Estimating end-to-end performance in 3G Long-Term Evolution compared to HSDPA

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Estimating end-to-end performance in 3G Long-Term Evolution compared to HSDPA

Thesis work seminar presentation 18.10.2005

Mari-Jaana Pelkonen 51529B


Acknowledgement

• Supervisor: Prof. Heikki Hämmäinen

• Instructor: Jani Kokkonen M.Sc

• Nokia Networks, System Technologies


Agenda

• Thesis introduction

• HSDPA overview

• 3G LTE overview

• Estimation work

• Summary


Thesis introduction

• 3G Long-Term Evolution standardization effort started in late 2004 in 3GPP

• 3G networks are implemented at very slow phase. One major reason for the operators low investment willingness is the low capacity it offers to the operator and to the customer.

• IEEE is standardizing mobile WiMAX => Threat for loosing competitive edge.

• In Japan the telecom technology is one step forward: DoCoMo is driving the standardization.

• Why not 4G? 4G will be a system that connects all the existing and future networks seamlessly together. The technology is not yet ready for that. 3G LTE is a evolution step towards the 4G, enabling the operators to use the existing infrastructure longer.

• Target to standardize simple, IP optimize network, offering mobile DSL type connections.


Thesis introduction

• The scope of the thesis work was to prove that the performance in presented 3G LTE architecture is better than in the current available systems.

• 3G HSDPA was selected to the reference architecture.

• We were not only interested whether the new system is better, but why and why not.

• How much of the improvement could be achieved only improving capacity of the legacy systems?

• What is the impact of the new architecture solutions

• Different applications have different requirements for the network, performance is application specific. Therefore delay and throughput impact estimations were done for three applications: Web browsing, streaming video and VoIP.


Thesis introduction

• This thesis work was written in 3G Long-Term Evolution architecture project

• One part was literature study about 3G HSDPA performance and performance in general.

• 3G LTE specific part is taken from the architecture project and standardization contributions. The 3G LTE architecture presented in this work is DRAFT architecture. It will not be standardized as presented here.

• The estimation work is done using a Service performance Excel tool created to calculate delays in 3G networks. The tool consists of signaling flows for different applications. For that work, the 3G LTE specific parts were added to the tool.

• Values used in the tool are for 3G networks measured or estimated. To get 3G LTE values, I consulted several experts working with that area. Some of the values are targets, other derived from 3G values and the rest are educated guesses.


HSDPA

• High-Speed Downlink Packet Access is 3G performance enhancement technology. It does not change the core network, but only the radio interface in the downlink direction.

• HSDPA offers theoretical DL bit rates up to 14.4 Mbps.

• Only test networks implemented, not yet in commercial use. The effective bit rate offered to users is assumed to be around 800 kbps.


HSDPA: 3G architecture

UE

Node

B

Node

B

RNC

SGSN GGSN

UTRAN

CN PS domain

HLRAuC EIR

Registers

CNUu

Iu

RNS

Iub

Iub

Gn

Gi

UE = User Equipment

Node B = base station

RNC = Radio Network Controller

RNS = Radio Network System

CN = Core Network

UTRAN = Universal Terrestrial Radio Access Network

SGSN = Service Gateway Supporting Node

GGSN = Gateway GGSN Supporting Node


HSDPA: 3G QoS bearer architecture

End-to-end Service

Local Bearer Service

Backbone Bearer Service

CN Bearer Service

External Bearer Service

Iu Bearer Service

Radio Bearer Service

UTRA ServicePhysical

Bearer Service

UMTS Bearer Service

Radio Access Bearer Service

TE MT UTRAN CN Iu edge

CN Gateway

TE


HSDPA: Protocol stack (user plane)

GGSN3G-SGSNRNCUE Server

HLR

BSBS

MAC-hsMAC-hs

HS-HS-DSCH DSCH

FPFP

L2L2

L1L1Radio Radio L1L1

Radio Radio L1L1

MACMAC

PDCPDCPP

IPv6/v4u

ApplicatioApplicationnTCP/UDP

RLC-RLC-UU

IPIP

UDPUDP

GTP-GTP-UU

L2L2

L1L1L1L1

L2L2

HS-HS-DSCH DSCH

FPFP

MAC-MAC-DD

RLC-RLC-UU

PDCPDCPP

L1L1

L2L2

IPv6/v4

IPIP

UDPUDP

GTP-GTP-UU

L2L2

L1L1

IPIP

UDPUDP

GTP-GTP-UU

L2L2

L1L1

IPIP

UDPUDP

GTP-GTP-UU

L2L2

L1L1

IPv6/v4

TCP/UDPApplication

L1L1

L2L2

L1L1

L2L2

UU IubIub IuPIuPss

GnGn GrGr


HSDPA: WCDMA RRC and PMM states

CELL_PCHCELL_PCH CELL_FACHCELL_FACH CELL_DCHCELL_DCH

RRC state changeRRC state change DCH channel DCH channel allocation allocation timetime

