Beyond 3G Receivers Design
Date Issued
2003-07-31
Date
2003-07-31
Author(s)
DOI
912213E002102
Abstract
In the communications systems beyond
the third generation (B3G) mobile
communications, the primary concept
leads to develop the efficiently
utilization of spectrum to provide the
higher data rate services than IMT-2000
and to develop the programmable
systems adaptive to multiple
communications systems, such as the
wide-band CDMA in IMT-2000, OFDM
in IEEE 802.11a [1] and IEEE 802.11g,
the Bluetooth technologies.
In the first year of the project, by
inheriting the properties of the
frequency-domain approach [2] to avoid
MAI in the asynchronous multiuser
communications and sharing the
rationale behind OFDM systems to
mitigate ISI, we propose an
asynchronous multiuser communications
system (i.e. the frequency-domain
orthogonal multiuser communications
with inverse transformation
(FDOMC-IT)) over frequency-selective
slowly fading channels such that the
optimal demodulation with similar
complexity to point-to-point
communications is possible. In addition,
by spreading the symbol energies to the
whole transmission frequency band, we
further introduce another asynchronous
multiuser communications system (i.e.
the frequency-domain orthogonal
multiuser communications with direct
spreading (FDOMC-DS)) to utilize the
frequency diversity gain. These
proposed systems not only mitigate MAI
and ISI efficiently with simple
complexity but also are flexible for
variable rates transmission to suggest
their applications to practical
multimedia services.
Applying the composite hypothesis
testing procedure, we further introduce
the maximum a posteriori probability
(MAP) symbol synchronization in the
wireless communications systems with
statistical channel information over
frequency-selective slowly fading
channels. This proposed estimation takes
the presence of interference due to
frequency-selective channels into
account and efficiently utilizes the
inherited frequency-diversity to combat
the channel fading impairment. By
mathematical analysis, we prove the
fundamental condition to have a
consistent symbol synchronizer over
frequency-selective slowly fading
channels when the channel impulse
response is unknown. We further
conduct simulations to justify its
performance considering the practical
implementation with a finite number of
timing candidates and extend its
applications to the case without training
symbols. This proposed timing
estimation considers more generalized
scenarios with feasible complexity and
therefore could be extensively applied in
many practical communications
systems.
With the introduction of the
frequency-domain orthogonal multiuser
communications systems (FDOMC) and
the optimal timing estimation over
frequency-selective slowly fading
channels, it is promised to design the
high-rate B3G systems for multi-media
services with simple complexity.
Subjects
B3G
FDOMC
Optimal
Timing Estimation
Timing Estimation
and
Frequency-selective slowly fading
channels
Frequency-selective slowly fading
channels
Publisher
臺北市：國立臺灣大學電信工程學研究所
Type
report
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