A type of radio communications in which the transmitter and receiver hop in synchronization through a pre-arranged pattern of frequencies. This reduces the effect of narrow band noise. FHSS modulates information onto a narrowband carrier signal that "hops" in a pseudo-random but predictable sequence from frequency to frequency. This technique reduces interference because a signal from a narrowband system will only affect part of the spectrum. Transmission frequencies are determined by a so-called spreading, or hopping, code. Receivers must be set to the same hopping code and must listen to the incoming signal at the right time and correct frequency in order to properly decode the signal. FCC regulations require manufacturers to use 75 or more frequencies per transmission channel with a maximum dwell time (the time spent at a particular frequency) of 400 ms.
A spread spectrum modulation technique whereby the radio transmitter frequency-hops from channel to channel in a predetermined but pseudorandom manner. The RF signal is dehopped at the radio receiver using a frequency synthesizer controlled by a pseudorandom sequence generator synchronized to the transmitter's pseudorandom sequence generator. A frequency hopper may be fast-hopped, where there are multiple hops per data bit, or slow-hopped, where there are multiple data bits per hop.
A type of spread-spectrum radio transmission in which the transmitter and receiver hop in synchronization from one frequency to another according to a prearranged pattern.
A spread spectrum technique which involves constantly changing the RF carrier's frequency in such a way that only the intended receiver can decipher it.
Hedy Lamarr, the actress, is credited in name only for inventing frequency hopping during World War II. As its label suggests, frequency hopping transmits using a narrowband carrier that changes frequency in a given pattern. There are 79 channels in a 2.4GHz ISM band, each channel occupying 1MHz of bandwidth. A minimum hop rate of 2.5 hops per channel per second is required in the United States. Frequency hopping technology is recognized as superior to direct sequence in terms of echo resistance, interference immunity, cost and ease-of-installation. To date, there has also been a greater selection of WLAN products from which to chose.
A method by which a carrier spreads out packets of information (voice or data) over different frequencies. For example, a phone call is carried on several different frequencies so that when one frequency is lost another picks up the call without breaking the connection.
A WLAN technology that uses narrow band carrier that changes frequency in a pattern known both to transmitter and receiver.
One of two approaches (with direct sequence spread spectrum) for sorting out overlapping data signals transmitted via radio waves. Frequency hopping spread spectrum is commonly abbreviated to FHSS or FH. Bluetooth uses frequency hopping spread spectrum.
FHSS is one of two types of spread spectrum radio, the other being direct sequence spread spectrum (DSSS). FHSS is a transmission technology used in WLAN transmissions where the data signal is modulated with a narrowband carrier signal that "hops" in a random but known sequence from frequency to frequency as a function of time over a wide band of frequencies. The signal energy is spread in time domain rather than chopping each bit into small pieces in the frequency domain. This technique reduces interference because a signal from a narrowband system will only affect the spread spectrum signal if both are transmitting at the same frequency at the same time. If synchronized properly, a single logical channel is maintained. The transmission frequencies are determined by a spreading, or hopping, code. The receiver must be set to the same hopping code and must listen to the incoming signal at the right time and correct frequency in order to properly receive the signal. Current FCC regulations require manufacturers to use 75 or more frequencies per transmission channel with a maximum dwell time (the time spent at a particular frequency during any single hop) of 400 milliseconds.
