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How Do Cellular Networks Work?

Wireless
Posted by James Donovan on 25 June 2015 Connect with James on LinkedIn Estimated reading time: 3 minutes

Understanding How Cellular Networks Function:

Need clarification on the terminology and processes behind how cellular networks function?

Then read on to find out.

Firstly, an electrical signal is generated by a Transmitter. The transmit Antenna will convert that signal into Electromagnetic wave (aka RF wave) which will radiate.
An RF wave then propagates (moves through matter and/or space) and is picked up by the Receive Antenna of the Receiver which converts the RF wave back into electrical signal.

Understanding Cellular Units of Measure

Electrical power is the rate at which electrical energy is converted to another form such as motion, heat, or an electromagnetic field. Electrical Power is usually expressed in Watts (W). Watts are often cumbersome in dealing with communications systems because of the large range required. A transmitter might have 20 watts of power, while a receiver might see signals that are 0.000,000,000,000,001 watts.

For this reason the unit of measure in communication systems is the Decibel or dB. It is the smallest difference that a human ear can detect between two different sounds. Since the ear’s sensitivity follows a logarithmic rather than a linear scale, the decibel (dB) has become a unit of measure of this change. The decibel has no actual numeric value, but is used to express a ratio between two powers.

Understanding Uplink and Downlink

The uplink path is the path from the subscriber unit (mobile) to the base station and the downlink path is the path from the base station to the mobile.

One of the key elements of any radio communications system is the way in which radio communications are maintained in both of these directions. Terms including simplex, duplex, frequency division duplex (FDD), and time division duplex (TDD), are all methods that can be used.

The Progression of Cellular Network Technology

There is a constant evolution within the wireless industry in an attempt to increase transmission rates. The methods used to achieve this include:

  • increasing the amount of frequencies available
  • improving the access scheme which increases the ability to re-use frequencies
  • improving the modulation schemes used which increases the amount of information passed for the amount of energy spent
  • increasing the re-use of the spectrum

In any cellular networ system or cellular technology, it is necessary to have a scheme that enables several multiple users to gain access to it and use it simultaneously. As cellular technology has progressed different multiple access schemes have been used. They form the very core of the way in which the radio technology of the cellular system works.

There are four main multiple access schemes that are used in cellular network systems ranging from the very first analogue cellular technologies to those cellular technologies that are being developed for use in the future. The multiple access schemes are known as FDMA, TDMA, CDMA and OFDMA.

FDMA – Frequency Division Multiple Access.
TDMA – Time Division Multiple Access
CDMA – Code Division Multiple Access
OFDMA – Orthogonal Frequency Division Multiple Access

Want to learn more about these and other cellular infrastructure fundamentals? See our RF Wireless Infrastructure Fundamentals Course.