Mobile Communication Systems - Basics

Now, let us see what makes up a communication system. A very basic components are

1. SOURCE the beginning point 
2. INFORMATION or DATA to be conveyed
3. CARRIER or MEDIUM that will take data from source to destination
4. RECIPIENT

Now, the very important requirement for communication, is a MEDIUM through which information will flow from the SOURCE to the RECIPIENT. For wireless systems this medium is called the CARRIER, which consists of waves of given frequency. For mobile telephony, RADIO FREQUENCY range is used.

The carrier can be modulated in a variety of ways to embed data/information into it. It is then signaled from a transmitter. The receiving end has a receiver that captures this signals and demodulates it to decipher the embedded data/info/message.

Since there are so many different mobile carriers, to avoid exchange of signals and interference, each carrier can use only an allotted  frequency range from the spectrum. That is why the radio spectrum has become a very valuable asset.

MOBILE NETWORKS

A mobile network is a radio network distributed over huge land areas. Terminal devices or mobile phones can move around in this land areas and still communicate.

In order to support communication between subscribers we need a pair of RF channels per active call. 1 Channel requires atleast two frequencies, one for forward link and one for reverse link.

In large cities where operators could have thousands of subscribers, we would require a large number of channels. A given base station can transceive only at a given frequency range, and the number of channels would be limited. Also there is a limit to availability of spectrum. 

If an operators get a 1 MHz band, and has 12 channels to use and  only one base station to cover the entire state, then at any given time it could support only 12 active calls at max. To overcome this limitation, you have to create zones of coverage, which are called as cells. 

READ NEXT  : Frequency Reuse in Cellular Toplogy

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More or Less... We're Wireless

You may be wondering why I am posting about Wireless mobile communication systems.
They have been there since decades! What's new about them ?

Well you are right, there's nothing new about them. They have evolved for so many years. 
But the interesting thing is they don't stop evolving..  from simply "cellular technology" to 3G, 4G and 5G or the LTE advanced... wireless technology is always renewing.

This and some more following posts will help you quickly learn how wireless technology evolved and soon you will be up-to-date with recent advances.

What Qualifies to be called a Wireless Communication System?

Communication - means transfer of data from one point to another. 
Any transfer of information between two or more points that are not physically connected by wires is wireless communication. 

Therefore, even when you talk to your friend sitting beside you, technically you are communicating "wireless-ly". But since we are Engineers, let's leave aside these naive examples.

We will consider only technologically advanced wireless data transfer as wireless communication. So, more complex examples of wireless communication systems would be:

Short Distance : TV controlled by remote

OR

Long Distance : Space Radio Communication

A Piece of Fun Fact

(click on image for magnified view)

The world's first wireless telephone conversation occurred in 1880, when Alexander Graham Bell and Charles Sumner Tainter invented and patented photophone, a telephone that conducted audio conversations wirelessly over modulated light beams. 

At that time this invention was practically useless. Decades later the photophone's principles found their first practical applications in military communications and later in fiber-optic communications.

This happened in that primitive era when electricity was a luxury, and lasers had not even been conceived of in science fictions. The transmitter required a clear line-of-sight with the receiver. (As light rays were carrying the info). Another requirement was sun-light and good weather to operate.

Evolution milestones of Mobile Communication Technology

The following map summarizes the evolution of cellular technology generations.
(click on image for magnified view)

Summary of Cellular Technology Generations

Although there are so many different wireless technologies from WLAN and Bluetooth to radio space communications, for this series we will be limiting ourselves to Wireless Mobile communications, as that is the most widely used wireless technology these days.

 NEXT READ: MOBILE COMMUNICATION SYSTEM

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