  In this paper, we study networks of discrete-time linear time-invariant
subsystems. Our focus is on situations where subsystems are connected to each
other through a time-invariant topology and where there exists a base-station
whose aim is to control the subsystems into any desired destinations. However,
the base-station can only communicate with some of the subsystems that we refer
to as leaders. There are no direct links between the base-station and the rest
of subsystems, known as followers, as they are only able to liaise among
themselves and with some of the leaders.
  The current paper formulates this framework as the well-known reachability
problem for linear systems. Then to address this problem, we introduce notions
of leader-reachability and base-reachability. We present algebraic conditions
under which these notions hold. It turns out that if subsystems are represented
by minimal state space representations, then base-reachability always holds.
Hence, we focus on leader-reachability and investigate the corresponding
conditions in detail. We further demonstrate that when the networked system
parameters i.e. subsystems' parameters and interconnection matrices, assume
generic values then the whole network is both leader-reachable and
base-reachable.
