# Basics of Communication (A1-A3)

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Basics of Communication (A1-A3)

 Course UNIK4700, UNIK9700 Basics of Communication and Assignments 2017/09/05 1300-1600 h by Josef Noll The objective of this lecture is to explain the principles of radio communication What will we learn today Basics of radio communication Typical radio transmission What effects the signal strengths Read before: these slides, prepare questions identify a topic for the first presentation (assignment), see L1-notes from 30Aug2016 send me an email for your login to UNIK4700 on the wiki sign up at Google Pluss (see notes L1) References: A Practical Evaluation of Radio Signal Strength: Propagation characteristics of wireless channels: 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

Regarding Video recording of UNIK4700/9700: Just talked to Kaja: Unfortunately we have a mapping problem with the disks, DRIFT is working to fix that issues. Hope you'll get the video links within this week.

Regarding the assignments: Next week, 12Sep2017, we'll set up the dates for presentation.

earlier notes

# To Do

Towards next lecture:

• Select papers related to your topics
• Come with a suggestion on the direction of your presentation
• Josef to define a time schedule
• No assignment, talk to Josef!

# 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?

Title
UNIK4700/UNIK9700 Basics of Propagation
Author
Josef Noll,
Footer
Basics of Communication (A1-A3)
Subfooter
UNIK4700/UNIK9700

# ⌘ UNIK4700 Radio and Mobility

Lecture 2: Basics of communications

# ⌘ Principles of radio communication

• Electromagnetic signals
• Nyquist Theorem
• Signal/noise ratio
• Shannon Theorem
• Signal strength

# ⌘TOC on A1-Electromagnetic signals

Building .... Networks
History, Now and Future
History
Pioneers: Maxwell, Hertz,...
1G, 2G,... 5G networks
Frequencies and Standards
Future Challenges
A-Basics of Communication
Electromagnetic Signals
Digital communication: Signal/Noise Ratio
Signal strength and Capacity: Shannon
B-Antennas and Propagation
Free Space Propagation
Multipath Propagation, Reflection, Diffraction
Attenuation, Scattering
Interference and Fading (Rayleigh, Rician, …)
Mobile Communication dependencies
C-Propagation models
Environments (indoor, outdoor to indoor, vehicular)
Outdoor (Lee, Okumura, Hata, COST231 models)
Indoor (One-slope, multiwall, linear attenuation)
D-System Comparison
Proximity: RFID, NFC
Short Range: ZigBee, Bluetooth, ANT+,...
WLAN/Wifi/802.11...
Mobile: GSM, UMTS, IMT-A (WiMAX, LTE)
E-Mobility
Mobile Network mobility
IP mobility
F-Network Building
5G and Future Networks
5G Heterogeneous Networks
Basic Internet
Video Distribution Networks
Coverage simulations
Coverage simulations
Traffic simulations
Network Capacity simulations
Building .... Networks

# ⌘ Wave Propagation Parameters

Can also be called "Propagation constant". Somewhat misleading, as the propagation usually varies strongly.

Alternative names:

• Transmission parameters
• Propagation parameters
• Propagation coefficients
• Transmission constants
• Secondary coefficients

Propagation constant, symbol γ, is defined by the ratio between the amplitude at the source, and the amplitude at some distance x. Is a complex quantity, so we use α (attenuation constant) and β (phase constant) to define it. Attenuation constant, is the loss of signal, or attenuation of an electromagnetic wave travelling through a medium. Phase constant is the change in phase per meter, along the path travelled.

