Radio Link Budget - Downlink

CableLoss

AntennaGain

NodeBSensitivity

PenetrationLoss

NodeB Transmit Power

UE Antenna Gain

NodeB Antenna Gain

SHO Gain againstfast fading

SHO Gain againstSlow fading

MDC GainSlow fading margin

Fast fading margin

Interference margin

Body Loss

Cable Loss

Penetration Loss

Maximumallowable path

loss

DOWNLINK BUDGET

UE reception sensitivity

Antenna Gain

SHO Gain

Margin

Loss

Slow fading margin

Algorithm Introduction• PL_UL=Pout_UE + Ga_BS + Ga_UE – Lf_BS + Ga_SHO –

Mpc– Mf – MI – M_BN – Lp – Lb – S_BS

• PL_UL: Maximum propagation loss of the Uplink• Pout_UE: Maximum transmit power of the traffic channel of the UE• Lf_BS: Cable loss• Ga_BS: Antenna gain of the BS; Ga_UE: Antenna gain of the MS• Ga_SHO: Gain of soft handover• Mpc: Margin for fast power control• Mf: Slow fading margin (related to the propagation environment)• MI: Interference margin (related to the designed system capacity)• M_BN: Margin for Background Noise (related to the electromagnetic

environment)• Lp: Penetration loss of a building (used if indoor coverage is required)• Lb: Body loss• S_BS: Sensitivity of BS receiver (related to factors such as service and multi-

path condition)

Uplink (reverse)Uplink (reverse)

Elements of WCDMA Uplink Budget

1. Max Power of TCH2. Body Loss3. Gain of UE Tx Antenna4. EIRP5. Gain of BS Rx Antenna6. Cable Loss7. Noise Figure (BS)8. Required Eb/No (BS)9. Sensitivity of BS Receiver 10.UL Cell Load11.Interference Margin

12.Background Noise Level13.Margin for Background

Noise14.Fast Fading Margin15.SHO Gain over Fast Fading16.Minimum Signal Strength

Required17.Penetration Loss18.Std. dev. of Slow Fading19.Edge coverage Probability20.Slow Fading Margin21.SHO Gain over Slow Fading


• 1. Max Power of TCH (dBm) – For a UE, the maximum power of each traffic channel is usually

the nominal total transmit power. There are many types of UE in a commercial network, so this parameters should be reasonably set in the link budget according to the specifications of a mainstream commercial cell phone and the requirement of the operator

Grade of UE power （ TS 25.101 v3.7.0 （ 2001-06 ） 6.2.1

Power Class Nominal maximum output power

Tolerance

1 +33dBm +1/-3dB

2 +27dBm +1/-3dB

3 +24dBm +1/-3dB

4 +21dBm +2/-2dB

Elements of WCDMA Uplink Budget • 2. Body Loss (dB)

– For voice service, the body loss is 3 dB. – Because the data service mainly involves reading and

video, the UE is relatively not so close to the body, so the body loss is 0 dB

• 3. Gain of UE Tx Antenna (dBi)– Generally, assume that the receiver and transmitter gain

of the UE antenna are both 0 dBi

• 4. EIRP (dBm)– UE EIRP (dBm)

= UE Tx Power (dBm) - Body Loss (dB) + Gain of UE Tx Antenna (dBi)


• 5. Gain of BS Rx Antenna (dBi)

Kathrein 741794

Frequency range1710~2170MHz (dual band for

DCS and UMTS)

Polarization +45O, -45O

Gain 18.5dBiHPBW

(1920~2170MHz)Horizontal: 63O

Vertical:6.5O

Electrical tilt Fixed, 2O

Kathrein 741790

Frequency range 1920~2170MHz

Polarization Vertical

Gain 11dBiHPBW Vertical: 7O

Electrical tilt Fixed, 0O


• 6. Cable Loss (dB)– Including the loss of the feeders and all of

the connectors. • Lower jumper• Connector (between jumper, feeder, cabinet, and

lightning arrester)• Feeder• Upper jumper

– Loss of the feeder:• 7/8-inch feeder: 6.1 dB / 100m for 2GHz• 5/4-inch feeder: 4.5 dB / 100m for 2GHz

– Other connecter loss is assumed 0.8 dB.


