The present thesis addresses the problem of stabilisability of a linear time invariant (LTI) output feedback control loop in the presence of a communication link. The communication link itself can be either located between the controller and the plant or between the plant and the controller. The communication link is assumed to be an additive coloured Gaussian noise channel with (or without) bandwidth limitation (memory) in the continuous-(or discrete-)time domain. The requirement for stabilisability of the feedback loop is then characterised as a lower bound on the channel signal to noise ratio (SNR). This lower bound is tight and it will depend on the channel model, plant and channel model NMP zeros, plant time delay and plant unstable poles. Performance requirements are also investigated, by loop shaping in the continuous-time domain, whilst a linear quadratic Gaussian (LQG) control approach is suggested for the discrete-time domain. / PhD Doctorate