LTE Radio dimensioning - ST3 Telkomalfin.dosen.st3telkom.ac.id/.../8/2015/12/LTE-Radio-Dimensioning.pdf · –LTE Radio dimensioning Downlink ... throughput requirements at cell edge

LTE Radio dimensioning

Roger EkstrandRAN Design groupPA Radio kista sweden

LTE Radio Dimensioning | Ericsson Confidential | 2010-09-21 | Page 2

Agenda

› LTE Introduction

› LTE Radio dimensioning Methodology

– LTE Radio dimensioning Uplink

– LTE Radio dimensioning Downlink

› Case study Air interface Capacity

– Capacity vs. load

– Capacity after tuning

› Key parameters and capacity growth

› Drive tests Commercial LTE NW

› Summary


LTE Radio

Introduction


LTE Introduction - Air interface

› OFDM (Orthogonal Frequency Division Multiplexing) radio access technique is used in downlink

› SC-FDMA (Single Carrier Frequency Division Multiple Access) in uplink.

› Orthogonal properties in uplink as well as in downlink

– Own cell interference will be low.

› MIMO technology in downlink to allow high peak rates.

› Depending on channel quality LTE uses following modulation schemes; QPSK, 16QAM or 64QAM

› LTE supports both FDD and TDD (only FDD is covered here)


LTE Radio Access - Downlink

› Power and sensitivity calculations for dimensioning is made on

Resource Block (RB) level. In downlink the power per RB is fixed

› Bitrate/RB varies with a multitude of factors e.g. C/I, channel type,

modulation format etc.

∆f = 15 kHz

time

frequency

User A

User B

User C

180kHz (12 x 15) over 0.5ms = Resource block


∆f = 15 kHz

LTE DL Physical Resources

One slot0.5 m

s, 7 OFDM symbols

One Resource Block12 x 7 = 84 resource elements

12 sub-carriers

time

frequency

One subframe

1.0 ms, 14 OFDM symbols

One Scheduling Block

180 kHz, 2 RB and 1 ms


› RB in UL must be consecutive:

– The number of RB for each transmission is selected by the scheduler

– In dimensioning, it is means a trade off between coverage and capacity

› Uplink has power control

LTE introduction - Uplink

Time

Frequency

User 1 scheduled

180 kHz

1 ms

User 2 scheduled


Bandwidth – Resource Blocks

› The smallest bandwidth for

deployment is 6 Resource Blocks

– 1,08 MHz + guardband = 1,4

MHz

› The largest bandwidth for

deployment is 100 Resource

Blocks

– 18 MHz + guardband = 20 MHz

Channel Bandwidth BWChannel [MHz] 1.4 3 5 10 15 20

Number of Resource Blocks (nRB) 6 15 25 50 75 100

Bandwidth [RB]

Transmission Bandwidth Configuration [RB]

Channel Bandwidth [MHz]

Resourc

e b

lock

Channel e

dge

Channel e

dge

Active Resource Blocks


LTE DL peak rate64 QAM and 20 MHz and 4x4 MIMO

› 14 OFDM symbols per 1.0 ms subframe

› 64QAM - 6 bits per symbol

› 6 x 14 = 84 bits per 1.0 ms subframe

› 84bits/1.0ms = 84kbps per subcarrier

› 12 x 84kbps = 1.008Mbps per Resource Block

› 100 resource blocks in 20MHz

› 100 x 1.008Mbps = 100.8Mbps per antenna

› 4 x 4 MIMO: 403.2Mbps !!

› BUT in reality approx. ~300Mbps

› In reality ~25% is overhead (ref signals, control signalling etc)


LTE Radio dimensioning Methodology


LTE DimensioningProcess overview

1.Identify quality requirements at

cell edge

2.Calculate coverage

� Pathloss

� Cell range

� Site-site distance

3.Calculate Capacity

� Cell capacity

Quality at cell edge

- Path loss

- Cell range

- Site-to-site

distance

- Cell capacity

- MIMO

- Tx diversity- RBS power

- UE power

- UE Rx diversity

If input

requirements

are not met

Capacity

Coverage

Done

Typically the UL is limiting in terms of

throughput requirements at cell edge


Methodology for lte linkbudgets

UL Cell Edge Bit Rate

Cell Edge Bit rate per Resource Block

SINR value required per RB

RBS Sensitivity

Uplink Interference margin

Number of Resource Blocks

UL Link Budget (PL & distance)

