The orthogonal frequency-division multiplexing (OFDM) is a promising waveform for joint radar and communication systems. In this article, a unified approach is proposed to analyse both radar and communication robustness with respect to Doppler mismatch. The analytical study leads to an expression that links the radar performance to the communication one. The performance of a delay-Doppler radar is quantified by modelling the delay response of the OFDM radar with an appropriate random variable. Different delay filters are analysed, among which the Wiener filter. The analytical results are validated by simulations, they show that the radar system benefits from the Wiener filter, and the configurations where this filter outperforms the other ones are outlined.

Techniques that improve interfacing between power-line communication (PLC) systems and LED-based visible light communication (VLC) systems start to gain attention in recent years. Indeed, this hybrid system is able to provide simultaneously power, lighting, and data transmission. Contrariwise, if the integration between PLC and commercial LED bulbs is done unintentionally, the risks of PLC data leakage by commercial LED bulbs must be carefully analyzed. Thus, in this paper, the risks of eavesdropping on the PLC network via commercial LED bulbs are studied. The impact of the LED driver on PLC data leakage through LED bulbs is explained. The electrical-optical channel transfer function for different LED bulbs and the power spectral density of the signal received through the LED bulbs when two commercial powerline modems are plugged into the same power line are measured. Afterwards, pseudo random binary sequence signals are injected into the electrical-optical channel in order to assess quantitatively the possibility to extract information from the received signal. Finally, simple LED driver modifications that foster and increase the leakage are analyzed.

For finite blocklength polar codes, the minimum distance and the number of low weight codewords are essential to obtain good performance under successive cancellation list decoding with moderate and high list sizes. In this paper, we propose a code design method to decrease the number of low weight codewords for some information lengths with a very low computational complexity. In the proposed method, some information bits are encoded by several rows of the polar encoding matrix, i.e., each of the dynamic frozen bits is chosen the same as one of the preceding information bits. The dynamic frozen bit index set is determined by using the connection between the binary representation of the row indices and the number of common 1-bit positions of any given rows. The resulting design is shown to perform as well as polarization-adjusted-convolutional codes [9] under successive cancellation list decoding but with significant computational complexity savings. These findings pave the way for the use of polar codes in applications with stringent complexity and with low energy consumption constraints.

Reed Muller (RM) codes are known for their good minimum distance. One can use their structure to construct polar-like codes with good distance properties by choosing the information set as the rows of the polarization matrix with the highest Hamming weight, instead of the most reliable synthetic channels. However, the information length options of RM codes are quite limited due to their specific structure. In this work, we present sufficient conditions to increase the information length by at least one bit for some underlying RM codes and in order to obtain pre-transformed polar-like codes with the same minimum distance than lower rate codes. Moreover, our findings are combined with the method presented in [1] to further reduce the number of minimum weight codewords. Numerical results show that the designed codes perform close to the meta-converse bound at short blocklengths and better than the polarized adjusted convolutional polar codes with the same parameters.

In this work, we give a complete characterization of the $\epsilon$-stable region in dynamic downlink random cellular networks. The $\epsilon$-stable region is the set of arrival rates such that the proportion of unstable queues in the network is not larger than $\epsilon$. We derive upper and lower bounds as well as an approximation of the critical arrival rate, which delimits the $\epsilon-$stable region. The developed model is based on stochastic geometry and queuing theory to handle the interaction between the transmit success probability and the queuing state evolution. Extensive numerical simulations are provided to confirm the tightness of the approximation.

The integration of powerline communication (PLC) with visible light communication (VLC) has attracted the attention of many researchers. Cascading these two techniques offers the possibility of performing a wired transmission over existing powerline infrastructure and a last-mile energy-efficient wireless transmission through pre-installed LEDs for indoor illumination. Therefore, VLC should be deeply analyzed to optimize its integration with other systems. So far, most research has only modeled the channel and modulation bandwidth of the VLC system. However, the electrical and optical aspects are rarely taken into account and there is no explicit expression of the received signal as a function of that emitted. So in this paper, An explicit expression is proposed allowing a direct calculation of the photo-current as a function of the transmitted current taking into account the optical, electrical, and frequency behavior of the VLC system. This expression is validated using measurement results.

