In SFN (Single Frequency Network) broadcasting systems the equivalent CIR (Channel Impulse Response) can be very long, typically with a sparse nature. This means that the equivalent CIR
has several clusters of paths, each one associated to
the CIR between a given transmitter and the receiver.
These clusters have several multipath components and
are typically well separated in time. In this paper we
consider OFDM-based (Orthogonal Frequency Division
Multiplexing) broadcasting systems with SFN operation
and we propose an efficient channel estimation method
that takes advantage of the sparse nature of the equivalent
CIR. For this purpose, we employ low-power training
sequences and we employ an iterative receiver with joint
detection and channel estimation. The receiver can know
the location of the different clusters that constitute the
overall CIR or not. Our performance results show that we
can have excellent performance, close to the performance
with perfect channel estimation, even with resort to
low-power training blocks and also for the case where
the receiver does not know the location of the different
clusters that constitute the overall CIR.