Definition - What does Frequency Hopping Multiple Access (FHMA) mean?
Frequency Hopping Multiple Access (FHMA) is a spread-spectrum transmission technology, which permits simultaneous voice or data communications to share the exact same communication medium.
This is done by allowing the receiving and transmitting stations to adjust the frequency swiftly in a pseudorandom sequence between several discrete radio channels. Transceivers are synchronized with a hopping sequence computed from a predefined algorithm. This hopping sequence can be modified effectively to avoid various other interference and transmissions in the same frequency band.
Techopedia explains Frequency Hopping Multiple Access (FHMA)
FHMA lets various users concurrently occupy the exact same spectrum, where every user stays at a certain narrowband channel at a specific time period, depending on the user's unique PN code.
Every user's digital data are split into bursts having uniform size, which are sent on various channels within the allotted spectrum band. The instantaneous bandwidth of any one transmission burst is very small compared to the complete spread bandwidth. The pseudorandom modification of the user's channel frequencies randomizes specific channel occupancies at any given time, thus permitting multiple access through a broad range of frequencies.
In the frequency-hopped (FH) receiver, a locally designed PN code is utilized to synchronize the instantaneous frequency of the receiver with the transmitter's frequency. At any given period of time, a frequency-hopped signal occupies only a single, comparatively narrow channel as narrowband FM, or FSK is employed.
The primary difference between FHMA and a standard FDMA technique is that the frequency-hopped signal adjusts channels at speedy intervals. In case the carrier frequency's rate of change is higher when compared to the symbol rate, the technique is often known as a fast frequency hopping system.
If the rate of change is less than or equal to the symbol rate, it is referred to as slow frequency hopping system. A fast frequency hopping system might thus be considered as an FDMA system that uses frequency diversity.
The FHMA systems generally utilize energy-efficient, consistent envelope modulation. Cost-effective receivers can be designed to offer non-coherent detection of FHMA. This signifies that linearity is not a concern, and the strength of various users at the receiver does not degrade the performance of FHMA.