presentation structure historic cell site analysis ...prashk/inf3350/f12/september_12_1.pdfhistoric...
TRANSCRIPT
Historic cell site analysis – Overview of principles and survey
Presented by Xiao MA
Presentation Structure ! Introduction of CDR ! Mobile network brief ! Access service area ! Data interpretation ! Experiments and results
I. INTRODUCTION of CDR ! CDR=Cell Data Records, stored by
network provider ! Different from your photo, video, music
or local data of social network apps ON YOUR PHONE.
! Generally, CDR records relevant data and info about calls and texts the network operator handles.
Information about CDR ! Time and date of the call ! Phone numbers ! Cell ID of the site where the call begins
and ends ! Generally, only answered calls/texts are
recorded. They are meaningful records.
2.Mobile phone networks-brief ! Cell site ! Sector ! Service/range ! Cell selection(important topic)
Cell site ! In brief, a set of physical devices,
deliberately located and operated to serve a particular area.
Theoretic service area
Cell site
Sectors ! Each cell operates as 3 independently
working Sectors. ! The service area of a sector depends on
geographic characteristics
1
2
3
Theoretically Actually
Service and range ! The service area of a cell, generally,
depends on height of antenna, power, location of other cells and geographic features of the land.
! Range varies from 50m~35km(theoretic limitation of GSM)
! Generally less than 20km for rural area, less than 5km in urban area, 2km in city center.
Cell selection ! The following slides introduces: ! How to pick a cell ! Issues when need to move to another cell
How to pick a cell--1 ! In every “cell site”, there are some area, in
which the cell has significant signal advantage over the signal from other cells
! This is the dominant area. ! Handsets in the dominant area of a cell
are most likely to pick this cell. ! Generally, a handset in the DA of a cell
has line sight to the antenna.
How to pick a cell—2 ! In a cell’s non-dominant area, there may
be several cell signals competing each other.
! Handsets may change the cell serving it in non-dominant area frequently. Unnecessary changes are NOT desired in application.
Move to a new cell—1 If a new cell: ! Has significant power advantage to the
current cell ! And this advantage lasts for a period of
time In IDLE MODE, the handset may move itself to the new cell. This approach avoids frequent PingPong.
Move to a new cell—2 ! During a call(DEDICATED MODE), a
handset may still need to move to a new cell for better signal.
! In this case the network core need to make a decision for this.
! The network may shift the call so that the call is not affected while the handset is moving to a new cell.
Moving to a new cell—3 ! Sometimes a handset need to move to a
new cell because current cell is congested—current cell say NO to handset albeit current cell may have unparalleled signal advantage.
! Direct retry or BA list
Moving to a new cell—3.1 ! Direct retry: handset manually detect
feasible alternative cells and try connect a cell of them. This action may need network operator consent.
! BA list: Broadcast control channel Allocation list. This list is provided by operator. Handset will only find alternative cells in the BA list.
Presentation Structure ! Introduction of CDR ! Mobile network brief ! Access service area ! Data interpretation ! Experiments and results
3. Assess Service Area ! To know the area over which a particular
cell could be expected to provide service. ! Need to consider a lot of factors ! Theoretic modeling and calculation not
sufficient ! Need precise measurement
Method 1:BSPs ! BSP: Best Server Prediction Plots ! Network Operator calculates which cell
has higher signal strength ! May underestimate the power of other
cells ! Result may be inexact ! Hard to track change with time
Method 2: RF mesurements(Survey)
! Spot sample: single/a few measurement(s) specific point, specific time
! Location sample: some measurements, specific point, period of time
! Area survey: large number of measurements, area, time:N/A, may with GPS
! Cell survey: very large number of measurements, large area, with GPS
Other RF surveys ! Drive survey: may need specific designed
route. ! Walk survey: similar to drive survey, but at
vehicle inaccessible area
4 Interpreting data ! A lot of factors to consider ! Neighbor cells may serve in the non-
dorminant area of another cell site ! Neighbor data must be considered, but
not as primary data. ! Last cell ID may indicate larger service
area due to different cell selection scheme during dedicative mode.
Ex of Derived service area
! Red: this cell serves these area ! Yellow: this cell considered as handover
candidate
Interpreting data ! For drive survey, the derived service area
can be determined by the observations indicating cell service.
! Determination based on subjective judgment, opinion based.
! ‘derived service area’ is not rigorous judgment.
Presentation Structure ! Introduction of CDR ! Mobile network brief ! Access service area ! Data interpretation ! Experiments and results
5. Experiments and results ! 2 positions 5m apart in a car park, testing
UK 2G network. ! Using: Crownhill Netmonitor System,
TEMS survey equipment, Engineering handset
Experiments ! Ex1: 5 minute data from Position1 then 2 ! Ex2: location sample from 1 and 2 for 1h
respectively ! Ex3: Spot and Location Samples on 1&2
for 1h, and an area survey of 300 meters from the car park.
! Observe whether cell IDs are providing service, as handover candidate, or not included.
Experiment Summery Ex1 ! Cell IDs monitored by a STATIC sampling
device change over time, as well as between similar devices.
! No single individual device detect all ‘legitimate’ cell IDs either as serving or neighbor.
Experiment Summery Ex2 ! Lengthening a static sample period to 1h
does NOT necessarily generate more consistent or accurate data.
Experiment Summery Ex3 ! Area survey produces most consistent
data ! Most cell ID detected, but still most
consistent
Survey methods pros and cons Survey method Pros Cons Spot sample speed Great variety, false
exclusives Location 5m speed, consider
time period Great variety
Location 1h Speed, consider time period
Slightly less variety than above
Area Minimize non-dominant area inconsistency, clear indication
Complicated massive date generated
Cell Demonstrating the cell service area
Not mentioned in the paper
Questions and doubts ! This paper never mentioned how TEMS
and Engineering handsets are used. ! This paper has confusion expression of
data in Ex1. ! This paper does not quantize the data
before making the solution. They should weight the data and process them by some math to make it.
Question time~