• 7. Noise Figure (dB)– Noise figure (NF): It is used to measure the noise

performance of an amplifier. It refers to the ratio of the input SNR to the output SNR of the antenna

NF = SNRi / SNRo

= (Si / Ni) / (So / No)

– Thermal noise of receiver (per Hertz):

• PN = K×T×BW×NF

= -174 (dBm/Hz) + 10lg(3.84MHz / 1Hz) + NF(dB)

= -108 (dBm/3.84MHz) + NF (dB)

Elements of WCDMA Uplink Budget • 8. Eb/No Required (dB)

– It is obtained through link simulation. It is related to the following:

• Configuration of receiver diversity • Multi-path environment• Bearer type (service)

• 9. Sensitivity of BS Receiver (dBm)– Sensitivity of Receiver (dBm)

= PN(dB) + required Eb/No (dB) - 10lg[3.84Mcps/Rb(kbps)]

= -174 (dBm/Hz) + NF (dB) + 10lg[1000 * Rb (kbps)] + Eb/No (dB)


• 10. Uplink Cell Load

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11– Uplink cell load is used to measure the uplink load of

a cell– The higher the uplink cell load, the higher the uplink

interference– If the uplink load is about 100% , the uplink

interference becomes infinite, and the corresponding capacity is the maximum capacity


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50% Load — 3dB

60% Load — 4dB

75% Load — 6dB

• 11. Uplink Interference Margin (dB)


• 12. Background Noise Level (dBm)– External electromagnetic interference sources:

• Wireless transmitters (GSM, microwave, radar, television station, and so)

• Automobile ignition • Lightning • …

– For the planning for a specific area, it is recommended to estimate the local interference through noise test


• 13. Margin for Background Noise Level (dB)– Suppose the thermal noise of the receiver is X

dBm, the background interference level is Y dBm, then received signal should be larger than before to overcome the noise, so the margin for the background noise should be:

Margin for Background Noise =

10log (10X/10 + 10Y/10) dBm - X dBm


• 14. Fast Fading Margin (dB)– In the link budget, the demodulation performance of the used

receiver is the simulation result based on the assumed ideal power control. In an actual system, because of the limited transmit power of the transmitter, non-ideal factors are introduced in the closed loop power control

– Effect of power control margin on the uplink demodulation performance:

• The simulation shows the following: When the HeadRoom is large, the target Eb/No set in the outer loop power control is appropriate to the simulation result under the ideal power control. As the power margin decreases, the Eb/No gradually increases (if the power margin decreases by 1 dB, the required Eb/No increases by about 1 dB). If power control performance is almost not available, the BER/BLER cannot be ensured


• 15. SHO Gain over Fast Fading (dB)– The soft handover gain includes two parts:

• Multiple unrelated soft handover branches lower the required margin for fading, which results in multi-cell gain

• Gain for the link demodulation of the soft handover –macro diversity combining gain

– The SHO Gain over Fast Fading refer to the Macro Diversity Combination gain and reducing the request for fast fading margin

– This value is obtained through simulation. The typical value is 1.5 dB.


• 16. Minimum Signal Strength Required (dBm)– The required minimum signal level should be:

Sensitivity of the Receiver + all the loss and margins – all the gain

– Minimum Signal Strength Required= Sensitivity of Receiver (dBm) + Body Loss (dB)+ Interference Margin (dB) + Margin for Background Noise (dB)+ Fast Fading Margin (dB)- Gain of Antenna (dBi) - SHO Gain over fast fading (dB)


• 17. Penetration Loss (dB)– Indoor penetration loss refers to the signal level difference

between the average strength near the wall outside the building and that of inside the building

– The penetration loss is related to building type, arrive angle of the radio wave, and so on. In link budget, assume that the penetration loss is subject to the lognormal distribution.

– It is uneconomical to provide good indoor coverage through an outdoor BS. Inside the building it should be covered using special indoor coverage solution

– In the actual construction of a commercial network, the penetration loss margin is usually specified by the operator in order to compare the planning results of different tenders


• 18. Std. dev. of Slow Fading (dB) – Std. dev. of indoor path loss– Suppose the standard deviation of the path loss

outdoor is X dB, that of the Penetration Loss is Y dB, the standard deviation of path loss indoor can be get by sqrt( X2 + Y2 )

Elements of WCDMA Uplink Budget• 19. Edge coverage Probability

– If the transmit power of a UE hits the maximum threshold, but still cannot overcome the path loss to guaranty the lowest receive level, the radio link will drop or the UE will fail to access

– If the designed signal level at the edge of the cell equals to the Minimum Signal Strength Required, the actual measurement result will obey the normal distribution.

• This means there is a 50% probability that the UE cannot access the network.

