As shown in Figure 18, the architecture of IS 95 is same as that of GSM. The roles of BTS,BSC,MSC, VLR,HLR remain the same except inclusion of Interworking Function (IWF).

Interworking Function (IWF): It is a technique for interfacing data between a wireless system and the telephone network; involves the use of modems or data terminal adapters to convert the data transmitted over the air interface and mobile network to a format that can be recognized and carried by the public telecommunications network. The reader should note that although the architecture looks similar to GSM, the principle of operation and the air specification is totally different.