LTE Link Budget

LTE FDD Radio Link Budget Principle

LTE FDD Radio Link Budget Principle

Huawei Technologies Co., Ltd. All rights reserved

2011-9-2

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LTE FDD Radio Link Budget Principle

1 Introduction The purpose of this document is to illustrate the link budget principle and at the same time provide detailed introduction to certain fundamental link budget parameters.

2 LTE Link Budget The link budget calculations estimate the maximum allowed path loss between the mobile and the base station. The maximum path loss allows the maximum cell range to be estimated with a suitable propagation model, such as Okumura–Hata. The cell range gives the number of base station sites required to cover the target geographical area. The LTE Link Budget workflow is showed in figure 2.1. Start

Input Data

Calculate EIRP and Minimum Receiver Sensitivity

Calculate downlink MAPL

Calculate uplink MAPL

And Cell radius

And Cell radius

Min (uplink, downlink)

Effective cell radius

Calculate site number

End

Figure 2.1 LTE Link Budget Workflow

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LTE FDD Radio Link Budget Principle

2.1

Maximum Allowable Path Loss

Link Budget is the first step for radio network dimensioning. For an actual radio access network, the effective coverage of eNode B depends on not only the coverage environment but also the TX power and Rx sensitivity of eNode B and UE. Since the properties of eNode B and UE are different from each other considerably, the actual permitted uplink and downlink path loss vary too. Because the actual effective coverage range will depend on the lower value of them, it is necessary to calculate the permitted maximum allowable propagation path loss of both uplink and downlink. Some MAPL uplink budget parameters are briefly illustrated in Figure 2.1.1 UPLINK BUDGET Other Gain

Slow fading margin Antenna Gain Other Gain

UE Antenna Gain

Interference margin Margin Loss

Body Loss

UE Transmit Power (e.g. 23dBm)

AntennaGain

Penetration Loss

Pa th

Lo ss

Path Loss

Cable Loss Node B Antenna Gain

CableLoss NodeB Sensitivity

eNodeB reception sensitivity

Penetration Loss

(e.g. -119dBm)

Figure 2.2.1 Uplink Budget

The Maximum Path loss (MAPL) of downlink and uplink can be described by the formulas below: MAPL  EIRP(dBm) - 10  Log10 (12  N RB ) - Rx Sensitivit y Composite (dBm)  AntGain(dB i)  CableLoss (dB)  BodyLoss (dB)  IM (dB) - PeneLoss(d B) - SFM(dB)  HHOGain(dB )

Where: 2011-9-2

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LTE FDD Radio Link Budget Principle

MAPL : Maximum path loss (dB) EIRP : Effective Isotropic Radiated Power (dBm)

PeneLoss : Penetration Loss (dB) (required for indoor coverage) SFM : Slow fading margin (dB) HHOGain: Hard Handover Gain (dB)

N RB : Numbers of Required Resource Block

2.2 Main LTE Link Budget Parameters In the following sections, a detailed description of the main parameters used in link budget is provided.

2.2.1 EIRP per Subcarrier EIRP means the Effective Isotropic Radiated power at antenna, calculated including cable loss, antenna gain, body loss etc. and effect by TMA used or not. The formula is as below:

EIRP(dBm) TXMaxpower  AntGain CellEdgeBoost- Bodyloss- CableLoss The modulation scheme of LTE is OFDM (Orthogonal Frequency Division).OFDM is a modulation multiplexing technology divides the system bandwidth into orthogonal subcarriers. The EIRP per Subcarrier means averaged EIRP per subcarrier and have little difference for uplink and downlink. For downlink EIRP per Subcarrier is Max TX power averaged in total bandwidth. This is depending on the number of subcarriers at total bandwidth.

