Transcript Quality of Service (QoS) in 3GPP

Quality of Service (QoS) in 3GPP
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UMTS QoS Architecture
UMTS QoS Management
UMTS QoS Classes
QoS Attributes (QoS Profile)
Management of End-to-End IP QoS
1. UMTS QoS Architecture
 3GPP TS 23.107 defines 3GPP QoS architecture with
the following major QoS principles
 QoS has to be provided end-to-end
 the QoS attributes are needed to support asymmetric bearers
 the number of user-defined and controlled attributes should
be as small as possible
 the derivation and definition of QoS attributes from the
application requirements have to be simple
 it should be able to provide different levels of QoS using
UMTS-specific control mechanisms that are not related to
QoS mechanisms in the external networks
 the QoS mechanisms have to allow efficient use of
radio capacity and efficient resource utilization
 it should allow independent evolution of core and
access networks
 the UMTS network should be evolved with
minimized impact on the evolution of transport
technologies in the wireline networks
 the UMTS QoS control mechanisms shall be able to
efficiently interwork with current QoS schemes
 the overhead and additional complexity caused by
the QoS scheme should be kept reasonably low, so
as the amount of state information transmitted and
stored in the network
 the QoS behavior should be dynamic, i.e., it should
be possible to modify QoS attributes during an
active session
UMTS QoS Architecture
 QoS functions are divided into different layers
 Each bearer service provides its QoS services by utilizing
the services furnished by lower layer(s)
 End-to-end QoS
 Terminal Equipment (TE) to Mobile Terminal (MT)
Local Bearer Service
 UMTS Bearer Service
 External Bearer Service
 UMTS Bearer Service
 Radio Access Bearer Service
 provides confidential transport of signaling and user data
between MT and CN Iu Edge Node
 Core Network (CN) Bearer Service
 connects the UMTS CN Iu Edge Node with the CN
Gateway to the external network
 should efficiently control and utilize the backbone
network in order to provide the contracted UMTS Bearer
Service
 the packet core network should support different
backbone bearer services for a variety of QoS
2. UMTS QoS Management
 Management of the UMTS Bearer Service includes
management functions in control plane and user plane
 Management functions
 seek to ensure the negotiated QoS between UMTS Bearer
Service and external services, including TE/MT Local Bearer
Service and External Bearer Service
 End-to-end QoS is achieved by
 translation and mapping of the QoS requirements and QoS
attributes between the UMTS Bearer Service and external
services
UMTS QoS management in control plane
Control Plane
 Four major functional blocks in control plane
 Bearer Service Manager
 功用
 主要功能是協調控制信號以建立，修改，並且維持所要
求的QoS品質服務
 每個BS manager都是一個包含著多個物件管理者
(component managers)的組合體，而這些物件管理者
(component managers)各自管理自己所屬功能，例如，
UMTS, radio, Iu, and CN BS manager
 另一些BS manager負責QoS品質服務參數數值的轉換
 在提供QoS品質服務前，每個BS manager可能會與
admission control entity相互溝通。溝通的目的在於判斷
使用者所要求的頻寬資源是否可獲得
 分類
 UMTS Bearer Service (BS) Manager
 Radio Access Bearer (RAB) Manager
 Local Bearer Service (BS) Manager
 Radio Bearer Service (BS) Manager
 Translation Function
 將外部的信號轉換成內部的信號，並且將它們轉
送至下一層的BS management，其中還包含了傳
輸相關參數屬性的轉換
 Admission/Capability Control
 維持有關頻寬資源的獲得及配置的相關資訊，並
在當使用者提出頻寬保留要求時，決定是否給予
頻寬資源的保留配置
 在CN EDGE中的admission control model主要是負
責對使用者所提出的PDP context和QoS參數值做
最後的接受或拒絕的決定
 Subscription Control
 讓CN EDGE的BS manager透過它來做確認，以決
定是否有使用網路QoS服務的使用權
 To establish or modify a UMTS bearer service
 the Translation Functions in the MT and the
Gateway signal / negotiate with external bearer
services
 the service primitives and QoS attributes are
converted between the UMTS Bearer Service and
the external bearer services
 the Translation Functions further signals/negotiates
with the UMTS BS Managers in MT, CN Edge, and
Gateway
 Each UMTS BS Manager consults with its associated
Admission/Capability Control to decide whether the
requested services and desired resources are available
and can be granted
 the UMTS BS Manager in CN Edge also consults with the
Subscription Control to check the administrative privileges
for the requested services
 once all checks are positive, a UMTS bearer service could be
established/modified
 each UMTS BS Manager requests services from lower layers
and translates its service attributes to lower layers
 example
 the UMTS BS Manager in MT requests services from the
