In a synchronous system, orthogonal codes (Orthogonal Code) can be used. In asynchronous system for this, such as pseudo-random code (Pseudo-random Noise) or Gold code is used. In order to minimize mutual interference in DS-CDMA, the spreading codes with less cross-correlation should be chosen.
Which CDMA uses orthogonal codes?
Each user in synchronous CDMA uses a code orthogonal to the others’ codes to modulate their signal. An example of 4 mutually orthogonal digital signals is shown in the figure below. Orthogonal codes have a cross-correlation equal to zero; in other words, they do not interfere with each other.
Which uses orthogonal codes synchronous?
Orthogonal codes are ideal for use in perfectly synchronous scenario like downlink cellular communication. Quasi-orthogonal codes are preferred over orthogonal codes in the uplink communication where perfect synchronization cannot be achieved.
Which modulation is used in CDMA?
Techniques generally used are direct sequence spread spectrum modulation (DS-CDMA), frequency hopping or mixed CDMA detection (JDCDMA). Here, a signal is generated which extends over a wide bandwidth. A code called spreading code is used to perform this action.
How does FH CDMA differ from DS CDMA?
FH-CDMA devices use less power and are generally cheaper, but the performance of DS-CDMA systems is usually better and more reliable. The biggest advantage of frequency hopping lies in the coexistence of several access points in the same area, something not possible with direct sequence.
What is self jamming in CDMA?
Self jamming is a problem in CDMA system. Self jamming arises from the fact that the spreading sequences of different users are not exactly orthogonal. The near-far problem occurs at a CDMA receiver if an undesired user has a high detected power as compared to the desired powers.
Why is CDMA used?
CDMA technology is used in commercial cellular communications to make better use of radio spectrum when compare to other technologies. … CDMA technology is known as a spread-spectrum technique which allows many users to occupy the same time and frequency allocations in a given band and space.
How do you generate orthogonal codes?
The simplest way to get an orthogonal code dictionary is to generate a Hadamard/Walsh matrix. All the rows and columns of this matrix are mutually orthogonal. You can use a couple of its rows or columns as your codes.
What is TDMA and CDMA?
CDMA is short for Code-Division Multiple Access, a digital cellular technology that uses spread-spectrum techniques. … TDMA is short for Time Division Multiple Access, a technology for delivering digital wireless service using time-division multiplexing (TDM).
Why CDMA is needed and explain it with an example?
CDMA is a spread spectrum technique where multiple users to access the system at the same example in a cell, and of course on the same frequency. … It spreads information using codes that are unique to the mobile station in all the CDMA cellular systems.
What is CDMA ranging?
The ranging (CDMA) payload consists of a C-band transponder which facilitates accurate determination of the range of the satellite. It also carries Corner Cube Retro Reflectors (CCRR) for laser ranging.
What is difference between GSM and CDMA?
GSM stands for Global System for Mobile communication. … One of the biggest differences between these two systems is that GSM phones use SIM cards to link a particular phone with its network, while CDMA phones don’t require a SIM card because the phone itself is linked to the network.
Who invented CDMA?
NIHF Inductee Irwin Mark Jacobs Invented CDMA Technology.