In this work, we proposed a tractable mathematical framework to analyze the coverage probability in dynamic downlink cellular networks taking into account the queue dynamics with finite buffer restriction. In particular, the developed model is based on stochastic geometry and queueing theory to handle the interaction between the coverage probability and the queueing state evolution. We analyze the coverage probability as well as packet loss probability by discrete time Markov chain (DTMC) at stationary regime. We explicitly derive the influence of the packet buffer length to the coverage and packet loss probability. We show in particular that small buffer length leads to a better coverage probability but also to a larger packet loss probability, advocating for a tradeoff between these two metrics.

Inspired by the subject of performance enhancement of users located at the edge of cells in cellular networks, this paper studies a centralized frequency reuse scheme depending on the link quality of users within the Voronoi cell of the serving base station (BS) for the homogeneous Poisson point process (PPP) network. To quantify how much a user experiencing performance degradation, we consider that each cell is partitioned into multiple regions based on the strength of the signal to interference ratio. In our model, a given resource block (RB) is allocated to one user in a cell and cannot be shared by another user in this cell. The RB is divided into multiple subchannels and the user of interest uses only one of the multiple sub-channels, the mapping depending on the region in which the user belongs, letting a part of the RB unused to reduce the interference to the other cells. This scenario implies that the interfering set of BS depends on the coverage probability of the typical user. We tightly approximate the interfering BS set as a thinned version of the original PPP depending on the probability of coverage of each type of user. Results show that the scheme increases the network's global coverage probability and enhances spectral efficiency by comparing the known fractional frequency reuse scheme.

In this paper, we propose a new spectrum sensing (SS) algorithm called unified sensing algorithm (USA). This method exploits the results of different algorithms developed in the literature. The considered methods are especially those based on the covariance matrix of the received signal and those which further compute the eigenvalue decomposition of such matrix. More precisely, the USA algorithm implements some covariance matrix based methods, and in the case where the primary user is miss-detected, the eigenvalue decomposition is performed. This approach fully exploits all detection methods and avoids computational costs, as eigenvalue decomposition, when it is not necessary. Finally, the performance of the proposed method is provided and compared with existing state of the art algorithms. Simulation results show the performance improvement obtained with this new approach, namely the contribution in term of detection under very low signal-to-noise ratio (SNR).

This paper aims at characterizing the energy efficiency (EE)-area spectral efficiency (ASE) tradeoff in random geometry networks with multiple-antenna arrays at base stations (BSs). In particular, ASE and EE are studied with respect to the transmit power when BSs use a signal-to-leakage-plus-noise ratio (SLNR) precoder. When the static power consumption cannot be neglected, EE behaves linearly with respect to ASE before a sharp decreasing of EE due to the interference-limited characteristic of the network. Our contribution relies on the derivation of a closed-form expression for ASE with SLNR precoder in the asymptotic regime, i.e., when the number of antennas and users grows to infinity, using stochastic geometry. We derive EE from a linear power consumption model afterwards. Unlike conventional SLNR precoders, the average signal-to-interference-plus-noise ratio and the leakage to other cells are considered in a geometry-dependent network. Extensive Monte Carlo simulations show that despite the asymptotic nature of the theoretical analysis, the closed-form expressions are tight with respect to simulations even for the moderate number of antennas and users. Hence, the analysis can be used for realistic network performance analysis.

This paper deals with the energy-efficiency spectralefficiency (EE-SE) tradeoff in regular hexagonal interference-limited networks. We aim to characterize the EE-SE region when non negligible static circuitry power consumption is assumed and when several frequency reuse factors as well as shadowing are taken into account. Our contribution is three-fold: a parametric expression of the interference to signal ratio, a.k.a. fparameter, obtained with a curve fitting approach is proposed, the EE-SE tradeoff is then studied when several frequency reuse factors are considered and a new characterization, called the c-EE-SE tradeoff, is proposed when shadowing is considered. This definition relies on the outage capacity achievable and its corresponding EE and remains particularly useful when longterm fading is present.

