LTE Call Flow Procedures ,Intra LTE HO procedure

LTE CALL FLOW

1. LTE Call Flow Procedures LTE Call Flow Procedures Rd
•
R
an
d
om

access
•Attach process
Dt h
•
D
e
t
ac
h
process
•Intra LTE HO procedure
CSFB
•
CSFB
•Events

2. LTE Random Access LTE Random Access

4. Step 1: Msg1
UE selects one of the 64 available RACH
p
reambles
p
Step 2: Msg2 The messa
g
e carries followin
g
information
gg
Temporary C-RNTI Timing Advance Value Uplink Grant Resource
Step 3: Msg3 Using UL-SCH, UE sends "RRC connection request message" to eNodeB UE i id tifi d b t C
RNTI ( i d i th i t b
UE i
s
id
en
tifi
e
d b
y
t
emporary
C
-
RNTI (
ass
i
gne
d i
n
th
e

prev
i
ous

s
t
ep
b
y

eNodeB) The message contains following
UE identity (TMSI or Random Value ) UE identity (TMSI or Random Value ) Connection establishment cause
Step 4: Msg4 Step 4: Msg4 eNodeB responds with contention resolution message to UE whose message was successfully received in step 3. This message is address towards TMSI value or Random number (from previous steps) but contains the new C value or Random number (from previous steps) but contains the new C RNTI which will be used for the further communication

5. Attach process A
ttach process

6. The detach procedure
is either
initiated by the
UE or
by the
network
The detach procedure
is either
initiated by the
UE or
by the
network
.

The network initiates the detach procedure: To detach the UE for EPS services or non-EPS services or both
To disconnect the UE from the last PDN to which it is connected
To inform the UE to re
-
attach to the network and re
-
establish all PDN
To inform the UE to re
attach to the network and re
establish all PDN
connections.
The UE initiate the detach
p
rocedure when:
p
the UE is switched off
the USIM is removed from the UE
the EPS capability of the UE is disabled

7. Detach process

8. Intra LTE HO procedure Intra LTE HO procedure

9. •The source eNB configures the UE measurement procedures according to the
area restriction information. UE sends MEASUREMENT REPORT by the rules
set by i.e. system information, specification etc. set by i.e. system information, specification etc.
•Source eNB makes decision based on MEASUREMENT REPORT and RRM
information to hand off UE and issues a HANDOVER REQUEST message to the
target eNB passing necessary information to prepare the HO at the target side.
•
A
dmission Control may be performed by the target eNB dependent on the
received E-RAB QoS information to increase the likelihood of a successful HO.
The target eNB configures the required resources according to the received E-
RAB
QoS
information
RAB
QoS
information
.
•Target eNB prepares HO with L1/L2 and sends the HANDOVER REQUEST
ACKNOWLEDGE to the source eNB. The HANDOVER REQUEST
ACKNOWLEDGE message includes a transparent container to be sent to the ACKNOWLEDGE message includes a transparent container to be sent to the UE as an RRC message to perform the handover.
•The UE receives the RRCConnectionReconfiguration message with necessary
p
arameters (i.e. new C-RNTI, tar
g
et eNB securit
y
al
g
orithm identifiers, and
p
g
yg
optionally dedicated RACH preamble, target eNB SIBs, etc.) and is commanded
by the source eNB to perform the HO.
•The source eNB sends the SN STATUS TRANSFER message to the target eNB
to co ve the pli k PDCP SN eceive stat s a d the dow li k PDCP SN to co
n
ve
y
the
u
pli
n
k PDCP SN
r
eceive
r
stat
u
s a
n
d the dow
n
li
n
k PDCP SN
transmitter status of E-RABs for which PDCP status preservation applies (i.e.
for RLC AM).
•
After receiving the
RRCConnectionReconfiguration
message including the
After receiving the
RRCConnectionReconfiguration
message including the
mobilityControlInformation , UE performs synchronisation to target eNB and
accesses the target cell via RACH.

