Chapter 1

INTRODUCTION

Based on the slides of Dr. Andrea Goldsmith, Stanford University and Dr. Dharma P. Agrawal, University of Cincinnati

Course Objectives:

� This course will cover the fundamental aspects of wireless networks, withemphasis on current and next-generation wireless networks. Variousaspects of wireless networking will be covered including: fundamentals ofcellular communication, mobile radio propagation, multiple accesstechniques, mobility support, channel allocation, Wireless PAN/LAN/MANstandards, mobile ad-hoc networks, wireless sensor networks, Internet ofThings (IoT), and routing in wireless and mobile networks.

� The goal of this course is to introduce the students to state-of-the-artwireless network protocols and architectures with emphasis on theInternet of Things (IoT).

� We will introduce the students to wireless networking research and guidethem to investigate novel ideas in the area via semester-long researchprojects (IoT theme).

� We will also look at industry trends and discuss some innovative ideasthat have recently been developed. Some of the course material will bedrawn from research papers, industry white papers and Internet RFCs.

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� Ignited the recent wireless revolution

� Ancient Systems: Smoke Signals, Carrier Pigeons, …

Exciting Developments

� Internet and Mobile use exploding

� Wireless LANs growing rapidly

� Huge cell phone popularity worldwide

� Emerging systems such as Bluetooth,

UWB, Zigbee, LTE, and WiMAX opening

new doors

� Internet of Things (IoT) and Smart Objects

� Military and security wireless needs

� Important interdisciplinary applications

5

Future Wireless Networks

Wireless Internet access

Nth generation Cellular

Wireless Ad Hoc Networks

Sensor Networks

Wireless Entertainment

Smart Homes/Spaces

Internet of Things (IoT)

Automated Highways

All this and more…

Ubiquitous Communication Among People and Devices

•Hard Delay Constraints

•Hard Energy Constraints

6

Design Challenges

� Wireless channels are a difficult and capacity-limited broadcast communications medium

� Traffic patterns, user locations, and network conditions are constantly changing

� Applications are heterogeneous with hard constraints that must be met by the network

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

� Location-aware services.

� Applications, applications, applications!

7

Radio Propagation Effects

Transmitterd

Receiver

hb

hm

Diffracted

Signal

Reflected Signal

Direct Signal

Building

8

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

Quality-of-Service (QoS)

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

� It is hard to make a 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.

Crosslayer Design

� Application

� Network

� Access

� Link

� Hardware

Delay Constraints

Rate Constraints

Energy Constraints

Channel-State

Adapt across design layers

Reduce uncertainty through scheduling

Provide robustness via diversity

Current Wireless Systems

� Cellular Systems

� Wireless LANs

� Satellite Systems

� Bluetooth

� Ultrawideband radios

� Zigbee radios

Fundamentals of Cellular Systems

Illustration of a cell with a mobile station and a base station

BS

MS

Cell

Hexagonal cell area

used in most models

Ideal cell area

(2-10 km radius)

Alternative

shape of a cell

MS

FDMA (Frequency Division Multiple Access)

User 1

User 2

User n

…Time

Frequency

Frequency Reuse

14

15

FDMA Bandwidth Structure

1 2 3…

nFrequency

Total bandwidth

4

FDMA Channel Allocation

Frequency 1 User 1

Frequency 2 User 2

Frequency n User n

Base Station

… …

Mobile Stations

OFDM� Conceptually, OFDM is a specialized FDM, the additional constraint

being: all the carrier signals are orthogonal to each other.

� In OFDM, the sub-carrier frequencies are chosen so that the sub-carriers are orthogonal to each other, meaning that cross-talk between the sub-channels is eliminated and inter-carrier guard bands are not required. This greatly simplifies the design of both the transmitter and the receiver; unlike conventional FDM, a separate filter for each sub-channel is not required.

Used also in DSL Modems

Used in Dual-Tone Multi-Frequency (DTMF)

MIMO� In radio, multiple-input and multiple-output,

or MIMO is a method for multiplying the capacity of a radio link using multiple transmit and receive antennas to exploit multipath propagation. MIMO has become an essential element of wireless communication standards including IEEE 802.11n (Wi-Fi), IEEE 802.11ac (Wi-Fi), HSPA+ (3G), WiMAX (4G), and Long Term Evolution (4G).

