Conference Paper

# Excessively Long Channel Estimation for CDD OFDM Systems Using Superimposed Pilots

Dept. of Electr. & Comput. Eng., Univ. of Western Ontario, London, ON, Canada

DOI: 10.1109/icc.2011.5962561 Conference: Communications (ICC), 2011 IEEE International Conference on Source: IEEE Xplore

- Citations (14)
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**ABSTRACT:**Cyclic delay diversity (CDD) is a low-complexity standard-conformable transmit diversity scheme for coded orthogonal frequency division multiplexing (OFDM) systems. However, it makes channel estimation more challenging due to the increased frequency-selectivity of the equivalent single-input single-output channel. In this paper, we propose a novel CDD-OFDM scheme with pilot-aided channel estimation for any number of transmit antennas. By alternating and optimizing the cyclic delay parameter over adjacent OFDM symbols, we design a simple yet efficient channel estimation scheme and illustrate its excellent performance for the DVB-T application.IEEE Transactions on Wireless Communications 04/2009; · 2.42 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**Cyclic delay diversity is a simple, yet effective, transmit diversity scheme for multicarrier based transmissions employing coherent digital linear modulation schemes. It is shown that, for satisfactory operation, the scheme requires additional channel estimation overhead compared to single antenna and traditional space-time coded transmissions owing to the inherent increase in frequency selective fading. The authors analyse the additional channel estimation overhead requirement for a Hiperlan #2 style system with two transmit antennas operating in a NLOS indoor environment. The analysis shows that an additional overhead of 500% is required for the candidate system compared to a single antenna system. It is also shown that by employing differential modulation the channel estimation overhead can be eliminated with significant performance improvement compared to a system employing a practical channel estimation scheme. This novel combination, termed 'differentially modulated cyclic delay diversity', is shown to yield a highly spectral efficient, yet simple transmit diversity solution for multi-carrier transmissions.IEE Proceedings - Communications 09/2005; · 0.32 Impact Factor -
##### Conference Paper: Parameter optimization, interleaving and multiple access in OFDM with cyclic delay diversity

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**ABSTRACT:**Cyclic delay diversity is a simple transmit diversity technique for coded OFDM systems with multiple transmit antennas. It does neither require an extended guard interval nor modifications of the standard OFDM receiver. We discuss the problem of choosing the cyclic delays and propose a solution which enables us to exploit the full spatial diversity in flat fading and. frequency-selective channels with unknown delay spread. As a result, the spatial diversity is transformed into frequency diversity between neighbouring subcarriers. This imposes certain restrictions on the channel coding and interleaving scheme. Furthermore, we address multi user aspects and propose an interleaving and multiple access strategy which guarantees that all users obtain the maximum possible diversity advantage using FEC codes with a limited constraint length.Vehicular Technology Conference, 2004. VTC 2004-Spring. 2004 IEEE 59th; 06/2004

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