With the recent announcement of the Atrix 4G‘s pre-order availability, AT&T made another statement that the laptop dock will require a tethering-capable data plan in order to be used with the Atrix 4G. The cheapest data plan compatible with Atrix 4G runs $25 per month, with a tethering add-on available for $20 per month, nearly doubling the cost.
AT&T has to enforce this tethering plan requirement through some mechanism on the device. The easiest way on AT&T‘s end would be Access Point Name (APN) restrictions – this is the gateway your device uses to get access to the internet at large. In AT&T’s case, there are three common gateways: wap.cingular, isp.cingular, ims.cingular. Which APN you use depends on your plan’s features – wap.cingular is the generic internet access APN, isp.cingular is the tethering-capable APN, and ims.cingular is used for AT&T’s video share service.
In previous devices, AT&T set up a simple toggle in the device’s configuration database (registry, build.prop, etc.) that forces any tethering activity to use the isp.cingular APN. If your account is not provisioned with access to isp.cingular, the tethering activity fails with an error. Fortunately, there are no technical limitations with wap.cingular that prevent it from being used for tethering. This is likely the method AT&T will use with the Atrix 4G, so immediately after rooting, we’ll be able to change the setting and open tethering up using wap.cingular.
Unlocking tethering with wap.cingular using this method has a significant drawback however; you will be limited to the data transfer available with your plan. Since the laptop dock is utilizing a full firefox browser, this may result in going over your transfer limit. However, presumably any individual deciding to undertake this hack will be diligent enough about their data usage for this not to pose a significant problem. Grandfathered users with unlimited data packages who purchase the device/dock through retail channels will be especially interested in this hack.