Espace membre

Cet espace est dédié aux étudiants, aux enseignants et au personnel administratif de l'école

Valider

Mot de passe oublié?

Evènements et manifestations

08/04/2017

Doctorate thesis defense of Marwane BEN HCINE




Doctorate thesis defense on April 08th 2017 at 09H00 AM ,in Amphi II, Sup’Com.


Entitled :Exponential Effective SINR Computation for LTE Networks

Presented by : Marwane BEN HCINE 





Committee


President

Mme. Houria REZIG

Professor, ENIT, Tunis.

 

 

 

Examiner

Mr. Neji YOUSSEF

Professor, Sup’Com, Tunis.

   

Reviewers

Mr. Tahar EZZEDINE,

Associate professor, ENIT, Tunis.

 

Mr. Mohamed Lassaad AMMARI,

Associate professor, ENISO, Sousse.

 

Supervisor

Mr. Ridha BOUALLEGUE,

Professor, Sup’Com, Tunis.

 

Abstract


The exponential effective SINR is a fundamental tool for evaluating and studying next generation orthogonal frequency division multiplexing (OFDM) based wireless systems such as LTE. It converts the different gains of multiple subchannels, over which a codeword is transmitted, into a single effective flat-fading gain with the same codeword error rate. It enables fast link adaptation by allowing each user to compute a precise channel quality indicator (CQI), which is fed back to the eNodeB for downlink rate adaptation and scheduling. For a given practical case, exponential effective SINR prediction relies on the approximation of the sum distribution of correlated lognormal random variables. The present thesis focuses on two major issues. First, the establishment of a novel approximation method for the sum of dependent lognormal random variables. Second, the study and the investigation of closed-form expression 2 for the exponential effective SINR spatial distribution in LTE downlink and uplink. Concerning the first issue, several methods have been proposed in the literature to be able to approximate the sum of dependent lognormal random variables. The accuracy of proposed methods relies highly on the individual lognormal parameters (mean and variance), and the examined region of the resulting distribution. Providing an acceptable accuracy for all cases, remains a challenge till today. In this thesis, a novel approximation technique for the sum distribution of correlated lognormal random variables based on log skew normal distribution is developed. A simple analytical method for log skew normal parameters derivation is proposed, which make possible the establishment of a highly accurate approximation to the sum of dependent lognormal random variables for any correlation coefficient over the whole range of dB spreads. Simulation results prove that our method performs better than all previously proposed methods and offers an accuracy within 0.01 dB for all cases. Concerning the second issue, we provide an original analytical framework for efficient computation of the exponential effective SINR in LTE networks. Beyond 3G cellular mobile communication standards, including LTE and WiMAX are based on multicarrier modulation. Thus, the classical single carrier SINR performance evaluation is no longer possible. The solution is to extend SINR assessment into multi-carrier systems operating over frequency selective channels. The extension is established by expressing the link outage probability by means of the effective SINR statistics. Considering LTE downlink, we rely on the log skew normal approximation to express link outage probability for the for single carrier case. By using the mean and standard deviation of the SINR of a generic subcarrier, the closed-form expression for the exponential effective SINR distribution is obtained assuming a log normal approximation. Achieved formulas are quickly computable and can be established for any user equipment located in the network. For LTE uplink, we rely on the lognormal approximation in order to provide an analytical evaluation for inter-cell interference. Distribution parameters are derived analytically. For single carrier SINR distribution, closed-form expression of the link outage probability is obtained assuming a log skew normal approximation. Similar to downlink case, closed-form expression for the exponential effective SINR distribution is obtained assuming a log normal approximation. According to simulations results, our approach provides an accuracy within 0.5 dB while evaluating the effective SINR distribution in both LTE downlink and uplink. Achieved formulas are used to calibrate the power control compensation factor for LTE uplink.


Keywords


LTE; OFDMA; SC-FDMA; Effective SINR; Log Skew Normal; Log Normal.