telecom • networking • design

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S1AP View of LTE Attach and EPS Bearer Setup

This sequence diagram looks at LTE Attach and EPS Bearer Setup from the S1AP vantage point. The following signaling is covered:

  1. UE Attach, authentication and security signaling
  2. Setup of two EPS Bearers (RAB id 5 and 6)
  3. Release of UE context due to inactivity
  4. Reestablishment of the UE context with a Service Request.

You can click on individual messages in the sequence diagram to see field level details.

Click to see the "S1AP View of LTE Attach & EPS Bearer Setup"  sequence diagram

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LTE S1-interface handover between eNodeBs

LTE networks prefer using the X2 interface for performing inter eNodeB handovers. An S1 handover is a fallback for scenarios where X2 interface is not available.

As the name suggests, S1 handovers take place over the S1-interface. The MME and the SGW are involved during the handover procedure.

An interesting part of LTE S1 handovers is the indirect tunnel that is established to carry the downlink data during the handover process. Refer to the S1 handover call flow for a detailed signaling flow.

Inter eNodeB S1 handover in LTE

 


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LTE Video Presentations

OFDM Time Frequency Multiplexing

Rohde & Schwarz‘s presentations provide an excellent introduction to LTE. The presentations are accompanied with an audio narration. The topics covered are covered:

  1. LTE Introduction
    • Motivations for LTE
    • LTE market and background
    • Requirements
    • Evolution path to LTE
  2. LTE Parameters and Downlink Modulation
    • LTE parameters and frequency bands
    • What is OFDMA?
    • OFDMA multiple access and downlink frame structure
    • OFDMA transmit and receive chains
  3. OFDMA and Downlink Frame Structure Details
    • Downlink OFDMA time-frequency multiplexing
    • LTE Spectrum Flexibility and Bandwidth
    • FDD downlink frame structure detailed
    • TDD frame structure
  4. SC-FDMA and LTE Uplink
    • Introduction to SC-FDMA and uplink frame structure
      • Marriage of single carrier transmission and FDMA
    • Uplink SC-FDMA tranmsit and receive chains
    • Peak to Average Power Ratio (PAPR) comparison with SC-FDMA and OFDMA
  5. Network and Protocol Architecture
    • LTE/SAE network architecture
    • EPC -Evolved Packet Core
    • Base Station control plane and user plane protocol stacks
    • EPC protocol stacks
  6. Channel Mapping and UE Categories
    • Logical and transport channel mapping in downlink and uplink
    • LTE UE Categories
  7. Initial Cell Search and Cell Selection
    • Downlink physical channels and signals
    • Cell Search and Selection in LTE
      • Primary synchronization signal
      • Secondary synchronization signal
      • Reference signals
  8. System Information
    • Downlink reference signal details
    • Master Information Block on PBCH
    • System Information on DL-SCH
  9. Random Access Procedures and EPS Bearer Setup
    • Random access preamble transmission to eNodeB
    • Random access response from eNodeB
    • Resource allocation and contention resolution
    • Signaling on PDCCH
    • Hybrid ARQ
    • RRC Connection Setup and EPS Bearer Setup
  10. Uplink Channels and Signals
    • Uplink physical channels and signals
    • PU-SCH: Physical Uplink Shared Channel
    • Uplink assignment signaling on PDCCH
    • Uplink frequency hopping
    • PUCCH
  11. LTE Mobility and MIMO Introduction
    • Intra MME Handover over the X2 interface
    • RRC States
    • MIMO Basics
      • Transmit diversity
      • Spatial multiplexing
      • Beamforming
  12. Downlink and Uplink MIMO in LTE
    • Downlink MIMO modes
      • Transmit diversity
      • Spatial multiplexing
      • Cyclic delay diversity
      • Beam forming
    • Spatial multiplexing downlink transmitter chain
      • Code book based precoding
    • Uplink MIMO
      • Uplink transmit antenna selection
      • Multi-user MIMO
  13. eNodeB and UE Performance Requirements
    • eNodeB modulation quality measurements
    • eNodeB performance requirements
    • UE performance requirements
  14. UE Certification and Field Trials
    • LTE terminal testing stages
    • LTE terminal certification
    • LTE field trial scenarios