Synchronizing discrete-time neutrally stable linear systems via   partial-state coupling
  A basic result in synchronization of linear systems via output coupling is presented. For identical discrete-time linear systems that are detectable from their outputs and neutrally stable, it is shown that a linear output feedback law exists under which the coupled systems globally asymptotically synchronize for all fixed connected (asymmetrical) network topologies. An algorithm is provided to compute such feedback law based on individual system parameters. A dual problem is also presented and solved. 
S. Emre Tuna