First Generation (1G) Alison Griffiths C203 Ext:3292

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

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

First Generation 1 st 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)

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

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.

First Generation FDMA Frequency

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

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 ( 2004)

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 MHz uplink  1000 channels, 600 were used  (915M-890M=25M, each channel is 25kHz so 25e 6 /25e 3 =1000 channels) The downlink will then be allocated by the mobile device by adding 45Mhz to the uplink MHz downlink So  890 MHz uplink will be 935 MHz downlink

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

First Generation 1G infrastructure Mobile Switching Centre PSTN Base Station

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

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 Frequency 900MHz

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

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

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 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

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!

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 BS2 BS1 Transmission BS2 Transmission BS1

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

First Generation Cellular infrastructure Signal stronger so hand over to new MSC BS2 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!

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