Download - LTE_Lte Link Budget v03

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1 Nokia Siemens Networks RA41205EN20GLA0

LTE RPESSLTE Link Budget

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Nokia Siemens Networks Academy

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Module Objectives

After completing this module, the participant should be able to:

Calculate link budget for different bit rates Understand link budgets and parameters Understand planning margins

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Coverage Dimensioning

Introduction DL Link Budget & Parameters UL Link Budget & Parameters Examples

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Introduction

Link Budget is the basis of coverage dimensioning, aiming to calculate UL / DL maximum allowed path loss (MAPL) for a certain type of service.

With the MAPL and a suitable propagation model, which can be generally seen as a function about path loss (PL) and distance between UE and eNB, average cell coverage radius can be calculated.

With cell coverage radius, radio network planners can easily figure up the site coverage area and site count for given area. Thats the target of coverage dimensioning.

Coverage AreaCA Range

Coverage dimensioning requires multiple inputs:

Service typeTarget service probabilityInitial site configurationEquipment performancePropagation environment

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Link budget

Target of the Link Budget calculation: estimate the maximum allowed path loss on radio path from transmit antenna to receive antenna

The minimum SINR requirement is achieved with the maximum allowed path loss and transmit power both in UL & DL

The maximum allowed Path Loss can be used to calculate cell range

Lmax_DLLmax_UL

Tx Power+ Gains Losses/Margins Path Loss minimum required Rx Power max. Path Loss Lmax

Range

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Introduction DL Link Budget & ParametersUL Link Budget & Parameters Examples

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In LTE, similar like in HSDPA Link Budget, one of two approaches can be adopted:

1. Cell Edge User Throughput LTE bit rate can be specified and link budget completed from top to bottom to determine the maximum allowed path loss

2. Existing maximum allowed path loss can be specified and link budget completed from bottom to top to determine the achievable LTE bit rate at cell edge

LTE DL Link Budget (FDD case)

*PDSCH = Physical Downlink Shared Channel

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LTE DL Link Budget

Assumptions: Operating Band

3GPP TS 36.104 specifies 16 operating bands for FDD

Defined by customer Channel Bandwidth

3GPP TS 36.104 specifies values of 1.4, 3, 5, 10, 15 & 20 MHz

Defined by customer. Channel Model

The SINR is based on link level simulations results which are available for:

Enhanced Pedestrian A 5Hz (EPA05) valid for low speed mobiles in general, i.e. 3 Km/h at 1800 MHZ (5Hz Doppler)

Enhanced Typical Urban (ETU70) valid for higher speed mobiles

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LTE DL Link BudgetOperating Band

For simplicity only the main centre frequencies (e.g. 1700, 2100, 2600 ...) are considered for the link budget calculation

It is also assumed that there is no bandwidth separation between UL & DL (i.e. 2600 MHz assumed both UL & DL )

Channel Bandwidth The bandwidth configuration impacts factors such as Thermal Noise, overhead ratio & total cell throughput.

The wider the working band is, the better the network performance (max. peak rate & cell throughput) is.

Supported operating bands* &

bandwidths in RL 10

& 20

5 MHz, 10MHz, 15 MHz, 20 MHzBand 12100 MHz

5 MHz, 10MHz, 15 MHz, 20 MHzBand 3 & 91800 MHz

5 MHz, 10MHz, 15 MHz, 20 MHzBand 4 & 101700/2100 MHz

5 MHz, 10MHzBand 241600 MHz

Frequency band Band Index Supported Bandwidths 800 MHz Band 20 & 5 & 6 & 18 & 19 5 MHz, 10MHz(, 15 MHz, 20 MHz)

2600 MHZ Band 7 5 MHz, 10MHz, 15 MHz, 20 MHz

LTE uses a channel raster of 100 kHz, which means that the carrier centre frequency must be an integer multiple of 100 kHz. Uplink E-UTRA Absolute radio Frequency Channel Numbers (EARFCN) are allocated sequentially from 0 starting from the lowest frequency in the uplink of operating band 1. Downlink EARFCN are allocated sequentially from 13000 starting from the lowest frequency in the downlink of operating band 1.

