Download Understanding the Service Performance of Operational Small Cells Graduate Research

Understanding the Service Performance of
Operational Small Cells
Graduate Research
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Sharan Naribole , Zihui Ge , Edward Knightly , Ajay Mahimkar , Jia Wang , He Yan
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Rice University AT&T Labs Research
SMALL CELLS
TRAFFIC
HOTSPOT
COVERAGE
HOLE
P
1
• Abrupt Cell Boundaries
SERVING CELL
SIGNAL QUALITY
MACRO
CELL
CHALLENGES
MOBILITY MANAGEMENT
SMALL
CELL
USER TRAJECTORY
TARGET CELL
• Increased Neighboring Cell List
REPLY
• Targeted deployment
o Traffic hot spots and Coverage holes
o More cells in the vicinity of the user
o Limitation risks exclusion of cell with best signal quality
DISTANCE
• Difficult to deploy new macro cells
BENEFITS
• Improvement in area spectral efficiency
o Small cell either as serving cell or target cell reduces the
handover region compared to a only macro cell scenario
o Small cell to Small cell handovers are worst-affected
REPLY
HANDOVER
OUTAGE
ENTRY
HANDOVER REGION
• Increase in the number of handovers with small cells
KEY QUESTION
HANDOVER
FAILURE
• Types of handovers: (i) Macro-to-Small (ii) Small-to-Macro
(iii)Small-to-Small and (iv) Macro-to-Macro
What are the implications of small cell deployment on
the service performance of an operational cellular
network?
IMPORTANCE
• The first detailed large-scale measurement study of voice and data service performance of a nation-wide operational small cell network
• Foundation for future studies of mobility management and development of techniques for improvement of service performance of operational small cell networks
VOICE SERVICE
• Anonymized call detail records collected over 14 days
• Over 500,000 calls involving over 1,500 small cells
• Start time | Call trajectory | Cause code of termination | Airtime for each cell
DATA SERVICE
• Tourist location with relatively higher traffic demand and user mobility and thus
relatively higher number of small cells deployed - 53 small cells and 5 macro cells
• Hourly cell-level service quality measurements for a period of three months
SERVICE PERFORMANCE
MACRO CELL - SMALL CELL INTERACTIONS
• Call drop probability employed as a measure of service performance
METHODOLOGY
• Mobility pattern - Mobile call or Stationary call
• Terminating cell - Small cell or Macro cell
• Final Cell Time - Time spent in the terminating cell
RESULTS
• 84.7% of the calls do not involve any handovers
o Adds confidence to the capacity and coverage impact of small cell
• 0.05% of the mobile calls had Small-to-Small handovers
o Neighboring macro cell better qualifies as target cell
o High small cell to small cell handover failures
• Traffic offload to small cells is as large as 50.4%, a significant fraction of total traffic
• Small cell deployment reduces likelihood of macro cells entering congestion state
SERVICE PERFORMANCE
• Retainability is a measure of successful termination as issued by the user
• Call drop probability is the highest for a mobile call terminating in a small cell
independent of the airtime
o Abrupt cell boundaries
o The probability that the user moves out of the cell increases with time. Also, the probability
of the call ended by the user increases with time.
METHODOLOGY
SYMPTOM
EVENT
EVENT
FORMATION
DATA
SANITIZATION
OTHER
EVENTS
STATISTICAL
CORRELATION
TEST
RESULTS
• Small-to-Small Handover failure percentage has the
highest correlation with Retainability degradation
• Widespread Impact
o More than 84% of the small cells in the tourist location have
a significant negative correlation between Small-to-Small
handover failure percentage and Retainability
SIGNIFICANT
CHANGES