Embedded pilot and multi-size OFDM processing for jointly time and frequency selective channels

An embedded pilot signal structure is presented that allows simultaneous processing for time-, and frequency-selective channel variations. The pilot signal is added to an OFDM data signal in the time domain and allows for variable power allocation to the pilot. The structure of the signal shows up as a tone comb in the frequency domain which allows for doppler tracking. It is shown that exact tone interpolation for the data carriers can be achieved as long as the channel's impulse response does not exceed the duration of a period of the pilot signal. Finally, pilots can be allocated in a frequency-division mode to multiple transmitters for MIMO or joint detection applications, avoiding the problem of pilot contamination.