Département Informatique et Réseaux

Soutenance de thèse

Lieu:Amphithéâtre B312 à Télécom ParisTech (46,rue Barrault –75013 Paris)

Membres du jury:

Rapporteurs:

• Raouf Boutaba (University of Waterloo,Canada)
• André-Luc Beylot (Université de Toulouse)

Directeur de thèse

• Nadia Boukhatem (Télécom ParisTech)

Examinateurs:

• Samir Tohmé (Université de Versailles)
• Elie Najm (Telecom ParisTech)
• Khalid Boussetta (Université de Paris 13)
• Thi-Mai-Trang Nguyen (Université de Paris 6)
• Erick Bizouarn (Alcatel-Lucent Bell Labs)

Abstract: “Exploiting Multipath for Mobile Terminals with Heterogeneous Multi-access”

Multi-interfaced mobile terminals may have the possibility to spread the traffic over multiple network interfaces and aggregate their resources. Ideally,this aggregation may provide better throughput to the applications as well as better transmission reliability.
Reliable transport layer ensures delivery of data by assigning sequence numbers to the transmitted packets. Upon reception,these packets are sorted back to their original order using their assigned sequence numbers,before being forwarded to the application layer.
However,using multiple paths for parallel data transmission may cause out-of-order data reception in transport layer mechanisms. This is principally due to the difference in characteristics of one path from the other. In a multipath communication where paths have vastly different characteristics,it becomes crucial that the data be received in-order so as to reduce packet reordering costs,and avoid fast-retransmission and head-of-the-line blocking problems.
This thesis deals with a multipath solution for multi-interfaced mobile terminals which enables the use of parallel data paths to achieve higher throughput as well as transmission reliability in heterogeneous wireless networks. First,a transport-layer multipath solution called \textit{Forward Prediction Scheduling} (FPS) is proposed. FPS alleviates the out-of-order data reception problem by estimating the delays incurred to data on each candidate path beforehand,and then scheduling the transmission of a data packet such that it is received in line with packets from other paths.
Preliminary performance evaluation of FPS is carried out using ns-2′s SCTP-CMT model. This is then followed by FPS implementation in Linux kernel version of SCTP (lkSCTP) and extensive tests using a mobile device with heterogeneous set of wired and wireless network interfaces. The results prove the performance improvements brought by FPS in face of high path delay ratios and dynamic wireless links.
A cross-layer extension of FPS mechanism is also proposed which contributes to accurate path delay calculations using layer-2 information in 802.11 wireless links.
Recently proposed multipath TCP (MPTCP) is a set of extensions to the original TCP which enables it to support multiple paths in a single transport connection. This thesis also presents a detailed compatibility study of the integration of FPS mechanism into MPTCP’s traffic scheduler.
Finally,a reliability-driven network coding-based multipath solution is proposed which enables a multi-interfaced host to transmit linearly encoded combinations of original data packets using its multiple paths. With the help of preliminary results,it is shown that the application of linear coding with FPS mechanism significantly improves data transmission reliability as well as leads to less out-of-order reception problem.