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LTE DL Link Budget

Assumptions: Scheduling

Two options possible: round robin & proportional fair

Proportional fair is possible only in DL for RL10 See next slide

Clutter Type Typical: dense urban, urban, suburban,

rural Impact on propagation parameters like

slow fading margin or building penetration loss

Cell Edge Throughput Either defined by the network operator or

derived from the given pathloss Central input parameter

See next slide

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LTE DL Link Budget

Scheduling Round Robin (RR) algorithm in time and frequency random allocation Proportional Fair (PF) in time and frequency domain allocation based on metrics assigned to

UE (e.g. Channel conditions) RL 20 RRM uses Proportional Fairness as the default scheduling algorithm for DL.

Frequency Domain Packet Scheduling (FDPS) provides some SINR improvement for PF.

Cell Edge User Throughput [kbps] Target throughput requirement to be achieved at the cell edge; minimum net single UE

throughput requirement Determines the service that can be provided at the cell border It can limit the MCS (Modulation & Coding Scheme) to be used Normally customer requirement

In LTE the scheduling is done on a per sub-frame basis: 180KHz in frequency domain and 1ms in time domain --- PRB pair.For each time interval the scheduler controls which resources will be allocated to which users (considering the buffer status, pending retransmissions, ...) HARQ retransmissions and Signaling Radio Bearers (SRB) have a higher priority than the first transmission for data radio bearers. The frequency domain scheduler takes into account the channel conditions for every user and makes the best possible assignment. It applies in DL "throughput-to-average" and "proportional-fair-scheduled (LNCEL: dlsFdAlg). In UL "Round robin" and "exhaustive FD scheduler" is used (LNCEL: ulsFdPrbAssignAlg).

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LTE DL Link Budget

Transmitter: eNodeB Tx. Power per Antenna

Typical value: 43dBm (20W) Antenna TX Gain

Antenna gain changes with the antenna type and frequency band

Common value: 18 dBi for a directional antenna Cable Loss

Feederless solution considered MHA Insertion Loss

Mast Head Amplifier MHA: Pre-Amplifier for UL receive path Typical 0.5 dB

EIRP represents the Effective Isotropic Radiated Power from the transmit antenna.

EIRP = Tx. Power per Antenna + Antenna Gain Cable Loss MHA

Insertion Loss

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LTE DL Link Budget

Tx. Power per Antenna Connector Depends on the Flexi Radio Module selected Typically 8, 20, 40 & 60 Watts 8, 40 & 60W are SW licensed In case of transmit diversity techniques like MIMO transmit diversity the power could be increased with 3dB in

DL

Antenna Gain Proportional to the physical size, signal frequency and antenna vertical & horizontal beamwidth Large size & High frequency Narrow beam High gain In 2100 MHz bandwidth typical gains are between 12 dBi - 20 dBi BTS Antennas vary in frequencies, sizes & configuration smaller antenna beam higher Antenna Gain larger size (e.g. 1m 2 m) higher Antenna Gain (at same frequency) lower frequency lower Antenna Gain

Typical values: 18 dBi for eNodeB directional antenna (3-sector) 19.5 dBi for eNodeB directional high gain antenna (6-sector) 8 dBi for eNodeB omni-directional antenna

Flexi multiradio BTS provides high radio downlink output power when using Flexi 3-sector RF module with the total of 210w power amplifiers, or RRH.

