Lab #5: LTV Channels

Introduction

The purpose of a communication system is to compensate the hostile effect of the channel between transmitter and receiver. In practice the communication channel is always time-variant. Thus, it is vitally important for a communications engineer to understand such channels to be able to design counter-measures for them. The goal of this laboratory exercise is to gain understanding of LTV system characterization and the constraints posed by such a system to communication receiver design.

In this laboratory work we investigate Linear Time-Variant (LTV) communication channels, their system functions, and information that can be extracted from those functions, such as coherence time, delay spread, Doppler spread.
 
 

Material

Material for the lab work  in pdf, 1.2 Mb. (Lab exercises updated slightly)
Hints for the lab, in pdf.
 
 

Prerequisites

• S-72.232 Radio Communications Systems
• Knowledge of MATLAB (or willingness to learn)
• Possibly useful, but not necessary: S-72.227, S-88.200, S-88.145, Tik-61.246, Tik-61.238

Literature

• Lecture notes of S-72.232 Radio Communication Systems
• B. Sklar, "Rayleigh Fading Channels in Mobile Digital Communication Systems, Part I: Characterization"   A good tutorial, accessible at HUT campus area
• B. Sklar, "Rayleigh Fading Channels in Mobile Digital Communication Systems, Part II: Mitigation"   Also accessible at HUT campus area

• William C. Jakes: Microwave Mobile Communications, USA 1974, Wiley, 642pp
• David Parsons: The Mobile Radio Propagation Channel, 2nd edition, Great Britain 2000, Wiley, 418pp

Some links

• Wireless Communications - Samples and Demos
• Radio Propagation Models - adapted from the material above
• "Design of an n-path Rayleigh fading channel model in the DSP Canvas simulator", a Master's Thesis from KTH, Sweden
• A wireless communications course at Chalmers University of Technology, Sweden.  Check out the project works in this course.
• Elektrobit   Manufacturer of the radio channel simulator used in the lab work
• MATLAB Signal Processing Toolbox on-line Documentation

Teaser

Below you see a segment of a real-world time-variant impulse response measured in Tapiola, Espoo. However, in this laboratory exercise we don't drag ourselves to Tapiola with actual channel sounding equipment, but use a hardware-based radio channel simulator instead (with 50 gigaFLOPS DSP computing power, not your average desktop PC). Channel output is measured with high speed A/D sampling boards, saved to a file and later processed with MATLAB. Other high tech used in this lab includes: 100 Msps Arbitrary Waveform Generator (AWG), spectrum analyzer, GSM tester.
 

Updated  16-09-2002/Lju