Max Path Loss from Uplink

System Load on DL

Cell Edge Bit Rate on DL

UE Sensitivity

RBS power per RB

Band width


LTE Radio dimensioning

uPLINK


LTE DimensioningCoverage – Uplink link budget

› Lpmax maximum path loss due to propagation in the air [dB] › PRB transmitter power from the terminal per resource block [dBm]› SeNodeB eNodeB sensitivity per resource block [dBm]› BIUL noise rise or the uplink interference margin [dB]› BLNF log-normal fading margin [dB]› LBL, LCPL, LBPL body loss, car penetration loss, building penetration loss [dB]› Ga sum of RBS antenna gain and UE antenna gain [dBi]› LJ jumper loss [dB]

LfLGLLLBBSPL JaBPLCPLBLLNFIULeNodeBRBpmax −−+−−−−−−=

PRB

SeNodeB

Lpmax

BIUL

Maximum cell size

� All calculations for dimensioning are made per Resource Block (RB)


LTE DimensioningCoverage – Uplink Power

› Transmitted power from the

terminal per Resource Block

(180 kHz)

› In LTE there is tradeoff between

number of resource blocks and

power per resource block

23 dBm

17 dBm

Example of max UE power per RB

4 RB with 17 dBm

eachOne RB with 23 dBm



LTE DimensioningCoverage - SINR requirement, uplink

UL SINR vs throughput per RB


› Nt Thermal noise: -174 dBm/Hz

› Nf Noise figure in eNodeB [dB]

› BW Bandwidth per resource block: 180 kHz

› ʸ SINR [dB] required for dimensioning

service on cell border

γ+++= )log(10 WfteNodeB BNNSUL SNR vs Throughput per RB

0

100

200

300

400

500

600

700

800

900

-8 -4 0 4 8 12 16 20 24 28 32 36

SNRT

hro

ug

hp

ut

per

RB

(kb

ps)


1

2

35

4

Γ1

Γ� 2

Γ� 1

Γ� 4

Γ� 5Γ3

Γ4

Γ5

Γ2

LTE DimensioningCoverage – Uplink noiserise

› Perfect orthogonality within one

cell

› Interference comes from users

in other cellsSignal

Interference

FQN

INB

ULthermal

intercellthermalIUL

γ−=

+=

1

1

SINR target for UL

open loop power control

System load- Average number of occupied resource

blocks in system relative maximum resource available

Interference factor from other cells to serving cell



UE output power 23,0 dBm

Resource blocks (RBs) 9

Power per RB 13,5 dBm

Thermal noise -174,0 dBm

RBS noise figure 2,5 dB

User bitrate 0,50 Mbps

SNR -2,9 dB

RBS sensitivity -121,8 dBm

Antenna gain (RBS+UE) 13,0 dBi

Installation loss (RBS+UE) 0,2 dB

Penetration loss 18 dB

Fading margin 8,4 dB

Max. pathloss unloaded 121,6 dB

Utilization 20%

Interference margin 1,1 dB

Max. pathloss 120,5 dB

Range 0,75 km

Uplink link budget

Linkbudget example (urban, Uplink, 700MHZ)


23dBm divided by 9 RB

500 kbps divided by 9 RB

55 kbps/RB @ SINR -2.9 dB

UL SNR vs Throughput per RB

0

100

200

300

400

500

600

700

800

900

-8 -4 0 4 8 12 16 20 24 28 32 36

SNR

Th

rou

gh

pu

t p

er

RB

(k

bp

s)


LTE Radio dimensioning dOWNLINK


LfLGLLLBBSPL JaBPLCPLBLLNFIDLUErefTXpmax −−+−−−−−−= ,

› Lpmax maximum path loss due to propagation in the air [dB]

› PTX,ref transmitter power at the system reference point per RB [dBm]

› SUE UE sensitivity [dBm]

› BIDL noise rise or the downlink interference margin [dB]

› BLNF log-normal fading margin [dB]

› LBL, LCPL, LBPL body loss, car penetration loss, building penetration loss [dB]

› Ga sum of RBS antenna gain and UE antenna gain [dBi]

