ECEN5533 Modern Commo Theory Dr. George Scheets Lesson #23 12 November 2013

ECEN5533 Modern Commo TheoryDr. George ScheetsLesson #25 11 November 2014

Read Section 6.4 – 6.5Read Section 6.4 – 6.5 Problems: 9.2, 9.4, 9.7, 6.2, 6.3Problems: 9.2, 9.4, 9.7, 6.2, 6.3 Design #2 due 11 NovemberDesign #2 due 11 November Reworked Exam #2 due 18 NovemberReworked Exam #2 due 18 November

ECEN5533 Modern Commo TheoryDr. George ScheetsLesson #26 13 November 2014

Read Section 6.6 – 6.9, 7.1Read Section 6.6 – 6.9, 7.1 Problems: 5.8, 6.4 & 5, 9.8 & 9Problems: 5.8, 6.4 & 5, 9.8 & 9 Reworked Exam #2 due 18 NovemberReworked Exam #2 due 18 November Final Exam, 0800 – 0950, Tuesday, 8 DecemberFinal Exam, 0800 – 0950, Tuesday, 8 December

ECEN5533 Modern Commo TheoryDr. George ScheetsLesson #27 18 November 2014 Read Section 7.2 - 7.3Read Section 7.2 - 7.3 Problems: 6.9, 6.11, 6.13, 7.1Problems: 6.9, 6.11, 6.13, 7.1 Reworked Exam #2 due todayReworked Exam #2 due today Reworked Design #2 due 25 NovemberReworked Design #2 due 25 November Final Exam, 0800 – 0950, Tuesday, 9 DecemberFinal Exam, 0800 – 0950, Tuesday, 9 December

ECEN5533 Modern Commo TheoryDr. George ScheetsLesson #28 20 November 2014 Read Section 7.4 Read Section 7.4 Problems 7.3, 7, 10, & 12Problems 7.3, 7, 10, & 12 Reworked Design #2 due 25 NovemberReworked Design #2 due 25 November Late Fee -1 per working dayLate Fee -1 per working day Final Exam, 0800 – 0950, Tuesday, 8 DecemberFinal Exam, 0800 – 0950, Tuesday, 8 December

ECEN5533 Modern Commo TheoryDr. George ScheetsLesson #29 25 November 2014 Read Section 12.1Read Section 12.1 Problems 7.16, 12.3 & 12.4Problems 7.16, 12.3 & 12.4 Reworked Design #2 due todayReworked Design #2 due today Comprehensive Final Exam (No Rework)Comprehensive Final Exam (No Rework)

Tuesday, 9 December, 0800-0950Tuesday, 9 December, 0800-0950

ECEN5533 Modern Commo TheoryDr. George ScheetsLesson #30 2 December 2014

Problems 12.9, 10, 11, & 21Problems 12.9, 10, 11, & 21 Comprehensive Final Exam (No Rework)Comprehensive Final Exam (No Rework)


ECEN5533 Modern Commo TheoryDr. George ScheetsLesson #31 4 December 2014

Radar Set & Old FinalsRadar Set & Old Finals Comprehensive Final Exam (No Rework)Comprehensive Final Exam (No Rework)


Design #2: Digital Satellite RFP Lowest Working BidLowest Working Bid

$20.54 Million$20.54 Million Matt GaalswyckMatt Gaalswyck Promoted to Senior Engineer II at MegaMoronPromoted to Senior Engineer II at MegaMoron

ASK @ 2.2 GHz ASK @ 2.2 GHz 84-1 Compression, (2.54,1) FEC84-1 Compression, (2.54,1) FEC Tower at city centerTower at city center

G1 = 2.493 over 285 degreesG1 = 2.493 over 285 degrees G2 = 1.116 over 75 degrees, aimed due NG2 = 1.116 over 75 degrees, aimed due N

1,000,000 receiver antenna elements1,000,000 receiver antenna elements 36.13 dB margin36.13 dB margin Largest Cost: Geek Telecom @ $7.75 MLargest Cost: Geek Telecom @ $7.75 M

Point Spreads of Completed Stuff Quiz #1 (20 points)Quiz #1 (20 points)

