Wireless Data Technologies

1
Wireless Data Technologies

• MM Clements

2
Introduction

• Wireless Data Technologies ELEE 1069
• Year 3 course
• BEng/ BSc Computer Networking
• (Server Technologies students should NOT be here!)

3
Classes

• Lecture Practical Cisco Lab  0900 - 1200
  Fridays (Term 1 only)
• Practical soldering construction work for
  antennae carried out in Hawke xxx

4
Assignments

• 1 hour Multiple Choice (MC) paper 10
• Antenna construction analysis 40
• Wireless network design 40
• Summative 1 hour MC Phase test 10

5
This week.

• Wireless modulation techniques
• Frequency vs. wavelength
• Mobile telephony
• Bluetooth
• Wireless Ethernet
• The Internet of Things

6
Wireless Technologies

• Use radio waves to carry information
• Allocated Radio Spectrum is located between 9 kHz
  and 300 GHz
• Signals are modulated onto a carrier wave
• Several modulation techniques exist
• Amplitude, Frequency, Phase

7
Transmission Bandwidths
8
Amplitude Modulation
Height or amplitude is changed to carry
information
9
Frequency Modulation
Here, the frequency is changed to carry
information while the amplitude remains constant
10
Phase Modulation
Here, the phase or position of the wave in time
is changed to carry information It is like a
mirror is placed at the change point
11
Wavelength and Frequency

• All waves can be described in terms of their
  wavelength, l and frequency, f
• These are related by c, the speed of light, a
  constant figure of 3 x 108 ms-1
• c l x f
• As l increases, f must decrease and vv.

12
Example

• The wavelength of a radio station is 209 metres.
  What is the frequency of this station?The
  equation given previously must be rearranged to
  put f on one side of the equation and the other 2
  terms (c, l) on the other side of the equation.

13
Solution
This can be solved by dividing both sides of the
equation by l c l x f l
l This is now simplified to
read c f l
14
Calculation

• c f
• l
• Add values
• 3 X 108 ms-1 1.44 x 106 Hz or 1.44 MHz
• 209 m

15
Radio Frequency Classification

• EHF Extremely high frequency (Microwaves) 1mm
  to 1cm, 30 to 300 GHz
• SHF Super high frequency (Microwaves) 1cm to
  10cm, 3 to 30 GHz
• UHF Ultrahigh frequency 10cm to 1m,
  300 MHz to 3  GHz
• VHF Very high frequency 1m to 10m,
  30 MHz to 300 MHz
• HF High frequency 10m to 100m,
  3 MHz to 30 MHz
• MF Medium frequency 100m to 1km,
  300 kHz to 3 MHz
• LF Low frequency 1km to 10km,
  30 kHz to 300 kHz
• VLF Very low frequency 10km to 100km,
  3 kHz to 30 kHz
• VF Voice frequency 100km to
  1000km, 300 Hz to 3 kHz
• ELF Extremely low frequency 1000km to 10000km,
  30 Hz to 300 Hz

16
1G, 2G, 3G

• 1G systems used analogue modulation only for
  voice transmission
• 2G GSM (Global System for Mobile Communications)
  was first used in Europe in early 1990s.  GSM
  provided voice and limited data services and used
  digital modulation with improved audio quality
  over 1G
• 2.5G systems enhanced the data capacity of GSM
  and mitigated some of its limitations. 
• 3G cellular services - Universal Mobile
  Telecommunications System (UMTS) or IMT-2000

17
4G

• Provides wireless mobile Internet access
• Download 1 Gbps, upload 500 Mbps (max)
• Launched in UK Oct 30 2012
• Mobile network operators repurposing 2G 3G
  spectra for 4G
• O2, Vodaphone have 4G
• 3 to begin Dec 2013

18
Cell Reuse in mobile telephony

• Allows same frequencies to be used over and over
  in different parts of the country
• Cells can vary in size from about 1 km radius to
  about 8 km for macrocells
• Smaller cells microcells and picocells exist in
  busier places

19
Cell Reuse Schemes
20
Base Stations

• On top of high buildings or towers
• 3 sectors help reduce co-channel interference
• A three-sectored aerial gives 3 X 120 degree
  coverage
• Divides each cell into 3 parts known as sectors.

21
Connection of the Base Stations

• Connection of the Base Stations
• The base stations are themselves connected by
  high bandwidth links to a mobile switching centre
  (MSC). The MSCs are themselves interconnected and
  also connected to the Public Switched Telephone
  Network (PSTN).

22
Backhaul Network
23
Wireless Ethernet

• Another wireless technology that has become very
  popular over the last few years is wireless
  Ethernet.
• The first was IEEE802.11a and was superseded by
  IEEE802.11b 11 Mbps
• IEEE802.11g 54Mbps
• IEEE802.11n 600 Mbps, multiple antennae
• The operating frequency for 802.11b g is 2.4
  GHz. This lies in an unlicensed band and so it is
  not necessary to purchase a licence to use this
  service.

24
Bluetooth

• Suitable for low range data communications
• Fitted in many mobile devices
• Operates at 2.4 GHz
• Interferes with IEEE802.11b g and microwave
  oven operating frequencies
• Reduces need for data cables

25
The Internet of Things

• Proposed in 1999 by Kevin Ashton
• Envisages a fully connected world of objects
• Computer control of every day objects
• Everything connected to the Internet
• Enabled using wireless technology
• Maybe using RFID, Bluetooth or ?

26
Summary

• Three main modulation techniques exist,
  Amplitude, Frequency and Phase modulation
• Wireless devices becoming ubiquitous
• Reduces need for many data cables
• Power consumption still causes problems
• Cellular systems allow for frequency reuse
• Bluetooth shares frequency range with wireless
  Ethernet and microwave ovens

27
References

• 1http//www.hpa.org.uk/radiation/understand/inform
  ation_sheets/mobile_telephony/background_info.htm