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Cable loss

Cable Loss is the sum of all signal losses caused by the antenna line outside the base station cabinet Jumper losses Feeder cable loss MHA (or TMA) insertion loss in DL when MHA is used

Typical 0.5 dB No MHA is used with Feederless solution*

Typical values for the cable loss: 0.4 dB with Feederless solution* (jumper losses only) 2 dB feeder solution w/o TMA 2.4 dB if feeders with TMA used (2 dB feeders + 0.4dB additional

jumpers for TMA) + 0.5dB MHA Insertion loss

* in the case of feederless solution the Flexi RF Module is mounted closed to the antenna. There is only a jumper cable connection between the RF module and the antenna system

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LTE DL Link Budget

Receiver: UE Handset Noise Figure depends on the receiver equipment design and

represents the additive noise generated by various HW components

Typical 7dB for the UE Thermal Noise

Depends on the channel bandwidth See next slide

SINR Requirement See next slides

Receiver Sensitivityrepresents the signal level that is required at the antenna port of the receiver to be able to achieve acceptable quality level in receiving

Receiver SensitivityReceiver Sensitivity = Handset Noise Figure + Thermal Noise + SINR Requirement

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Thermal Noise Calculation

Thermal Noise = kB x T x B

Where: kB = Boltzmanns constant, 1.38 E-23 Ws/K T = Receiver temperature, 293 K B = Bandwidth

10 log (kB *T) = -174dBm/Hz is the Thermal Noise Density not considering the bandwidth impact

DL: OFDM receiver looks at the whole bandwidth, thus all available Resource Blocks should be considered.UL: SC-FDMA receiver looks only at the allocated bandwidth, thus not all but only assigned Resource Blocks are assumed in sensitivity formula.

OFDMA / SC-FDMA

)#1215log(10/174 RBkHzHzdBmseThermalNoi +=

Single RB bandwidth

Receiver bandwidth

#RB is the Number of Physical Resource Blocks DL: all available in the channel bandwidth UL: only those RBs allocated for transmission

Example:For 10MHz there are 50 RBs in DLThermal noise = -174dBm/Hz + 10log(15 * 1000 * 12 * 50) = = -174 dBm/Hz + 69,54 dB== -104.45dBm

Thermal noise density: 10*log (kT) in dBm, where k:1.38e-23 Joules/Kelvin; T:300 Kelvin

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SINR: Signal-to-Interference + Noise Ratio

SINR: Signal to Interference plus Noise Ratio Minimum relation between useful signal and sum of interferences coming from own and

neighboring cells and the received noise power

S : useful signal (received power) Iown : own cell interference (close to zero in LTE due to the orthogonality of subcarriers) Ioth : other cell interference N : noise power

In LTE the PDSCH required SINR replaces the required Eb/No of the UMTS Rel. 99 DCH Link Budget; Eb/No is not helpful in case of Fast Link Adaptation

SINR requirement is practically obtained from link level simulations, which depend on channel mode, MIMO scheme, BLER requirement.

NIISSINRothown ++

=

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SINR distribution

CDF = Cumulative Distribution Function *Source: "LTE Downlink Performance Results with Time-Domain Scheduling - Using UPRISE" by Klaus I Pedersen et al.

The simulation scenarios and parameters are provided in 3GPP TR25.814Bandwidth = 2000MHzSpeed = 3Km/h

Macro Case 1 Inter-site distance = 500m

Macro Case 3 Inter-site distance = 1732m

Cell load is 100% which is affecting the inter-cell interference

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Required SINR

In order to meet the defined quality requirements (BLER) a certain average required SINR is needed Required SINR depends on: Cell Range (Pathloss) Cell Edge User Throughput

Based on the Cell Edge Throughput the number of allocated PRBs and the MCS could be defined see next slides OFDM specific channel models

Channel model is a way to consider UE mobility and environment in the link budget calculation 2 main groups of channel models are available:

Enhanced Pedestrian A 5Hz (EPA05) valid for low speed mobiles in general, i.e. 3 Km/h at 1800 MHz (5Hz Doppler) Enhanced Typical Urban (ETU70) valid for higher speed mobiles

Considered Antenna Scheme for the DL: 1Tx 2Rx; 2TX 2RX Transmit Diversity ; 2TX 2RX Spatial Multiplexing (not expected at cell edge)

L1 overhead of the physical channels The impact is the reduced number of resource blocks which could be used for user data

