Take a ride through a subway's wireless network design

IN WHAT CITY DO METRO CARS HAVE CARPET FLOORING?

A) Beijing, China

B) Bucharest, Romania

C) Washington, D.C, USA

Subway's Wireless Network Design #iBwaveTalks

A) NEW YORK CITY, USA

WHAT IS THE WORLD’S LARGEST METRO (PASSENGER-ROUTE LENGTH)?

B) SEOUL, SOUTH KOREA

C) LONDON, ENGLAND


A) 532 FT

KIEV, UKRAINE HAS THE DEEPEST METRO STATION – HOW DEEP UNDERGROUND IS IT?

B) 187 FT

C) 346 FT


A) LONDON,ENGLAND

WHAT CITY HAS THE MOST METRO STOPS?

B) SHANGHAI, CHINA

C) NEW YORK, USA


A) 400 METERS

A TRAIN TRAVELING 100 KM/H OVERTAKES AMOTORBIKE TRAVELING 64 KM/H IN 40 SECONDS. HOW LONG IS THE TRAIN?

B) 1822 METERS

C) 1011 METERS


A) NEW YORK CITY, USA

WHAT CITY HAD THE WORLD’S FIRST METRO?

B) LONDON, ENGLAND

C) MOSCOW, RUSSIA


A) SHANGHAI, CHINA

WHAT CITY HAS THE BUSIEST METRO SYSTEM?

B) TOKYO, JAPAN

C) MOSCOW, RUSSIA


A) 14

HOW MANY OF THE WORLD’S 180 METRO SYSTEMS HAVE DRIVERLESS TRAINS?

B) 30

C) 46


A) MONTREAL, CANADA

WHAT CITY HAS WHAT’S CONSIDERED THE MOST BEAUTIFUL STATIONS IN THE WORLD?

B) TOKYO, JAPAN

C) MOSCOW, RUSSIA


A) CHICAGO, USA

IN WHAT CITY ARE THERE METRO CARS RESERVED SPECIFICALLY JUST FOR WOMEN?

B) ISTANBUL, TURKEY

C) TOKYO, JAPAN


A) 2 CENTS

HOW MUCH DID IT COST TO RIDE THE NYC SUBWAY WHEN IT OPENED IN 1904?

B) 10 CENTS

C) 5 CENTS


A) 10 CENTS

AND WHAT DID IT COST TO RIDE THE NYC SUBWAY 44 YRS LATER, IN 1948?

B) 25 CENTS

C) 50 CENTS


A) THIRD RAIL

WHAT IS THE COMMON NAME GIVEN TO THE SOURCE OF ELECTRICAL POWER FOR A SUBWAY CAR?

B) SECOND RAIL

C) WHITEBOX


A) BUDAPEST, HUNGARY

IN WHAT CITY DO THE SUBWAY TRAINS RIDE ON RUBBER WHEELS?

B) NEW YORK, USA

C) PARIS, FRANCE


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#iBwaveTalksPRESENTED BY: VLADAN JEVREMOVIC, PhD RESEARCH DIRECTOR

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GLOBAL SOLUTIONS FOR IN-BUILDING NETWORK DESIGN & WIRELESS LIFECYCLE MANAGEMENT



Subways around the world Target areas for IBS coverage Design Requirements Best Practices

