digital communications ecp 601 2020. 9. 2. · wcdma. communication principles evolving paths...

Digital Communications

ECP 601

1

Professional Masters Program

Acknowledgement

These lecture notes were mainly prepared by

Dr. Ahmed Hesham, EECE, Cairo University

2

Introduction

3

Introduction

Advances of Telecommunications

4

Introduction

The Big Picture (What we want)

5©RFMD

Introduction


6

Voice ApplicationsTele-Health

Tele-EducationTele-Transactions, etc.

Home/Office/Vehicular Networking

Mobile MultimediaApplications

Social Network

Tele-work (business/Government

/individual)

Global Network Objectives

Introduction

7


The evolution of telecommunications

Introduction


8

More sophisticated applications(Internet of Things)

Introduction

The Big Picture (What we need)

▪ Understand the existing technologies

▪ General descriptions and rate advantages

▪ Understand what fields/science enable these technologies?

▪ Theoretical limits and practical implementations

9

Introduction

10

1G

2G2.5G

3G

4G

Analog

14 kbps400 kbps

14 Mbps

100 Mbps

1 GbpsLTE

LTEA

1980 1990 2000 2010/2020 Time

Data Rate

Speed Vs. Time

1/2/3/4 G: are officially defined as wireless standards by the International TelecommunicationUnion (ITU)

2.5/2.75/3.5 G…: labeled only for marketing purposes

~

Introduction

11

GSM GPRS EDGE UMTS HSDPA HSUPA LTE LTEA

IS95 1xRTTEVDORev0

UMBEVDORev A

EVDORev B

20002001

20022003

20042005

20062007

20082009

20102011

20122013

2014

802.11 802.11b802.11g802.11a

802.11aa 802.11n

DL: 9.6 KUL: 9.6 K

DL: 60 KUL: 40 K

DL:177 KUL:188 K

DL:384 KUL:384 K

DL: 1.8-7.2 MUL: 384 K

DL: 7.2 MUL: 5.8 M

DL: 100 MUL: 50 M

DL: 1 GUL: 500 M

DL: 14.4 KUL: 14.4 K

DL: 153 KUL: 153 K

DL: 2.4 MUL: 153 K

DL: 3.1 MUL: 1.8 M

DL: 3.1-73 MUL: 1.8-27 M

DL: 70-200 MUL: 30-45 M

DL: 2 MUL: 2 M

DL: 11 MUL: 11 M

DL: 54 MUL: 54 M

DL: 200 MUL: 200 M

DL: < 1 GUL: < 1G

A closer Look

CDMAOne CDMA2000

WCDMA

Communication Principles

Evolving Paths (different classification)

12

1G 2G 3G 4G2.5G

© Dong Xuan at Ohio State University

Each of these standards has underlying technologies.


Evolving Paths (different classification)

13

1G 2G 3G 4G2.5G

© Dong Xuan at Ohio State University

Each of these standards has underlying technologies.

Fuzzy words:TDMA/FDMA/CDMA/SDMA/

OFDMA…


• Can we do more (rates)?

• We must understand the system capabilities (theoretical and practical limits)

14

GSM GPRS EDGE UMTS HSDPA HSUPA LTE LTEA

DL: 9.6 KUL: 9.6 K

DL: 60 KUL: 40 K

DL:177 KUL:188 K

DL:384 KUL:384 K

DL: 1.8-7.2 MUL: 384 K

DL: 7.2 MUL: 5.8 M

DL: 100 MUL: 50 M

DL: 1 GUL: 500 M

B4G

?


• Let us visit some of the basic concepts and terminologies

• More details will be covered throughout the course

15

DVB-T/T2


• The channel:

– The medium over which the information is transported

DVB-S

WiFi/BT/ZigBee/NFC

Cellular

16


• The channel:

– What are the channel parameters (characteristics)?

– How to measure a channel?

– How to model the channel (application-dependent)?

– How to communicate over the channel (the ultimate goal)?

17


• The channel:

– Capacity ≈ “Maximum information rate transported over a channel”

– The definition is not really rigorous

18


• The channel:

– Capacity ≈ “Maximum information rate transported over a channel”

– The definition is not really rigorousThat is too

much! I can’t get it all !!

