MAP-Tele Manuel P. Ricardopaginas.fe.up.pt/~mricardo/07_08/wnp/slides/wnp-mpr-qos.pdfWNP-MPR-qos 1...

WNP-MPR-qos 1

Wireless Networks and Protocols

MAP-Tele

Manuel P. Ricardo

Faculdade de Engenharia da Universidade do Porto

WNP-MPR-qos 2

Topics Scheduled for Today

♦ …

♦ Quality of Service

» Characterization and models

» Case studies

» Research issues

♦ …

WNP-MPR-qos 3

♦ This set of slides is made in articulation with the QoS lectures

given by Prof. Ruela in the Network Services and Applications

course. Please review Prof. Ruela’s slides» http://elearning.ua.pt/@@8f1af8c4466670c37379dee68a1e0119/courses/1/nsa_map/content/_221536_1/NAS_QoS_1.pdf

» http://elearning.ua.pt/@@8f1af8c4466670c37379dee68a1e0119/courses/1/nsa_map/content/_223126_1/NAS_QoS_2.pdf

♦ In this lecture we will recall briefly the QoS basics concepts and

then focus in the QoS in wireless networks, namely 3GPP-QoS

and IEEE-wireless-QoS

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Quality of Service

♦ From a user point of view

» level of satisfaction experienced by the user of an application delivered

through a network. Depends on

– User’s subjective evaluation and expectations

– Terminal capabilities

– Performance of networks

♦ From a network point of view

» ability of giving differentiated treatment to traffic flows or traffic classes

» provide them with different levels of delivery assurance

– bandwidth, delay, loss

» network behaviour quantifiable by a set of performance parameters

WNP-MPR-qos 5

QoS principles

♦ The provision of QoS requires

» cooperation of various protocol layers

» cooperation of network elements in the end-to-end chain

♦ QoS requirements of users/applications

must be mapped into values of network service attributes

♦ Attributes of a network service

» may be described by a set of performance (QoS) parameters

» which must be observable measurable and controllable

♦ Networks and users must negotiate contracts,

which are described by means of traffic and QoS parameters

WNP-MPR-qos 6

QoS

QoS is an end-to-end problem, handled at multiple communication layers

Physical

Network

Transport

Data link

Application

Mobility

Security

Multicast

Quality of Service

IP layer

IP user plane IP control plane

Application app. control

Application node

IP layer

IP user plane IP control plane

Application app. control

IP IP

Control

IP IP

Control

Application control (e.g. SIP)

App. node-backbone

control plane interface

App. node-backbone

user plane (IP) interface

IP Backbone

Inter-domain interface

Application node

WNP-MPR-qos 7

QoS building blocks in a packet

network

• Data plane (traffic flows/packets)– Shaping, Policing

– Classification & Marking

– Queuing and Scheduling (service discipline)

– Congestion control and Queue management

• Control plane– QoS mapping

– Admission control

– QoS routing

– Resource reservation/allocation

• Management plane– Resource provisioning

– Policy management

network

packet switch

(router, switch)

Traffic source/

previous network elementfeed-back based,

end-to-end (TCO, RTP+RTCP)

inter-network element

WNP-MPR-qos 8

IP QoS Models

♦ Very important!» Please review NSA slides on QoS» http://elearning.ua.pt/@@8f1af8c4466670c37379dee68a1e0119/courses/1/nsa_map/content/_223126_1/NAS_QoS_2.pdf

♦ 2 service models

♦ Integrated Services (IntServ) model, which is oriented towards the

» Resource ReSerVation Protocol (RSVP)

» TSpec, FlowSpec

» Token Bucket

» Controlled load

» Guaranteed service (maximum delay)

♦ Differentiated Services (DiffServ) model» DS field

» Per-Hop Behaviours (PHB),

» Assured Forwarding (AF)

» Expedited Forwarding (EF)

» Bandwidth broker

WNP-MPR-qos 9

QoS in UMTS

WNP-MPR-qos 10

Quality of Service in UMTS

TE MT RAN CN EDGE NODE

CN Gateway

TE

UMTS

End-to-End Service

TE/MT Local Bearer Service

UMTS Bearer Service External Bearer Service

UMTS Bearer Service

Radio Access Bearer Service CN Bearer Service

Backbone Bearer Service

RAN Access Bearer Service

Radio Bearer Service

Physical Radio

Bearer Service Physical

Bearer Service

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QoS management functions,

UMTS bearer service, user plane

Resource Manager

Mapper

Class if.

Cond.

Resource Manager

Resource Manager

Mapper

Resource Manager

Mapper

Resource Manager

Resource Manager

Cond.

Class if.

Cond.