Hi = 19.1, Low = 9.7, Ave = 13.45, Hi = 19.1, Low = 9.7, Ave = 13.45, σσ = 3.20 = 3.20 Quiz #2 (20 points)*Quiz #2 (20 points)*

Hi = 15.9, Low = 10.6, Ave = 13.52, Hi = 15.9, Low = 10.6, Ave = 13.52, σσ = 2.38 = 2.38 Exam #1 (100 points)*Exam #1 (100 points)*

Hi = 86, Low = 46, Ave = 65.83, Hi = 86, Low = 46, Ave = 65.83, σσ = 17.23 = 17.23A A >> 85, B 85, B >> 69, C 69, C >> 59, D 59, D >> 49 49

Exam #2 (100 points)*Exam #2 (100 points)*Hi = 97, Low = 31, Ave = 70.33, Hi = 97, Low = 31, Ave = 70.33, σσ = 24.33 = 24.33A A >> 90, B 90, B >> 78, C 78, C >> 68, D 68, D >> 58 58

Design #1 (70 points)Design #1 (70 points)Hi = 66, Low = 59, Ave = 65.80, Hi = 66, Low = 59, Ave = 65.80, σσ = 3.39 = 3.39

Anything in Circles is Fair Gameon Final Exam

S

Read HW

Notes

Bit Error Rate Unsatisfactory? System designer has several options:System designer has several options:

Use FEC codesUse FEC codes Increase received signal powerIncrease received signal power Use more effective modulation techniqueUse more effective modulation technique

Best for baseband: + & - square pulsesBest for baseband: + & - square pulses Best for RFBest for RF

Binary system? PSKBinary system? PSKM-Ary system? QPSK or QAMM-Ary system? QPSK or QAM

Slow down the transmitted message symbol rateSlow down the transmitted message symbol rate Decrease receiver TDecrease receiver Tsystemsystem

FEC Examples Matched Filter Detector (MFD)Matched Filter Detector (MFD) MFD P(BE) gets worse as bit rate increasesMFD P(BE) gets worse as bit rate increases

h(t) = 1; 0 h(t) = 1; 0 << t t << T, for an integrator T, for an integrator H(f) = sinc with a phase shiftH(f) = sinc with a phase shift Integration time becomes shorterIntegration time becomes shorter H(f) becomes wider, less of a low pass filterH(f) becomes wider, less of a low pass filter

FEC Examples In the limit, as bit interval T approaches zeroIn the limit, as bit interval T approaches zero

# of independent samples approaches 1 # of independent samples approaches 1 MFD P(BE) approaches SSD P(BE)MFD P(BE) approaches SSD P(BE)

Suppose you have a system whereSuppose you have a system where P(BE) = 0.02 for MFD at bit rate R (no FEC)P(BE) = 0.02 for MFD at bit rate R (no FEC) P(BE) = 0.03 for MFD at bit rate 2R (2:1 FEC)P(BE) = 0.03 for MFD at bit rate 2R (2:1 FEC) P(BE) = 0.04 for MFD at bit rate 3R (3:1 FEC)P(BE) = 0.04 for MFD at bit rate 3R (3:1 FEC)

Matched Filter Detector & No coding: Block Diagram

Source

Channel

Channel Coder

Symbol Detector:Matched Filter

P(Data Bit Error) = .02

MFD 2:1 FEC

SourceSource Coder:Input = 1 bit.

Output = Input + Parity

bit.

Channel

Channel Coder

Symbol Detector:Matched

Filter

Source Decoder:Looks at blocks of

2 bits. Outputs1 bit.

