UMTS Protocols 3

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OutlinesPDCP Protocol. 1)PDCP Functions. 2)PDCP Entities.BMC Protocol. 1)BMC Functions. 2)Cell Broadcast Center.RRC Protocol. 1)RRC Entities. 2)RRC Functions.

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Radio Interface Protocol Architecture.

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Packet Data Convergence Protocol PDCP is located above RLC of the user plane.PDCP is used only for services from PS domain.PDCP protocol entities are located in the UE and the RNC.PDCP PDUs are (NAS)non access stratum because they

are exchanged between the UE and the core network, and do not terminate in the UTRAN.

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PDCP Functions(1)Transmitting and receiving of network layer data units :As the most common protocols for data services are IPv4

and IPv6 at the network layer and TCP and User Datagram Protocol (UDP) at the transport layer.

So UTRAN needs to interwork with these protocols without requiring any changes to its RLC and MAC layers.

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IPv4,IPv6,UDP , TCP UTRAN

PDCP[Adapting]

PDCP Functions(2)IP Header compression and decompression: Because IP was originally designed for fixed networks where

the overhead is not a big problem. However, in radio networks like UMTS, radio resources are scarce and IP header compression is crucial to increase channel efficiency, especially if small packets are sent frequently.

Transmission Efficiency depends on size of packet header compared to length of the entire packet.

EX : For IPv6 where header is 48 octets long and if the user data in the packet is also 48 octets then the transmission efficiency will be 50 % .

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Header Compression AlgorithmsBased on the Fact Many of Header fields remain the same during the life of

the call and do not change from one packet to another . Ex: IP,UDP,TCP Header : 1- Source address. 2- Destination address. 3- Port number .Larger Headers will lead to Higher channel BW , decrease

transmission efficiency and increase delay.7

DO Not Change

TCP/IP Header Compression: State Of Art

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A1A1 A1A1B C D

Compressor

A1 B C D

De-Compressor

A1A1 A1A1B C D

PDCP EntitiesThe PDCP entities are located in the PDCP sublayer.Every PDCP entity uses zero, one or several header

compression algorithm types with certain parameters.Several PDCP entities may use the same algorithm type. The algorithm types and their parameters are negotiated

by RRC and indicated to PDCP through the PDCP Control Service Access Point (PDCP–C–SAP).

Every PDCP–SAP uses exactly one PDCP entity.

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PDCP Entities

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Radio Interface Protocol Architecture.

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Broadcast Multicast ControlBMS exists only in the user plane .The only service utilizing this protocol is SMS CB .At the UTRAN side, the BMC sublayer shall consist of one

BMC protocol entity per cell.Each BMC entity requires a single CTCH, which is

provided by the MAC sublayer through the RLC sublayer. The BMC requests the Unacknowledged Mode service of

the RLC.BMC doesn’t have special logical structure.

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BMC Model

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SMS CBPoint-to-area message : is targeted to a geographical

area CB : Delivery of messages to multiple users in a specific

area .SMS CBs : are directed to radio cells rather than to a

specific terminal. Not all operators provide CB service in their networks.Not all handsets have CB capability.EX : Weather Reports , Location based News and

Emergency alerts. 14

Cell Broadcast Centre (CBC)Node which is a source of SMS CB is connected to RNC

networks via interface CBC-RNC.

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CBC RNC Node-BSMS CB Message

SMS CB Message

Cell List

Requested Repetion

Rate

Number of

times

BMC FunctionsStorage of Cell Broadcast Messages.Traffic volume monitoring and radio resource request for

CBS.Scheduling of BMC messages.Transmission of BMC messages to UE.Delivery of Cell Broadcast messages to upper layer.Note: when sending SMS CB messages to a cell for the

first time ,appropriate capacity has to be allocated in the cell and may vary over time to allow efficient use of radio resources .

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Radio Interface Protocol Architecture.

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Radio Resource Control(RRC)The major part of the control signaling between UE &

UTRAN through RRC messages.RRC messages : 1) Carry all parameters to set-up , modify and release layer 1 , layer 2 protocol entities . 2) Carry all higher layer signaling (NAS) e.g. MM (Mobility Management) , CM (Connection

Management) , SM (Session Management) . 3) Control the mobility of UE in the connected mode ( measurements , Handovers , Cell Updated ) .

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RRC-Interaction with lower layers

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RRC Layer Model

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RRC EntitiesDCFE : Dedicated Control Function Entity.PNFE : Paging and Notification control Function

Entity.BCFE : Broadcast Control Function Entity.RFE : Routing Function Entity.

