Wireless was the next significant step in telecommunication after the telephone. Scientists and engineers began to fathom electromagnetic waves, they also discovered how to manipulate and exploit them. This success meant that you didn't need to have a physical connection between the sender and the receiver, enabling you to send information across huge distances - around the world, or even across space.How wireless works
Wireless works because an electromagnetic wave, passing through the air at the speed of light, can create - or 'induce' - an electrical signal in an aerial. If you can control this electromagnetic wave, then you can use it to communicate or to broadcast information.So in a radio system, information is sent from one place - the transmitter - and picked up in another - the receiver - using an electromagnetic wave to carry it.
Wireless works because an electromagnetic wave, passing through the air at the speed of light, can create - or 'induce' - an electrical signal in an aerial. If you can control this electromagnetic wave, then you can use it to communicate or to broadcast information.So in a radio system, information is sent from one place - the transmitter - and picked up in another - the receiver - using an electromagnetic wave to carry it.
Electromagnetic spectrum
When scientists first realised that electromagnetic waves could be transmitted through the air, they didn't understand the full extent or impact of what they'd discovered. As our knowledge of the electromagnetic spectrum and the properties of electromagnetic waves has increased, we have learnt to manipulate and exploit them in different ways for many different uses, from early transatlantic phone calls to today's satellite and mobile communications.
When scientists first realised that electromagnetic waves could be transmitted through the air, they didn't understand the full extent or impact of what they'd discovered. As our knowledge of the electromagnetic spectrum and the properties of electromagnetic waves has increased, we have learnt to manipulate and exploit them in different ways for many different uses, from early transatlantic phone calls to today's satellite and mobile communications.
Satellite
s
Although you can communicate over long distances with wireless, there are limits because the Earth's surface is curved and electromagnetic waves may be lost before reaching their intended destination. The solution to these limitations is to use communication satellites high above the Earth's surface to relay information around the world. Although there are now hundreds of satellites in orbit around the Earth, this scientific solution to the problem of long distance communication was thought up many years before the technology existed to achieve it.
sAlthough you can communicate over long distances with wireless, there are limits because the Earth's surface is curved and electromagnetic waves may be lost before reaching their intended destination. The solution to these limitations is to use communication satellites high above the Earth's surface to relay information around the world. Although there are now hundreds of satellites in orbit around the Earth, this scientific solution to the problem of long distance communication was thought up many years before the technology existed to achieve it.
Mobile tele
phones
Mobiles phones have changed our lives since the first ones appeared in 1985. Today's mobile phones are triumphs of miniaturisation - there's nothing else you own that's likely to fit so much technology into such a small package. It's a great combination of electronics and design, but what makes it work behind the scenes is just as important. The widespread use of mobile phones has meant huge additions to the old telephone system in the form of base stations, transmitters and antenna towers, as well as clever techniques for getting the most out of the electromagnetic spectrum. And the network also has to know where you are . . . .
phonesMobiles phones have changed our lives since the first ones appeared in 1985. Today's mobile phones are triumphs of miniaturisation - there's nothing else you own that's likely to fit so much technology into such a small package. It's a great combination of electronics and design, but what makes it work behind the scenes is just as important. The widespread use of mobile phones has meant huge additions to the old telephone system in the form of base stations, transmitters and antenna towers, as well as clever techniques for getting the most out of the electromagnetic spectrum. And the network also has to know where you are . . . .
Cells and base stations : wireless on the move
Mobile telephone networks are organised in geographic cells, and each cell has an antenna that transmits to all the mobile phones that are in its geographic area. For this reason the network must know exactly where you are as you move around.
When you move from one cell to another your identity (which is contained inside your SIM card) and your new location are automatically reported to the network's control system. Your telephone also 'reports in' to the local network every couple of minutes. You can sometimes hear the communication, as interference, if your mobile is near a loudspeaker or landline telephone.
Conversations on the move are transferred without a break from one base station to the next. And because the network knows at all times where you are (as long as you're in range of one of its base stations and switched on), you can always be contacted if someone calls you.
Mobile telephone networks are organised in geographic cells, and each cell has an antenna that transmits to all the mobile phones that are in its geographic area. For this reason the network must know exactly where you are as you move around.
When you move from one cell to another your identity (which is contained inside your SIM card) and your new location are automatically reported to the network's control system. Your telephone also 'reports in' to the local network every couple of minutes. You can sometimes hear the communication, as interference, if your mobile is near a loudspeaker or landline telephone.
Conversations on the move are transferred without a break from one base station to the next. And because the network knows at all times where you are (as long as you're in range of one of its base stations and switched on), you can always be contacted if someone calls you.
Frequency allocation and reuse : getting the most from the electromagnetic spectrum
Each network operator - such as Vodafone, 02, Orange and so on - has been given a share of the electromagnetic spectrum - a band of frequencies - for their network and their customers. But this band is not enough to give everyone a permanent connection, so advanced techniques are used to make sure that it's all being used as well as it can be, to ensure there's a slot available when you want to make a call.
When you make a call you're allocated a channel - a small part of the frequency band - but it's not permanent. When you move around and change from one cell to another this frequency may not be available, so you are changed to a vacant slot. And when you finish the call, the slot you've been using is made available for someone else. This is called frequency reuse and the concept forms the basis of having a workable cellular system. Unfortunately there's a fixed maximum capacity for each cell so sometimes you can't get a connection when all frequecy slots are already in use.
Each network operator - such as Vodafone, 02, Orange and so on - has been given a share of the electromagnetic spectrum - a band of frequencies - for their network and their customers. But this band is not enough to give everyone a permanent connection, so advanced techniques are used to make sure that it's all being used as well as it can be, to ensure there's a slot available when you want to make a call.
When you make a call you're allocated a channel - a small part of the frequency band - but it's not permanent. When you move around and change from one cell to another this frequency may not be available, so you are changed to a vacant slot. And when you finish the call, the slot you've been using is made available for someone else. This is called frequency reuse and the concept forms the basis of having a workable cellular system. Unfortunately there's a fixed maximum capacity for each cell so sometimes you can't get a connection when all frequecy slots are already in use.
