1

Introduction to

Mobile Communications

Lecture 1 (Overview)

Dong In Kim

School of Info/Comm Engineering

Sungkyunkwan University

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Outline

Course Basics

Course Syllabus

The Wireless Vision

Technical Challenges

Current Wireless Systems

Emerging Wireless Systems

Spectrum Regulation

Standards

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Course Information

Dong In Kim

dikim@skku.ac.kr

299-4585

office hours: Wed/Fri (4–5pm) in 23528

by appointment

TA Jong Ho Moon (299-4663 or menia1492@naver.com)

hand in all assignments to room 23517 (or in class)

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Textbooks & Course Webpage

Textbooks A. Goldsmith, Wireless Communications

D. Tse, Fundamentals of Wireless Communication

Course webpage:

http://wireless.skku.edu

Lecture notes (password protected): User name: ece

Password: cellular

Assignments

Handouts (project, old exams, etc.)

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Grading

This course will be graded on a curve.

Grade breakup:

Assignments: 20%

Term Project: 30%

Final: 50%

Final exam: December 17, Tuesday, in class

Submit homework to Wireless Comm. Lab (23517) by 5pm on the due date

Late submission of homework:

25% penalty per calendar day.

No makeup final exam:

If you miss the final exam due to a documented health problem or family catastrophe, your assignments and term project will have their weighting increased proportionally.

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Plagiarism

Please review the plagiarism page:https://www.lib.sfu.ca/help/academic-integrity/plagiarism

An assignment containing copied material

from others will receive 0 (for both students)

Second-time offender will get an F.

Cheating on an exam will receive an F.

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MATLAB Simulink

Assignments and term project include some MATLAB programming and Simulink.

Simulink:

A block diagram-based MATLAB extension that allows engineers to rapidly and accurately build computer models of dynamic systems.

Simulink is a programming language itself.

The simulink diagrams can be converted to C codes, which can be compiled for different target platforms.

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An Example of Simulink

Block diagram Scope output Spectrum analyzer output

Type “simulink” from MATLAB command line to launch the simulink window.

A short tutorial available from Handouts at the course webpage: http://wireless.skku.edu.

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Mathematical Tools For Comm Calculus, linear algebra

Signals & Systems Fourier Transform (1822)

Probability

Random Processes Will be partially covered in this course

Digital Signal Processing

Statistical Signal Processing Usually taught at graduate level

Based on Probability and Random Processes

Pioneered by Norbert Wiener in 1940’s Wiener: Went to college at age of 11, Got PhD from Harvard at 18

Information Theory and Coding Usually taught at graduate level

Also based on Probability and Random Processes

Established by Claude Shannon in 1948

These tools are also useful in many other areas

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Course Syllabus

Overview of Wireless Communications (Gold: Ch.1)

Path Loss, Shadowing, and Fading Models (Gold: Ch. 2,3)

Capacity of Wireless Channels (Gold: Ch. 4 and Tse: Ch. 5)

Digital Modulation and its Performance (Gold: Ch. 5,6)

Adaptive Modulation (Gold: Ch. 9)

Diversity (Tse: Ch. 3 and Gold: Ch. 7)

MIMO Systems (Tse: Ch. 3 and Gold: Ch. 10)

Multicarrier Modulation (Gold: Ch. 12)

Multiuser Communications & Cellular Systems

(Tse: Ch. 4,6 and Gold: Ch. 14,15)

Ultra-Low Power Communications for IoT

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Wireless History

Radio invented in the 1880s by Marconi

Many sophisticated military radio systems were developed during and after WW2

Cellular has enjoyed exponential growth since 1988, with almost 5 billion users worldwide today Ignited the wireless revolution

Voice, data, and multimedia becoming ubiquitous

Use in third world countries growing rapidly

WiFi also enjoying tremendous success and growth

MTC for massive IoT connection has been growing Low-power IoT devices will reach 150 billion in 2030!

