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Atténuation des interférences dans les réseaux mobiles 5G : Contamination pilote des liaisons montantes dans le schéma massif MIMO TDD

Abstract : By the revolution of Cloud Computing and Smartphones, an enormous amount of data should traverse the network every second where most of this data are delivered by mobiles using internet services. The fast growth in bandwidth and QoS demands makes the 4th G mobile networks insufficient. The next generation system must afford a sum rate from 100Mbps up to 1Gbps per User Terminal (UT), with a connection density that exceeds 1M connection/Km2, the mobility of high-speed vehicles up to 500 km/hr and an End to End (E2E) delay less than 10ms. A promising candidate that can offer those demands is the Multi-User Multi-Cell Massive Multiple-Input Multiple-Output (MIMO) wireless system. However, Massive MIMO capacity is upper bounded by the Inter-cell Interference (ICI) due to pilot reuse and thus, pilot contamination. In this thesis, we investigate the uplink pilot contamination in Time Division Duplexing (TDD) training scheme of massive MIMO wireless networks. Assuming block-fading channel, the coherence interval will lag for a limited duration, where channel estimation, symbol reception, and symbol precoding must be done within the same interval. Having said that, the training pilot length is limited. Likewise, the number of User Terminal’s (UT’s) per interference region is also limited. Inspired by the variation of coherence interval size among UT’s, this research introduces two independent novel contributions to deal with uplink pilot contamination in massive MIMO. The first contribution maps the Base Station (BS) cell coverage region into a Channel State Information (CSI) Map. This map is created and updated using a special machine-learning algorithm, and it is exploited to predict UT CSI instead of estimating their channels. In view of this, training overhead and uplink pilots are reduced significantly. The second contribution classifies UT’s based on the size of their channel coherence interval. Furthermore, we apply a pilot shifting technique to shift similar pilots to different time position (that considered empty due to empty pilot TDD frames). Simulation results show a scaled increase in the performance of massive MIMO especially in the performance of energy and spectral efficiency, UT per cell and sum-rate. In particular, the third contribution evolves multi-cell massive MIMO to a single cell performance and even overcome single conventional huge in the energy efficiency and UT per cell.
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https://tel.archives-ouvertes.fr/tel-01619147
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Submitted on : Thursday, October 19, 2017 - 10:15:11 AM
Last modification on : Friday, March 26, 2021 - 12:46:09 PM
Long-term archiving on: : Saturday, January 20, 2018 - 2:06:24 PM

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Ahmad Abboud. Atténuation des interférences dans les réseaux mobiles 5G : Contamination pilote des liaisons montantes dans le schéma massif MIMO TDD. Electronics. Université de Limoges, 2017. English. ⟨NNT : 2017LIMO0040⟩. ⟨tel-01619147⟩

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