PhD graduated
Team : Phare
Departure date : 06/26/2014

Supervision : Guy PUJOLLE

Co-supervision : GHAITH Alaa

Cross-layer Spectral and Energy Efficient Scheduling Algorithms with Adaptive Modulation and Coding in LTE Heterogenous Networks

Responding to the huge demand for high data rates and satisfying Quality of Service (QoS) requirements are the main objectives of the wireless mobile operators. LTE-based small cell system is a promising technology offering the required services, enhanced indoor coverage and increased system capacity. However, many challenges face the constructors and the operators for an effective deployment of these systems. In this thesis, in order to evolve such systems and adduce significant enhancement in terms of QoS and throughput, we adopt a complementary strategy based on both data link layer and physical layer. First, we propose, on the link layer level, two scheduling and joint resource allocation algorithm based on the Adaptive Modulation and Coding (AMC) and the power control mechanism for OFDMA-Downlink and SC-FDMA-Uplink connections respectively. Namely, they refer to: “Downlink AMC-QRAP” and “Uplink AMC-QRAP”. The joint adaptation of the transmission power and the Modulation and Coding Scheme reliably interacts with the link quality on each allocated sub-channel. Two distinct user categories are considered to differentiate between different QoS levels required. Accordingly, a linear optimization model is performed for the problem resolution. A clustering approach proposed in the literature has been used as a tradeoff between centralized and distributed schemes. Particularly, we used the spectrum sensing technique as proposed on the physical layer to detect surrounding transmissions. After that, we tackle the physical layer “signal processing” techniques as an LTE enhancement approach. Thus, two contributions based on the “wavelet transform” (WT) are proposed. The “wavelet-based OFDM” technique is firstly proposed as an alternative transmission mode for both downlink and uplink of the LTE and beyond wireless systems. In fact, the OFDM suffers from several limitations in terms of PAPR, spectral efficiency, synchronization cost and the inter-carrier interference. We proved that with substituting the Fourier transform by the wavelet transform in the OFDM technique, the different OFDM limitations can be significantly overcame. Second, we proposed an enhanced spectrum sensing approach based on WT tool that accurately delimits the occupied resource blocks in the whole spectrum. These physical layer enhancements help improving the scheduling algorithm for the uplink proposed in our second contribution. Extensive network simulations with different network densities have been conducted, using several metrics such as spectral efficiency, throughput satisfaction rate, user outage and transmission power. We have compared our methods to several existing works in the literature and proved the outperformance for the different considered metrics.

Defence : 06/26/2014 - 15h - Site Jussieu 25-26/105

Jury members :

ACHIR Nadjib: Maître de conférence-HDR, Université Paris Nord [rapporteur]
ELAYOUBI Salah Eddine: Ingénieur de recherche-HDR, Orange Labs [rapporteur]
AL-AGHA Khaldoun: Professeur, Université Paris Sud
FLADENMULLER Anne: Maître de conférence-HDR, Université Pierre et Marie Curie
GHAITH Alaa: Maître de Conférence, Université Libanaise
NGUYEN Thi-Mai-Trang: Maître de Conférence-HDR, Université Pierre et Marie Curie
PUJOLLE Guy: Professeur, Université Pierre et Marie Curie

2014 Publications