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. Cordless phones operating in the 900 MHz, 2.4 GHz and 5.8 GHz bands.
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.
What is Direct Sequence Spread Spectrum Technology How does it work in CDMA technology?
Direct sequence spread spectrum applications CDMA cellphone technology: The DSSS technique was used to provide a multiple access scheme that was used for 3G cellophane technology. Each mobile used a different access code or spreading code and this enabled multiple users to access the base station on the same frequency.
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.
Where is CDMA used?
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.
What CDMA used for?
CDMA (Code-Division Multiple Access) refers to any of several protocols used in second-generation (2G) and third-generation (3G) wireless communications. As the term implies, CDMA is a form of multiplexing, which allows numerous signals to occupy a single transmission channel, optimizing the use of available bandwidth.
What is the use of CDMA?
CDMA uses spread spectrum technology to transmit data. This technology permits several phones to send and receive through a single channel. Each part of these separate conversations is labeled with a specific digital code. The carriers that use CDMA technology include Sprint, Verizon, Alltel, and NEXTEL.
What is the relationship between Direct Sequence Spread Spectrum DSSS and Code Division Multiple Access CDMA )?
CDMA uses a Direct Sequence Spread Spectrum (DSSS) property where the transmitter and the receiver must use the same spreading code to transmit data. This ensured the transmission could not be decoded thereby providing room for a variety of user to transmit data over the same channel without interference.
What is direct sequence CDMA?
Direct Sequence CDMA In Direct Sequence spread spectrumtransmission, the user data signal is multiplied by a code sequence. Mostly, binary sequences are used. The duration of an element in the code is called the “chip time”. The ratio between the user symbol time and the chip time is called the spread factor.
What is direct sequence spread spectrum transmission?
In Direct Sequence spread spectrumtransmission, the user data signal is multiplied by a code sequence. Mostly, binary sequences are used. The duration of an element in the code is called the “chip time”.
What is the difference between different CDMA codes for different users?
Different CDMA users use different codes. In this example the receiver sees the signal from user 1, while the signal from user 2 is heavily attenuated by the correlator (multiplier and integrator) in the receiver.
How to retrieve the wanted signal from a CDMA receiver?
A CDMA receiver can retrieve the wanted signal by multiplying the receive signal with the same code as the one used during transmission. We find: where c1is the code sequence used by user 1, Tcis the chip duration, tdis a common time offset, shared between transmitter and receiver and Nis the length of the code sequence..