Wireless networks - Lecture 3: Introduction to Wireless communication

Wireless networks - Lecture 3: Introduction to Wireless communication. The main topics covered in this chapter include: multiplexing; multiplexing - carrying multiple signals; transmission mediums; propagation modes; multi-path propagation; fading;...

Wireless Networks

Lecture 3 Introduction to Wireless Communication

Dr Ghalib A Shah

Multiplexing

 Time­division multiplexing (TDM)

► Takes advantage of the fact that the achievable bit rate of 

the medium exceeds the required data rate of a digital  signal

Frequency­division Multiplexing

Time­division Multiplexing

Satellite microwave

 Transmission characteristics

► Optimum range is 1-10 GHz

► Below 1 GHz, significant natural noise (solar, galactic,

atmospheric) and manmade

► Above 10 GHz, higher attenuation due to atmospheric

Ground Wave Propagation

► AM radio

Sky Wave Propagation

Line­of­Sight Propagation

h

57

Let h1 = 100 m, h2 = 0 or the second antenna is at

ground level.

D = 3.57 ( 4/3x100)^1/2 + 0 = 41 km.

Now suppose that h2 = 10m To achieve same

distance, what must be h1?

41 = 3.57(Kh1)^1/2+(13.3)^1/2

h1 = 46.2m

Propagation Factors

 The effect of the Earth’s shape in between the

Multipath Propagation

Fading channel

 Additive white Gaussian noise (AWGN) channel

► Signal is degraded only by thermal noise

► Accurate for space communication and some wire

communication such as coaxial cable