GWEC Link Budget Presentation - Final

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link budget

Transcript of GWEC Link Budget Presentation - Final

  • Link Budgets for Cellular NetworksPresented by Eric Johnson

  • IntroductionOverviewLink Budget ImportancePath BalanceFinding ERPParametersScenarios

  • Importance of a Link BudgetWhat is a Link Budget?Determines tower transmit ERP for sufficient signal strength at the cell boundary for a quality mobile callDefines the cell coverage radius when used with a path loss modelWhy need a Link Budget?Determine transmit ERP and cell radiusEnsure path balanceBalance the uplink and downlink powerDont transmit more base station power than the maximum cell phone power capability

  • Importance of a Link BudgetPath Balance IssueMobile is power limitedStronger base station power will deceive mobile into thinking there is sufficient signal strengthMobile can receive info but cannot send

  • Importance of a Link BudgetConsequencesMobile call initiations will fail and poor handoff decisions will be madeAt the cell boundarySolutionSetting the base station power to match the mobile power allows for optimum performancePath balance

  • Path BalanceBalanced PathDistancefrom mobilefromtowerPowerSamePath Loss

  • Path BalanceNot path balancedPrevious Distance

  • Path BalancePath balance limited by mobile powerIS-136Older phones max. power: 3 W (35 dBm)Current phones max. power: 0.6 W (28 dBm)Ranges from 26 to 28 dBmBenefit: less power consumption less rechargingDrawback: smaller cell coverage more cellsGSMMobile power max.: 1.0 W (30 dBm)

  • Finding ERPLink budget determines transmit ERPNetwork is limited by mobile powerTypical transmit is 100 W ERP Transmit ERP determines cell radiusRadius also depends on tower height and path loss environmentSmall improvement (1 dB) in link budget can provide large coverage gains

  • Finding ERPDistancefrom mobilefromtowerPower

  • ParametersSummary of ParametersThermal Noise PowerAntenna GainSignal to Noise (S/N)Minimum Input PowerSimplified Example



    Thermal Noise-129.0 dBmAThermal Noise-121.0 dBmA

    Antenna Gain12.0 dBiBAntenna Gain12.0 dBiB

    Cable Loss1.2 dBCCable Loss1.2 dBC

    S/N15.0 dBDS/N12.0 dBD

    Minimum Input Power-124.8 dBmE = A - B + C + DMinimum Input Power-119.8 dBmE = A - B + C + D



  • ParametersNoise-Limited SystemAmbient temperature creates noise floorInterference from high frequency re-use may cause system to be interference limitedSite measurements determine if noise or interference limitedThe following analysis assumes a noise limited system

  • ParametersThermal Noise PowerPN = kTBk = boltzmans constantT = ambient temperature in KelvinB = signal bandwidthIS-136 PN = -129 dBm GSM PN = -121 dBm

  • ParametersThermal Noise Power (cont.)The noise floor for GSM is 8 dB higher than IS-136 because it uses a wider bandwidth signalResult: IS-136 is 8 dB more sensitive to lower power signals

  • ParametersAntenna GainTower gain ranges from 6 dBd to 16 dBdMobile gain typically 0 dBd (-2 dBd to 0 dBd)gain more uplink larger coverage areagain narrower beamwidthGain choice depends on desired coverage areaMore GainNarrower BeamLess GainBroader BeamIsotropicGain

  • ParametersCable Loss1-5/8 diameter0.8 dB/100-ft7/8 diameter1.2 dB/100-ftTower heights range from 30 ft to 600 ft

  • ParametersSignal to Noise (S/N)IS-136 15 dB (15 - 17 dB)GSM 11 dB (7 - 12 dB)GSM has a S/N advantage over IS-136GSM has more tolerance for errors than IS-136Wider bandwidth and different modulation schemeDifference between GSM and IS-136GSM noise floor is worse (higher) than IS-136GSM S/N is better (lower) than IS-136GSM has more uplink power availableResult: GSM and IS-136 have comparable link budgets, so only analyze IS-136 link budget

  • Scenario 1: BaselineSite ConfigurationHeight: 200 ftAntenna Gain: 12 dBdCable: 1-5/8 0.8 dB/100-ftDetermine ERPPath balance to find ERP

