The 802.11b or 802.11g protocol is used for the wireless link between the router and the Wireless Network Adapterss in any connecting PCs or Laptops. This is independent of the wireless broadband service you are receiving over the 5GHz link.
The question is really "what type of interface does your broadband service have for connecting computers?" If it is a conventional RJ45 ethernet port, then a wireless router can plug directly into that, but there is also the matter of how you establish the connection. With "Cable" broadband, it is just a matter of connecting by ethernet cable and, provided the modem is online, the computer is online - there is no connection to establish using PPP as is the case with ADSL.
Does that make sense?