A USB router is a device used for sharing a broadband Internet connection among multiple computers. It is primarily designed for use with cable services where the modem does not have an Ethernet connection. It is also possible to use a USB router for mobile broadband devices.
The most common set-up in which a USB router is used is where a home user gets their broadband services from a cable company. In such a situation, they will get the Internet access through the main fiber optic cable rather than a standard telephone line. This requires a cable modem, which connects and transfers the data between the computer and the fiber optic cable, often filtering out data from the cable TV signal.
In most cases this cable modem will have an Ethernet port. This can either be connected directly to one computer, or to a router which can then provide Internet access to multiple machines. In most cases this will include wireless connections.
In some cases, though, the cable modem will only offer a USB connection. This will work fine if the user only wants to connect one computer and is happy with a wired-only connection. If the user wants to use multiple machines or if they need a wireless connection, a USB-only cable modem will not be sufficient.
The solution is a USB router. This is simply a router which connects to the cable modem via USB rather than Ethernet. Once set up, it operates in exactly the same way as a standard router. The drawback is that fewer firms produce USB routers, meaning there is less price competition.
There may also be situations where a broadband provider will supply a USB modem even when the service comes through a standard telephone line. Such a set-up has become somewhat outdated. Even when the USB modem is the standard option, the broadband provider will usually offer an Ethernet router for an additional fee.
The term "USB router" may also be used for a device which plugs into an Internet-enabled computer and shares its connection with other machines wirelessly. This is often known as an ad-hoc connection. It is much less flexible than a traditional router set-up as it requires the main computer to be switched on and connected to the Internet at all times. If the main computer is switched off, the other machines cannot get online.
Some routers with a USB socket can be connected to a mobile broadband "dongle" and can then share this connection with multiple machines. This could be useful if, for example, two people traveled together and wanted to share the same mobile broadband connection on their laptops. In practice, the relatively low connection speeds and monthly data limits on mobile broadband mean that sharing a connection is not usually desirable.