EE 359: Wireless CommunicationsProfessor Andrea Goldsmith

Outline

Course Basics Course Syllabus The Wireless Vision Technical Challenges Current Wireless Systems Spectrum Regulation and Standards Emerging Wireless Systems

Course Information*

People Instructor: Andrea Goldsmith,

andrea@ee, Packard 371, OHs: MW after class and by appt.

TAs: Mainak Chowdhury, mainakch@stanford.edu, and Milind Rao, milind@stanford.edu, Discussion Tues 4-5 pm (televised) or 5-6pmOHs: Tues after discussion (Mainak), Wed 5-

6pm, Thur 9:30-10:30 (Milind), location TBA. Email OHs (ideally via Piazza): Thursday 2-4

pm. Piazza website: https://piazza.com/stanford/fall2014/ee359/home

Class Administrator: Pat Oshiro, poshiro@stanford, Packard 365, 3-2681. Homework dropoff: Th by 5 pm.

*See web or handout for more details

Course InformationNuts and Bolts

Prerequisites: EE279 or equivalent (Digital Communications)

Required Textbook: Wireless Communications (by me), CUP Available at bookstore (out of stock) or Amazon Extra credit for finding typos/mistakes/suggestions

(2nd ed. soon!) Supplemental texts on 1 day reserve at Engineering

Library.

Class Homepage: www.stanford.edu/class/ee359 All handouts, announcements, homeworks, etc.

posted to website “Lectures” link continuously updates topics,

handouts, and reading

Class Mailing List: ee359-aut1415-students@lists (automatic for on-campus registered students). Guest list ee359-aut1415-guest@lists for SCPD and

auditors: send Mainak/Milind email to sign up. Sending mail to ee359-aut1415-staff@lists reaches

me and TAs.

Grading: Two Options No Project (3 units): HW – 30%, 2 Exams – 30%, 40% Project (4 units): HWs- 20%, Exams - 25%, 30%,

Project - 25%

HWs: assigned Thurs, due following Thurs 5pm (starts 9/25) Homeworks lose 33% credit per day late, lowest HW

dropped Up to 3 students can collaborate and turn in one HW

writeup Collaboration means all collaborators work out all

problems together Unpermitted collaboration or aid (e.g. solns for the

book or from prior years) is an honor code violation and will be dealt with strictly.

Exams: Midterm week of 11/3. (It will be scheduled outside

class time; the duration is 2 hours.) Final on 12/8 from 8:30-11:30 am.

Exams must be taken at scheduled time, unless a course conflicts

Course InformationPolicies

The term project (for students electing to do a project) is a research project related to any topic in wireless

Two people may collaborate if you convince me the sum of the parts is greater than each individually

A 1 page proposal is due 10/24 at 5 pm. 5-10 hours of work typical for proposal Project website must be created and proposal

posted there

The project is due by 5 pm on 12/6 (on website) 20-40 hours of work after proposal is typical for a

project

Suggested topics in project handout Anything related to wireless or application of

wireless techniques ok.

Course InformationProjects

Course Syllabus Overview of Wireless Communications Path Loss, Shadowing, and Fading

Models Capacity of Wireless Channels Digital Modulation and its

Performance Adaptive Modulation Diversity MIMO Systems Multicarrier Modulation Spread Spectrum Intro to Wireless Networks (EE360)

Lecture # Date Topic Required Reading    Introduction  

1 9/22 Overview of Wireless CommunicationsChapter 1 and Appendix D

Wireless Channel Models

2*-3 9/26*,9/29 Path Loss and Shadowing ModelsLec 2: Section 2.1 to 2.6Lec 3: Section 2.7 to 2.10

4-5 10/1,10/6Statistical Fading Models, Narrowband Fading

Lec 4: Section 3.1 to 3.2.1Lec 5: Section 3.1 to 3.2

6 10/8 Wideband Fading Models Section 3.2 to 3.3Impact of Fading and ISI on Wireless Performance

7 10/13 Capacity of Wireless Channels Chapter 4

8,9*,1010/15,10/22, 10/24*

Digital Modulation and its PerformanceLec 8: Chapter 5Lec 9-10: Chapter 6

Flat-Fading Countermeasures11 10/27 Diversity Chapter 712 10/29 Adaptive Modulation Section 9.1 to 9.2

 MT Week of 11/3 Midterm (outside class time) Chapters 2 to 7

 

13 11/3Practical Considerations in Adaptive Modulation

Section 9.3

14,15,16*11/5,11/10,

11/17Multiple Input/Output Systems (MIMO)

