First Generation

Justin Champion

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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

FDMAFrequency

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)

PCS – 1G to 2G technology

1G infrastructure

Mobile Switching Centre

PSTN

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

Cellular infrastructure Power of signal now weakening

BS2BS1

First Generation

Cellular infrastructure Paging signal stronger so hand over to new MSC

BS2BS1

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