How would I know?

19


• The channel:

– Capacity: “Maximum information rate that can be reliably transported over a channel”

That is too much! I can’t

get it all !!

How would I know?

20


• The channel:

– Capacity: “Maximum information rate that can be reliably transported over a channel”

That is too much! I can’t

get it all !!

How would I know?

21


• The Channel Capacity (theoretical limit):

– Assume a single-input single-output (SISO) system

– Shannon (1948) showed that the channel capacity of this system (under certain constraints) is

𝐶 = log2 1 +ℎ 2𝑃

𝑁𝑜

ℎ 2 : the (magnitude square of) channel response

𝑃 : the transmitted power

𝑁𝑜: the noise power

b/s/Hz

22

You can’t beat this number


23

• The channel:– Characteristics:

• Path-loss (two-ray model/Fresnel zone/ space attenuation, etc.)

• Small-scale fading (medium scatters)

• Large-scale fading (shadowing)

– Models (important for system design) :• Indoor/Outdoor

• Urban/Suburban

• LOS/NLOS

• Macro/Micro

.

.


• The channel is not the only important part

• Recall

• The transmitter/receiver should be also ‘smart’enough for ‘good’ communication

Transmitter ReceiverChannel

24


• The channel is not the only important part

• Recall

• The transmitter/receiver should be also ‘smart’enough for ‘good’ communication

Transmitter ReceiverChannel

25

But this will take for ever!

One drop at a timeis enough

Reliable scheme But not ‘smart’ enough

for ‘good’ communication


• These high rates are achieved over the same wireless channels! (in contrast to other wired applications (example!) )

– The evolution must be in the transceiver

– What could be the key enabling features?• Coding (add redundancy to detect and/or correct errors)

• Modulation (packs bits into symbols, thus sends more bits)

• OFDM/MIMO/Carrier Aggregation/Relay/Advanced Receivers…(many other techniques to combat the channel effects and send more data)

• Evolution of semiconductors and RF chips

• Evolution of higher layer protocols (MAC and network layers)26

GSM GPRS EDGE UMTS HSDPA HSUPA LTE LTEADL: 9.6 KUL: 9.6 K

DL: 60 KUL: 40 K

DL:177 KUL:188 K

DL:384 KUL:384 K

DL: 1.8-7.2 MUL: 384 K

DL: 7.2 MUL: 5.8 M

DL: 100 MUL: 50 M

DL: 1 GUL: 500 M

B4G?


• Revisiting some of the main communication principles

• Error control:

– Channel coding is very important

– One of the main tools to approach capacity!

– Examples: turbo, LDPC, Reed Solomon, etc.27


• Error control:

– Error detection (e.g. ARQ schemes)

– Error correction (FEC schemes)

ChannelEncoder

Channel

ChannelDecoder

ErrorDetector

RXTX

To TX

28


• Error control:

– Examples for FEC in Standards

29

Standards Channel Coding

LTE Turbo Code

UMTS Turbo Code

GSM Cyclic and Convolutional Code

CDMA Orthogonal Variable Spreading Factor (OVSF) code

IEEE 802.11a/g Convolutional Code

ZigBee 32-chip PN sequence


• Revisiting some of the main communication principles

• Modulation

– The process of varying some parameter of a periodic waveform in order to convey a message

– Digital Vs. Analog modulation

– Why moving to ‘Digital’?

30


• Modulation

– ‘Digital’ advantages : noise immunity, H/W complexity, power/bandwidth/security/performance constraints

– Equally important, the industry trends provide strong motivation

© Agilent application note 31


• Modulation

32


• Modulation

© Agilent application note

Theoretical Limits Actual implementation33


• Modulation (more on this, later)

– What are the different types of digital modulation?

– What is the (necessary) order of the modulation?

– What are the (I/Q) components of the modulation?

– What type of impairments (practical limitations) can exist for different modulations?

– How can we fix the impairments (pre-/post-compensation) ?

34


• Simplified system block diagram:

• Additional functions (required in practical system):– Scramblers/Interleaving/Precoding/IFFT/ CP/ZP/Pre-

compensations, etc. at the TX

– Descrambler/Deinterleaver/Equalizer/Ch.estimator/ Synchronization circuits, etc. at the RX

– RF chain!

