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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 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. Ruelas slides
NAS_QoS_1.pdf, NAS_QoS_2.pdfNAS_QoS_1.pdf, NAS_QoS_2.pdf
In this lecture we will recall 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 users point of view
level of satisfaction experienced by the user of an application whose
traffic is delivered through a network. Depends on
Users subjective evaluation and expectations
Terminal capabilities
Performance of networks Performance of networks
From a network point of view
ability of providing differentiated treatment to
traffic flows or traffic classes
provide them with different levels of delivery guarantees
bandwidth, delay, loss
network behaviour characterizable by a set of performance parameters
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QoS principles
The provisioning of QoS requires
cooperation of various communications layers
cooperation of network elements in the end-to-end chain
QoS requirements of users/applications 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 offered traffic and QoS parameters
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QoS
QoS is an end-to-end problem, handled at several communication layers
Transport
Application
Application app. control
Application node
Application app. control
Application control (e.g. SIP)
App. node-backbone
control plane interface
Application node
Physical
Network
Transport
Data link
Mo
bil
ity
Sec
uri
ty
Mu
ltic
ast
Qu
ali
ty o
f S
ervi
ce
IP layer
IP user plane IP control plane
IP layer
IP user plane IP control plane
IP IP
Control
IP IP
Control
App. node-backbone
user plane (IP) interface
IP Backbone
Inter-domain interface
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
network
management
Control plane QoS mapping
Admission control
QoS routing
Resource reservation/allocation
Management plane Resource provisioning
Policy management
packet switch
(router, switch)
Traffic source/
previous network element
feed-back based,
end-to-end (TCO, RTP+RTCP)
inter-network element
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IP QoS Models
Important Please review NSA slides on QoS
NAS_QoS_2.pdf : pages 37 to 104
2 service models IntServ - oriented towards the support of QoS per flow
DiffServ - oriented towards the provisioning of QoS to traffic classes DiffServ - oriented towards the provisioning of QoS to traffic classes
Integrated Services (IntServ) model Resource ReSerVation Protocol
(RSVP)
TSpec, FlowSpec
Controlled load
Guaranteed service (maximum delay)
Differentiated Services (DiffServ) model DS field
Per-Hop Behaviours (PHB)
Assured Forwarding (AF)
Expedited Forwarding (EF)
Bandwidth broker
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IntServ - RSVP
Resource
ReSerVation Protocol (RSVP)
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IntServ Tspec, FlowSpec
The FlowSpec - information that characterizes the traffic to submit to the network (TSpec)
the service requested from the network (RSpec)
TSpec includes the following parameters p peak rate p peak rate
r token bucket rate
b bucket size
M maximum datagram size
m minimum policed unit
RSpec is specified only for the Guaranteed service and includes R service rate (must be > r)
S delay slack (acceptable delay in addition to the delay obtained with R
WNP-MPR-qos 11
IntServ QoS Services
Guaranteed Service
hard guarantees provided to real-time applications
Guaranteed bandwidth
Bound on end-to-end delay
No losses of conforming packets on the routers
Resources reserved per flow, based on a Flowspec (TSpec and RSpec) Resources reserved per flow, based on a Flowspec (TSpec and RSpec)
Controlled-Load Service
emulates the service provided by a moderately loaded best-effort network
only qualitative guarantees
Very high percentage of transmitted packets are successfully delivered
Delay of the majority of the packets
will not greatly exceed the minimum delay of a packet
The sender does not specify RSpec
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0 1 2 3 4 5 6 7 +---+---+---+---+---+---+---+---+ | DSCP | CU | +---+---+---+---+---+---+---+---+ DSCP: differentiated services codepointCU: currently unused
DiffServ DSCP field
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Diff Serv PHB, AF, EF
Per-Hop Behaviours (PHB)
Packets marked with the same DSCP, receive similar treatment
3 PHBs defined
Best effort Best effort
Assured Forwarding (AF)
Service provides qualitative guarantees, based on priorities
Service characterized by a high probability of packet delivery
may be used to implement the Olympic service (gold, silver and bronze classes)
Expedited Forwarding (EF)
aimed at building services characterized by
low packet loss ratio, low latency and low jitter
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DiffServ - Bandwidth broker
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QoS in UMTSQoS in UMTS
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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 Bearer Service 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
WNP-MPR-qos 17
QoS management functions,
UMTS bearer service, user plane
Class if.
