What is spreading of spectrum in communication?

What is spreading of spectrum in communication?

Spread Spectrum refers to a system originally developed for military applications, to provide secure communications by spreading the signal over a large frequency band. These narrowband signals are easily jammed by any other signal in the same band.

What do you mean by spread spectrum?

Definition(s): Telecommunications techniques in which a signal is transmitted in a bandwidth considerably greater than the frequency content of the original information. Frequency hopping, direct sequence spreading, time scrambling, and combinations of these techniques are forms of spread spectrum.

What are the requirements of direct sequence spread spectrum?

In telecommunications, direct-sequence spread spectrum (DSSS) is a spread-spectrum modulation technique primarily used to reduce overall signal interference. The direct-sequence modulation makes the transmitted signal wider in bandwidth than the information bandwidth.

How does direct sequence spread spectrum work?

Direct sequence spread spectrum (DSSS) works somewhat differently. With DSSS, the data is divided and simultaneously transmitted on as many frequencies as possible within a particular frequency band (the channel). DSSS adds redundant bits of data known as chips to the data to represent binary 0s or 1s.

What is spread spectrum and its types?

Spread Spectrum can be categorized into two types: Frequency Hopping Spread Spectrum (FHSS) Direct Sequence Spread Spectrum(DSSS)

Why spread spectrum is used in communication?

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. These spread spectrum signals transmit at low power density and has a wide spread of signals.

Which of the following is advantage of direct sequence spread spectrum?

Following are the benefits or advantages of DSSS: ➨It uses both time and frequency planes for transmission of information bits, effect of interference and fading can be minimized to great extent. ➨It can be employed in point to point applications at the rate of 11 Mbps.

Which step is performed first in direct sequence process?

2. In direct sequence process which step is performed first? Explanation: In direct sequence process, De-spreading correlator is followed by a modulator. Explanation: The processing gain is given by the ratio of the minimum bandwidth of the data to data rate.

What is FHSS DSSS?

Direct Sequence Spread Spectrum (DSSS) DHSS spreads the signal over a larger bandwidth than needed, sacrificing bandwidth efficiency for transmission speed and redundancy. For example, 802.11b DSSS uses 22 Mhz channels, as opposed to the roughly 1 Mhz channels used by FHSS.

What are the advantages of FHSS over DSSS?

IEEE 802.11 FHSS provides the following advantages (in comparison to DSSS): Greater tolerance of signal interference because of operation over wider (83.5MHz) bandwidth. Capability to operate up to 10 collocated access points without significant interference.

Which is larger a chip or a spreading sequence?

Each spreading-sequence bit, which is known as a chip, has a much shorter duration (larger bandwidth) than the original message bits. The modulation of the message bits scrambles and spreads the pieces of data, and thereby results in a bandwidth size nearly identical to that of the spreading sequence.

How is the direct sequence spread spectrum used?

In telecommunications, direct-sequence spread spectrum ( DSSS) is a spread-spectrum modulation technique primarily used to reduce overall signal interference. The direct-sequence modulation makes the transmitted signal wider in bandwidth than the information bandwidth. After the despreading or removal of the direct-sequence modulation in

What is the spreading factor of a pseudorandom sequence?

Spreading consists of multiplying input data bits by a pseudorandom or pseudonoise (PN) sequence. The ratio of the PN sequence bit rate to the data rate is called the spreading factor.

What are the properties of a spreading sequence?

The following sections highlight various spreading sequences, their properties, and characteristic performance in single-user or multiuser and single-path or multipath transmission environments. This model compares data recovery for a single-user system versus a two-user system.

How interference can be prevented by spread spectrum communication techniques?

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.

What is spreading in networking?

In DSSS, a spreading code is used to map each data bit in the original signal to multiple bits in the transmitted signal. The pseudorandom code (spreading code) spreads the input data across a wider frequency range compared to the input frequency. In the frequency domain, the output signals appear as noise.

How does a spread spectrum reduce interference?

Figure 1: In a spread-spectrum system, signals are spread across a wide bandwidth, making them difficult to intercept, demodulate, and intercept. The spread of energy over a wide band, or lower spectral power density, also makes spread-spectrum signals less likely to interfere with narrowband communications.

Why do we go for modulation?

The signals within 20 Hz to 20 kHz frequency range can travel only a few distances. To send the message signal, the length of the antenna should be a quarter wavelength of the used frequency. Thus, modulation is required to increase the frequency of the message signal and to enhance its strength to reach the receiver.

What is the need for spread spectrum?

Spread Spectrum refers to a system originally developed for military applications, to provide secure communications by spreading the signal over a large frequency band. Figure 1 represents a narrow band signal in the frequency domain. These narrowband signals are easily jammed by any other signal in the same band.

What is CDMA and its application?

Code Division Multiple Access (CDMA) is a sort of multiplexing that facilitates various signals to occupy a single transmission channel. It optimizes the use of available bandwidth. The technology is commonly used in ultra-high-frequency (UHF) cellular telephone systems, bands ranging between the 800-MHz and 1.9-GHz.

Which is the most common example of interference?

Interference is the phenomenon in which two waves superpose to form the resultant wave of the lower, higher or same amplitude. The most commonly seen interference is the optical interference or light interference. This is because light waves are randomly generated every which way by most sources.

When are two sources of interference said to be coherent?

Two sources are said to be coherent when the waves emitted from them have the same frequency and constant phase difference. Interference from such waves happen all the time, the randomly phased light waves constantly produce bright and dark fringes at every point. But, we cannot see them since they occur randomly.

Where does interference occur in the electromagnetic spectrum?

Coherent Sources and Sustained Interference Interference is a natural phenomenon that happens at every place and at every moment. Yet we don’t see interference patterns everywhere. Interference is the phenomenon in which two waves superpose to form the resultant wave of the lower, higher or same amplitude.

What are the conditions for sustained interference of light?

For sustained interference of light to occur, the following conditions must be met: Coherent sources of light are needed. Amplitudes and intensities must be nearly equal to produce sufficient contrast between maxima and minima. The source must be small enough that it can be considered a point source of light.