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This is the peer reviewed version of the following article: [Font-Bach, O., Bartzoudis N., Pascual-Iserte, A., Payaró M., Blanco L., López Bueno D., and Molina M. (2015) Interference management in LTE-based HetNets: a practical approach, Trans. Emerging Tel. Tech., 26, 195–215, doi: 10.1002/ett.2833.], which has been published in final form at [http://onlinelibrary.wiley.com/doi/10.1002/ett.2833/epdf]. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving. Interference is a major obstacle in radio communications, especially when opportunistic frequency reuse is an inherent requirement for maximising spectral ef¿ciency in heterogeneous networks. A typical example is encountered in cellular communications where macrocell-edge users receive interference from small cell transmissions that use the same radio frequency band. Innovating interference management algorithms are employed towards this end, which because of their interdependencies with numerous parameters of the target operating scenario and various low-level implementation aspects, need to be prototyped in real-time signal processing platforms in order to be credibly veri¿ed. In this paper, we present the development and experimental validation of a macrocell/femtocell coexistence scenario in close to real-life conditions. The inclusion of an agile interference management scheme increased the signal processing complexity at the physical layer. This overhead was appropriately addressed by engaging advanced parallel processing techniques, optimisations of the arithmetic operations and intelligent reuse of logic and memory resources in the ¿eld programmable gate array (FPGA)-based baseband processing architecture

Silicon-photonics bus and ring networks-on-chip are evaluated in terms of transfer function and bit error rates at 10Gb/s, demonstrating that the ring architecture can be effectively used with physical layer performance similar to the bus.

Privacy and security have an increasingly important role in wireless networks. A secure communication enables a legitimate destination to successfully retrieve information sent by a source, while it disables the eavesdropper (illegitimate destination) to interpret the intercepted information. Physical (PHY) layer security approaches for wireless communications can prevent eavesdropping without encryption. It exploits the physical characteristics of the wireless channel in order to transmit messages securely. They are typically feasible when the source-destination channel is better than the source-eavesdropper channel. Cooperative schemes are a means to improve the performance of secure wireless communications. We propose an improved relay selection scheme, based on source-eavesdropper channel SNR restriction, that will guarantee the best secrecy rate at the destination under QoS condition. Performance has been studied in terms of secrecy rate, outage probability and average error probability. Simulations shows that the proposed scheme outperforms in terms of the secrecy rate at the destination when compared to techniques in the literature. Scopus

Cataloged from PDF version of article. In this paper, we introduce BilMesh, an indoor 802.11 b/g mesh networking testbed we established, and we report about our performance experiments conducted on multi-hop topologies with single-radio and multi-radio relay nodes. We investigate and report the effects of using multi-radio, multi-channel relay nodes in the mesh networking infrastructure in terms of network and application layer performance metrics. We also study the effects of physical channel separation on achievable end-to-end goodput perceived by the applications in the multi-radio case by varying the channel separation between the radio interfaces of a multi-radio relay node. We have observed that the difference between TCP and UDP goodput performances together with the delay and jitter performance depends on the hop count. We also observed that assigning overlapping channels with a central frequency separation of 5-15 MHz may render the CSMA mechanism used in 802.11 MAC ineffective and hence reduce the overall network performance. Finally, we provide some suggestions that can be considered while designing related protocols and algorithms to deal with the observed facts. (C) 2013 Elsevier Ltd. All rights reserved.

Physical layer security protocols exploit inviolable physical laws at the signal level for providing guarantees on secrecy of communications. These protocols invariably involve randomized encoding at the transmitter, for which an ideal random number generator is typically assumed in the literature. In this work, we study the impact of using weak Pseudo Random Number Generators (PRNGs) in physical layer security protocols for coding and forward key distribution over Binary Symmetric and Gaussian wiretap channels. In the case of wiretap channel coding, we study fast correlation attacks that aim to retrieve the initial seed used in the PRNGs. Our results show that randomized coset encoding, which forms an important part of wiretap channel coding, provides useful robustness against fast correlation attacks. In the case of single-round or forward key distribution over a Gaussian wiretap channel, the bits from a PRNG are nonlinearly transformed to generate Gaussian-distributed pseudo random numbers at the transmitter. In such cases, we design modified versions of the fast correlation attacks accounting for the effects of the nonlinear transformation and soft input. We observe that, even for moderately high memory, the success probability of the modified fast correlation attacks become the same as that of a random guess in many cases. � 2014 IEEE.