Local BS Manager and the Radio BS Manager
 the UMTS BS Manager in Gateway asks services from the
CN BS Manager and the External BS Manager
 in addition to the Iu BS manager and the CN Manager in the
CN Edge, the UMTS BS Manager in CN Edge translates
QoS attributes and requests services from the RAB Manager
in UTRAN as well
 the RAB Manager in UTRAN verifies with its associated
Admission/ Capability Control to determine whether the
requested services are supported and the desired resources
are available
UMTS QoS management in user plane
User Plane
 User plane
 ensures that the user data transmitted in UMTS
Bearer Service conforms to the traffic
characteristics and service attributes defined by the
control plane
 Four major components
 Classifier
 依據使用者QoS品質服務需求來分類並指派封包
 例如，依據DiffServ (Differentiated Services)的DSCP
(Differentiated Service Code Point)或TCP port number
來給予不同等級的品質服務
 Classifier分別存在於MT及Gateway中，各自負責指
派並分配來自local bearer service和external bearer
service的封包
 Conditioner
 為一個監督者的角色，隨時監看資料傳輸的狀態，
檢查資料是否符合所給予的QoS等級，若不符合則
丟棄或重新給予標記
 conditioner藉由塑型(traffic shaping)或政策管理
(traffic policing)來達成目標控制
 Mapper
 依據QoS品質服務的要求給予每個資料單元特殊的
QoS品質服務的標記
 marks data in order to receive the intended QoS
 Resource manager
 responsible for managing and distributing
resources according to the QoS requirements
 include scheduling, bandwidth management, and
power control for the radio bearer
 Before entering the domain of UMTS Bearer Service,
traffic is classified and conditioned in the MT and the
Gateway
 Based on packet header or traffic characteristics, data are
classified into different UMTS bearer services
 They are then conditioned to ensure conformance with the
negotiated QoS
 For downlink traffic to MT, there is also a traffic
conditioner in UTRAN
 The conditioner in the Gateway is for conditioning traffic
that enters the core network from external networks
 The output traffic from the conditioner in the gateway may
not conform with the QoS attributes specified for downlink
traffic in the UTRAN
 packets may be shaped or dropped
 shaping: the process of delaying packets within a traffic
stream to cause it to conform to some defined traffic profile
 dropping: the process of discarding packets based on
specified rules
3. UMTS QoS Classes
 3GPP define two major classes (according to delay
sensitivity)
 real time
 conversational class
 streaming class
 non-real time
 interactive class
 background class
 real-time traffic is more delay sensitive than is non-realtime traffic
 conversational class is most sensitive to delay,
followed by streaming class, interactive class, and
then background class
UMTS QoS Classes
4. QoS Attributes (QoS Profile)
Bearer services discussed for QoS attributes
QoS attributes in UMTS bearer service
 Attributes
 delivery order
 whether the SDU (Service Data Unit) should be delivered in
order
 maximum SDU size
 the maximum allowable size of SDUs
 SDU format information
 the possible actual sizes of SDUs, which might be useful for
RLC operation in UTRAN
 SDU error ratio
 the fraction of lost or detected erroneous SDUs
 residual bit error ratio (BER)
 the undetected bit error ratio of a delivered SDU
 delivery of erroneous SDUs
 whether the detected erroneous SDU should be
transmitted
 transfer delay
 the maximum delay of 95th percentile of the delay
distribution of all delivered SDUs
 traffic handling priority
 the priority for SDUs
 allocation/ retention priority
 the priority for allocation and retention of the UMTS
bearer
 source statistics descriptor
 shows the traffic characteristics of SDUs
 studies have shown that speech holds a discontinuous
behavior, in which there are talking and silent periods
 by specifying the source characteristics, it helps the
system in making a decision for admission control to
achieve statistical multiplex gain
Values of UMTS bearer service attributes
QoS attributes in RAB (radio access bearer) service
Values of RAB (radio access bearer) service attributes
5. Management of End-to-End IP QoS
 Assuming the external network is based on IP,
this section discusses the management and
interaction between the UMTS Bearer Service
and the External Bearer Service to provide endto-end IP QoS
Control plane for end-to-end IP QoS management
 Two extra components in the control plane of
the management function to provide end-to-end
IP QoS
 IP BS (Bearer Service) Manager
 P-CSCF (Proxy Call State Control Function)
 IP BS Manager
 controls the external IP bearer service
 utilizes standard IP mechanisms to manage IP
bearer services