2-5 s timer2-5 s timer 2-5 s timer2-5 s timer

If DL If DL activated, activated, paging paging causes delaycauses delay

IDLEIDLE

PMM DetachedPMM Detached

PMM PMM ConnectedConnected

RRC Connection establishment timeRRC Connection establishment timeGPRS GPRS AttachAttach

Mobile is allowed to send data in CELL_FACH and CELL_DCH states. DCH channel is dedicated channel for end user data.

CELL_PCH and URA_PCH (not shown in the figure) are used for paging.

In idle mode mobile has no radio connection.


3G LTE

• IP optimized network architecture

• Target is to solve the performance problems that current 3G architecture has and offer DSL type mobile internet connection.

• Simple architecture

• Short user plane RTT

• Cell capacity up to 100 Mbps

• In between 3G and 4G, interworking with existing and future network technologies inbuilt in the architecture.


3G LTE: Goodbye circuit switched voice!

• The evolution of packet switched network technology has made possible to transmit voice over IP network with acceptable end-user performance.

• The SKYPE is one of the most popular example of that.

• Current 3G and 2G networks are optimized for circuit switched voice, that makes them complex and not best possible for data traffic.

• Operators need to invest in and maintain two parallel networks: CS and PS.

• The all-IP architecture will be simple and cheap!

• Of course operators are not willing to cannibalize their CS voice business by offering VoIP. The success of SKYPE shows, that former or later customers are changing to the VoIP. To ensure not to loose the future profit, operators need to be inside the VoIP business.


3G LTE reference architecture

UE = User Equipment

BS = Base Station

SN-C = Serving Node (Control plane)

SN-U = Serving Node (User plane)

SGW = Service Gateway

Access Network

BS

BS

Serving Node - C

Serving Node - U

ServiceGateway

Subscription

Operatorservicenetwork

AAA Registers

Internet

Inter -connection

HA

RNC functionalities moved in the base station.


3G LTE: QoS bearer architecture

BS SN

User -IPTunneling or forwarding

TransportRadio

UE

Transport

Note: this is called bearerless compared to current 3G bearer architecture. Air interface connection establishment and modification is simplified by reducing the number of air-interface bearers.

Instead of four radio bearers, only one radio bearer has to be established. This leads to the significantly reduced radio connection setup time.


3G LTE: Mobility Management States

Idle Active Associate RLID

Release RLID

Detached

Connection Failure , UE local release

Assign UE_LLA, Associate RLID

Release UE_LLA & RLID


Release RLID

Detached





Release RLID

Detached




The number of channels reduced. Only one channel for user data. That channel is associated, if UE is in Active state.

That allows to reduce the number of states to three. If user is connected to the network, it is Idle or Active, whether it has data to send or receive.


3G LTE: Protocol stack (User plane)

All-IP protocol architecture, one continuous IP layer through all the network elements.


Estimation work

• Throughputs, link utilizations and transfer delays for TCP is estimated for different file sizes.

• Studied applications were VoIP, web browsing and streaming.

• For VoIP call, the most critical Key Performance Identifiers are session setup delay, end-to-end delay and delay variation. Session setup delay and end-to-end delay were estimated.

• For web browsing, the KPI studied is the click-to-content time, i.e. the time that takes after user selects page until it is loaded to his computer.

• KPIs for streaming are session setup delay and the throughput. Because throughput is studied separately, only session setup delay is estimated.


Estimation work: TCP throughputs

Average throughput in HSDPA and 3G LTE

0

1000

2000

3000

4000

5000

6000

7000

12 200 1000

Size of file (kB)

Av

era

ge

TC

P t

hro

ug

hp

ut

(kb

ps

)

HSDPA (800)

3G LTE (6000)

3G LTE (3000)

3G LTE (1500)

3G LTE (800)

TCP throughput for 3G LTE (800 kbps) is better with all file sizes than HSDPA

Due the TCP slow start effect, the TCP throughput is worse with small files than the large ones.