Rapplication

bps

2Rcodebps

2R code bpsR

app. bps

P(code bit error) = .03

Example) MFD 2 bit code words Suppose you transmit each bit twice, smaller bit width will cause Suppose you transmit each bit twice, smaller bit width will cause

P(Code Bit Error) to increase to, say 0.03 P(Code Bit Error) to increase to, say 0.03 Legal Transmitted code words; 00, 11Legal Transmitted code words; 00, 11 Possible received code wordsPossible received code words

00, 11 (appears legal, 0 or 2 bits in error)00, 11 (appears legal, 0 or 2 bits in error)01, 10 (clearly illegal, 1 bit in error)01, 10 (clearly illegal, 1 bit in error)P(No code bits in error) = .97*.97 = .9409P(No code bits in error) = .97*.97 = .9409P(One code bit in error) = 2*.97*.03 = .0582P(One code bit in error) = 2*.97*.03 = .0582P(Both code bits in error) = .03*.03 = .0009P(Both code bits in error) = .03*.03 = .0009

Decoder takes 2 code bits at a time and outputs 1 data bitDecoder takes 2 code bits at a time and outputs 1 data bitIf illegal code word received, it can guess 0 or 1.If illegal code word received, it can guess 0 or 1.94.09%94.09% + + 5.82%(1/2)5.82%(1/2) = 97% of time correct bit output = 97% of time correct bit output .09%.09% + + 5.82%(1/2)5.82%(1/2) = 3% of time the incorrect bit is output = 3% of time the incorrect bit is output

FEC makes it worse: 3% data bit error vs 2% No CodingFEC makes it worse: 3% data bit error vs 2% No Coding

MFD 2:1 FEC


Output = Input + Parity

bit.

Channel

Channel Coder


Filter



Rapplication

bps

2Rcodebps

2R code bpsR

app. bps

P(code bit error) = .03P(data bit error) = .03P(Data Bit Error) = .02 when FEC not used.

Typical FEC Performance

Eb/No

P(BE)

Coded Plot changes as type of symbol, type of detector, and type of FEC coder change.

UncodedPlot changes as type of symbol, andtype of detector change.Last example is

operating here.

There generally always is a cross-over point.The max possible P(BE) = 1/2.

MFD 3:1 FEC


Output = Input + twoparity bits.

Channel

Channel Coder




FilterP(code bit error) = .04

Rapplication

bps

3Rcodebps

3R code bpsR

app. bps

Example) MFD 3 bit code words Transmit each bit thrice, P(Bit Error) again increases to, say 0.04, due to Transmit each bit thrice, P(Bit Error) again increases to, say 0.04, due to

further increase in the bit rate. further increase in the bit rate. Legal Transmitted code words; 000, 111Legal Transmitted code words; 000, 111 Possible received code wordsPossible received code words

000, 111 (appears legal, 0 or 3 bits in error)000, 111 (appears legal, 0 or 3 bits in error)001, 010, 100 (clearly illegal, 1 or 2 code bits in error)001, 010, 100 (clearly illegal, 1 or 2 code bits in error)011, 101, 110 (clearly illegal, 1 or 2 code bits in error)011, 101, 110 (clearly illegal, 1 or 2 code bits in error)P(No code bits in error) = .96*.96*.96 = .884736P(No code bits in error) = .96*.96*.96 = .884736P(One code bit in error) = 3*.96P(One code bit in error) = 3*.9622*.04 = .110592*.04 = .110592P(Two code bits in error) = 3*.96*.04P(Two code bits in error) = 3*.96*.0422 = .004608 = .004608 P(Three code bits in error) = .04*.04*.04 = .000064P(Three code bits in error) = .04*.04*.04 = .000064

Decoder takes 3 bits at a time & outputs 1 bit. Majority Rules.Decoder takes 3 bits at a time & outputs 1 bit. Majority Rules.88.4736%88.4736% + 11.0592% = 99.5328% of time correct bit is output + 11.0592% = 99.5328% of time correct bit is output .0064%.0064% + + .4608%.4608% = 0.4672% of time incorrect bit is output = 0.4672% of time incorrect bit is output

FEC makes Data BER better (.5% vs 2%) @ thrice the bit rateFEC makes Data BER better (.5% vs 2%) @ thrice the bit rate

MFD 3:1 FEC


Output = Input + twoparity bits.

Channel

Channel Coder




FilterP(code bit error) = .04

Rapplication

bps

3Rcodebps

3R code bpsR

app. bps

P(data bit error) = .005P(Data Bit Error) = .02 when FEC not used.

