TETRA in Tunnels - Anthony Sutton

TETRA in Tunnels1

Anthony SuttonSales Manager – Aerial Facilities Limitedanthonys@aerial.co.ukwww.aerialfacilities .com2

Tunnel Environments‣ Road Tunnels‣ Metros‣ Rail Tunnels‣ Underground service tunnels(Airports)Slide 3

Design Considerations - Tunnels‣ Length of Tunnel‣ Frequencies required in tunnel‣ Required signal strengths‣ Alarming‣ Redundancy‣ Method of coverage – LeakyFeeder Cable or antennas‣ Equipement Locations‣ External Signal StrengthsSlide 5

How to serve Tunnels - Antennas‣ Efficient for covering wideopen spaces‣ Poor in Tunnels at LowFrequency‣ Can Suffer from Near / Fareffect‣ Tuned to frequency bandSlide 6

How to serve Tunnels - Radiating Cable‣ Imperfectly screen co-axialcable with slots or holeswhich radiate‣ Controlled radiation, majorityof power transmitted alongthe cable‣ Avoids Near / Far Effect‣ Broadband or TunedSlide 7

Coverage in Tunnel - Link Budget Calculations‣ Splitting Losses‣ Cable Longitudinal Losses‣ Coupling Loss‣ EquipmentPower/Sensitivity‣ Receive Signal Level‣ Propagation Loss (where iscoverage required?)Slide 8

Simple Road Tunnel CoverageDownlink Signalstrength at Car =(+20dBm - longitudinalloss) – coupling loss:(+20 – 20dB(1000mtrs) – 75+40dBm-75dBm-75dBm100dB Free Space Loss (>5km @UHF)-60dBm= -75dBm at carantenna0dBm1km = 20dB Loss typLongitudinal Loss dB / km+20dBm+25dBm-35dBm-35dBm-55dBmCoupling Loss @ 95%: Typical 75dBCoupling loss 50% / 95% at distance 2m / 6m(75dB typical)-75dBmGain 80dBTypical RX Sens = -113dBmTypical TX Pwr = +40dBmCar mobile transmit = +35dBmSlide 10

Coverage Options – Large Tunnels & Metros‣Direct Coverage from BTS– Direct connection• Can be dedicated tunnel coverage or alsoused to provide above ground coverage• Can also provide station coverage• Requires back haul link to networkSlide 13

Coverage Options – Large Tunnels & Metros‣Coverage from Cell Enhancer– Cascaded amplifiers• Low costs system• Easy to install• Lacks system redundancySlide 14

Coverage Options – Large Tunnels & Metros‣Coverage from Cell Enhancer– FO Back Bone• Low costs system• Easy to install• Improved system redundancySlide 15

Coverage Options – Large Tunnels & Metros‣Coverage from BTS & Cell Enhancer– Direct Feed – FO Mastersite• Improved performance• Easy to install• Utilise above ground BTS for undergroundcoverageFO MastesiteSlide 16

Coverage Options – Large Tunnels & Metros‣Coverage from Larger system with multiple BTS– Direct Feed – FO MastersiteSlide 17

Special Points for Tetra‣ Time Delay is important if equi-signal overlap areasexist.‣ Two digital signals with differing delays cause symboloverlap. Demodulation uncertainty leads to high Bit ErrorRate.‣ Timing of overlapping signals should not differ by morethan about ¼ symbol period – less if possible.Zero Delay1/8 Symbol Delay1/4 Symbol Delay1/2 Symbol DelaySlide 19

What are Equi-signal overlaps‣Areas where BTS and repeatedsignals are both present.‣Tetra Symbol Rate is 18kbit/s or56uS/symbol‣Differential delay should be 56/4

Special Points for Tetra‣ Propagation time in air is 3.3uS/km. In Fibre or in Cable it is1.5 times greater – practically 5uS/km. To avoid delayproblems in overlap areas differential route distance of thetwo signal components should not exceed 2.8km of fibre +cable.TETRA BS4km1.5kmFibre OpticSlave SiteFibre OpticMaster SiteCoupler -30dBFibre OpticSlave Site500m1km1km500m2km -1km = 1km OK4.5km - 1km = 3.5km NOKSlide 21

Alarm Monitoring‣ Local Alarms for connection Scada system.‣ Remote from location direct to NMC‣ Remote alarm reporting back to MastersiteWESTMAINPLAZACITYEASTSOUTHHALLSlide 22

Key Features‣ Low cost‣ Limited visual impact‣ Seamless transitional coverage‣ High level of service availability‣ Expandable‣ Couple on to existing infrastructure or new build‣ Single or multiple bands / technologies on samesystemSlide 23

Sample of existing Tetra Tunnel Coverage‣ Madrid Metro‣ London Underground‣ Amsterdam Metro‣ Shanghai Metro‣ Blackwall Road Tunnel‣ Brussels Metro‣ Athens Metro‣ Moscow Metro‣ Channel Tunnel Rail Link‣ Bilbao Metro‣ Dubai Airport – includingservice tunnels‣ Barajas Tunnel – Road / Rail/ Service tunnel – MadridAirport‣ Nanjing Metro‣ Rotterdam Metro‣ Heathrow Express‣ Warsaw – Tram TunnelsSlide 24

Any Questions?25