First Generation Justin Champion C208 Ext:3273. First Generation What we will look at 1 st...
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Transcript of First Generation Justin Champion C208 Ext:3273. First Generation What we will look at 1 st...
First Generation
What we will look at 1st Generation technology Analogue signals Frequency Division Handover Infrastructure
First Generation
Early Wireless communications Signal fires Morse Code Radio
Radio Transmitter 1928 Dorchester
First Generation
1st Generation devices Introduced in the UK by Vodafone
January 1985 UK Technology (and Italy)
Total Access Cellular System (TACS) This was based on the American design of AMPS
Used the 900MHz frequency range Europe
Germany adopted C-net France adopted Nordic Mobile Telephone (NMT)
First Generation
Operates Frequency Division Multiple Access (FDMA)
Covered in next slide Operates in the 900MHz frequency range
Three parts to the communications Voice channels Paging Channels Control Channels
PCS – 1G to 2G technology
FDMA Breaks up the available frequency into 30 KHz channels
Allocates a single channel to each phone call The channel is agreed with the Base station before
transmission takes place on agreed and reserved channel The device can then transmit on this channel
No other device can share this channel even if the person is not talking at the time!
A different channel is required to receive The voice/sound is transmitted as analogue data, which means
that a large than required channel has to be allocated.
PCS – 1G to 2G technology
FDMA You use this technology all of the time!
Consider your radio in the house As you want different information you change the frequency
which you are receiving
PCS – 1G to 2G technology
Voice calls Are transferred using Frequency modulation The rate at which the carrier wave undulates is changed
Encoding information More resistant to interference than AM radio
(www.tiscali.co.uk/reference/encyclopaedia/hutchinson/m0030280.html, 2004)
First Generation
Infrastructure Base Station
Carries out the actual radio communications with the device
Sends out paging and control signals MSC
Takes responsibility Controls all calls attached to this device Maintains billing information Switches calls (Handover)
First Generation
Cellular Architecture Allows the area to be broken into smaller cells The mobile device then connects to the closest
cell
Cell
Cell Cell
Cell Cell
Cell Cell
Cell
Cell
Cell Cell
Cell Cell
Cell Cell
Cell
First Generation
Cellular Architecture continued Cellular architecture requires the available frequency to be
distributed between the cells If 2 cells next to each other used the same frequency each
would interfere with each other
Cell
Cell Cell
Cell
Cell Frequency 900
First Generation
Cellular Architecture continued There must be a distance between adjoining cells This distance allows communications to take place
Cell
Cell Cell
CellCell
Cell
Cell
Cell Frequency 900
Frequency 920
Frequency 940
Frequency 960
First Generation
Cellular Architecture continued This is referred to as the “Minimum Frequency Reuse Factor”
This requires proper planning and can be an issue for all radio based wireless communications
Planning the radio cell and how far a signal may go
Cell
Cell Cell
Cell
First Generation
Radio Planning Logically we picture a cell as being a
Octagon In reality the shape of a transmission will
change depending on the environment In this diagram of a cell you can see this
The building are the rectangles in dark green The darker the shade of green the stronger
the signal
Cell
Cell Cell
Cell Cell
First Generation
Radio Planning Planning needs careful thought You must cover the entire area with the minimum of base
stations Base stations cost the company money They also make the potential for radio problems greater
Simulations can be used but accurate models of the area is required Best solution is to measure the signals at various points
From this a decision can be made
Cell
Cell Cell
Cell
First Generation
Cellular infrastructure why ?? Cells with different frequencies allow devices to
move between these cells The device just informing what frequency they are
communicating at Cellular communications can only travel a certain
distance Discussed in the wireless LAN’s lecture Cell sizes are flexible
Examples in the TUK TACS system were up to 50 Miles!
First Generation
Cellular infrastructure Once you get to the ‘edge’ of a cell you will need
a handover Handover allows the user to move between cells
After a certain distance the amount of data which is sent in error becomes greater than the data sent correctly at this point you need to connect to a new cell which is closer.
TACS carries this out by monitoring the amplitude of the voice signal
First Generation
Cellular infrastructure Communicating with BS1
Moving towards BS2
BS2BS1
Transmission BS2Transmission BS1
First Generation
Handover Once a handover is decided upon by the BS
The MSC is informed All BS in the area of the current location are informed to
start paging the device The BS with the strongest signal is then handed over to The call can continue In reality a lot of calls were dropped whilst waiting for a
handover to take place Ending a call
A 8Khz tone is sent for 1.8 seconds The phone then returns to an idle state
First Generation TACS
Problems Roaming was not applicable outside of the UK
All of Europe was using different standards Different frequencies Different frequency spacing Different encoding technologies
Security Calls were easily ‘listened’ upon Limited capacity of the available spectrum Analogue signal meant a larger than required amount of the
frequency had to be allocated to each call Expansion of the network was difficult
This was unacceptable GSM was introduced
Next weeks lecture!