ISSN : 1796-2021
Volume : 3    Issue : 3    Date : July 2008

Channel Correlation Properties in OFDM by using Time-Varying Cyclic Delay Diversity
Simon Plass, Armin Dammann, Gerd Richter, and Martin Bossert
Page(s): 19-26
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This paper analyzes the influence of time-varying cyclic delay diversity (TV-CDD) on the channel
fading correlation properties in orthogonal frequency division multiplexing (OFDM) based systems.
The underlying transmit diversity technique CDD only increases the frequency diversity at the
receiver. In contrast, TV-CDD introduces additionally time diversity which can be exploited without
the need of additional complexity at the receiver. This paper gives investigations regarding the
resulting channel characteristics from TV-CDD and the impact on the system performance. Due to
the increased frequency and time selectivity, an unintended higher channel estimation effort is
possible. Therefore, we analyze the impact of choice of the maximum cyclic delay. We show that the
resulting channel for TV-CDD can be seen as an uncorrelated Rayleigh fading channel (except for
the first sub-carrier) for a large maximum cyclic delay. Furthermore, analysis and simulation results
demonstrate a feasible choice of small time-varying cyclic delays for guaranteeing the standard
conformability of the TV-CDD technique at the receiver without significant performance degradations.

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