connecting the corporate hq

PRESENTED BY: VLADAN JEVREMOVIC, PhD RESEARCH DIRECTOR

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CONNECTING THE CORPORATE HQ #iBwaveTalks

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In-Building wireless solutions specialist

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

Small Cell Industry Awards 2014Small cell tool design &technology innovation


• Campus description• Design Requirements• Best Practices

• RF survey• 3D modeling• Signal containment• Elevator coverage• Handoff management

• IBS Solution• RF Coverage maps• Conclusion• Q&A


54/16/2015CONNECTING THE CORPORATE HQ #iBwaveTalks

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Common features• Off major road/street• Multistory buildings• Small building separation

• One company may reside in all buildings, or…

• … Two or more companies may share the campus, or…

• …Two or more may share a building

• RF coverage from macro BTS• Minimal wireless traffic

outside business hours


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One companyTwo buildings• Building A: 10 levels• Building B: 5 levels• Distance: 30 meters

Poor wireless service• Slow data connection

No preferred carrier• Employees use their own

personal phones


RF Coverage• UMTS, LTE, Public safety required in IBS• IBS signal must be dominant

• The signal should be 5-7 dB stronger than the residual macro

• Minimum IBS signal requirements:• LTE RSRP = -95 dBm• UMTS CPICH = -85 dBm• Public safety Rx = -95 dBm

• Stairwells and elevator must be includedInterference management• Minimize IBS signal leakage outdoors• Minimize IBS sectors’ overlap• Limit handoff occurrences


Public Safety has additional design requirements• Technological

• Needs more extensive coverage than WSPs (loading docks, electrical rooms, freight elevators…)

• Needs redundancy• PIM: PS in SMR band (800 MHz) may affect UL cellular

band (850 MHz)• Regulatory

• PS requires waterproof NEMA 4X enclosures• Judicial

• PS must be controlled and maintained by PS authority


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RF survey• Residual macro signal determines IBS

design target• IBS signal should be 5-7 dB higher than

residual• RF survey must be done for all carriers and

all technologies• Residual signal varies with the height

• Higher floors have higher residual signal• The signal increases 1-3 dB per floor [1] [2] • The signal eventually levels off at floors

above BTS height • RF survey should be done at all floors

• If floor plans are similar, RF survey data may be interpolated between similar floors

•First floor

Sixth floor

Tenth floor


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3 D modeling• IBS signal propagates between floors• It also propagates between buildings• The buildings must be properly modeled,

especially the windows• Some older windows have low penetration

loss• Some newer ones have high penetration loss• The difference can be significant• If you aren’t sure which window type to use

in 3D modeling, make window penetration loss a part of CW propagation test measurements


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IBS signal containment• IBS signal should be confined indoors

• If it is not, IBS signal from one building may overlap with IBS in the other building

• This slows down the network• Most operators stipulate IBS signal level

outside a building• Example

• LTE RSRP -100 dBm at 30 meters away;• UMTS CPICH - 90 dBm at 30 meters away


IBS signal containment• Omnidirectional antennas should not be

placed near windows• Exception may be made if the windows

have high penetration loss due to metallic window tint


IBS signal containment• Directional antennas with low side lobes

and high front to back ratio should be used • Example: Andrew Cellmax D-25

• F/B ratio 20 dB• Antenna gain 4.85 dBd• H plane 3dB beamwidth = 70 degrees• V plane 3 dB beamwidth = 60 degrees


Elevator coverage• Due to metal doors and walls, elevator has

no coverage when elevator doors are closed• The figure shows cross section of the taller

building • Two elevator shafts• Small waiting area at elevator bank• The directional antennas (red triangles)• Color coded in-building sectors

• How to provide coverage?• Antennas at the bank• Wired antenna inside the elevator• Antennas inside the shaft• Radiating cable inside the shaft


Antennas at elevator bank• Omni antennas at the bank in front of the elevators• If we connect omnis to the corresponding IBS

sectors… (see picture)• A UE inside elevator needs to make handover

between IBS sectors• Need up to 10 seconds for a successful HO• If elevator goes straight from top to the bottom floor,

there may not be enough time to execute 2 consecutive handovers

• We may get dropped calls!• If we connect omnis to the same IBS sector…

• All antennas are connected to the top (blue) sector• There is horizontal handoff area near elevator bank

on the lower (yellow) and mid (green) floors• We may get extensive sector overlap!


Wired antenna inside elevator• Antenna is inside elevator, connected to an

IBS sector via cable• Handoff occurs only when entering and exiting

the elevator • No missed handoffs

• Horizontal sector overlap exists only when the door is open (several seconds)

• Rarely deployed in N. America• Most municipalities consider cable inside

elevator shaft a fire hazard


Antennas inside elevator shaft• Three antennas are in use

• IBS directional antenna mounted at the top, pointing down the shaft

• Directional donor antenna at the top of the elevator, pointing up

• Serving Omni antenna inside the elevator, connected to the donor

• Example:• 20 dBm CPICH ERP at the IBS antenna, -85 dBm

RSCP in elevator• Maximum distance =115 m (AWS band)

• If the building is taller, another IBS directional antenna is mounted at the bottom, pointing up

• Must allow for 10-20% overlap margin• Maximum distance = 200 m


Radiating cable inside the shaft• Provides uniform coverage in the shaft• Still may be considered fire hazard


Handoff management• IBS - macro network handoff should be

confined to entrances:• building lobby • loading dock

• Handoff between IBS sectors can be • Vertical• Horizontal

• Vertical handoff is between floors• This handoff should be confined to stairwells• Avoid vertical HO in moving elevators

• Horizontal handoff is on the same floor• These handoffs are not desirable• Might need them for elevator coverage


The key requirement• Employees use their own phones

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

impractical

Optimum solution: Distributed Antenna System

Video streamAnalog / Digital

Power Amplifier

Splitters, dividers,

coax cables

RF / Combining

Analog / Digital

Digital / Analog

Power Amplifier

RF Source

Passive

Active

Splitters, dividers,

coax cables

antenna

antennaRF /

CombiningRF

Source

Analog / Digital

Digital / Analog

Power Amplifier

antenna

antennaRF

Source

RF / Combining


LTE RSRP


UMTS Ec/Io


LTE SINR


LTE Maximum Achievable Data Rate


Enterprise HQ descriptionDesign requirementsBest practices

RF Survey3D modelingSignal containmentElevator coverageHandoff management

IBS Solution2D and 3D coverage maps

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Contact Vladan Jevremovic, Research Director at [email protected]

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