Rate 1/2 Turbo Coder

uukk (data) & v (data) & vkk (parity bits) are transmitted to far side (parity bits) are transmitted to far side vvkk = v = v1k1k 1/2 of the time & v 1/2 of the time & v2k2k other half other half

Source: Figure 8.26 from Sklar's Digital Communications

Rate 1/2 Turbo Decoder

xxkk (corrupted data) & y (corrupted data) & ykk (corrupted parity bits) (corrupted parity bits) yykk = y = y1k1k 1/2 of the time & y 1/2 of the time & y2k2k other half other half


←Matched

Filter

←Matched

Filter

Rate 1/2 Turbo Coding Performance

P(data bit error) = 0.00001 P(data bit error) = 0.00001 when Eb/when Eb/NoNo = 0.2 dB & 18 = 0.2 dB & 18 repsreps

P(bit error) = 0.07395 for P(bit error) = 0.07395 for BPSK when Eb/BPSK when Eb/NoNo = 0.2 dB = 0.2 dB


Performance Uncoded BPSKUncoded BPSK Hard coded Block or Convolutional BPSKHard coded Block or Convolutional BPSK Soft coded Convolutional BPSKSoft coded Convolutional BPSK

2 dB increase in effective Eb/No 2 dB increase in effective Eb/No Compared to Hard Convolutional DecodingCompared to Hard Convolutional Decoding

Turbo Coded BPSKTurbo Coded BPSK Big time increase in effective Eb/Big time increase in effective Eb/NoNo Can get you close to Shannon LimitCan get you close to Shannon Limit

All of above require an increase in the bit rateAll of above require an increase in the bit rate Need more bandwidth, or go M-AryNeed more bandwidth, or go M-Ary

Trellis Coded ModulationTrellis Coded Modulation 3 db – 6 dB increase in effective Eb/3 db – 6 dB increase in effective Eb/NoNo Doesn't require an increase in bit rateDoesn't require an increase in bit rate

Improved Performance

Low Density Parity Check Codes Developed by Robert Gallagher, 1963 MIT GradDeveloped by Robert Gallagher, 1963 MIT Grad

Low Density → Few 1's in rows & columns of Low Density → Few 1's in rows & columns of HH Impractical to implement thenImpractical to implement then

Linear Block CodesLinear Block Codes Huge block sizesHuge block sizes DVB-S2 (Video) Code DVB-S2 (Video) Code

43,200 data bits & 21,600 parity bits43,200 data bits & 21,600 parity bits Offers comparable performance to Turbo CodesOffers comparable performance to Turbo Codes

Being used in some of the newest standardsBeing used in some of the newest standards 10 Gbps Ethernet over twisted pair10 Gbps Ethernet over twisted pair 802.11n & 802.11ac (optional)802.11n & 802.11ac (optional)

Turbo Codes: Easy to Encode, Hard to DecodeTurbo Codes: Easy to Encode, Hard to DecodeLDPC Codes: Hard to Encode, Easy to DecodeLDPC Codes: Hard to Encode, Easy to Decode

Spread Spectrum Two KindsTwo Kinds

Direct SequenceDirect Sequence Frequency HoppingFrequency Hopping

AdvantagesAdvantages Interference SuppressionInterference Suppression Low Probability of ExploitationLow Probability of Exploitation Multipath Effects are ReducedMultipath Effects are Reduced Code Division Multiple AccessCode Division Multiple Access

UsesUses 3G Cell Phone Standards3G Cell Phone Standards Lower to mid speed WiFi (IEEE 802.11)Lower to mid speed WiFi (IEEE 802.11)

+1

-1time

time

time+1

-1-1-1

+1 +1 +1

Traffic(9 Kbps)

SpreadingSignal27 Kcps

TransmittedSignal27 Kcps

+1 +1+1

-1 -1

DSSS - Transmit Side

Wireless

X

27 KcpsSquare Pulses

cos(2πfct)

BPSK output27 Kcps90% of power in 54 KHz BW

centered at fc Hertz

X

cos(2πfct)

BPSK input27 Kcps+ noise

27 KcpsSquare Pulses+ filtered noise

RCVR Front End

RF Transmitter

Low PassFilter

time

time+1

-1-1-1

+1 +1 +1DespreadingSignal27 Kcps

ReceivedSignal27 Kcps

+1 +1+1

-1 -1

+1

-1

timeRecoveredTraffic9 Kbps

DSSS-Receiver

DSSS Receiver

If the proper source is transmitting...If the proper source is transmitting... ...and the receiver has the correct ...and the receiver has the correct

despread sequence...despread sequence... ...and the sequence is properly ...and the sequence is properly

synchronized...synchronized... ...the original message is recovered....the original message is recovered.

