Efficient pilot allocation for sparse channel estimation in UWB OFDM systems.

•Pilot allocation scheme is the first time to jointly design in time and frequency for compressive sensing based channel estimation.•Three efficient pilot allocation methods are proposed for pilot-assisted sparse channel estimation.•Three pilot allocation methods have lower complexity than the state-of-the-art algorithm.•Deterministic greedy algorithm and simulated annealing algorithm achieve a better performance with a lower complexity than the state-of-the-art algorithm.•The negligible complexity makes simplified deterministic greedy algorithm become an effective method for the situation where the temporal dimension is considered.