Post on 03-Apr-2018
transcript
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Background
Signalling & interfaces
Interface
Application protocol
Service related signalling
MSC/SGSN
node BRNC
UE
RNC
RRC
NBAP
RNSAP
RANAPNAS/layer 3
Uu
Iub
Iur
Iu
service user service access point
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Allow communication (signalling: control plane) between different network elements
Technology specific (e.g. UMTS)
UMTS application protocols:
RRC (Radio Resource Control)
Runs over Uu and Iub interface, between UE and RNC
NBAP (Node B Application Part)
Used on Iub interface between node B and RNC
RANAP (Radio Access Network Application Part)
Used on Iucs/Iups interface between RNC and MSC/SGSN
RNSAP (Radio Network Subsystem Application Part)
Used on Iur interface between different RNCs
Remark: only RRC application protocol will be studied in detail
Can be captured on air interface during drive testing
Background
Application protocols
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Used for service setup and release
Between service user (UE) and service access point (MSC/SGSN)
Service specific, but not technology specific
UMTS service related signalling is different for voice call and PS data session
2G and 3G service related signalling can be the same for the same service type (e.g. voice
call)
Background
Service related signalling
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Only one RRC Connection in connected mode, no RRC Connection in idle mode
RRC Connection consists of typically four signalling Radio Bearers (sRB)
sRB1, sRB2, sRB3 and sRB4
Used for transport of RRC application protocol and NAS/layer 3 messages
Up to two Iu signalling connections in connected mode (to MSC and/or SGSN), none in idle mode
Background
Control plane
MSC/SGSN
node BRNC
UE
RNC
RRC (signalling) connection
Uu
Iub
Iur
Iu
Iu signalling connection
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One RAB for each service type in connected mode (e.g. voice call, PS data service), no RAB in
idle mode
RAB consists of one or three RBs (depending on service)
Voice call three RBs, all other services only one RB
One Iu bearer for every RAB used
Background
User plane
MSC/SGSN
node BRNC
UE
RNC
Radio Bearer (RB)
Uu
Iub
Iur
Iu
Iu bearerRadio Access Bearer (RAB)
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Background
Control/user plane flow during soft handover
MSC/SGSN
node BRNC
UE
Iub
Iur
Iu
RNC
RNC
Iur
node B
node B
Iub
Iub
Serving RNC (SRNC)
Drift RNC (DRNC)
Drift RNC (DRNC)
One logical RRC Connection
Signalling/data flow
Radio Link (RL)
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BackgroundControl plane vs. user plane bit pipe
Control plane bit pipe (RRC Connection):
Signalling transport (RRC, NAS)
Typically 4 sRBs setup during RRC Connection Setup procedure
User plane bit pipe:
Transport of user data
1 or 3 RBs setup during RB Setup procedure
UE
SRNC
C-plane U-plane
sRB 14 RB 13
RRC Connection Setup
procedure
RB Setup procedure
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BackgroundControl plane vs. user plane RRC procedures
RRC Connection Setup procedure
RB Setup procedure
UE SRNC
RB Release procedure
RRC Connection Release procedure
Setup control plane
bit pipe
Release control plane
bit pipe
Setup user planebit pipe
Release user plane
bit pipe
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BackgroundRRC Connection Setup procedure
RRC Connection Setup procedure:
First step to go from idle mode to connected mode
Establishment of RRC signalling connection
Setup dedicated resources control plane (CCCH
DCCH) RRC Connection Request:
Used by UE to get access to network
Retransmitted if no reaction from network
Maximum # retransmissions: N300 (default: 3)
Time between retransmissions: T300 (default: 1000ms) Parameters in System Information
UE SRNC
RRC Connection Request (UL-CCCH)
RRC Connection Setup (DL-CCCH)
RRC Connection Setup Complete (UL-DCCH)
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BackgroundRRC Connection Setup procedure
RRC Connection Setup:
Contains downlink instructions regarding setup control plane bit pipe
RRC Connection Setup Complete:
Confirmation from UE indicating successful setup of control plane bit pipe Contains information on UE capabilities (e.g. HSDPA UE category)
UE SRNC
RRC Connection Request (UL-CCCH)
RRC Connection Setup (DL-CCCH)
RRC Connection Setup Complete (DL-DCCH)
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BackgroundRRC Connection Release procedure
UE SRNC
RRC Connection Release Complete (UL-DCCH)
RRC Connection Release (DL-DCCH)
RRC Connection Release Complete (UL-DCCH)
Used to release RRC signalling connection
All sRBs released
To go from connected mode to idle mode
RRC Connection Release complete: typically retransmitted several times
# retransmissions: N308
Time between retransmissions: T308
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BackgroundRRC Connection Setup failure
UE SRNC
RRC Connection Request (UL-CCCH)
RRC Connection Reject (DL-CCCH)
Indication of unsuccessful RRC Connection Setup procedure
Reject cause, e.g. congestion
