The authors study causal dynamic source-channel codes for mean-square stabilisation of a linear plant with random initial state, over binary symmetric channels (BSCs). A binary expansion source coding scheme and two types of channel coding schemes are investigated: (i) dynamic repetition encoding under sequential majority logic decoding, and (ii) dynamic Fountain encoding under sequential BP decoding. The coding schemes are first analysed for an openloop system, where the goal is to transmit a real-valued source over BSCs with the objective of minimising end-to-end mean-square error distortion. They derive upper-and lower bounds on the achievable distortion which is a function of time. Based on these distortion bounds, they show that the dynamic Fountain codes are able to stabilise (in mean-square sense) an unstable linear plant over BSCs.
IntroductionRecent advances in sensor technology, low-power electronics, digital communications and networking have enabled the engineering of a completely new type of networked monitoring and control systems, which have the potential to drastically decrease costs and increase productivity in a wide range of industrial applications. Such systems are known as networked control systems (NCS), consisting of a plant and a group of sensors, controllers and actuators that need to exchange information over communication links to perform coordinated actions. In practice, the communication links are noisy and the transmission errors are inevitable, affecting the performance of NCS. Traditionally, long block codes are used in the design of communication systems to provide reliable communication over noise corrupted channels. However, the use of longer codes incurs larger delays in the decoding of the transmitted information, which may not be suitable for certain delay sensitive closed-loop control applications. Thus, it is important to develop delay-efficient coding methods that can be used for transmitting information within NCS. This paper makes an effort in this direction by studying delay-efficient source-channel coding methods for state estimation or stabilisation of a plant that is connected to a controller via a noisy digital communication channel. In the following, we first introduce the system model and the objectives in Section 1.1, then provide a review of the relevant literature in Section 1.2 and finally highlight the main contributions of this paper in Section 1.3.
System modelConsider a discrete-time linear system (plant) with the following state equationwhere X (t) ∈ R n is a state variable and U (t) ∈ R is a control variable. The matrices A and B are of appropriate dimensions and the pair (A, B) is controllable. Let {a 1 , a 2 , . . . , a n } denote the eigenvalues of A. Without loss of generality we assume that all the eigenvalues of A are outside the unit disc, that is, |a i | ≥ 1. The unstable modes can be decoupled from the stable modes by a similarity transformation. If the system in (1) is one-dimensional then A is scalar and we use the notation A = a. We assume th...