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Is a spread-spectrum multiple access technique?
…is sometimes referred to as spread-spectrum multiple access (SSMA), because the process of multiplying the signal by the code sequence causes the power of the transmitted signal to be spread over a larger bandwidth. Frequency management, a necessary feature of FDMA, is eliminated in CDMA.
What are the two ways to implement spread-spectrum communication?
There are two predominant techniques to spread the spectrum: 1) Frequency hoping (FH), which makes the narrow band signal jump in random narrow bands within a larger bandwidth. 2) Direct sequence (DS) which introduces rapid phase transition to the data to make it larger in bandwidth.
What do you mean by spread-spectrum multiple access?
Spread spectrum multiple access (SSMA) uses signals which have a transmission bandwidth whose magnitude is greater than the minimum required RF bandwidth.
What are two main types of spread spectrum multiple access techniques?
There are generally two types of SSMA techniques: frequency-hopped spread spectrum (FHSS); direct-sequence spread spectrum (DSSS).
Is LTE a spread spectrum?
LTE is a broadband wireless technology that uses wide channels to achieve high data rates and accommodate lots of users. The standard is set up to permit bandwidths of 1.4, 3, 5, 10, 15, and 20 MHz. The carrier selects the bandwidth depending on spectrum holdings as well as the type of service to be offered.
What are the types of spread spectrum?
There are two main types of spread spectrum techniques that are employed. These are Direct Sequence Spread Spectrum (DSSS) and Frequency Hopping Spread Spectrum (FHSS).
What are the advantages of spread spectrum?
The main advantage of spread spectrum communication technique is to prevent “interference” whether it is intentional or unintentional. The signals modulated with these techniques are hard to interfere and cannot be jammed. An intruder with no official access is never allowed to crack them.
How does multi user orthogonal Chirp Spread spectrum improve performance?
Multi user orthogonal chirp spread spectrum (OCSS) can improve the spectral inefficiency of chirp spread spectrum (CSS) but is only feasible with perfect synchronism and without any channel dispersion. Asynchronism, channel dispersion, or unexpectedly large Doppler shifts can cause multiple access interference (MAI), which degrades performance.
How are upchirps used in the spread spectrum?
Other types of upchirps may increase exponentially over time. In digital communications, chirp spread spectrum ( CSS) is a spread spectrum technique that uses wideband linear frequency modulated chirp pulses to encode information.
How is the chirp spread spectrum different from the DSSS?
However, it is unlike direct-sequence spread spectrum (DSSS) or frequency-hopping spread spectrum (FHSS) in that it does not add any pseudo-random elements to the signal to help distinguish it from noise on the channel, instead relying on the linear nature of the chirp pulse.
What does chirp stand for in IEEE 802.15.4a?
Chirps are specified in the IEEE 802.15.4a standard as chirp spread spectrum (CSS). Another growing application area requiring advanced communications is aviation.