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DCFEHandles all functions and signaling related to one UE.There is one DCFE entity for each UE having an RRC

connection with this RNC.DCFE messages use mostly AM-RLC through AM-SAP but

some messages are sent using UM-SAP ( RRC Connection Release) and using TR-SAP (Cell Update).

Used to deliver the RRC services which are requested at the Dc-SAP .

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PNFEHandles paging of idle-mode UE(s).There is at least one PNFE in the RNC for each cell

controlled by this RNC.The PNFE uses the PCCH logical channel via. TR-SAP and

may also use UM-SAP.PNFE in RNC, when receiving a paging message from an Iu

interface, needs to check with the DCFE whether or not this UE already has an RRC connection if it does, then the paging message is sent using the existing RRC connection.

Deliver RRC Services at Nt-SAP.23

BCFEHandles the system information broadcast .There is at least one BCFE for each cell in the RNC.The BCFE uses BCCH logical channel via. TR-SAP and also

via. UM-SAP .Used to deliver the RRC services which are requested at

the Gc-SAP .

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RFERouting of higher layer (NAS) messages to different MM

entities .Each higher layer message is piggybacked onto the RRC

Direct Transfer Message.RRC Direct Transfer Message types : 1- Initial Direct Messages. 2- Uplink Direct Messages. 3- Downlink Direct Messages.

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RRC Functions (1)Broadcast of system information (NAS – access stratum).Paging .Initial cell selection and re-selection in Idle-Mode.Establishment , Maintenance and Release of RRC

connection .Notification .Radio Access Bearers Establishment and Release .RRC connection mobility functions.

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RRC Functions (2)Cell Update .URA Updating .Control of security functions.Integrity protection of signaling .UE measurement Reporting.UE measurement Control.CBS related Functions .

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Broadcast of system information

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Broadcast of system informationSystem Information originates from the CN (RNC -Node Bs ).System Information message contains system information

blocks (SIBs) .Each group of SIBs carry the system information of the same

type .One System Information message can carry several SIBs or

part of one SIB -> Depending on the size of SIB.Through Transmitting, SIBs will fit the size of BCH/FACH

transport block and if padding is required ,it is inserted by RLC.R99 ,there is one MIB and two scheduling blocks and 17 SIBs.EX : Location Service Area related to some specific cells.

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System Information Classes Information giving unique identification of the current

network, location area, UTRAN registration area and cell.Information used for candidate cell measurements for

handover and cell selection procedures.Information describing the current control channel structure.Information defining different options supported within the

cell.Protocol information.

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System Information

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BCCH

BCH/FACH

System Information Message

Paging

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PagingRRC layer can broadcast paging information on the PCCH

from Network to selected UEs.Reasons of paging : 1- Session set-up : request to start paging comes from

CN via Iu interface . 2- To change UE state from Cell_PCH to Cell_FACH. 3- To indicate a change in the system information .EX : BCCH Modification Information that indicates the

modification of system information on BCCH.

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Notification

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Notification This procedure is used for broadcast of notification

information to selected UEs in a cell. Only UEs that listen to the correct notification group can

be reached by this procedure. The initiative to send a NOTIFICATION REQUEST can

come from both the access stratum and the non-access stratum.

NOTIFICATION REQUEST can be sent to either one or many UEs at the same time.

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RRC Connection EstablishmentThis procedure is initiated from the UE side to establish

an RRC connection, as a result of either: (1) A request from the non-access stratum to establish the

first signaling connection for the UE. (2) A received paging request.

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RRC Connection Establishment

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RRC Connection EstablishmentThe RRC connection establishment is initiated by the UE .UE leaves the idle mode and sends an RRC CONNECTION REQUEST message on the uplink CCCH.The UTRAN makes an assignment of radio resources and the Radio

Network Temporary Identity (RNTI) to be used by the UE.The UTRAN sends an RRC CONNECTION SETUP message to the UE

on the downlink CCCH. The UE configures the layer 2 and layer 1 processing for the DCCH

using the radio resource parameters. The procedureSuccessfully ends when the layer 2 signaling link is established on

the DCCH.

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RRC Connection Release

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RRC Connection ReleaseA normal RRC connection release procedure is initiated from

the UTRAN.RRC layer entity in the network issues an RRC CONNECTION

RELEASE message using unacknowledged mode on the DCCH.Upon reception of this message the UE-RRC sends an RRC

CONNECTION RELEASE COMPLETE message to UTRAN using acknowledged mode on the DCCH.

After receiving the RRC CONNECTION RELEASE COMPLETE message the network RRC layer releases L2 resources and the RRC entity dedicated to this UE goes to Idle Mode.

