Free download complete engineering seminar Code Division Seminar ppt
Mobile communications are rapidly becoming more and more necessary for everyday activities. With so many more users to accommodate, more efficient use of bandwidth is a priority among cellular phone system operators. Equally important is the security and reliability of these calls. One solution that has been offered is a CODE DIVISION MULTIPLE ACCESS SYSTEM.
CDMA is one method for implementing a multiple access communication system. MULTIPLE ACCESS is a technique where many subscribers or local stations can share the use of the use of a communication channel at the same time or nearly so despite the fact originate from widely different locations. A channel can be thought of as merely a portion of the limited radio resource, which is temporarily allocated for a specific purpose, such as someoneâ€™s phone call. A multiple access method is a definition of how the radio spectrum is divided into channels and how the channels are allocated to the many users of the system.
Since there are multiple users transmitting over the same channel, a method must be established so that individual users will not disrupt one another. There are essentially three ways to do this.
Code Division Multiple Access is a new technology used in wireless communication devices. This technology made its commercial debut in the early nineties. Significant advantage of the CDMA is the fact that unlike other modulation schemes it does not have to allocate part of the frequency for each user. It allocates whole frequency spectrum to each user, distinguishing each signal with the unique pseudo-random sequence.
CDMA stands for "Code Division Multiple Access." It is a form of spread-spectrum, an advanced digital wireless transmission technique. Instead of using frequencies or time slots, as do traditional technologies, it uses mathematical codes to transmit and distinguish between multiple wireless conversations. Its bandwidth is much wider than that required for simple point-to-point communications at the same data rate because it uses noise-like carrier waves to spread the information contained in a signal of interest over a much greater bandwidth. However, because the conversations taking place are distinguished by digital codes, many users can share the same bandwidth simultaneously.