We present a novel cross layer approach to random access (RA) that combines physical-layer network coding (PLNC) with multiuser detection (MUD). PLNC and MUD are applied jointly at the physical level in order to extract any linear combination of messages experiencing a collision. The set of combinations extracted from a whole frame is then processed by the receiver to recover the original packets. A simple pre-coding stage at the transmitting terminals allows the receiver to further increase system diversity. We derive an analytical bound on the system throughput and present simulation results for the decoding at the physical level as well as several performance measures at frame level in block fading channels, namely throughput, packet loss rate and energy efficiency. The results we present are promising and suggest that a cross layer approach leveraging on the joint use of PLNC and MUD can significantly improve the performance of RA systems.

In recent years, there have been increasing demands for the security of wireless multimedia applications. Essentially, wireless networks, compared to traditional wired networks, are more likely to suffer from malicious attacks. Most current security methods consider physical layer and application layer security technologies independently and separately. Usually, physical layer information is dynamic in wireless networks, and application layer information is related to wireless multimedia delivery. Importantly, both of them have significant impact on security performance. In this work, we propose a joint framework involving both the physical and application layer security technologies. Specifically, by exploiting the security capacity and signal processing technologies at the physical layer and the authentication and watermarking strategies at the application layer, the available network resources can be utilized efficiently. In addition, scalable multimedia security services can be maximized within the given multimedia delivery deadlines. In particular, this joint scheme can be implemented easily with low communication overhead, which facilitates its deployment in large-scale wireless multimedia systems. 2014 IEEE. Scopus 2-s2.0-84896912180

In this paper, we consider Doppler compensation for time varying underwater acoustic channels. The underlying system model comprises two sources, S1 and S2, communicating with each other through a relay, R. The transmission process goes through two phases. In the first phase, the two sources transmit simultaneously and the relay receives. In the second phase, the relay processes the received signals and broadcasts the combined signal to the destinations, i.e., sources. The underlying channels are considered to be time varying frequency selective channels, where the only source of time variation is the relative motion between the transceivers. Orthogonal frequency division multiplexing (OFDM) is used as a means to combat frequency selectivity. Two cases are considered, namely, when R uses multiple resampling (MR) preprocessing to reduce the effect of intercarrier interference (ICI) resulting from the time variation, and when R uses single resampling (SR) preprocessing. In both cases, in the second phase of transmission, each source performs MR preprocessing and after subtracting its own signal ICI equalization is performed to further reduce the effect of residual ICI. Simulation results show that performing MR at R outperforms the case when SR is used at R, however, this comes at the expense of more hardware complexity. Grant NPRP 09-126-2-054 from the Qatar National Research Fund (a member of Qatar Foundation). Scopus

Within the paradigm of physical layer secrecy, typically a physical layer specific characteristic is used as key generator to guarantee information hiding from eavesdroppers. In this paper, we propose a novel secret key generation algorithm based on two reciprocal physical layer parameters; the channel measurements and the distances between the two communicating nodes. The two parameters are estimated experimentally using implementations of our algorithm on three FPGA-based WARP kits emulating the two communicating nodes and the eavesdropper. The parameters are used as common sources of randomness to generate the secret key. We evaluate the performance of our algorithm through extensive iterations. We compare the bit mismatch rate as well as the entropy of the generated secret key of our algorithm versus classical channel only and distance only based algorithms. Our results reveal that even in the worst case scenarios, our algorithm outperforms the two other algorithms and overcomes their vulnerabilities. 2014 IEEE. Scopus