This paper presents an opportunity to cancel range ambiguities in synthetic aperture radar (SAR) configuration. One of the limitations of SAR systems is the range ambiguity phenomenon that appears with long delayed echoes. The reflected signal corresponding to one pulse is detected when the radar has already transmitted the next pulse. Thus, this signal is considered as an echo from the next pulse. This paper investigates the opportunity of coding the transmitted pulses using an orthogonal frequency-division multiplexing pulse. The results show that coded-OFDM signals outperform conventional chirp signal and make it possible to relax constraints placed upon the pulse repetition frequency.

Remote sensing applications need specific signal processing to obtain high resolution for radar images. One of limitations for synthetic aperture radar (SAR) systems is the range ambiguity phenomenon that appears with long delayed echoes. The reflected signal corresponding to the pulse (n) is detected when the radar has already transmitted the next pulse (n + 1). Thus, this signal is considered as an echo from the pulse (n + 1). This paper investigates the opportunity of coding the transmitted pulse using an orthogonal frequency division multiplexing (OFDM) pulse. The results show that coded OFDM signal outperform conventional chirp signal.

The growth in energy demand coupled with global warming provide new trends in communication systems known as green radio. The main focus in green radio is to provide new techniques to save energy consumption. In this paper, a new concept, named ultra wide time (UWT), is proposed to define the lower asymptotic consumed energy to transmit a given amount of information. With UWT concept, minimization of energy consumption leads to infinite time of transmission. To overcome this drawback, and instead of energy minimization, we proposed to evaluate the energetic performance of communication systems with a new energy efficiency β, defined as the ratio between the asymptotic limit and the consumed energy. It is then possible to control the energetic consumption with finite time of transmission. The energy efficiency β is fixed in advance and the transmitter is then configured under this constraint. Both UWT and energy efficiency β are applied in parallel channel with best effort communications. Simulation results show that energetic gains of 20 dB can be reached in WiMAX configuration. This respects the ”two order of magnitude lower transmission power” mentioned by the Wireless World Research Forum.

The conventional resource allocation method in multicast OFDM systems adapts the physical layer to the worst user link conditions. In this paper, we propose new subcarrier, bit and time slot allocation algorithms for multicast OFDM systems in indoor powerline communication (PLC) context. To increase the multicast bit rate, these algorithms jointly use linear precoded OFDM (LP-OFDM) modulation technique and the conventional multicast approach to exploit the channel frequency selectivity experienced by each user. The LP technique applied to OFDM systems has already proved its ability to significantly increase the system throughput in a PLC context. Here, different groups of multicast users according to their channel conditions are created and different ways of gathering users, leading to different modes, are analyzed. Simulations are run over indoor PLC channels and it is shown that the proposed modes combined with the LP-OFDM solution offer a significant bit rate gain compared to the conventional multicast approach. In addition, the interest of gathering multicast users into groups for multicast OFDM systems in PLC context is shown.

Within the ICT OMEGA project, a thorough study of the Electro Magnetic Compatibility (EMC) issues linked to Power Line Communications (PLC) has been conducted. In this paper, we present our investigations carried out in the context of a frequency bandwidth extension of PLC systems up to 100 MHz. The current status of EMC regulations for PLC is first recalled. An experimental study is then presented for the assessment of the effect of electromagnetic field radiation from an electrical network, in the 30 - 100 MHz band. Recommendations are given for the injected PSD levels to be used for future studies within the OMEGA project. From these results, the capacity of the PLC channel is evaluated in terms of outage probability. This analysis shows that an extended bandwidth up to 100 MHz provides capacities in excess of 1 Gbps, while satisfying the current emission limits. Finally, the possible countermeasures for the mitigation of EMC issues are discussed.

The problem of bit rate maximization of a linear precoded orthogonal frequency division multiplexing (LP-OFDM) system is considered for imperfect channel state information. The discrete bit loading algorithms are proposed, which sustain the target bit error rate even under high mean square error (MSE) of estimation. The proposed scheme enhances the robustness of the system against noisy channel estimation without significantly compromising on the system throughput. The results are shown for a power line communication system using a well-known multipath channel model. It is shown that the proposed LP-OFDM allocation is more robust to estimation noise than OFDM allocations and provides higher throughputs even at high MSEs.