Wait time: time needed before retry
Optionally UE redirected to other carrier/RAT
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BackgroundRB Setup procedure
UE SRNC
RB Setup
RB Setup Complete
Setup dedicated resources/bit pipe user plane
Consists of 1 or 3 RBs depending on requested service
Triggered by RAB setup procedure (RANAP on Iu interface)
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BackgroundRB Release procedure
UE SRNC
RB Release
RB Release Complete
Release dedicated resources/bit pipe user plane
Used for PS procedures
Not used for CS procedures
RBs released with RRC Connection Release procedure
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BackgroundCS vs. PS service
CS service PS service
CS service
No RB release procedure
All RBs released implicitly with RRC Connection Release procedure
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BackgroundInitial Direct Transfer
UE SRNC
Initial Direct Transfer (initial NAS message)
Used to setup Iu signalling connection between SRNC and MSC/SGSN
Carries the very first NAS message of the session from UE to SRNC
Contains CN domain:
CS: Iu signalling connection needed to MSC
PS: Iu signalling connection needed to SGSN
Last step to go from idle mode to connected mode:
1) RRC Connection Setup procedure (signalling connection UE-SRNC)
2) Initial Direct Transfer (signalling connection UE-MSC/SGSN)
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BackgroundUplink/Downlink Direct Transfer
UE SRNC
Uplink Direct Transfer (NAS message)
Used to carry NAS messages between UE and SRNC, once the Iu signalling connection exists
Carries all NAS messages of the session except the initial NAS message
Downlink Direct Transfer (NAS message)
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BackgroundMobile Originating Call part 1
Downlink Direct Transfer (CC Call Proceeding)
UE SRNC
RRC Connection Setup Complete
RRC Connection Request
RRC Connection Setup
Initial Direct Transfer (MM CM Service Request)
Security Mode Command
Security Mode Complete
Uplink Direct Transfer (CC Setup)
RB Setup
RB Setup Complete
RRC Connection Setup procedure
RB Setup procedure
Security Mode procedure: ciphering
NAS signalling: service setup part 1
First NAS messageDownlink Direct Transfer (MMAuth Req)
Uplink Direct Transfer (MMAuth Resp) Authentication procedure: double check UE id
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BackgroundMobile Originating Call part 2
UE SRNC
RRC Connection Release
RRC Connection Release Complete
Uplink Direct Transfer (CC Disconnect)
Downlink Direct Transfer (CC Release)
Uplink Direct Transfer (CC Release Complete)
RRC Connection Release Complete
NAS signalling: service release
RRC Connection Release procedure
Downlink Direct Transfer (CC Alerting)
Downlink Direct Transfer (CC Connect)
Uplink Direct Transfer (CC Connect Ack)
NAS signalling: service setup part 2
ACTIVE CALL
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BackgroundIntra-frequency soft handover
3G coverage f1 3G coverage f1
Soft handover area
Handover between cells with same carrier
Soft handover:
UE connected simultaneously to multiple cells
Iur interface needed if several RNCs involved
Soft handover area:
Overlapping cells with same quality
RNCRNC
Iur
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BackgroundIntra-frequency soft handover area
2-cell soft handover area
3-cell soft handover area
Active Set (AS): all cells the UE is connected to in connected mode
Typically Active Set is limited to maximum three cells
Several possibilities for soft handover area:
2-cell soft handover area
3-cell soft handover area
Soft handover causes redundancy, but results in reduction of transmitted power (SHO Gain)
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BackgroundRRC state model main states
Two main states:
Idle mode: no RRC connection
Connected mode: one logical RRC connection
Connected mode
Idle mode
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BackgroundRRC state model - substates
cell-DCH cell-FACH
cell-PCHURA-PCH
Connected mode
Idle mode
Connected mode: four substates
Cell-DCH: UE is allocated dedicated resources (e.g. codes from code tree)
Cell-FACH: UE is using shared resources (common control channels RACH/FACH)
Cell-PCH/URA-PCH
UE in sleep mode, not using shared/dedicated resources from network
Paging needed to wake up UE, resulting in transition to cell-FACH
Location of UE known to network: cell (cell-PCH) or URA (URA-PCH)
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BackgroundRadio Bearer upgrade/downgrade
Switching between different data rates
64kbps 128kbps 384kbps
By changing the uplink/downlink spreading factor
Performed with Transport Channel Reconfiguration
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BackgroundRadio Bearer upgrade/downgrade Spreading Factor
Symmetrical service: SF DL is double of SF UL
Data rate (DL/UL) SF DL SF UL
64/64 32 16
64/128 32 8
64/384 32 4
128/64 16 16
128/128 16 8
128/384 16 4
384/64 8 16
384/128 8 8
384/384 8 4
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BackgroundRadio Bearer upgrade/downgrade logfile example