lte networks: how far are the achievable capacities from the theoretical ones? – keynote from...

LTE Networks: how far are the achievable capacities from the theoretical ones?

ICUMT 2012, October 3-5, Sankt Petersburg, Russia

Agenda

Copyright © IS-Wireless | www.is-wireless.com 2

1. Broadband LTE Radio Interface

2. Method for Capacity Calculations

3. Influence of Interference on Network Capacity

4. Practical LTE Capacity

5. LTE Capacity - Summary

6. 4G-Online.net – Business Case Calculations

Broadband LTE Radio Interface

Broadband LTE Radio Interface 3GPP Radio Access Networks Evolution


1997 2000 2005 2009 2011

LTE LTE-Advanced

2G 3G 3.9G 3.5G 4G

1992

GPRS

2.5G

GSM UMTS HSPA

Phase 1

Phase 2

Rel. 96

Rel. 97

Rel. 98

Rel. 99

Rel. 4

Rel. 5

Rel. 6

Rel. 7

Rel. 8

Rel. 9 Rel. 10

3GPP

Release

Voice only 14.4kbps UL: 128kbps

DL: 384kbps

UL: 11Mbps

DL: 28Mbps

UL: 75Mbps

DL: 325Mbps

UL: 500Mbps

DL: 1Gbps

Highest

Data Rate

Broadband LTE Radio Interface LTE Overview


SGW

MME

eNB

eNB

eNB

Internet/ ...

Radio Access Network Core Network

Flat architecture and All-IP structure

Theoretical Throughputs

75Mbps 325Mbps (4x4)

172Mbps (2x2)

20MHz

37Mbps 138Mbps (4x4) 10MHz

Uplink Downlink Direction

Channel BW

• VoIP/video conferences

• WWW

• Video on Demand

• Online Gaming

• FTP

• always-on concept

• World-wide roaming • High throughputs

• Mobile internet

• Low latencies

LTE Services

IP

IP

IP

IP

IP

IP

IP

The main targets / requirements for the LTE are (ref. TS 25.913):

• Peak data rate: e.g. 100 Mbps (downlink) and 50 Mbps (uplink)

• Scalable bandwidth: 1.4, 5, 10, 15, 20MHz

• At least 200 VoIP users served in a 5MHz FDD bandwidth

(giving 800 VoIP users in 20MHz bandwidth)

• Efficient support of the various types of services, especially from the PS domain

(e.g. Voice over IP)

eNB

Broadband LTE Radio Interface LTE Performance Requirements


Method for Capacity Calculations

Method for Capacity Calculations Example Calculations of Offered Capacity Calculation


carrier

1 sector

1 carrier

Ustawienia: BW_network = 30MHz

Frequency Reuse = 3 BW_sector = BW_network/3 = 10MHz

50% of total area

experienced SNIR = 7dB

SNIR1 = 1.5dB

SNIR2 = 7dB

SE – spectral efficiency for a certain SNIR

50% of total area

experienced SNIR = 1.5dB

MCS = QPSK ½ SE1 = 2 * ½ = 1bps/Hz

MCS = 16QAM ½ SE2 = 4 * ½ = 2bps/Hz

SNIR_usage1 = 50% of total area = 0.5

SNIR_usage2 = 50% of total area = 0.5

SNIR_usage – percent of area on which a certain SNIR occurs

SE_average = ∑ SEi * SNIR_usagei

Offered sector capacity

From MCS curves

SE_average = SE1*SNIR_usage1 + SE2*SNIR_usage2 = 1*0.5 + 2*0.5 = 1.5bps/Hz

R_sector = BW_sector *SE_average = 10MHz * 1.5bps/Hz = 15Mbps

Each sector – a different carrier

This method is used to calculate average capacity (overhead neglected)

Impact of Interference on Network Capacity

Impact of Interference on Network Capacity A Model Network for Capacity Calculations


Inter site distance = 2km

EIRP = 61dBm

Radio interface: LTE or Mobile WiMAX

Reuse 1 – each sector of a single BS is assigned full BW

Reuse 3 – each sector of a signle BS is assigned 1/3 of the full BW

Average sector

capacity is calculated

in the presence of

interference

Frequency Reuse 3 Frequency Reuse 1

Max SNIR = 16.9dB

Min SNIR = -4.7dB

Max SNIR = 65dB

Min SNIR = -3.3dB

SNIR range = ~21dB SNIR range = ~68dB

Considered Cell

Cell edge

(SNIR < 0dB)

Best SNIR but

less resources per sector Steep SNIR and

all resources per sector

Impact of Interference on Network Capacity Downlink SNIR [dB] Distribution Snapshot Example


Practical LTE Capacity

System Peak throughput

Average throughput

Cell edge throughtput

Peak / Cell edge ratio

LTE Rel. 8 1x1, reuse 1

64.2 Mbit/s 27.0 Mbit/s 9.6 Mbit/s 6.6




121.9 Mbit/s

27.0 Mbit/s 9.6 Mbit/s 12.6




231.7 Mbit/s

27.0 Mbit/s 9.6 Mbit/s 24.1



LTE-A (Rel. 10) 8x8, reuse 1


LTE-A (Rel. 10) 8x8, reuse 3


Assumptions:

- Throughput is calculated for 1 UE (UE gets all resources)

- For reuse 3 each sector is assigned 1/3 of 20MHz (6.67MHz)

- MIMO increases throughput only near eNB (peak throughput increase)

- Cell edge throughput is calculated for 5% of area with worst SNIR

- Signalling resources not excluded

Practical LTE Capacity Sector Throughput


LTE Capacity - Summary

LTE Capacity - Summary Theoretical vs Practical Network Throughputs


Bandwidth / System Type

10MHz LTE FDD

20MHz LTE FDD

20MHz LTE TDD (3:2)

Theoretical Throughputs

• Achievable in lab

• Don’t take into account signalling

• Neglect propagation conditions

Practical Throughputs

• Relate do the propagation conditions

• Take into account real signalling

• Calculated in real propagation conditions

(e.g. interference, channel distortions, noise, etc.)

Practical sector data rate

11.6Mbit/s

23.3Mbit/s

12.7Mbit/s

Theoretical sector data rate

50Mbit/s

100Mbit/s (325Mbit/s with MIMO)

65Mbit/s

Comparable with fixed

lines (e.g. DSL)

4G-Online.net – Business Case Calculations

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lte networks: how far are the achievable capacities from the theoretical ones? – keynote from...

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