 to interact with UMTS Bearer Service, the IP BS
Manager leverages the Translation Function to map
the mechanisms and parameters used within the IP
bearer service to those used within the UMTS
bearer service
 Two IP BS Managers
 one in the UE (User Equipment)
 one in the Gateway (the Gateway might be a
GGSN)
 the IP BS Managers in the UE and the GGSN could
communicate with each other using relevant
signaling protocols
 IP BS Manager may support Int-Serv/RSVP or
Diff-Serv edge function
 Diff-Serv edge function
 required for the IP BS Manager in GGSN
 optional for the IP BS Manager in UE
 Int-Serv/RSVP
 optional for both UE and GGSN
 PEP (Policy Enforcement Point) function
defined in IP policy framework
 optional for UE
 mandatory for GGSN
Capability of IP BS managers in UE and GGSN
 P-CSCF
 a mobile’s first contact point for IP multimedia sessions
 essentially is a local SIP server
 includes a Policy Control Function (PCF)
 PCF
 coordinates the applications with the resource management in
IP layer
 a logical entity for policy decision, which conforms to the
policy framework defined by IETF
 effectively is a PDP (Policy Decision Point), whereas the IP
BS Manager in GGSN is a PEP (Policy Enforcement Point)
 Go interface
 the interface between PCF and GGSN
 supports the transfer of information and policy
decisions between PCF and IP BS Manager in the
GGSN
 QoS resource authorization for IP bearer service
 SIP adopted by 3GPP as the signaling protocol for
packet domain
 the QoS authorization process is triggered when
receiving a SIP message
 the payload of a SIP INVITE usually contains SDP
(Session Description Protocol), which specifies the type
of media, codec, sampling rate, etc.
 PCF identifies the connection information such as media
and bandwidth requirements for a downlink connection
 PCF then relays the SDP message to the destining UE
 once the SDP from destining UE is received, the PCF
identifies the uplink connection information
 it also authorizes the requested QoS resources and
enforces the IP bearer policy
 the SDP message is then forwarded to the originating
UE
Radio Resource Management (RRM)
 Radio Resource Management (RRM)
algorithms are responsible for efficient
utilization of the air interface resources
 RRM is needed to guarantee Quality of Service
(QoS), to maintain the planned coverage area,
and to offer high capacity
Typical locations of RRM algorithms in a WCDMA network
 RRM functions
 connection based functions
 Handover Control (HC)
 handles and makes the handover decisions
 controls the active set of Base Stations of MS
 Power Control (PC)
 maintains radio link quality
 minimize and control the power used in radio
interface, thus maximizing the call capacity
 network based functions
 Admission Control (AC)
 handles all new incoming traffic
 check whether new connection can be admitted to
the system and generates parameters for it
 Load Control (LC)
 manages situation when system load exceeds the
threshold and some counter measures have to be
taken to get system back to a feasible load
 Packet Scheduler (PS)
 handles all non real time traffic, (packet data
users)
 decides when a packet transmission is initiated
and the bit rate to be used
Connection Based Functions
 Power control
 prevent excessive
interference and near-far
effect
 open-loop power control
 rough estimation of
path loss from
receiving signal
 initial power setting,
or when no feedback
channel is exist
Outer Loop Power Control
If quality < target,
increases SIRTARGET
Fast Power Control
If SIR < SIRTARGET,
send “power up”
command to MS
 fast close-loop power control
 feedback loop with 1.5kHz cycle to adjust uplink /
downlink power to its minimum
 even faster than the speed of Rayleigh fading for
moderate mobile speeds
 outer loop power control
 adjust the target SIR setpoint in base station
according to the target BER
 commanded by RNC
 Handover
 softer handover
 a MS is in the overlapping
coverage of 2 sectors of a
base station
 concurrent communication
via 2 air interface channels
 2 channels are maximally
combined with rake
receiver
 soft handover
 a MS is in the overlapping
coverage of 2 different base
stations
 concurrent communication via
2 air interface channels
 downlink: maximal combining
with rake receiver
 uplink: routed to RNC for
selection combining, according
to a frame reliability indicator
by the base station
Network Based Functions
RT / NRT : Real-time / Non-Real-time
RAB : Radio Access Bearer
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