Chapter 10 & Appendix C

ISI Countermeasures17 11/19 Equalization, Multicarrier Systems Chapter 12.1-12.318 11/21* Multicarrier Modulation and OFDM Chapter 12.4-12.6

Multiuser Systems19 12/1 Spread Spectrum and CDMA Chapter 13

20 12/3Overview of multiuser systems & networksCourse summary

Sections 14.1 to 14.4, 15.1 to 15.2, 16.1 to 16.3

Final 12/8 8:30-11:30 am  

No lectures Wed 9/24, Mon 10/20, Wed 11/12

Class Rescheduling

9/24 (this Wed) moved to 9/26 (this Fri), 9:30-10:45, 102 Thornton (w/donuts)

10/20 (Mon) rescheduled to Fri 10/24, tentatively 9:30-10:45am, 102 Thornton (w/donuts)

11/12 (Wed) rescheduled to Fri 11/21, tentatively 9:30-10:45am, 102 Thornton (w/donuts)

May have optional advanced topics lecture the last week of classes (evening or lunch, w/ pizza)

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 ubiquitous Use in third world countries growing

rapidly Wifi also enjoying tremendous success

and growth Wide area networks (e.g. Wimax) and

short-range systems other than Bluetooth (e.g. UWB) less successful

Ancient Systems: Smoke Signals, Carrier Pigeons, …

Future Wireless Networks

Ubiquitous Communication Among People and Devices

Next-generation CellularWireless Internet AccessWireless MultimediaSensor Networks Smart Homes/SpacesAutomated HighwaysIn-Body NetworksAll this and more …

Challenges

Network ChallengesScarce/bifurcated spectrumDemanding/diverse applicationsHeterogeneous networksHigh-performance requirementsReliability and coverage

Device ChallengesSize, Power, CostMultiple Antennas in SiliconMultiradio Integration Coexistance

Cellular

AppsProcessor

BT

MediaProcessor

GPS

WLAN

Wimax

DVB-H

FM/XM

Software-Defined (SD) Radio:

Wideband antennas and A/Ds span BW of desired signals

DSP programmed to process desired signal: no specialized HW

Cellular

AppsProcessor

BT

MediaProcessor

GPS

WLAN

Wimax

DVB-H

FM/XM A/D

A/D

DSPA/D

A/D

Is this the solution to the device challenges?

Today, this is not cost, size, or power efficientCompressed sensing may be a solution for sparse

signals

Current Wireless Systems

Cellular Systems Wireless LANs WiGig and mmWave

Communications Cognitive Radios Satellite Systems Zigbee radios

Driving Constraint in Wireless System Design:

Scarce Spectrum

Licensed Bands Scarce & Expensive

$$$

Spectral ReuseDue to its scarcity, spectrum

is reused

BS

In licensed bands

Cellular

Wifi, BT, UWB,…

and unlicensed bands

Reuse introduces interference

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

(reuse 1 common now). Base stations/MTSOs coordinate handoff and control

functions Shrinking cell size increases capacity, as well as

networking burdenBASE

STATION

MTSO

Future Cellular Phones

Much better performance and reliability than today- Gbps rates, low latency, 99% coverage indoors and out

BSBS

PhoneSystem

BS

San Francisco

ParisNth-Gen

Cellular

Nth-Gen

Cellular

Internet

LTE backbone is the Internet

Everything wireless in one deviceBurden for this performance is on the backbone network

4G/LTE Cellular Much higher data rates than 3G

(50-100 Mbps)3G systems has 384 Kbps peak rates

Greater spectral efficiency (bits/s/Hz)More bandwidth, adaptive OFDM-

MIMO, reduced interferenceFlexible use of up to 100 MHz of

spectrum20 MHz spectrum allocation common

Low packet latency (<5ms).Reduced cost-per-bitAll IP network

Careful what you wish for…

20

Exponential Mobile Data

Growth

Leading to massive spectrum deficit

Growth in mobile data, massive spectrum deficit and stagnant revenues require technical and political breakthroughs for ongoing success of cellular

Source: Unstrung Pyramid Research 2010Source: FCC

On the Horizon: “The Internet of Things”

Number of Connected Objects Expected to Reach 50bn by 2020

Are we at the Shannon limit of the Physical Layer?

We don’t know the Shannon capacity of most wireless channels

Time-varying channels with no/imperfect CSI

Channels with interference or relaysCellular systems

Channels with delay/energy/HW constraints.

