a comparison between one-way delays in operating hspa and lte networks

A Comparison Between One-way Delays inOperating HSPA and LTE Networks

Markus Laner, Philipp Svoboda, Peter Romirer-Maierhofer,Navid Nikaein, Fabio Ricciato and Markus Rupp

Vienna University of Technology, AustriaFTW, Austria

EURECOM, France

WINMEE’12, May18, 2012, Paderborn, Germany

Intro. Measurements Results Interpretation Conclusion

Outline

1 Introduction

2 Measurements

3 Results

4 Interpretation

5 Conclusion

M. Laner, TUV Comparison of Delays in HSPA and LTE 2012-05-18 2/16


Outline

1 Introduction

2 Measurements

3 Results

4 Interpretation

5 Conclusion



Motivation

I Latency affects user experience

I Increasing importance/attention

I What to improve? → Measurements

Low Latency

Future Appl.?Video

Gaming

VoiceM2M

Alarm



Contributions

I Measurements of LTE and HSPA latency

I Verification of LTE design goals (popular estimates)I Comparing influences of

− Packet size− Data rate

I QoS estimates for latencysensitive applications


latency estimates [Holma, 2010]

20

0

30

10

RTT (ms)

HSPA

NodeB

TTI

UE

Buffering

Retransm.

Scheduling

UE

LTE

TTI

Buffering

Retransm.

Scheduling

Core

RNC

eNodeB

HSPA High Speed Packet AccessLTE Long Term Evolution

RTT Round Trip TimeQoS Quality of Service


Outline

1 Introduction

2 Measurements

3 Results

4 Interpretation

5 Conclusion



Definition of LatencyI Latency [3GPP, TS 25.913]:

− Control-plane: Transition time from idle to connected state− User-plane: Packet (0 Bytes) available at IP layer of UE/GW

I Ambiguities:− Size: IP datagrams vs. IP fragments− Availability: Start vs. end− Intermediate interfaces: No IP

I Def.: Last bit of an IP datagram passing each interface

I Q: Is this def. enough for low data rate applications?

IP datagram, 4 fragmentsInterface 1

Interface 2

Interface 3

time

∆1,2 ∆2,3

∆1,3



Setup

I 3G and 4G networks (3GPP Rel. 8)

I Modem: Huawei E392, triple-mode

I FDD: 10 MHz (HSPA) vs. 20 MHz (LTE)

I Radio: Line-of-sight, 130 m

ServerServer

Server

Probe

Internet

RNC GGSN

NodeBGn

SGi

Gi

USB

∆

∆

∆

Modem

S1−U

HSPA

LTE

owd

cnran

eNodeB

ProbeProbe

Probe

ProbeSAE GW

PC

Client

PC

Server



Measurement Devices

I Passive packet sniffing (wiretaps) - five Probes

I GPS synchronized

I Protocol parsing

I Packet identification → timestamp comparison

ServerServer

Server

Probe

Internet

RNC GGSN

NodeBGn

SGi

Gi

USB

∆

∆

∆

Modem

S1−U

HSPA

LTE

owd

cnran

eNodeB

ProbeProbe

Probe

ProbeSAE GW

PC

Client

PC

Server



Traffic Generation

I Data-traffic influences latency

I Independent uplink and downlink

I Random packet size and inter-arrival time[IETF, RFC 2330][Fabini, 2009][Baccelli, 2007]

I Blocked measurements → fixed data-rate

Internet

HSPA

modem



Outline

1 Introduction

2 Measurements

3 Results

4 Interpretation

5 Conclusion



Comparison RTT

I LTE: 36 ms median RTT

I HSPA: 42 ms median RTT

I Minor improvements of 14%

0 20 40 60 800

0.5

1

overall round−trip time (ms)

em

piric

al C

DF

LTE

HSPA


RTT RoundTrip Time

CDF CumulativeDistribution Function


One-way Delay in RAN

I Downlink: LTE very fast (7 ms)

I Uplink: HSPA fast (15 ms)

I Main reasons for minor performance of LTE:Low layer signaling, scheduling, DRX, and cell configuration(e.g. SR periodicity)

0 15 30 45 600

0.5

1

one−way delay RAN (ms)

em

piric

al C

DF

LTE downlink

LTE uplink

HSPA downlink

HSPA uplink


RAN Radio AccessNetwork

CDF CumulativeDistribution Function


One-way Delay in Core

I Uplink and Downlink equal (1.5 ms)

I HSPA and LTE similar (1.5 ms)

