Advanced pilot design procedure based on HS algorithm for OFDM-IDMA system

The direct effect of the pilot positions to the channel estimation performance gives an opportunity for minimising the estimation errors in multicarrier transmission technologies. To this end, harmony search (HS) algorithm is proposed for optimising the pilot distribution pattern in order to increase the performance of least squares estimator employed in orthogonal frequency division multiplexing-interleave division multiple access (OFDM-IDMA) system. Besides, the upper bound of mean square error (MSE) utilised as the fitness function of HS algorithm is obtained by using Gershgorin disc theorem to get rid of matrix inversion process required in MSE calculation. In the simulations, the authors' proposed HS-based pilot optimisation technique proves to be an effective way of pilot design for OFDM-IDMA system by providing a clear performance superiority over the other considered pilot placement strategies.