Search results
Results From The WOW.Com Content Network
Frequency-division multiple access (FDMA) is a channel access method used in some multiple-access protocols. FDMA allows multiple users to send data through a single communication channel, such as a coaxial cable or microwave beam, by dividing the bandwidth of the channel into separate non-overlapping frequency sub-channels and allocating each sub-channel to a separate user.
In the WDMA case, different network nodes in a bus or hub network get a different color. [7] An advanced form of FDMA is the orthogonal frequency-division multiple access (OFDMA) scheme, for example, used in 4G cellular communication systems. In OFDMA, each node may use several sub-carriers, making it possible to provide different quality of ...
Single-carrier FDMA (SC-FDMA) is a frequency-division multiple access scheme. Originally known as Carrier Interferometry , it is also called linearly precoded OFDMA ( LP-OFDMA ). Like other multiple access schemes (TDMA, FDMA, CDMA, OFDMA), it deals with the assignment of multiple users to a shared communication resource.
The mobile transmits at the beginning of the time slot as received from the network. If the mobile is near the base station, the propagation delay is short and the initiation can succeed. If, however, the mobile phone is just less than 35 km from the base station, the delay will mean the mobile's transmission arrives at the end of the time slot.
QDMA is used for local area networks, usually wireless short-range such as WiMax. CDMA and QDMA are especially suitable for modern communications, for example, the transmission of short messages such as SMS or MMS; communication when in motion (from cars, trains, etc.); the establishment of unplanned links.
Sowa invented conceptual graphs, a graphic notation for logic and natural language, based on the structures in semantic networks and on the existential graphs of Charles S. Peirce. He introduced the concept in the 1976 article "Conceptual graphs for a data base interface" in the IBM Journal of Research and Development . [ 7 ]
A single frequency network is a form of transmitter macrodiversity. The concept can be further used in dynamic single-frequency networks (DSFN), where the SFN grouping is changed from timeslot to timeslot. OFDM may be combined with other forms of space diversity, for example antenna arrays and MIMO channels.
The passband of an FDM channel carrying digital data, modulated by QPSK quadrature phase-shift keying.. The multiple separate information (modulation) signals that are sent over an FDM system, such as the video signals of the television channels that are sent over a cable TV system, are called baseband signals.