Quality of Service (QoS) in 3GPP

1. UMTS QoS Architecture

2. UMTS QoS Management

3. UMTS QoS Classes

4. QoS Attributes (QoS Profile)

5. 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-real-time 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 end- to-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

Fast Power ControlIf SIR < SIRTARGET, send “power up” command to MS

Outer Loop Power ControlIf quality < target, increases SIRTARGET

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

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Network Based Functions

RT / NRT : Real-time / Non-Real-time RAB : Radio Access Bearer