Direct sequence spread spectrum (DSSS) transmission employs a chipping code to “spread” the transmission over a wider frequency band than it would normally occupy. DSSS is a form of CDMA (see Chapter 4). But instead of a pseudorandom binary sequence (PRBS), an 11-bit Barker code is used as the spreading sequence.

What is direct sequence spread spectrum and CDMA?

Direct sequence spread spectrum (DSSS) transmission employs a chipping code to “spread” the transmission over a wider frequency band than it would normally occupy. DSSS is a form of CDMA (see Chapter 4). But instead of a pseudorandom binary sequence (PRBS), an 11-bit Barker code is used as the spreading sequence.

Does CDMA use spread spectrum?

To permit this without undue interference between the users, CDMA employs spread spectrum technology and a special coding scheme (where each transmitter is assigned a code). CDMA optimizes the use of available bandwidth as it transmits over the entire frequency range and does not limit the user’s frequency range.

What is direct-sequence CDMA?

DS-CDMA (Direct-Sequence Code Division Multiple Access) is a multiple access scheme based on DSSS, by spreading the signals from/to different users with different codes. It is the most widely used type of CDMA.

How many types of spread spectrum techniques are used in CDMA?

Chapter three describes different techniques of spread spectrum. There are four techniques of spread spectrum namely direct sequence spread spectrum (DSSS), frequency hopping spread spectrum (FHSS), chirp spread spectrum (CSSS) and time hopping spread spectrum (THSS).

What is Direct Sequence Spread Spectrum technology How does it work in CDMA technology?

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.

How does DSSS work in CDMA technology?

Our method uses DS-CDMA based on direct-sequence spread spectrum (DSSS). The method is physical layer and a multiple-access technique (i.e., the code division multiple channel access technique) to divide the channel into subchannels, and transmits data through these subchannels.

What is Walsh code in CDMA?

Walsh Code is a group of spreading codes having good autocorrelation properties and poor cross correlation properties. Walsh codes are the backbone of CDMA systems and are used to develop the individual channels in CDMA. For IS-95, there are 64 codes available.

How does FH CDMA differ from DS-CDMA?

The devices that make use of FH-CDMA technology consume less power and are usually cost effective; however, DS-CDMA systems are more reliable and perform better. The greatest benefit of FH-CDMA is based on the coexistence of various access points in the same area, which is not possible when using direct sequence.

What is spread spectrum explain frequency hopping spread spectrum and direct sequence spread spectrum?

Frequency-hopping spread spectrum (FHSS) is a method of transmitting radio signals by rapidly changing the carrier frequency among many distinct frequencies occupying a large spectral band. The changes are controlled by a code known to both transmitter and receiver.

What is good code for CDMA?

Ideal codes for CDMA should have delta function as their autocorrelation functions, and 0 for cross-correlation functions, i.e., autocorrelation function \rho(\tau) = \delta(\tau). cross-correlation functions \rho_{i,j}(\tau)=0, for all i \neq j, for all \tau.

What are the three property of PN sequences in CDMA?

A PN sequence has many features such as having an almost equal number of zeros and ones, very low correlation between shifted versions of the sequence, and very low cross-correlation with other signals such as interference and noise.