Analogy: Think of a shower head ☺

TDMA (Time Division Multiple Access)

Use

r 1

Use

r 2

Use

r n

…

Time

Frequency

TDMA Frame Structure

1 2 3…

nTime

Frame

4

TDMA Frame Illustration for Multiple Users

Time 1

Time 2

Time n……

Base Station

User 1

User 2

User n

…

Mobile Stations

CDMA (Code Division Multiple Access)

Use

r 1

Time

Frequency

Use

r 2

Use

r n

Code

...

Transmitted and Received Signals in a

CDMA System

Information bits

Code at

transmitting end

Transmitted signal

Received signal

Code at

receiving end

Decoded signal

at the receiver

Frequency Hopping

Frequency

f5

f4

f3

f2

f1

Frame Slot

Time

Cellular System Infrastructure

BS

Service area

(Zone)

Early wireless system: Large zone

Cellular System: Small Zone

BS BS

BS BS BS

BS BS

Service area

Cellular Systems:Reuse channels to maximize capacity

� Geographic region divided into cells� Frequencies/timeslots/codes reused at spatially-separated

locations.� Co-channel interference between same color cells.� Base stations/MSCs coordinate handoff and control functions� Shrinking cell size increases capacity, as well as networking

burden

BASE

STATION

MSC

Home phone

PSTN

MSC

BSC …

BS

…

…

MS

…

BS MS

BSC

BS MS

…

BS MS

BSC

BS MS

…

BS MS

BSC

BS MS

…

BS MS

MSC

MS, BS, BSC, MSC, and PSTN

Control and Traffic Channels

Base StationMobile Station

Steps for a Call Setup from MS to BS

BS MS

1. Need to establish path

2. Frequency/time slot/code assigned

(FDMA/TDMA/CDMA)

3. Control Information Acknowledgement

4. Start communication

Steps for a Call Setup from BS to MS

BS MS

2. Ready to establish a path

3. Use frequency/time slot/code

(FDMA/TDMA/CDMA)

4. Ready for communication

5. Start communication

1. Call for MS # pending

Cos(x) is an even function: f(x) = f(-x)

A Simplified Wireless Communication

System Representation

Information to

be transmitted

(Voice/Data)

Coding Modulator Transmitter

Information

received

(Voice/Data)

Decoding Demodulator Receiver

Antenna

AntennaCarrier

Carrier

ITU-T Framework

IEEE 802.11 – WLAN (wireless local area network)

IEEE 802.16 – WMAN (wireless metropolitan area network)

3GPP – WBA (wireless broadband access)

ITU-T – United Nations telecommunications standards

organization

Accepts detailed standards contributions from 3GPP, IEEE

and other groups

Pervasive connectivityWLAN - WMAN - WWAN

Source: 4G Wireless Evolution Conference.

GSM, CDMA, UMTS…3GPP

802.16 WiMAX

802.11 Wi-Fi

802.15.3Bluetooth60 GHzUWB

802.22

LocalMetro

Regional

Personal

Wide

TVWS

Source: 4G Wireless Evolution Conference.

ITU: International Mobile Telecommunications

� IMT-2000� Global standard for third generation (3G) wireless communications� Provides a framework for worldwide wireless access by linking the diverse

systems of terrestrial and satellite based networks. � Data rate limit is approximately 30 Mbps � Detailed specifications contributed by 3GPP, 3GPP2, ETSI and others

� IMT-Advanced� New generation framework for mobile communication systems beyond

IMT-2000 with deployment around 2010 to 2015 � Data rates to reach around 100 Mbps for high mobility and 1 Gbps for

nomadic networks (i.e. WLANs)� IEEE 802.16m working to define the high mobility interface� IEEE 802.11ac and 802.11ad VHT (very high throughput) working to

define the nomadic interface

Source: 4G Wireless Evolution Conference.

