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Transcript of ECEN5553 Telecom Systems Dr. George Scheets Week #12 Read [27] "Fantastic 4G" [28] "Mobiles...
ECEN5553 Telecom SystemsDr. George ScheetsWeek #12Read [27] "Fantastic 4G"[28] "Mobiles Millimeter Wave Makeover"[29] "Emerging Technologies and Research Challenges for
5G Wireless Networks""Term Paper
6 November (Live)< 13 November (Distant Learning)Late Fee = -1 point per working day
Final ExamFriday, 11 December, 1400 – 1550 (Live)< 18 December (Distance Learning)
Exam 2 Results – 90 points (as of 5:00 pm 3 November)Hi = 87.7, Low = 59.3, Average = 78.43, σ = 8.39A > 81, B > 70, C > 61
ECEN5553 Telecom SystemsDr. George ScheetsWeek #12Read [27] "Fantastic 4G"[28] "Mobiles Millimeter Wave Makeover"[29] "Emerging Technologies and Research Challenges for
5G Wireless Networks""Term Paper
6 November (Live)< 13 November (Distant Learning)Late Fee = -1 point per working day
Final ExamFriday, 11 December, 1400 – 1550 (Live)< 18 December (Distance Learning)
Exam 2 Results – 90 points (as of 5:00 pm 3 November)Hi = 87.7, Low = 59.3, Average = 78.43, σ = 8.39A > 81, B > 70, C > 61
Cosine & Cosine2Cosine & Cosine2
Cosine
Cosine2
Cosine & Cosine*SineCosine & Cosine*Sine
Cosine
Sine
Cosine*Sine
RF Wireless Layer 1 IssuesRF Wireless Layer 1 Issues Message mapped onto carrier waveMessage mapped onto carrier wave
Binary: PSKBinary: PSK 4-Ary: 4-PSK, a.k.a. QPSK4-Ary: 4-PSK, a.k.a. QPSK M-Ary: QAM (combo of ASK & PSK)M-Ary: QAM (combo of ASK & PSK)
Hi frequency RF carrier Hi frequency RF carrier Small antennaSmall antenna
Hi frequency RF carrierHi frequency RF carrier Less penetrationLess penetration
Wireless is a Hostile EnvironmentWireless is a Hostile Environment Compared to Guided Media (fiber, copper cable)Compared to Guided Media (fiber, copper cable) Noisier & received power is very weakNoisier & received power is very weak
Forward Error CorrectionForward Error Correction XMTR Adds extra parity bits to the bit streamXMTR Adds extra parity bits to the bit stream FEC codes allow trade-off of an increase in the bit rate for a reduced RCVR Message Bit Error RateFEC codes allow trade-off of an increase in the bit rate for a reduced RCVR Message Bit Error Rate
Cranking up transmitted signal power can do the sameCranking up transmitted signal power can do the same Distance between legal code words sets error correcting capability Distance between legal code words sets error correcting capability FEC codes are used on...FEC codes are used on...
Cell PhonesCell Phones NASA Deep Space probesNASA Deep Space probes Compact DiskCompact Disk ...and other applications....and other applications.
Digital Communication SystemDigital Communication System
SourceData, Digitized audio or video.Outputs bits.
FECAdds extra parity bits.
ChannelAttenuates,
distorts,& adds noise to symbols.
ModulatorConverts bitsto a symbol suitable for
channel.
Symbol DetectorExamines
received symbol& outputs 1
(binary) or more(M-Ary) bits.
FEC DecoderExamines blocks
of bits. If possible, corrects or
detects bit errors.Outputs estimate ofsource bit stream.
Optional
ModulatorModulator Copper CableCopper Cable
Electrical pulses frequently used Electrical pulses frequently used Fiber CableFiber Cable
Electrical pulses converted to optical pulsesElectrical pulses converted to optical pulses RF SystemsRF Systems
High frequency sinusoid symbols usedHigh frequency sinusoid symbols used Carrier frequency impacts antenna sizeCarrier frequency impacts antenna size
Binary versus M-Ary Binary versus M-Ary M-Ary packs more bits in the bandwidthM-Ary packs more bits in the bandwidth M-Ary more susceptible to decoding errorsM-Ary more susceptible to decoding errors M-Ary used when bandwidth is tight & SNR decentM-Ary used when bandwidth is tight & SNR decent
RF ModulatorRF Modulator
May map 1 Mbps stream from the FEC coder to...May map 1 Mbps stream from the FEC coder to... ... 1 M symbol/sec Binary ... 1 M symbol/sec Binary ASK,ASK, PSK PSK, or FSK , or FSK
signalsignal ... 500 K symbol/sec 4-Ary ... 500 K symbol/sec 4-Ary ASK,ASK, PSK (a.k.a. PSK (a.k.a.
