First Generation (1G)

1. First Generation (1G) Alison Griffiths C203 Ext:3292 www.fcet.staffs.ac.uk/alg1

2. First Generation • What we will look at • 1st Generation technology • Analogue signals • Frequency Division • Handover • Infrastructure

3. First Generation • Early Wireless communications • Signal fires ! • Morse Code • Radio A Radio Transmitter in Dorchester 1928

4. 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 Advanced Mobile Phone System (AMPS) • Used the 900MHz frequency range • Europe • Germany adopted C-net • France adopted Nordic Mobile Telephone (NMT)

5. 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

6. First Generation • FDMA • Breaks up the available frequency into 25 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 • Separate channels are allocated for uplink and downlink • This means no sharing of the medium is required • 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 larger than required channel has to be allocated.

7. First Generation • FDMA Frequency

8. First Generation • 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

9. First Generation • 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)

10. First Generation • Each of the mobile devices need to operate on a unique frequency • This is given to the devices by the base station when communications are initially requested • The base station will give the phone a frequency in the range • 890-915 MHz uplink • 1000 channels, 600 were used • (915M-890M=25M, each channel is 25kHz so 25e6/25e3=1000 channels) • The downlink will then be allocated by the mobile device by adding 45Mhz to the uplink • 935-960 MHz downlink • So • 890 MHz uplink will be 935 MHz downlink

11. First Generation • Three kinds of channels for communications • Fixed channels (always the same) • Paging Channels • Constant transmission by the BS • Incoming Call Signal • The device monitors this to see if another BS has a stronger signal • If it does a handover takes place • Control Channels • Information sent over this link would include • Device wishes to make a call • Carry out a hand over • Frequency to communicate upon • Dynamic channels • Voice/traffic channels • These are allocated as discussed previously by the BS as required • If a channel is not available the phone will wait a random time interval and try again

12. First Generation • 1G infrastructure PSTN Base Station Mobile Switching Centre

13. 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)

14. Cell Cell Cell Cell Cell Cell Cell Cell Cell Cell Cell Cell Cell Cell Cell Cell First Generation • Cellular Architecture • Allows the area to be broken into smaller cells • The mobile device then connects to the closest cell

15. 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 Frequency 900MHz Cell Cell Cell Cell Cell

16. First Generation • Cellular Architecture continued • There must be a distance between adjoining cells • This distance allows communications to take place MHz Cell Frequency 900 Cell Frequency 920 Cell Cell Cell Cell Frequency 940 Cell Cell Frequency 960

17. 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

18. Cell 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 buildings are the rectangles in dark green • The darker the shade of green the stronger the signal

19. 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

20. 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 • Cell sizes are flexible • Examples in the TUK TACS system were up to 50 Miles!

21. 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

22. First Generation • Cellular infrastructure • Communicating with BS1 • Moving towards BS2 Transmission BS1 Transmission BS2 BS1 BS2

23. First Generation • Cellular infrastructure • Power of signal now weakening from BS1 BS1 BS2

24. First Generation • Cellular infrastructure • Signal stronger so hand over to new MSC BS1 BS2

25. 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

26. 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!

27. First Generation • Summary • 1G systems • TACS • Frequency Use • Infrastructure • Handover • Problems