3G Optimization PS HSDPA Layer Messages

RRC connection setup procedure is performed for the UE to set up a signaling connection  to the SRNC. RRC connection setup is always initiated by the UE. One UE has a maximum of one RRC connection at a time.

Triggering Conditions : The UE in idle mode initiates the RRC connection setup procedure when the NAS of the UE requests the establishment of a signaling connection When the SRNC receives an RRC CONNECTION REQUEST message from the UE, the Radio Resource Management (RRM) module of the RNC determines whether to accept or reject the RRC connection request, based on a specific  algorithm. If accepting the request, the RRM module further determines whether to set up the RRC connection on a Dedicated Channel (DCH)or on a Common Channel (CCH),based on a specific RRM algorithm. Typically, an RRC connection is set up on the DCH.

The procedure shown is described as follows:
1.The UE sends an RRC CONNECTION REQUEST message to the SRNC through the uplink CCCH(RACH), requesting the establishment of an RRC connection.
2.Based on the cause in the RRC connection request and the system resource status, the SRNC determines to set up the RRC connection on a DCH and allocates the Radio
NetworkTemporary Identity(RNTI),radio resources, and L1 and L2 resources. Then the SRNC sends a RADIO LINK SETUP REQUEST message to the NodeB, requesting the NodeB to
allocate the specific radio link resources required for an RRC connection.
3.The NodeB responds with a RADIO LINK SETUP RESPONSE message to the SRNC after successfully preparing the resources.
4.The SRNC uses the ALCAP protocol to set up the Iub user plane transport bearer and performs the synchronization between the SRNC and the NodeB. This procedure is optional. It
is required for the ATM-based Iub interface only.
5.The SRNC sends an RRC CONNECTION SETUP message to the UE through the downlink CCCH (FACH). The message contains the information about the DCH allocated by the SRNC.
6. UE and NodeB initiate L1 Synchronization. NodeB sends NBAP :Synchronization Indicator message to SRNC when the uplink enter "In-Sync" state
7. The UE sends an RRC CONNECTION SETUP COMPLETE message to the SRNC through the uplink Dedicated Control Channel (DCCH) that is just set up. The message
indicates that the RRC connection setup procedure ends.

If the RNC judges that the RRC connection request cannot be set up (for instance, due to insufficient resources), it directly sends an RRC CONNECTION REJECT message to theUE, and  indicates the reject reason in the message

The PS Session Setup procedure is performed to set up a PS session

Triggering Conditions: The UE send Activate PDP context request message to RNC. PDP Context Activation is performed when the UE initiates a packet call setup. The UE has the state Packet Mobility Management Connected that enables the user to transmitt and receive data while moving within a PLMN. and starts the PDP context activation procedure used to set up and remove a virtual data channel between a terminal connected to a UE and a GGSN. PDP contexts deal with allocation of IP addresses to the UE and Quality of Service, QoS, parameters. A Radio Access bearer establishes on request of the SGSN in order to realize the air interface connection. At the end the UE has an IP address NSAPI (Network layer Service Access Point Identifier) and a TLLI  (Temporary Logical Link Identity) associated to IMSI.

IP addresses can be allocated dynamically or statistically. If allocated dynamically, this significantly reduces the total number of IP addresses required per PLMN. Support of static IP address allocation enables subscribers to provide their own IP addresses. This can be useful when accesing secure networks that use the calling IP address as a form of security check. The support of QoS enables the operator to differentiate GPRS services.

When dynamic addressing from the home PLMN or the Visitor PLMN is used, it is the responsibility of the GGSN to allocate and release the dynamic PDP address.
The procedure shown is described as follows:
1.
 The UE initiates the PS Session by using the Service Request (Service Type=Data) message. After the RR setup completion the UE asks for initial direct transfer to the serving node. The RNC
 sets-up an SCCP connection with the SGSN and transfers the initial service request (Authentication and ciphering may performed depends on operator's setting)
2
.
The UE sends an Activate PDP Context Request (NSAPI, TI(Teardown Indication), PDP Type, Address, APN (Access Point Name), QoS (Quality of Service) Requested, PDP Configuration
Options) message to the SGSN The UE shall use PDP Address to indicate whether it requires the use of a static PDP address or whether it requires the use of a dynamic PDP address.
3.
 The SGSN sends a RAB Assignment Request message to the RNC to establish a RABs
4.The RNC establishes the appropriate radio bearer In WCDMA, RAB setup is done by the RAB Assignment procedure
5.The RNC returns a RAB Assignment Response message to the SGSN
6.
 The SGSN validates the active PDP Context Request using PDP Type (optional), PDP Address, APN (Access Point Name (optional) provided by the UE and the PDP context subscription
records.The SGSN sends a Create PDP Context Request message to the affected GGSN. Access Point Name shall be the APN Network Identifier of the APN. The GGSN may use Access Point
 
Name to find an external network and optionally to activate a service for this APN
7.
 The GGSN creates a new entry in its PDP context table and generates a Charging Id. The new entry allows the GGSN to route PDP PDUs (Policy Decision Point Protocol Data Units) between 
the SGSN and the external PDP network, and to start charging
 
