Arlington-based Federated Wireless has raised $51 million in its latest funding round — its biggest single haul so far — as its customers launch the company’s 5G and private business wireless networks and it looks to expand its own real estate footprint. Federated Wireless, a software-as-a-service firm founded in 2012, has raised a total of $126 million to date. The company provides a shared spectrum Citizen Band Radio Service — technology that allows for the creation of smaller, localized wireless networks — to more than 30 customers.