LTE Air Interface

3 days

Download brochureThe course focuses on the LTE air interface and explains in great detail all its functions and processing blocks. It contains logically structured topics covering E-UTRAN architecture, key techniques used in E-UTRA such as OFDMA and SC-FDMA, LTE Layer 1 processing, Layer 2 and 3 functions and all the important radio interface procedures. Special attention is given to the LTE PHY layer (Layer 1), where the architecture of the radio frame is examined with all the corresponding channels, resource mapping options and procedures. A thorough overview of RRC, PDCP, RLC and MAC protocols is given, where MAC operation is especially highlighted due to its importance in the E-UTRAN operation.

The course utilizes a number of hands-on practical exercises using the state-of-the art LTE PHY Lab – a Link Level Simulator applied to observe signals, channels and frames of the LTE air interface.

Introduction to E-UTRA

• Evolution steps of the 3GPP systems, the goals for LTE
• E-UTRA and Evolved Packet Core network architecture
• Nodes: UE, eNB, SGW, MME
• Interfaces: Uu, X2, S1, S11
• LTE bandwidths, bit rates and UE categories
• Summary of radio access techniques
• E-UTRAN protocol stack
• Alternative systems: Mobile WiMAX

Overview of OFDMA and SC-FDMA

• Fundamentals of multipath propagation (selectivity in time, frequency and space)
• Basics of OFDM transmission, subcarriers, cyclic prefix, IFFT/FFT processing
• OFDMA and SC-FDMA as extension of OFDM
• Multiple access with OFDMA and SC-FDMA
• Advantages and disadvantages of OFDM, OFDMA and SCFDMA

LTE Downlink PHY Layer Processing

• Downlink channel architecture (radio bearers, logical, transport and physical channels)
• Downlink FDD frame structure and its elements (sub-frames, slots, resource elements, physical resource blocks, PHY channels and signals)
• PHY channels and signals including: PBCH, PCFICH, PHICH, PDCCH, PDSCH, Primary and Secondary Synchronization Signals, Reference Signals)
• Various antenna pilot patterns and Reference Signals for MIMO
• MIMO processing in 3GPP-LTE Release 8
• Placement of control channels (PCFICH, PHICH, PDCCH) in the control region
• Downlink processing chain including channel coding and rate matching, modulation, layer mapping, pre-coding, resource element mapping and OFDMA signal generation
• Downlink control information, PDCCH formats, mapping of DCI into PDCCH
• PDCCH blind decoding
• PHICH assignment

LTE Uplink PHY Layer Processing

• Uplink channel architecture (radio bearers, logical, transport and physical channels)
• Uplink FDD frame structure and its elements (sub-frames, slots, resource elements, physical resource blocks, PHY channels and signal)
• PHY channels and signals including PUCCH, PUSCH, SRS, DRS, PRACH
• PUCCH formats
• Creation of SRS
• Random Access Preamble formats
• Location of PRACH in the uplink frame
• Uplink processing chain including channel coding and rate matching, modulation, resource element mapping and SCFDMA signal generation
• PUSCH hopping procedure and UE SRS procedure

LTE MAC Layer

• MAC architecture and functions
• Priority handling and multiplexing
• Hybrid ARQ (HARQ) operation (Chase combining and incremental redundancy)
• HARQ processes and processing HARQ ACKs and NACKs by PHY layer
• Discontinuous Reception (DRX) and Semi-Persistent Scheduling (SPS)
• Adaptive Modulation and Coding
• Timing Relationship and Timing Advance
• Scheduling

LTE RRC, PDCP and RLC Layers

• RRC procedures including system info broadcasting, paging, RRC connection establishment, security establishment, NAS message transport and RRC connection reconfiguration
• Types of radio bearers
• RRC connection establishment: from RRC Idle to RRC Connected
• PDCP architecture and functions: robust header compression, ciphering and integrity protection
• RLC architecture and functions including segmentation / concatenation, retransmissions
• RLC modes: Transparent, Unacknowledged, Acknowledged
• Example LTE data flow and transport block sizes

Radio Interface Procedures

• Downlink resource assignment, resource allocation types, resource block grouping
• Modulation and transport block size determination
• Synchronization and system info acquisition
• RRC measurement reporting
• UE mobility states
• Measurements: RSRP, RSSI, RSRQ
• Overview of E-UTRA reporting events
• Cell selection / reselection
• Random Access procedure
• MIMO feedback reporting (PMI and RI)
• CQI, PHR and BSR reporting
• Uplink power control, open loop and closed loop, types of transmit power commands
• Downlink power control - operation and parameters
• X2 interference management and load balancing procedures

LTE Air Interface Demo and Experiments (tool-based)

• OFDMA and SC-FDMA waveforms
• Chosen eNB and UE signals and PHY channels shown in the time and frequency domain
• Complete downlink and uplink radio frame shown as time-frequency grid