Fundamentals of LTE

Course 223

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Understanding the evolution of wireless data transmission from 3G to 4G technologies is critical to today’s commercial component and system vendors. This comprehensive three day program covers the key technologies in a clear and concise manner.

The course begins by covering fundamental digital signal concepts. We look at the relationship between complex digital signals and the hardware (specifically complex envelope, quadrature modulators and demodulators). This will also be used to provide insight into the modulation schemes chosen by these standards. Various reasons why certain decisions have been made by the 3GPP standards body will be provided. A practical pulse shaping filter discussion will be presented. Channel impairments such as noise (AWGN) and multipath fading are introduced. Forward error-control coding (convolutional, Turbo, etc) and the Viterbi decoder will be discussed in detail, as well as functionality partitioning between hardware and software.

Moving on, we will present the components of a WCDMA system. We will start with the protocol overview and the where certain functions are located (and why) in the network. We discuss the purpose of the physical channels and the issues to be aware of when designing a RAKE receiver to demodulate them. We then point out the issues related to WCDMA to support packet data and introduce HSDPA & HSUPA. A RAKE receiver will be discussed and specific implementation details such as ADC location, dedicated HW and SW control will be provided. PN code sequences will be discussed as well as the method used to shift the sequence. A block diagram of the NodeB transceiver will be provided to show location of ADC, transport channel multiplexing, closed loop operations, etc. A discussion on why certain choices were made in the implementation partitioning.

Finally, we discuss the components of the LTE system. We will start with the protocol overview and the where certain functions are located (and why) in the network. We discuss the purpose of the physical channels and the issues to be aware of when designing a receiver. The OFDM transceiver will be discussed as well as options needed to be implemented to support the various BWs defined. We will discuss the implementation partitioning to support link adaptation. Antenna diversity details around the LTE standard will be provided to introduce the various modes of operation that need to be supported.

Learning objectives

Upon completing the course you will be able to:

  • understand multipath fading issues when deploying WCDMA and LTE.
  • describe receive antenna diversity techniques and issues surrounding their implementation.
  • compare the implementation complexity of TDMA, CDMA and OFDMA as the supported data rates increase.
  • Know the issues and obstacles related to multiple access schemes and how to overcome them.
  • address issues pertaining to timing tracking and channel estimation.
  • describe the expected UE behavior with regards to cell search.
  • address the timing requirements for closed loop power control.
  • describe various LTE system scenarios such as random access and link adaptation.

Target Audience

Engineers and technical managers who need a technical understanding of third and fourth generation cellular data transmission techniques will benefit from this course. Knowledge of fundamental signal processing concepts (Fourier transform, etc.) is assumed.


Day One

Digital Modulation Overview
 • Complex envelope representation of signals and systems - Relationship to HW components - Impact of PA non-linearity (spectral reqrowth)Impact of PA non-linearity (spectral reqrowth) - Gain & Phase imbalance • Digital modulation overview - BPSK, QPSK, 16QAM & 64QAM - Block diagrams - Pulse shaping filter selection (Nyquist and Raised Cosine filtering) • System Metrics: BER, SNR, Eb/No definitions
Radio Propagation Characterization
 • AWGN channel • Rayleigh/Rician multipath fading - Background & Practical explanations • Delay spread concept (flat vs. frequency selective fading) - Indoor & Outdoor propagation measurements • Delay spread & coherence bandwidth (outdoor & indoor) • Updated 3GPP Reference Channel Models
Performance Improvement Techniques
 • Forward Error Correction - Convolutional (Viterbi Algorithm, Punctured Coding) - Turbo (Encoder and Decoder) - Interleaver/de-interleaver - advantages & disadvantages • Performance comparisons • Antenna receiver diversity techniques - Switching, Equal Gain, Maximal Ratio, Optimal Combining - Theoretical SNR improvement & BER Performance - Issues to be aware of when implementing spatial diversity
Multipath Mitigation Techniques
 • Explain how different standards resolve multipaths - TDMA vs. CDMA vs. OFDMA solutions

Day Two

3GPP WCDMA System Components (Building Blocks)
 • System Goals (latency, throughput, etc.) • 3GPP Release Overview (Release 99 to Release 9 features) • WCDMA Signaling Channels (UL and DL) - Logical Channels - Physical Channels • WCDMA Protocol Overview - Layer1-PHY, Layer2-MAC, Layer3-RLC functions • High Speed Downlink Packet Access (HSDPA) - HSDPA Physical Channels • High Speed Uplink Packet Access (HSUPA) - HSUPA Physical Channels • PN sequences discussion: m sequences, gold codes, OVSF • NodeB Transceiver block diagram - Spreader & despreader, etc. • RAKE receiver Overall Block Diagram Discussion - RAKE Receiver Signal Processing
3GPP WCDMA System Scenarios
 • Echo profile manager (searcher) - Discussion on sample rate changes • PN time tracking & acquisition • SIR power control - Inner, Outer and Closed Loop - UL and DL Closed Loop Comparison • Pilot symbol aided coherent detection for Channel estimation - What is the timing impact ? • Modulation (HPSK) • Cell search & Handoffs - Expected UE behavior • Paging Discussion - Comparison of EIA/TIA-95, CDMA2000 and WCDMA Paging Protocols - Power Consumption conclusion • Call Flow Diagrams - Mobile Originated (MO) Call - Mobile Terminated (MT) Call • Network Architecture (NodeB, Radio Network Controller, Core Network) - Partitioning of Protocol Stack Across Network • Security Architecture - Ciphering Examples - Integrity Protection - Confidentiality - WCDMA & HSDPA examples

Day Three

LTE System Components (Building Blocks)
 • System Goals (latency, throughput, etc.) - Discussion on trend toward IP services • LTE Signaling Channels (UL and DL) - Logical Channels - Physical Channels • Network Architecture (E-UTRAN, EPC) - Element Interfaces • Protocol Architecture (RRC, RLC, MAC) - Partitioning of Protocol Stack across Network • OFDM Principles and details for LTE - Transmission & modulation (subcarrier, IFFT, S/P, etc.) - Sub-carrier discussion - Reception and Demodulation (FFT, P/S, etc.) - Purpose and values of Cyclic Prefix (CP) - OFDM Receiver block diagrams • FDD & TDD Modes