why cdma is called spread spectrum?
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CDMA is a form of a Direct Sequence Spread Spectrum (where the transmitted data is coded at a very high frequency) communication. In spread spectrum, to send data, the signal bandwidth is much larger than necessary to support multi-user access. ... Multi user access is achieved using a code that is pseudo-random.
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CDMA: The American Contender The other well-travelled cellular technology is CDMA. CDMA was developed by Qualcomm. The CDMA brand name encompasses two different standards: IS-95 aka CDMA One, a 2G digital service, and its modern 3G successor CDMA-2000.
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Frequency-division multiple access (FDMA) provides multiuser access by separating the used frequencies. This is used in GSM to separate cells, which then use TDMA to separate users within the cell.
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Two basic technologies in mobile phones, CDMA and GSM, represent a gap you can't cross. They're the reason you can't use older AT&T phones on Verizon's network and vice versa. ... CDMA (Code Division Multiple Access) and GSM (Global System for Mobiles) are shorthand for two older radio systems used in cell phones.
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There are five basic access or multiplexing methods: frequency division multiple access (FDMA), time division multiple access (TDMA), code division multiple access (CDMA), orthogonal frequency division multiple access (OFDMA), and spatial division multiple access (SDMA).
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GSM handsets came with a SIM card slot, while CDMA phones did not. ... On the other hand, with GSM devices, the phone number is linked to the SIM card, so when switching devices, all you have to do is pop the SIM card into a new phone and you are good to go.
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STC uses 2 GSM bands, 2 UMTS bands, 4 and 0 CDMA bands.. You can read the specific frequency bands in the table below. All bands of the STC are display in MHz units.
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As TDMA makes efficient use of the spectrum, more number of users can use same spectrum than FDMA system. ... ➨The different types of traffic e.g. voice, data and video are transmitted using TDMA technique as this require different data rates which can be easily achieved using allocation of multiple time slots.
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Explanation: The popular 2G CDMA standard, Interim Standard (IS-95) is also known as CdmaOne. The 2.5G CDMA standard, IS-95B is called CdmaTwo. And IS-136 is a TDMA standard for 2G. ... Explanation: Interim Standard 136 (IS-136) was popularly known as North American Digital Cellular (NADC) system.
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GSM handsets came with a SIM card slot, while CDMA phones did not. In other words, CDMA is a handset-based standard, with a phone number linked to a particular device. If you wanted to upgrade to another phone, you would have to get in touch with the network carrier, de-activate the old device and activate the new one.
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UMTS has faster data transfer rates than GSM. 2. GSM is 2G and 2.5G while UMTS is already 3G. ... GSM is typically based on TDMA while UMTS is mainly CDMA-based.
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If your phone has an MEID or an ESN number, it's CDMA. If you see an IMEI number then it's GSM.
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Both OFDM and CDMA have significant benefits. OFDM can combat multipath interference with greater robustness and less complexity. Equalisation can be undertaken on a carrier by carrier basis. OFDMA can achieve higher spectral efficiency with MIMO than CDMA using a RAKE receiver.
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CDMA (Code Division Multiple Access) and GSM (Global System for Mobiles) are shorthand for two older radio systems (2G and 3G) used in cell phones. ... Verizon will turn off its CDMA network and T-Mobile will turn off its 2G GSM network by the end of 2020.
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3g isn't called WCDMA(at least in our country). Rather,3g is based on WCDMA (Wideband Code Division Multiple Access) technology.It makes use of a single 5 MHz channel for both voice and data. Its faster than the typical CDMA network.
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Verizon and U.S. Cellular are both wireless service providers that use CDMA technology, meaning that they don't use SIM cards to connect phones to their networks. Verizon is a nationwide carrier offered most anywhere, while U.S. Cellular is offered in about half of the United States.
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You cannot use a GSM SIM card in a mobile device that is designed to work exclusively with CDMA because CDMA and GSM are two different technologies. However, you can use a GSM SIM card in a mobile device which incorporates both CDMA and GSM technology. Check your phone's specifications to see if it has this capability.