and the cost of the fronthaul) and the complexity of carrying traffic between the data processing unit and distributed antennas. 5G networks hold high potential for adopting the centralized architecture to reduce maintenance costs while reducing deployment costs and improving resilience, reliability, and coordination. Incorp...
The proactive routing algorithm OLSRd2 is popular in MANETs. The OLSRd2 routes are based on a Dir... more The proactive routing algorithm OLSRd2 is popular in MANETs. The OLSRd2 routes are based on a Directional Air Time (DAT) metric that can be computed in several ways: three options have been considered here. For benchmarking with respect to the best possible performances, a so-called Omniscient Dijkstra Routing (ODR) algorithm is proposed. An investigation of the performance results of an acknowledged message service for a 24-node MANET using TDMA radios and OLSRd2 is presented. Round Trip Time and message Completion Ratio are computed based on real time emulations using the open-source EMANE framework. The emulated nodes move according to the realistic open-source Anglova scenario. A simple urban scenario with static nodes is also considered for comparison purpose. The preliminary investigations show that improving OLSRd2 is possible but appears to be very challenging as no single option stand out.
2020 International Symposium on Networks, Computers and Communications (ISNCC)
Inspired from the microfacets theory based BRDF models used in computer graphics, the reciprocal,... more Inspired from the microfacets theory based BRDF models used in computer graphics, the reciprocal, energy conserving Walter et al.’s GGX directional factor is proposed to complement the usual scattering and reflection models for radio propagation. A single formulation of the E field is derived to fit the well-known expressions spanning from the specular reflection from a large smooth surface to the Lambertian scattering from a very rough surface. Near the specular direction, the proposed formulation is similar to the Phong and Degli-Esposti’s directional models. This similarity is exploited to propose a simplification of the directional model. The GGX based formulation has two fitting parameters related to the material and the roughness of the facets. Preliminary comparisons with published measurements are encouraging.
1983 Eighth International Conference on Infrared and Millimeter Waves, 1983
We present here the first results of an analytical and numerical study of a five-region planar ca... more We present here the first results of an analytical and numerical study of a five-region planar canonical structure which models non-reciprocal devices for the near-millimeter wave range using surface magnetoplasmon modes. The model includes two slabs of high quality semiconducting material, such as n-GaAs, independently magnetized parallel to the interfaces and perpendicular to the direction of propagation. This analysis in an extension of the one performed in reference 1. Emphasis is placed on a discussion of the results and we suggest directions for further research.
2020 International Symposium on Networks, Computers and Communications (ISNCC), 2020
A Q-learning solution called OLSR-Q was proposed and tuned by McAuley et al. in 2012 to improve t... more A Q-learning solution called OLSR-Q was proposed and tuned by McAuley et al. in 2012 to improve the performance of Optimized Link State Routing (OLSR) using a TDMA MANET simulation and a testbed with real WiFi cards. Here, the use of either IEEE802.11 or TDMA radios are compared using real time emulations based on the open source EMANE platform implemented on a cluster of virtual machines. The open source OLSRd and newer OLSRd2 are analyzed and compared to our implementation called OLSRd2-Q2 of the OLSR-Q algorithm. The benefit of our OLSRd2-Q2 is clear when using TDMA radios but not when using IEEE802.11 radios. These preliminary results confirm the potential and the practical challenges of cognitive approaches to improve the MANET performance of the open source implementation OLSRd2.
2015 9th European Conference on Antennas and Propagation (EuCAP), 2015
The dense multipath components (DMCs) are non-resolvable distributed multipaths on the spatio-tem... more The dense multipath components (DMCs) are non-resolvable distributed multipaths on the spatio-temporal domain that cannot be modeled as specular propagation paths. The specular paths are modeled by ray-optical propagation, while the DMCs originates from electromagnetic field scattering and are diffusive. The DMCs have a significant impact on multiple-antenna link performance. This paper presents a DMC add-on for the existing implementation of COST 2100 channel model in MATLAB. The DMC implementation is based on a geometrical approach which is simple and consistent with the specular path modeling. In the delay domain, the DMCs are associated with an exponentially decaying power delay profile. Whereas in the angular domain, DMCs are dropped uniformly in an extended three-dimensional ellipsoid of the specular cluster so that they are centered at the same angles as specular paths but with wider angular spread. Parametric study of the DMC shows its implication on the delay spread of wide...