# ⌘Wave propagation and absorption mechanisms

 Band Frequency Wavelength Propagation via Very low frequency, VLF 3-30 kHz 100 - 10 km Guided between the earth and the ionosphere. Low frequency, LF 30 - 300 kHz 10 - 1 km Guided between the earth and the D layer of the ionosphere. Surface waves. Medium frequency, MF 300 - 3000 kHz 1000 - 100 m Surface waves.E, F layer ionospheric refraction at night, when D layer absorption weakens. High frequency, HF (short wave) 3-30 MHz 100-10 m E layer ionospheric refraction. F1, F2 layer ionospheric refraction. Very high frequency, VHF 30-300 MHz 10-1 m Sporadic E propagation Extremely rare F1,F2 layer ionospheric refraction during high sunspot activity up to 80 MHz. Generally direct wave. Ultra high frequency, UHF 300-3000 MHz 100-10 cm Line-of-sight propagation. Sometimes tropospheric ducting. Super high frequency, SHF 3-30 GHz 10-1 cm Direct wave. Extremely high frequency, EHF 30-300 GHz 10-1 mm Direct wave limited by absorption.

The frequencies which we use for mobile communications are ranging from 450 MHz (ICE), the old TV bands, 800-900 MHz (GSM), 1800 (GSM), 1900, 2100 MHz (UMTS), 2400 MHz (Wifi), 2650 MHz (LTE), and 5100 MHz (IEEE802.11a..). While previously frequency band were used for a specific technology, refarming started in 2012 to open for communication technologies in other bands. Examples of such refarming are LTE1800 indicating an operation of LTE in the 1800 band. Back in 2013 Apple surprised the European operators, as the iPhone came with LTE only in the 1800 band, and not, as usual in Europe, in the 2600 band.

# ⌘ What will we learn today

• sampling theorem
• 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 signals

 * Prerequisite: Ohm's law, current, dielectric constant $\epsilon_r$, conductivity $\sigma$ "Pappa, what is voltage?" Alternating electric and magnetic field Direction of wave from "right-hand rule" [Source: Wikipedia] Note: Depending on the convention, either $\vec H$ [A m] or $\vec B$ are used to indicate the magnetic field. In UNIK4700 and this compendium we use the notation of $\vec B = \mu_0 \mu_r \vec H$

### Literature:

Keywords used:

• wireless electromagnetic propagation
• wireless electromagnetic propagation parameter
• wireless propagation refraction
• wireless wave attenuation constant

Building .... Networks
History, Now and Future
History
Pioneers: Maxwell, Hertz,...
1G, 2G,... 5G networks
Frequencies and Standards
Future Challenges
A-Basics of Communication
Electromagnetic Signals
Digital communication: Signal/Noise Ratio
Signal strength and Capacity: Shannon
B-Antennas and Propagation
Free Space Propagation
Multipath Propagation, Reflection, Diffraction
Attenuation, Scattering
Interference and Fading (Rayleigh, Rician, …)
Mobile Communication dependencies
C-Propagation models
Environments (indoor, outdoor to indoor, vehicular)
Outdoor (Lee, Okumura, Hata, COST231 models)
Indoor (One-slope, multiwall, linear attenuation)
D-System Comparison
Proximity: RFID, NFC
Short Range: ZigBee, Bluetooth, ANT+,...
WLAN/Wifi/802.11...
Mobile: GSM, UMTS, IMT-A (WiMAX, LTE)
E-Mobility
Mobile Network mobility
IP mobility
F-Network Building
5G and Future Networks
5G Heterogeneous Networks
Basic Internet
Video Distribution Networks
Coverage simulations
Coverage simulations
Traffic simulations
Network Capacity simulations
Building .... Networks

# ⌘ Coding and Modulation

A modulated radio signal can be written in a general form: $C(t) = A(t) cos(2\pi f(t) t + \varphi(t))$ Any of these three parameters can be varied: amplitude-, frequency- or phase-modulation.

• Channel-coding is used to reduce bit-error-rate, e.g. through forward error correction.
• Multiplexing is used to split the total amount of radio into smaller pieces. Typical: time, frequency or code multiplex. examples

[Source:K.E. Walter, Basics of Mobile Communications]

Figure: A frequency band consists of n channels.

Example GSM: the upload band is from 880-915 Unik/MHz, which is 35 Unik/MHz. With a carrier of 200 kHz we have 175 channels, which have to be divided between the various operators.

