re 10.20. The total sum of these interferences and noise power compared with the desired signal power yield the SINR. The capacity of an IS-95 system in terms of the number of voice channels is calculated based on the required SINR for a voice channel. Given the length of code, the fact that a user is only actively speaking around 40% of the time, and a required SINR of 7 dB, the total number of simultaneous voice channels may be estimated as around a third of the total code space. For IS-95 standard the number of users per carrier can be estimated at 20-25 per cell. This is a rule of thumb that a third of the code space can be used in a CDMA system consid- ering all the interference from uplink and downlink users in cells near the nearby cells, fading and noise. It follows that the same frequency may be used in all cells (i.e. frequency reuse factor is equal to 1). This simplifies frequency planning significantly compared with both FDMA and TDMA systems [8, 9]. Example 10.4 An IS-95 operator has been allocated 10 MHz of spectrum (5 MHz for downlink and 5 MHz for uplink). How many voice channels can be offered in each cell if the frequency reuse factor is 1? Answer Assuming that the allocated 5 MHz spectrum can accommodate 3 IS-95 system carriers, and that 23 active voice users per carrier may be supported, the total number of users is 3 X 23 = 69 users, resulting in a 13.8 voice channel/MHz capacity. Note this is similar to capacity figure for the GSM system. Terrestrial Broadband Wireless Telecommunications Third Generation: Digital Mobile Communications Systems The mobile communications standards landscape in the middle of the 1990s was a mix of regional and proprietary standards. GSM had made large in-roads in becoming a world-wide standard. However it was not widely adopted in a number of regions and countries such as the Americas, Japan and Korea. The two Japanese 2G standards had remained confined to Japan and Japanese handsets and handset manufacturers were largely constrained in developing devices for ot