Sharing Cellular Data Access Between Multiple PCs

As described in the previous post, you only want to use a cellular data service (EVDO or HSPDA) for your home ISP if you can’t get good DSL, cable, or fixed wireless access. Cellular data service is, when available, usually better than satellite service. Like satellite service, cellular data comes with limits (not always enforced) on how much data you can transfer in a month. The previous post also describes how to find out whether high speed cellular data service is available where you live.

This post tells you how to use a single cellular data service account for all of the PCs and even some other IP devices in your home. That’s important because the accounts are expensive so you certainly don’t want to buy one for each PC. Note that, although the Verizon Wireless terms of service seem to permit such non-commercial shared use, other carriers may have at least a nominal prohibition on sharing; I haven’t checked their terms.

One way to share a connection is with a Windows feature called Internet Connection Sharing (I don’t know what the Mac equivalent is but would be glad to have some Mac-knowledgeable reader supply the details). There are also devices which act as hubs for sharing a cellular data connection (subject of a future post).

In order to get Internet Connection sharing working, here’s what you need to do:

1. Assuming that you already have your cellular data account and the necessary PC card or USB device to access it (or, less likely, your PC came with EVDO and/or HSPDA capability), start up the service as instructed in its documentation so you can access the Internet.
2. Open the Network Connections window. One way to get to it is through Start/Connect To…/Show All Connections.
3. Right-click the icon for the service you’re using in the Network Connections window and elect Properties from the popup menu
4. Click the Advanced tab
5. Check the box which says “Allow other network users to connect through this computer’s Internet connection”
6. Right below that checkbox is a dropdown menu which says “Select a private network connection”. This is the connection that will be used to connect your computer to the other computer(s) which share the Internet connection. If you are going to use WiFi to connect the computers, select Wireless Connection. If you are cabling them together by putting Ethernet cables between the computers’ Ethernet ports, select whichever local area connection corresponds to the Ethernet connection.
7. Click OK
8. If you are using Ethernet, you should now have a connection to the Internet from both your computer and the one which is connected to it (connecting more than two computers to the Internet in this manner requires more equipment and is beyond the scope of this post). BTW, you could use the Ethernet connection to share your cellular data connection with a VoIP phone or some other IP device.
9. If you are using WiFi, you now have to set up an ad hoc WiFi network. The good news is that this can be shared by multiple computers within WiFi range. The bad news is that you have some more steps to follow.
10. Even worse news is that I can’t give exact steps to follow next because different WiFi cards and builtin chipsets come with different setup programs. But somehow you want to do all the things in the steps below.
11. On the computer which has the cellular data connection and all other computers with which you want to share the connection, enable ad hoc networking in the control application for your WiFi device (may already be enabled).
12. On the machine with the cellular data connection, create a profile for an ad hoc network with a name (SSID) which you believe will be unique.
13. Turn on WiFi on all machines in your network and, on the machines that want to share the connection, look for the SSID you set up above to become visible.
14. Most WiFi control applications will require you to explicitly connect to this SSID and some may require you to make a profile for it.
15. Once the WiFi connections are established, all machines should have Internet access through the “gateway” machine, the one with the cellular data connection.

IMPORTANT: Don’t forget to turn off Internet Connection Sharing when you are no longer using your computer as a gateway. If you leave it on, you’ll have trouble connecting that machine to the Internet when it’s NOT the gateway.

You can make the WiFi network secure in the usual way with WEP encryption (not covered in this post). The way I described above creates an open ad hoc network where transmissions are visible to those within range of the network who choose to access it and where others may decide to share your Internet connection.

BTW, these techniques are also useful for sharing a single WiFi or Ethernet connection in a hotel room. Use WiFi to share an Ethernet connection or Ethernet to share a WiFi connection. Mary and I are a two computer family even when traveling and we do this all the time.