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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