Mapping technological trajectories as patent citation networks. An application to data communication standards

We use patent citation networks to study the dynamics of technical change in Ethernet, a standard for data communication. We first consider the evolution of the broad technological system of local area networks (LANs) and we identify the most significant inventions within the specific subfield of Ethernet. Then we analyse the structure of connectivity of patent citation networks to reconstruct the main technological trajectories in this subfield. Our results suggest that these technological trajectories are characterized by the presence of a number of interconnected technological environments which cluster following an engineering logic. These clusters include the most significant patents related to 'milestones inventions' in the evolution of the LAN technology. Thus, our analysis of the structure of connectivity in patent citation networks seems appropriate to capture both the cumulativeness associated to the development of a specific technology and the significant discontinuities that punctuate the trajectory, as well as the technological interrelatedness characterising large technical systems.