› LJ jumper loss [dB]

LTE DimensioningCoverage – Downlink link budget

PTX,ref

SUE

Lpmax

BIDL

Maximum cell size

� All calculations for dimensioning are made per Resource Block (RB)


LTE DimensioningCoverage – DL Power

29 dBm

35 dBm

1.4 MHz – 6 RB

5 MHz – 25 RB

Power per RB 20 W total power

available


5 MHz – 25 RB

› DL power is shared between all Resource Blocks:

– More bandwidth means less power per Resource Block

› To maintain coverage:

– Higher bandwidth requires higher total power

– Multi-later transmission schemes require higher total power


DL SNR vs throughput per RB

LTE DimensioningCoverage – downlink SINR requirements


› Nt Thermal noise: -174 dBm/Hz

› Nf Noise factor [dB]

› BW Bandwidth per resource block: 180 kHz

› ʸ SINR available on cell border [dB]

γ+++= )log(10 WftUE BNNSDL SNR vs Throughput per RB

0

200

400

600

800

1000

1200

1400

1600

-8 -4 0 4 8 12 16 20 24 28 32 36

SNR

Th

rou

gh

pu

t p

er

RB

(kb

ps)

SUE: -114.9 dBm

If:

NF: 7 dB

SINR: -0.4 dB


LTE DimensioningCoverage – DL noise rise

sa,maxRB

cDLRBtx

IDLLN

FQPB

,1 +=


3

Signal

Interference

Other/own cell interference factor

at cell edge

UE noise floor

)log(10 WftRB BNNN ++=

Power per

resource block

Maximum signal

attenuation to cell

edge

System load


RBS output power 2x60 W

Resource blocks (RBs) 50

Power per RB 30,8 dBm

Thermal noise -174,0 dBm

UE noise figure 7,0 dB

User bitrate 5,14 Mbps

SNR -0,4 dB

UE sensitivity -114,9 dBm

Antenna gain (RBS+UE) 13,0 dBi

Installation loss (RBS+UE) 0,2 dB

Penetration loss 18 dB

Fading margin 8,4 dB

Max. pathloss unloaded 132,1 dB

Utilization 44%

Interference margin 11,5 dB

Max. pathloss 120,5 dB

Range 0,75 km

Downlink link budget

Linkbudget example (urban, downlink, 700MHZ)


DL SNR vs Throughput per RB

0

200

400

600

800

1000

1200

1400

1600

-8 -4 0 4 8 12 16 20 24 28 32 36

SNR

Th

rou

gh

pu

t p

er

RB

(kb

ps)

10MHz = 50RB


Case study

Air interface Capacity


Planning aspectsAchieving high throughput

› Tuning the cell plan is an efficient way

to increase maximum throughput

› Ensure that the network has confined

cells with minimal overlap

– Remove high sites

– Tilt antennas

– Remove overlapping cells

› Interference reduced at lower system

load. Typical load is not 100%.

High sites generate interference outside the planned coverage area

Tilting antenna is an efficient way of achieving confined cells

Removing overlapping sectors is necessary for high cap, high throughput


SINRSignal to Interference and noise ratio

SARBtx

tx

LNQFP

P

NI

PSINR

+=

+=

Less loading in surrounding cells

=> Higher middle cell capacity

Maximum cell capacity and user throughput can be significantly higher in an unevenly

loaded network ⇒ All networks are unevenly loaded

DL SNR vs Throughput per RB

0

200

400

600

800

1000

1200

1400

1600

-8 -4 0 4 8 12 16 20 24 28 32 36

SNR

Th

rou

gh

pu

t p

er

RB

(kb

ps)


“F”-Factor

› The cell plan quality is modeled with the “F”-factor. It describes the ratio of received “unwanted” powers to “wanted” power of own cell at location near the cell edge.

› Assuming all cells have the same transmit powers, F-factor increases closer to the cell edge meaning higher grade of cell overlap or higher “pilot pollution”.

› “F”-factor used in the Radio dimensioning methodology.