10. •The target eNB responds with UL allocation and timing advance.
•UE sends the RRCConnectionReconfigurationComplete message (C-RNTI)
t fi th h d t th t t
NB
t i di t th t th h d
t
o

con
fi
rm
th
e
h
an
d
over
t
o
th
e
t
arge
t
e
NB
t
o
i
n
di
ca
t
e
th
a
t th
e
h
an
d
over

procedure is completed for the UE. The target eNB verifies the C-RNTI
sent in the RRCConnectionReconfigurationComplete message. The target
eNB can now be
g
in sendin
g
data to the UE.
gg
•The target eNB sends a PATH SWITCH message to MME to inform that
the UE has changed cell.
•The MME sends an UPDATE USER PLANE REQUEST message to the
Serving Gateway Serving Gateway
.
•The Serving Gateway switches the downlink data path to the target side.
The Serving gateway sends one or more "end marker" packets on the old
path to the source eNB and then can release any U-plane/TNL resources
td th
NB
t
owar
d
s
th
e

source

e
NB
.
•Serving Gateway sends an UPDATE USER PLANE RESPONSE message to
MME.
•
The MME confirms the PATH SWITCH message with the PATH SWITCH The MME confirms the PATH SWITCH message with the PATH SWITCH A
CKNOWLEDGE message.
•By sending UE CONTEXT RELEASE, the target eNB informs success of HO
to source eNB and triggers the release of resources by the source eNB. The
target
eNB
sends this message after the PATH SWITCH ACKNOWLEDGE
target
eNB
sends this message after the PATH SWITCH ACKNOWLEDGE
message is received from the MME.
•Upon reception of the UE CONTEXT RELEASE message, the source eNB
can release radio and C-
p
lane related resources associated to the UE
id f di i
p
context. Any ongo
i
ng
d
ata
f
orwar
di
ng may cont
i
nue.

11. CSFB Inter-connected nodes CSFB Inter-connected nodes
The support CS fallback in EPS a new interface SGs is added in LTE
architecture. SGs interface is the reference point between the MME and MSC
server. SGs interface is used for the mobility management and paging procedures between EPS and CS domain and is based on the Gs interface procedures between EPS and CS domain
,
and is based on the Gs interface
procedures

12. CS Fallback and IMS based services can co-exist in the same operator
network. Although its not very straight forward to support CS fallback, all
ii i l
i
d
part
i
c
i
pat
i
ng e
l
ements
i
.e UE, MME, MSC & E-UTRAN nee
d
s to support
additional functionalities.
UEUE supports access to E-UTRAN/EPC as well as access to the CS domain over GERAN and/or UTRAN.
Combined procedures for EPS/IMSI attach, update and detach.
CS

fallback

and

SMS

procedures

for

using

CS

domain

services
.
CS fallback and SMS procedures for using CS domain services MME Deriving a VLR number and LAI from the GUTI received from the UE or from a default LAI.
Maintaining of SGs association towards MSC/VLR for EPS/IMSI attached UE.
Initiating IMSI detach at EPS detach.
Initiating paging procedure towards eNodeBwhen MSC pages the UE for CS services.
Support of SMS procedures
Rejecting CS Fallback call request (e g due to O&M reasons) Rejecting CS Fallback call request (e
.g
. due to O&M reasons)
Use of the LAI and a hash value from the IMSI to determine the VLR number when multiple
MSC/VLRs serve the same LAI.
MSC
Maintaining SGs association towards MME for EPS/IMSI attached UE.
Support of SMS procedures as provided in 3GPP specification
E-UTRAN F di i t d SMS t th UE F
orwar
di
ng

pag
i
ng

reques
t
an
d SMS t
o
th
e
UE
.
Directing the UE to the target CS capable cell.

