The digital PCS standards comprise an interim standard (IS), to indicate that the standard is not yet approved by the TIA/EIA (Telecommunication Industry Association-Electronic Industry Association). However, these standards have achieved the status of TIA/EIA standards but are commonly referred to with their "IS" code (e.g., IS-136). As described in this chapter, the term IS-136 network refers to the cellular standard defined by the TIA for digital PCS networks. In particular, IS-136 identifies a particular part of the digital PCS family of standards and does not identify all the features of digital PCS networks. The IS-136 standard is the result of the evolution of the North American analog cellular systems called advanced mobile phone service (AMPS). Due to the phenomenal success of AMPS networks, the need for a more efficient system and more cellular capacity led to the development of a first digital cellular standard, called IS-54. However, IS-54 drawbacks (higher costs with no clear improvements for the end users) did not allow IS-54 to duplicate the success of AMPS. Therefore, the IS-136 standard was developed to allow for increased cellular capacity and for providing new services to mobile users. IS-136 allowed for a capacity three times larger than the one provided by AMPS, and for new features such as longer battery life, authentication and voice privacy, caller ID, message waiting indication, and short messages. Whereas AMPS systems used analog traffic and control channels, IS-54 introduced a DTC. Full-rate DTC is supported in IS-54 by means of time multiplexing of 30-KHz RF channels, and a mobile user is assigned a full-rate DTC. In addition to the DTC, IS-136 introduced the DCCH, which allows for the new features supported by IS-136 with respect to its predecessors. The digital PCS standards comprise a set of standards including IS-136, IS-137, IS-138, IS-641, IS-130, and IS-135. Here we give a brief summary of each standard:
IS-137, IS-138, IS-641, IS-130 and IS-135 are supporting standards for IS-136. This means that they complement the features defined in IS-136 for the support of digital PCS services. IS-136 standard merges the digital PCS family into a single standard composed of multiple parts in order to allow for easier tracking of standard modifications and for greater flexibility in the development of new features. |