Mobile Health (mHealth) systems leverage wireless and mobile communication technologies to provide healthcare stakeholders with innovative tools and solutions that can revolutionize healthcare provisioning. Body Area Sensor Networks (BASNs) is part of the mHealth system that focuses on the acquisition by a group of biomedical sensors of vital signals. However, the design and operation of BASNs are challenging, because of the limited power and small form factor of biomedical sensors. The source encoding and data transmission are the two dominant power-consuming operations in wireless monitoring system. Therefore, in this paper, a cross-layer framework that aims at minimizing the total energy consumption subject to delay and distortion constraints is proposed. The optimal encoding and transmission energy are computed to minimize the energy consumption in a delay constrained wireless BASN. This cross-layer framework is proposed, across Application-MAC-Physical layers. At large scale networks and due to heterogeneity of wireless BASNs, centralized cross-layer optimization becomes less efficient and more complex. Therefore, a distributed cross-layer optimization has been considered in this paper. The proposed solution has close-to-optimal performance with lower complexity. Simulation results show that the distributed scheme achieves the compromise between complexity and efficiency in energy consumption compared to centralized scheme. 2014 IFIP. Scopus

It was well known from Shannon's days that characteristics of the physical channel like attenuation, fading and noise can impair reliable communication. But it was more recently that the beneficial side effects of channel characteristics in ensuring secret communication started getting attention. Studies have been made to quantify the amount of secrecy that can be reaped by combining channel coding with security protocols. The Wiretap channel proposed by Wyner is arguably one of the oldest models of physical layer security protocols. In this paper, we present a brief tutorial introduction to the Wiretap channel, followed by an application of the physical layer model to a class of Key Distribution protocols. We present results from an implementation of key distribution protocols using Software Defined Radio tools along with physical RF hardware peripherals. We believe this approach is much more tangible and informative than computer based simulation studies. � 2013, DESIDOC.

Machine-to-machine networks are spreading over every sector of our society due to their self-organisation capabilities. In these networks, thousands of devices are left unattended for years of operation without the possibility of human intervention. In this sense, every step forward into avoiding early exhaustion of the network nodes is of paramount importance. We have introduced a novel authentication scheme that is able to discard non-intended and/or non-legitimate packets just after the reception of the physical preamble. This proposal was shown to yield enormous energy saving with regard to both node exhaustion attacks and normal network operation. In this paper, we extend that work with a novel synchronization protocol that addresses previous desynchronisation issues. Besides, we analyse and propose the more appropriate deployment parameters that maximise the overall energy savings. We also detail the necessary key generation and key updating processes required to manage the in use keying material. Moreover, we show how to fit the proposed mechanism into the IEEE 802.15.4e amendment to the IEEE 802.15.4-2006 standard, as many companies have decide to go for this technology for the development of machine-to-machine networks. © 2013 John Wiley & Sons, Ltd.

We consider heterogeneous cellular networks (HetNet) where each base station (BS) sends unique training signal based on its physical layer cell identity. Received signal at mobile terminal (MT) is superposition of training signals from different BS. Neither BS identities nor their channel response is known apriori at MT. For this scenario, we consider the problem of finding constituent BS identities from superimposed components in received signal. Though number of BS with unique identities can be quite large in a HetNet, in any given scenario, actual number of BS interfering at MT is relatively few. By exploiting this sparseness, we show that our problem can be solved using block sparse signal reconstruction algorithms under compressive sensing framework where sensing matrix is block-matrix with circulant-blocks (BCB). We apply convex programming based l2l1 mixed norm minimization and greed based subspace matching pursuit approaches to recover interfering BS identities. We characterize block restricted isometry property, mutual subspace incoherence of BCB matrices with i.i.d. Rademacher distributed entries and establish certain recovery guarantees. Our proposed approaches give significant improvements over conventional successive interference cancellation approach over both randomly generated and 3GPP-LTE training signals. � 1972-2012 IEEE.