EIRPPersubcarr ier  EIRP - 10  Log10 (12  TotRBNum) For uplink EIRP per Subcarrier means Max TX power averaged in numbers of subcarrier used,

EIRPPersubcarrier  EIRP - 10  Log10 (12  ULRBNum)

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LTE FDD Radio Link Budget Principle



Cable Loss

The cable loss value depends on the cable length, cable thickness and frequency band. The cable Loss for downlink at eNode B side is also related with TMA used or not. For Marco cell with TMA in use

CableLoss( DL)  CableLength  Loss100/10 0  JumperLoss AnttoTMA  JumperLoss TMAtoBS  InsertLoss TMA ;

For Marco cell without TMA in use;

CableLoss(DL)  CableLength  Loss100/100  JumperLoss; Table 2.2.1：Typical cable Loss (100m) Insertion loss/100m Size

800MHz

2100MHz

2500MHz

1/2"

6.456

10.961

12.09

1/2"

10.431

18.137

20.11

7/8"

3.325

5.678

6.27

7/8"

3.676

6.246

6.89

5/4"

2.465

4.342

4.828

13/8"

2.193

3.798

4.208

2.2.2 Receiver sensitivity Per Subcarrier Rreceiver sensitivity is defined as the minimum signal strength that can demodulator by the receiver. The general formula is:

Re ceiverSensitivity  ThermalNoise  E S / N 0  N f The Receiver sensitivity subcarrier is:

Receiver sensitivity Composted  Thermalnoise (dBm/Hz) 10 * lg(Subcarrier band)  NF  Es/No

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LTE FDD Radio Link Budget Principle

2.2.3 Es/No（SINR） Es/No is the Signal to Interference and Noise Ratio as experienced by the detector. The factors Impact Es/No including: 1. Radio Environment (e.g. ETU3) 2. Frequency Band (e.g. 2600MHz) 3. MCS, MCS= Code bits *Code rate. 4. RB (Resource Block) number 5. BLER (e.g. 10%)

2.2.4 Body Loss Body loss is the loss at UE due to the presence of human body. Typical value is 3dB for voip. For services of data rates, no body loss is taken into account considering that terminals are usually held kept a distance from the subscribers’ body.

2.2.5 Penetration Loss When indoor coverage is required to coverage by outdoor macro NodeBs, buliding penetration loss needs to be considered. Building penetration loss is related to such factors as incidence angle of the radio wave, the building construction (the construction materials and number and size of windows), the internal building layout and Frequency. Building penetration loss is highly dependent on specific environment and morphology and varies greatly. For instance, the wall thickness in Siberian tends to be larger than that of Singapore in order to resist coldness and hence the former’s building penetration loss is correspondingly larger. In addition, sometimes vehicular coverage may be required and consequently vehiculare penetration loss also needs to be included in link budget process. In fact, only one penetration loss, the maximum of building penetration loss and vehicular penetration loss, is included in link budget. Since typical vehicular penetration loss is 2011-9-2

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LTE FDD Radio Link Budget Principle

around 8dB which is smaller than building penetration loss, building penetration loss rather than vehicular penetration loss is usually included in link budget process.

2.2.6 Interference Margin (IM) Interference margin is the required margin in the link budget due to the noise rise caused by system load (the noise rise due to other subscribers).The higher the system load, the larger the interference margin.

2.2.7 SFM (Slow Fading Margin) The log normal fading margin (also known as slow or shadow fading margin) corresponds to the variation in mean signal level caused by shadowing effect of physical environments such as buildings and hills. The fading margin is the amount of margin necessary to achieve the required area reliability for a given standard deviation. Obviously, the higher area coverage reliability requires the larger SFM. In addition, the value of standard deviation will also influence the required fading margin and the larger the standard deviation, the larger the required SFM.

Coverage Probability: P COVERAGE (x) = P [F(x) > Fthreshold ]

Probability Density

SFM required

Without SFM With SFM

F threshold

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Received Signal Level [dBm]

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LTE FDD Radio Link Budget Principle

2.2.8 Propagation Model The propagation models are the basis of coverage planning. Good models ensure the precision of planning. The propagation models are used to forecast the influences of terrains and artificial environments on path loss and affected by the system working frequency. Different models have different working frequency ranges. All available Propagation Models can be used for LTE link budget are listed in the following table Model

Applicable Range Band:2.5/3.5/5.8GHz, Antenna height 10~80m

Stanford A/B/C Model

Cell radius