Comcast and Time Warner Cable have taken a step towards the merger they announced in February. The companies have filed a request for review with the Federal Communications Commission, one of the agencies that will have to approve the $45 billion deal between Americas two largest providers of wired broadband. In a 181-page document, the companies argued that Comcasts acquisition of TWC would give consumers network upgrades, better cable TV services, and expanded broadband access for low-income users. Many of the promised benefits apparently stem from Comcast expanding its existing services to cover TWC customers.