3D modeling Tunnels Environmental concerns Capacity dimensioning

IBS Solution RF Coverage maps Conclusion Q&A

AGENDA


BUSIEST UNDERGROUND TRANSIT SYSTEMS

#2

2.5Bpassenger

s /year

#3

2.5Bpassengers

/year

Tokyo Seoul Beijing Shanghai

#5

2.3Bpassenger

s /year

#1

3.2Bpassenger

s /year

#4

2.4Bpassengers

/year

Moscow

SOURCE: Wikipedia


LARGEST UNDERGROUND TRANSIT SYSTEMS

#2

429stations

#3

300stations

NYC Seoul Paris Shanghai

#5

292stations

#1

468stations

#3

300stations

Madrid

SOURCE: Wikipedia


100-150passengers

/car

1,200passengers

/train

36,000passengers

/hour

80,000passengers

/hourMTR in Hong

Kong

Average capacity

Record capacity

WORLDWIDE UNDERGROUND TRANSIT STATS

SOURCE: Wikipedia


TARGET AREAS FOR IBS RF COVERAGE

Entry Hall

Ticket Booth Escalators Hallways Stairways


Car

Platform

TunnelTrain

TARGET AREAS FOR IBS RF COVERAGE


DESIGN REQUIREMENTS: RF COVERAGE

Train station GSM, UMTS, LTE, Public safety, WiFi

Tunnel GSM, UMTS, LTE WiFi not required Public safety must have coverage in

the worst case scenario

Minimum IBS signal requirements: GSM BCCH = -85 dBm UMTS RSCP = -85 dBm LTE RSRP = -95 dBm WiFi Rx = -75 dBm


BEST PRACTICES: 3D MODELING

Video stream

• IBS signal propagates horizontally through platforms, but also vertically, between platforms

• Signal overlap between platforms should be kept to minimum• 3D modeling of multilevel train station is essential


BEST PRACTICES: 3D MODELING

Video stream

• Train cars need IBS coverage• Signal propagates only through windows• Window height, length and position is

essential to assess RF coverage • 3D models of trains must be included at

station and in tunnels


BEST PRACTICES: TUNNEL COVERAGE• Radiating cables are often used in tunnels, mounted

at side wall at train window height• Remote Units (RU) or eNodeB are used to feed the

cable

• Pathloss example: Eupen RMC 78-HLFR @ 1900 MHz• 69 dB coupling loss @ 2 meters• 10 W RU power feeding the cable (40 dBm)• -85 dBm target receive power • 5 dB window penetration loss• Max cable loss: 40-(-85) – 5 -69 = 61 dB• @ 6.4 dB loss/100 meters, max cable length = 800

meters

• Two cable runs from each end can cover up to 1.6 km

• If a tunnel is longer, then cascading RUs may be used to extend the coverage (but watch out for UL noise!)


BEST PRACTICES: TUNNEL MULTIPATH SIGNAL DELAY• If multipath delay at the receiver is greater than

expected, SINR is degraded

• 3GPP standard defines UMTS search window delay settings:• 40 (20) chip delay 20/3.84Mcps = 5.2 ms 1.56 km• 256 (128 )chip delay 33.3 ms 10 km• 2560 (1280 )chip delay 333 ms 100 km• If cascaded cable length 1.5 km, search window = 256

• 3GPP standard defines LTE Cycle Prefix settings• Cycle Prefix (CP) is transmission gap between OFDM

symbols• CP duration defines tolerable multipath delay• 5.2 ms 1.56 km • 16.7 ms 5 km• If cascaded cable length 1.5 km, CP =16.7 ms


BEST PRACTICES: TUNNEL HANDOFF

• If radiating cables from the opposite end of tunnel meet in the middle, UE must hand off from one sector to another• A handoff takes 2-3 seconds to execute• UE must be allowed multiple attempts to

handoff before failing and dropping the call

• Example: • Train speed 36 km/h (10 m/s)• 10 seconds is budgeted for handoff completion sector overlap is 100 meters

• The length of sector overlap depends on:• Train speed• The number of allowed handoff attempts


BEST PRACTICES: TUNNEL – PUBLIC SAFETY

Worst case scenario:• Double track tunnel• Trains stop next to each other• If public safety has one radiating cable, the

train near the opposite wall may experience RF coverage outage

• In a double track tunnel, public safety radiating cables should be installed at both walls to insure “worst case” scenario coverage

• Commercial networks need not plan for “worst case” scenario, can have cables on one wall only


BEST PRACTICES: ENVIRONMENTAL CONCERNS

Video stream

• Tunnels are often damp, dusty and prone to frequent but short AC power outages• All cable connections should be

waterproofed• Use power converter to filter out

instabilities• Tunnel vibrations cause PIM in loose cables • Keep in mind that dust also causes PIM• Keep antennas away from metallic objects,

including train roof!

