PROJECT OBJECTIVE:
The objective of this research is to design and analyze an OFDM system for
mobile communications applications.
GENERAL DESCRIPTION:
High data rate communication systems can experience severe distortion when
used over mobile channels. To make the system relatively immune to some of those
distortions, a particular type of signal design referred to as orthogonal
frequency division multiplexing (OFDM) has been suggested. In this research
project, we propose to study the performance of OFDM when used in mobile
systems. This mobility makes it more difficult to design an efficient receiver,
and we propose to compare many receiver designs to one another.
TECHNICAL ABSTRACT:
This proposal is concerned with the design and performance analysis of both
conventional OFDM and multicarrier direct sequence (DS) communications systems.
These two systems are similar in that they both employ multiple subcarriers, and
thus neither one requires a contiguous frequency band over which to operate.
This makes the deployment of such waveforms very flexible, especially in the
presence of in-band narrowband interference. Further, if the total bandwidth
occupied by these waveforms exceeds the coherence bandwidth of the channel, they
are each capable of providing diversity enhancement.
Most previous studies on OFDM have been for either fixed wireless systems or
pedestrian-speed systems. Over the past two years, we have initiated research on
the use of OFDM for systems experiencing high degrees of mobility. This means
that the effects of Doppler shifts across the subcarriers becomes a fundamental
consideration in both system design and performance analysis. Other key research
issues are the effects of channel estimation errors, the classical high
peak-to-average power ratio that such systems are known to suffer from, and the
relative performance of such signals when operated in a CDMA mode.
Note that our proposed emphasis on high mobility is especially meaningful given
the popularity that fixed wireless/low mobility OFDM systems have experienced
(e.g., 802.11A). This is because a goal of system designers has been to merge
digital cellular systems with so-called “last-mile” systems. Since some of these
last mile systems already employ OFDM, if OFDM can be shown to be competitive
with cellular systems such as CDMA, the merger of cellular and last mile designs
will be that much easier.
PARTICIPATING FACULTY:
The following CWC faculty are participating in this research project: Larry Milstein(lead PI),
Truong Nguyen, John Proakis, James Zeidler.
Affiliated Faculty
CoRe Research Projects