In this first post of our Wireless and Cellular Communication Course, we will get a basic overview of wireless communication systems in general, by talking about their types and advantages. We’ll also take a trip down memory lane to go through the key events in the history of communication.
Basic Communication System
A basic communication system, irrespective of the fact that it is wired or wireless, can be represented by the following block diagram:
The basic components and terminologies, which will be followed throughout the course, are:
- Transducers: Transducers are devices that convert a physical quantity into electrical signals, or vice versa. Here, the input transducer converts the input message, which could be spoken as it is in the case of a cellular network system, and converts it into electrical impulses, which is then sent. The received electrical impulses are converted back into speech at the output transducer.
- Transmitter: Transmitters are devices that convert the electrical signal into a form, say radio waves, that can be used to transmit the message signal.
- Channel: The channel is the medium through which the transmitted signal passes. It is here that it faces the danger of being attenuated or being exposed to external distortive signals called noise signals.
- Receiver: Receivers converts the transmitted signal back to electrical impulses, after receiving it. It is here that certain signal processing processes are done on the received signal to either eliminate or at least reduce, the effects of noise on the transmitted signal.
What is wireless communication?
- Wireless communication is the process of transmission of data from the sender to the receiver without the need for any sort of physical medium or connections, such as wires and cables, for propagation.
- The channel for communication is generally considered to be air and the means of propagation are radio waves.
- The frequency of the radio waves varies based on application, lower frequencies to transmit over longer distances (like Deep-Space Communication) and higher frequencies over shorter distances (like Bluetooth).
- Apart from the conventionally used radio waves, there are other methods to achieve wireless communication, which include the use of light, magnetic and electric fields or even sound, though they are quite uncommon.
- Some examples of wireless communication include cellular phones, GPS devices, TV/AC remotes, walkie-talkies, and car keys.
Advantages of Wireless Communication
Wireless communication has revolutionized the way how people communicate since its inception in 1896 when Marconi had invented the Radio. The advantages that wireless communication provide its wired counterparts are as follows:
Flexibility and Modularity
Wireless communication is said to be flexible and modular. This means that the addition of more and more users into the network is a seamless and effortless process that doesn’t require any additional infrastructure to be set up (other than getting the user a unique identification entity, such as SIM cards in cellular networks), unlike wired communication systems.
Adding to the previous factor of flexibility, the absence of the need for additional infrastructure for every new member of the network implies a lower installation cost per person. Maintenance costs are also quite low as a majority of the components of the wireless systems are not physical entities that could fall victim to wear and tear.
A major advantage of wireless communication is its ability to provide user mobility, meaning that unlike wired communication, the destination address doesn’t mean a fixed destination location. This effectively boils down to the fact that the user can be anywhere across the world (obviously somewhere where he’s able to wirelessly access the network), and he’d still be able to communicate.
Recent advances in the field of cellular wireless communication, such as the advent of 4G technology and Voice-over-LTE, have enabled higher rates of data transfer to a wider audience, without sacrificing the connectivity strength.
The wireless networks are up most of the time and can be accessed by any authorized person, from any place of his/her choice. Wireless systems also ensure that people in areas where wired communication is not possible, such as rocky terrains where laying ground lines are tough, remain connected.
History of Wireless Communication
The following image gives a brief overview of the evolution of wireless communication through the years:
Some major inventions/discoveries in wireless communication are as follows:
- In 1873, Maxwell proposed the idea of using electromagnetic waves to propagate the transmission of message signals, which is the underlying concept behind wireless communication.
- Guglielmo Marconi invented the first wireless device, the wireless Telegraph, in 1896 and was awarded the patent for his radio the same year. The very next year, the first wireless message was sent, which read “Are you ready?”, across a distance of 6km.
- Soon, advancements in radio broadcasting took place and in 1933, the first FM radio station was built in the United States.
- In 1946, the first commercial telephone service was set up by AT&T and Southern Bell in Saint Louis, Missouri, USA, and the service was made available to private customers as well.
- In 1947, a tiny device that revolutionized the computing industry was invented. The transistor, which replaced the much bigger vacuum tubes, made possible the marriage of computers and communications and also brought compactness into the picture.
- In 1954, the first among a line of transistor radios were built, which could fit in one’s pocket comfortably.
- During the 1970s and 1980s, various companies such as Bell industries and Motorola came up with their idea of a commercial cellular phone for the masses, available for the public, which also initiated the first generation(1G) of mobile telephony.
- In the 1990s, GSM came into the picture, connecting many more people, and brought about the second generation of mobile telephony(2G).
- Wireless Fidelity(WiFi) came into existence in the late 1990s. Soon after, in the year 2000, Bluetooth was invented along with the release of the third-generation (3G) of mobile telephony. These two technologies revolutionized the way people shared messages, bringing more into the wireless world.
- In 2007, Apple released its first iPhone (the first “actual smartphone”), which lead to an exponential increase in the number of smartphones in the market.
- In 2010, the fourth generation(4G) of mobile telephony rolled out, which provide facilities such as Voice over LTE.
Frequencies for Radio Communication
The most common electromagnetic waves used in communication are radio waves, and all those systems that operate with radio waves are called Radio Frequency(RF) devices. The frequency ranges from 3kHz to 300GHz, and are further divided into sub-bands, as shown in the table below:
|Name of Sub-band||Abbreviation||Frequency Range||Applications|
|Extremely Low Frequency||ELF||3 – 30 Hz||Detection of Buried Metal Objects|
|Super Low Frequency||SLF||30 – 300 Hz||Underwater Communication|
|Ultra-Low Frequency||ULF||300 – 3,000 Hz||Audio signals on Telephone|
|Very Low Frequency||VLF||3 – 30 kHz||Navigation and Position Location|
|Low Frequency||LF||30 – 300 kHz||
Weather Broadcast Stations for Air Navigation
|Medium Frequency||MF||300 – 3,000 kHz||AM Broadcasting|
|High Frequency||HF||3 – 30 MHz||Short Wave Broadcasting|
|Very High Frequency||VHF||30 – 300 MHz||FM Broadcasting, Air Traffic Control|
|Ultra-High Frequency||UHF||300 – 3,000 MHz||Microwave Ovens, Cellular Telephones|
|Super High Frequency||SHF||3 – 30 GHz||Satellite Communication, Remote Sensing|
|Extremely High Frequency||EHF||30 – 300 GHz||Radar, Radio Astronomy|
In the next post, we’ll dwell deeper into the basic cellular communication system infrastructure.