Philippe Mary

BPSK Bit Error Outage over Nakagami-m Fading Channels in Lognormal Shadowing Environments

In this letter, we address the problem of finding a tractable expression for the bit-error outage (BEO) defined as the probability to observe a given average bit error rate (BER) over a fading channel in a shadowing environment. Our contribution is two-fold: (1) a simple yet tight approximation of the bit error probability (BEP) for binary phase shift keying (BPSK) over a frequency-flat Nakagami-m fading channel is derived, which (2) facilitates the derivation of a tight lower bound of the BEO in presence of lognormal shadowing in closed form. Theoretical results are corroborated by means of simulation results, confirming the tightness of the bounds.

M-ary symbol error outage over Nakagami-m fading channels in shadowing environments

This letter addresses the problem of finding a tractable expression for the symbol error outage (SEO) in flat Nakagami-m fading and shadowing channels. We deal with M-ary phase shift keying (M-PSK) and quadrature amplitude modulation (M-QAM) which extends our previous results on BPSK signaling. We propose a new tight approximation of the symbol error probability (SEP) holding for M-PSK and M-QAM signals which is accurate over all signal to noise ratios (SNRs) of interest. We derive a new generic expression for the inverse SEP which facilitates the derivation of a tight approximation of the SEO in a lognormal shadowing environment.

Performance Analysis of Time-Reversal Based Precoding Schemes in MISO-OFDM Systems

Time-Reversal (TR) precoding schemes are regarded as promising candidates for robust and energy efficient wireless systems. These schemes are characterized by their low computational complexity at the receiver side. In multipath Rayleigh fading channel, this paper presents analytical expressions of the average bit error rate (BER) of TR technique and the Equal Gain Transmission (EGT) scheme in MISO-OFDM systems. It further provides simple and tight upper bounds on the ergodic capacity of these schemes. Hence, these theoretical analyses might be very useful to avoid lengthy simulations. It also provides an interesting conclusion: for large number of transmit antennas, i.e. in Massive MIMO, TR technique outperforms the EGT scheme and its performance approaches that of Maximum Ratio Transmission (MRT) scheme. Hence, it confirms the applicability of TR scheme in the future Massive MIMO systems. Results with LTE-A system parameters are provided in order to corroborate our analysis.

Symbol Error Outage Analysis of MIMO OSTBC Systems over Rice Fading Channels in Shadowing Environments

We deal with the analytical performance study of orthogonal space-time block codes (OSTBC) applied to multiple-input multiple-output (MIMO) systems experiencing non-frequency selective fast fading and shadowing. We address the problem of finding a tractable closed-form expression for the symbol error outage (SEO) over Rice fading channels in shadowing environments. In order to obtain the SEO, a symbol error probability (SEP) inversion w.r.t. the average signal to noise ratio (ASNR) is needed since no invertible SEP approximations are available in literature. We propose an accurate approximation for the SEP in Rice fading channels. This new approximation is proved to be invertible w.r.t. the ASNR and this expression thus facilitates the derivation of a tight approximation of the SEO in lognormal shadowing environments.

Global Ergodic Capacity Closed-Form Expression of Coexisting DVB-LTE-Like Systems

In this paper, we analyze the problem of deploying small cellular cells into a large broadcast cell in the framework of the convergence between the Long Term Evolution (LTE) and the Digital Broadcasting Video (DVB) technologies. In this work, a non- cooperative deployment of these technologies is considered in the sense that cellular and broadcast networks interfere on each other. In literature, there is no work dealing with the ergodic capacity of full cross-interfering links in a DVB-LTE convergence scenario. Our contribution lies in two folds: i) the global ergodic capacity is derived in closed-form with Rayleigh fading channel on each link. This derivation allows us to evaluate the global data rate of the DVB and LTE in a spectral overlap scenario. ii) The analytical forms allow the evaluation of the influence of system parameters on the global and broadcast data rate, e. g. mobile and broadcast power, distance between the broadcast receiver and the LTE base station.

