Training Design for Multipath Channel and Frequency-Offset Estimation in MIMO Systems
IEEE Transactions on Signal Processing
A comparison of pilot-aided channel estimation methods for OFDMsystems
IEEE Transactions on Signal Processing
Optimal training design for MIMO OFDM systems in mobile wireless channels
IEEE Transactions on Signal Processing
Optimal training signals for MIMO OFDM channel estimation
IEEE Transactions on Wireless Communications
IEEE Transactions on Information Theory
Pilot tone selection for channel estimation in a mobile OFDM system
IEEE Transactions on Consumer Electronics
Wireless Personal Communications: An International Journal
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We consider the problem of pilot design for channel estimation in multiple-input multiple-output (MlMO) orthogonal frequency division multiplexing (OFDM) systems in the presence of virtual carriers. The design criterion is the average mean-square error (MSE) of the least square (LS) estimates of the channel frequency response over tlite data carriers. To maximize bandwidth efficiency, the number of pilots is set to its minimum which is equal to the number of unknown channel coefficients. Both the phase shift orthogoual and disjoint pilot schemes are investigated. For a given pilot placement, a closed-form expression for the pilot power distribution for the disjoint scheme is provided. It is fonnd that the optimal power distribution allocates less power to the pilots that are close to the virtual carriers. Pilot placement is obtained using an exhaustive search. The latter is too complex in systems with large number of subcarriers. A suboptimum pilot placement design for the disjoint pilot scheme is presented. It is shown that, unlike fully loaded systems where the two pilot design schemes have similar performance, in the presence of virtual carriers thl! optimal disjoint scheme not only has lower complexity but also yields more accurate channel estimation and bit error rate performance.