1. Wired and wireless Frequency spectrum
Spectrum & Bandwidth
Lesson 1
Wired and wireless Frequency spectrum

2. Spectrum & Bandwidth Spectrum Absolute bandwidth Effective bandwidth
range of frequencies contained in signal
Absolute bandwidth
width of spectrum
Effective bandwidth
Often just bandwidth
Narrow band of frequencies containing most of the energy

3. EM Spectrum    ISM band
902 – 928 Mhz
2.4 – Ghz
5.725 – Ghz
ISM band
AM radio
S/W radio
FM radio TV TV
cellular LF HF
VHF
UHF
SHF
EHF MF  
30kHz
300kHz
3MHz
30MHz
300MHz
30GHz
300GHz
10km
1km
100m
10m 1m
10cm
1cm
100mm
3GHz
X rays
Gamma rays 
infrared
visible UV
1 kHz
1 MHz
1 GHz
1 THz
1 PHz
1 EHz
Propagation characteristics are different in each frequency band

4. Wireless LANs (CSMA/CA)
IEEE
Bandwidth: 1 or 2 Mbps
802.11b - 11 Mbps (2.4 GHz)
802.11g - 54 Mbps (2.4 GHz)
802.11a - 54 Mbps (5 GHz)
Physical Media
spread spectrum radio (2.4 GHz)
diffused infrared (10 m)
Wireless LAN
irDA
Bluetooth

5. Wireless LANs (CSMA/CA)
IEEE
Bandwidth: 1 or 2 Mbps
802.11b - 11 Mbps (2.4 GHz)
802.11g - 54 Mbps (2.4 GHz)
802.11a - 54 Mbps (5 GHz)
Physical Media
spread spectrum radio (2.4 GHz)
diffused infrared (10 m)
Wireless LAN
irDA
Bluetooth

6. Unlicensed Radio Spectrum
33cm
12cm
5cm
26 Mhz
83.5 Mhz
125 Mhz
902 Mhz
2.4 Ghz
5.725 Ghz
928 Mhz
Ghz
5.785 Ghz
cordless phones
baby monitors
Wireless LANs
802.11
Bluetooth
Microwave oven
802.11a
Pravin AT&T Labs

7. Wireless LANs
802.11b
Standard for 2.4GHz ISM band (80 MHz)
DSSS, 1.6 Mbps, 500 ft range
Star or peer-to-peer architecture
802.11a
Standard for 5GHz NII band (300 MHz)
OFDM with time division
20-70 Mbps (adapt. modulation/coding), variable range
Aloha access, Peer-to-peer architecture
802.11g
Same as a but in the 2.4 GHz ISM band
802.11n, e
Standards being developed to include MIMO or QoS

8. Other Wireless Networks
3G Cellular mobile
Uses CDMA; 2Mb/s indoor, 384kb/s outdoor.
Technology developed and deployed.
Spectrum auctioned at over $1,000 per subscriber.
Some think this will make it too expensive.
Bluetooth
For short-range communication within a small system.
E.g.: headset to cell-phone; computer to printer.
Uses 2.45GHz unlicensed spectrum and frequency-hopping.
Up to 721kb/s data rate and about 10m.

9. Data Analog Digital Continuous values within some interval
e.g. sound, video
Digital
Discrete values
e.g. text, integers

10. Analog Transmission
Analog signal transmitted without regard to content
May be analog or digital data
Attenuated over distance
Use amplifiers to boost signal
Also amplifies noise

11. Digital Transmission Concerned with content
Integrity endangered by noise, attenuation etc.
Repeaters used
Repeater receives signal
Extracts bit pattern
Retransmits
Attenuation is overcome
Noise is not amplified

12. Acoustic Spectrum (Analog)

13. Signals Means by which data are propagated Analog Digital
Continuously variable
Various media
wire, fiber optic, space
Speech bandwidth 100Hz to 7kHz
Telephone bandwidth 300Hz to 3400Hz
Video bandwidth 4MHz
Digital
Use two DC components

14. Data and Signals
Usually use digital signals for digital data and analog signals for analog data
Can use analog signal to carry digital data
Modem
Can use digital signal to carry analog data
Compact Disc audio

15. Analog Signals Carrying Analog and Digital Data

16. Digital Signals Carrying Analog and Digital Data

17. Advantages of Digital Transmission
Digital technology
Low cost LSI/VLSI technology
Data integrity
Longer distances over lower quality lines
Capacity utilization
High bandwidth links economical
High degree of multiplexing easier with digital techniques
Security & Privacy
Encryption
Integration
Can treat analog and digital data similarly