No other conversations can access this channel until the subscriber's call is finished, or until that original call is handed off to a different channel by the system. For example, IS-54 systems, designed to coexist with AMPS systems, divide 30 kHz of spectrum into three channels. PDC divides 25 kHz slices of spectrum into three channels. GSM systems create 8 time-division channels in 200 kHz wide carriers. The CDMA Cellular Standard With CDMA, unique digital codes, rather than separate RF frequencies or channels, are used to differentiate subscribers.
All users share the same range of radio spectrum.
In July of 1993, the TIA gave its approval of the CDMA IS-95 standard. One of the unique aspects of CDMA is that while there are certainly limits to the number of phone calls that can be handled by a carrier, this is not a fixed number. Rather, the capacity of the system will be dependent on a number of different factors. This will be discussed in later sections. Though CDMA's application in cellular telephony is relatively new, it is not a new technology.