In this paper the trade-off between time diversity and the inter-carrier interference (ICI) in an OFDM based MC-CDMA system is discussed. Our approach is to partially shift each spectrum of an OFDM symbol at the transmitter by using different phase shifts in the time domain at different antennas after the OFDM modulation. The summary signal at the receiver has a wider Doppler spectrum as the re...

We establish the optimal diversity-multiplexing (DM) tradeoff of coherent time, frequency, and time-frequency selective-fading multiple-input multiple-output (MIMO) channels and provide a code design criterion for DM tradeoff optimality. Our results are based on the new concept of the “Jensen channel” associated to a given selective-fading MIMO channel. While the original problem seems analytic...

Orthogonal Frequency Division Multiplexing (OFDM) has become a very popular method for high data rate wireless communications because of its advantages over single carrier modulation schemes on multi-path, frequency selective fading channels. However, inter-carrier interference due to Doppler frequency shifts, and multipath fading severely degrades the performance of OFDM systems. Estimation of...

Abstract In direct sequence code division multiple access (DS-CDMA), when small spreading factor (SF) is used to achieve high speed transmissions an average bit error rate (BER) performance severely deteriorates due to severe inter-path interference (IPI) in a frequency-selective fading channel. The authors proposed a decision feedback chip-level maximum likelihood detection (DF-CMLD) that can ...

In this paper, we propose an enhanced decoding method to improve the performance of the quasi orthogonal (QO)-space frequency block coding (SFBC) in frequency selective fading channel environment. Generally, QO-SFBC obtains full diversity gain with more than two transmit antennas by using the constellation rotation in flat fading channel. However, QO-SFBC provides less diversity gain in frequen...

The partial parallel interference cancellation (PPIC) scheme can give an optimal IC by adding a partial cancellation weight (PCW) to each interference cancellation path, in which case the PCW is a fraction of one and reflects the reliability of the tentative decision. Then, that the fuzzy-based PPIC (FB-PPIC) outperforms the conventional PIC and constant weight PPIC over flat fading channels ha...

This paper analyzes the spectral efficiency (total channel capacity per subband) of randomly-spread synchronous multicarrier code-division multiple-access (MCCDMA) channel subject to frequency-selective fading in the asymptotic regime of number of users and bandwidth going to infinity with a constant ratio. We analyze the spectral efficiency for uplink and downlink conditioned on subcarrier fre...

Recently, we proposed space-time block coded-joint transmit/receive antenna diversity (STBC-JTRD) for narrow band transmission in a frequency-nonselective fading channel; it allows an arbitrary number of transmit antennas while limiting the number of receive antennas to 4. In this paper, we extend STBC-JTRD to the case of frequency-selective fading channels and propose frequency-domain STBC-JTR...

Orthogonal Frequency Division Multiplexing (OFDM) has become a very popular method for high data rate wireless communications because of its advantages over single carrier modulation schemes on multi-path, frequency selective fading channels. However, inter-carrier interference due to Doppler frequency shifts, and multipath fading severely degrades the performance of OFDM systems. Estimation of...

In this thesis, we first build up a wireless communication simulator including Gray coding, modulation, different channel models (AWGN, flat fading and frequency selective fading channels), channel estimation, adaptive equalization, and demodulation. Next, we test the effect of different channel models to the data and image in receiver with constellation and BER (bit error rate) plots under QPS...