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Wireless & Mobile Networking: Mobile Radio Propagation. Azizol Bin Abdullah azizol@fsktm.upm.edu.my (A2.04). Outline. Revisit: Wireless communication -What is radio waves? Types of radio waves Propagation Mechanisms. Wireless Communication. Wireless communication:

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wireless mobile networking mobile radio propagation

Wireless & Mobile Networking:Mobile Radio Propagation

Azizol Bin Abdullah

azizol@fsktm.upm.edu.my (A2.04)

outline
Outline
  • Revisit: Wireless communication
  • -What is radio waves?
  • Types of radio waves
  • Propagation Mechanisms
wireless communication
Wireless Communication

Wireless communication:

is transferring of information over electromagnetic waves over atmospheric space(as opposed to long cable)

-Light, microwaves, x-rays, TV and radio transmissions are all kinds of electromagnetic waves.

what is radio wave
What is Radio Wave?
  • Radio waves have the longest wavelengths in the electromagnetic spectrum.

Electromagnetic Spectrum

Definition:

The electromagnetic spectrum is the distribution of electromagnetic radiation according to energy.

what is radio wave cont
What is Radio Wave?(cont..)
  • Type of Radio Wave:
    • Ground wave
    • Sky wave
    • Space wave
    • Satelite wave
  • These waves can be longer than a football field.
  • Radio waves do more than just bring music to your radio. They also carry signals for your television and cellular phones.
what is radio wave cont1
What is Radio Wave?(cont..)
  • Radio waves have frequencies ranging from almost zero Hertz up to hundreds of Giga Hertz.
  • The spectrum is usually divided up into bands, some of which are: Very Low Frequency (VLF); Low Frequency (LF); Medium Frequency (MF); High Frequency (HF); Very High Frequency (VHF); Ultra High Frequency (UHF).
radio frequency bands
Radio Frequency Bands

Band

Nomenclature

Frequency

Wavelength

ELF

Extremely Low Frequency

3 - 30 Hz

100,000 - 10,000 km

SLF

Super Low Frequency

30 - 300 Hz

10,000 - 1,000 km

ULF

Ultra Low Frequency

300 - 3000 Hz

1,000 - 100 km

VLF

Very Low Frequency

3 - 30 kHz

100 - 10 km

LF

Low Frequency

30 - 300 kHz

10 - 1 km

MF

Medium Frequency

300 - 3000 kHz

1 km - 100 m

HF

High Frequency

3 - 30 MHz

100 - 10 m

VHF

Very High Frequency

30 - 300 MHz

10 - 1 m

UHF

Ultra High Frequency

300 - 3000 MHz

1 m - 10 cm

SHF

Super High Frequency

3 - 30 GHz

10 - 1 cm

EHF

Extremely High Frequency

30 - 300 GHz

1 cm - 1 mm

Low frequency means big waves and high frequency equates to small waves. Higher frequency ‘short’ waves is better for long range transmission.

the frequency spectrum service bands and channels
The Frequency Spectrum, Service Bands, and Channels

Frequency

Spectrum

(0 Hz

to infinity)

A service band has a specific

purpose, such as FM radio or

cellular telephony.

Service bands are divided into

channels. Signals sent in different channels do not interfere with one

another.

Channels with wider bandwidths

can carry signals faster.

Channel 5

Channel 4

Service

Band

Channel 3

Channel 2

Channel 1

0 Hz

allocation of spectrum mobile service
Allocation of Spectrum: Mobile Service

1. Global System for Mobile in the 900 MHz BandUpper band: 925 to 960 MHz Lower band: 880 to 915 MHz

GSM900 Operators

a) Celcom Celcom ( Malaysia) Berhad

b) Maxis Maxis Mobile Sdn Bhd

c) DiGi DiGi Telecommunication Sdn Bhd

allocation of spectrum mobile service cont
Allocation of Spectrum: Mobile Service (cont..)

2. Global System for Mobile System in the 1800 MHz BandUpper band: 1805 to 1880 MHz Lower band: 1710 to 1785 MHz

GSM1800 Operators

a) CELCOM MOBILE Celcom Mobile Sdn Bhd

b) MAXIS (MMS) Malaysian Mobile Services Sdn Bhd

c) DIGI DiGi Telecommunication Sdn Bhd

allocation of spectrum mobile service cont1
Allocation of Spectrum: Mobile Service (cont..)