13. CSFB message flow CSFB message flow

14. 1a. The UE sends an Extended Service Request (CS Fallback Indicator) to the MME. Extended
Service Request message is encapsulated in RRC and S 1 -AP messages. CS Fallback Indicator
indicates MME to perform CS Fallback.
1b. The MME sends an S1-AP UE Context Modification Request message to eNB that includes a
CS
Fallback Indicator. This message indicates to the eNB that the UE should be moved to
UTRAN/GERAN Th l f th CS F llb k I di t i t t "CS F llb k ith t PS HO UTRAN/GERAN
. Th
e

va
l
ue

o
f th
e
CS F
a
llb
ac
k I
n
di
ca
t
or
i
s

se
t t
o
"CS F
a
llb
ac
k
w
ith
ou
t PS HO
Required"
1c. The eNB shall re
p
l
y
with S 1 -
A
P UE Context Modification Res
p
onse messa
g
e
py
pg
2. The eNodeB may optionally solicit a measurement report from the UE to determine the target
GERAN/UTRA cell to which the redirection procedure will be performed.
3. If the UE and network support inter-RAT cell change order, The eNodeB triggers an inter-
RAT cell change order
4. The eNodeB sends an S1-AP UE Context Release Request message to the MME.
5. The MME releases the UE Context in the eNodeB as well as all eNodeB related information in
h
t
h
e S-GW
6a. (Step 6a is performed if step 3a, Cell Change Order to GERAN, was performed)
The UE moves to the new cell in GERAN The UE uses the NACC information and/or receives the The UE moves to the new cell in GERAN
. The UE uses the NACC information and/or receives the
broadcast System Information and when it has all of the necessary information to access the
GERAN cell, establishes a radio signaling connection.

15. 7. If the target RAT is GERAN and DTM is not supported, the UE starts the Suspend procedure.
This triggers the SGS to send a Suspend Request message to the MME, The MME returns a
Suspend Response to the SGSN even though the GUTI cannot be derived from the P-TMS1 and
RAI pair RAI pair 8. If the S1 -AP UE Context Release Request message, received from the eNodeB in step 4,
indicates that the UE is not available for the PS service in the target cell the MME starts the
ti d i f
GBR b d th d ti ti f GBR b t d
preserva
ti
on

an
d
suspens
i
on

o
f
non-
GBR b
earers

an
d th
e
d
eac
ti
va
ti
on

o
f GBR b
earers
t
owar
d
s

S-GW and P-GW(s). The MME stores in the UE context that UE is in suspended status.
9. The UE continues with the MO call setu
p

p
rocedure with sendin
g
CM Service Re
q
uest.
pp g q
10a. if the UE is not registered in the MSG serving the 2G/3G cell or the UE is not allowed in
the LA, the MSG shall reject the service request, if implicit location update is not performed.
10b. A UE detecting that the MSG rejected the service request shall perform the Location Area
Update or a Combined RA LA procedure according to existing GERAN or UTRAN procedures for
the different Network Modes of O
p
eration (NMO).
p
10c The UE initiates the CS call establishment procedure. 11 Aft th CS i ll i t i t d d if th UE i i GERAN d PS i 11
. Aft
er
th
e
CS
vo
i
ce

ca
ll i
s
t
erm
i
na
t
e
d
an
d if th
e
UE i
s
i
n
GERAN
an
d PS
serv
i
ces

are

suspended, then the UE shall resume PS services as specified in TS 23.060 [3]. A Gn/Gp -SGSN
will follow TS 23.060 [3] to resume the PDP Contexts). An S4 SGSN will follow TS 23.060 [3]
to resume the bearers, and informs the S-GW and P-GW(s) to resume the suspended bearers. If
th UE h t d t E
UTRAN ft th CS i ll t i t d th th UE h ll
th
e
UE h
as

re
t
urne
d t
o
E
-
UTRAN
a
ft
er
th
e
CS
vo
i
ce

ca
ll
was
t
erm
i
na
t
e
d
,
th
en
th
e
UE
s
h
a
ll
resume PS service by sending TAU to MME. The MME will in addition inform S-GW and P-
GW(s) to resume the suspended bearers

16. LTE Events LTE Events
A1 & A2 A1 & A2

17. A3 & A4 A3 & A4
Offset

18. A5A5

19. B1 & B2 B1 & B2

20. LTE/WCDMA Events comparison LTE/WCDMA Events comparison

21. Thank Thank

Thank
You You
..

☺☺