論文 / 著書情報
Article / Book Information
題目(和文)
Title(English)

Periodic Handover Skipping in Cellular Networks and Its Stochastic
Geometry Analysis

著者(和文)

徳山喜一

Author(English)

Kiichi Tokuyama

出典(和文)

学位:博士(理学),学位授与機関:東京工業大学,
報告番号:甲第12655号,
授与年月日:2024年3月26日,
学位の種別:課程博士,
審査員:三好 直人,金森 敬文,髙邉 賢史,中野 張,府川 和彦

Citation(English)

Degree:Doctor (Science),
Conferring organization: Tokyo Institute of Technology,
Report number:甲第12655号,
Conferred date:2024/3/26,
Degree Type:Course doctor,
Examiner:,,,,

学位種別(和文)

博士論文

Category(English)

Doctoral Thesis

種別(和文)

論文要旨

Type(English)Summary

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（博士課程）Doctoral Program論 文 要 旨ＴＨＥＳＩＳ ＳＵＭＭＡＲＹ

系・コース：
Department of, Graduate major in

学生氏名：
Student’s Name

数理・計算科学
数理・計算科学
徳山 喜一

系コース

申請学位（専攻分野）：

博士

Academic Degree Requested

Doctor of

審査員主査：
Chief Examiner

（理学 ）

三好 直人

要旨（英文 800 語程度）
Thesis Summary （approx.800 English Words ）Stochastic geometry is the study of random spatial patterns. Such random structures have been recognized toplay a key role in various fields such as cosmology, ecology, cell biology, engineering, and data sciences. One
substantial essence in the field of stochastic geometry is the theory of spatial point processes, which are thetools to represent the random allocation of points in a certain given space. The spatial point processes havebeen applied to various contexts in the real world, for example, random arrivals of customers, distribution ofEarthquake locations on the whole world.
This thesis studies applications of the stochastic geometry to the handover management problem in wirelesscellular communication networks. Handover management has attracted attention of research in the context ofwireless cellular communication networks. One crucial problem of handover management is to deal with increasing
handovers experienced by mobile users. To address this problem, handover skipping techniques have been studied
in recent years. For example, a fundamental handover skipping scheme, which we call alternate handover skipping,
was introduced, where a moving user alternately performs handovers along its trajectory, thereby enabling thehandover rate to be reduced to half. Another handover skipping scheme, called topology-aware handover skipping,
was proposed, where the handover skipping is triggered according to the distance from the moving user and its
target base station and the size of the cell. In this thesis, we propose yet another handover skipping scheme,
called periodic handover skipping. In the proposed scheme, handovers of a mobile user are controlled by a certain
fixed period of time, which we call skipping period. The skipping period can be managed as a system parameter,
thereby enabling flexible operation of handover skipping.
We first investigate the periodic handover skipping scheme on a basic model of a single-tier cellular network,where base stations in the cellular network are deployed according to a homogeneous Poisson point process.
Homogeneous Poisson point processes are often associated with point patterns that do not have any interaction
between points. We then provide a tractable framework for analyzing the periodic handover skipping scheme. Undera random walk model of user mobility, we derive the analytical expressions of the two performance metrics, thehandover rate and the expected downlink data rate. Moreover, by using these two metrics, we construct a utility
metric representing transmission performance, regarding the trade-off relation between the handover rate andthe data rate. Based on this utility metric, we conduct performance comparison between two scenarios where theperiodic handover skipping scheme is introduced and not introduced.
We next study the optimal skipping period on the same single-tier cellular network model and consider maximizing
the utility metric by controlling the skipping period introduced in the periodic handover skipping scheme. We
numerically observed that there exists an optimal value of the skipping period, which locally maximizes theutility metric. We investigate the impact of other system parameters on the optimal skipping period. Moreover,
we attempt to derive an approximate expression of the optimal skipping period. We also conduct numericalcomparison with some other handover skipping techniques.
We further study the periodic handover skipping scheme on a two-tier cellular network based on a homogeneous
Poisson point process and a Poisson-Poisson cluster process. Poisson-Poisson cluster processes are often used
to model clustered nodes in a network, for example, small base stations deployed organically to complement thecapacity of the cellular networks at user hotspots. Inside the network, we consider a random walk-based user
with the periodic handover skipping technique. Based on the system model, we provide analytical results for thetwo performance metrics, the handover rate and the expected data rate, which are derived via the exact and theapproximate analyses, respectively. In the numerical experiments, we found the values of the performance metrics
behave differently compared to the case of the single-tier cellular network model. In addition, we conduct
another numerical experiment to verify the efficiency of our proposed model in the two-tier cellular network.
We believe that our studies in this thesis could give some fundamental insights to the handover management
problem. However, those studies still have various points that need extension. For example, we considered adeterministic length of the skipping period, which could be enhanced to the random skipping period. Although we
focused on optimizing the performance of a single user, incorporating multiple users in this model is essential
for capacity management and load balancing in cellular networks. For further study, we could consider
incorporating the current wireless technologies in 5G, such as the inter-cell interference coordination, into
the periodic handover skipping scheme. Moreover, this handover skipping scheme might contribute to the handover
management problem in the unmanned aerial vehicle assisted cellular networks and the beam management problem inthe millimeter-wave cellular networks.
備考 : 論文要旨は、和文 2000 字と英文 300 語を 1 部ずつ提出するか、もしくは英文 800 語を 1 部提出してください。
Note : Thesis Summary should be submitted in either a copy of 2000 Japanese Characters and 300 Words (Engｌish) or 1copy of 800
Words (English).
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Website (T2R2).