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Future Wireless Networks

Wireless Internet access

5G & 6G Wireless Cellular

Low-Power Wide Area IoT

Battery-less Sensor Networks

Wireless Entertainment (VR)

Smart Homes/Factories/Farms

Automated Highways (V2X)

Intelligent Connectivity (ML)

Ubiquitous Communication Among People and Devices

•Hard Delay Constraints

•Hard Energy Constraints

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Design Challenges

Wireless channels appear a “random” and capacity-limited broadcast communications medium

Traffic patterns, user density/locations, and network conditions are constantly changing (time-varying)

Cellular/IoT applications are “heterogeneous” with hard constraints that must be met by the network

Energy/delay constraints change design principles across all layers of the protocol stack

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Evolution of Current Systems

Wireless systems today 4G Cellular: ~15-30 Mbps, peak rate 300 Mbps WLANs (802.11n or 802.11ac): ~600 Mbps or 3.46 Gbps

Next Generation is in the works 5G Cellular: beyond OFDM/MIMO (long-term evolution) WLANs: 60GHz (802.11ad/ay) or 2.4G & 5G (802.11ax)

Technology Enhancements Hardware: Longer batteries, lower-power circuits/processors Link: Antennas, modulation, coding, adaptation, DSP, BW Network: Cloud/Fog, mobile edge computing and cashing Application: Soft and adaptive QoS 5G NR: eMBB (energy), URLLC (delay), mMTC (scale)

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Future Generations

Rate

Mobility

2G

3/4G

5G

802.11b WLAN

2G Cellular

Other Tradeoffs:

Rate vs. Coverage

Rate vs. Delay

Rate vs. Cost

Rate vs. Energy

Fundamental Design Breakthroughs Needed

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Multimedia Requirements

Voice VideoData

Delay

Packet Loss

BER

Data Rate

Traffic

<100ms - <100ms

<1% 0 <1%

10-3 10-6 10-6

8-32 Kbps 1-100 Mbps 1-20 Mbps

Continuous Bursty Continuous

One-size-fits-all protocols and design do not work well

Wired networks use this approach, with poor results

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Quality-of-Service (QoS)

QoS refers to the requirements associated with a given application, typically rate and delay requirements.

It is hard to make an one-size-fits-all network that supports requirements of different applications.

Wired networks often use this approach with poor results, and they have much higher data rates and better reliability than wireless.

QoS for all applications requires a cross-layer design approach.

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Cross-layer Design

Application

Network

Access

Link

Hardware

Adapt across design layers

Reduce uncertainty through scheduling

Provide robustness via diversity

Delay Constraints

Rate Constraints

Energy Constraints

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Cross-layer Techniques Adaptive techniques

Link, MAC, network, and application adaptation

Resource management and allocation (power control)

Diversity techniques Link diversity (antennas, channels, etc.)

Access diversity (unicast or multicast?)

Route diversity (e.g., caching)

Application diversity

Content location/server diversity (cloud or fog?)

Scheduling Application scheduling/data prioritization

Resource reservation

Access scheduling

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Current Wireless Systems

Cellular Systems

UAV-aided Mobile Relays (3D coverage)

Wireless LANs

Satellite Systems

Bluetooth (BLE)

Zigbee radios

NB-IoT/LoRa/SigFox radios (LPWAN)

Backscatter radios (e.g., RFID)

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Cellular Systems:

Reuse channels to maximize capacity

Geographic region divided into cells Frequency/timeslots/codes/ reused at spatially-separated locations.

Co-channel interference between same color cells.

Base stations/MTSOs coordinate handoff and control functions

Shrinking cell size increases capacity, as well as networking burden

BASE

STATION

MTSO

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Cellular Phone Networks

BSBS

MTSOPSTN

MTSO

BS

Seoul

DaejeonInternet

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4/5G Cellular Design

Data is bursty, whereas voice is continuous Typically require different access and routing strategies

4/5G “widens the data pipe”: 15-30 Mbps (4G), 150-200 Mbps (5G), 802.11ac (3.46 Gbps) Standard based on OFDM/MIMO (long-term evolution) 50 ms delay (4G), 1 ms delay for URLLC (5G)

Evolution of existing systemsLTE (4G), LTE-Advanced (4G+) 5G NR (eMBB/URLLC/mMTC)

What is beyond 5G? Intelligent connectivity for smart worldMachine learning meets mobile communications!