ChannelEncoder

DigitalModulator

ChannelDigital

DemodulatorChannelDecoder

bits bits Signal

35

• Advanced techniques

– OFDM

– MIMO

– Equalizers

– Channel estimation

– Powerful decoders

– Synchronization techniques


36

OFDMMIMO

MIMO Ch Estimation and Equalization

.

.

• The final design could be complicated

• How is it implemented?


37

US 7724833

• Architecture Design

– Now that the system is designed, an architecture (hardware/software processing) must be chosen

– Two general types of processor:

• General purpose processor

• Application specific processor

– An application specific system can be built using:

• GPP (General Purpose Processor)

• ASIC (Application Specific Integrated Circuit)

• ASIP (Application Specific Instruction set Processor)


38

• Architecture Design

– Choosing the right architecture is important (criteria: time-to-market, performance, price, development, power, feature flexibility, etc.)

– Whatever you do has to fit in the chip (constraints), otherwise you will ‘fall out of’ it (Joseph Mitola)


No more space! I’m

falling out of the chip.

39

• Architecture Design– Example-1: ZigBee RX baseband processor on ASIC

– An example of a not-so-good design: Duplicating the design with 10M gates! This may indicate that some optimizations have not been considered (System/RTL).


Kai-Hsin Chen; Hsi-Pin Ma, "A low power ZigBee baseband processor," SoC Design Conference, 2008.

40

• Technology Advances (Nano Science)


42

• Good for Telecomm too (Why?)

Year : 04 06 08 10 12 14 16 18 20

𝐿𝐺 (nm) : 90 65 45 32 22 14 10 7 5

Gate Length


• The RF story

Switch

Power Amplifier Radio

Transceiver

Baseband Processor

© SIGE SEMICONDUCTOR INC

43


• The RF story

• The radio has three major parts

© AnandTech

44


• The RF story

• To support multi-bands, there are three main components: an antenna switch, per-band filter and PA.

Stacked radio architectureswith separate radio transceiversfor different standards

45© AnandTech


• The RF story• Recently, Qualcomm fabricated a CMOS-based

integrated PA and antenna switch in a single piece of silicon. This simplifies routing, reduces the number of RF components inthe front end, and reduces the PCB area. Big achievement! (why?)

46© AnandTech

• The RF story

– RF teams continue to develop new solutions

– Note that the RF section is not isolated from baseband processing. It has many impacts:• Operating band, power, noise/interf. immunity

• Received signal quality (sensitivity, RSSI, chain dynamics e.g. AGC dynamics, etc.)

• ADC/DAC characteristics

• Pre/Post-compensations

– Both teams MUST cooperate


… and here are mine

Here are my specs

RF Baseband47

• Back to our simplified system block diagram:

• Note that in general two quantities exist:

– Bit

– Signal


ChannelEncoder

DigitalModulator

bits bits Signal

RF Chain

48



• Note that in general two quantities exist:

– Bit

– Signal (in digital baseband domain, why? Details of IF/Baseband processing are provided later)

First level of abstractionin the system model

Bit-chainSignal-chain

(Digital)RF chain

interface interface

49

bits



• We can further abstract these procedures in one more step: Physical layer (PHY)

• What are the functions performed by the PHY layer (at the TX /RX) in a communication system?


(Digital)RF chain

50

PHYbits



• Where do the bits come from, how are they packed, and what do they really represent?


(Digital)RF chainPHYbits

51



• Medium Access Control (MAC):– Multiplexing and de-multiplexing information to/from

PHY

– Prepare payloads for PHY (padding if necessary)

– Can perform some functions (e.g. HARQ)

– handling frames to/from upper layer, etc.

