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|Title: ||OFDM-IDMA wireless communication systems|
|Other Titles: ||Zheng jiao pin fen fu yong jiao zhi qu fen duo zhi jie ru wu xian tong xin xi tong|
|Authors: ||Li, Yueqian (李悦騫)|
|Department: ||Department of Electronic Engineering|
|Degree: ||Master of Philosophy|
|Issue Date: ||2007|
|Publisher: ||City University of Hong Kong|
|Subjects: ||Orthogonal frequency division multiplexing.|
Wireless communication systems.
|Notes: ||CityU Call Number: TK5103.484 .L5 2007|
xiii, 77 leaves : ill. 30 cm.
Thesis (M.Phil.)--City University of Hong Kong, 2007.
Includes bibliographical references (leaves 72-76)
|Abstract: ||Orthogonal frequency-division multiplexing code-division multiple-access (OFDMCDMA)
also referred as multi-carrier CDMA (MC-CDMA) is a spread-spectrum transmission
technique introduced in 1993. Since then, numerous technical papers about
OFDM-CDMA have been published. OFDM-CDMA is considered to be a promising
candidate for the air interface of the fourth generation (4G) wireless communication systems.
Interleave-division multiple-access (IDMA) is a recently proposed multiple access
scheme, which employs random interleavers as the only method for user separation. As
a particular case of CDMA, IDMA inherits many distinguished features of well-studied
CDMA. Furthermore, it allows a low-cost turbo-type multiuser detection (MUD) algorithm
applicable to the system with large numbers of users, which is crucial for high-rate
multiple access communication.
The work presented in this thesis is completely devoted to the investigation of an
OFDM-IDMA scheme. The proposed scheme employs IDMA instead of CDMA in the
OFDM-CDMA scheme and combines advantages of both OFDM and IDMA. With sufficient
guard intervals, OFDM can completely remove intersymbol interference (ISI).
IDMA with a chip-by-chip (CBC) iterative multi-user detector can overcome both crosscell
and intra-cell multiple access interference (MAI) problems efficiently.
We first present the basic principles of OFDM-IDMA transmitter and receiver. Comparative
studies between OFDM-IDMA and OFDM-CDMA are carried out. We also
compare OFDM-IDMA with IDMA with LLRC algorithm. Thanks to the independent
processing of ISI and MAI, OFDM-IDMA offers better performance than plain IDMA
with LLRC in terms of both bit error rate (BER) and complexity.
Then we derive a simple and effective performance analysis method for OFDMIDMA
based on SNR evolution. To support large number of users and achieve high rates,
we optimize the transmitted power profiles with the aid of the SNR evolution technique.
Several power allocation methods are presented, which are selected according to the system
configurations and channel conditions. The comparisons between OFDM-IDMA
and OFDM-TDMA based on bit-interleaved coded modulation (BICM) are carried out,
which demonstrates a spectral-power efficiency advantage of non-orthogonal multiple
access approaches over orthogonal ones.
The proposed OFDM-IDMA scheme provides a competitive alternative to the conventional
OFDM-CDMA scheme for future high-rate multiuser communications over
multipath fading channels.|
|Online Catalog Link: ||http://lib.cityu.edu.hk/record=b2217920|
|Appears in Collections:||EE - Master of Philosophy |
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