Ad-hoc/peer-to-peer networks

Channels and networks with feedback

Multicast/common information networks

Rethinking “Cells” in Cellular

Traditional cellular design “interference-limited”MIMO/multiuser detection can remove interferenceCooperating BSs form a MIMO array: what is a cell?Relays change cell shape and boundariesDistributed antennas move BS towards cell boundarySmall cells create a cell within a cellMobile cooperation via relays, virtual MIMO, network coding.

SmallCell

Relay

DAS

Coop MIMO

How should cellularsystems be designed?

Will gains in practice bebig or incremental; incapacity or coverage?

Are small cells the solution to increase cellular system capacity?

Yes, with reuse one and adaptive techniques (Alouini/Goldsmith 1999)

A=.25D2p Area Spectral Efficiency

S/I increases with reuse distance (increases link capacity).Tradeoff between reuse distance and link spectral

efficiency (bps/Hz).Area Spectral Efficiency: Ae=SRi/(.25D2p) bps/Hz/Km2.

The Future Cellular Network: Hierarchical Architecture

Future systems require Self-Organization (SON) and WiFi Offload

10x Lower COST/Mbps (?)

10x CAPACITY Improvement

Near 100%COVERAGE

MACRO: solving initial coverage issue, existing networkPICO: solving street, enterprise & home coverage/capacity issue

Macrocell Picocell Femtocell

Today’s architecture• 3M Macrocells serving 5 billion users• Anticipated 1M small cells per year

SON Premise and Architecture

Node Installation

Initial Measurements

Self Optimization

SelfHealing

Self Configurati

on

Measurement

SON Server

SoNServer

Macrocell BS

Mobile GatewayOr Cloud

Small cell BS

X2

X2X2

X2

IP Network

SWAgent

SON is part of 3GPP/LTE standard Small cells not widely deployed today

Green” Cellular Networks

Minimize energy at both the mobile and base station via New Infrastuctures: cell size, BS placement,

DAS, Picos, relays New Protocols: Cell Zooming, Coop MIMO,

RRM, Scheduling, Sleeping, Relaying Low-Power (Green) Radios: Radio

Architectures, Modulation, coding, MIMO

Pico/Femto

Relay

DAS

Coop MIMO

How should cellularsystems be redesignedfor minimum energy?

Research indicates thatsignificant savings is possible

Wifi NetworksMultimedia Everywhere, Without Wires

802.11ac

Wireless HDTVand Gaming

• Streaming video• Gbps data rates• High reliability• Coverage inside and out

Wifi is today’s small cell

Wireless Local Area Networks (WLANs)

WLANs connect “local” computers (100m range)

Breaks data into packets Channel access shared (random access

+ backoff) Backbone Internet provides best-effort

servicePoor performance in some apps (e.g.

video)

01011011

InternetAccessPoint

0101 1011

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 band (300 MHz)/also 2.4GHz OFDM in 20 MHz with adaptive rate/codes Speeds of 54 Mbps, approx. 100-200 ft range

802.11n/ac (Current) Standard in 2.4 GHz and 5 GHz band Adaptive OFDM /MIMO in 20/40/80/160 MHz Antennas: 2-4, up to 8 Speeds up to 600Mbps/10 Gbps, approx. 200 ft

range Other advances in packetization, antenna use,

multiuser MIMO

Many WLAN cards have

(a/b/g/n)

The WiFi standard lacks good mechanisms to mitigate interference, especially in dense AP deployments Multiple access protocol (CSMA/CD) from 1970s Static channel assignment, power levels, and carrier

sensing thresholds In such deployments WiFi systems exhibit poor spectrum

reuse and significant contention among APs and clients Result is low throughput and a poor user experience

Why does WiFi performance suck?

Carrier Sense Multiple Access: if another WiFi signal detected, random backoff

Collision Detection: if collisiondetected, resend

Why not use SoN for WiFi?

SoN-for-WiFi: dynamic self-organization network software to manage of WiFi APs.

Allows for capacity/coverage/interference mitigation tradeoffs.

Also provides network analytics and planning.

SoNController

- Channel Selection- Power Control- etc.

In fact, why not use SoN for all wireless networks?

TV White Space &Cognitive Radio

mmWave networks Vehicle networks

Software-Defined Wireless Network

(SDWN) Architecture

WiFi Cellular mmWave Cognitive Radio

Freq.Allocation

PowerContr

ol

SelfHealing

ICIC QoSOpt.