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Elements of WCDMA Uplink Budget• 20. Slow Fading Margin (dB)

Slow Fading Margin (dB) =

NORMSINV (required edge coverage Probability) × Std. dev. of Slow Fading (dB)

Edge Reliability:50%

Edge Reliability:75%

Key point: Property of normal distribution


• 21. SHO Gain over Slow Fading (dB)– The soft handover gain includes two parts:

• Multiple irrelevant soft handover branches lower the required margin for fading, which results in multi-cell gain

• Gain for the link demodulation of the soft handover –macro diversity combination gain

– The SHO Gain over Fast Fading refers to the macro diversity combining gain

– Obtained through simulation

Elements of WCDMA Uplink Budget• Summary: path loss at the edge of a cell

– Based on the maximum path loss allowed by the link, the path loss at the edge can be calculated if the fading margin and soft handover gain for providing the required edge/area coverage probability and the penetration loss of indoor coverage are considered.

– Path Loss (dB) = EiRP (dBm) + SHO Gain over Slow Fading (dB)- Minimum Signal Strength Required (dBm)- Penetration Loss (dB)- Slow Fading Margin (dB)

Summary of the Uplink budget

UE Power – Body Loss＋ Ga_UE_Antenna

Sensitivity of Receiver - SHO Gain over fast fading

- Gain of Antenna + Fast Fading Margin + Body Loss +

Interference Margin

+ Margin for Background Noise

f(edge coverage Probability) * Std. dev. of Slow Fading

EIRP + SHO Gain over Slow Fading - Slow Fading Margin - Minimum Signal Required

Sensitivity of Receiver = PN + required Eb/No – Processing Gain

PN = 10lg ( K*T*B*Nf ) = -108 (dBm/3.84MHz) + NF (dB) ; NF is the receiver NF of

the receiver system at the antenna connecter

Processing Gain = 10lg[3.84Mcps/Rb(Kbps)]

So the Sensitivity of Receiver =

-174 (dBm/Hz) + NF (dB) + 10lg[Rb (bps)] + Eb/No (dB)

Margin for Background Noise

= 10log (10X /10 ＋ 10Y/10) dBm － X dBm

standard deviation of path loss outdoor : X dB,

standard deviation of Penetration Loss: Y dB,

Std. dev. of Slow Fading = Sqrt(X2 + Y2)

Path Loss

- Penetration Loss

Contents

1. Process of WCDMA Network Planning

2. Uplink Budget

3. Downlink Budget

4. Coverage Enhancement Technologies

Fundamental Principle

TX

CombinerDuplexer

Feeder

RX

Pout_BS

Lc_BSLf_BS

Ga_BSNodeB

TX

RX

Pout_UE

Ga_UEUE

CombinerDuplexer

PL_DLPL_U

L

Body Loss

FadingMargin

PenetrationLoss

Algorithm • PL_DL=Pout_BS – Lf_BS + Ga_BS + Ga_UE +

Ga_SHO –Mpc– Mf – MI – Lp – Lb – S_UE

• PL_DL: Maximum propagation loss of the downlink

• Pout_UE: Maximum transmit power of the traffic channel of the BS

• Lf_BS: Cable loss

• Ga_BS: Antenna gain of the BS; Ga_UE: Antenna gain of the UE

• Ga_SHO: Gain of soft handover

• Mpc: Margin for fast power control

• Mf: Slow fading margin (related to the propagation environment)

• MI: Interference margin (related to the designed system load)

• Lp: Penetration loss of a building (for indoor coverage only)

• Lb: Body loss

• S_UE: Sensitivity of UE receiver (related to factors such as service and multi-path condition)

Downlink (forward)Downlink (forward)

Elements of WCDMA Downlink Budget • Max Power of TCH

• Cable Loss• Gain of BS Tx Antenna• EIRP• Gain of UE Rx Antenna• Body Loss• Noise Figure (UE)• Required Eb/No (UE)• Sensitivity of UE Receiver • DL Cell Load• Interference Margin

• Background Noise Level

• SHO Gain over Fast Fading

• Fast Fading Margin

• Minimum Signal Strength Required

• Penetration Loss

• Std. dev. of Slow Fading

• Edge coverage Probability

• Slow Fading Margin

• SHO Gain over Slow Fading

Elements of WCDMA Downlink Budget• Downlink Cell Load

Downlink cell load factor is defined in two ways: – 1. Downlink cell load factor at the receiver:

– This definition is similar to that of the uplink cell load:• The higher the downlink cell load, the higher the cell transmit power,

and the higher the receiver interference.

• When the downlink cell load is 100% , the corresponding capacity is the limit capacity of the downlink.

– 2. Downlink cell load at the receiver: The ratio of the current cell transmit power to the maximum BS transmit power. Characteristics:

• The higher the downlink cell load, the higher the cell transmit power. The downlink cell load is related to service type, UE receiver performance, cell size, and BS capability.

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radio link budget - w

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