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Orthogonality. Conceptually, OFDM is a specialized frequency-division multiplexing (FDM) method, with the additional constraint that all subcarrier signals within a communication channel are orthogonal to one another. In OFDM, the subcarrier frequencies are chosen so that the subcarriers are orthogonal to each other, meaning that crosstalk ...
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 ).
Trellis coded modulation ( TCM) is a modulation scheme that transmits information with high efficiency over band-limited channels such as telephone lines. Gottfried Ungerboeck invented trellis modulation while working for IBM in the 1970s, and first described it in a conference paper in 1976. It went largely unnoticed, however, until he ...
Shannon's diagram of a general communications system, showing the process by which a message sent becomes the message received (possibly corrupted by noise) This work is known for introducing the concepts of channel capacity as well as the noisy channel coding theorem. Shannon's article laid out the basic elements of communication:
Wireless LAN (WLAN) channels are frequently accessed using IEEE 802.11 protocols. The 802.11 standard provides several radio frequency bands for use in Wi-Fi communications, each divided into a multitude of channels numbered at 5 MHz spacing (except in the 45/60 GHz band, where they are 0.54/1.08/2.16 GHz apart) between the centre frequency of the channel.
Digital Signal 1 ( DS1, sometimes DS-1) is a T-carrier signaling scheme devised by Bell Labs. [1] DS1 is the primary digital telephone standard used in the United States, Canada and Japan and is able to transmit up to 24 multiplexed voice and data calls over telephone lines. E-carrier is used in place of T-carrier outside the United States ...
A clear-channel station is a North American AM radio station that has the highest level of protection from interference from other stations, particularly from nighttime skywave signals. This classification exists to ensure the viability of cross-country or cross-continent radio service enforced through a series of treaties and statutory laws.
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 links operating in half ...