According to recent reports, AT&T mobile customers who upgraded to the iPhone 5 or iOS 6 on an iPhone 4 now face problems with the MicroCell service.

MicroCell is a 3G device designed to boost the cellular signal through the existing broadband connection for AT&T customers who get bad reception inside their houses. A lot of users have relied on MicroCells to amplify their signal in areas of bad reception, but the service has apparently stopped working for some.

AT&T Wireless forums are filled with reports of issues connecting to the MicroCell from iPhone 5 and from people who just upgraded their devices to Apple's latest operating system. AT&T has been notified of the issue and is reportedly working to fix it. The carrier did not offer any timeframe for the promised fix.

While the MicroCell is a complicated product in itself, in this case things are even more tangled between AT&T, Cisco - the manufacturer - and Apple.

Some of the iPhone 5 issues with the service are apparently tied to LTE, as 3G MicroCell does not support LTE connections. The HSPA base band chip on the device's circuit board is not compatible with LTE, which makes it a hardware issue. In turn, this means the problem cannot be resolved with a software or firmware fix.

Some users on the AT&T forums have reported that turning off the LTE on their iPhone 5 smartphones allows them to connect to the MicroCell. The iOS 6 issues, however, may ba more difficult to diagnose and fix. To avoid interference with local cell towers, MicroCell adjusts the signal strength it generates inside the house based on how weak the actual cell signal is at the time of initial activation. Individual phones, meanwhile, will adjust their transmitter based on the signal strength received from the Microcell device. All of this back and forth to balance the signal has created problems for some users, while others were left unaffected.

The MicroCell has been greatly appreciated especially by AT&T users in rural and coastal areas, who get substandard cell coverage at home. If you are among those people and rely on MicroCell on a daily basis, consider the risks before upgrading to the iPhone 5 or iOS 6. It is difficult to assess the actual scale of the problem based only on forum reports and talks with iPhone users, but if AT&T is aware of the problem a fix should arrive soon.