Wireless Local Area Networks (WLANs)

� 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

History of IEEE 802.11

� 1989: FCC authorizes ISM bands(Industrial, Scientific and Medical)

� 900 MHz, 2.4 GHz, 5 GHz

� 1990: IEEE begins work on 802.11

� 1994: 2.4 GHz products begin shipping

� 1997: 802.11 standard approved

� 1998: FCC authorizes the UNII (Unlicensed National Information Infrastructure) Band - 5 GHz

� 1999: 802.11a, b ratified

� 2003: 802.11g ratified

� 2006: 802.11n (600 Mbps) draft 2 certification by the Wi-Fi Alliance begins

20??: 802.11 ac/ad: 1 Gbps Wi-Fiac (5 GHz)Ad: (60 GHz, millimeter wave)

802.11 has pioneered commercial deployment of OFDM and MIMO – key wireless signaling technologies today

Source: 4G Wireless Evolution Conference.

Satellite Systems

� Cover very large areas

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

� Optimized for one-way transmission� GPS, Radio (XM, DAB) and movie (SatTV)

broadcasting

� Most two-way systems struggling or bankrupt� Expensive alternative to terrestrial system� Are they coming back???

Bluetooth

� 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

Ultrawideband Radio (UWB)

� UWB is an impulse radio: sends pulses of tens

of picoseconds(10-12) to nanoseconds (10-9)

� Duty cycle of only a fraction of a percent

� A carrier is not necessarily needed

� Uses a lot of bandwidth (GHz)

� Low probability of detection

� Excellent ranging capability

� Multipath highly resolvable: good and bad� Can use OFDM to get around multipath problem.

IEEE 802.15.4 / ZigBee Radios

� Low-Rate Low-Cost 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

Data rate

10 kbits/sec

100 kbits/sec

1 Mbit/sec

10 Mbit/sec

100 Mbit/sec

0 GHz 2 GHz1GHz 3 GHz 5 GHz4 GHz 6 GHz

802.11a

UWB

ZigBee

Bluetooth

ZigBee

802.11b

802.11g

3G

UWB

Range

1 m

10 m

100 m

1 km

10 km

0 GHz 2 GHz1GHz 3 GHz 5 GHz4 GHz 6 GHz

802.11a

UWB

ZigBee BluetoothZigBee

802.11b,g

3G

UWB

Power Dissipation

1 mW

10 mW

100 mW

1 W

10 W

0 GHz 2 GHz1GHz 3 GHz 5 GHz4 GHz 6 GHz

802.11a

UWB

UWB

ZigBee

Bluetooth

ZigBee

802.11bg3G

Emerging Systems

� Ad hoc wireless networks

� Sensor networks

� Distributed control networks

Ad-Hoc and Vehicular Networks

� Peer-to-peer communications.

� No backbone infrastructure.

� Routing can be multihop.

� Topology is dynamic.

� Fully connected with different link SIRs

� IEEE 802.11s and IEEE 802.11p (WAVE)

� Cognitive Radio IEEE 802.11af

� IEEE 802.22 (WRAN; TV White Spaces)

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.

� Crosslayer design critical and very challenging.

� Energy constraints impose interesting design tradeoffs for communication and networking.

Sensor NetworksEnergy is the driving constraint

�Nodes powered by nonrechargeable batteries�Data flows to centralized location.�Low per-node rates but up to 100,000 nodes.�Data highly correlated in time and space.�Nodes can cooperate in transmission, reception,

compression, and signal processing.� IEEE 802.11ah (900 MHz)

The Internet of Things (IoT) is the interconnection of uniquely identifiable embedded computing devices within the existing Internet infrastructure.

Projected market share of dominant IoT applications by 2025

The whole annual economic impact caused by the IoT is estimated to be in range of $2.7 trillion to $6.2 trillion by 2025

Internet of Things (IoT)� Internet: Interconnected computer networks, based on a

standard communication protocol (TCP/IP)

� Things: any unique object in the world

� Internet of Things: Internet Connected Objects (ICOs)

uniquely addressable, based on standard communication

protocol

� Example of IoT: Imagine when you approach your home,

your car send signals to open garage door, turn on air

condition/ heat system, lights, TV, Stove, etc. to find

everything ready for you, making your life easier and save

your money buy saving energy.

History of IoT

� IoT was originally introduced by the Auto-ID

research center at MIT (Massachusetts Institute)

in 1999

� Founded by Kevin Ashton, David Brock and

Sanjay Sarma to develop the Electronic Product

Code or EPC to uniquely identify products

Source: Government Accountability Office (GAO)

RFID (Radio Frequency Identification)

� Microchip used for tagging objects for automated identification

� RFID systems consist of a reading device called a reader, and one or more

tags

� The reader is a powerful device with memory and computational resources

� Able to identify objects wirelessly (track things or send specs info.)