DSSS Receiver

If another source is transmitting...If another source is transmitting...

...the receiver will have the wrong ...the receiver will have the wrong despread sequence...despread sequence...

...and the output will be garbage....and the output will be garbage.

time+1ReceivedSignal #227 Kcps

+1

-1

timeRecoveredGarbage from 2ndsignal -1

+1 +1

+1 +1

-1

time

-1-1

+1 +1 +1DespreadingSignal27 Kcps

+1 +1

+1

-1

DSSS-Receiver

RecoveredGarbage at 2ndreceiver

ReceiverMatchedFilterDetector

Message Output is a random sequence of 0’s & 1’s

+1 +1

time

time

-1

+1 +1+1 +1

-1

DSSS Receiver

If both sources are transmitting...If both sources are transmitting...

...the bit detector will be fed the sum of ...the bit detector will be fed the sum of the results.the results.

Input toMatchedFilterDetector(sum)

+1

-1

timeRecoveredTraffic9 Kbps

timeRecoveredGarbage from 2ndsignal -1

+1 +1

+2

+1

-1

+1

-2

time

DSSS-Receiver

+2

ReceiverMatchedFilterDetectorOutput

Additional signals transmitting at the same time increase the apparent noise seen by our system.

Message BER will increase.

+1

-1 time

Input toMatchedFilterDetector(sum)

+2

-2

time

TBit

+2

FDM FDMAWDM frequency

time

Different channels use some of the bandwidth all of the time.

1 2 3 4 5

TDMTDMA

frequency

time

Different channels use all of the bandwidth some of the time. Predictable time assignments.

1

2

3

1etc.

CDMAfrequency

time

Different channels use all of the bandwidth all of the time.

Channels use different codes. Other channels cause noise-like interference.

CDMA: 3D View

code #1

code #2

code #3

frequency

time

CDMA vs FDMA

Example) Given 10 MHz Channel & Example) Given 10 MHz Channel & Coding Gain of 1,000Coding Gain of 1,000 CDMA will support 75 usersCDMA will support 75 users FDMA will support 900 usersFDMA will support 900 users All things being equal...All things being equal...

Power Out, Path Loss, Antenna Gains, etc.Power Out, Path Loss, Antenna Gains, etc. In real world, all things aren't always In real world, all things aren't always

equalequal

CDMA vs FDMA (or TDMA) Narrowband NoiseNarrowband Noise

May knock out some FDMA or TDMA channelsMay knock out some FDMA or TDMA channels Severe Multi-path EnvironmentSevere Multi-path Environment

May knock out some FDMA channelsMay knock out some FDMA channels Easier to add usersEasier to add users

Transmit with different code (CDMA)Transmit with different code (CDMA) Must find empty time slot or frequency bandMust find empty time slot or frequency band

Easier to use Variable Rate CoderEasier to use Variable Rate Coder Voice Coder with Silence SuppressionVoice Coder with Silence Suppression

Doubles potential capacityDoubles potential capacity

DSSS Wireless Example

X

100 KcpsZero MeanSquare Pulses

cos(2πfct)

BPSK output100 Kcps90% of power in 200 KHz BW

centered at fc Hertz

X

cos(2πfct)

BPSK input100 Kcps+ noise+ 2nd DSSS Signal 100 Kcps

Zero MeanSquare Pulses+ filtered noise

RCVR Front End

RF Transmitter

Low PassFilter

(Wide Band)

Band PassFilter

(Wide Band)

Spread Spectrum Receiver

X

cos(2πfct)

BPSK input100 Kcps+ noise+ 2nd DSSS Signal

100 KcpsZero MeanSquare Pulses+ filtered noise+ 2nd DSSS signal

RCVR Front End

Low PassFilter

(Wide Band)

Band PassFilter

(Wide Band)

XDespreadSequence

Low PassFilter

(Narrow Band)

10 KbpsMessage+ noise+ 2nd DSSSinterference(noise like)

Radar

XMTR

RCVR

Switch

Antenna

Same antenna normally used.Either Transmitter or Receiver connected at any time.

