MOBILITY MANAGEMENT FOR FEMTOCELLS IN

LTE-ADVANCED

SURVEY PAPER

Dr. Dionysis Xenakis

National and Kapodistrian University of Athens

November 2018

PART 1

1

HETEROGENEOUS WIRELESS NETWORKS

THE CURRENT STATE OF PLAY

Single-tier operator-deployed CS systems =>

Multi-tier networking clusters of user-installed IP-based WNEs

Heterogeneous communication capabilities and diverse networking requirements

Today’s HWN is a collection of

Tower-mounted cellular base stations (BSs)

Small-sized base stations in the licensed or the unlicensed spectrum

Low-cost low-power and battery-operated sensors2

HETEROGENEOUS WIRELESS NETWORKS

DISCOVERY AND ASSOCIATION

The mobile terminals (or WNEs)

Discover the nearby WNEs that they can access

Associate with the one(s) that meet their particular communication requirements

Different terms and methodologies are used

Discovery: Cell Search (3GPP), Network Discovery (IEEE), Peer Discovery

Association: Handover (intra-system) or Vertical Handover (inter-system)

Discovery and Association are integral part of Mobility Management (MM) for all systems

3

HETEROGENEOUS WIRELESS NETWORKS

MOBILITY MANAGEMENT CHALLENGES

Mobile terminals support multiple RATs Candid. PoA, increased complexity and consumption

Direct exchange of localized traffic (P2P/D2D) Emerging applications such as SN, MMOG, D2D, SM,

FRC, Unsupervised navigation of robotic nodes

User-assisted network-controlled MM approach (??)

Unplanned and densely overlappingdeployment of different-purpose WNEs Semi-autonomous terminal-based discovery

Stochastic system dominated by spatial dependencies

4

HETEROGENEOUS WIRELESS NETWORKS

ENHANCED MEASUREMENT CAPABILITIES

Enhanced measurement capabilities

Assess the ambient radio environment

Estimate their physical distance and angle to other WNEs

Knowledge of the radio status or the spatial dependencies between the WNEs

Enhanced mobility, interference, and energy mgmt

Accurate localization between the WNEs

Localization

Relative distance (or connectivity) to other WNEs

Vital component in the future 5G network 5

MOBILITY MANAGEMENT FOR FEMTOCELLS

RELATED REFERENCES

1. D. Xenakis, N. Passas, L. Merakos, and C. Verikoukis,"Mobility Management for Femtocells in LTE-Advanced: Key Aspects and Survey of HandoverDecision Algorithms", IEEE Surveys and Tutorials,vol.16, no.1, pp.64-91, First Quarter 2014.

2. D. Xenakis, N. Passas, L. Merakos, and C. Verikoukis, "HandoverDecision for Small Cells: Algorithms, Lessons Learned andSimulation Study", Computer Networks, Elsevier, Vol. 100, pp 64-74, May2016.

3. D. Xenakis, N. Passas, L. Merakos, and C. Verikoukis, "AdvancedMobility Management for Reduced Interference and EnergyConsumption in the Two-tier LTE-Advanced Network", ComputerNetworks, Elsevier, vol. 76, pp. 90-111, Jan 2015.

4. D. Xenakis, N. Passas, and C. Verikoukis, "�An Energy-CentricHandover Decision Algorithm for the Integrated LTE Macrocell -Femtocell Network Computer Communications", Comp. Comm.,Elsevier, vol. 35, is. 14, pp. 1684-1694, Aug. 2012.

6

MOBILITY MANAGEMENT FOR FEMTOCELLS IN LTE-A: KEY

ASPECTS, SURVEY OF HO DECISION ALGORITHMS, LESSONS

LEARNED AND SIMULATION STUDY

Overview and State-of-the-Art

Small Cells, Femtocells, LTE-Advanced, Key research challenges for Interference, Mobility and Energy Mgmt

Mobility Management for femtocells: Open Issues and Implementation in LTE-A (Part I)

Network architecture - Support of femtocells

Cell Identification, Access Control, Cell Search, Cell Selection/Reselection, HO Decision, HO Execution

Handover Decision for femtocells in LTE-A (Part II)

Decision Criteria, Classification and Survey of Algorithms

Performance and Modeling Issues, Lessons Learned

Qualitative and Quantitative Performance Comparisons

7

SMALL CELLS

Smoothly integrate small-sized stations

Small Cells

Short-range, low-power and cost cellular access points

Support fewer users compared to macrocells

Embody the functionality of a regular base station

Operate in the mobile operator’s licensed spectrum

Promising solution for supporting the plethora of emerging home/enterprise apps

Include pico, micro, metro cells: Operator-managed

Include femtocells: installed/managed by the users8

FEMTOCELLS

Special case of small cells [1]

Installed/managed by the users

Utilize existing broadband backhaul to reach the mobile operator’s network, e.g., xDSL

Support up to a few users, e.g. 4 users

Low power operation, e.g. up to 20dBm

Are subject to access control

Feature edge-based intelligence

Self-x capabilities, advanced radio resource, mobility and interference management

9

FEMTOCELL DEPLOYMENT EXAMPLE

10

FEMTOCELL BENEFITS

Mobile Operator Perspective

Reduce the Capital and Operational Expenditure

Improve indoor coverage and system capacity

Result in higher spatial frequency reuse

Lower power transmissions

Decongest nearby macrocells

User Perspective

Improved indoor coverage

Enhanced system capacity – end throughput

Prolonged handset battery lifetime

Preferential charging11

FEMTOCELL OPEN ISSUES

Business Models / Access Methods [1][13]-[14]

Radio Resource Management [15]-[17] Resource Allocation and Power Control

Energy Saving Management [18]-[22] Network : Component and System Level ES

User side: Enhance the UE energy-efficiency Discontinuous Reception (DRX) [30]-[32]

Interference Management [2] [23]-[29]

Self-organization, configuration and healing [1]

Location Management [38]

Mobility Management [33]-[61] [69]-[73]

Performance Analysis [62]-[64] [41]-[43] [48] 12

PART I: MOBILITY MANAGEMENT FOR

FEMTOCELLS IN LTE-A

Overview of Part I

Motivation

Support of Femtocells in LTE-A

Discuss the key aspects and research challenges Cell Identification

Access Control

Cell Search

Cell Selection / Reselection

Handover Decision

Handover Execution13