LTE Protocols and Procedures

Subject: 4G LTE
Category: Radio
Duration: 3 days

Course outline:

Introduction to EPS

● Evolution steps of the 3GPP systems, the goals for LTE
● LTE bandwidths, bit rates and UE categories EPS Network Architecture
● E-UTRA and Evolved Packet Core network architecture
● Nodes: UE, eNB, SGW, MME, PGW, PCRF
● Interfaces: Uu, X2, S1, S11, S5, Gx, S6a, SGi, Rx
● Overview of EPS protocols: PDCP, RRC, GTP, X2AP, S1-AP, S1-MME, GTP, Diameter
● IP connectivity, user plane and control plane
● Access Stratum signaling and Non-Access Stratum signaling
● E-UTRAN protocol stack and channel architecture
● E-UTRAN L3 and L2 protocols: RRC, PDCP, RLC, MAC, PHY

Non-Access Stratum (NAS) Protocols

● NAS protocols (EMM and ESM)
● UE states and state transitions (LTE-idle, LTE-active, LTE-detached)
● Subscriber identities and their relations (IMEI, IMSI, GUTI, STMSI, RNTIs)
● Security and keys’ derivation
● Integrity and Encryption – SNOW 3G, AES
● EPS Authentication and Key Agreement; Key Hierarchy
● Key distribution and mobility
● NAS message structure

Radio Resource Control (RRC) Protocol

● RRC procedures including system info broadcasting, paging, RRC connection establishment, security establishment, NAS message transport and RRC connection reconfiguration
● Types of radio bearers
● RRC States & State Transitions

Packet Data Convergence Protocol (PDCP)

● PDCP architecture
● PDCP Functions (robust header compression, ARQ at handover, status reporting ciphering and integrity protection)
● PDCP message structure for Data and Control

Radio Link Control (RLC) Protocol

● RLC architecture (Transparent Mode, Unacknowledged Mode, Acknowledged Mode)
● Functions (segmentation / concatenation, ARQ procedures)
● RLC PDU formats (RLC user plane and control PDUs)

MAC Protocol

● MAC Architecture
● MAC PDU: user plane and control plane parts
● Scheduling procedures for downlink and uplink resource assignments
● Scheduling Requests, Buffer Status Reports and Power Headroom Reports
● Hybrid-ARQ processes and HARQ operation
● Mapping of Logical Channels to Transport Channels
● MAC level identities mapping

LTE PHY Layer

● Logical, Transport and Physical channels and their relation to the radio interface protocol stack (i.e. Channel architecture)
● Adaptive Modulation and Coding, QPSK, 16-QAM, 64-QAM
● Principles of OFDM/OFDMA/SCFDMA
● Principles of MIMO
● Downlink and uplink frame structure and its elements (PRB, RE, CCE)
● L1 control information, formats and signaling
● Resource mapping to radio frame
● PHY layer related scheduling principles (including ”maximum SNIR”, ”round robin” and ”proportional fair” schedulers)

S1 Interface Procedures

● S1 CP and UP protocol stacks
● S1 Application Protocol (S1-AP)
● S1-AP identifiers
● S1-AP procedures: S1 association and SON related procedures, UE related procedures
● GTP-U protocol (including tunneling concept and TEID)

X2 Interface Procedures

● X2 CP and UP protocol stacks
● X2 Application Protocol (X2-AP)
● X2-AP identifiers
● X2-AP procedures: X2 association procedures, UE related procedures, SON related procedures S11, S5/S8, S10 Interface Procedures
● CP and UP protocol stacks for each interface
● GTP-C (eGTP) protocol
● GTP-C message header and tunneling concept
● Functions and procedures related to each interface (UE context exchange, call establishment, bearer management, etc.)

IMS and End-to-End Signaling

● IMS architecture (S-CSCF, P-CSCF, I-CSCF, HSS, AS, etc.)
● IMS security and PCC considerations
● SIP Basics – registration, session establishment
● IMS end-to-end protocol stack
● IMS end-to-end call establishment
● Voice in LTE (CS Fallback, Voice Call Continuity, VoLGA)

Interworking with 3GPP and non-3GPP networks

● Roaming
● Inter-working with 3GPP and non-3GPP networks
● Inter-RAT handover: example of handover between LTE and UMTS

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