Scheduling gain see next slides

MCS: Modulation & Coding SchemePRB: Physical Resource Block

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Required SINR decision sequence (1/7)

STEP 1 for the required SINR decision: Input: Cell Edge User Throughput The target cell edge throughput is used to select the

least robust MCS with good balance of coverage & resource consumption of the air interface

BLER at first HARQ retransmission Assumption: to be 10% for the first HARQ

retransmission, i.e. 10% probability to complete 1 or more retransmissions

The actual effect is the increase of the cell edge throughput

MCS = Modulation & Coding Scheme 3GPP TS 36.211 specifies QPSK, 16QAM & 64QAM for the DL Affects the amount of resources that will be used for user data

Output: TBS (Transport Block Size) & Number of Required RBs (Resource Blocks) see next slide

Cell Edge Throughput BLER MCS

STEP 1 for required SINR decision

TBS = Transport Block Size

#RBs = Number of Resource

Blocks

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TBS set Number of user data bits transmitted to single user

during 1 TTI (1ms) The TB occupies 2 PRBs in time domain 3GPP TS 36.213 specifies tables to: link the MCS Index -> Modulation Order (modulation type) and

TBS Index link the TBS Index -> Transport Block Size (TBS) for a specific

number of PRBs

MCS index - from 0 to 28 it is decided by the scheduler which should translate a specific

CQI in an MCS index

ITBS = TBS index The TBS Index is mapped to a specific TBS size for a specific

#PRBs Uses a different table (3GPP TS 36.213) See next slide for an example

DL MCSsMCS_index MCS Mod order ITBS

0 QPSK 2 01 QPSK 2 12 QPSK 2 23 QPSK 2 34 QPSK 2 45 QPSK 2 56 QPSK 2 67 QPSK 2 78 QPSK 2 89 QPSK 2 910 16QAM 4 911 16QAM 4 1012 16QAM 4 1113 16QAM 4 1214 16QAM 4 1315 16QAM 4 1416 16QAM 4 1517 64QAM 6 1518 64QAM 6 1619 64QAM 6 1720 64QAM 6 1821 64QAM 6 1922 64QAM 6 2023 64QAM 6 2124 64QAM 6 2225 64QAM 6 2326 64QAM 6 2427 64QAM 6 2528 64QAM 6 26

MCS: Modulation & Coding SchemePRB: Physical Resource Block

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MCS = 10-16QAM TBS_index = 9

Air Interface User Throughput = = 384 / (100% - 10%) = 427 kbpssearch for TBS in ITBS9 Air Interface User

Throughput

#RB_used = 3 TBS = 456 bits456 bits/TTI = 456 bits/1 ms = 456 kbps 427

kbpsConclusion: # RB used= 3

Example for the identification of the Number of PRBs per User and the Transport Block Size (TBS)

Assumptions: Required cell edge throughput = 384Kbps MCS = 10-16QAM

Only a subset of the complete table(3GPP TS 36.213 specifies 110 columns)

Identifies the number of Resource Blocks (RB) required to achieve the target Cell Edge User ThroughputUses the already defined MCS to identify the appropriate row within the transport block size tableThe target Cell Edge User Throughput is used to determine the minimum transport block size requirement

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STEP 2 for the required SINR decision:

The selected MCS & #PRBs from Step 1 is associated with a defined Required SINR

The actual SINR requirement is obtained from link level simulations

Several look-up tables results are available for several cases: Specific channel models (EPA 5Hz & ETU70Hz

channel models) Different SINR requirements are specified for

different antenna schemes (1TX 2RX or 2TX 2RX)

Block Error Rate BLER typical 10% In the SINR look-up table result the SINR is a

function of : MCS = Modulation and Coding Scheme Number of RBs

Example:SINR table for the case DL 2Tx-2Rx, EPA 5Hz Channel Model, BLER = 10%EPA 5Hz Doppler frequency=5Hz for 1800MHz and 3km/h


Conditions for the table --- EPA5Hz + 22MIMO + 10%BLEREPA: Enhanced Pedestrian A, ETU: Enhanced Typical Urban.