F-15 Eagle

RCS ≈ Barn Door?

F-117 Nighthawk

RCS ≈ Hummingbird = 0.025 m2?

B-2 Spirit

RCS ≈ 0.1 m2?

Impulse Response

Non-stealthvs

Stealth

Source: Cheville & Grischkowsky,"Time Domain THz Impulse Response Studies", Applied Physics Letters, October 1995

Impulse Response

LookingDownfrom

Top LeftSource: Cheville & Grischkowsky,"Time Domain THz Impulse Response Studies", Applied Physics Letters, October 1995

Voyager IIhttp://voyager.jpl.nasa.gov/index.html LaunchLaunch

August 1977 August 1977 Jupiter fly-byJupiter fly-by

July 1979July 1979 Saturn fly-bySaturn fly-by

August 1981August 1981 Uranus fly-byUranus fly-by

January 1986January 1986 Neptune fly-byNeptune fly-by

August 1989August 1989 15.93 Billion Km15.93 Billion Km

106.5 AU106.5 AU November 2014November 2014

Source: JPL

source: http://voyager.jpl.nasa.gov/

VoyagerSpacecraft

source:September 1990IEEE CommunicationsMagazine

NASA Deep Space Network70 m diameter parabolic

source:http://deepspace.jpl.nasa.gov

Voyager FEC Coding

source: Science, Summer 1990

BER Performance

at Jupiter

source: Science, Summer 1990CODING

NO CODE

Target BER:Imaging 5(10-3)Non-Imaging: 5(10-5)Command: 1(10-5)

BER Performance

at Saturn


CODINGSame SystemConfigurationas at Jupiter


CODINGSlowed bitrate comparedto Jupiter

BER Performance

at Uranus



CODINGReduced RIncreased AerDecreased Tsyscompared to Saturn

CODINGSame SystemConfigurationas at Saturn

Signal * Wideband Noise

BER Performance

at Neptune



CODINGReduced RIncreased Aer Rebuilt antennas Additional coupling

CODINGSame SystemConfigurationas at Uranus

NRAO's Very Large Array

image source: http://www.vla.nrao.edu/

MIMO Used in latest Cell & Wireless LAN protocolsUsed in latest Cell & Wireless LAN protocols

WiFi 802.11n & 802.11acWiFi 802.11n & 802.11ac LTE 4G CellularLTE 4G Cellular

Potential BenefitsPotential Benefits Steerable BeamsSteerable Beams

Increased antenna gainIncreased antenna gain Spatial MultiplexingSpatial Multiplexing

Transmit several signals over (ideally) independent pathsTransmit several signals over (ideally) independent paths Increase usable BWIncrease usable BW

Spatial DiversitySpatial Diversity Several Versions of XMTR signal receivedSeveral Versions of XMTR signal received Improves BERImproves BER

MIMO antenna

source:http://www.pcmag.com/article2/0,1759,1822020,00.asp

Belkin Wireless Pre-N Router F5D8230-4

MIMO Examplefc = 300 MHzλ = 1 meter

Same signal fedto both antennas.

Beam shoots outboth sides at 90degree angle.

λ/2

Directivity Strength


Signal to leftantenna advancedby 333.3 picosecond( = 10% wavelength)with respect to rightantenna.

λ/2



Signal to leftantenna delayedby 333.3 picosecond( = 10% wavelength)with respect to rightantenna.

λ/2



Signal to leftantenna delayedby 833.3 picosecond( = 25% wavelength)with respect to rightantenna.

λ/2



Signal to leftantenna delayedby 1 2/3 nanosecond( = 50% wavelength)with respect to rightantenna.

