What is coherent 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.

What is Direct Sequence Spread Spectrum explain with an example?

Direct sequence spread spectrum (DSSS) is a transmission technology used in local area wireless network transmissions. In this technology, a data signal at the sending station is combined with a high data rate bit sequence, which divides user data based on a spreading ratio.

Is DSSS and BPSK same?

Direct Sequence Spread Spectrum (DSSS) using BPSK modulation, so the first reversing switch introduces 180 degree phase reversals according to a pseudo-random code, while the second introduces the same reversals to reconstitute the original, narrow-band signal. The output is a “recompressed” narrow-band signal.

What is the spreading factor in DSSS?

One of the most essential attributes of DSSS coding is the spreading factor, which is defined as the quotient of the chip rate and the bit rate. As suggested by the above characteristics, DSSS does not affect the transmission time for the same transmitted packet.

What is spread spectrum?

Spread spectrum is a form of wireless communications in which the frequency of the transmitted signal is deliberately varied. This results in a much greater bandwidth than the signal would have if its frequency were not varied.

What are the applications of BPSK?

BPSK Applications The BPSK modulation is a very basic technique used in various wireless standards such as CDMA, WiMAX (16d, 16e), WLAN 11a, 11b, 11g, 11n, Satellite, DVB, Cable modem etc. It is considered to be more robust among all the modulation types due to difference of 180 degree between two constellation points.

What is the spread spectrum?

Why spread spectrum is used?

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 are the types of spread spectrum?

There are four generic types of spread spectrum signals:

Direct Sequence (DS) – The carrier of a DS source stays at a fixed frequency. Narrowband information is spread out into a much larger bandwidth using a pseudo-random chip sequence.
Pseudo noise (PN)
Frequency Hopping (FHA)
Linear Frequency Modulation (chirp)

What are the applications of spread spectrum?

Current applications of spread spectrum technology include wireless LANs (local area networks), bar code scanners, and microphones. This technology improves the efficiency and effectiveness of business processes, many of which are finding that wireless communications are requisite for success.

What is the concept of BPSK?

Binary Phase-shift keying (BPSK) is a digital modulation scheme that conveys data by changing, or modulating, two different phase s of a reference signal (the carrier wave ). The constellation points chosen are usually positioned with uniform angular spacing around a circle.

What are the advantages of BPSK?

Benefits or advantages of BPSK ➨It is most robust modulation technique due to the fact that binary 1 and 0 are separated by 180 degree phase shift of the carrier. Due to this property, BPSK modulated data can travel longer distances when transmitted from base station or subscriber stations.

How is BPSK generated?

Generation of BPSK: Consider a sinusoidal carrier. If it is modulated by a hi-polar hit stream according to the scheme illustrated in Figure below, its polarity will be reversed every time the bit stream changes polarity. This, for a sinewave, is equivalent to a phase reversal (shift).

What is BPSK used for?

As mentioned BPSK stands for Binary Phase Shift Keying. It is digital modulation technique. This is regarded as the most robust digital modulation technique and is used for long distance wireless communication.

What is coherent detection of BPSK?

In coherent detection, the receiver derives its demodulation frequency and phase references using a carrier synchronization loop. Such synchronization circuits may introduce phase ambiguity in the detected phase, which could lead to erroneous decisions in the demodulated bits.

What is the advantage of BPSK?

How do you draw a BPSK signal?

How to generate BPSK signal

Generate 1000 random binary data bits.
Convert unipolar to bipolar in the databits.
Modulate the bipolar bits with Binary Phase Shift Keying (BPSK).
Multiply the baseband BPSK with a carrier fc = 100 Hz.
The modulated BPSK signals will be transmitted through a Noiseless channel.

What is coherent detection?

Coherent detection allows information to be encoded with two degrees of freedom, which increases the amount of information per channel. From: Optical Fiber Telecommunications VII, 2020.

How is BPSK signal generated?

The modulated BPSK signals will be transmitted through a Noiseless channel. At the receiver side demodulate the received signal by multiplying it with a carrier and passing it through a Low Pass Filter (LPF).

What is meant by BPSK?

Binary Phase-shift keying (BPSK) is a digital modulation scheme that conveys data by changing, or modulating, two different phases of a reference signal (the carrier wave). The constellation points chosen are usually positioned with uniform angular spacing around a circle.

How to calculate the direct sequence BPSK signal?

The direct sequence BPSK (or DS/BPSK) signal is generated at the output (x (t)). Let’s say that the carrier is represented as, Φ (t) = √2Ps sin (2πƒct)

What is direct sequence spread spectrum (DSSS)?

In direct sequence spread spectrum (DSSS), the transmitter and receiver contain identical psuedo-random sequence generators producing a pseudo-noise (PN) signal. In the transmitter, the input data stream is XORed with the PN signal before transmission.

What is direct-sequence spread-spectrum modulation?

Lecture Notes 11: Direct-Sequence Spread-Spectrum Modulation In this lecture we consider direct-sequence spread-spectrum systems. Unlike frequency-hopping, a direct-sequence signal occupies the entire bandwidth continuously. The signal is obtained by starting with a narrowband signal and directly modulating a high bandwidth signal.

What is the phase shift of a BPSK signal?

The direct sequence BPSK (or DS/BPSK) signal is generated at the output (x (t)). Let’s say that the carrier is represented as, Φ (t) = √2Ps sin (2πƒct) Thus when m (t) is positive, there is phase shift of ‘0’ and if it is negative, there is phase shift of 180°.