quality of service (qos) in 3gpp. 1.umts qos architecture 2.umts qos management 3.umts qos classes...
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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
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