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The selection of MCS is a trade-off between coverage & resource utilization:The more robust the selected MCS (e.g. 0-QPSK) the lower the allowed required SINR which is improving the coverage. But on the same time the higher the resource consumption (42 PRBs out of 50 for 10 MHz bandwidth for 1024Kbps) which leaves less resources for the rest of the scheduled users.

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Note that not all MCS are suitable to achieve a certain cell edge throughput. If high target cell edge throughput are required then the selection of a very robust MCS (with correspondingly large overhead portion) may lead to a situation where the resource consumed by the coded user data traffic exceeds the amount of the resources provided by the entire cell (e.g. MCS = 3-QPSK for a cell edge throughput 4096Kbps requires more than 50 PRBs for 10 MHz bandwidth)It is recommended for a specific cell edge throughput to select the MCS which is maximizing the allowed pathloss.

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DL FDPS Gain (dB)Channel usage per

single UE Gain (dB)

10.00% 3,7111.11% 3,6412.50% 3,5314.29% 3,4116,67% 3,2520.00% 2,9325.00% 2,5233.33% 2,1150.00% 1,68

100.00% 0

STEP 3 for required SINR decision: Consider additional SINR improvements features like FDPS

(Frequency Domain Packet Scheduling) System level simulations are used to show the gain of Proportional Fair

algorithm in DL over Round Robin (see the table) The table could be read as follows: when UE occupies 100% of

resources there is no gain from particular scheduling strategy because RRM cannot play with frequency resources.

The more UEs could be scheduled in the same TTI (that means less resource allocation per user), the more certain gain can be observed.

Example:Cell edge Throughput is 1024Kbps, Number of allocated PRBs per user is selected to be 13 out of 50 available in 10 MHz (for MCS = 5-QPSK)

The channel usage per TTI of the user is 26%. Thus, Required SINR = 1,11 dB(Required SINR from table) 2,47 dB (FDPS gain for 26% channel usage) = -1,36dB


The larger the amount of resources (subcarriers) available for the scheduling of a single user, the higher the chance to avoid channel quality gaps For example when 50 PRBs are available (10MHz bandwidth) and 10 full user buffer UEs are scheduled per TTI then it results 5 PRBs per user that is 10% of resources allocated per UE.

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LTE DL Link Budget

Receiver: UE Rx Antenna Gain

0 dBi for UE Antenna DL Load

Average Resource Utilisation Assumed to be 50% Defined by the customer

Interference Margin Depends on the neighbor cell interference Frequency reuse 1 will be used Higher reuse schemes are possible but

there is no significant gain in network performance

See next slides Body Loss

2-3 dB for VoIP users & 0 dB for data users

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Cell Load

Cell Load [%] Cell load represents the average resource utilization in terms of PRBs

It accounts for the average load of the system over longer time period (minutes, hours,...) For the link budget calculation, which is a single cell-edge user case to estimate maximum possible

coverage, cell load reflects the average neighbour load but it does not impact own cell resource allocation In other words a cell edge user occupying 100% resources per TTI (100% of PRBs) does not mean 100%

load (i.e. over long time period)

Affects the Interference Margin (IM) Higher cell load means higher interference from the neighbour cells High neighbour cell load increases the IM that in terms reduces the MAPL* High neighbour cell load limits the possibility of selecting high MCS

Recommended value: 50% (subject to change) Customer may provide this value

*MAPL = Maximum Allowed Path Loss

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DL Interference Margin

)/(/

NIISNSIMotherown ++

=

S: useful signal (received power) Iown: own cell interference ( 0 in LTE due to the orthogonality of subcarriers) Ioth: other cell interference N: noise power

100% orthogonality could be assumed in UL & DL due to OFDM & SC-FDMA so that the Intra-cell interference is close to zero

The only interference which counts is the Inter-cell interference DL Interference Margin could be derived analytically

Interference margin IM Interference Margin can be defined as a relation between signals received with & without interference

IM = (1/N) / [1 / (I+N)] = 1 / [N / (I+N)] = 1 / [1 I / (N + I)] = 1 / [1 S/(N+I) I/S] = 1 / [1 SINR(1/G)], and now can be introduced on the right part.