3. International Mobile Telecommunications-2000 (IMT2000)

Frequency Division Duplex (FDD)

Upper band: 2110 to 2170 MHzLower band: 1920 to 1980 MHz

Time Division Duplex (TDD)

Frequency: 1915 to 1920MHz Frequency: 2010 to 2025MHz

IMT2000 Operators

a) TM Telekom Malaysia Berhad

b) UMTS UMTS (Malaysia) Sdn Bhd

c) TT.COM TT Dotcom Sdn Bhd

d) MITV U Telecom Media Holdings Sdn Bhd

frequency vs wavelength
Frequency Vs Wavelength
  • Radio waves are transmitted as a series of cycles, one after the other. The hertz (abbreviated Hz) is equal to one cycle per second. When we say that electric power is "60 Hz," we mean it changes its direction of flow 60 times in one second.
  • The term "wavelength" is left over from the early days of radio. Back then, frequencies were measured in terms of the distance between the peaks of two consecutive cycles of a radio wave instead of the number of cycles per second. Even though radio waves are invisible, there is a measurable distance between the cycles of electromagnetic fields making up a radio wave. The distance between the peaks of two consecutive cycles is measured in meters. The relationship between a radio signal's frequency and its wavelength can be found by the following formula:
  • wavelength = 300 / frequency in MHz

As the formula indicates, the wavelength of a radio signal decreases as its frequency increases.

radio wave
Radio Wave

Wavelength

Amplitude

Frequency

Measured in Hertz (Cycles per Second)

2 Cycles in one Second, so 2 Hz

Wavelength * Frequency = Speed of Propagation

types of radio waves
Types of Radio Waves
  • Many kinds of radio waves, such as ground, space, sky and satellite waves
  • Ground wave: propagates along the surface of earth. This is the dominant mode of propagation below 2MHz
  • Sky wave propagates in the space but can return to earth by
  • reflection(in troposphere or ionosphere). The higher frequency, the long distance communication is enabled.
  • Troposphere= 1st layer above surface of earth(weather takes place)
  • Ionosphere=sufficient ions & electrons exist to reflect the electromagnetic waves
  • Satellite waves normally comes in when the frequency is >30 MHz.
propagation mechanisms
Propagation Mechanisms
  • Propagation in free space, without obstacle is the ideal situation.
  • However, when radio waves reach close to an obstacle, the following propagations effects can occur to the wave:
  • Reflection; propagating wave hits on object that is larger compared to its wavelength (tall buildings)
  • b) Diffraction; radio path is obstructed with a sharp irregular
  • edges
  • c) Scattering; objects smaller than wavelength such as lamp
  • posts, the incoming signal is scattered into several weaker
  • outgoing signals
illustrative signal and propagation
Illustrative: Signal and Propagation

Received Signal

(Attenuated &

Distorted)

Because of

Propagation Effects

Transmitted Signal

Propagation

Transmission Medium

Sender

Receiver

propagation mechanisms cont
Propagation Mechanisms(cont.)

Land Propagation

- Communication from/to a fixed station to/from a MS

- it becomes a multipath propagation channel with fading :- the signal reaches the destination using many different paths (diffraction and reflection)

- The signal strength and quality received varies according to the time

Wave propagation in the multipath channel depends on the actual environment such as:

- the antenna height

- building profile

- roads profile

- terrain profile

Wave propagation is characterized by three aspect:- path loss, slow fading and fast fading.

propagation mechanisms cont1
Propagation Mechanisms(cont.)

Path Loss (Lp)

- average propagation loss over a wide area

- it determine by the macroscopic parameter such as:- TR distance, carrier frequency, land profile.

Slow Fading (Ls)

- variation of propagation loss in local area(several 10m)/small area.

Fast Fading (Lf)

- the motion of the terminal in a standing wave that consist many diffracted waves

Doppler Effect

- the frequency of received signal will not be the same as the source when a wave source and a receiver are moving relative to one another.

propagation mechanisms cont2
Propagation Mechanisms(cont.)

Delay Spread

- spreading effect :- reflections produce more path with different path length caused the arrival time of each path is different.

Intersymbol Interference

- caused by time delayed multipath signals. Also has an impact on the burst error rate of the channel.

Coherence Bandwidth

- represent the correlation between two fading signal at different frequency

Cochannel Inteference

- caused by same frequency