• Choose equipment location with visibility and maintenance in mind• A small room accessible at all times is a

better choice than big room accessible only after hours

• If rush hour commuters can see IBS equipment, so can late night vandals


BEST PRACTICES: CAPACITY DIMENSIONING

Video stream

User profiles

• User profiles must include• Type of service (voice, email…)• Venue specific average call duration per

user (mE) during busy hour• Data rate

• Key assumptions: • All listed services are used by every

subscriber during busy hour • Some subscribers may be denied service

due to network congestion• The goal: Calculate call rejection

(blocking) for every service type based on• Number of subscribers • Call duration & call data rate

LTE user profileService type mE/User kbpsEmails 50 100Browsing 100 200Video conf 20 600Data Download 150 1000Video Streaming 100 2000



Video stream

How many commuters?

• Assume the worst case scenario:• Two trains at each platform (4 trains total)• Each train has 10 cars• Each car carries 150 passengers (limit)• Up to 1,000 in shops near or inside entry hall Total of 4*1,500+1,000 = 7,000 commuters at

the station

• Assume more trains are nearby• Two trains approaching the station Total of 2*1,500 = 3,000 commuters in tunnels

• Total of 10,000 commuters need to be supported by IBS at the station



Video stream

How many subscribers per Wireless Service Provider? • Total of 10,000 commuters:

• WSP A: 30% penetration rate• GSM: 5%• UMTS: 35%• LTE: 60%

• WSP B: 25% penetration rate• GSM: 5%• UMTS: 40%• LTE: 55%

• WSP C: 25% penetration rate• GSM: 5%• UMTS: 45%• LTE: 50%

• WSP D: 20% penetration rate• GSM: 10%• UMTS: 60%• LTE: 30 %

station tunnel station tunnel station tunnelWSP A 105 45 735 315 1,260 540WSP B 88 38 700 300 963 413WSP C 88 38 788 337 875 375WSP D 140 60 840 360 420 180

GSM UMTS LTE


BEST PRACTICES: CAPACITY DIMENSIONINGLTE: Establish a link between MCS efficiency and

SINR

• 3GPP defines relationship between CQI, modulation and spectral efficiency

• Relationship between SINR and CQI can be obtained from vendors or from scientific papers

From TS 136 213


BEST PRACTICES: CAPACITY DIMENSIONINGLTE: MCS efficiency vs. SINR

• Combining the previous two tables we get spectral efficiency vs. SINR table for all CQI values and modulation types (15 entries)

• A simplified table with 4 entries:

• For simplicity, only the table with 4 entries is used further in this exercise

CQI Modulation MCS effi ciency SINR6 QPSK 1.18 39 16QAM 2.40 912 64QAM 3.90 1515 64QAM 5.55 20



LTE: How many Physical Resource Blocks?• Use simplified table with 4 SINR ranges• Each SINR range has different spectral

efficiency• PRB data rate = MCS efficiency * # of PDSCH

RE/1ms • Calculate number of PRBs per service per SINR

range

• Example: video conferencing needs 4 PRBs in SINR Range 1

Number of PRBs

CQI Modulation MCS effi ciency SINR6 QPSK 1.18 39 16QAM 2.40 912 64QAM 3.90 1515 64QAM 5.55 20

Service Type Range 1 Range 2 Range 3 Range 4Emails 1 1 1 1Web Browsing 2 1 1 1Video Conferencing 4 2 2 1Data Download 6 3 2 2Video Streaming 12 6 4 3

LTE user profileService type mE/User kbpsEmails 50 100Browsing 100 200Video conf 20 600Data Download 150 1000Video Streaming 100 2000


BEST PRACTICES: CAPACITY DIMENSIONINGLTE traffic at the station?