λ/2


Directivity: .4λ spacing

source: www.orbanmicrowave.com/The_Basics_of_Antenna_Arrays.pdf

# elementsred = 2green = 5blue = 10

Directivity: 5 elements

source: www.orbanmicrowave.com/The_Basics_of_Antenna_Arrays.pdf

spacingred = .2λgreen = .3λblue = .5λ

SISO Potential BenefitsPotential Benefits

Can use Steerable BeamsCan use Steerable Beams Increased antenna gainIncreased antenna gain


Spatial MultiplexingSpatial Multiplexing Transmit several signals over independent pathsTransmit several signals over independent paths Increase usable BWIncrease usable BW

MISO Potential BenefitsPotential Benefits

Transmitter can use Steerable BeamsTransmitter can use Steerable Beams Increased antenna gainIncreased antenna gain


Spatial MultiplexingSpatial Multiplexing Transmit several signals over independent pathsTransmit several signals over independent paths Only one signal per Single Antenna (SO) ReceiverOnly one signal per Single Antenna (SO) Receiver Increase usable BWIncrease usable BW

Needed for Spatial Multiplexing: Accurate Knowledge of RF channelAccurate Knowledge of RF channel Can get by…Can get by…

Periodically transmit known sequencesPeriodically transmit known sequences x1(t) = string of logic 1'sx1(t) = string of logic 1's x2(t) = alternating 1's and 0'sx2(t) = alternating 1's and 0's

Look at relative strength at two outputsLook at relative strength at two outputs Baseband x1(t) = constant valueBaseband x1(t) = constant value Baseband x2(t) = peak-to-peak valueBaseband x2(t) = peak-to-peak value

SIMO Potential BenefitsPotential Benefits

Receiver can use Steerable BeamsReceiver can use Steerable Beams Increased antenna gainIncreased antenna gain

Spatial DiversitySpatial Diversity Several Versions of Several Versions of samesame XMTR signal received XMTR signal received Feed signal with strongest power to MFD & FECFeed signal with strongest power to MFD & FEC Improves BERImproves BER

Spatial MultiplexingSpatial Multiplexing Receive several signals over multiple pathsReceive several signals over multiple paths Increase usable BWIncrease usable BW

MFDetector

Power = ?

Power = ?

switch

Wish to Probe Further?

See… See… Multiple Antenna Techniques for Multiple Antenna Techniques for Wireless CommunicationsWireless Communications

What Will 5G Be?What Will 5G Be?

(Links on 5533 Home Page)(Links on 5533 Home Page)

OFDM Resistant to narrow band interferenceResistant to narrow band interference

Which might knock out single carrier systemWhich might knock out single carrier system Resistant to multi-pathResistant to multi-path Spread Spectrum has same benefitsSpread Spectrum has same benefits

Requires extra BW compared to OFDMRequires extra BW compared to OFDM Usually implemented with FFT & IFFTUsually implemented with FFT & IFFT Used in latest Wireless ProtocolsUsed in latest Wireless Protocols

WiFi 802.11n & 802.11acWiFi 802.11n & 802.11ac LTE 4G CellularLTE 4G Cellular

Standard Single Carrier Modulationfrequency

time

Message power is multiplied by a carrier with a single center freq.

M-ASK, M-PSK, M-QAM

Channel 1

Example:8 Mbps bit stream carried by B-PSK with 16 MHz null-to-null BW

Orthogonal FDMfrequency

time

Channels split into sub-channelsBits parceled out to sub-channels

Advantage:Sub-channel bit rates can be modified to cope with interferenceLess susceptible to multipath

Channel 1

FDM with Multi-path

XMTR

RCVRdirect path

bounce path

direct path pulsesbounce path pulses

Signal sum seen by Receiver

T1 T2 T3 Symbol decision intervals at Receiver.The third bit is obliterated by multi-path.

T3time

delay

OFDM with Multi-path

direct

T3

bounce

directbounce

directbounce

T2T1

Matched filter detector will work OK.

delay

Slower symbol rate over each subchannel.

ECEN5533 Modern Commo Theory Dr. George Scheets Lesson #23 12 November 2013

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Transcript of ECEN5533 Modern Commo Theory Dr. George Scheets Lesson #23 12 November 2013