8.The SGSN inserts the Network layer Service Access Point Identifier, NSAPI along with the GGSN address in its PDP context and informs the UE via RNC that the PDP Context is Accepted. The
SGSN selects Radio Priority and Packet flow Id based on QoS Negotiated, and returns an Activate PDP Context Accept message to the UE. The SGSN is now able to route PDP PDUs between
 
theGGSN and the UE and to start charging

The Radio Bearer Setup procedure shown is described as follows:
1.The CN sends an RAB ASSIGNMENT REQUEST message to the SRNC to initiate the RAB setup procedure.
2.(Optional; applicable to the ATM-based Iu-CS interface only) The SRNC maps the Quality of Service (QoS) parameters for the RAB to the AAL2 link characteristic parameters and radio resource
characteristic parameters. Based on the AAL2 link characteristic parameters,the ALCAP on the Iu interface initiates an Iu user plane transport bearer setup procedure.
3.The SRNC sends a RADIO LINK RECONFIGURATION PREPARE message to the NodeB, requesting the NodeB to prepare for adding one or more DCHs to the existing radio links for carrying 
 the RAB.
4.The NodeB allocates the associated resources and then sends a RADIO LINKRECONFIGURATION READY message to the SRNC.
5.(Optional; required for the ATM-based Iub interface only) The Iub ALCAP at the SRNC initiates an Iub user plane transport bearer setup procedure. The NodeB and the SRNC perform
 
synchronization by exchanging uplink and downlink synchronization frames in the DCH frame protocol.
6.The SRNC sends a RADIO BEARER SETUP message to the UE.

7.The SRNC sends a RADIO LINK RECONFIGURATION COMMIT message to theNodeB.
8.After performing the radio bearer setup, the UE sends a RADIO BEARER SETUP COMPLETE message to the SRNC.
9.The SRNC sends an RAB ASSIGNMENT RESPONSE message to the CN. The RAB isset up.
The procedure when RAB Setup Failure shown is described as follows:
1.The CN sends an RAB ASSIGNMENT REQUEST message to the SRNC to initiate the RAB setup procedure.
2.The SRNC sends an RAB ASSIGNMENT RESPONSE message to the CN. The message indicates the ID of the RAB that fails to be set up and the reason for the failure.
The PS session release procedure is performed to release services and resources after a session ends.

Triggering Conditions
 :  The UE send Deactivate PDP context request message to RNC. A PDP Context Deactivation is performed when the UE terminates a packet call. Before the 
deactivation,the UE has the state Active. After the PDP Context deactivation procedure the state becomes Packet Mobility Management Connected.The RAB will be released if there are no other
PDP contexts activated.PDP Deactivation may be initiated by a:UE procedure,SGSN procedure,GGSN procedure
 
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The procedure shown is described as follows:
1.The UE sends a Deactivate PDP Context Request (TI, Teardown Indication) message to the SGSN via the RNC
2.The SGSN sends a Delete PDP Context Request (TEID, NSAPI, Teardown Indication) message to the GGSN. If Teardown Indication was included by the UE in the Deactivate PDP Context Request message, then the SGSN deactivates all PDP contexts associated with this PDP address by including Teardown Indication in the Delete PDP Context Request message
3.The GGSN removes the PDP context(s) and returns a delete PDP Context Response (TEID) message to the SGSN. The Delete PDP Context messages are sent over the backbone network
4.The SGSN returns a Deactivate PDP Context Accept (TI) message to the UE via the RNC
5.
 In Iu mode, radio access bearer release is done by the RAB Assignment procedure
6. The SCCP connection between RNC and SGSN is released. At GPRS detach, all PDP contexts for the UE are implicitly deactivated

The RRC Connection Release procedure is performed to release the signaling connection and all radio bearers between UE and the UTRAN

Triggering Conditions:
 After a n RAB is released,the SRNC judges whether the RRC connection carries any other RAB or the UE. If judging that the RRC connection does not carry other RAB
of the UE,the SRNC initiates an RRC connection release procedure.
The procedure shown is described as follows: based on the resouce occupied by the RRC connection,there are two types of RRC connection release procedure: release of an RRC connection from DCH and release of an RRC connection from CCH 
(If an RRC connection needs to be released after a successful outgoing call,, the RRC connection on the DCH is released and if
 a radio bearers fails to be setup ,the RRC connection on the CCH is released)

1.The SRNC sends an RRC CONNECTION RELEASE message to the UE through the DCCH.
 
(NOTE: The SRNC may send the RRC CONNECTION RELEASE message several times to increase the probability of proper reception of the message by the UE. The RRC SNs of these messages are the same. The number of retransmissions and the transmission intervals are determined by the SRNC. If the SRNC does not receive an RRC CONNECTION RELEASE 
COMPLETE message from the UE after sending the RRC CONNECTION RELEASE message for four times, the SRNC judges that the UE has released the RRC connection.)

2.The UE sends an RRC CONNECTION RELEASE COMPLETE message to the SRNC.
3.The SRNC sends a RADIO LINK DELETION REQUEST message to the NodeB,requesting the NodeB to delete the radio link resources in the NodeB.
4.After releasing the resources, the NodeB sends a RADIO LINK DELETION RESPONSE message to the SRNC.
5.(Optional; required for the ATM-based Iub interface only) The SRNC uses the ALCAP protocol to initiate an Iub user plane transport bearer release procedure. Then, the RRC connection release

procedure ends. 

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