Link Budget

Link Budget

Company Confidential

Link Budget

Link Budget is the first step toward RF Planning. It is also called Power Budgeting.It provides the Max. Allowable Path Loss (MAPL) and Cell Radius.MAPL is max. attenuation on the signal which can be allowed to Demodulate the signal Correctly.Cell radius is the theoretical value which can be used to find the total no of sites required.

Company Confidential*


Link BudgetLink budget is the accounting of all of the gains and losses from the transmitter, through the medium to the receiver in a telecommunication system.It accounts for the attenuation of the transmitted signal due to propagation, as well as the antenna gains, feeder and miscellaneous lossesChannel Margins such as fading are taken into account by adding some margin depending on the anticipated severity of its effects.A simple link budget equation looks like this:

Received Power (dBm) = Transmitted Power (dBm) + Gains (dB) Losses (dB)

Link budget will be considered in both side:- Uplink Link Budget ( From UE to eNodeB)Downlink Link Budget From eNodeB to UE)



Link Budget PrincipleCompany Confidential* Link budget Process Starts with a target service (Cell Edge Throughput ) in a certain Environment (Dense Urban , Urban, Rural).First we get MAPL ( Max. Allowable Path Loss) MAPL = Tx Power Rx sensitivity Losses Margins + Gains

Using MAPL we will find out Cell RadiusMAPL = Intercept + 10 Slope Log10(Cell Radius) Cell Radius = 10(MAPL Intercept) / (10 Slope )


Downlink Link Budget ( From eNodeB to UE)



Uplink Link Budget ( From UE to eNodeB)Company Confidential*


Tx PowerTransmitted Power in Downlink is 43 dBm i.e. Base Station PowerTransmitted Power in Uplink is 23 dBm i.e. UE Power



GainsIn link budget, gains are considered in the form of antenna gain , MIMO gain , Diversity gain and Handover gainIn Downlink eNodeB Antenna gain is considered 18 dBi for 65 degree HBW.In Uplink UE has 0 dBi gain, a outdoor CPE has 4-5 dBi gain.



MarginsMargins considers random losses due to Fading , Shadowing, Interference due to neighbors cell and user in own cell.



LossesLosses includes cables loss, Connector loss and Penetration loss.Cable loss depends upon the length of cable (dB/m)Penetration losses are depends on the Morphology: Dense urban : 22dB Urban : 18dB Suburban : 16dB Rural : 12dB



Receiver SensitivityRx Sensitivity is defined as the threshold of Min. signal strength which can be successfully decoded by the receiver.Rx sensitivity depends on thermal noise, Noise figure of Receiver, Bandwidth and SINRRx sensitivity = Thermal Noise +Bandwidth +Noise Figure +SINR



Downlink Link Budget (Calculation)

In Downlink BS power is 43 dBm.Antenna Gain is to be supposed 18 dBi.Loss 2 dB and Margin is 4 dBReceiver sensitivity is -110 dB MAPL = Tx Power Rx sensitivity Losses Margins + Gains Path Loss = 43 - 2 - 4 + 18 + 110 = 164 dB



Uplink Link Budget (Calculation)In Uplink UE power is 23 dBm .Antenna Gain is to be supposed 0 dBi .Loss 2 dB and Margin is 4 dBReceiver sensitivity is -110 dB MAPL = Tx Power Rx sensitivity Losses Margins + Gains Path Loss = 23 - 2 - 4 + 0 + 110 = 127 dB





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Link Budget

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