CSThreshol

d

UNIFIED CONTROL PLANE

HW Layer

SW layer

App layerVideo SecurityVehicularNetworks HealthM2M

WiGig and mmWaveWiGig

Standard operating in 60 GHz bandData rates of 7-25 GbpsBandwidth of around 10 GHz

(unregulated)Range of around 10m (can be extended)Uses/extends 802.11 MAC LayerApplications include PC peripherals and

displays for HDTVs, monitors & projectors

mmWaveCouples 60GHz with massive MIMO and

better MACPromises long-range communication

w/Gbps data ratesHardware, propagation and system design

challengesMuch research on this topic today

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 went bankrupt

Global Positioning System (GPS) ubiquitousSatellite signals used to pinpoint locationPopular in cell phones, PDAs, and

navigation devices

IEEE 802.15.4/ZigBee Radios

Low-Rate WPAN Data rates of 20, 40, 250 Kbps Support for large mesh networking

or star clusters Support for low latency devices CSMA-CA channel access Very low power consumption Frequency of operation in ISM bandsFocus is primarily on low power sensor networks

Spectrum Regulation Spectrum a scarce public resource,

hence allocated 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 in multiple cognitive radio paradigms

Standards Interacting systems require

standardization

Companies want their systems adopted as standardAlternatively try for de-facto

standards

Standards determined by TIA/CTIA in USIEEE standards often adoptedProcess fraught with inefficiencies

and conflicts

Worldwide standards determined by ITU-TIn Europe, ETSI is equivalent of

IEEE

Standards for current systems are summarized in Appendix D.

Emerging Systems*

Cognitive radio networksAd hoc/mesh wireless networksSensor networksDistributed control networksThe smart gridBiomedical networks

*Can have a bonus lecture on this topic late in the quarter if there is interest

Cognitive Radios

Cognitive radios support new users in existing crowded spectrum without degrading licensed usersUtilize advanced communication and DSP

techniquesCoupled with novel spectrum allocation policies

Multiple paradigms(MIMO) Underlay (interference below a threshold)Interweave finds/uses unused time/freq/space slotsOverlay (overhears/relays primary message while

cancelling interference it causes to cognitive receiver)

NCR

IP

NCRCR CR

CRRx

NCRRxNCRTx

CRTx

MIMO Cognitive Underlay Cognitive Overlay

Compressed Sensing in Communications

Compressed sensing ideas have found widespread application in signal processing and other areas

Basic premise: exploit sparsity to approximate high-dimensional system/signal in a few dimensions.

We ask: how can sparsity be exploited to reduce the complexity of communication system design

• Sparse signals: e.g. white-space detection

• Sparse state space: e.g reduced-dimension network control

• Sparse users: e.g. reduced-dimension multiuser detection

• Sparse samples: e.g. sub-Nyquist sampling

Ad-Hoc Networks

Peer-to-peer communicationsNo backbone infrastructure or

centralized control Routing can be multihop. Topology is dynamic. Fully connected with different link

SINRs Open questions

Fundamental capacity regionResource allocation (power, rate,

spectrum, etc.) Routing

Wireless Sensor NetworksData Collection and Distributed Control

Energy (transmit and processing) is the driving constraint

Data flows to centralized location (joint compression) Low per-node rates but tens to thousands of nodes Intelligence is in the network rather than in the

devices

• Smart homes/buildings• Smart structures• Search and rescue• Homeland security• Event detection• Battlefield surveillance

Distributed Control over Wireless

Interdisciplinary design approach

• Control requires fast, accurate, and reliable feedback.

• Wireless networks introduce delay and loss

• Need reliable networks and robust controllers

• Mostly open problems

Automated Vehicles - Cars - Airplanes/UAVs - Insect flyers

: Many design challenges

The Smart Grid:Fusion of Sensing, Control, Communications

carbonmetrics.eu

Open problems:- Optimize sensor placement in the grid- New designs for energy routing and distribution- Develop control strategies to robustify the grid- Look at electric cars for storage and path planning

Applications in Health, Biomedicine and

Neuroscience

Recovery fromNerve Damage

Doctor-on-a-chip

WirelessNetwork

Neuro/Bioscience- EKG signal

reception/modeling- Brain information theory- Nerve network

(re)configuration- Implants to

monitor/generate signals- In-brain sensor networks- SP/Comm applied to

bioscience

Body-Area Networks

Main Points

The wireless vision encompasses many exciting systems and applications

Technical challenges transcend across all layers of the system design.

Existing and emerging systems provide excellent quality for certain applications but poor interoperability.

Innovative wireless design needed for mmWave systems, massive MIMO, SDWN, and Internet of Things connectivity

Standards and spectral allocation heavily impact the evolution of wireless technology