氏学位名

Jia Liu

名

博士（システム情報科学）

学 位 記 番 号

第３２号

学位授与年月日

平成２８年９月１６日

学位論文題目On the Performance of Two-Hop Relay Mobile Ad Hoc Networks
under Buffer Constraint

論文審査委員

主査 姜 暁鴻副査 藤野 雄一
副査 稲村 浩副査 佐藤 仁樹論

文 要 旨Mobile ad hoc network (MANET) represents a kind of self-organizing networkarchitecture, which consists of mobile devices communicating with each other overpeer-to-peer wireless links without centralized infrastructure. Since MANETs can bedeployed and reconfigured rapidly at very low cost, they are appealing for many criticalapplications, such as disaster relief, emergency rescue, battlefield communications,traffic offloading and cover extension for future 5G networks. To efficiently facilitate theapplication and commercialization of MANETs, understanding the fundamental
performance of such networks is of great importance.
The available performance studies for MANETs suffer from two major limitations.
First, they mainly focus on the asymptotic behaviors of network performance as thenetwork size tends to infinity, while the actual achievable performance is largely
uninvestigated. Second, to make their analysis tractable, these studies are usuallybased on the ideal assumption of infinite buffer, which does not hold for a practicalMANET. Therefore, it is important to have a thorough study on the actual achievable
performance of MANETs under the practical limited-buffer constraint.
For a general MANET with limited-buffer constraint, this thesis is devoted toexploring its actual achievable performance in terms of the throughput, end-to-end(E2E) delay and throughput capacity. We first consider the scenario with only therelay-buffer constraint, where each network node maintains a shared limited relaybuffer for storing relay packets of all other nodes. For such a MANET, we develop an
efficient theoretical framework to model its dynamic behaviors characterized by thebuffer occupancy process, packet source-queuing process and packet delivery process.
This theoretical framework is general since it applies to any distributed MAC protocol
and any mobility model that leads to the uniform distribution of nodes' locations in
steady state. With the help of this framework, we derive the exact expressions for boththroughput capacity and expected E2E delay. Case studies are further conducted under
two typical network scenarios to demonstrate the application of the proposed theoreticalframework.
We then extend our study to the MANETs where both the source buffer and relay
buffer are subject to the limited-buffer constraint. Based on the Queuing theory andbirth-death chain theory, we develop a general theoretical framework to fully depict theoccupancy processes of both source buffer and relay buffer, such that the corresponding
stationary occupancy state distributions (QSDs) can be derived. With the help of OSDs,
we further obtain the exact expressions of throughput, expected E2E delay andthroughput capacity. Finally, extensive simulations and numerical results are presented
to demonstrate the efficiency of the proposed theoretical framework and illustrate ourtheoretical findings. It is expected that the theoretical results developed in this thesis
will provide a useful guideline for the practical design and optimization of MANETs.

審査結果の要旨

This thesis studied the fundamental performance of an important class of two-hop relay
MANETs under the limited-buffer constraint, which represents a significant progress in theperformance study of practical MANETs. This thesis first considered the scenario with only therelay-buffer constraint and developed an efficient theoretical framework to characterize the relay
buffer occupancy process. With the help of this framework, the exact expressions of throughput
capacity and expected end-to-end (E2E) delay were derived. This thesis then extended theperformance study to the MANETs with both limited relay-buffer and relay buffer were analyzed,
which enables the exact expressions of throughput, expected E2E delay and throughput capacity tobe derived. All theoretical results were verified with extensive simulation results. It is expected thatthe results developed in this thesis will be helpful for the application and commercialization ofMANETs.

・論文の構成
Chapter 1 Introduction
Chapter 2 Related Works
Chapter 3 Preliminaries
Chapter 4 Throughput Capacity of MANETs under Relay-Buffer Constraint
Chapter 5 End-to-end Delay of MANETs under Relay-Buffer Constraint
Chapter 6 Throughput and Delay of MANETs under General Buffer Constraint
Chapter 7 Conclusion
Appendix A Proofs of Chapter 4Appendix B Proofs of Chapter 5
Appendix C Proofs of Chapter 6
・研究目的の妥当性，従来の手法との比較においての有意性，および理論・実験手法の新規性
This thesis studied the fundamental performance of an important class of two-hop relay
MANETs under the limited-buffer constraint, which is expected to provide precious insights to thedesign and optimization of future communication networks.
The available performance studies for MANETs suffer from two major limitations. First, theymainly focused on the asymptotic behaviors of network performance as the network size tends toinfinity, while the actual achievable performance is largely uninvestigated. Second, to make theiranalysis tractable, these studies were usually based on the ideal assumption of infinite buffer, which
does not hold for a practical MANETs. Different from these works, this thesis conducted a thoroughstudy on the actual achievable performance of MANETs under the practical limited-buffer constraint,
representing an important progress in the performance study of practical MANETs.
・得られた知見のシステム情報科学の分野における意義
The results of this thesis provide the following insights.
1. The novel theoretical frameworks developed in this thesis could be helpful for exploring theperformance in other MANET scenarios as well.
2. The theoretical findings revealed in this thesis could serve as the important guidelines for thedesign of practical MANETs with the limited-buffer constraints.