built-in limit to the number of concurrent users. Uses precise clocks that do not limit the distance a tower can cover. Consumes less power and covers large areas so cell size in IS-95 is larger. Able to produce a reasonable call with lower signal (cell phone reception) levels. Uses soft handoff, reducing the likelihood of dropped calls. IS-95's variable rate voice coders reduce the rate being transmitted when speaker is not talking, which allows the channel to be packed more efficiently. Has a well-defined path to higher data rates. Disadvantages of IS-95 Most technologies are patented and must be licensed from Qualcomm. Breathing of base stations, where coverage area shrinks under load. As the number of subscribers using a particular site goes up, the range of that site goes down. Because IS-95 towers interfere with each other, they are normally installed on much shorter towers. Because of this, IS-95 may not perform well in hilly terrain. USSD, PTT, concatenated/E-sms are not supported by IS-95/CDMA IS-95 covers a smaller portion of the world, and IS-95 phones are generally unable to roam internationally. Manufacturers are often hesitant to release IS-95 devices due to the smaller market, so features are sometimes late in coming to IS-95 devices. Even barring subsidy locks, CDMA phones are linked by ESN to a specific network, thus phones are typically not portable across providers. Development of the market share of mobile standards This graphic compares the market shares of the different mobile standards. In a fast-growing market, GSM/3GSM (red) grows faster than the market and is gaining market share, the CDMA family (blue) grows at about the same rate as the market, while other technologies (grey) are being phased out Comparison of wireless Internet standards As a reference, a comparison of mobile and non-mobile wireless Internet standards follows. See also Comparison of wireless data standards Spectral efficiency comparison table SMS – contain the content of its standardization References Mobile phone standards