One of the several challenges for high capacity wireless communications is to find propagation mo... more One of the several challenges for high capacity wireless communications is to find propagation models able to predict as easily and accurately as possible the propagation channel to assess the performance of wide-band wireless systems. An investigation of simple propagation models using detailed point cloud topographical data available in Switzerland is conducted. Our point cloud based predictions are compared to measurements in 2 ways: wide band impulse response at VHF in hilly terrain and 5GHz-WiFi outdoor picocell connectivity. The preliminary results contribute to the assessment of the potential, but also the current limitations of using precise maps but simple propagation models to predict measurements.
2021 International Conference on Military Communication and Information Systems (ICMCIS), 2021
In MANETs, congestion typically occurs on the interconnecting nodes between two or more groups of... more In MANETs, congestion typically occurs on the interconnecting nodes between two or more groups of nodes. Routing to avoid the congested nodes via alternate, perhaps longer paths, allows more throughput, e.g., 50% more in the canonical 9-node 2-ring scenario. OLSR-Q is based on the routing protocol OLSR and a reinforcement learning (RL) agent to learn the most appropriate link states or "Directional Air Time" metric to avoid the congested nodes. The challenges for the RL agent are (1) to avoid congestion before packets are dropped and (2) to minimize the number of real valued or discrete observations or states. In this paper, three simplified OLSRd2-Qx versions are presented and compared to OLSRd2 and a centralized ODRb, Omniscient Dijkstra Routing-balanced, algorithm. The proposed OLSRd2-Qload algorithm provides the expected 50% increase in throughput on the 9-node 2-ring scenario with a specific test traffic scenario. On the NATO IST-124 Anglova scenario, and using an acknowledged message application, the Q-learning agents remain to be improved. The superior results of the centralized load balancing approach taken in ODRb will be investigated to train multi-agents systems including OLSR-Q.
2019 International Conference on Military Communications and Information Systems (ICMCIS), 2019
A realistic troop deployment scenario for tactical MANET was developed within the NATO IST-124. T... more A realistic troop deployment scenario for tactical MANET was developed within the NATO IST-124. The NAT0 IST-150, which relies on Anglova for benchmarking, has recognized a potential drawback in a subset of this scenario: there is a lack of long (> 4) multi-hop paths. Our contribution confirms this drawback using, for the first time, to the best of our knowledge, EMANE emulations based on realistic TDMA radio models combined with the OLSRd implementations. In addition, we propose a scenario, called 1km-chain, which is shown to be quite challenging for low power radios and might be of interest for future profiling of MANET performances. Our 1kmchain scenario simply modifies the Anglova Company 1 scenario based on stopping particular nodes and on using a dual-slope propagation model.
279 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1988.The communication channel ... more 279 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1988.The communication channel established with HF waves reflected by the ionosphere is investigated. The background ionosphere is modeled by a horizontally stratified medium. This model is superimposed with random irregularities. The resulting channel is characterized by a random transfer function. Each frequency component of this transfer function is determined from the received wave field, knowing the transmitted wave field. The computation of the random fluctuations of the received wave field is performed by using the phase screen-diffraction layer method. This scheme simulates the propagation of an HF wave in the turbulent ionosphere. Based on the forward-scatter approximation, the scheme computes sequentially the effects of phase fluctuations due to the irregularities and the effects of diffraction due to phase mixing. Stepping along the ray path, phase fluctuations are imbedded into a number of phase screens. Diffraction effects are then computed between phase screens using FFT techniques. Special attention is given to the reflection region where the classical WKB approximations are invalid. The simulated received wave field is processed to determine some of the skywave channel characteristics. The computed statistics of the received signal include probability distribution, power spectrum, correlation function and scintillation index. For communication purposes, the pulse distortion is of major interest. The two-frequency mutual coherence function is computed to determine the statistical behavior of the received signal. The coherence bandwidth resulting from this computation is used to assess the ionospheric effects on HF spread spectrum systems.Ope
2011 15th International Conference on Intelligence in Next Generation Networks, 2011
The Universal Postal Union is motivated to develop a new platform: .post, to offer digital servic... more The Universal Postal Union is motivated to develop a new platform: .post, to offer digital services secured from SPAM and cybercriminal activities such as phishing and identity theft. Assuming that strong authentication, network security and QoS must be offered on the international .post platform, the use of national authentication tokens and IMS (IP Multimedia Subsystem) networks is proposed and discussed. A prototype architecture for the .post platform is proposed and the development of an IMS/SIP client to enable the exchange of secured and authenticated mail is described as a sample service to demonstrate the feasibility of the concept.
