The Radio Interface Layer is the name for an interface that was developed especially for the Pocket PC Phone Edition. It is meant to abstract the interface with a phone/modem device. To achieve this it is closely modelled after the GSM AT command interface. Unfortunately the API was not published officially by Microsoft. Instead more high level API s were published that should be sufficient for developers. Again, unfortunately they are not sufficient. For example the API for receiving notification of incoming SMS messages is arranged for exclusively for one application per type of SMS. Apparently this will be improved upon in Pocket PC 2003. Another area is the availablity of a true AT command modem interface to interact with the GSM modem directly, which is also absent.