MT Gateway CN EDGE RAN

BB netw ork service RAN Access network service RAN phys. BS

data f low with indication of direction

TE Ext. Netw.

Local BS External BS

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♦ Class

» Classifies and marks packet

» At the entry of network (downlink � GGSN, uplink � terminal)

♦ Cond – Traffic conditioner

» Enforces compliance of flow with QoS attributes

» At the entry of the network and radio segment

♦ Mapper

» marks packet with QoS information related to bearer service below

♦ Resource manager

» Decides when to send the packet so that QoS is satisfied

» Manages the resources it sees

– Packet queues, ARQ mechanisms, modulations and codes, power, spreading codes

WNP-MPR-qos 13

UMTS QoS Classes

Background

download of

emails

Web browsingstreaming videovoiceExample of the

application

Destination is

not expecting

the data within a

certain time

Preserve

payload content

Request response

pattern

Preserve payload

content

Preserve time

relation (variation)

between

information entities

of the stream

Preserve time relation

(variation) between

information entities of

the stream

Conversational pattern

(stringent and low

delay)

Fundamental

characteristics

BackgroundInteractive classStreaming classConversational classTraffic class

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UMTS Bearer Service Attributes –

Examples♦ Traffic class ('conversational', 'streaming', 'interactive', 'background')

♦ Maximum bitrate (kbps)

» compliance enforced by

token-bucket(Maximum-bitrate , Maximum-SDU-size)

» used to reserve codes radio interface - downlink

♦ Guaranteed bitrate (kbps)

» traffic compliance enforced by

token-bucket(Guaranteed-bitrate , Maximum-SDU-size)

» Delay/ reliability attributes guaranteed only for traffic up to the Guaranteed bitrate

» Used for admission control and resource allocation

♦ Maximum SDU size (octets)

♦ SDU error ratio

» fraction of SDUs lost or detected as erroneous

♦ Residual bit error ratio

» Undetected bit error ratio in the delivered SDUs.

♦ Transfer delay (ms)

» 95th percentile of the delay distribution

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Token Bucket

Token Bucket Counter(TBC) - number of remaining tokens at any time

b

TBC

Time

OK OK Non-compliant

L1<TBC L2<TBC L3>TBC

b-L1

b-L1+r*∆T

WNP-MPR-qos 16

QoS attributes versus traffic classes

XSignalling Indication

XXSource statistics

descriptor

XXXXAllocation/ Retention priority

XTraffic handling priority

XXGuaranteed bit rate

XXTransfer delay

XXXXDelivery of

erroneous SDUs

XXXXResidual bit error ratio

XXXXSDU error ratio

XXSDU format

information

XXXXMaximum SDU size

XXXXDelivery order

XXXXMaximum bit rate

Background classInteractive classStreaming classConversational classTraffic class

WNP-MPR-qos 17

UMTS Bearer Service Attributes

(Rel. 7!)

Yes/No (9)Signalling Indication

Speech/unknow

n

Speech/unknow

n

Source statistic descriptor

1,2,31,2,31,2,31,2,3Allocation/Retention priority

1,2,3 (9)Traffic handling priority

<= 256 000 (2)<= 256 000 (2)Guaranteed bit rate (kbps)

300 (8) –

maximum value

100 – maximum

value

Transfer delay (ms)

10-3, 10-4, 10-610-3, 10-4, 10-610-1, 10-2, 7*10-3,

10-3, 10-4, 10-510-2, 7*10-3, 10-3,

10-4, 10-5SDU error ratio

4*10-3, 10-5, 6*10-8 (7)

4*10-3, 10-5, 6*10-8 (7)

5*10-2, 10-2, 5*10-

3, 10-3, 10-4, 10-5,

10-6

5*10-2, 10-2, 5*10-

3, 10-3, 10-4, 10-5,

10-6

Residual BER

Yes/No/- (6)Yes/No/- (6)Yes/No/- (6)Yes/No/- (6) Delivery of erroneous SDUs

(5)(5)SDU format information

<=1 500 or 1 502

(4)

<=1 500 or 1 502

(4)

<=1 500 or 1 502

(4)

<=1 500 or 1 502

(4)

Maximum SDU size (octets)

Yes/NoYes/NoYes/NoYes/NoDelivery order

<= 256 000 (2)<= 256 000 (2)<= 256 000 (2)<= 256 000 (2)Maximum bitrate (kbps)