Proceedings of the Third International Workshop on the Web of Things, 2012
ABSTRACT With the generalization of network-enabled devices such as smart phones, slate computers... more ABSTRACT With the generalization of network-enabled devices such as smart phones, slate computers and tablets, new challenges await the eHealth research community. Indeed, these devices should not only integrate seamlessly into the daily workflow, but their usage must appear as ordinary as possible to the different caregivers. Using RESTful architectures, it is possible to model custom objects in the health domain as resources, interact with them and combine them to mashup applications, enhancing and facilitating in a natural way the work of caregivers. We claim that embedding eHealth workflows into the Web of Things is not only possible, but even enhances the whole process. An alert is no more an isolated event, but becomes connected to other resources providing additional information about its general context. In this paper, we illustrate some of the challenges of bringing REST to the eHealth domain by studying an existing hospital laboratory alerts system and by proposing to generalize it in order to encompass the whole escalating process and exchanges of information among caregivers, patients and their medical records.
We consider an interface between dielectric and semiconductor semispaces, curved along the direct... more We consider an interface between dielectric and semiconductor semispaces, curved along the direction of propagation and infinite in the transverse direction. The semiconductor is magnetically polarized in the Voigt configuration. We give approximate expressions for the loss due to curvature.
The Radio Access Network (RAN) architecture evolves with different generations of mobile communic... more The Radio Access Network (RAN) architecture evolves with different generations of mobile communication technologies and forms an indispensable component of the mobile network architecture. The main component of the RAN infrastructure is the base station, which includes a Radio Frequency unit and a baseband unit. The RAN is a collection of base stations connected to the core network to provide coverage through one or more radio access technologies. The advancement towards cloudnative networks has led to centralizing the baseband processing of radio signals. There is a trade-off between the advantages of RAN centralization (energy efficiency, power cost reduction, and the cost of the fronthaul) and the complexity of carrying traffic between the data processing unit and distributed antennas. 5G networks hold high potential for adopting the centralized architecture to reduce maintenance costs while reducing deployment costs and improving resilience, reliability, and coordination. Incorp...
The proactive routing algorithm OLSRd2 is popular in MANETs. The OLSRd2 routes are based on a Dir... more The proactive routing algorithm OLSRd2 is popular in MANETs. The OLSRd2 routes are based on a Directional Air Time (DAT) metric that can be computed in several ways: three options have been considered here. For benchmarking with respect to the best possible performances, a so-called Omniscient Dijkstra Routing (ODR) algorithm is proposed. An investigation of the performance results of an acknowledged message service for a 24-node MANET using TDMA radios and OLSRd2 is presented. Round Trip Time and message Completion Ratio are computed based on real time emulations using the open-source EMANE framework. The emulated nodes move according to the realistic open-source Anglova scenario. A simple urban scenario with static nodes is also considered for comparison purpose. The preliminary investigations show that improving OLSRd2 is possible but appears to be very challenging as no single option stand out.
2020 International Symposium on Networks, Computers and Communications (ISNCC)
Inspired from the microfacets theory based BRDF models used in computer graphics, the reciprocal,... more Inspired from the microfacets theory based BRDF models used in computer graphics, the reciprocal, energy conserving Walter et al.’s GGX directional factor is proposed to complement the usual scattering and reflection models for radio propagation. A single formulation of the E field is derived to fit the well-known expressions spanning from the specular reflection from a large smooth surface to the Lambertian scattering from a very rough surface. Near the specular direction, the proposed formulation is similar to the Phong and Degli-Esposti’s directional models. This similarity is exploited to propose a simplification of the directional model. The GGX based formulation has two fitting parameters related to the material and the roughness of the facets. Preliminary comparisons with published measurements are encouraging.