1st Case study

Capacity

Vs load


Capacity impact due to different

- Band width

- system load

Case study 5 MHz


LTE throughput vs. load (BW: 5 MHz in 700 MHz band)

0,0%

10,0%

20,0%

30,0%

40,0%

50,0%

60,0%

70,0%

80,0%

90,0%

100,0%

0,0 3,0 6,0 9,0 12,0 15,0 18,0 21,0 24,0 27,0 30,0 33,0

DL Throughput [Mbps]

CD

F [

%]

5 MHz High load

5 MHz Medium load

5 MHz low load

Average achievable bitrates 7 - 12 Mbps throughput

Antenna tilt: 4°

System Load:25%, 45% and 87%

User Distribution:

Uniform

Average achievable bitrate vs. Load- LTE 5 MHz

Cell troughput at max system load: 6.9 Mbps



- Band width

- system load

- antenna tilt

(Cell confinement)

Case study 5 MHz



Antenna tilt: 8°



0,0%

10,0%

20,0%

30,0%

40,0%

50,0%

60,0%

70,0%

80,0%

90,0%

100,0%

0,0 3,0 6,0 9,0 12,0 15,0 18,0 21,0 24,0 27,0 30,0 33,0


CD

F [

%]

5 MHz High load

5 MHz Medium load

5 MHz low load




- Band width

- system load

Case study 10 MHz



Antenna tilt: 4°

System Load:25%, 45% and 87%

User Distribution:

Uniform



0,0%

10,0%

20,0%

30,0%

40,0%

50,0%

60,0%

70,0%

80,0%

90,0%

100,0%

0,0 5,0 10,0 15,0 20,0 25,0 30,0 35,0 40,0 45,0 50,0 55,0 60,0 65,0 70,0 75,0


CD

F [

%]

10 MHz High load

10 MHz Medium load

10 MHz low load




- Band width

- system load

- antenna tilt

(Cell confinement)

Case study 10 MHz



Antenna tilt: 8°



0,0%

10,0%

20,0%

30,0%

40,0%

50,0%

60,0%

70,0%

80,0%

90,0%

100,0%

0,0 5,0 10,0 15,0 20,0 25,0 30,0 35,0 40,0 45,0 50,0 55,0 60,0 65,0 70,0 75,0


CD

F [

%]

10 MHz High load

10 MHz Medium load

10 MHz low load



2nd Case study

Capacity

after tuning


- Band width

- system load

- antenna tilt

(Cell confinement)

Summary from the Case study

20 MHz - High Load 27,8 Mbps 24,8 Mbps

20 MHz - Mid Load 36,4 Mbps 24,8 Mbps

20 MHz - Low Load 46,1 Mbps 24,8 Mbps
















Cases Tilt 4°DL average

achievable bitrate

DL potential capacity per

cell 90 % Utilization

Cases Tilt 8°DL average

achievable bitrate



•High speed for the end users at

typical load

•50% potential capacity increase

with well tuned NW

20 MHz - High Load 2 750 24,8 Mbps

20 MHz - Mid Load 1 833 24,8 Mbps

20 MHz - Low Load 1 217 24,8 Mbps

10 MHz - High Load 1 375 12,4 Mbps

10 MHz - Mid Load 917 12,4 Mbps

10 MHz - Low Load 608 12,4 Mbps

5 MHz - High Load 687 6,2 Mbps

5 MHz - Mid Load 458 6,2 Mbps

5 MHz - Low Load 303 6,2 Mbps

Cases Tilt 4°No of users with 2

GB monthly usage




Key parameters

And

CAPACITY GROWTH


traffic distributed over cellsin a Radio Access network

0

1

2

3

4

5

6

7

8

9

10

0%

5%

10

%

15

%

20

%

25

%

30

%

35

%

40

%

45

%

50

%

55

%

60

%

65

%

70

%

75

%

80

%

85

%

90

%

95

%

100

%

Percentage of sectors (%)

Rela

tive

se

cto

r lo

ad

Sector speech BH relative load Sector HS BH relative load

50% of total HS traffic carried by 17% of the sectors

50% of total Speech traffic carried by 23% of the cells

Both speech and HSDPA traffic is very unevenly distributed on cell level. Traffic volume in most loaded site is about 9 times as loaded as average. 65% of the cells carry less than average cell load.

Most cells could be considered to be coverage cells.