Body Area Sensor Networks (BASNs) for healthcare applications have gained significant research interests recently due to the growing number of patients with chronic diseases requiring constant monitoring. Because of the limited power source and small form factors, BASNs have distinguished design and operational challenges, particularly focusing on energy optimization. In this paper, an Energy-Delay-Distortion cross-layer design that aims at minimizing the total energy consumption subject to data delay deadline and distortion threshold constraints is proposed. The optimal encoding and transmission energy are computed to minimize the total energy consumption in a delay constrained wireless body area sensor network. This cross-layer framework is proposed, across Application-MAC-Physical layers, under a constraint that all successfully received packets must have their delay smaller than their corresponding delay deadline and with maximum distortion less than the application distortion threshold. Due to the complexity of the optimal-proposed solution, sub-optimal solutions are also proposed. These solutions have close-to-optimal performance with lower complexity. In this context, there is complexity/energy-consumption trade-off, as shown in the simulation results. 2013 IEEE. Qatar National Research Fund Scopus

In recent years, sensor networks characteristics have led to incremental utilization in different types of applications. Several techniques have been proposed to evaluate the performance of WSNs the two most popular being mathematical analysis and simulations. An important drawback of these techniques is that they provide evaluation results that usually are not similar to those of real deployments. One reason for this is the fact that both techniques introduce physical layer modeling assumptions, which do not usually corresponded to real-life environments. In this paper, we used measurements from an industrial environment to develop a new radio propagation model for use in simulators and mathematical tools. The proposed radio model was implemented in the COOJA simulator and validated against real-life results obtained from a testbed inside a running oil refinery, which were found not to conform to any legacy radio propagation model. The proposed model has been shown to successfully match the refinery testbed behavior. 125 131 Sponsors: ACM SIGSIM Conference code: 93968 Cited By :5

Transparent and translucent optical networks are widely considered as the prime candidates for the core network technology of the future. These networks provide ultra high speed end-to-end connectivity with high quality of service (QoS) and resilience to failures. This will be achieved through appropriate network planning techniques. A downside of transparency, however, is the accumulation of physical layer impairments over long distances, which are difficult to mitigate using purely physical-layer techniques. Considering the impact of physical layer impairments on network planning and operation has received considerable attention from research community. A novel physical layer impairment aware network planning tool is presented in this paper. Its performance is quantitatively compared with results obtained by a state-of-the-art tool under a common network scenario. The differences between the two planning approaches are illustrated and discussed.

A deployment of femtocells that is harmonic with its environment is a challenging issue. In this respect, interference management has traditionally been in the spotlight. However, architectural improvements for efficient femtocell deployments, despite being equally relevant, have received less attention. This paper presents a system architecture conceived for efficiently deploying femtocells in the form of Networks of Femtocells (NoFs). In this scenario, a group of femtocells in the same administrative domain cooperate towards a global performance improvement. Key to this improvement is the introduction of a new entity called Local Femto Gateway (LFGW) and the modifications in the femtocells in the local network. This allows offloading a high volume of control and data traffic from the core network of the mobile operator to the functional entities in the NoF. In particular, this paper focuses on building blocks related to traffic and mobility management. A two-level routing approach is discussed. The highest level is carried out by the mobile network layer. It is in charge of (1) determining the communication endpoints in the form of GPRS Tunneling Protocol (GTP) tunnel endpoint IDs, and (2) forwarding packets between tunnels belonging to the same Evolved Packet System (EPS) bearer at the appropriate nodes. Solutions for efficient handoff, local breakout, and local location management are presented for this level of routing. On the other hand, the lowest-level routing is carried out by the transport network layer. This level is in charge of finding the path between the above endpoints by efficiently using the local transport network that interconnects the femtocells in the NoF. A distributed routing solution for a large-scale, allwireless network of femtocells is also presented. Overall, these architectural improvements render NoFs a promising approach for efficient traffic management in large-scale femtocell deployments, hence making them a scalable solution. © Springer Science+Business Media, LLC 2012.

