The original TDMA standard was IS–54, introduced in 1988–89 by the Telecommunications Industry Association (TIA)/CTIA (see Figure 6). It inaugurated a feature set including authentication, calling-number ID, a message-waiting indicator (MWI), and voice privacy.

Figure 6. TDMA Standards Evolution

IS–54B was superseded in 1994 with the introduction IS–136 followed closely by revisions A and B.

IS–136 was backward compatible to IS–54B and included a DCCH and advanced features.

IS–136A upbanded IS–136 for seamless cellular service between the 800–MHz and 1,900–MHz frequency bands. In addition, it introduced over-the-air activation and programming services.

IS–136B includes a new range of services including broadcast SMS, packet data, etc.