Background

class

Interactive classStreaming classConversational

class

Traffic class

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PDP Context Activation Procedure

for Iu mode

GGSN

9. Activate PDP Context Accept

4. Create PDP Context Response

4. Create PDP Context Request

1. Activate PDP Context Request

SGSNRANMS

5. Radio Access Bearer Setup

C1

C2

6. Invoke Trace

8. Update PDP Context Response

8. Update PDP Context Request

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Network-Requested

PDP Context Activation Procedure

MS SGSN GGSN

3. PDU Notification Request

HLR

1. PDP PDU

2. Send Routeing Info for GPRS

2. Send Routeing Info for GPRS Ack

4. Request PDP Context Activation

5. PDP Context Activation procedure

3. PDU Notification Response

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supporting PS mode, Terminal

Equipment side

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Primitives and Parameters at

SMREG-SAP - MS side

WNP-MPR-qos 22

UMTS QoS Conceptual Models

IP Bearer

Layer

Access

Bearer

Layer

(eg. UMTS

Bearer)

Local

UE

SGSN

Scope of PDP Context

IP Bearer Service

RemoteAccess

Point

Gn/Gp

GGSN

Remote

Host

GGSNUE Remote

AP

Remote

Host

Backbone IPNetwork

WNP-MPR-qos 23

Local UE does not provide IP BS

Manager

Uplink Data

Downlink Data

QoS in UMTS controlled by

PDP context.

DS

DS

PDP Flow

PDP Flow

GGSNUE Remote

AP

Remote

Host

The UE controls

the QoS mechanisms

from the UE.

The UE may control

the QoS mechanisms

from received

information.

QoS on remote access

link controlled by

DS.


link controlled by

DS or other means.


PDP context selected by

TFT.

QoS in backbone network controlled

by DS. DS marking performed by

GGSN.



RUE, or remarking by RAP.

Application Layer (eg. SIP/SDP)


WNP-MPR-qos 24

Local UE supports DiffServ

Uplink Data

Downlink Data

DS

DS

GGSN Remote

AP

Remote

Host

The UE controls

the QoS mechanisms

from the UE.

The UE may control

the QoS mechanisms

from received

information.

The UE performs

DS edge functions.


link controlled by

DS.


link controlled by

DS or other means.


PDP context.

UE DS marking carried

transparently.



TFT.

Remote DS marking/GGSN

remarking carried

transparently.



UE (or remarking by GGSN).



RUE, or remarking by RAP.

PDP Flow

PDP Flow



UE

WNP-MPR-qos 25

Local UE supports RSVP signalling

and DiffServ

RSVP Signalling

RSVP Signalling



UE, or by GGSN based on PDP

context signalling.

RSVP signalling carried

transparently.


PDP context.

UE DS marking and RSVP

signalling carried

transparently.

Uplink Data

Downlink Data

DS

DS

GGSNUE Remote

AP

Remote

Host

The UE controls

the QoS mechanisms

from the UE.

The UE may control

the QoS mechanisms

from received

information.

The UE performs

DS edge functions

and RSVP



TFT.

Remote DS marking/GGSN

remarking and RSVP

signalling carried

transparently.



RUE (or remarking by RAP).

RSVP signalling carried

transparently.


link controlled by

either DS or RSVP.


link controlled by

either DS or RSVP.

PDP Flow

PDP Flow



WNP-MPR-qos 26

More about IPQoS over UMTS …

♦ An implementation example with results obtained in a testbed

» Manuel Ricardo, J. Dias, G. Carneiro, J. Ruela, "ARROWS QoS

Framework", IST ARROWS project, 31 August 2002

– http://paginas.fe.up.pt/~mricardo/doc/arrows/arrowsQosReport.pdf

WNP-MPR-qos 27

UMTS – Radio Resource

Management

♦ UMTS – WCDMA

♦ What are the causes of high packet delays?

» Low transmission information rate R

� high packet service time (transmission time) � long queues � high waiting time delay

» Packet retransmissions caused by packet loss

♦ What are the causes of packet loss?

» High BER

♦ What are the causes high BER?

WNP-MPR-qos 28

Uplink Capacity

– Ideal power control (every sinal received same power)

– N users transmitting at same data bitrate R bit/s

– Eb/Io decreases � BER increases, or

– Alternatively, for a given Eb/Io , BER,

• N, R � � need to be managed � admission control

1

1

)1( −=

−=

NNC

C

I

C

1

1

0−

===NR

W

I

C

R

W

WIR

CE

Ib

IEb

R

WN

0

1≅

N – number of users

C – power received form each user (W)

I – interference from other users (W)

Eb – energy received per information bit (J/bit)

I0 – Interference spectral density (J/Hz)

W –chip rate (chip/s)

R – information bitrate (bit/s)

∑=

N

i

iR1

WNP-MPR-qos 29

(from Holma & Toskala, 3rd

edition)

