Long-Term Evolution compared to HSDPA

qualtaghblurtingMobile - Wireless

Dec 12, 2013 (3 years and 10 months ago)

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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

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Acknowledgement


Supervisor: Prof. Heikki Hämmäinen


Instructor: Jani Kokkonen M.Sc


Nokia Networks, System Technologies

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Agenda


Thesis introduction


HSDPA overview


3G LTE overview


Estimation work


Summary


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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.


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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.


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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.

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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.


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HSDPA: 3G architecture

UE

Node

B

Node

B

RNC

SGSN

GGSN

UTRAN

CN PS domain

HLR

AuC

EIR

Registers

CN

Uu

Iu

RNS

Iub

Iub

G
n

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

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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 Service

Physical Bearer
Service

UMTS Bearer Service

Radio Access Bearer Service

TE

MT

UTRAN

CN Iu edge

CN Gateway

TE

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HSDPA: Protocol stack (user plane)


GGSN

3G
-
SGSN

RNC

UE


Server

HLR


BS

MAC
-
hs

HS
-
DSCH
FP

L2

L1

Radio
L1

Radio
L1

MAC

PDC
P

IPv6/v4

u

Application

TCP/UDP

RLC
-
U

IP

UDP

GTP
-
U

L2

L1

L1

L2

HS
-
DSCH
FP

MAC
-
D

RLC
-
U

PDC
P

L1

L2

IPv6/v4

IP

UDP

GTP
-
U

L2

L1

IP

UDP

GTP
-
U

L2

L1

IP

UDP

GTP
-
U

L2

L1

IPv6/v4

TCP/UDP

Application

L1

L2

L1

L2

U

Iub

IuPs

Gn

Gr

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HSDPA: WCDMA RRC and PMM states

CELL_PCH

CELL_FACH

CELL_DCH

RRC state change

DCH channel
allocation time

2
-
5 s timer

2
-
5 s timer

If DL activated,
paging causes
delay

IDLE

PMM Detached

PMM
Connected

RRC Connection establishment time

GPRS
Attach

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.

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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.


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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.

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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

Service

Gateway

Subscription

Operator

service

network

AAA

Registers

Internet

Inter

-

connection

HA

RNC
functionalities
moved in the
base station.

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3G LTE: QoS bearer architecture

BS

SN

User

-

IP

Tunneling or forwarding

Transport

Radio

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.

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3G LTE: Mobility Management States

Idle



Active



Associate



RLID



Release



RLID



Detached



Connectio

n



Failure



, UE



local



release



Assign



UE_LLA,



Associate



RLID



Release UE_LLA &



RLID



Idle



Active



Associate



RLID



Release



RLID



Detached



Connection



Failure



, UE



local



release



Assign



UE_LLA,



Associate



RLID



Release UE_LLA &



RLID



Idle



Active



Associate



RLID



Rele

ase



RLID



Detached



Connection



Failure



, UE



local



release



Assign



UE_LLA,



Associate



RLID



Release UE_LLA &



RLID





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.

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3G LTE: Protocol stack (User plane)

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

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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.


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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)
Average TCP throughput (kbps)
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.

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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 utilization (%)
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 delay (s)
HSDPA (800)
3G LTE (6000)
3G LTE (3000)
3G LTE (1500)
3G LTE (800)
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Estimation work: Streaming session setup time

Phase

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

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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.

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Estimation work: VoIP End
-
toEnd Delay

RNC



3G
-
SGSN

GGSN

IP/MPLS/IPoATM
-
backbone

Node B

UE


IMS 1

3G

RNC



3G
-
SGSN

GGSN

IP/MPLS/IPoATM
-
backbone

Node B

UE


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.

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Estimation work: Web browsing

First Page Delay
0
2000
4000
6000
8000
10000
12000
40
300
600
Size of page and objects (kB)
Total delay (ms)
HSDPA (800/128)
HSDPA with always on
PDP 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)
Total delay (ms)
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.

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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)
HSDPA
with
always
on PDP
context
3G LTE
(6000)
3G LTE
(3000)
3G LTE
(1500)
3G LTE
(800)
3G LTE
(512)
time (ms)
DNS Query
RAB/Radio connection
PDP context
HTTP protocol
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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.