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RRC Connection Re-establishment

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RRC Connection Re-establishmentRRC connection re-establishment is needed, when a UE loses

radio connection due to e.g. radio link failure. After having selected a new cell, the UE RRC sends the NW RRC

an RRC CONNECTION REESTABLISHMENT REQUEST message. The NW RRC configures the NW and acknowledges the

connection re-establishment to the UE RRC with an RRC CONNECTION RE-ESTABLISHMENT message.

The UE RRC configures the UE L1 to activate the new radio link(s).

When the procedure is completed on the UE side, an RRC CONNECTION RE-ESTABLISHMENT COMPLETE message is sent.

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Radio Access Bearer Establishment

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Radio Access Bearer Establishment This procedure establishes a new radio access bearer. It include assignment of a physical channel(s) and change of the

used transport channel types / RRC state.A Radio Access Bearer Establishment is initiated when the RRC

layer in the network sends a RADIO ACCESS BEARER SETUP message to its peer entity.

This message contains L1, MAC and RLC parameters. RRC on the UE side then configures L1 and MAC and creates a

new RLC entity associated with the new radio access bearer. The UE then sends a RADIO ACCESS BEARER SETUP COMPLETE

message back to the network.

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Radio Access Bearer Reconfiguration

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Radio Access Bearer ReconfigurationThis procedure reconfigures parameters for a radio

access bearer or the signaling link to reflect a change in QoS.

It may include change of RLC parameters, change of multiplexing priority for DTCH/DCCH, change of DCH scheduling priority, change of TFS for DCH, change of TFCS, assignment or release of physical channel(s) and change of used transport channel types.

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URA Update

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URA UpdateThe URA update procedure is used by the UE to inform the

UTRAN that the UE has switched to a new URA. Normally the procedure is triggered after change of cell and

after the UE have read information broadcasted by UTRAN indicating change of URA.

The UE establishes a radio link to a cell in the new URA. After that the UE sends a URA UPDATE REQUEST message to the UTRAN.

Upon reception of the message the UTRAN registers the change of URA, and sends a URA UPDATE CONFIRM message to the UE. The URA UPDATE CONFIRM message may include a new RNTI.

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Cell Update

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Cell UpdateThe cell update procedure is used by the UE to inform the UTRAN

that the UE has switched to a new cell. The procedure is a forward handover procedure. Normally the procedure is triggered after change of cell and after

the UE has read information broadcasted by UTRAN.The UE abandons the radio link to the old cell and establishes a

radio link to the new cell. After that the UE sends a CELL UPDATE REQUEST message to the

UTRAN. Upon reception of the message the UTRAN registers the change of

cell, and sends a CELL UPDATE CONFIRM message to the UE.

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Control of Security FunctionUsed to start ciphering and integrity protection

between the UE and UTRAN and to trigger the change of the ciphering and integrity keys during the connection.

Two ciphering keys can be used simultaneously for one UE: PS domain services & CS domain services.

Ciphering is executed on the RLC layer for services using unacknowledged or acknowledged RLC and on the MAC layer for services using transparent RLC.

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Integrity Protection of Signaling

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Integrity Protection of SignalingRRC layer inserts integrity checksum : Message

Authentication Code (MAC-1) into most RRC PDUS.MAC-1 : is used by the receiving entity of RRC to verify

the origion & integrity of the messages .The receiving entity also calculates MAC-1 and compare

it with one received with signaling message.Message with wrong or missing MAC-1 are discarded.All higher layer messages are automatically also integrity

protected.

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Measurement control

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Measurement control(1)This procedure is initiated from the UTRAN side to control

a measurement in a specific UE. The UTRAN sends a MEASUREMENT CONTROL message

to the UE on the DCCH. Example of this information :1. Measurement type: One of the types from a predefined

list where each type describes what the UE shall measure.2. Measurement identity number: A reference number that

is used by the UTRAN at modification of the measurement and by the UE in the measurement report.

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Measurement control(2)3. Measurement command: One out of three different

measurement commands : Setup & Modify & Release

4. Measurement objects: The objects the UE shall measure on, and corresponding object information.

5. Measurement quantity: The quantity the UE shall measure. This also includes the filtering of the measurements.

6. Measurement reporting criteria: The triggering of the measurement report, e.g. periodical, event-triggered or immediate reporting.

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Measurement Report

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Measurement ReportThe Measurement Report procedure is initiated from the

UE side when the reporting criteria are met. The message is sent using either acknowledged or

unacknowledged data transfer on the DCCH. The UE sends a MEASUREMENT REPORT message to the

UTRAN that includes the measurement identity and the measured values of the requested measurement objects.

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RRC Connection MobilityThe RRC layer performs evaluation, decision and

execution related to RRC connection mobility during an established RRC connection.

Ex: - Handover, - Preparation of handover to GSM or other systems, - Cell re–selection - Cell area update based on measurements done by the UE.

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