Class
MT Gateway CN EDGE RAN TE Ext. Netw.
Resource Manager
Mapper
Cond.
Resource Manager
Resource Manager
Mapper
Resource Manager
Mapper
Resource Manager
Resource Manager
Cond.
Class if.
Cond.
BB netw ork service RAN Access network service RAN phys. BS
data f low with indication of direction
Local BS External BS
WNP-MPR-qos 18
Class
Classifies and marks packet
At the entry of network (downlink GGSN, uplink terminal)
Cond Traffic conditioner
Enforces compliance of flow with QoS attributes
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
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
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UMTS QoS Classes
Traffic class Conversational class Streaming class Interactive class Background
Fundamental characteristics
Preserve time relation (variation) between information entities of the stream
Conversational pattern (stringent and low
Preserve time relation (variation) between information entities of the stream
Request-response pattern
Preserve payload content
Destination is not expecting the data within a certain time
Preserve payload content(stringent and low
delay)payload content
Example of the application
voice streaming video Web browsing Background download of emails
WNP-MPR-qos 20
UMTS Bearer Service Attributes Examples
Traffic class ('conversational', 'streaming', 'interactive', 'background')
Maximum bitrate (kbit/s) compliance enforced by
token-bucket (Maximum-bitrate , Maximum-SDU-size)
used to reserve codes in WCDMA radio interface - downlink
Guaranteed bitrate (kbit/s) traffic compliance enforced by 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
b
TBC
OK OK Non-compliant
L1
WNP-MPR-qos 22
QoS attributes versus traffic classes
Traffic classConversational
classStreaming class Interactive class Background class
Maximum bit rate X X X X
Delivery order X X X X
Maximum SDU size X X X X
SDU format information
X X
SDU error ratio X X X X
Residual bit error ratio
X X X Xratio
Delivery of erroneous SDUs
X X X X
Transfer delay X X
Guaranteed bit rate X X
Traffic handling priority
X
Allocation/ Retention priority
X X X X
Source statistics descriptor
X X
Signalling Indication X
WNP-MPR-qos 23
UMTS Bearer Service Attributes (Rel. 7!)
Traffic class Conversational
class
Streaming class Interactive class Background
class
Maximum bitrate (kbps)
WNP-MPR-qos 24
PDP Context Activation Procedure for Iu mode
GGSN
4. Create PDP Context Request
1. Activate PDP Context Request
SGSNRANMS
C1
9. Activate PDP Context Accept
4. Create PDP Context Response
5. Radio Access Bearer Setup
C2
6. Invoke Trace
8. Update PDP Context Response
8. Update PDP Context Request
WNP-MPR-qos 25
Network-Requested
PDP Context Activation Procedure
MS SGSN GGSNHLR
1. PDP PDU
2. Send Routeing Info for GPRS
2. Send Routeing Info for GPRS Ack
3. PDU Notification Request
2. Send Routeing Info for GPRS Ack
4. Request PDP Context Activation
5. PDP Context Activation procedure
3. PDU Notification Response
WNP-MPR-qos 26
Protocol architecture of NAS supporting PS
mode, Terminal Equipment side
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Primitives and Parameters at
SMREG-SAP - MS side
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UMTS QoS Conceptual Models
IP BearerLocal IP Bearer Service Remote
GGSNUE Remote
AP
Remote
Host
IP BearerLayer
Access
Bearer
Layer
(eg. UMTS
Bearer)
Local
UE
SGSN
Scope of PDP Context
IP Bearer Service
Remote
Access
Point
Gn/Gp
GGSN
Remote
Host
Backbone IPNetwork
WNP-MPR-qos 29
Local UE does not support IP QoS
Uplink Data
QoS in UMTS controlled by
PDP context.
DS
PDP Flow
The UE controls
the QoS mechanisms
from the UE.
QoS on remote access
link controlled by
DS.
QoS in backbone network controlled
by DS. DS marking performed by
GGSN.
Application Layer (eg. SIP/SDP)
Downlink DataDS
PDP Flow
GGSNUE Remote
AP
Remote
Host
The UE may control
the QoS mechanisms
from received
information.
QoS on remote access
link controlled by
DS or other means.
QoS in UMTS controlled by
PDP context selected by
TFT.
QoS in backbone network controlled
by DS. DS marking performed by
RUE, or remarking by RAP.
