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Frequency-hopping spread spectrum (FHSS) is a method of transmitting radio signals by rapidly changing the carrier frequency among many frequencies occupying a large spectral band. The changes are controlled by a code known to both transmitter and receiver .
It allows several users to share the same frequency channel by dividing the signal into different time slots. [1] The users transmit in rapid succession, one after the other, each using its own time slot. This allows multiple stations to share the same transmission medium (e.g. radio frequency channel) while using only a part of its channel ...
Have Quick (also HAVEQUICK, short HQ) is an ECM-resistant frequency-hopping system used to protect military aeronautical mobile (OR) radio traffic. Since the end of World War II , U.S. and Allied military aircraft have used AM radios in the NATO harmonised 225–400 MHz UHF band (part of NATO B band [ 1 ] ) for short range air-to-air and ground ...
Practical synchronous digital systems radiate electromagnetic energy on a number of narrow bands spread on the clock frequency and its harmonics, resulting in a frequency spectrum that, at certain frequencies, can exceed the regulatory limits for electromagnetic interference (e.g. those of the FCC in the United States, JEITA in Japan and the ...
Random frequency-hopping orthogonal frequency division multiple access (RFH-OFDMA) Code-division multiple access (CDMA), where different amount of spreading codes or spreading factors can be assigned to different users. Statistical multiplexing normally implies "on-demand" service rather than one that preallocates resources for each data stream.
Time-division multiplexing (TDM) is a method of transmitting and receiving independent signals over a common signal path by means of synchronized switches at each end of the transmission line so that each signal appears on the line only a fraction of time according to agreed rules, e.g. with each transmitter working in turn.
Pilot signals and training symbols may also be used for time synchronization (to avoid intersymbol interference, ISI) and frequency synchronization (to avoid inter-carrier interference, ICI, caused by Doppler shift). OFDM was initially used for wired and stationary wireless communications.
Time Slotted Channel Hopping or Time Synchronized Channel Hopping (TSCH) is a channel access method for shared-medium networks. TSCH is used by Low-Power devices to communicate using a wireless link. It is designed for low-power and lossy networks (LLNs) and aims at providing a reliable Media access control layer.