Wireless machine connection

Hi, at Bekaert we are running an MES program with which we want to rollout in + 20 sites an MEs solution which is heavily using the data coming from the machine layer. One of the biggest bottlenecks in terms of budget and leadtime is the connection of the machines to MES. In each site we have > 1000 machines which are cussrently connected via Lan to the network in order to send the PLC data to what we call an automation server. Does anybody know if there are already robust wireless solutions available on the market.