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Unmanned Aerial Vehicles (UAV)

UAV-aided ubiquitous coverage

UAV-aided relaying

UAV-aided information

dissemination and data collection

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Wireless Local Area Networks

WLANs connect “local” computers (100m range)

Breaks data into packets

Channel access is shared (random access)

Backbone Internet provides best-effort service

Poor performance in some apps (e.g., video)

01011011

Internet

Access

Point

0101 1011

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Wireless LAN Standards

802.11b (Old – 1990s) Standard for 2.4GHz ISM band (80 MHz) Direct sequence spread spectrum (DSSS) Speeds of 11 Mbps, approx. 500 ft range

802.11a/g (Middle Age– mid-late 1990s) Standard for 5GHz NII band (300 MHz) OFDM in 20 MHz with adaptive rate/codes Speeds of 54 Mbps, approx. 100-200 ft range

802.11n/ac/ax (4G/5G/6G), 802.11ad/ay (7G) Standard in 2.4GHz and 5GHz band (4G/5G/6G) Adaptive OFDM /MIMO in 20/40 MHz (2-4 antennas) Speeds up to 600 Mbps/3.46 Gbps, approx. 200 ft range Standard in 60GHz band (7G) Speeds up to 7 Gbps/20 Gbps, currently 11 ft range

Many WLAN

cards have

all 3 (a/b/g)

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Satellite Systems

Cover very large areas

Different orbit heights GEOs (39000 Km) versus LEOs (2000 Km)

Optimized for one-way transmission Radio (XM, Sirius) and movie (SatTV, DVB/S) broadcasts

Most two-way systems struggling or bankrupt

Global Positioning System (GPS) use growing

Satellite signals used to pinpoint location

Popular in cell phones, PDAs, and navigation devices

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Bluetooth (BLE)

Cable replacement RF technology (low cost)

Short range (10m, extendable to 100m)

2.4 GHz band (crowded)

1 Data (700 Kbps) and 3 voice channels

Widely supported by telecommunications, PC, and

consumer electronics companies

Few applications beyond cable replacement

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IEEE 802.15.4 / ZigBee Radios

Low-Rate WPAN

Data rates of 20, 40, 250 kbps

Star clusters or peer-to-peer operation

Support for low latency devices

CSMA-CA channel access

Very low power consumption

Frequency of operation in ISM bands

Focus is primarily on radio and access techniques

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NB-IoT/LoRa/SigFox Radios

All low-power wide-area network (LPWAN).

NB-IoT is a cellular-grade wireless technology that uses

OFDM modulation, providing high performance at the cost of

more complexity and greater power consumption.

LoRa is a non-cellular modulation technology for LoRaWAN.

LoRaWAN uses unlicensed spectrum that can also be used by

non-mobile operator customers (e.g., Things Network).

SigFox has the lowest cost radio modules (<$5, compared to

~$10 for LoRa and $12 for NB-IOT) and is for uplink only.

SigFox sends very small amounts of data (12 bytes) very

slowly (300 baud) using BPSK, so long-range capabilities.

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NB-IoT/LoRa/SigFox Radios

LoRa uses a chirped spread spectrum (CSS) signaling.

LoRaWAN is an asynchronous ALOHA-based protocol.

LoRaWAN is designed around a 1% duty cycle limit

driven by the European ETSI requirements.

LoRa is a half-duplexing technology, and it is important

to prevent up/down collisions.

Receiver sensitivities of more than -130dBm in LPWAN

technologies, compared with the -90 to -110dBm in

many traditional wireless technologies.

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Tradeoffs

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Spectrum Regulation

Spectral Allocation in US controlled by FCC

(commercial) or OSM (defense)

FCC auctions spectral blocks for set applications.

Some spectrum set aside for universal use

Worldwide spectrum controlled by ITU-R

Regulation is a necessary evil.

