A few years after Alexander Graham Bell invented the telephone in 1876, a couple of scientists independently began doing research on sending electromagnetic signals, similar to the ones used in a telephone, through the air. The discovery of radio waves transformed communication around the world because people could send and receive messages without the use of a wire. It would only be a matter of time before the radio and the telephone would be combined into the mobile phone.
It must be mentioned that a man named Jagdish Chandra Bose was a pioneer in the field of wireless communication. However he did not believe in patenting his research because he believed that this scientific breakthrough should be available for all to take and replicate. This is why Guglielmo Marconi, and not Bose is often attributed with the discovery of wireless technology.
Before we learn about the complex system of mobile telephone networks, we should understand how the most basic two-way radio works. A two-way radio or walkie-talkie has a transmitter to send radio signals and an antenna to receive them.
A transmitter is the part of a device that has the ability to change the frequency and amplitude of a wave into an electromagnetic signal. In this case it is a sound wave. The antenna of another walkie-talkie picks up this signal and converts it back into a sound wave which we can understand. However, this system is limited because it only allows you to transmit information over 1 channel and only one person can be talking at any given time since both talking and listening occur over the same channel. Mobile phones are different because they use 1 channel to transmit and another one to receive.
Before mobile technology was developed the way it is today, there were radio phones. The radio-telephone system used one radio tower that had 25 channels. This antenna was responsible for receiving signals from one radio-phone and sending it to a desired destination. But the phones themselves were huge because they had to be powerful enough to transmit and receive signals for up to 70 kms.
What is a Mobile Network?
A mobile network avoids this problem by breaking up this area into many pieces known as cells. Each cell has its own radio tower that has a range of about 26 square kms. Think of each cell as a hexagon placed beside another hexagon, on a larger hexagonal grid.
Today, in 2012, we have phones and other hand-held devices that allow you talk on the phone, upload photographs, download music and much more, but this wasn’t always the case. Let’s see how this development came about from the early days of wireless communication.
Types of Mobile Networks
1G Network –
1G refers to the first generation of mobile communication technology. This was an analog system that was first introduced in Japan by the Nippon Telegraph and Telephone in 1979. The voice signal from the handset was was sent to a tower at a high analog frequency. The tower would pick up this signal and convert it to digital before transmitting it to another tower in the area. The second tower would locate the desired receiver, convert the digital signal back to analog, which the handset would convert into sound waves. Japan was very successful in implementing this technology and within five years it had become the first nationwide 1G network.
A single cell tower in the 1G network had a very limited capacity because each phone call used 4 channels at any given time- 2 for listening at each telephone and 2 for talking. This was not a very efficient system and was not secure because it used radio frequencies that cannot be easily encrypted for the purpose of a phone call. An added problem was that when a signal moved out of the range of one tower to another, calls would not be transferred properly and would get disconnected.
You might be wondering what exactly an analog signal is, so before we make the switch to digital, let’s find out. An analog signal is a continuous signal that fluctuates i.e. it is always evolving and every point of the signal is significant to the information it is carrying. This means that every part of an analogue signal carries important data that is different to another point on the same signal. Digital data on the other hand is a bundle of information that has to be unbundled before it can be interpreted.
2G Network –
The big breakthrough with 2G was that it was an entirely digital network. The 1G network used an analog signal to connect with cellphone towers which limited the range and the number of users that could be on a call at any given time.
The second generation (2G) mobile communication system can be divided into 3 parts- FDMA, CDMA and TDMA, which are basically different ways in which cellphones could access the channels of a tower.
FDMA (Frequency Division Multiple Access)
FDMA was not the most efficient of the three systems because while it was able to handle digital data, it was simply a more sophisticated way of transmitting analog signals. It split a single channel into uniform pieces of bandwidth and allowed multiple cellphones to access the same channel through small variations in frequency.
TDMA (Time Division Multiple Access)
One of the basic concepts of mobile communication is to allow multiple users to send and receive information over 1 channel i.e. many people could share the same bandwidth. Consider any 1 channel on a mobile tower which is able to send and receive a fixed amount of data per second. TDMA split this one second into three and allowed three different users to share each second of space on a channel. Network speeds had risen greatly after making the switch from analog to digital signals, which allowed for towers to relay messages at a fraction of a second.
CDMA (Code Division Multiple Access)
Instead of breaking up the channels into smaller parts, the CDMA system broke the information into smaller packets of information. Using a unique spreading code, these packets were spread over multiple towers along with information on its destination. Once all the packets reached the destination tower, it was reassembled into its original form and sent to the receiver in one part.
3G Network –
The third generation (3G) of mobile networking systems offered a wider variety of services than what came before and also increased the speeds at which information was relayed. The 3G network allowed people to download information at 14.4 Mb per second and an upload speed of 5.8 Mb per second. This network opened the road to accessing the internet on your mobile device and also protecting the information you sent and received much more efficiently than the 2nd generation.
4G Network –
There is a current generation of a communication network called the fourth generation (4G) that is still in its development phase, although some countries have begun implementing this technology already. Usually the quality of speed diminishes when the location of the phone is constantly moving. The 4G system increases the efficiency of the network by improving the antenna in your mobile device without compromising on design. It boasts of greater internet speeds on highly secure channels. This new network is allows people to use multimedia applications that handle audio, video, and encrypted information with very little loss of quality.
It took inventors around 100 years to combine the telephone and the radio into the mobile phone. However, the advances in mobile phone networks have grown leaps and bounds since the radio-phone was introduced in the 1970s.
As wired telephones slowly become a thing of the past, mobile phone are packed with more and more features as technology experts continually reduce the size of the device while increasing its power and efficiency. Mobile phone technology is moving at a furious pace towards creating a more connected world. These networks allow us to connect with family living in other countries, it helps scientists track important information about our planet over vast distances, and basically makes our large planet seem a little smaller and connected. So take a good look at that tiny mobile phone in your hand and know that this little piece of technology is changing the way the world communicates and interacts.
Now that you know how wireless communication works, go backwards and find out how regular telephones (with wires) work. You can start by google the words ‘how a telephone works.’
Some phones, especially those made for the US market cannot be used with SIM-cards from outside the US. Can you find out why this is?
Using your amazing research skills, find out about the different advances in radio that were put forth by Nikolai Tesla and Guglielmo Marconi.
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