Cataloged from PDF version of article. A two-way relay channel is considered where two users exchange information via a common relay in two transmission phases using physical-layer network coding (PNC). We consider an optimal decoding strategy at the relay to decode the network coded sequence during the first transmission phase, which is approximately implemented using a list decoding (LD) algorithm. The algorithm jointly decodes the codewords transmitted by the two users and sorts the L most likely pair of sequences in the order of decreasing a-posteriori probabilities, based on which, estimates of the most likely network coded sequences and the decoding results are obtained. Using several examples, it is observed that a lower complexity alternative, that jointly decodes the two transmitted codewords, has a performance similar to the LD based decoding and offers a near-optimal performance in terms of the error rates corresponding to the XOR of the two decoded sequences. To analyze the error rate at the relay, an analytical approximation of the word-error rate using the joint decoding (JD) scheme is evaluated over an AWGN channel using an approach that remains valid for the general case of two users adopting different codebooks and using different power levels. We further extend our study to frequency selective channels where two decoding approaches at the relay are investigated, namely; a trellis based joint channel detector/physical-layer network coded sequence decoder (JCD/PNCD) which is shown to offer a near-optimal performance, and a reduced complexity channel detection based on a linear receiver with minimum mean squared error (MMSE) criterion which is particularly useful where the number of channel taps is large.

The existing dimensioning strategy for translucent, sub-wavelength switching architectures relies on over-provisioning, and consequently, overuse of costly, power-consuming optical-electrical-optical (O/E/O) regenerators. In addition, due to a variety of external phenomena, many physical layer impairments are time-varying, and hence, can strongly degrade network performance. In this work, we introduce a Cross-Layer Optical Network Element (CLONE) used for the dynamic management of physical layer impairments in the network. We investigate the impact of real-time impairment aware routing in a CLONE-enabled optical network with sub-wavelength switching. Simulation results show that the CLONE-enabled network architecture provides improvements in: (1) energy efficiency by optimizing the usage of regenerators, and (2) network performance in terms of the packet loss probability.

International audience; In this work, the Quantitative Structure-Property Relationship (QSPR) strategy is applied to represent/predict the surface tension of pure chemical compounds at (66.36-977.40). K temperature range. To propose a comprehensive, reliable, and predictive model, 18298 data belonging to experimental surface tension values of 1604 chemical compounds at different temperatures are studied. The Sequential Search mathematical method has been observed to be the only variable search method capable of selection of appropriate model parameters (molecular descriptors) regarding this large data set. To develop the final model, a three-layer Artificial Neural Network has been optimized using the Levenberg-Marquardt (LM) optimization strategy. Using this dedicated strategy, we obtain satisfactory results quantified by the following statistical parameters: absolute average deviations of the represented/predicted properties from existing experimental values: 3.8%, and squared correlation coefficient: 0.985.

A primary challenge in multicasting video in a wireless LAN to multiple clients is to deal with the client diversity - clients may have different channel characteristics and hence receive different numbers of transmissions from the AP. A promising approach to overcome this problem is to combine multi-resolution (layered) video coding with interlayer network coding. The fundamental challenge in such an approach is to determine the strategy of coding the packets across different layers that maximizes the number of decoded layers at all clients. This paper makes three contributions. (1) We first show that even for one client, the previously proposed canonical triangular scheme for inter-layer network coding can perform poorly. We show how to enhance the triangular scheme by incorporating the estimated target number of layers which significantly improves its effectiveness. (2) We show that such an enhanced triangular scheme still performs poorly for multiple clients with diverse channel characteristics, which motivates the need for searching for the optimal coding strategy. The naive way of searching for the optimal strategy is computationally prohibitive. We present several optimizations that drastically reduce the complexity of exhaustively searching for the optimal strategy, making it feasible in real time. (3) Finally, we design and evaluate an online video delivery scheme, Percy, to be deployed at a proxy behind the AP of a wireless LAN. Our simulation results show that Percy outperforms the previous inter-layer coding heuristic by up to 22-80% with varying numbers of clients. 2011 IEEE. Qatar National Research Fund Scopus

