Pilot power optimization for channel estimation in OFDM system

For Orthogonal Frequency Division Multiplexing (OFDM) system, training preamble for channel estimation is studied when null subcarriers are embedded in each OFDM symbol. The optimal training preamble that minimize the mean squared channel estimation error is numerically found by casting the design problem into a semidefinite programming problem. A design example under the same setting as IEEE802.11a is provided to verify the efficacy of our proposal as well as to show that the preamble of IEEE802.11a is almost optimal.