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t. e. Code-division multiple access (CDMA) is a channel access method used by various radio communication technologies. CDMA is an example of multiple access, where several transmitters can send information simultaneously over a single communication channel. This allows several users to share a band of frequencies (see bandwidth).
DS-CDMA (Direct-Sequence Code Division Multiple Access) is a multiple access scheme based on DSSS, by spreading the signals from/to different users with different codes. It is the most widely used type of CDMA. Cordless phones operating in the 900 MHz, 2.4 GHz and 5.8 GHz bands; IEEE 802.11b 2.4 GHz Wi-Fi, and its predecessor 802.11-1999.
For the case of MC-DS-CDMA where OFDM is used as the modulation scheme, the data symbols on the individual subcarriers are spread in time by multiplying the chips on a PN code by the data symbol on the subcarrier. For example, assume the PN code chips consist of {1, −1} and the data symbol on the subcarrier is −j.
Carrier-sense multiple access with collision avoidance (CSMA/CA) in computer networking, is a network multiple access method in which carrier sensing is used, but nodes attempt to avoid collisions by beginning transmission only after the channel is sensed to be "idle". [1][2] When they do transmit, nodes transmit their packet data in its entirety.
Channel access method. In telecommunications and computer networks, a channel access method or multiple access method allows more than two terminals connected to the same transmission medium to transmit over it and to share its capacity. [1] Examples of shared physical media are wireless networks, bus networks, ring networks and point-to-point ...
Chip (CDMA) In digital communications, a chip is a pulse of a direct-sequence spread spectrum (DSSS) code, such as a pseudo-random noise (PN) code sequence used in direct-sequence code-division multiple access (CDMA) channel access techniques. In a binary direct-sequence system, each chip is typically a rectangular pulse of +1 or −1 amplitude ...
DS-1 is a communications protocol for multiplexing the bitstreams of up to 24 telephone calls, along with two special bits: a framing bit (for frame synchronization) and a maintenance-signaling bit, transmitted over a digital circuit called T1. T1 's maximum data transmission rate is 1.544 megabits per second.
Examples of DS-CDMA based cellular systems are: the 3GPP/UMTS 3G radio interfaces WCDMA, HSDPA and HSUPA used globally. the 3GPP2 2G standard cdmaOne (IS-95) and 3G standards CDMA2000 1x and 1xEV-DO, used especially in the U.S. and South Korea; the Chinese TD-SCDMA system. The terminology used in this article is firstly based on 3GPP2 standards.