introduction to mobile communications lecture 1...
TRANSCRIPT
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
299-4585
office hours: Wed/Fri (4–5pm) in 23528
by appointment
TA Jong Ho Moon (299-4663 or [email protected])
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