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1、Collected by esfuncComparison of mobile phone standardsFrom Wikipedia, the free encyclopedia(Redirected from Cdma vs gsm)Jump to: navigation, search This article needs additional citations for verification.Please help improve this article by adding reliable references. Unsourced material may be chal
2、lenged and removed. (August 2007)Global System for Mobile Communications (GSM, around 8085% market share) and IS-95 (around 1015% market share1) are the two most prevalent mobile communication technologies. Both technologies have to solve the same problem: to divide the finite RF spectrum among mult
3、iple users.TDMA (Time Division Multiple Accessunderlying technology used in GSMs 2G) does it by chopping up the channel into sequential time slices. Each user of the channel takes turns to transmit and receive signals. In reality, only one person is actually using the channel at a specific moment. T
4、his is analogous to time-sharing on a large computer server.CDMA (Code Division Multiple Accessunderlying technology used in GSMs 3G and IS-95s 2G) on the other hand, uses a special type of digital modulation called spread spectrum which spreads the voice data over a very wide channel in pseudorando
5、m fashion. The receiver undoes the randomization to collect the bits together and produce the sound.For comparison, imagine a cocktail party, where couples are talking to each other in a single room. The room represents the available bandwidth. In GSM, a speaker takes turns talking to a listener. Th
6、e speaker talks for a short time and then stops to let another pair talk. There is never more than one speaker talking in the room, no one has to worry about two conversations mixing. In CDMA, any speaker can talk at any time; however each uses a different language. Each listener can only understand
7、 the language of their partner. As more and more couples talk, the background noise (representing the noise floor) gets louder, but because of the difference in languages, conversations do not mix.Contentshide 1 Comparison table 2 Traceability comparison 3 Advantages of 2G GSM 4 Disadvantages of 2G
8、GSM 5 Advantages of IS-95 6 Disadvantages of IS-95 7 Development of the Market Share of Mobile Standards 8 Comparison of wireless Internet standards 9 See also 10 Referencesedit Comparison tableFeatureNMTGSMUMTS (3GSM)IS-95 (CDMA one)CDMA 2000TechnologyFDMATDMAW-CDMACDMACDMAGeneration1G2G3G2G3GDigit
9、alNoYesYesYesYesYear of First Use19811991200119952000 / 2002Worldwide market share *Valid non-biased source still required0%72%12%0.6%12%RoamingScandinaviaWorldwide, 200+ countriesWorldwideLimitedLimitedHandset interoperabilityNoneSIM cardSIM cardNoneRUIM (not commonly implemented)Operator lockingMo
10、nopolyUnlockableUnlockableESNESNCommon InterferenceNoneInterferes with some electronics, such as amplifiersNoneNoneNoneSignal quality/coverage areaGood coverage due to low frequenciesGood coverage indoors on 850/900MHz. Repeaters possible. 35km hard limit.Smaller cells and lower indoors coverage on
11、2100MHz; equivalent coverage indoors and superior range to GSM on 850/900MHz.Unlimited cell size, low transmitter power permits large cellsUnlimited cell size, low transmitter power permits large cellsFrequency utilization/Call densityVery low density0.2MHz = 8 timeslots. Each timeslot can hold up t
12、o 2 calls through interleaving.5MHz = 2 Mbit/s. Each call uses 1.8-12 kbit/s depending on chosen quality and audio complexity.? Comparable to UMTS? Comparable to UMTSBattery lifeLow, due to high transmitter power (1 watt)Very good due to simple protocol, good coverage and mature, power-efficient chi
13、psets.Lower due to high demands of WCDMA power control and young chipsets.Lower due to high demands of CDMA power control.Lower due to high demands of CDMA power control and young chipsets.HandoffHardHardSoftSoftSoftBreathingNoNoYesYesYesIntellectual propertyScandinavian telecom operatorsConcentrate
14、d among a few manufacturersConcentrated among a few manufacturersQualcommQualcommedit Traceability comparisonThis section requires expansion.edit Advantages of 2G GSM GSM is mature; this maturity means a more stable network with robust features. Less signal deterioration inside buildings. Ability to
15、 use repeaters. Talktime is generally higher in GSM phones due to the pulse nature of transmission. The availability of Subscriber Identity Modules allows users to switch networks and handsets at will, aside from a subsidy lock. GSM covers virtually all parts of the world so international roaming is not a problem. The much bigger number of subscribers globally creates a better network effect for GSM handset makers, carriers and end users.edit Disadvantages of 2G GSM Pulse nature o
