ECE 6634 Multi-Channel Communications | ECE | Virginia Tech


Course Information


In-depth study of modern multi-channel communications techniques, primarily multi-antenna systems (known as multiple-input multiple-output or MIMO) and Orthogonal Frequency Division Multiplexing (OFDM). Specifically the course examines multi-antenna techniques such as transmit and receive diversity, beamforming (including eigen-beamforming), and spatial multiplexing. Within the area of OFDM we examine modulation/demodulation, carrier bit loading, mitigating multipath, frequency-domain equilization, peak-to-average power reduction, and frequency offset mitigation. As time permits we will also investigate a third multi-channel technique know as multi-user scheduling or packet access networks.

Why take this course?

OFDM has become ubiquitous as a technique for wireless communications. However, since it is an advanced technique we only touch on the topic in the introductory graduate level digital communications course, 5654. MIMO techniques are also fast becoming standard in wireless communications and are still the subject of substantial research. Thus, these two techniques which are introduced in earlier courses, require a more in-depth study.


5605, 5654

This course requires an in-depth background in communication theory as well as a strong background in stochastic processes. The relevant communication theory can be learned only at the graduate level or above. Stochastic processes are not introduced until the first year of graduate studies. These 5000-level prerequisites justify its level.

Major Measurable Learning Objectives

  • Create and use a channel model appropraite for multi-antenna or OFDM simulation studies.
  • Analyze the performance (via statistical analysis and/or simulation) of a receive or transmit diversity system in the presence of independent or correlated fading with either Nakagami or Rayleigh fading.
  • Determine the optimal beamforming weights for a linear or circular array with max Signal-to-Noise Ratio (SNR), max Signal-to-Interference Ratio (SINR), Minimum Mean Square Error (MMSE) or max Signal-to-Interference Ratio (SIR) criteria.
  • Design and analyze (via statistical analysis and/or simulation) a multi-antenna system for increasing spectral efficiency using spatial multiplexing.
  • Analyze (via statistical anlaysis and/or simulation) the performance of a system emplying orthogonal space-time block codes.
  • Analyze the performance (via statistical analysis and/or simulation) of an OFDM system in flat and frequency selective channels, including the effect of Doppler spread, Inter-carrier Interference (ICI) and peak-to-average reduction techniques.
  • Design a cyclic prefix or guard interval for multigating ICI and Inter-Symbol Interference (ISI) in an OFDM system.

Course Topics


Percentage of Course

1. Multi-antenna and OFDM Channel Models 5%
2. Channel Capacity 5%
3. Diversity and Fading - Performance analysis 10%
4. Beam-forming - Optimal weights; adaptive algorithms 10%
5. Orthogonal Space-Time Block Codes and S-T Trellis Codes 10%
6. Spatial Multiplexing 5%
7. Hybrid MIMO Techniques 5%
8. OFDM - Introduction and performance analysis 10%
9. Degradation of OFDM due to Doppler-induced Inter-Carrier Interference 10%
10. Multipath, the Cyclic Prefix and guard intervals 10%
11. Adaptive Modulation and Bit Loading 5%
12. Peak-to-Average Reduction 5%
13. OFDMA 5%
14. Applications 5%