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Basics of Communication (A1-A3)

Course	UNIK4700, UNIK9700
Title	Basics of Communication and Assignments
Lecture date	2013/09/10 1315-1600 h
presented	by Josef Noll
Objective	The objective of this lecture is to explain the principles of radio communication
Learning outcomes	What will we learn today Basics of radio communication Typical radio transmission What effects the signal strengths
Pensum (read before)	Read before: http://wiki.unik.no/index.php/Courses/UNIK4700radio
References (further info)	References: A Practical Evaluation of Radio Signal Strength: http://www.chriskarlof.com/papers/p41-whitehouse.pdf Propagation characteristics of wireless channels: Media:Propagation_characteristics.pdf
Keywords	SNR, Transmit Power, Scattering, Reflection, Diffraction

this page was created by Special:FormEdit/Lecture, and can be edited by Special:FormEdit/Lecture/Basics of Communication (A1-A3).

Test yourself, answer these questions

What factors affect Wireless signal strength?
Explain the meaning of the term diffraction
How is diffraction used for radio communications?
What is the difference between diffraction and interference?
What is the difference between Scattering and Diffraction?
What is non line of sight (NLOS)?
Does WiMAX possess NLOS capability?
How is UMTS different from current second generation networks?

Lecture notes

Media:UNIK4700-L2H13.pdf

earlier notes

Slide Show

Title: UNIK4700/UNIK9700 Introduction to radio propagation
Author: Josef Noll,
Footer: Basics of Communication (A1-A3)
Subfooter: UNIK4700/UNIK9700

⌘ UNIK4700 Radio and Mobility

Lecture 2: Basics of communications

⌘ Topics for programming

Propagation Models

indoor (statistical, deterministic), outdoor (rural, city), indoor-outdoor propagation
comparison to satellite link

Capacity and range

Propagation equation
Range, Capacity
"Real systems" capacity

System parameters

CDMA-2000, W-CDMA (UMTS), GSM 900, WLAN 802.11b, 802.11a, Bluetooth
Receiver sensitivity
Noise factors

Mobile/wireless communications

combine systems and discuss results

⌘ Expectations

select papers -> list of 2 selected papers to Josef (email)
- UiOLibrary how to use IEEE, ACM and other library information to search for papers
- you are able to search without VPN, but for printout of .pdf you need someone with access (Knut, Sarfraz)
- Alternative: scholar.google.com
- starting point: literature list of UNIK4700

prepare presentation (typical 35 min), focus
- explain content
- point out strengths and weaknesses
discuss with colleagues

⌘ Distribution of work

Radiation equation
- power budget, examples

Radiation and health
- absorption examples (see Cost259)

Range of wireless communications
- selected papers on comparison of theory and measurements (WLAN) -
- selected papers for GSM900, GSM1800 and WDCDMA -

System capacity
- selected papers on WLAN (802.11a and 802.11n) -
- selected papers on WDCDMA -

Propagation models
- indoor, outdoor, indoor-outdoor

Systemparamters and performance -

open

CDMA-2000, W-CDMA (UMTS), GSM 900, WLAN 802.11b, 802.11a, Bluetooth

⌘ Principles of radio communication

radio wave propagation
Electromagnetic signals
Nyquist Theorem
Signal/noise ratio
Shannon Theorem
Signal strength

⌘ What will we learn today

basics of radio communication
sampling theorem
typical radio transmission
what effects the signal strengths

⌘ Heinrich Hertz - Radiowave propagation

Basics of wave propagation:

The variation of an electrical field creates a magnetic field
The variation of a magnetic field creates an electrical field

⌘ Electromagnetic channel

The radio channel is always affected by noise, which restricts the information flow to the receiver

[Source:Neelakanta et. al., Fig1.2]

⌘ Sources of noise

Electronic parts of transmitter and receiver (components)
Spurious electromagnetics (lines radiating on the chip)
Fluctuations in power (switching CMOS circuits)

Radio

In-band interference
out-of band interference, e.g. GSM/NMT interference
radio channel, e.g. scattering, multi-path

[Source:Wikipedia, "interference"]

450px

Figure: Noise floor in a receiver

further explanations: Telektronikk 4/95, Rækken and Løvnes, Multipath propagation

Comments

in-band: a source having the same signal
out-of-band: modulations/filters which are not perfect

]] [[File:Inband-outofband.png|450px|right|Figure: In-band (top) and out-of-band interference (bottom)

explain Fourier-transform and overlap

Figure: Cell capacity (left) and system capacity (right)

The capacity of a system consists of both the cell capacity (depending mainly on OSI layer 1-3) and on network design, meaning: how much interference do I get from other cells.

Figure: UMTS macro and microcells in a 6-operator environment

In a network where the available 60 MHz in the UMTS band are distributed to 6 operators, each operator will only have 2x 10 MHz available for operation, which typically means that one frequency block (5MHz) will be used for micro-cells and the other frequency block (5 Unik/MHz) will be used for macro-cells.

Figure: Factors influencing interference (6-operator environment)

The amount of interference will depend on

the filter characteristics of the handset ( check separation)
the distance from the transmitter
the transmit power

Receiver sensitivity might play a role, but is considered as being constant in the selected frequency band.

⌘ Electromagnetic signals

Prerequisite: Ohm's law, current, dielectric constant , conductivity
- "Pappa, what is voltage?"

