Implementation and Analysis of
Multi-Carrier Synchronization
Techniques

Recap:

multi-carrier systems

· Data is distributed onto multiple carriers

· Localized errors correctible using FEC

· Synchronization errors affect all carriers

· Can not be corrected by FEC

Recap:

Schmidl and Cox synchronization

Twice the same sequence back-to-back

Averaged autocorrelation for Δt=½T_Preamble

|x| and arg(x)

Recap:

GNU Radio

• … a signal processing framework for PCs
• … usable via a graphical interface
• … usable via Python and C++

Implementation

A fast S&C implementation for GNU Radio

Performs the raw S&C calculation and outputs a correlation value normalized to the mean input power

Adds a tag to the sample stream when set thresholds are crossed

Performace evaluation

Compared to …

• … a power based method …
• … a frequency sweep based method …

… when disturbed by …

• … an AWGN channel.
• … a frequency shift.
• … a frequency selective channel.

AWGN

Frequency shift

Frequency selective channel

Hardware test where the LO frequency is estimated

Frequency offset to phase mapping is not unique

Residual CFO error is small

Count the number of samples processed by S&C blocks …

… and compare them to a baseline figure

Usable for WiFi on a Desktop PC

S&C components do not use more than two CPU cores

The software sources are released under the terms of the
GNU GPLv3 license:

github.com/hnez/XFDMSync

This presentation and thesis are released under the terms of the
GNU FDLv1.3:

github.com/hnez/XFDMSync-Report

The presentation slides are available online at:

tut.zerforscht.de/ba