Estimation work: TCP Link utilizations and delays

Link Utilization in HSDPA and 3G LTE

0

20

40

60

80

100

120

12 200 1000

Size of file (kB)

Link

util

izat

ion

(%) HSDPA (800)

3G LTE (6000)

3G LTE (3000)

3G LTE (1500)

3G LTE (800)

3G LTE link utilization with same bit rate is notable better.

TCP delay in HSDPA and 3G LTE

0

2

4

6

8

10

12

14

12 200 1000

Size of file (kB)

TCP

dela

y (s

)

HSDPA (800)

3G LTE (6000)

3G LTE (3000)

3G LTE (1500)

3G LTE (800)


Estimation work: Streaming session setup timePhase 3G LTE delay (ms) HSDPA with always on

PDP context (ms)HSDPA delay (ms)

RTSP signaling 329 535 535

TCP connection establishment 77 156 156

Primary PDP context without RAB - - 769

RAB establishment 1408 1408

Secondary PDP context with RAB - 1975 1974

Delay before buffering 406 4073 4843

Buffering 5000 5000 5000

Total 5406 9073 9843


Estimation work: VoIP call with Internet Multimedia Subsystem System SIP session setup delay

(ms)End-to-end delay

(ms) (for 210 bytes VoIP packet)

RTT UE1-UE2-UE1 (ms)

3G LTE 2385 34 68

HSDPA with always on PDP context

7894 97 194

Difference 5509 63 126

For 3G LTE the SIP session setup delay is less than the circuit switch PSTN call setup delay.

The difference ín session setup delay is 5.5 second. Most of the difference is caused by the secondary PDP context activation and RAB procedures.

End-to-end delay for 3G LTE 30 ms is not notable for user. HSDPA 71 ms end-to-end delay is not notable with echo cancellation.

-External network delay not calculated

- Both end-users are connected to their own

IMSs.


Estimation work: VoIP End-toEnd Delay

RNC

3G-SGSN

GGSN

IP/MPLS/IPoATM-backbone

Node BUE IMS 1

3G

RNC

3G-SGSN

GGSN

IP/MPLS/IPoATM-backbone

Node BUE IMS 2

End-to-end delay consists of processing delays in UEs and in every network node in between them and transition delays between nodes.


Estimation work: Web browsing

First Page Delay

0

2000

4000

6000

8000

10000

12000

40 300 600

Size of page and objects (kB)

To

tal d

elay

(m

s)

HSDPA (800/128)

HSDPA with always onPDP context

3G LTE (6000/2500)

3G LTE (3000/1500)

3G LTE (1500/512)

3G LTE (800/384)

3G LTE (512/2576)

Second page delay

0

2000

4000

6000

8000

10000

12000

40 300 600

Size of page and objects (kB)

To

tal d

elay

(m

s)

HSDPA (800/125)

3G LTE (6000/2500)

3G Lte (3000/1500)

3G LTE (1500/512)

3G LTE (800/368)

3G LTE (512/2576)

Estimation is done for HSDPA with and without always-on PDP context.

First page delay includes radio connection establishment, PDP context activation and DNS query

Second page delay consists only HTTP signaling.


First page delay divided into parts

First page delay, page and objects total 40 kB

0

500

1000

1500

2000

2500

3000

3500

4000

HSDPA(800)

HSDPAwith

alwayson PDPcontext

3G LTE(6000)

3G LTE(3000)

3G LTE(1500)

3G LTE(800)

3G LTE(512)

tim

e (m

s)

DNS Query

RAB/Radio connection

PDP context

HTTP protocol


Summary

• Performance advantage of presented 3G LTE is clear for investigated applications.

• The session setup delay (PDP context and radio connection establishment) in 3G affects worst in short living applications, or applications that transfers only small amount of data.

• Enhanced air- interface effect is notable only with applications that transmit large files

• The capacity increase or RTT decrease is not the only way to the better performance. The IP connectivity added with bearerless model presented here is needed to reduce the session setup latencies.

Documents

Estimating end-to-end performance in 3G Long-Term Evolution compared to HSDPA