� Active tags can sense the channel, detect collisions, reliable, accurate,

expensive, contains transmitter, and power source like battery.

� Passive tags have limited computational capacity, no ability to sense the

channel, detect collisions, doesn’t contain transmitter, and power source

� Semi-passive tags have an on-board power source that can be used to

energize their microchip, contains power source but without transmitter

Corresponding NodeHome Agent

ReaderRFID Tag

IPv6 request

IPv6 response

RFID request

RFID response

IPv6 request

IPv6 response

2

5

6

1

3

4

Source : Sandra Dominikus

Simple scenario of RFID functionality

Architecture of IoT

Source: Future Internet , 2012

Network Layer Secure Transmission

Wifi, Bluetooth, ZigBee, etc

Perception LayerPhysical Objects

RFID, Barcode, Infrared Sensors

Middleware Layer

Info Processing

Ubiquitous Computing Database

Service Management Decision Unit

Application LayerSmart Applications and Management

Business Layer Business Models Flowcharts

System Management Graphs

IoT layers - Perception (Device) Layer

� Perception (Device) Layer:

� Consists of the physical objects and sensor

devices

� The sensors can be RFID, 2D-barcode, or any

sensor depending on required functionality

� Collection of information by the Sensors

� Collected information passed to Network layer for

secure transmission to the information processing

system in middleware layer

� Network Layer (Transmission):

�Transfer information securely from

sensor devices in Perception

(device) layer to the information

processing system in Middleware

layer

IoT layers - Network Layer

IoT layers - Middleware Layer � Middleware Layer:

� Middleware is the software the connects software

components together.

� Responsible for the service management and has

link to the database related with each sensor.

� Performs information processing and ubiquitous

computation and makes a decision by sending

specific sensor info to the related applications in

Application layer to do specific jobs.

� Application Layer:

� Provides a global management for the

application based on the objects processed in

Middleware layer

� Applications can be smart health, smart farming,

smart home, smart city, intelligent transportation,

etc.

IoT layers - Application Layer

IoT layers - Business Layer

� Business Layer:

� Maintain overall IoT system including the

applications and services.

� Build business models, graphs, flowcharts, etc.

based on the data received from Application layer.

� Analyzing and monitoring of models results, which

helps to determine the future actions and business

strategies.

IoT Application examples

� Manufacturing, logistics and retail

� Energy and utilities

� Intelligent transportation systems

� Environment monitoring systems

� Home management and monitoring

� Healthcare

� Smart Library Services

Roadmap of key technological developments with IoT

Source : Jayavardhana Gubbi

①Global addressing schemes such as IPv6

②Standardization for interoperability

③Low lower and thin batteries

④Cloud storage⑤Security in RFID and

cloud ⑥Smart sensors in

healthcare⑦Data centers⑧WSN test beds

①Smart antennas②Networking sensors ③Enhanced RFID

security and privacy ④Miniaturized readers ⑤Interoperability

between RFID and WSNs

⑥Cloud computation as a service

⑦Energy harvesting ⑧Intelligent analytics ⑨Wireless power ⑩RFID in retail 11Industrial ecosystems 12Low cost SCADA

system

①Energy harvesting and recycling

②Large scale wireless sensor networks

③Highly enhanced security

④Deploy and forget networks

⑤Self adaptive system of systems

⑥Cloud storage, computation and online analytics

⑦Biodegradable materials and nanopower units

⑧Critical infrastructure monitoring

⑨Smart grid and household metering

①Smart tags for logistics and vehicle management

②Vehicle to infrastructure

③System level analytics ④Autonomous vehicles

using IoT services ⑤Heterogeneous

systems with interaction between other sub-networks

⑥Smart traffic⑦Automatically driven

vehicles ⑧ intelligent

transportation and logistics

2010 2015 2020 2025 & +

Home and personal

Enterprise

Utility

Transport

Plug & play smart objects

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-RRegulation can stunt innovation, cause economic

disasters, and delay system rollout

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

� Protocols are standardized by IETF as RFCs