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DL Interference Margin

GSINR

IM11

1

=

=

GSINRIM 11log10

Neighbour cellload

G = S/I = Geometryfactor

After some analytical derivation the IM in DL could be written as:

Geometry Factor G explanation: At cell edge the noise N could be neglected in comparison to Iother so that SINR S/I which is

also called G geometry factor SINR < G (G is the Maximum SINR at cell edge) G depends on the network geometry (cell area location probability) and antenna configuration but

not on the cell range G = -0.03 dB

Obtained from system level simulations (with the NSN Morse Simulator for the 3GPP Macro cell case 1 simulation environment with ISD (inter-site distance) = 500m

(typical 50%).

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Interference MarginDownlink (simulation for 10MHz BW)

IM as a function of Neighbour Cell Load for different MCS and cell Edge User Throughputs

By selecting high neighbour cell load we are limiting to the usage of low ( robust) MCS since for higher MCS the IM increases a lot.

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LTE DL Link Budget

Building penetration loss BPL Loss for Indoor Coverage due to walls, etc. clutter specific between 12 dB (Rural) and more than

20 dB (Urban / Dense Urban) (Indoor) Location Probability

Area Location probability, giving the service probability of connection (here: indoor)

applied values depend on clutter & area, vary from 85 95%

Indoor standard deviation The standard deviation represents the dispersion

of the path loss or received power measured over the coverage area.

clutter & area dependent; differing for Indoor / Outdoor; varies from 5 - 12 dB.

Shadowing Margin or Slow Fading Margin often also denominated as Log-normal Fading

Margin calculated from indoor location probability and

standard deviation. Typical values for slow fading margins for 90-95% coverage probability are:

outdoor: 6 8 dB indoor: 10 15 dB

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Building penetration loss

Pref = 0 dB

Pindoor = -3 ...-15 dB

Pindoor = -7 ...-18 dB

-15 ...-25 dB no coverage

rear side :-18 ...-30 dB

signal level increases with floor number :~1,5 dB/floor (for 1st ..10th floor)

Signal levels from outdoor Base stations into buildings are estimated by applying a Building Penetration Loss (BPL) margin

Slow fading standard deviation is higher inside buildings due to shadowing by building structures There are big differences between rooms with window and deep indoor (10 ..15 dB)Typical values for BPL:

In-car/Rural 5 10dB

In building:Dense Urban: 2025 dBUrban: 1520 dBSuburban: 1015 dB

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Slow Fading Margin SFM / Shadowing Margin

Slow Fading is caused by signal shadowing due to obstructions on the radio path

A cell with a range predicted from maximum pathloss(without Slow Fading Margin SFM) will have a Cell Area Coverage Probability of about 75 %

this means: Lot of coverage holes due to shadowing

SFM is required in order to achieve higher coverage quality, better coverage probability

Smaller cell, less coverage holes over cell area, better coverage quality

max. pathlossfrom link budget

Pathlossprediction model

Cell Range

Cell Area Coverage probability = 75 %

large coverage holes, bad coverage quality

max: pathlossfrom link budget

Pathloss prediction model

Cell Range

Cell Area Coverage probability > 75 %,i.e. less coverage holes,Better coverage quality;

but: smaller cells

- Slow Fading Margin SFM

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The Location Probability means the probability that the average received field strength is better than the minimum required received signal strength (in order to make a successful phone call).For Radio Network Planning & Dimensioning, two different types of location probabilities are used: Cell Area Probability: coverage probability over the whole cell area; Cell Edge Probability: point location probability at the cell edge. The Jakes formula can be used to convert the Cell Area into a Cell Edge Probability.