WNP-MPR-qos 30

Admission Control Based on

Throughput

<

WNP-MPR-qos 31

WLAN- QoS

WNP-MPR-qos 32

DCF - Distributed Coordination

Function

♦ Listen before-talk, CSMA/CA based

♦ Station transmist when medium is free for time greater than DIFS

♦ Random backoff used when medium is busy

AP

DIFS

S2

S1

SIFS

DATARTS

DIFS S2-bo

DATA

- Packet arrivalDATA

- Transmission of DATA DIFS - Time interval DIFS

CTS

SIFS

SIFS

ACK

WNP-MPR-qos 33

PCF - Point Coordination Function

♦ Contention-free frame transfer

♦ Point Coordinator (PC / AP) pools stations

♦ PIFS time used to enter Contention Free Period

Data+Poll

DATA+ACKBeacon

Data+Poll

ACK

CF-End

PIFS SIFS SIFS SIFS SIFS

SIFS

(no response)

PIFS

Contention

Period

PC

Contention Free Period CP

Data+Poll

SIFS

Time

WNP-MPR-qos 34

802.11e – QoS Support for WLAN

♦ Basic elements for QoS

» Traffic Differentiation

– 4 Access Categories, 8 Traffic Classes

» Concept of Transmission Opportunity (TXOP)

– Transmission of multiple frames

♦ New Contention-based channel access

» Enhanced Distributed Channel Access (EDCA)

♦ New Contention-free channel access

» HCF Controlled Channel Access (HCCA)

WNP-MPR-qos 35

PC

BSS (Basic Service Set) QBSS (Basic Service Set for QoS)

( Enhanced Station )

EDCA HCCADCF PCF

HCF- Hybrid Coordination

Function

STASTA

STA

STA

STA

HC

STASTA

STA

STA

STA

WNP-MPR-qos 36

HCF - Hybrid Coordination

Function

♦ During Contention Free Period

» Polls STAs and gives a station the permission to access channel

» Specifies time and maximum duration of each TXOP

♦ During Contention Period

» Controlled Contention

– STA may send traffic with different priorities

– STAs may also request resources

» HC can send polled TXOPs during CP

WNP-MPR-qos 37

EDCA

♦ 4 Access Categories (AC)

» AC_VO (Voice)

» AC_VI (Video)

» AC_BE (best-effort)

» AC_BK (background)

♦ Contention between ACs (and STAs)

♦ An Inter-frame Space (IFS) for each AC

Arbitration Inter frame Space (AIFS)

♦ Contention-Window (CW) depends on AC

♦ Mapping Priorities into AC

» IEEE 802.1D and IEEE 802.1Q

» See NSA slides

Virtual Collision

AC1 AC2 AC3 AC4

WNP-MPR-qos 38

ACK BackOff[AC0] + Frame

BackOff[AC1] + FrameBackOff[AC2] + Frame

AIFS[AC0]

AIFS[AC1]

AIFS[AC2]

BackOff[AC3] + Frame

AIFS[AC3]

Access Category AIFS

WNP-MPR-qos 39

MAC Parameters

• Prioritized Channel Access

implemented using MAC parameters per AC

10231023157CWmax

151573CWmin

7322AIFSN

AC_BK [3]AC_BE [2]AC_VIdeo [1]AC_VOice [0]

AIFS [AC] = AIFSN [AC] * aSlotTime + SIFS

If CW[AC] is less than CWmax[AC], CW[AC] shall be set to the value (CW[AC] + 1)*2 – 1.

WNP-MPR-qos 40

Transmission Opportunity (TXOP)

♦ TXOP: duration a STA has to transmit frame(s)

♦ When will a STA get a TXOP ?

» Winning a contention in EDCA during Contention Period

» Receiving a “polled TXOP” from HC

WNP-MPR-qos 41

Transmission Opportunity (TXOP)

(cont.)

♦ In TXOP, frames exchange sequences are separated by SIFS

WNP-MPR-qos 42

HCF Controlled Channel Access

(HCCA)

♦ Procedure similar to PCF

♦ Hybrid Coordinator (HC)

» Controls the iteration of CFP and CP

– By using beacon, CF-End frame and NAV Mechanism (similar to PCF)

» Use polling scheme to assign TXOP to STA

– Issue CF-poll frame to poll STA

– Polling can be issued in both CFP & CP

WNP-MPR-qos 43

Resources Managed in WLAN

♦ Resources are the time slots

» Used to transmit bits according to the modulations/codes used

♦ WLAN enables to send differentiated traffic

» By giving priority to real type traffic

♦ WLAN enables a flow to get a bit rate /delay

» By using polling

♦ What needs to be managed by the HC?

» The time slots available

» Who uses them and when

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