(Georgia Institute of Technology, 2009-07)
Pirkl, Ryan J.; Durgin, Gregory D.
A wireless channel sounder based upon the conventional
spread spectrum sliding correlator implementation uses
unfiltered pseudo-random noise (PN) at both the transmitter
and receiver to generate a time-dilated copy of the channel’s
impulse response. However, in addition to this desired impulse
response, the sliding correlator also produces a noise-like, wideband
distortion signal that decreases the measurement system’s
dynamic range. Careful selection of the sliding correlator’s lowpass
filter can significantly reduce this distortion, but no amount
of filtering will remove it completely. In contrast, using filtered
PNs at both the transmitter and receiver enables one to remove
this distortion in entirety and realize a measurement system
whose dynamic range closely approximates the theoretical ideal
for spread spectrum systems.
(Georgia Institute of Technology, 2009-04)
Pirkl, Ryan J.; Durgin, Gregory D.
Off-the-horizon propagation severely degrades the
accuracy of any field reconstruction technique that presupposes a
two-dimensional (2-D) wireless channel. Therefore, employing the
2-D cylindrical wave expansion (CWE) to interpolate perimeter
channel measurements into a planar region often yields poor
results. Here, the CWE is adapted for real-world radio channel
measurements by selectively combining the basis functions from
two similar CWEs. Using both simulated and experimental measurement
data, it is shown that this conjoint CWE yields a more
accurate reconstruction than the conventional CWE yet requires
no additional measurements. Thereby, this field reconstruction-
based channel imaging technique will enable more complete
investigations of the wireless channel’s spatial behavior and allow
researchers to isolate and characterize the actual mechanisms
underlying radio wave propagation.
(Georgia Institute of Technology, 2008-09)
Pirkl, Ryan J.; Durgin, Gregory D.
The sliding correlator technique remains one of the most versatile and effective methods for sounding the radio propagation channel in next-generation wireless systems. Despite their utility, there has never been a comprehensive set of metrics and rules for the design of a sliding correlator channel sounder. This paper presents quantitative guidelines for balancing the many system parameters to achieve optimal levels of temporal resolution, dynamic range, processing. gain, and Doppler resolution. The design procedure presented at the end of the paper will allow researchers to probe the new radioscapes that result as wireless systems are pushed to higher carrier frequencies, wider bandwidths, multiple antennas, and ubiquitous operation.