MAC PHY

52



DSP algorithmsQualcommBroadcomSamsungRIMTIInterdigitalNSNAlcatel-Lucent

Semiconductors / ToolsIntel SynopsysSamsung CadenceQualcomm Mentor Graphics

Broadcom ZukenToshiba Agilent EEsofTIFreescaleSK Hynix

RFMotorola Ericsson Nexius

AxxceleraDelfMEMSOberonMaguffin

53

MAC/NetworkCiscoAlcatel-LucentEricssonIntelSamsungHPRealTek

Different parts of the chain require different specialties

MACUpper Layers

Base-band

RF

Some of these companies have smaller teams that specialize in other fields as well



DSP algorithmsQualcommBroadcomSamsungRIMTIInterdigitalNSNAlcatel-Lucent

Semiconductors / ToolsIntel SynopsysSamsung CadenceQualcomm Mentor Graphics

Broadcom ZukenToshiba Agilent EEsofTIFreescaleSK Hynix

RFMotorola Ericsson Nexius

AxxceleraDelfMEMSOberonMaguffin

54

MAC/NetworkCiscoAlcatel-LucentEricssonIntelSamsungHPRealTek

Different parts of the chain require different specialties

MACUpper Layers

Base-band

RF

Some of these companies have smaller teams that specialize in other fields as well

AntennasMobile MarkSkyCrossEMS TechLaird TechGaltronicsHuaweiNetgear



56

MACUpper Layers

Base-band

RF

Pt-to-Pt Applications

Pt-to-mPt Applications



57

MACUpper Layers

Base-band

RF

Outdoor AntennaIndoor Antenna



59

MACUpper Layers

Base-band

RF

Another part of the story:Antenna Array

Southern Hemisphere Auroral Radar Experiment (1988)Samsung AAS for FD-MIMO (2013/2014)



60

MACUpper Layers

Base-band

RF

More antennas → More rates !

Another part of the story:Antenna Array

‘Antenna’ is important for Telecomm.

Antenna is important for many other reasons (why)



62

MACUpper Layers

Base-band

RF

?


BTS: Base Transceiver Station

BSC: Base Station Controller

MSC: Mobile Switching Center

NOC: Network Operations Center

How does a packet travel through a network?

GSS: gateway switching system

PDN: Packet Data Network

PSTN: Public Switched Telephone Network


• Communication rules or procedures must be defined (Protocol)

• How do the protocols work?– A piece of data travels over a network in a number

of steps

– At each step, some actions are taken on the data

– In a network, several rules (protocols) work together (coordinated) to ensure proper data transfer

– This protocol coordination is done via layering

64


• Protocol Stack

– A protocol stack is a combination

of protocols (grouped in layers)

– Each layer of the stack has a

different protocol for handling

a function of the communication

process

65

Physical Layer

Data Link Layer

Network Layer

Transport Layer

Session Layer

Presentation Layer

ApplicationLayer

Open Systems Interconnection model


• Protocol Stack– Ex.: Protocols allow successful communication

between the chips of different manufacturers

66

Physical Layer

Data Link Layer

Network Layer

Transport Layer

Session Layer

Presentation Layer

ApplicationLayer


IntelNIC

HuaweiNIC

I speak Chinese你好

I speak English

Network

Packet flow


• Protocol Stack

67

Physical Layer

Data Link Layer

Network Layer

Transport Layer

Session Layer

Presentation Layer

ApplicationLayer


Indicates/accepts a request

Formatting/Display/Encryption

Traffic flow info (when the packetis sent)

Error-handling info

Address info

Error check and medium access

Prepare for sending the packet as bit stream


• Protocol Stack

– More details about these layers (later)

• Specific functions?

• Who specifies these functions?

• How are the interconnections defined?

• How to implement these functions?

• How to test a chip compliance?

68

Physical Layer

Data Link Layer

Network Layer

Transport Layer

Session Layer

Presentation Layer

ApplicationLayer


• A final product is obtained by integrating different teams works (in different layers)

• Collaboration between these teams is essential

• This results in many meetings, debates and work procedures (examples!)

Conclusion

69RF

DSP Alg.(System)

MAC

RTL

Upper Layers

Conclusion

• Course Roadmap

Digital Comm.Basics

Intro. to Current Technologies and Channel

Models

Implementation Methodologies

Advanced techniques

In Digital Comm.

Technical level

More

Less

70End of Lecture-1

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digital communications ecp 601 2020. 9. 2. · wcdma. communication principles evolving paths...

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