First Generation 1G

1
First Generation (1G)

• Justin Champion
• C203 Ext3292
• www.soc.staffs.ac.uk/jjc1

2
FMC First Generation

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

3
FMC First Generation

• Early Wireless communications
• Signal fires !
• Morse Code
• Radio

A Radio Transmitter in Dorchester 1928
4
FMC First Generation

• 1st Generation devices
• Introduced in the UK by Vodafone and Cellnet
• 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)

5
FMC 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
FMC 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 large than required channel
  has to be allocated.

7
FMC First Generation

• FDMA

Frequency
8
FMC 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
FMC 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/hutchin
son/m0030280.html, 2004)
10
FMC 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
• 935-960 MHz downlink
• The downlink will then be allocated by the mobile
  device by adding 45Mhz to the uplink
• So
• 890 MHz uplink will be 935 MHz downlink

11
FMC 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
FMC First Generation

• 1G infrastructure

PSTN
Mobile Switching Centre
13
FMC 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
FMC First Generation

• Cellular Architecture
• Allows the area to be broken into smaller cells
• The mobile device then connects to the closest
  cell

15
FMC 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
Frequency 900
Cell
16
FMC First Generation

• Cellular Architecture continued
• There must be a distance between adjoining cells
• This distance allows communications to take place

Cell
Frequency 900
Cell
Frequency 920
Cell
Cell
Cell
Cell
Frequency 940
Cell
Cell
Frequency 960
17
FMC 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
FMC First Generation

• Radio Planning
• Logically we picture a cell as being a Hexagon
• 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

19
FMC 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
FMC 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
FMC 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
FMC First Generation

• Cellular infrastructure
• Communicating with BS1
• Moving towards BS2

Transmission BS1
Transmission BS2
BS1
BS2
23
FMC First Generation

• Cellular infrastructure
• Power of signal now weakening from BS1

BS1
BS2
24
FMC First Generation

• Cellular infrastructure
• Signal stronger so hand over to the new BS2

BS1
BS2
25
FMC 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
FMC 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
• From the point of view of this course there was
  very little computing capabilities within the
  devices
• Simply put the electronics were not readily and
  cheaply available in addition there was not the
  demand for computing services
• TACS was designed for voice services alone
• In 1985 there were 1,961 hosts on the Internet
  (http//www.isc.org/index.pl?/ops/ds/host-count-hi
  story.php)
• This was unacceptable
• GSM was introduced
• Tomorrows lecture!

27
FMC First Generation

• Summary
• 1G systems
• TACS
• Frequency Use
• Infrastructure
• Handover
• Problems