LTE Link Budget

LTE FDD Radio Link Budget Principle

Huawei Technologies Co., Ltd.

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.

Figure 2.1 LTE Link Budget Workflow Start

Calculate EIRP and Input Data

Calculate site number

End

Calculate downlink MAPL And Cell radius Minimum Receiver Sensitivity

Calculate uplink MAPL And Cell radius

Min (uplink, downlink)

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

Figure 2.2.1 Uplink Budget

The Maximum Path loss (MAPL) of downlink and uplink can be described by the formulas below: ) HHOGain(dB SFM(dB) -B) PeneLoss(d -(dB) (dB) BodyLoss (dB) CableLoss i) AntGain(dB (dBm) Composite y Sensitivit Rx -) (12 Log10 10 -EIRP(dBm) MAPL         IM N_RB Where: Pat_{h L} oss CableLoss AntennaGain NodeB Sensitivity Penetration Loss UE Transmit Power (e.g. 23dBm) UE Antenna Gain

Node B Antenna Gain Other Gain Slow fading margin

Interference margin Body Loss Cable Loss Penetration Loss Path Loss UPLINK BUDGET

eNodeB reception sensitivity (e.g. -119dBm)

Antenna Gain Other Gain Margin

MAPL: Maximum path loss (dB)

EIRP : Effective Isotropic Radiated Power (dBm)

PeneLoss

SFM : Slow fading margin (dB) HHOGain: Hard Handover Gain (dB)

RB

N

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:

CableLoss

-Bodyloss

-Boost

Edge

Cell

AntGain

TX

(dBm)

EIRP







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.

TotRBNum)

(12

Log10

10

-EIRP







EIRP

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

 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

; InsertLoss JumperLoss JumperLoss 0 Loss100/10 h CableLengt DL)

CableLoss(    _AnttoTMA _TMAtoBS _TMA

For Marco cell without TMA in use;

; JumperLoss 0 Loss100/10 h CableLengt DL) CableLoss(   

Table 2.2.1：Typical cable Loss (100m)

Size Insertion loss/100m 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:

f S

N

N

E

se

ThermalNoi

itivity

ceiverSens





/



Re

The Receiver sensitivity subcarrier is:

Es/No NF band) ier lg(Subcarr * 10 (dBm/Hz) noise Thermal Composted y sensitivit Receiver    

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

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

(x) = P [F(x) > F

]

F

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

Stanford A/B/C Model

Band:2.5/3.5/5.8GHz, Antenna height 10~80m Cell radius <10km, suburban scenario

Cost231－Hata Model Band: 1500~2000MHz , antenna height 30~200m Cell radius 1~20km

Cost231-WI Model

Band: 800~2000MHz , Antenna height 4~50m Cell radius 0.02~0.5km

Okumura-Hata Model

Band: 150~1000MHz , Antenna height 30~200m Cell radius 1~20km