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1
Default Bearer Setup In LTE
By: Zunaira TahirNetwork Performance Optimization Trainee Engineer at Ericsson
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Contents of Presentation: Identifiers Used in LTE
Radio Bearers in LTE
Default Bearer Setup in LTE
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LTE ARCHITECTURE
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IDENTIFIERS USED IN LTE
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Identifiers Used in LTE
PLMN IDIdentify the network
MCC+MNC
MMEGIIdentify MME group in pool
areas
MMECIdentify MME within MME group
MMEIIdentify MME within PLMN
MMEC+MMEGI
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MME Pool Area:
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Benefits of MME Pool Area:
Region A Region B
MME Pool Area 1MME 1 and MME 2
MME Pool Area 2MME 3 and MME 4
Down town
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Identifiers Used in LTE
M TMSIIdentify the mobile to serving
MME
GUMMEIIdentify MME anywhere in the
worldMMEI+PLMN-ID
GUTI To identify a UE between the UE and the MME on behalf of
IMSI for security reasonGUMMEI+ M-TMSI
S TMSIUsed for paging and service
requestM TMSI+ MMEC
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Comparison of GUTI and S-TMSI:
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Identifiers Used in LTE
RNTIUsed to differentiate one user
from other
LBIIdentify default bearer linked
with dedicated bearer
P-GW IDAssigned by HSS to identify a
specific PDN GW (P-GW)
eNB IDIdentify eNodeB within PLMN
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PopUp:
How many types of RNTIs are available in the network?
Who issues RNTI?
How can PHY layer know which RNTI it has to use?
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RADIO ACCESS BEARERS IN LTE
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What is the difference between RRC and RAB?
PopUp:
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Hey, I want to buy some
things from store
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Okay, tell me what do you want to buy
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Buyer will write the items on paper, wrap the paper
around stone and throws the stone towards
seller
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Seller will send the list to store via robot car to confirm
whether all items are
available in store or not
Assume the positive Response from store
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How to do shipment? There is no path to deliver the order
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Let us assume that seller has some carriers and some iron
rods.
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The seller will put the rods and will
establish the path for delivery
of order. The establishment of path for shipment
is called RRC
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The seller then chooses the carrier
according to the type of material which
needs to be delivered. The carrier which is
delivering the order is called RAB
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Definitions of RRC and RAB
RRCA signaling link established as the result of allocation of resources
RABA signaling link that carriers the actual information satisfying the QOS demands
of user
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Lets map the analogy to available technologies !
GSM Network:• Buyer : MS• Seller : BTS• Store: BSC• Robot Car: Abis interface• SD Assignment: RRC • Traffic flow over TCH: Radio bearer
LTE Network:• Buyer : UE• eNode B is the only manager of radio resources in LTE • There is no concept of robot car• We can assume that seller is sitting in the store and receiving the order via telephone
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Radio Bearers in LTE
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DEFAULT BEARER SETUP
IN LTE
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Random Access Procedure in LTE
Random Access Preamble
UE sends one of the 64 preambles,
RA-RNTI
How the UE will come to know when it has to transmit RACH Preamble?
UE will listen the system information type 2
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System Information Type 2:
Number of Rach Preambles: 4-64
Preamble TransMax
Ra-Response Window
Prach_configindex
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Random Access Procedure in LTE
Random Access Preamble
Random Access Response
RRC Setup Request
RRC Setup
UE sends one of the 64 preambles,
RA-RNTI
DL-SCH, RA-RNTI, TA, Uplink resource grant,
TC-RNTI UL-SCH, C-RNTI,
Establishment cause
This message will establish signaling
connection
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ATTACH PROCEDURES IN LTE
Using IMSI
Using GUTI (MME Unchanged)
Using GUTI (MME Changed)
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Attach Procedure Using IMSI
Attach Request
Initial UE message
RRC Connection setup
complete+Attach req
NAS-PDU, ECGI, TAI
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Authentication Procedure
Authentication info req
HSS
Generates AV(RAND, AUTN, XRES, KASME)
Authentication response
IMSI, PLMN ID
Auth. Req.
RAND, AUTN,
KSIASME
AUTNue=AUTNhss
Auth. Response (RES)
RES=XRES
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Security Setup Procedure
Generates Security keys
Security mode Command
Selected ciphering algorithm
Generates Security keys
Security Mode Complete
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Location Update Procedure
Location Update Answer
IMSI, MMEI Location Update Request
HSS
APN, PGW-ID,
QOS Profile, IMSI
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Attach Procedure Using GUTI (MME Unchanged)
Attach Request (GUTI)
Authentication
Security Setup
Location Update
Identity Request
Identity Response
IMSI, GUTI, KSIasme, NAS MAC, NASKeys
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Attach Procedure Using GUTI (MME Changed)
UE N-MME
Attach Request
Authentication
Security Setup
Location Update
Identity Request
Identity Response
O-MME
Attach Request (GUTI)
Identity Request
Identity Response
Fail
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Default Bearer Setup
UES-
GW
Session request
P-GW
EPS Bearer ID, IMSI, PGW ID,
APN, QOS Profile, ECGI, TAI
S5 S-GW TEID (DL)
Session request
EPS Bearer ID, IMSI, PGW ID,
APN, QOS Profile, ECGI, TAI,
S5 S-GW, TEIDUE IP Address
P-GW TEID (UL)
37
Default Bearer Setup
UES-
GWP-GW
S5 Bearer
Response
EPS Bearer ID,UE IP, PGW ID, APN, QOS
Profile, S5 P-GW TEID, Charging
info
S1 S-GW TEID
Response
EPS Bearer ID,UE IP, APN, QOS Profile, S5 P-GW TEID, S1
S-GW TEID Charging info
38
Default Bearer Setup
UES-
GWP-GW
Receive S1 TEID (UL)
Initial context setup
E-RAB ID, E-RAB QOS, S1 S-GW
TEID (UL), Kenb, GUTI, UE IP, UE
security algo.
Sec mode cmd
Sec Mode comp.
DRB ID
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Default Bearer Setup
UES-
GWP-GW
RRC Re configEPS Bearer ID, DRB ID
Initial contxt res.
DRB Bearer
E RAB ID, S1 enb TEID
(DL)
S1 enb TEID (DL)
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Default Bearer Setup
UES-
GW
Modify bearer request
P-GW
EPS Bearer ID, S1 enb TEID (DL)
Response
S1 Bearer Established
S1 Bearer EstablishedDRB
Established
41
THANK YOU