QPSK)QPSK), or FSK signal, or FSK signal 2 bits per symbol2 bits per symbol Would require less Bandwidth than Binary as BW Would require less Bandwidth than Binary as BW
proportional to symbol rateproportional to symbol rate ... other M-Ary signal (QAM)... other M-Ary signal (QAM)
Receiver Symbol DetectorReceiver Symbol Detector If Radio systemIf Radio system
INPUT: attenuated, noisy & distorted INPUT: attenuated, noisy & distorted Binary PSK, QPSK, or QAM Binary PSK, QPSK, or QAM
If copper cableIf copper cable INPUT: attenuated, noisy & distorted square electrical pulses INPUT: attenuated, noisy & distorted square electrical pulses
(Baseband)(Baseband) If fiberIf fiber
INPUT: attenuated, noisy, & distorted square optical pulses INPUT: attenuated, noisy, & distorted square optical pulses (Baseband)(Baseband)
OUTPUT: Baseband (square electrical pulses)OUTPUT: Baseband (square electrical pulses)
ReceiverReceiver
FEC DecoderFEC Decoder INPUT: Baseband BitsINPUT: Baseband Bits
Traffic we want + parity bitsTraffic we want + parity bits OUTPUT: Baseband BitsOUTPUT: Baseband Bits
Traffic bitsTraffic bits Some may be in error Some may be in error
FEC ExamplesFEC Examples Single Sample Detector (SSD)Single Sample Detector (SSD)
Samples each symbol once, compares result to thresholdSamples each symbol once, compares result to threshold Matched Filter Detector (MFD)Matched Filter Detector (MFD)
Samples each bit multiple times and computes an Samples each bit multiple times and computes an average, compares average to a thresholdaverage, compares average to a threshold
MFD will have lower P(BE) than SSDMFD will have lower P(BE) than SSD MFD P(BE) gets worse as bit rate increasesMFD P(BE) gets worse as bit rate increases
Averaging time becomes shorterAveraging time becomes shorter Number of independent samples gets smallerNumber of independent samples gets smaller
FEC ExamplesFEC Examples In the limit, as bit interval T approaches zero In the limit, as bit interval T approaches zero
secondsseconds # 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) = 0.1 for SSD for all bit ratesP(BE) = 0.1 for SSD for all bit rates 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)
Block Diagram:Single Sample Detector & no FECBlock Diagram:Single Sample Detector & no FEC
Source
Channel
Channel Coder
Symbol Detector:Single Sample
P(Bit Error) = .1R bps
If symbol detector screws up 10% ofIf symbol detector screws up 10% of
the time, P(Bit Application Error) = 0.1the time, P(Bit Application Error) = 0.1
Data bitsR bps
Example: Source OutputExample: Source Output 500 Kbps Data Bit Stream500 Kbps Data Bit Stream
Layer 2 protocols and aboveLayer 2 protocols and above Voice, Computer Data, or Video Voice, Computer Data, or Video
time
+1
volts
0
-1
T
T = .000002 seconds/bit1/T = 500 K Data bps.
Example: 2:1 FEC Coder OutputExample: 2:1 FEC Coder Output Might duplicate each application bit Might duplicate each application bit
for every 1 for every 1 data data bit input, two code bits bit input, two code bits (1 parity bit & the input application bit) are output(1 parity bit & the input application bit) are output
time
+1
volts
0
-1
T
T = .000001 seconds/bit1/T = 1 M Code bps.
Example) SSD 2 bit code wordsExample) SSD 2 bit code words Suppose you now transmit each bit twice, and Suppose you now transmit each bit twice, and
P(Code Bit Error) = .1 P(Code Bit Error) = .1 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 decoded in error)00, 11 (appears legal, 0 or 2 bits decoded in error)01, 10 (clearly illegal, 1 bit decoded in error)01, 10 (clearly illegal, 1 bit decoded in error)P(No bits in error) = .9*.9 = .81P(No bits in error) = .9*.9 = .81P(One bit in error) = 2*.9*.1 = .18P(One bit in error) = 2*.9*.1 = .18P(Both bits in error) = .1*.1 = .01P(Both bits in error) = .1*.1 = .01
Decoder takes 2 Code bits at a time & outputs 1 bit of DataDecoder takes 2 Code bits at a time & outputs 1 bit of DataIf illegal code word received, it can guess 0 or 1.If illegal code word received, it can guess 0 or 1.81%81% + + 18%(1/2)18%(1/2) = 90% of time the correct bit is output = 90% of time the correct bit is output 1%1% + + 18%(1/2)18%(1/2) = 10% of time the incorrect bit is output = 10% of time the incorrect bit is output
Same performance as No Coding @ twice the bit rateSame performance as No Coding @ twice the bit rate
SSD 2:1 FECSSD 2:1 FEC
SourceFEC Coder:Input = 1 bit.
Output = Input + Parity
bit.
Channel
Modulator
Symbol Detector:
Single sample
FEC Decoder:Looks at blocks of
2 bits. Outputs1 bit.
data bits
R bps
codebits
2R bps
code bitsapp. bits
P(code bit error) = .1P(data bit error) = .1
Symbol ratetransmitted
must double compared to noFEC case, or
4-Ary signaling must be used.