Ultra-wideband (UWB) has emerged as an exciting technology for short range, high data rate wireless personal area networks (WPAN) applications. The multiband orthogonal frequency division multiplexing (MB-OFDM) scheme is one of the main candidates for WPAN standardization. In this paper, we propose a new UWB waveform based on a spread spectrum multicarrier multiple-access (SS-MC-MA) scheme that respects the OFDM parameters of the MB-OFDM solution. Then, we suggest an efficient low-complexity resource allocation algorithm that maximizes the total system throughput. Furthermore, we dynamically distribute the time-frequency codes that provide frequency hopping between users, in order to improve our system performance. We show that our proposed system transmits data at much higher attenuation levels and higher throughputs compared to the MB-OFDM system. Consequently, we conclude that our proposed system can be advantageously exploited for high data rate UWB applications.

In this paper, we investigate the robustness of the spread spectrum multi-carrier multiple access (SS-MC-MA) technique in uplink multicellular systems. In a first step, a statistical characterization of the intercell interference is carried on to model it for BER performance simulations. Then, the impact of the intercell interference on such a scheme is evaluated and the robustness of SS-MC- MA system by mitigating those interferences thanks to frequency allocation, channel coding and spreading gain is optimized.

In this paper, we propose to apply adaptive loading principles to linear precoded digital multitone (LP-DMT). This new approach can especially be exploited in the powerline context, since it requires the knowledge of the channel at the transmitter. We first show that maximal waveform capacity is achieved when orthogonal matrices are used to linearly precode the multitone signal. A practical loading algorithm based on tone clustering is then developed to handle the configuration of the system. This algorithm assigns tones, size of preceding matrices, bits and energies in order to maximize the total throughput of the system. The optimization procedure is led under power spectral density (PSD) limitations and finite order modulations constraint. Through simulations over power line channels, it is shown that the new adaptive LP-DMT system takes advantage of the carrier merging effect offered by the precoding function and then outperforms the non-precoded DMT system.

In this paper, we investigate the dynamic resource allocation adapted to spread-spectrum multicarrier multiple-access (SS-MC-MA) systems in a multiuser power line communication (PLC) context. The developed adaptive system is valid for uplink, downlink, as well as for indoor and outdoor communications. The studied SS-MC-MA system is based on classical multicarrier modulation like digital multitone (DMT), combined with a spread-spectrum (SS) component used to multiplex several information symbols of a given user over the same subcarriers. The multiple-access task is carried out using a frequency-division multiple-access (FDMA) approach so that each user is assigned one or more subcarrier sets. The number of subcarriers in each set is given by the spreading code length as in classical SS-MC-MA systems usually studied in the wireless context. We derive herein a new loading algorithm that dynamically handles the system configuration in order to maximize the data throughput. The algorithm consists in an adaptive subcarrier, code, bit, and energy assignment algorithm. Power-spectral density constraint due to spectral mask specifications is considered, as well as finite-order modulations. In that case, it is shown that SS-MC-MA combined with the proposed loading algorithm achieves higher throughput than DMT in a multiuser PLC context. Because of the finite granularity of the modulations, some residual energy is indeed wasted on each subcarrier of the DMT spectrum. The combining of a spreading component with DMT allows to merge these amounts of energy so that one or more additional bits can be transmitted in each subcarrier subset leading to significant throughput gain. Simulations have been run over measured PLC channel responses and highlight that the proposed system is all the more interesting than the signal-to-noise ratio is low.

This paper investigates optimum and sub-optimum linear minimum mean square error (MMSE) multi-user detection (MUD) techniques for multi-carrier code division multiple access transmission systems. In a first step, we present two formulations of MMSE MUD techniques that are optimum for any number of users and any power distribution and achieve exactly the same performance with a different computational complexity. In a second step, we present a simplification of optimum MMSE MUD techniques that achieves sub-optimum performance but at a reduced complexity that is similar to single-user detection techniques. Simulation results on indoor channels show that optimum and sub-optimum MMSE MUD techniques outperform the MMSE single-user detection technique, especially for low and medium system loads as well as in the case of the near-far effect.