A perspective on distributed radio systems with cooperative coding

In distributed radio systems, e.g., wireless sensor or ad-hoc networks, the system performance may be significantly enhanced by means of cooperation among the nodes. In this paper, we present a perspective on cooperative coding in distributed radio systems. In particular, we consider a simple reference scenario where two source nodes need to transmit two correlated information sequences to a common access point (AP). This is a scenario of interest for wireless sensor networks, where the sensor may observe correlated phenomena. Four possible cooperative coding situations are described: (i) non cooperative system (NCS), (ii) cooperative source coding (CSC), (iii) cooperative sourcechannel coding (CSCC), and (iv) joint source-channel coding (JSCC). While in the first scheme source correlation is not used at all, the following schemes differ according to the way source correlation is used, from CSC systems, where source correlation is used at the sources only, to JSCC systems, where source correlation is used only at the AP. Indeed, JSCC systems are attractive in scenarios (such as wireless scenarios) where communications between the sources might be problematic. As an illustrative example, we will present a practical JSCC system in the presence of block faded channels, using low-density paritycheck (LDPC) coding at the sources and a proper iterative decoder at the AP.