• Calculate SINR coverage map• Break SINR coverage into 4 SINR ranges

• WSP B: Approximately 1,000 LTE subscribers • Number of subs/range is proportional to SINR

coverage • Offered traffic (E)= number of subscribers * call

duration

• Total offered traffic = 420 Erlangs

SINR coverage

Metrics Range 1 Range 2 Range 3 Range 4SNIR 3 9 15 20Distribution 10.0% 20.0% 20.0% 50.0%subscribers 100 200 200 500emails 5.0 10.0 10.0 25.0browsing 10.0 20.0 20.0 50.0video conf 2.0 4.0 4.0 10.0data download 15.0 30.0 30.0 75.0video streaming 10.0 20.0 20.0 50.0


CAPACITY DIMENSIONINGCall blockage calculation

• We try to “populate” an LTE frame with PRB packets of various size • SINR range and minimum service data rate

affect the packet size; email needs 1 PRB, video streaming 3-12

• The number of available PRBs in LTE frame depends on RF channel size (500 RBs in 10 MHz)

• The formula to calculate blocking for N concurrent data sessions is given in ITU-R.M. 1768-1 recommendation

rm = traffic in Erlangs for mth data service

nm = number of PRBs for mth data service

Ncs = number of different data services

ITU-R call blocking

Bn = Blocking rate for nth data service


CAPACITY DIMENSIONINGEncountered blocking rate

• Blocking rate is calculated for each service in each SINR range

• If a particular data packet length cannot fit into a frame, it is rejected/blocked

• Higher data rate services require more PRBs per packet and have greater blocking rate

ITU-R call blocking

Service Type Range 1 Range 2 Range 3 Range 4Emails 2.1% 2.1% 2.1% 2.1%Browsing 4.2% 2.1% 2.1% 2.1%Video conf 8.3% 4.2% 4.2% 2.1%Data Download 12.2% 6.2% 4.2% 4.2%Video Streaming 23.5% 12.2% 8.3% 6.2%


CAPACITY DIMENSIONINGCarried data traffic

• Carried data is offered data that is not blocked• Carried data traffic (E) =(1-blocking %) *Offered traffic (E)

• Total carried traffic = 398 Erlangs• Based on Carried data traffic, we calculate

• composite call blocking (5.2%) • data usage (150 GB)• duty cycle (39.8%)

Service Type Range 1 Range 2 Range 3 Range 4Emails 4.9 9.8 9.8 24.5Browsing 9.6 19.6 19.6 48.9Video conf 1.8 3.8 3.8 9.8Data Download 13.2 28.1 28.7 71.9Video Streaming 7.6 17.6 18.3 46.9


IBS SOLUTION The key requirement

• All WSPs must be included in IBS • WSPs don’t share small cells• Building separate network for each WSP is

impractical

Optimum solution: Distributed Antenna System

Video streamAnalog / Digital

Power Amplifier

Splitters, dividers,

coax cables

Analog / Digital

Digital / Analog

Power Amplifier

RF Source

Passive

Active

Splitters, dividers,

coax cables

antenna

antenna

RF / Combining

RF Source

Analog / Digital

Digital / Analog

Power Amplifier

antenna

antenna

RF Source

RF / Combining


RF COVERAGE MAPSTunnel: GSM coverage, two trains


RF COVERAGE MAPSPlatform 1: GSM coverage, two

trains


RF COVERAGE MAPSPlatform 2: GSM coverage, one train


RF COVERAGE MAPSTrain station, GSM coverage


RF COVERAGE MAPSTrain station, LTE SINR


RF COVERAGE MAPSTrain station, LTE MADR


SUMMARY

Subways around the world Target areas for IBS coverage Design Requirements Best Practices

3D modeling Tunnels Environmental concerns Capacity dimensioning

IBS Solution RF Coverage maps

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Contact Vladan Jevremovic, Research Director at [email protected]

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Take a ride through a subway's wireless network design