Application Layer (eg. SIP/SDP)
WNP-MPR-qos 30
Local UE supports DiffServ (DS)
Uplink DataDS
The UE controls
the QoS mechanisms
from the UE.
QoS on remote access
link controlled by
DS.
QoS in UMTS controlled by
PDP context.
UE DS marking carried
transparently.
QoS in backbone network controlled
by DS. DS marking performed by
UE (or remarking by GGSN).
PDP Flow
Application Layer (eg. SIP/SDP)
Downlink DataDS
GGSN Remote
AP
Remote
Host
The UE may control
the QoS mechanisms
from received
information.
The UE performs
DS edge functions.
QoS on remote access
link controlled by
DS or other means.
QoS in UMTS controlled by
PDP context selected by
TFT.
Remote DS marking/GGSN
remarking carried
transparently.
QoS in backbone network controlled
by DS. DS marking performed by
RUE, or remarking by RAP.
PDP Flow
PDP Flow
Application Layer (eg. SIP/SDP)
UE
WNP-MPR-qos 31
Local UE supports RSVP signalling and DiffServ
RSVP Signalling
QoS in backbone network controlled
by DS. DS marking performed by
UE, or by GGSN based on PDP
context signalling.
RSVP signalling carried
transparently.
QoS in UMTS controlled by
PDP context.
UE DS marking and RSVP
signalling carried
transparently.
Uplink Data
DS
The UE controls
the QoS mechanisms
from the UE.
QoS on remote access
link controlled by
either DS or RSVP.
PDP Flow
Application Layer (eg. SIP/SDP)
RSVP Signalling
Downlink Data
DS
GGSNUE Remote
AP
Remote
Host
The UE may control
the QoS mechanisms
from received
information.
The UE performs
DS edge functions
and RSVP
QoS in UMTS controlled by
PDP context selected by
TFT.
Remote DS marking/GGSN
remarking and RSVP
signalling carried
transparently.
QoS in backbone network controlled
by DS. DS marking performed by
RUE (or remarking by RAP).
RSVP signalling carried
transparently.
QoS on remote access
link controlled by
either DS or RSVP.
PDP Flow
PDP Flow
Application Layer (eg. SIP/SDP)
WNP-MPR-qos 32
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 33
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 Packet retransmissions caused by packet loss
What are the causes of packet loss?
High BER
What are the causes high BER?
WNP-MPR-qos 34
Uplink Capacity
Maximum Number ( N ) of users
Ideal power control (every sinal received same power)
N users transmitting at same data bitrate R bit/s
1
1
)1( =
=
NNC
C
I
C
C
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)
Eb/Io decreases BER increases, or
Alternatively, for a given Eb/Io , BER,
N, R need to be managed admission control
1
1
0
===NR
W
I
C
R
W
WI
RC
E
Ib
IEbR
WN
0
1
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 35
Load Factor, Uplink
(from Holma & Toskala, 3rd edition)
WNP-MPR-qos 36
Load Factor, Uplink
(from Holma & Toskala, 3rd edition)
WNP-MPR-qos 37
Admission Control Based on Throughput
WNP-MPR-qos 38
WLAN- QoSWLAN- QoS
WNP-MPR-qos 39
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 40
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 41
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 42
PC
HCF- Hybrid Coordination Function
STA
STA
STA
HC
STA
STA
STA
PC
BSS (Basic Service Set) QBSS (Basic Service Set for QoS)
( Enhanced Station )
EDCA HCCADCF PCF
STASTA
STASTA
WNP-MPR-qos 43
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 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 44
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 ACArbitration Inter frame Space (AIFS)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 45
AIFS[AC1]
AIFS[AC2]
AIFS[AC3]
Access Category AIFS
ACK BackOff[AC0] + Frame
BackOff[AC1] + FrameBackOff[AC2] + Frame
AIFS[AC0]
BackOff[AC3] + Frame
WNP-MPR-qos 46
MAC Parameters
Prioritized Channel Access
implemented using MAC parameters per AC
AC_VOice [0] AC_VIdeo [1] AC_BE [2] AC_BK [3]
AIFSN 2 2 3 7
CWmin 3 7 15 15
CWmax 7 15 1023 1023
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 47
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 48
Transmission Opportunity (TXOP) (cont.)
In TXOP, frames exchange sequences are separated by SIFS
WNP-MPR-qos 49
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 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 50
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 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