ecen5533 modern commo theory dr. george scheets lesson #23 12 november 2013
DESCRIPTION
ECEN5533 Modern Commo Theory Dr. George Scheets Lesson #23 12 November 2013. Read Section 6.4 – 6.5 Problems: 9.2, 9.4, 9.7, 6.2, 6.3 Reworked Quiz #2 due various dates Reworked Exam #2 due various dates Exam # 2 < 14 Nov (remote DL) Design #2, 14 Nov (local), < 21 Nov (remote DL). - PowerPoint PPT PresentationTRANSCRIPT
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)
Tuesday, 9 December, 0800-0950Tuesday, 9 December, 0800-0950
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)
Tuesday, 9 December, 0800-0950Tuesday, 9 December, 0800-0950
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
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) = .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
SourceSource Coder:Input = 1 bit.
Output = Input + twoparity bits.
Channel
Channel Coder
Source Decoder:Looks at blocks of
3 bits. Outputs1 bit.
Symbol Detector:Matched
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
SourceSource Coder:Input = 1 bit.
Output = Input + twoparity bits.
Channel
Channel Coder
Source Decoder:Looks at blocks of
3 bits. Outputs1 bit.
Symbol Detector:Matched
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
Source: Figure 8.27 from Sklar's Digital Communications
←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
Source: Figure 8.28 from Sklar's Digital Communications
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
source: Science, Summer 1990
CODINGSame SystemConfigurationas at Jupiter
Target BER:Imaging 5(10-3)Non-Imaging: 5(10-5)Command: 1(10-5)
CODINGSlowed bitrate comparedto Jupiter
BER Performance
at Uranus
source: Science, Summer 1990
Target BER:Imaging 5(10-3)Non-Imaging: 5(10-5)Command: 1(10-5)
CODINGReduced RIncreased AerDecreased Tsyscompared to Saturn
CODINGSame SystemConfigurationas at Saturn
Signal * Wideband Noise
BER Performance
at Neptune
source: Science, Summer 1990
Target BER:Imaging 5(10-3)Non-Imaging: 5(10-5)Command: 1(10-5)
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
MIMO Examplefc = 300 MHzλ = 1 meter
Signal to leftantenna advancedby 333.3 picosecond( = 10% wavelength)with respect to rightantenna.
λ/2
Directivity Strength
MIMO Examplefc = 300 MHzλ = 1 meter
Signal to leftantenna delayedby 333.3 picosecond( = 10% wavelength)with respect to rightantenna.
λ/2
Directivity Strength
MIMO Examplefc = 300 MHzλ = 1 meter
Signal to leftantenna delayedby 833.3 picosecond( = 25% wavelength)with respect to rightantenna.
λ/2
Directivity Strength
MIMO Examplefc = 300 MHzλ = 1 meter
Signal to leftantenna delayedby 1 2/3 nanosecond( = 50% wavelength)with respect to rightantenna.
λ/2
Directivity Strength
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 DiversitySpatial Diversity Several Versions of XMTR signal receivedSeveral Versions of XMTR signal received Improves BERImproves BER
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 DiversitySpatial Diversity Several Versions of XMTR signal receivedSeveral Versions of XMTR signal received Improves BERImproves BER
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.