# ⌘ Modulation types

• Frequency shift keying (FSK)
• Phase shift keying (PSK)

[Source:K.E. Walter, Basics of Mobile Communications]

# ⌘ Frequency and time division multiplexing

• Time domain, e.g. 8 slots in GSM
• Frequency domain, e.g. up- and downlink in specific bands
• Code division (CDM), specific codes

[Source:K.E. Walter, Basics of Mobile Communications]

# ⌘ Code division multiple access

UMTS as an example (in one of the future lectures)

# ⌘ A3-Digital Communication Principles

Building .... Networks
History, Now and Future
History
Pioneers: Maxwell, Hertz,...
1G, 2G,... 5G networks
Frequencies and Standards
Future Challenges
A-Basics of Communication
Electromagnetic Signals
Digital communication: Signal/Noise Ratio
Signal strength and Capacity: Shannon
B-Antennas and Propagation
Free Space Propagation
Multipath Propagation, Reflection, Diffraction
Attenuation, Scattering
Interference and Fading (Rayleigh, Rician, …)
Mobile Communication dependencies
C-Propagation models
Environments (indoor, outdoor to indoor, vehicular)
Outdoor (Lee, Okumura, Hata, COST231 models)
Indoor (One-slope, multiwall, linear attenuation)
D-System Comparison
Proximity: RFID, NFC
Short Range: ZigBee, Bluetooth, ANT+,...
WLAN/Wifi/802.11...
Mobile: GSM, UMTS, IMT-A (WiMAX, LTE)
E-Mobility
Mobile Network mobility
IP mobility
F-Network Building
5G and Future Networks
5G Heterogeneous Networks
Basic Internet
Video Distribution Networks
Coverage simulations
Coverage simulations
Traffic simulations
Network Capacity simulations
Building .... Networks

# ⌘ Chapter A3 - Digital Communication Principles

• Electromagnetic signals
• Nyquist Theorem
• Signal/noise ratio

A4-Signal Strength and Capacity

• Shannon Theorem
• Signal strength

# ⌘ Nyquist Theorem

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

[source: Shannon, 1948]

# ⌘ Hartley's law

• The amount of information that may be transmitted over a system is proportional to the bandwidth of that system.

$\mbox{Amount of information} = const \cdot BT \cdot \mathrm{log} m$

• where m is the “number of current values”, which in modern terms would be called “the size of the signalling alphabet”

Why did it take twenty years to fill the gap between Hartley’s law and Shannon’s formula? The only necessary step was to substitute 1+C/N for m in Hartley's law. Why, all of a sudden, did three or more people independently “see the light” almost at the same time? Why did neither Nyquist, nor Hartley or Küpfmüller realize that noise, or more precisely the signal-to-noise ratio play as significant a role for the information transfer capacity of a system as does the bandwidth?

[source: L. Lundheim, Telektronikk 2002]

# ⌘ 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)

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

[Source:Wikipedia, "interference"]

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

# ⌘ Signal/noise ratio

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

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

where P is average power

• dB, $\mbox{dB}_m,\ \mbox{dB}_a$
• near-far problem

[source: Wikipedia]

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

explain Fourier-transform and overlap

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.

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.

The amount of interference will depend on

1. the filter characteristics of the handset ( check separation)
2. the distance from the transmitter
3. the transmit power

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

802.11b has only three non-overlapping channels, ch 1, 6, and 11. In a normal business building radio waves will propagate not only along one floor, but also through the roof/floor. The visibility of WLAN will make it necessary to plan the frequencies in order to support the person on the ground floor with wireless access.

In UMTS coverage and capacity can be adopted not only through the power level of the transmitting unit, but also through the selection of codes. If the same code or code-class is selected in neighbouring cells, a simultaneous connection to the mobile phone can be achieved. This will increase the coverage (why?) but decrease the total capacity of the system (why?)

# ⌘ Shannon Theorem

Shannon's theorem will be part of next lecture...