Quality of Service (QoS) in 3GPP

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Quality of Service (QoS) in 3GPP
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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

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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

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• 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

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• 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

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UMTS QoS Architecture
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• 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

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• 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

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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

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UMTS QoS management in control plane
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Control Plane

• Four major functional blocks in control plane
• Bearer Service Manager
• ??
• ??????????????,??,????????QoS????
• ??BS manager??????????????(component
  managers)????,????????(component
  managers)??????????,??,UMTS, radio, Iu, and CN BS
  manager
• ???BS manager??QoS???????????
• ???QoS?????,??BS manager????admission control
  entity??????????????????????????????

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• ??
• UMTS Bearer Service (BS) Manager
• Radio Access Bearer (RAB) Manager
• Local Bearer Service (BS) Manager
• Radio Bearer Service (BS) Manager

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• Translation Function
• ??????????????,????????????BS management,?????????
  ????????

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• Admission/Capability Control
• ???????????????????,???????????????,??????????????
  ?
• ?CN EDGE??admission control model?????????????PDP
  context?QoS???????????????

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• Subscription Control
• ?CN EDGE?BS manager???????,??????????QoS??????

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• 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

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• 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

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• 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

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UMTS QoS management in user plane
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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

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• Four major components
• Classifier
• ?????QoS??????????????
• ??,??DiffServ (Differentiated Services)?DSCP
  (Differentiated Service Code Point)?TCP port
  number????????????
• Classifier?????MT?Gateway?,???????????local
  bearer service?external bearer service???

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• Conditioner
• ?????????,???????????,????????????QoS??,??????????
  ????
• conditioner????(traffic shaping)?????(traffic
  policing)???????
• Mapper
• ??QoS??????????????????QoS???????
• marks data in order to receive the intended QoS

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• Resource manager
• responsible for managing and distributing
  resources according to the QoS requirements
• include scheduling, bandwidth management, and
  power control for the radio bearer

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• 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

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• 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

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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

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• 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

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UMTS QoS Classes
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4. QoS Attributes (QoS Pro?le)
Bearer services discussed for QoS attributes
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QoS attributes in UMTS bearer service
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• 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

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• 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

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• 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

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Values of UMTS bearer service attributes
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QoS attributes in RAB (radio access bearer)
service
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Values of RAB (radio access bearer) service
attributes
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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

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Control plane for end-to-end IP QoS management
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• 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)

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• 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

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• 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

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• 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

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• PEP (Policy Enforcement Point) function defined
  in IP policy framework
• optional for UE
• mandatory for GGSN

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Capability of IP BS managers in UE and GGSN
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• P-CSCF
• a mobiles 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)

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• 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

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• 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.

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• 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

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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

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Typical locations of RRM algorithms in a WCDMA
network
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• 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

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• 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

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• 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

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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

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• 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

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• 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

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• 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