Innovations in regulation being considered worldwide,

including underlays, overlays, and cognitive radios

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US Spectrum allocation today

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Coexistence Challenge: Many devices use the same radio band

Technical Solutions:

Interference Avoidance or Cancellation

Smart/Cognitive Radios

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Next-Generation DevicesEverything Wireless in One Device

Multiradio Integration Challenges

RF Interference

Where to put antennas

Size

Power Consumption

Cellular

AppsProcessor

BT

MediaProcessor

GPS

WLAN

Wimax

DVB-H

FM/XM

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Standards

Interacting systems require standardization

Companies want their systems adopted as standard

Alternatively try for de-facto standards

Standards determined by TIA/CTIA in US

IEEE standards often adopted

Process fraught with inefficiencies and conflicts

Worldwide standards determined by ITU-T In Europe, ETSI is equivalent of IEEE

Standards for current systems are summarized in Appendix D.

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Emerging Systems

Ad-hoc/mesh wireless networks

Wireless sensor networks

Distributed control networks

Ultra-low power backscatter networks

Wireless-powered communication networks

Metasurface-based “programmable” wireless

environments

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Ad-Hoc/Mesh Networks

ce

Outdoor (municipal) Mesh

Indoor Mesh

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Design Issues

Ad-hoc networks provide a flexible network infrastructure for many emerging applications.

The capacity of such networks is generally unknown.

Transmission, access, and routing strategies for ad-hoc networks are generally ad-hoc.

Cross-layer design critical and very challenging.

Energy constraints impose interesting design tradeoffs for communication and networking.

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Wireless Sensor NetworksData Collection and Distributed Control

•Hard Energy Constraints

•Hard Delay Constraints

•Hard Rate Requirements

Nodes can cooperate in transmission, reception, compression, and signal processing.

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Energy-Constrained Nodes

Each node can only send a finite number of bits.

Transmit energy minimized by maximizing bit time

Circuit energy consumption increases with bit time

Introduces a delay versus energy tradeoff for each bit

Short-range networks must consider transmit, circuit, and processing energy.

Sophisticated techniques not necessarily energy-efficient.

Sleep modes save energy but complicate networking.

Changes everything about the network design:

Bit allocation must be optimized across all protocols.

Delay vs. throughput vs. node/network lifetime tradeoffs.

Optimization of node cooperation.

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Distributed Control over

Wireless Links

Packet loss and/or delays impacts controller performance.

Controller design should be robust to network faults.

Joint application and communication network design.

Automated Vehicles

- Cars

- UAVs

- Insect flyers

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Next Generation IoT ScenariosEnhanced Traditional Use Cases

Smart OfficePublic Sensor

Network

Internet of

VehicleSmart HomeSmart Shelf

Self-Organized

Network (SON)

• Most of current IoT devices such as NB-IoT, ZigBee, LoRa, SigFox,

BlueTooth, requires carry-on power supply (plug-in/battery). High

power consumption, short transmission distance limits their growth.

• RFID also suffers the weakness of very short range, non-SON, non-

convergence (Island Network Topology)

Needs of Low Power

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Next Generation IoT Scenarios

海报

可穿戴设备标志

警示

Sensing around cellphone/car Embedded Health Monitor

New Use Cases

Dense Drone Group Dense Robotics Group

Smart ManufactureDigital Twins

Real time, Dense,

High Speed

Sensing System

with the center of

cellphone

Industrial IoT

• Jump out of the limitations of simple RFID structure

• Super long distance

• Massive clients access

• Global Service

Energy-free IoT

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Ultra-Low Power Communications

Ultra Low Power: backscattering

High performance active Reader/Base Station

Energy-free/passive IoT devices (tag-like IoT stations)

Long Distance: 50-100 meters DL/UL transmission range

Massive Access: 10 thousands IoT stations/tags connection

within one small cell

Band: ISM-915MHz/2.4GHz

Rate: 0.1-1k bps

Tx EIRP: 36dBm (follow regulations of different regions)

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Ambient Backscatter

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Bistatic Backscatter

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Wireless-Powered Comm Networks

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Programmable Wireless Environments

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Main Points

The wireless vision encompasses many exciting systems and applications

Technical challenges transcend across all layers of the system design.

Cross-layer design emerging as a key theme in wireless.

Existing and emerging systems provide excellent quality

for certain applications but poor interoperability.

Standards and spectral allocation heavily impact the evolution of wireless technology