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The Qualcomm standard IS-2000, known as CDMA2000, is used by several mobile phone companies, including the Globalstar network. [nb 1] The UMTS 3G mobile phone standard, which uses W-CDMA. [nb 2] CDMA has been used in the OmniTRACS satellite system for transportation logistics.
Operator Country Technology Frequency (MHz) Launch date End of service Notes Movicel Angola CDMA2000 1xRTT, EV-DO Rev. A 800 Apr 2004: Mar 2016 [29] [30] [31]BelCel Belarus ...
CDMA2000 1X (IS-2000), also known as 1x and 1xRTT, is the core CDMA2000 wireless air interface standard.The designation "1x", meaning 1 times radio transmission technology, indicates the same radio frequency (RF) bandwidth as IS-95: a duplex pair of 1.25 MHz radio channels. 1xRTT almost doubles the capacity of IS-95 by adding 64 more traffic channels to the forward link, orthogonal to (in ...
Multi-carrier code-division multiple access (MC-CDMA) is a multiple access scheme used in OFDM-based telecommunication systems, allowing the system to support multiple users at the same time over same frequency band. MC-CDMA spreads each user symbol in the frequency domain.
In 3G, the most prevalent technology was UMTS with CDMA-2000 in close contention. All radio access technologies have to solve the same problems: to divide the finite RF spectrum among multiple users as efficiently as possible. GSM uses TDMA and FDMA for user and cell separation. UMTS, IS-95 and CDMA-2000 use CDMA. WiMAX and LTE use OFDM.
VOFDM was proposed by Xiang-Gen Xia in 2000 (Proceedings of ICC 2000, New Orleans, and IEEE Trans. on Communications, Aug. 2001) for single transmit antenna systems. VOFDM replaces each scalar value in the conventional OFDM by a vector value and is a bridge between OFDM and the single carrier frequency domain equalizer (SC-FDE).
CDMA allows multiple people to speak at the same time over the same frequency, allowing more conversations to be transmitted over the same amount of spectrum; this is one reason why CDMA eventually became the most widely adopted channel access method in the wireless industry. [9]
Code-division multiplexing (CDM), code-division multiple access (CDMA) or spread spectrum is a class of techniques where several channels simultaneously share the same frequency spectrum, and this spectral bandwidth is much higher than the bit rate or symbol rate. One form is frequency hopping, another is direct sequence spread spectrum.