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Single Carrier Orthogonal Multiple Access Technique for Broadband Wireless Communications
DISSERTATION
Degree of DOCTOR OF PHILOSOPHY (Electrical Engineering)
POLYTECHNIC UNIVERSITY
by
Hyung G. Myung
January 2007
An Abstract
Single Carrier Orthogonal Multiple Access Technique for Broadband Wireless Communications
by
Hyung G. Myung
Advisor: David J. Goodman
Submitted in Partial Fulfillment of the Requirements
For the Degree of Doctor of Philosophy
January 2007
Broadband wireless mobile communications suffer from multipath frequency-selective fading.
Orthogonal frequency division multiplexing (OFDM) and orthogonal frequency division
multiple access (OFDMA), which are multicarrier communication techniques, have become
widely accepted primarily because of its robustness against frequency selective fading channels.
Despite the many advantages, OFDM and OFDMA suffer a number of drawbacks; high peakto-
average power ratio (PAPR), a need for an adaptive or coded scheme to overcome spectral
nulls in the channel, and high sensitivity to frequency offset.
ix
Single carrier frequency division multiple access (SC-FDMA) which utilizes single carrier
modulation at the transmitter and frequency domain equalization at the receiver is a technique
that has similar performance and essentially the same overall structure as those of an OFDMA
system. One prominent advantage over OFDMA is that the SC-FDMA signal has lower PAPR.
SC-FDMA has drawn great attention as an attractive alternative to OFDMA, especially in the
uplink communications where lower PAPR greatly benefits the mobile terminal in terms of
transmit power efficiency and manufacturing cost. SC-FDMA is currently a working assumption
for the uplink multiple access scheme in 3rd Generation Partnership Project Long Term
Evolution (3GPP LTE).
In this thesis, we first give a detailed overview of an SC-FDMA system. We then analyze
analytically and numerically the peak power characteristics and propose a peak power reduction
method that uses symbol amplitude clipping technique. We show that subcarrier mapping
scheme and pulse shaping are significant factors that affect the peak power characteristics and
that symbol amplitude clipping method is an effective way to reduce the peak power without
compromising the link performance. We investigate multiple input multiple output (MIMO)
spatial multiplexing technique in an SC-FDMA system using unitary precoded transmit eigenbeamforming
with practical limitations. We also investigate channel-dependent scheduling for an
uplink SC-FDMA system taking into account the imperfect channel information in the form of
feedback delay. To accommodate both low and high mobility users simultaneously, we propose a
hybrid subcarrier mapping method using orthogonal code spreading on top of SC-FDMA and
show that it can have higher capacity gain than that of conventional subcarrier mapping scheme. |
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发表于 2008-10-14 12:08:43