Energy Efficiency-Spectral Efficiency Tradeoff in Interference-Limited Wireless Networks with Shadowing

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.

Ergodic capacity optimization in coexisting DVB-LTE-like systems

In this paper, the ergodic capacity maximization problem in case of coexistence between digital video broadcasting (DVB) and long term evolution (LTE) systems is studied. A full interference scenario, i.e. where the DVB and LTE systems spectrally overlap, is assumed. The objective function, defined as the summation of the LTE and DVB system capacities, is shown to be constituted by a convex and concave parts and only depends on the ratio of transmitted powers. Hence, we first apply the convex concave procedure (CCCP) to the maximization problem, under QoS constraints, in order to obtain the optimal functioning point. The optimal solution is shown to be the minimum of the global capacity but leads to a strict fairness situation between the LTE and DVB systems. We hence propose a second simple algorithm strictly maximizing the global capacity under QoS constraints. The algorithm leads to a global data rate higher than the one obtained with CCCP but favor largely one system over the other. This study can be useful for operators interested in dense network deployment scenarios to decide the operating point of resources allocated in a very aggressive frequency reuse pattern.

Packet Error Outage for Coded Systems Experiencing Fast Fading and Shadowing

In this paper, we consider the performance of coded wireless communication systems experiencing non-frequency selective fading channels in shadowed environments. The quality of service (QoS) in a wireless network is dependent on the packet error outage (PEO). We address the problem of finding a tractable expression for the coded PEO over Nakagami-m channels with shadowing, considering multilevel modulations, various block and convolutional channel coding schemes and hard decision decoding. In order to obtain the coded PEO, an inversion of the coded packet error probability (PEP) w.r.t. the signal to noise ratio (SNR) is needed. To this end, we propose an invertible approximation for the coded PEP w.r.t. the uncoded bit error probability (BEP) in Nakagami-m fading channels which is accurate for all BEPs of interest. The BEP itself depends on the average SNR and we hence make use of previous results on the inversion of the uncoded BEP w.r.t. the SNR in Nakagami-m fading channels, holding for M-PSK and M-QAM signals. We were thus able to obtain a reliable closed form expression for the coded PEO in flat fading and shadowing channels. The theoretical findings are verified by means of simulations.

Energy efficiency analysis in relay assisted hybrid-ARQ communications

This paper studies the energy efficiency (bits/joule) in relay assisted networks using Chase combining hybrid-ARQ (HARQ-CC) retransmission technique. As energy efficiency depends on the average delay and the packet error probability (PER), we start by deriving an approximation of the PER for HARQ-CC retransmission scheme. This approximation is really simple compared to the existing expressions in the literature and is proved to be tight enough to address the energy efficiency study. In particular, the energy efficiency is investigated in terms of destination position and in terms of transmission power of the source and the relay. The results give some insights on the optimal transmission power according to the maximum number of retransmissions maximizing the energy efficiency.

Performance Analysis of Mitigated Asynchronous Spectrally-Overlapping WLAN Interference

The deployment of wireless local area networks (WLANs) has recently gained in popularity with roll-out densities often reaching saturation levels. The frequency bands designated to WLANs do thus not suffice anymore to provide non-overlapping, and hence interference-free, communication. Prior research has therefore been dedicated to a wide variety of mainly cochannel interference mitigation techniques. Our contribution lies in the performance analysis of the more realistic case of spatially close WLAN systems interfering asynchronously in DSSS mode and on adjacent channels. The authors expose the performance of optimum and sub-optimum multiuser detection maximum likelihood sequence estimators (MUD-MLSEs) under varying conditions, e.g. level of interference, degree of spectral overlap, etc. This facilitates a better understanding and design of future interference-limited WLAN systems. The performance results are also important to spectrum policy makers, allowing to knowledgeably estimate the degree of tolerated interference in license exempt bands.