  The line of sight direction in the redshifted 21-cm signal coming from the
cosmic dawn and the epoch of reionization is quite unique in many ways compared
to any other cosmological signal. Different unique effects, such as the
evolution history of the signal, non-linear peculiar velocities of the matter
etc will imprint their signature along the line of sight axis of the observed
signal. One of the major goals of the future SKA-LOW radio interferometer is to
observe the cosmic dawn and the epoch of reionization through this 21-cm
signal. It is thus important to understand how these various effects affect the
signal for it's actual detection and proper interpretation. For more than one
and half decades, various groups in India have been actively trying to
understand and quantify the different line of sight effects that are present in
this signal through analytical models and simulations. In many ways the
importance of this sub-field under 21-cm cosmology have been identified,
highlighted and pushed forward by the Indian community. In this article we
briefly describe their contribution and implication of these effects in the
context of the future surveys of the cosmic dawn and the epoch of reionization
that will be conducted by the SKA-LOW.