Area Location Probability: Cell Area / Cell Edge Probability

Cell Edge probability [ % ]

Cell Area probability [ % ]

5075849095

7590949799

Jakes, W.C.Jr. Microwave Mobile Communications. USA 1974, John Wiley & Sons. 473 p

Cell Edge Probability

Point Location Probability

Cell Area Probability:Location probability over whole cell area

W.C.Jakes formula is complex.Typical value mapping is shown in the table.

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Cell Edge Probability: Point Location Probability at Cell Edge

Slow Fading is normal distributedwith the gaussian distribution function

+=

=

221

21

2

1

0

2)(

20

2

2

0

m

x

rr

x

rxerf

rdepm

Refer to Cellular Radio Performance Engineering, Chapter 2, e.g. 2.9 Page 29Jakes, W.C.Jr. Microwave Mobile Communications. USA 1974, John Wiley & Sons. 473 p

The probability Pxo that r exceeds some threshold xo at a given point inside the cell is called the Point Location Probability. The point location probability can be written as the upper tail probability of the above equation :

2

2

2)(

22

1)(

=

mrr

erp

Slow Fading Margin, SFM

Field StrengthLevel [dBm]

Prob

abilit

y

m

SFM = 1 - coverage

Coverage w/o SFM

Clutter Type DU 9 dBU 8 dB

SU 8 dBR 7 dB

The standard deviation isempiricallydetermined

Examples:

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FR

p dAu x=

1 2 0Cell Area Location ProbabilityPoint LocationProbabilities

px0

F erf a e erf a bbu

a bb

= + + +

+

1

21 1 1

2 12( )

2)( 00

=

Pxa2

log 10

=

eb

P0: field strength threshold value at cell edge

: path loss slope

Slow Fading Margin, SFM

Standard Deviation,

From Point Location Probability to Area Location Probability

Jake Formula

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Slow fading margin SFM (Example)

Cell EdgeProbability

Cell Area Probability Factor F SFM

50% 75% 0 0 dB

75% 90% 0.67 5.5 dB

84% 94% 1.00 8 dB

90% 97% 1.28 10 dB

95% 99% 1.65 13.2 dB

SFM values presented for the different Cell Edge & Cell Area Probabilities Jakes formula used to convert Cell Area into Cell Edge Probability F: Factor to adapt SFM to required Cell Edge Probability Standard deviation assumed to be 8 dB

SFM = x F

0.000 0.126 0.253 0.3850.5240.6740.8421.0361.2821.6451.7511.8812.0542.326

5055606570758085909596979899

Factor Ffor

calculation of SFM

Cell edge probability

in %

0.000 0.126 0.253 0.3850.5240.6740.8421.0361.2821.6451.7511.8812.0542.326

5055606570758085909596979899

Factor Ffor

calculation of SFM

Cell edge probability

in %

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Gain Against Shadowing

Gain Against Shadowing is considered at the cell edgeAlso called multi server gain (because of multi-cell coverage probability)For the previous calculation of the Shadowing Margin the key assumption was a single, isolated cell However, if there are several cells providing coverage in an area then the probability of having enough field strength increases The Gain Against Shadowing reflects the possibility of switching to another cell available at a certain position

Example:Assume that there are 2 cells providing coverage and both cells are providing at the cell edge 50% location probability (A = B =50% are the location probabilities for the 2 cells)If the assumption is that the signals from the cells are uncorrelated then a joint probability could be calculated:P = (A+B) (A*B) = (50%+50%) (50%*50%) = 75%

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LTE DL Link Budget

Isotropic power required: Required signal power is calculated to take

into account the building penetration loss and indoor standard deviation as well as receiver sensitivity and additional margins.