Source: Ericsson measurements from one example network. Results are however well representative for other networks as well

Normalized average cell load


Resource utilization (HSPA and DCH)

Rtotal

Racc

HSPA - High load criterion

High load – new

user cannot get

acceptable rate

• High load criterion:• potential new user cannot reach acceptable target rate due to

resource outage

HSPA analysis


0

1000

2000

3000

4000

5000

6000

Cells

Th

rou

gh

pu

t [k

bp

s]

or

data

vo

lum

e [

Mb

yte

/ho

ur]

0

5

10

15

20

25

30

35

CQ

I

Cell Throughput (Cell_Thp)

User Throughput (User_Thp)

HS traff ic volume (HS_DL_Data_Volume)

Average CQI (CQI_Avg)

commercial HSPA network

User target rate 500 kbps


How to expand HSPA with Traffic growth

› Some cells need tuning

› Some cells will not have enough Codes & Power to match expected Growth

– need a second carrier

– QoS, HSDPA and R99 on same carrier

› Some cells will need Channel Element expansion only

› Expand RNC capacity accordingly

› Expand IUB capacity accordingly

› In general the following measures are required:


Similar with LTEHow to expand with Traffic growth

› Some cells need tuning

› Some cells will not have enough BW & Power for match expected Growth

– need more BW (PRB)

– QoS, NGBR and GBR on the same carrier

› Most cells will only need license expansion

› Expand SGW/MME capacity accordingly

› Expand S1/X2 capacity accordingly

› In general the following measures are required:


LTE Radio Key parameters for growth

› Simple, as few parameters as possible (PAYG):

–Bandwidth (e.g. 5, 10, 15, 20 MHz)

–Power (e.g. 20, 40, 60W)

–Throughput DL/UL (Cell throughput)

–PRB (RB utilization%)

–Connected users (No of active users )


Integrity DL Tput (Observability)

DL Throughput

Ue Rep RANKUe Rep CQI

Used Tx-Rank

DL Packet Loss

PELR HO# Active UE’s DL

PELRUu

DL Latency

HARQ%

QPSK16QAM

64QAM

RLC%

HARQ%

QPSK16QAM

64QAM

# Active DRB’s DL

RLC Delay

MAC Delay


Admission control basicsGeneric mechanism

› The purpose of the admission control is to leave a headroom for– other traffic not subject to admission control for the specific resource (signaling, non-GBR)

– incoming user mobility

– varying radio conditions and intra-cell mobility

› Valid for dynamic resources

› Goal is to protect other traffic and to minimize call dropping (“service blocking over service dropping”)

Admission

Threshold

LoadMax capacity

Allow all requests

Block new accesses

Allow incoming mobility


Admission control basics

› Non-GBR capacity varies with GBR load

– Handled dynamically in the scheduler by prioritizing the GBR over NGBR

› Admission threshold “reserves” a minimum NGBR capacity

Admission

Threshold

LoadMax capacity

Non-GBR capacity

GBR capacity


Drive tests

Commercial LTE NW


LTE Dl throughput – Drive test LTE NW, July 2010

Average DL througput: 34,2 Mbps

Median DL througput 32,5: Mbps

Q2 -2010


LTE Ul throughput – Drive test commercial LTE NW, July 2010

Q2 -2010


Commercial 4G Price Plan

80 USD5 USD 25 USD 30 USD 45 USD

40 Mbps2 Mbps 2 Mbps 6 Mbps 10 Mbps

30 GB2 GB 5 GB 10 GB 20 GB

Included40 USD Included Included Included

Included5 USD/month 5 USD/month Included Included

Price per month

”Start”(3G)

”På gång”(3G)

”Fri”(3G)

”Fri +”(3G) 4G

Speed

Telia Secure Surf

USB modem

Data per month


summary

› LTE Radio Dimensioning requires initial design, radio

planning, NW tuning in similar way as HSPA

› LTE is based on a one frequency reuse – therfore well designed/tuned NW and cell confinement are important

(i.e. antenna placements, directions and tilt are keys)

› Expansion of radio resources depends on end user target

rate vs. cell throughput, i.e. The definition of satisfied users

› LTE in commercial NW’s today deliver performance acording

to expectations


Documents

LTE Radio dimensioning - ST3 Telkomalfin.dosen.st3telkom.ac.id/.../8/2015/12/LTE-Radio-Dimensioning.pdf · –LTE Radio dimensioning Downlink ... throughput requirements at cell edge