CDMA TECHNOLOGY FILETYPE PDF

CDMA TECHNOLOGY FILETYPE PDF

Wide band CDMA technology is selected for UTRAN air interface. WCDMA; TD- SCDMA. Base stations are referred to as Node-B and control equipment for. 3G CDMA – WCDMA and cdma W-CDMA Versus cdma [2] . [4] “ CDMA Evolution from IS, IS, to 1XTREME,” Technology Transfer Training. GSM Technology. GSM is now a worldwide standard. GSM uses Time Division Multiple Access or TDMA technology as their air interface standard. TDMA has.

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If the signal matches the desired user’s code, then the correlation function will be high and the system can extract that signal.

The jammer can either spread its energy over the entire bandwidth of the signal or jam only part of the entire signal. Each sender has a different, unique vector v chosen from that set, but the construction method of the transmitted vector is identical.

CDMA is used as the access method in many mobile phone standards. Orthogonal codes have a cross-correlation equal to zero; in other words, they do not interfere with each other. The following table explains how this works and shows that the signals do not interfere with one another:.

The technology of code-division multiple access channels has long been known.

When the receiver attempts to decode the signal using sender1’s code, the data is all zeros, therefore the cross-correlation is equal to filteype and it is clear that sender1 did not transmit any data. Channel access methods Code division multiple access Multiplexing Radio resource management Media access control.

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This article is about a channel access method. The new collaborative multi-user receiver consists of two stages: Reusing the same frequency in every cell eliminates the need for frequency planning in a CDMA system; however, planning of the different pseudo-random sequences must be done to ensure that the received signal from one cell does not correlate with the filftype from a nearby cell.

Asynchronous CDMA offers a key advantage in the flexible allocation of resources i. In a hard-hand-off situation, as the mobile telephone approaches a hand-off, signal strength may vary abruptly. CDMA can also effectively reject narrow-band interference. In this approach, instead of using one sequence per user as in conventional CDMA, the authors group a small number of users to share the same spreading sequence and enable group spreading and despreading operations.

Gold codes are an example of a PN suitable for this purpose, as there is low correlation between the codes. CDMA is a spread-spectrum multiple-access [8] technique. Since the xdma signal occupies a large bandwidth, only a small portion of this will undergo fading due to multipath at any given time.

Convolution encoding and interleaving can be used to assist in hechnology this lost data. A rake receiver combines the information from several correlators, each one tuned to a different path delay, producing a stronger version of the signal than a simple receiver with a single correlation tuned to the path delay of the strongest signal.

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Many teechnology occupy the same channel, but only users associated with a particular code can communicate. Proceedings of the Leningrad Experimental Institute of Communication: Channel access methods Media access control.

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InKupriyanovich made the new experimental “pocket” model of mobile phone. These systems were designed using spread spectrum because of its security and resistance to jamming. The following example demonstrates how each user’s signal can be encoded and decoded. If the dot product is zero, the two vectors are said to be orthogonal to each other. Wireless Communications, Principles and Practice. Channel access methods and media access control.

How Cell Phones Work

Since adjacent cells use the same frequencies, CDMA systems have the ability to perform soft hand-offs. Fundamentals and Applications Second ed. This is effectively a frequency convolution Wiener—Khinchin theorem of the two signals, resulting in a carrier with narrow sidebands.

In the analog case, a low-frequency data signal is time-multiplied with a high-frequency pure sine-wave carrier and transmitted. The separation of the signals is made by correlating the received signal with the locally generated code of the desired user. In the digital case, the sinusoidal carrier is replaced by Walsh functions. Spread spectrum in digital communications.