Cdma standard network architecture

CDMA standard network architecture

Muzakbarov D

PLAN:

• Introduction
• CDMA standard
• Network architecture
• Conclusion
• References

Introduction

• The history of CDMA goes back to the distant 30s of the 20th century, when the Soviet academician Ageev Dmitry Vasilyevich published his work entitled "Code Channel Separation". At that time, there was only a method of frequency division.In the 40s, research on this topic was conducted in the USSR and the USA, and the first steps were taken on the path to the latest communication technologies. The CDMA-450 standard has also been developed in Russia, where it is used in some regions by companies such as SKYLINK, Udmurt Cellular Networks - 450, Kuzbass Cellular Communications, Moscow Cellular Communications, Uralvestkom, VolgaTelecom, DeltaTelecom, Sotel-Nizhny Novgorod and some others. It is quite possible that CDMA-450 will gradually cover more and more territories.

CDMA standart

It is based on the construction of a broadband data transmission system, which involves the multiple expansion of the message bandwidth.

The advantage of communication systems built on the principles of CDMA is the lack of frequency planning, which is necessary for efficient operation when using other methods. The capacity of this technology-based network is on average 5 times higher than in TDMA and 10 times higher than in FDMA.

Picture 1
CDMA performance

Each data source is assigned an individual code, which is used to encode the transmitted message. The receiver also knows this code, and its function is to separate the coded message of the desired sender from the entire message stream. The codes should be as similar to each other as possible. In mathematical language, the property of "similarity" is called correlation. This means that the coded message should have as little correlation as possible. Such a property has orthogonal codes, the scalar product of which is zero.

• Each data source is assigned an individual code, which is used to encode the transmitted message. The receiver also knows this code, and its function is to separate the coded message of the desired sender from the entire message stream. The codes should be as similar to each other as possible. In mathematical language, the property of "similarity" is called correlation. This means that the coded message should have as little correlation as possible. Such a property has orthogonal codes, the scalar product of which is zero.

Picture 2
Transmission and reception on a CDMA connection