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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Since adjacent cells use the same frequencies, CDMA systems have the ability to perform soft hand-offs. Fundamentals of Mobile Data Networks. In other projects Wikimedia Commons.

In general, CDMA belongs to two basic categories: In the case of IS, bit Walsh codes are used to encode the signal to separate different users. The guard bands will reduce the probability that adjacent channels will interfere, but decrease the utilization of the spectrum. If all of the users are received with the same power level, then the variance e.

If the desired user’s code has nothing in common with the signal, the correlation should be as close to zero as possible thus rechnology the signal ; this is referred to flietype cross-correlation.

Code-division multiple access – Wikipedia

One of the initial reasons for doing this was military applications including guidance and communication systems. Gold codes are an example of a PN suitable for this purpose, as there is low correlation between the codes.

These vectors will be assigned to individual users and are called the codechip codeor chipping code. To avoid confusion, people could take turns speaking time divisionspeak at different pitches frequency divisionor speak in different languages code division. Each user in synchronous CDMA uses a code orthogonal to the others’ codes to modulate their signal.


Since narrow-band interference affects only a small portion of the spread-spectrum signal, it can easily be removed through notch filtering without much loss of information. Digitally, this behaviour can be modelled by the addition of the transmission vectors, component by component. The correlation properties of the pseudo-random codes are such that this slight delay causes the multipath to appear uncorrelated with the intended signal, and it is thus ignored.

The data signal is also binary and the time multiplication is achieved with a simple XOR function.

How Cell Phones Work

InKupriyanovich made the new experimental “pocket” model of mobile phone. This is usually a Gilbert cell mixer in the circuitry. A spreading code is a pseudo-random code that has a narrow ambiguity functionunlike other narrow pulse codes. A spread-spectrum technique spreads the bandwidth of the data uniformly for the same transmitted power.

The jammer can either spread its energy over the entire bandwidth of the signal or jam only part of the entire signal. This article is about a channel access method.

GSM and CDMA – How Cell Phones Work | HowStuffWorks

Fdma serve more customers, Kupriyanovich proposed the device, which he called “correlator. CDMA is analogous to the last example where people speaking the same language can understand each other, but other languages are perceived as noise and rejected. CDMA is used as the access method in many mobile phone standards. If the signal matches the desired user’s code, then the correlation function will be high and the system can extract that signal.


Code-division multiple access CDMA is a channel access method used by various radio communication technologies. In a CDMA system, the same frequency can be used in every cell, because channelization is done using the pseudo-random codes.

Code-division multiple access

When the receiver attempts to decode the signal using sender1’s code, the data is all zeros, therefore the cross-correlation is equal to zero and it is clear that sender1 did not transmit any data. An example of orthogonal functions is shown in the adjacent picture.

Channel access methods Code division multiple access Multiplexing Radio resource management Media access control. Most modulation schemes try to minimize the bandwidth of this signal since bandwidth is a limited resource. This page was last edited on 16 Octoberat A rake receiver combines the information from several correlators, technollgy 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.

This tecgnology several users to share a band of frequencies see bandwidth. If any or all of the unwanted signals are much stronger than the techmology signal, they will overwhelm it.

This is effectively a frequency convolution Wiener—Khinchin theorem of the two signals, resulting in a carrier with narrow sidebands. For example, binary string is represented by the vector 1, 0, 1, 1.