Isotropic Power Required = Receiver Sensitivity RxAntennaGain + Interference

Margin + Body Loss Gain Against Shadowing + BPL + SFM

Max. allowed Path Loss Lpmax = Allowed Prop. Loss =

EIRP Isotropic Power Required

max. Pathloss Lpmax

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Introduction DL Link Budget & ParametersUL Link Budget & Parameters Examples

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LTE UL Link Budget

*PUSCH = Physical Uplink Shared Channel

Assumptions: same as in the DL

Transmitter Handset UE Tx Power

typical value: 23dBm (UE Class 3) Antenna TX/RX gain

typically assumed to be 0 dBi for data card 2 dBi possible

Body Loss UE: 0 dB (data user); 2-3dB (VoIP users) Otherwise (card) : 0dB

UL EIRP = UE Tx Power + UE Antenna Gain Body Loss

UE Tx capability :Power Class1 [+30] dBmPower Class2 [+27] dBmPower Class3 [+23 +/-2 dB] dBmPower Class4 [+21] dBm

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LTE UL Link Budget

Receiver eNodeB NodeB Noise Figure

vendor-specific for Flexi-BTS default values: 2.2 dB (w/o MHA) / 2 dB (with MHA)

Thermal Noise same formula as in DL only RBs considered which are allocated for UL transmission (1RB for 64Kbps, 15RBs for 384Kbps, 27 RBs for 1024 Kbps)

SINR Requirement same decision sequence as in the DL based on link level simulations differences in UL coming from different

MCS allocation strategy see next slide

Receiver Sensitivity = eNodeB Noise Figure + Thermal Noise + SINR

Requirement

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Required SINR in UL

The selection of MCS in UL is a trade-off between a lower required SINR value and the number of allocated PRBs per UE:UE output power is shared between the subcarriers assigned for transmission. The smaller the number of used subcarriers the higher is the power per subcarrier so the higher the coverage. On the other hand, lower number of PRBs per UE (lower number of subcarriers) requires a higher order MCS -increasing the required SINR. In this case, despite of a higher required SINR, a greater cell range could be obtained due to the accumulation of the total power on less PRBs used for the transmission.

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LTE UL Link Budget

Receiver eNodeB Rx Antenna Gain

Antenna gain changes with the antenna type & frequency band typical value: 18 dBi for a 3-sectored site / directional antenna

UL Load same assumption as in DL

Interference Margin based on system level simulations (analytical formula like in DL isnt trivial because of the interference nature in UL which is more complex due to UE mobility) see next slide

Cable Loss, Building Penteration Loss, Indoor Location Probability, Indoor Standard Deviation, Shadowing Margin & Gain Against Shadowingare the same as in DL

Isotropic Power Required = Receiver Sensitivity RxAntennaGain + Interference Margin + Cable

Loss Benefit of using MHA Gain Against Shadowing + BPL + SFM

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Interference MarginUplink

Uplink Interference Margin Currently obtained from system level simulations. Due to the non-deterministic

characteristic of uplink interferences it is difficult to make a mathematical model (like in downlink)

It is a function of cell load

IM as a function of Cell Load

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Introduction DL Link Budget & Parameters UL Link Budget & Parameters Examples

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Assumptions Parameter/Feature UL DL

Operating Band 2600 MHz 2600 MHzTransmission power max UE power 23dBm 43 dBm (20W Flexi RF Module)

Antenna Scheme Number of TX antennas = 1Number of RX antennas = 2

Number of TX antennas = 1Number of RX antennas = 2

Noise Figure UE: 7dB eNodeB: 2,2dB

Cell Load 50% 50%Scheduling Channel unaware with Round

Robin strategy Channel aware with Proportional

FairnessMast Head Amplifier Not Considered

(Feederless solution)Not Considered

(Feederless solution)

Antenna Gain 0 dBi 18 dBi

UE speed 3Km/h 3Km/hPlanning Margins Building Penetration Loss,

Shadowing Margin & Gain Against Shadowing NOT considered

Building Penetration Loss, Shadowing Margin & Gain Against

Shadowing NOT considered

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Pathloss as a function of Cell Edge Throughput DL

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Pathloss as a function of Number of PRBsDL

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Pathloss as a function of Number of PRBsUL