Alternating electric and magnetic field
Direction of wave from "right-hand rule"

[Source: Wikipedia]

⌘ Maxwell's Equation in a source free environment

Source free environment and free space:

$\nabla \cdot \vec E = 0 \qquad \qquad \qquad \ \ (1)$

$\nabla \times \vec E = -\frac{\partial}{\partial t} \vec B \qquad \qquad (2)$

$\nabla \cdot \vec B = 0 \qquad \qquad \qquad \ \ (3)$

$\nabla \times \vec B = \mu_0 \epsilon_0 \frac{\partial}{\partial t} \vec E \qquad \ \ \ (4)$

where div is a scalar function
$\fs \mbox{div}\,\vec v = {\partial v_x \over \partial x} + {\partial v_y \over \partial y} + {\partial v_z \over \partial z} = \nabla \cdot \vec v$
and curl is a vector function
$\fs \mbox{curl}\;\vec v = \left( {\partial v_z \over \partial y} - {\partial v_y \over \partial z} \right) \mathbf{i} + \left( {\partial v_x \over \partial z} - {\partial v_z \over \partial x} \right) \mathbf{j} + \left( {\partial v_y \over \partial x} - {\partial v_x \over \partial y} \right) \mathbf{k} = \nabla \times \vec v$

[Source: Wikipedia]

⌘ Wave equation

Taking the curl of Maxwell's equation

$\fs \nabla \times \nabla \times \vec E = -\frac{\partial } {\partial t} \nabla \times \vec B = -\mu_0 \varepsilon_0 \frac{\partial^2 \vec E } {\partial t^2}$

$\fs \nabla \times \nabla \times \vec B = \mu_0 \varepsilon_0 \frac{\partial } {\partial t} \nabla \times \vec E = -\mu_o \varepsilon_o \frac{\partial^2 \vec B}{\partial t^2}$

yields the wave equation:
$\fs {\partial^2 \vec E \over \partial t^2} \ - \ {c_0}^2 \cdot \nabla^2 \vec E \ \ = \ \ 0$

$\fs {\partial^2 \vec B \over \partial t^2} \ - \ {c_0}^2 \cdot \nabla^2 \vec B \ \ = \ \ 0$

with $\fs c_0 = { 1 \over \sqrt{ \mu_0 \varepsilon_0 } } = 2.99792458 \times 10^8$ m/s

[Source: Wikipedia]

⌘ Homogeneous electromagnetic wave

single frequency

$\fs \vec E(\vec r) = E_0 e^{j(\omega t - \vec k \cdot \vec r) }$ ,

$\fs \vec B(\vec r) = B_0 e^{j(\omega t - \vec k \cdot \vec r) }$ ,

[Source: Wikipedia]

where

$\fs \vec r = (x, y, z)$ and $\fs \vec k = (k_x, k_y, k_z)$ so?
$\fs j \,$ is the imaginary unit
$\fs \omega = 2 \pi f \,$ is the angular frequency, [rad/s]
$\fs f \,$ is the frequency [1/s]
$\fs e^{j \omega t} = \cos(\omega t) + j \sin(\omega t)$ is Euler's formula

with $\fs c = { c_0 \over n } = { 1 \over \sqrt{ \mu \varepsilon } }$ and $\fs n = \sqrt{ \mu \varepsilon \over \mu_0 \varepsilon_0$

room for comments

What is the difference between a static and a dynamic field
Develop the relations for a plain wave

Assume a plane wave: $E_x, H_y$ . Show that $\frac{E_x}{H_y}=Z_0 = \sqrt{\mu_0/\varepsilon_0}$

⌘ Boundary conditions

What is happening on electrical walls, magnetic walls?

Figure: Reflection of an electromagnetic wave at the ground plane

Scattering, reflection and diffraction (explain differences) are the three major components in wave propagation. Ideal reflection environments are characterised through $\fs |r| =1,\ \ \phi_r=180\deg$

⌘ Nyquist Theorem

Shannon: If a function $\fs f(t)$ contains no frequencies higher than $\fs W$ [cycles/s], it is completely determinded by giving its ordinates at serires of points spaced $\fs \frac{1}{2W}$ seconds apart

band-limitation versus time-limitation
Fourier transform

[source: Shannon, 1948]

⌘ Signal/noise ratio

$\fs \mathrm{SNR} = {P_\mathrm{signal} \over P_\mathrm{noise}}$

$\fs \mathrm{SNR (dB)} = 10 \log_{10} \left ( {P_\mathrm{signal} \over P_\mathrm{noise}} \right )$ ,

where P is average power

why talking about noise?
dB, $\fs \mbox{dB}_m,\ \mbox{dB}_a$
near-far problem

[source: Wikipedia]

⌘ Shannon Theorem

Shannons theorem will be part of next lexture...

⌘ Summary

radio wave propagation explain
Electromagnetic signals
Nyquist Theorem
Signal/noise ratio
(Shannon Theorem -> next lecture)
(Signal strength -> next lecture)

Basics of Communication (A1-A3)

Test yourself, answer these questions

Lecture notes

⌘ UNIK4700 Radio and Mobility

⌘ Topics for programming

⌘ Expectations

⌘ Distribution of work

⌘ Principles of radio communication

⌘ What will we learn today

⌘ Heinrich Hertz - Radiowave propagation

⌘ Electromagnetic channel

⌘ Sources of noise

Comments

⌘ Electromagnetic signals

⌘ Maxwell's Equation in a source free environment

⌘ Wave equation

⌘ Homogeneous electromagnetic wave

room for comments

⌘ Boundary conditions

⌘ Nyquist Theorem

⌘ Signal/noise ratio

⌘ Shannon Theorem

⌘ Summary

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