  Channel Estimation is a major problem encountered by receiver designers for
wireless communications systems. The fading channels encountered by the system
are usually time variant for a mobile receiver. Besides, the frequency response
of the channel is frequency selective for urban environments where the delay
spread is quite large compared to the symbol duration. Estimating the channel
is essential for equalizing the received data and removing the Inter-Symbol
Interference (ISI) resulting from the dispersive channel. Hence, conventional
transceivers insert pilot symbols of known values and detect the changes in it
in order to deduce the channel response. Because these pilots carry no
information, the throughput of the system is reduced. A Novel modulation scheme
is presented in this work. The technique depends on using a carrier signal that
has no fixed frequency, the carrier tone sweeps the band dedicated for
transmission and detects the transfer function gain within the band. A carrier
signal that is Frequency Modulated (FM) by a periodic ramp signal becomes
Amplitude Modulated (AM) by the channel transfer function, and thus, the
receiver obtains an estimate for the channel response without using pilots that
decrease the systems throughput or data rate. The carrier signal itself acts as
a dynamic frequency domain pilot. The technique only works for constant energy
systems, and thus it is applied to PSK transceivers. Mathematical formulation,
transceiver design and performance analysis of the proposed modulation
technique are presented.