  • Scenario 1: BaselineMin. input power

    Path Loss

    Receive Path Parameters

    IS-136IS-136 w TMAGSMGSM w TMA



    Channel BW (kHz)30.0 kHz30.0 kHz30.0 kHz30.0 kHz200.0 kHz200.0 kHz200.0 kHz200.0 kHz

    Ambient Temperature (deg F)70 deg F70 deg F70 deg F70 deg F70 deg F70 deg F70 deg F70 deg F

    Ambient Temperature (deg C)21 deg C21 deg C21 deg C21 deg C21 deg C21 deg C21 deg C21 deg C

    Thermal Noise (Kelvin)294.1 K294.1 K294.1 K294.1 K294.1 K294.1 K294.1 K294.1 K

    Noise Floor (dBm)-129.1 dBm-129.1 dBmA-129.1 dBm-129.1 dBm-120.9 dBm-120.9 dBm-120.9 dBm-120.9 dBm

    RBS Gain (dB)24.0 dB24.0 dB24.0 dB24.0 dB

    RBS Noise Figure (dB)4.0 dB9.0 dBB4.0 dB9.0 dB4.0 dB9.0 dB4.0 dB9.0 dB

    Noise Floor (dBm)-125.1 dBm-120.1 dBmC = A + B-125.1 dBm-120.1 dBm-116.9 dBm-111.9 dBm-116.9 dBm-111.9 dBm

    Cable Length (ft)220.0 ft220.0 ft220.0 ft220.0 ft

    Cable Loss per 100 ft (dB/100-ft)0.8 dB0.8 dB0.8 dB0.8 dB

    Receiver Cable Loss (dB)1.7 dBD1.7 dB1.7 dB1.7 dB

    Effective Noise Floor no TMA-123.5 dBm-123.5 dBm-115.2 dBm-115.2 dBm

    TMA Gain12.0 dB12.0 dB

    TMA Noise Figure1.0 dB1.0 dB

    System Noise Figure with TMA0.0 dB0.0 dB0.0 dB5.0 dB0.0 dB0.0 dB0.0 dB0.0 dB0.0 dB5.0 dB

    Effective Gain of using TMA0.0 dB0.0 dB0.0 dB0.6 dB0.0 dB0.0 dB0.0 dB0.0 dB0.0 dB0.6 dB

    Effective Noise Floor (dBm)-123.5 dBm-120.1 dBmE = C + D-124.1 dBm-115.2 dBm-115.9 dBm

    C/N (3% BER) (dB)15.0 dB15.0 dBF15.0 dB15.0 dB11.0 dB11.0 dB11.0 dB11.0 dB

    Min. Radio Input (dBm)-108.5 dBm-105.1 dBmG = E + F-109.1 dBm-105.1 dBm-104.2 dBm-100.9 dBm-104.9 dBm-100.9 dBm

    Body Loss (dB)3.0 dBH3.0 dB3.0 dB3.0 dB

    Vehicle Loss (dB)5.0 dBI5.0 dB5.0 dB5.0 dB

    Other: in building coverage (dB)0.0 dBJ

    Receiver Antenna Gain (dBd)12.0 dBd0.0 dBdK12.0 dBd0.0 dBd12.0 dBd0.0 dBd12.0 dBd0.0 dBd

    Receiver Diversity Gain (dB)5.0 dBL5.0 dB5.0 dB5.0 dB

    Effective Min. Input (dBm)-125.5 dBm-97.1 dBmM = G + H + I + J - K - L-126.1 dBm-97.1 dBm-121.2 dBm-92.9 dBm-121.9 dBm-92.9 dBm

    Transmit Path Parameters



    Transmit PA (W)0.6 W16.9 W0.6 W19.6 W1.0 W28.2 W1.0 W32.7 W

    Transmit PA (dBm)27.8 dBm42.3 dBmA27.8 dBm42.9 dBm30.0 dBm44.5 dBm30.0 dBm45.1 dBm

    Transmit Cable Loss Total (dB)1.7 dBB1.7 dB1.7 dB1.7 dB

    Transmit Combiner Loss (dB)4.5 dBC4.5 dB4.5 dB4.5 dB

    Transmit EIRP (dBm)36.1 dBm36.7 dB38.3 dB39.0 dB

    Transmit Antenna Gain (dBd)0.0 dBd12.0 dBdD0.0 dBd12.0 dBd0.0 dBd12.0 dBd0.0 dBd12.0 dBd