A primary challenge in multicasting video in a wireless LAN is to deal with the client diversity - clients may have different channel characteristics and hence receive different numbers of transmissions from the AP. A promising approach to overcome this problem is to combine scalable video coding techniques such as MRC or MDC, which divide a video stream into multiple substreams, with inter-layer network coding. The fundamental challenge in such an approach is to determine the strategy of coding the packets across different layers that maximizes the number of decoded layers at all clients. In [7], the authors showed that inter-layer NC indeed helps the delivery of MRC coded media over the WiFi, and proposed how to efficiently search for the optimal coding strategies online. In this paper, we study (1) how NC can help with WiFi delivery of MDC media, and (2) in particular, due to the different decoding requirements of MDC from MRC, whether WiFi delivery of MDC media can benefit more from NC compared to that of MRC media. Our simulation results are somewhat surprising. Even though MDC is generally shown to outperform MRC in lossy channels, most of the benefit of MDC over MRC is lost after applying NC to both schemes. 2011 ACM. Qatar National Research Fund Scopus

[EN] The paper addresses the problem of distribution of highdefinition video over fiber-wireless networks. The physical layer architecture with the low complexity envelope detection solution is investigated. We present both experimental studies and simulation of high quality high-definition compressed video transmission over 60 GHz fiberwireless link. Using advanced video coding we satisfy low complexity and low delay constraints, meanwhile preserving the superb video quality after significantly extended wireless distance. © 2011 Optical Society of America., This work has been partly funded by the European Commission under FP7 ICT-249142 FIVER project and by the by the Spanish Ministry of Science and Innovation under the TEC2009-14250 ULTRADEF project.

Internal vehicle communication networks are becoming highly distributed systems. The increase of the internal vehicle electronic system complexity requires higher performance and reliability, and the necessity of ensuring enough bus signal integrity increases the design verification effort. In this paper we present a system verification methodology of Flexray communication networks through behavioral simulations as well as the analysis of important parameters which influence the communication. The paper presents the verification of different network topologies through mixed-mode behavioral simulations and the evaluation of the most critical aspects of the physical layer. Modifications in the original topologies have been performed, and their effects have been analyzed. Additionally, we give special attention to the computational effort required for the behavioral simulations. The different topologies have been simulated with two bus line models (a lossless and a lossy), and the results are evaluated in terms of CPU usage time and accuracy.

Since an IP data traffic has rapidly been growing during the last few years, transport bandwidth requirements become a critical issue. The basic trend of the next-generation carrier networks is eliminating intermediate layers in the backbone and creating two-layer network architecture consisting of IP over optical layer, i.e. to eliminate a SONET/SDH and ATM layer. In this new architecture, the capacity issues are being addressed by using a DWDM technology. Dynamic provisioning, protection and restoration at the wavelength level are introduced using a wavelength router. IP + optical gives the final solution for the next-generation carrier networks as the combination of the intelligence of the IP routing with the economics and capacity of the optical technology.

Shared Access terrestrial-satellite backhaul Network enabled by Smart Antennas (SANSA) is a project funded by the EU under the H2020 program. The main aim of SANSA is to boost the performance of mobile wireless backhaul networks in terms of capacity, energy efficiency and resilience against link failure or congestion while easing the deployment in both rural and urban areas and assuring at the same time an efficient use of the spectrum. This paper provides an overview and the first results of the project, and, more specifically, it describes the regulatory environment, the State of The Art of mobile backhauling technologies regarding Ka band, the scenarios, the use cases and the key performance indicators along with the SANSA architecture, network (NET) and physical (PHY) layer techniques used to enhance wireless backhauling capabilities. Copyright (c) 2017 John Wiley & Sons, Ltd.