I Caution: high load in HSPA → tail

0 1 2 3 4 50

0.5

1

one−way delay CN (ms)

em

piric

al C

DF

LTE downlink

LTE uplink

HSPA downlink

HSPA uplink



LTE Delay vs. Packet Size

I Scatterplot: No diagonal components⇒ no correlation

I Reason: High bandwidth & LTE scheduling

Downlink

0 10 20 30 40 500

1

2

3

4

5

overall one−way delay (ms)

data

gra

m s

ize (

kB

yte

)

0

1

Uplink

0 10 20 30 40 500

1

2

3

4

5


data

gra

m s

ize (

kB

yte

)

0

1



LTE Delay vs. Packet Size

I Scatterplot: Diagonal components⇒ positive correlation

I Reason: HSPA scheduling & network load

Downlink

0 10 20 30 40 500

1

2

3

4

5


data

gra

m s

ize (

kB

yte

)

0

1

Uplink

0 10 20 30 40 500

1

2

3

4

5


data

gra

m s

ize (

kB

yte

)

0

1



Delay vs. Data-rateI LTE: independent of packet-size

I HSPA: dependent of packet-size (2 curves)

I Delay decreasing with increasing ratestrong contrast to fixed networks (queuing)

256 1k 4k 16k 64k 256k 1M0

15

30

45

60

data rate (Byte/s)

me

dia

n o

ve

rall

on

e−

wa

y d

ela

y (

ms)

LTE downlink

LTE uplink

HSPA downlink

HSPA uplink



Outline

1 Introduction

2 Measurements

3 Results

4 Interpretation

5 Conclusion



Latency Sensitive Traffic

Online Gaming

I Data-rate: 1 kByte/s – 16 kByte/s

I Latency: Impairments at RTT > 50 ms

M2M (e.g., event-driven, real-time)

I Data-rate: < 1 kByte/s


VoIP, video call

I Data-rate: 4 kByte/s – 256 kByte/s




Network Type vs. Traffic

I QoS requirements vs. network performance

I Not accounting for IP backbone and server processing delays

I 3G/4G networks not (yet) ready to host certain apps.

I Source of QoS parameters [LOLA, D3.6, 2012]

Application LTE (up/down) HSPA (up/down)

Online Gaming ( 31 / 13 ) ms ( 12 / 17 ) msM2M ( 30 / 10 ) ms ( 10 / 16 ) msVoIP ( 30 / 15 ) ms ( 35 / 16 ) ms


QoS Quality of ServiceM2M Machine to MachineVoIP Voice over IP


Outline

1 Introduction

2 Measurements

3 Results

4 Interpretation

5 Conclusion



Conclusions

I LTE shows improved latency over HSPA (14%)

I Decreasing latency with increasing data-rate

I HSPA uplink scheduling outperforms LTE

I New low-latency transmission techniques [LOLA project]

I Semi-persistent scheduling in LTE

I Latency sensitive apps. require improvements



Thank you for your attention!

Markus Laner, Philipp Svoboda, Peter Romirer-Maierhofer,Navid Nikaein, Fabio Ricciato and Markus Rupp

Vienna University of Technology, AustriaFTW, AustriaEURECOM, France

[email protected]


Ref.

ReferencesI 3GPP. TS 25.913, Requirements for Evolved UTRA and Evolved UTRAN,

http://www.3gpp.org/.

I H. Holma and A. Toskala, WCDMA for UMTS: HSPA Evolution and LTE (5thEdition). Wiley, 2010.

I M. Laner, P. Svoboda, and M. Rupp, Dissecting 3G Uplink Delay by Measuringin an Operational HSPA Network, in PAM’11, Atlanta, Georgia, 2011.

I J. Fabini, L. Wallentin, and P. Reichl, The importance of being really random:methodological aspects of IP-layer 2G and 3G network delay assessment, inICC’09, Dresden, Germany, 2009.

I V. Paxson et al. (1998) RFC 2330, Framework for IP Performance Metrics,http://www.ietf.org/rfc/rfc2330.txt.

I F. Baccelli et al., On Optimal Probing for Delay and Loss Measurement, inIMC’07, San Diego, California, 2007.

I libpcap - library for network traffic capture, http://www.tcpdump.org/.

I Darwin Project, http://userver.ftw.at/∼ricciato/darwin/.

I Endace DAG, http://www.endace.com/.

I LinuxPPS, http://wiki.enneenne.com/index.php/LinuxPPS support.

I EU FP7 LOLA Project, http://www.ict-lola.eu/.M. Laner, TUV Comparison of Delays in HSPA and LTE 2012-05-18 17/16

a comparison between one-way delays in operating hspa and lte networks

Documents