    Transmit ERP (dBm)27.8 dBm48.1 dBmE = A - B - C + D27.8 dBm48.7 dBm30.0 dBm50.3 dBm30.0 dBm51.0 dBm

    Transmit ERP (W)0.6 W64.4 W0.6 W74.7 W1.0 W107.5 W1.0 W124.7 W

    Body Loss (dB)3.0 dBF3.0 dB3.0 dB3.0 dB

    Vehicle Loss (dB)5.0 dBG5.0 dB5.0 dB5.0 dB

    Other: in building coverage (dB)0.0 dBH0.0 dB0.0 dB0.0 dB

    Slow fade margin (dB)5.4 dB5.4 dBI5.4 dB5.4 dB5.4 dB5.4 dB5.4 dB5.4 dB

    Effective Transmit Power (dBm)14.4 dBm42.7 dBmJ = E - F - G - H - I

    Max. Path Loss (dB)139.8 dB139.8 dBTeff - Reff140.5 dB140.5 dB137.8 dB137.8 dB138.5 dB138.5 dB

    Path imbalance (dB)-0.0 dB-0.0 dB0.0 dB-0.0 dB

    Adjusted ERP (dBm)48.1 dBm48.7 dBm50.3 dBm51.0 dBm

    Adjusted Transmitter PA (dBm)42.3 dBm42.9 dBm44.5 dBm45.1 dBm

    Adjusted Transmitter PA (W)16.9 W19.6 W28.2 W32.7 W

    TMA Calculations

    Attenuator Pad-2.7 dB9.3 dB-2.7 dB9.3 dB

    (Note: all the following is linear)

    TMA Gain115.8489319246115.8489319246

    TMA Noise Factor11.258925411811.2589254118

    Cable Gain0.67804731420.67804731420.67804731420.6780473142

    Cable Noise Factor1.47482333331.47482333331.47482333331.4748233333

    Attenuator Gain1.85669257220.11714938151.85669257220.1171493815

    Attenuator Noise Factor0.53859212618.53610994180.53859212618.5361099418

    RBS Gain251.188643151251.188643151251.188643151251.188643151

    RBS Noise Factor2.51188643152.51188643152.51188643152.5118864315

    System Noise Factor (linear)1.9952623153.19109199231.9952623153.1910919923

    System Noise Figure (dB)3.0 dB5.0 dB3.0 dB5.0 dB

    Incr. in IP3 due to TMA (dB)0.0 dB0.0 dB0.0 dB2.0 dB0.0 dB0.0 dB0.0 dB0.0 dB0.0 dB2.0 dB

    Cell Radius - Define Height

    Cell Radius - Uplink Limited

    Note: Only the suburban path loss factor was used in these calculations

    850 MHz

    Okumura-Hata for cell radius

    IS-136IS-136 w TMAGSMGSM w TMA

    Frequency (MHz)850 MHz850 MHz850 MHz850 MHz

    Tower Height (m)61 m61 m61 m61 m

    Tower Height (ft)200 ft200 ft200 ft200 ft

    Mobile Height (ft)5 ft5 ft5 ft5 ft

    Mobile Height (m)2 m2 m2 m2 m

    a (h mobile) (dB)0.0542 dB0.0542 dB0.0542 dB0.0542 dB



    Cell Radius (km)5.06 km5.29 km4.40 km4.60 km

    Cell Radius (mi)3.14 mi3.29 mi2.73 mi2.86 mi


    Dense UrbanUrbanSuburbanRural


    Available channels per group25252525

    Actual channels per sector2.08333333332.08333333332.08333333332.0833333333

    Erl per sq mi502550.5

    Voice paths per sector15151515

    Erlangs Available per sector at 2 % GOS9999

    Area of site31.038080450433.956432329823.453147175725.6583265922

    Area of sector10.346026816811.31881077667.81771572528.5527755307

    Erlangs required per sector517.3013408402282.97026941539.08857862624.2763877654


    1900 MHz

    COST 231 for cell radius

    Scenario 1Scenario 2Scenario 3Scenario 4

    Frequency (MHz)1900 MHz1900 MHz1900 MHz1900 MHz

    Tower Height (m)61 m61 m61 m61 m

    Tower Height (ft)200 ft200 ft200 f