How many codes in cdma

Unfortunately, due to the number of possible codes, this program is too slow for actual use. Significant optimization i. However, it was written, and is presented here should anyone find a use for it.

This was done to make the program easier to understand. We will not be developing a program to solve chip synchronization issues. Unlike the code asynchrony problem, which had a discrete and finite number of possibilities, the number of ways in which bits may be unsynchronized is infinite. Therefore, this program will be a simulation. To solve the chip synchronization issue, supersampling is used. That is, rather than sample the received waveform once per bit period, multiple samples are taken during the same period.

A supersampling value of 4, for example, should provide enough extra resolution to handle all cases i. The purpose of the simulation is to determine how accurately the transmitted signals can be decoded. This program simulates the CDMA transmission and decoding process.

It requires an input file that specifies the transmission sequence. Here is a sample input file. See the comments at the top of the program file for more details.

This program creates a set of files for every station being simulated. These results are intended to be viewed with gnuplot, a freeware plotting program. If running in a unix environment, with the sample input file given above, use the following command line: simul1 simul1.

To start gnuplot, simple type gnuplot. To view the results of the first station from within gnuplot, type load "app0. A code called spreading code is used to perform this action. Using a group of codes, which are orthogonal to each other, it is possible to select a signal with a given code in the presence of many other signals with different orthogonal codes.

CDMA allows up to 61 concurrent users in a 1. There are 64 Walsh codes available to differentiate between calls and theoretical limits.

Operational limits and quality issues will reduce the maximum number of calls somewhat lower than this value. In fact, many different "signals" baseband with different spreading codes can be modulated on the same carrier to allow many different users to be supported.

Using different orthogonal codes, interference between the signals is minimal. Conversely, when signals are received from several mobile stations, the base station is capable of isolating each as they have different orthogonal spreading codes. The following figure shows the technicality of the CDMA system. During the propagation, we mixed the signals of all users, but by that you use the same code as the code that was used at the time of sending the receiving side.

You can take out only the signal of each user. This means, CDMA operates in the presence of noise and interference. In addition, neighboring cells use the same frequencies, which means no re-use. So, CDMA capacity calculations should be very simple. No code channel in a cell, multiplied by no cell. But it is not that simple. Necessary cookies are absolutely essential for the website to function properly.

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