1983 Eighth International Conference on Infrared and Millimeter Waves, 1983
We present here the first results of an analytical and numerical study of a five-region planar ca... more We present here the first results of an analytical and numerical study of a five-region planar canonical structure which models non-reciprocal devices for the near-millimeter wave range using surface magnetoplasmon modes. The model includes two slabs of high quality semiconducting material, such as n-GaAs, independently magnetized parallel to the interfaces and perpendicular to the direction of propagation. This analysis in an extension of the one performed in reference 1. Emphasis is placed on a discussion of the results and we suggest directions for further research.
2020 International Symposium on Networks, Computers and Communications (ISNCC), 2020
A Q-learning solution called OLSR-Q was proposed and tuned by McAuley et al. in 2012 to improve t... more A Q-learning solution called OLSR-Q was proposed and tuned by McAuley et al. in 2012 to improve the performance of Optimized Link State Routing (OLSR) using a TDMA MANET simulation and a testbed with real WiFi cards. Here, the use of either IEEE802.11 or TDMA radios are compared using real time emulations based on the open source EMANE platform implemented on a cluster of virtual machines. The open source OLSRd and newer OLSRd2 are analyzed and compared to our implementation called OLSRd2-Q2 of the OLSR-Q algorithm. The benefit of our OLSRd2-Q2 is clear when using TDMA radios but not when using IEEE802.11 radios. These preliminary results confirm the potential and the practical challenges of cognitive approaches to improve the MANET performance of the open source implementation OLSRd2.
2015 9th European Conference on Antennas and Propagation (EuCAP), 2015
The dense multipath components (DMCs) are non-resolvable distributed multipaths on the spatio-tem... more The dense multipath components (DMCs) are non-resolvable distributed multipaths on the spatio-temporal domain that cannot be modeled as specular propagation paths. The specular paths are modeled by ray-optical propagation, while the DMCs originates from electromagnetic field scattering and are diffusive. The DMCs have a significant impact on multiple-antenna link performance. This paper presents a DMC add-on for the existing implementation of COST 2100 channel model in MATLAB. The DMC implementation is based on a geometrical approach which is simple and consistent with the specular path modeling. In the delay domain, the DMCs are associated with an exponentially decaying power delay profile. Whereas in the angular domain, DMCs are dropped uniformly in an extended three-dimensional ellipsoid of the specular cluster so that they are centered at the same angles as specular paths but with wider angular spread. Parametric study of the DMC shows its implication on the delay spread of wide...
One of the several challenges for high capacity wireless communications is to find propagation mo... more One of the several challenges for high capacity wireless communications is to find propagation models able to predict as easily and accurately as possible the propagation channel to assess the performance of wide-band wireless systems. An investigation of simple propagation models using detailed point cloud topographical data available in Switzerland is conducted. Our point cloud based predictions are compared to measurements in 2 ways: wide band impulse response at VHF in hilly terrain and 5GHz-WiFi outdoor picocell connectivity. The preliminary results contribute to the assessment of the potential, but also the current limitations of using precise maps but simple propagation models to predict measurements.
2021 International Conference on Military Communication and Information Systems (ICMCIS), 2021
In MANETs, congestion typically occurs on the interconnecting nodes between two or more groups of... more In MANETs, congestion typically occurs on the interconnecting nodes between two or more groups of nodes. Routing to avoid the congested nodes via alternate, perhaps longer paths, allows more throughput, e.g., 50% more in the canonical 9-node 2-ring scenario. OLSR-Q is based on the routing protocol OLSR and a reinforcement learning (RL) agent to learn the most appropriate link states or "Directional Air Time" metric to avoid the congested nodes. The challenges for the RL agent are (1) to avoid congestion before packets are dropped and (2) to minimize the number of real valued or discrete observations or states. In this paper, three simplified OLSRd2-Qx versions are presented and compared to OLSRd2 and a centralized ODRb, Omniscient Dijkstra Routing-balanced, algorithm. The proposed OLSRd2-Qload algorithm provides the expected 50% increase in throughput on the 9-node 2-ring scenario with a specific test traffic scenario. On the NATO IST-124 Anglova scenario, and using an acknowledged message application, the Q-learning agents remain to be improved. The superior results of the centralized load balancing approach taken in ODRb will be investigated to train multi-agents systems including OLSR-Q.
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Papers by Fred Wagen