Performance Analysis of Uplink NOMA-Relevant Strategy Under Statistical Delay QoS Constraints

A new multiple access (MA) strategy, referred to as non orthogonal multiple access - Relevant (NOMA-R), allows selecting NOMA when this increases all individual rates, i.e., it is beneficial for both strong(er) and weak(er) individual users. This letter provides a performance analysis of the NOMA-R strategy in uplink networks with statistical delay constraints. Closed-form expressions of the effective capacity (EC) are provided in two-users networks, showing that the strong user always achieves a higher EC with NOMA-R. Regarding the network's sum EC, there are distinctive gains with NOMA-R, particularly under stringent delay constraints

User Grouping and Power Allocation in NOMA Systems : A Reinforcement Learning-Based Solution

Author's accepted manuscript.Available from 05/09/2021.acceptedVersio

A dynamic channel access strategy for underlay cognitive radio networks: Markov modelling and performance evaluation

[EN] Unlike in overlay cognitive radio networks, secondary users in underlay cognitive radio networks can access licensed spectrum even at the presence of a primary user, given that the interference caused by the secondary transmission is lower than a pre-specified threshold. Based on this underlay access principle, we propose in this paper a dynamic channel access strategy for multi-channel cognitive radio networks. Different from existing underlay access techniques, channel assembling, spectrum adaptation and restricted channel occupancy are also considered in the proposed strategy in order to achieve better performance in the secondary network. Accordingly, a partial channel occupancy mode, which allows secondary users to access a portion of a channel when co-existing with a primary user, is introduced in this study. The size of this portion is adjusted by selecting an appropriate value of a configurable parameter ¿ in the partial channel occupancy mode. The system performance is evaluated for both primary and secondary networks, and a comparison analysis is carried out to assess the cost against the gain. Numerical results demonstrate that the proposed underlay channel access strategy outperforms the corresponding overlay strategy in terms of secondary network capacity, blocking probability and dropping probability. The cost and gain analysis identifies appropriate traffic conditions under which the overall system performance could be improved by employing the proposed underlay strategy.The work of V. Pla was supported in part by the Ministry of Economy and Competitiveness of Spain under Grant TIN2013-47272-C2-1-R.Jalali, E.; Balapuwaduge, IAM.; Li, FY.; Pla, V. (2017). A dynamic channel access strategy for underlay cognitive radio networks: Markov modelling and performance evaluation. Transactions on Emerging Telecommunications Technologies. 28(1):1-11. https://doi.org/10.1002/ett.2928S11128

Allocation de ressources distribuée dans les réseaux OFDMA multi-cellulaires

La thèse étudie des méthodes d'allocation de ressources, distribuées par station de base (BS) dans les réseaux OFDMA multi-cellulaires. L'objectif est de fournir la Qualité de Service (QdS) requise par chaque utilisateur, quelle que soit sa localisation dans la cellule. Les travaux portent d'abord sur la coordination causale de réseaux. Deux BSs forment un lien MIMO virtuel pour les utilisateurs localisés en bordure de cellule. Ces utilisateurs bénéficient d'un gain de diversité et d'une diminution de l'interférence inter-cellulaire. L'efficacité de la méthode d'allocation de ressources associée dépend de l'équité du contrôle de puissance. En conséquence, la coordination de réseaux est utilisée pour les utilisateurs à Débit Contraint (DC), mais pas pour les utilisateurs Best Effort (BE), dans un algorithme permettant de gérer conjointement les deux objectifs de QdS. La thèse étudie ensuite les réseaux totalement distribués. Pour les utilisateurs DC, une méthode d'allocation de ressources incluant une allocation de puissance itérative est déterminée pour résoudre le problème Margin Adaptive. Cette méthode est étendue aux utilisateurs DC en MIMO, lorsque le transmetteur connaît tout l'information de canal, ou uniquement ses caractéristiques statistiques. Pour les utilisateurs BE, enfin, l'objectif est de maximiser la somme des débits pondérés, le poids de chaque utilisateur étant proportionnel à la longueur de sa file d'attente. Une méthode d'allocation de sous-porteuses, déduite d'un graphe d'interférence, et une méthode de contrôle de puissance distribuée sont proposées pour résoudre ce problème d'optimisation

Comparison of distributed space and frequency interference alignment

This paper addresses multiple access in MIMOwireless networks. It compares two distributed interferencealignment techniques, in space and in frequency, that bothaim at removing interferences through orthogonalization. Thetheoretical advantages and drawbacks of each technique arehighlighted. Then, the multiplexing gain and the computationalcomplexity are analytically evaluated. It is shown that frequencyinterference alignment achieves a higher multiplexing gain thanspace interference alignment in realistic network conditions,and always requires a lower computational complexity. Finally,the performances of both algorithms with varying number ofinterfering links are assessed via numerical simulations. Spaceinterference alignment fulfills complete interference suppression,and consequently provides the same spectral efficiency to alllinks, regardless of the number of interfering links. Frequencyinterference alignment is less efficient in terms of INR, and thespectral efficiency per link thus decreases when the number oflinks increases. Nevertheless, the spectral efficiency is alwayshigher with frequency interference alignment than with spaceinterference alignment