1. Transmission Media Wired Wireless Coaxial Twisted Pair (UTP / STP)
Optical Fibres
Wireless IR
Microwave signals
Radio Frequency

2. Wired LAN (Coaxial cable)
high capacity communication cable
using BNC Connector
2 concentric conductor
one inner (inner core)
one outer (metal mesh)
nowadays mostly for cable TV transmission
disadv :
much thicker
not flexible
more expensive (c.f. UTP / STP)

5. Wired LAN (Twisted pair)
Using ordinary copper wire
the copper wires are twisted together
to reduce crosstalk / electromagnetic interference
by electrical appliances (motors, transformers)
radio frequency interference
if the twisted pair is
enclosed inside a shield
STP
not enclosed inside a shield (unshield)
UTP
nowadays mostly for networking cabling

8. Wired LAN (Twisted pair) … cont’d
Using RJ45 connector
Adv :
more flexible
less expensive (c.f. coaxial cable)
Categories
Cat for analogue voice (old telephone system)
Cat. 2
Cat baseT Ethernet (16Mbps)
Cat. 4
Cat baseT Ethernet (100Mbps)
Ref :

9. Wired LAN (Twisted pair) … cont’d
Types of cables
Straight through cable
connecting PC to network devices (hub / switch)
Crossover cable
connection between PC & PC
connection between network device with network device
Rollover cable
with connector
RJ45 to DB-9 converter then to COM 1 or COM 2 of PC

26. Wired LAN (Optical fibres)
made up of a bundle of thin tubes of glass
thinner than a human hair
do not conduct or transmit electrical signals
not interfere by electromagnetic wave
Transmission of info via light pulse
Carry more info than copper wire at the same period of time
signal can travel a very long distance
because no / little attenuation
But fragile … need more protection
installation .. More labour intensive

27. Interference
Original Signal

28. Noise

29. When signal and noise combined together

30. Resulting Signal detected

32. Wireless LAN
use electromagnetic waves to transmit and receive data from one device to another
suitable to env. where cabling is difficult / not practical / not economical
construction site
warehouse
school campus
hospitals
usually as an extension or an alternative for a wired LAN
transmitter : Access Point (AP)

33. Wireless LAN … cont’d Using IR / radio signals / microwaves
Some of them require direct line of sight (e.g. : IR)
Signal travels in straight line
Stations using antenna & satellite
To avoid the
curvature of the Earth
Mountains
Tall buildings
Other signal obstacles
Advanced wireless technology
Eliminate the limitation of direct line-of-sight
More flexible

34. Wireless LAN … cont’d Problems faced by wireless transmission
Signals can be weakened by bad weather and solar activity
A satellite can be used for around 7-10 years
Anyone can detect the signal (Security problem)
Signal / data must be encrypted before sending

35. Advantages Wireless LAN … cont’d Easy installation
Flexibility in usage
Economical
Expandability