First Generation (1G)

27
First Generation (1G) Alison Griffiths C203 Ext:3292 www.fcet.staffs.ac.uk/al g1

description

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

Transcript of First Generation (1G)

Page 1: First Generation (1G)

First Generation (1G)

Alison Griffiths

C203 Ext:3292

www.fcet.staffs.ac.uk/alg1

Page 2: First Generation (1G)

First Generation

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

Page 3: First Generation (1G)

First Generation

Early Wireless communications Signal fires ! Morse Code Radio

A Radio Transmitter in Dorchester 1928

Page 4: First Generation (1G)

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)

Page 5: First Generation (1G)

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

Page 6: First Generation (1G)

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.

Page 7: First Generation (1G)

First Generation

FDMAFrequency

Page 8: First Generation (1G)

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

Page 9: First Generation (1G)

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)

Page 10: First Generation (1G)

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

Page 11: First Generation (1G)

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

Page 12: First Generation (1G)

First Generation

1G infrastructure

Mobile Switching Centre

PSTN

Base Station

Page 13: First Generation (1G)

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)

Page 14: First Generation (1G)

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

Page 15: First Generation (1G)

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 900MHz

Page 16: First Generation (1G)

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

MHz

Page 17: First Generation (1G)

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

Page 18: First Generation (1G)

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

Cell Cell

Cell Cell

Page 19: First Generation (1G)

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

Page 20: First Generation (1G)

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!

Page 21: First Generation (1G)

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

Page 22: First Generation (1G)

First Generation

Cellular infrastructure Communicating with BS1

Moving towards BS2

BS2BS1

Transmission BS2Transmission BS1

Page 23: First Generation (1G)

First Generation

Cellular infrastructure Power of signal now weakening from BS1

BS2BS1

Page 24: First Generation (1G)

First Generation

Cellular infrastructure Signal stronger so hand over to new MSC

BS2BS1

Page 25: First Generation (1G)

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

Page 26: First Generation (1G)

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!

Page 27: First Generation (1G)

First Generation

Summary 1G systems

TACS Frequency Use Infrastructure Handover Problems