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Stratégies d'allocation de ressources dans des contextes mono et multiutilisateurs pour des communications à très haut débit sur lignes d'énergie

Abstract : The demand for broadband services over PLC (powerline communications) networks has been growing rapidly during the recent past due to the availability of infrastructures and low deployment costs. This kind of network supports multiple high-speed traffics with seamless connectivity among multiple nodes and access points. In this context, efficient management of available resources through allocation policies is needed to satisfy the quality of service requirements. These policies consist in determining efficient rules for allocating resources in order to optimize the transmission rates in PLC network. This thesis proposes resource allocation strategies to increase transmission rates in single and multi-user contexts. However, the transmission characteristics of the powerline channel are less favorable for data transfer, since it was originally not designed for that purpose. To exploit these difficult channel conditions, data is transmitted via a waveform combining the linear precoding technique and the multicarrier OFDM modulation scheme, leading to the LP-OFDM (linear precoding OFDM) solution. Assuming a perfect knowledge of the channel conditions at the transmitter side, this combination allows a more efficient utilization of the available transmission power. The achieved data rates are then increased by adapting modulation orders, transmitted power levels and the distribution of time-frequency resources, to the channel conditions. The main objective of this thesis is to study and optimize distribution strategies, for one or more users, of different subchannels (subcarriers in OFDM case and precoding sequences in LP-OFDM case) of the multicarrier systems and the bits and powers allocated to these subchannels. First, the problem of maximizing the bit rate is studied in a single user context and uses as the basis for multi-user context. A new resource allocation algorithm for LP-OFDM systems with minimum mean square error equalizer is proposed and constitutes the first original contribution. In addition, two novel bit and power allocation algorithms, with low complexity, are proposed to maximize the total bit rate while satisfying a bit error rate constraint. Then, a physical layer approach of multicast communications is addressed for LP-OFDM systems. The proposed methods better exploit the diversities of transmission links to increase the users' bit rates. Compared to the conventional resource allocation method in multicast OFDM systems, simulation results show bit rate gains up to 70% with linear precoding based methods. Finally, the possibility for several users to simultaneously access to the same physical medium is analysed for PLC networks. Current powerline communication systems are characterized by multiple access methods where different users transmit their signals in separate time intervals. New resource allocation algorithms are then proposed and analysed for simultaneous transmission over the same physical medium, in centralized and decentralized manner. Again, the results show the interest of the LP-OFDM solution.
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Submitted on : Thursday, June 30, 2011 - 4:56:11 PM
Last modification on : Wednesday, April 27, 2022 - 3:55:58 AM
Long-term archiving on: : Saturday, October 1, 2011 - 2:26:44 AM


  • HAL Id : tel-00605144, version 1


Ali Maiga. Stratégies d'allocation de ressources dans des contextes mono et multiutilisateurs pour des communications à très haut débit sur lignes d'énergie. Traitement du signal et de l'image [eess.SP]. INSA de Rennes, 2010. Français. ⟨tel-00605144⟩



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