1. Long Term Evolution Protocols
© Tata Consultancy Services Ltd

2. Objective LTE Protocol stack Layer functionalities
Frame structure and Resource blocks of LTE
Channel Mapping between Layers
Transmission Parameters supports in LTE

3. LTE Protocol
LTE protocol stack for User Equipment (UE).
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4. Physical Layer
Takes care of Power control ,cell search for initial synchronization and handover
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5. =1ResourceElement(RE)
Physical Resource Blocks in LTE
OFDM Symbols 1 2 3 4 . 11 12 5 6
1Frame = 10 subframes
1 Subframe = 2 slots
Subcarriers
1slot has
6<= RBs <=100
12 Subcarriers x 7symbos
= 1 Resource Block (RB)
1 Subcarrier x 1 Symbol
=1ResourceElement(RE)
1 frame = 10 subframes
1 subframe = 2 Slots
1 slot has 6 <= RBs <= 100
12 Subcarriers x 7 symbols = 1 Resource Block (RB)
1 Subcarrier x 1 Symbol = 1 Resource Element
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6. LTE Transmission Parameters
Values
Bandwidth (MHz)
1.4 3 5 10 15 20
Subframe duration
1ms
Subcarrier spacing
15kHz
Usable subcarriers 72
180
300
600
900
1200
Resource blocks 6 25 50 75
100
OFDM symbols for time slot
7 (normal CP) or 6 (extended CP)
Modulation schemes
BPSK or QPSK (signaling)
QPSK, 16QAM or 64 QAM (data)
Coding schemes
1/3 Convolutional (PDCCH)
1/3 Turbo (data and LTE messaging)
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7. Signals
Cell-specific Reference Signals
Synchronization Signals
Demodulation Reference Signals
There is one reference signal transmitted per downlink antenna port. The number of downlink antenna ports equals 1, 2, or 4.
504 unique physical cell identities.
Uplink reference signals for channel estimation for coherent demodulation
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8. MAC Layer
The main services and functions of the MAC(Medium Access Control):
Mapping between logical channels and transport channels.
- scheduling information reporting.
- Error correction through HARQ.
- Priority handling between UEs by means of dynamic scheduling.
A general classification of logical channels is into two groups:
- Control Channels (for the transfer of control plane information);
- Traffic Channels (for the transfer of user plane information).
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9. RLC Layer
The main services and functions of the RLC(Radio Link Control) :
- Error Correction through ARQ.
- Concatenation, segmentation and reassembly of RLC SDUs
- Duplicate detection.
- Protocol error detection.
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10. RLC Modes of Operation Modes of Operation Acknowledged Transparent
(AM)
Transparent
(TM)
Unacknowledged
(UM)
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11. RLC Layer contd…
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12. PDCP Layer
The main services and functions of the PDCP(Packet Data Converge Control):
- Header compression and decompression: ROHC only.
- Transfer of user data.
-- Retransmission of PDCP SDUs at handover for RLC AM.
- Ciphering and Integrity Protection.
- Transfer of control plane data.
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13. PDCP Layer contd…
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14. RRC Layer
The main services and functions of the RRC(Radio Resource Control):
Broadcast of System Information
Paging
Establishment, maintenance and release of an RRC connection between the UE and E-UTRAN including
- Allocation of temporary identifiers between UE and E-UTRAN
Configuration of signalling radio bearer(s) for RRC connection
- mobility.
- Handover; -UE cell selection and reselection and control of cell selection and reselection.
Notification for MBMS services.
services.
- QoS management functions.
- UE measurement reporting and control of the reporting.
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15. Layer Functionalities
The RRC layer controls the lower layers in both
eNB and UE, and the lower layers provide
Feedback to the RRC
Initiate Security
Activation
RRC
PDCP
RLC
MAC
PHY
Configure RLC mode
for DRBs
Configure logical channel priorities
Configure HARQ
Parameters
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16. Radio Protocol Architecture
Radio protocol architecture 2 types .
User Plane
Control Plane
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17. User Plane
User plane protocol stack between UE and e-NodeB
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18. User Plane contd.. User Plane consists of PDCP,RLC,MAC layers
Packets received by a layer are called Service Data Unit (SDU)
Output of a layer is referred to by Protocol Data Unit (PDU)
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19. Control Plane
Control Plane
Between UE and MME
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20. Control Plane contd..
Control plane handles radio –specific functionality which depends on the state of mobile.
Control plane includes RRC layer –responsible for configuring lower layers
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21. Interfaces
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22. Interfaces contd…
The application layer signaling protocol S1 Application Protocol (S1AP) provides signaling services between the eNB and MME.
The application layer signaling protocol X2 Application Protocol (X2AP) provides signaling services between two eNBs.
The SCTP is added on top of IP for reliable transport of application layer messages.
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23. Stream Control Transmission Protocol (SCTP)
Multi-Streaming
Reliable Transmission
SCTP
Functions
Multi-homing
Message
Oriented
Ordered Delivery within
a Stream
Flow Control and
Congestion Control
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24. S1 Application Protocol (S1AP)
E-RAB Management
Context Management
NAS Transport
Initial UE message
Downlink&Uplink NAS Transport
Paging
Handover Signaling
Path Switch Request
eNB Status Transfer
MME Status Transfer
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25. Non-Access Stratum (NAS)
The NAS sub layer between the UE and the MME is transparent to the eNB. .
The NAS layer takes care of two areas.
1) It handles all the procedures related to registration ,authentication and security procedure,paging procedure and mobility management of a UE
2) Session management includes creation, deletion and modification of both default and dedicated EPS bearers.
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26. Non-Access Stratum (NAS) contd…
NAS Functions
EPS Mobility Management
Attach, Detach, Tracking Area Update
Authentication and Security Procedures
Paging Procedures
EPS Session Management
Default Bearer Establishment
Dedicated Bearer Establishment
Bearer Management
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27. NAS Transport MME NAS NAS Initial UE msg RRC RRC S1AP S1AP SRB1
Piggybacked to
RRCConnectionSetupComplete
DL NAS Transport
S1-MME Bearer
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28. X2 Application Protocol (X2AP)
Mobility Management:
Start or cancel a handover, forward user plane data, transfer PDCP SN status and release UE context.
Load Management:
Indicate resource status, provide interference and load coordination between neighbor eNBs. The knowledge of neighbor eNB load status helps efficient scheduling.
eNB Configuration Update
Application level configuration data needed for two eNBs
General Error Situation Report
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29. X2 Application Protocol (X2AP) Functions
Mobility Management
Handover Request & cancel
SN Status Transfer
UE Context Release
eNB Configuration Update
Load Management/Indication
Resource Status Request
Reporting of General Error
Error Indication
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30. GTP (GPRS Tunneling Protocol)
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31. GTP contd..
used to encapsulate user data when passing through core network and also carries bearer specific signalling traffic between various core network entities
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32. Overview of Lte Protocol stack
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33. Life of packet - Downlink
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34. Summary
Lte protocol stack contains Physical ,MAC,RLC,RRC,PDCP ,AS,NAS sub layers.
Physical layer carries all the information from MAC transport channels over the interface.
MAC layer is responsible for mapping between the logical channels and transport channels.
RLC is responsible for error correction through ARQ
RRC main service for broadcast system information related to the non- access startum(NAS).
PDCP responsible for header compression and decompression of data
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35. Thank You
Thank You