Example) SSD 3 bit code wordsExample) SSD 3 bit code words Transmit each bit thrice, P(Code Bit Error) = .1Transmit each bit thrice, P(Code Bit Error) = .1
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 bits in error)001, 010, 100 (clearly illegal, 1 or 2 bits in error)011, 101, 110 (clearly illegal, 1 or 2 bits in error)011, 101, 110 (clearly illegal, 1 or 2 bits in error)P(No bits in error) = .9*.9*.9 = .729P(No bits in error) = .9*.9*.9 = .729P(One bit in error) = 3*.9P(One bit in error) = 3*.922*.1 = .243*.1 = .243P(Two bits in error) = 3*.9*.1P(Two bits in error) = 3*.9*.122 = .027 = .027 P(Three bits in error) = .1*.1*.1 = .001P(Three bits in error) = .1*.1*.1 = .001
Decoder takes 3 bits at a time & outputs 1 bit. Majority Rules.Decoder takes 3 bits at a time & outputs 1 bit. Majority Rules.72.9%72.9% + 24.3% = 97.2% of time correct bit is output + 24.3% = 97.2% of time correct bit is output .1%.1% + + 2.7%2.7% = 2.8% of time incorrect bit is output = 2.8% of time incorrect bit is output
Improved performance @ 3x the required bit rateImproved performance @ 3x the required bit rate
SSD 3:1 FECSSD 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.
data bits
R bps
codebits
3R bps
data bits
P(data bit error) = .028
Symbol Detector:
Single sample
code bits
P(code bit error) = .1
Symbol ratetransmittedmust triple
compared to noFEC case, or
8-Ary signaling must be used.
3:1 FEC offers superior performance than simpler no FEC code system.
Example) MFD No CodingExample) MFD No Coding Probability of a Bit Error will improve over that of Probability of a Bit Error will improve over that of
Single Sample Detector to, say, P(Bit Error) = .02Single Sample Detector to, say, P(Bit Error) = .02 No Coding: Transmit each Data Bit OnceNo Coding: Transmit each Data Bit Once
Legal Transmitted data‘words’; 0, 1Legal Transmitted data‘words’; 0, 1 Possible received data wordsPossible received data words
0, 1 (legal or 1 bit in error, no way to tell)0, 1 (legal or 1 bit in error, no way to tell)P(Data Bit OK) = .98P(Data Bit OK) = .98P(Data Bit in error) = .02P(Data Bit in error) = .02
Matched Filter Detector & No coding: Block Diagram
Matched Filter Detector & No coding: Block Diagram
Source
Channel
Channel Coder
Symbol Detector:Matched Filter
P(Bit Error) = .02
Matched Filter shows reduced bit errors compared to SSDMatched Filter shows reduced bit errors compared to SSD Improvement decreases as symbol rate increasesImprovement decreases as symbol rate increases
Example) MFD 2 bit code wordsExample) MFD 2 bit code words Suppose you transmit each bit twice, smaller bit width will cause P(Code Suppose you transmit each bit twice, smaller bit width will cause P(Code
Bit Error) to increase to, say 0.03 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
Typical FEC PerformanceTypical FEC Performance
SNR
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 2:1 FECMFD 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.
Rdata bps
2Rcodebps
2R code bpsR
app. bps
P(code bit error) = .03P(data bit error) = .03
Example) MFD 3 bit code wordsExample) MFD 3 bit code words Transmit each bit thrice, P(Bit Error) again increases to, say 0.04, due to further Transmit each bit thrice, P(Bit Error) again increases to, say 0.04, due to further
increase in the bit rate. 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 FECMFD 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.
P(app. bit error) = .005
Symbol Detector:Matched
Filter
P(code bit error) = .04
Rapplication
bps
3Rcodebps
3R code bpsR
app. bps
Typical FEC PerformanceTypical FEC Performance
Received SNR
P(BE) Coded
Uncoded
FEC allows targetP(BE) to be reachedwith lower receivedSNR, but a higher bit rate must be
transmitted. Used a lot in power limited
environments.
Different FEC codes will have different curves!
Very Large Array ParabolicsVery Large Array Parabolics
image source: Wikipedia
Directional antennas. Larger size → narrower beam.Narrower beam → energy more focused (XMTR)
Narrower beam → better at picking up weak signal (RCVR)
Arecibo Radio Telescope (305 m)Arecibo Radio Telescope (305 m)Direct TV Antenna (1/2 m)
Omni-Directional Antenna ArrayOmni-Directional Antenna Array
source:http://www.pcmag.com/article2/0,1759,1822020,00.asp
Belkin Wireless Pre-N Router F5D8230-4
Steerable beams.
Two Omni Array ExampleTwo Omni Array Example
fc = 300 MHzλ = 1 meter
Same signal fedto both antennas.
Beam shoots outboth sides at 90degree angle.(Far side not shown.)
λ/2
Directivity Strength
Two Omni Array ExampleTwo Omni Array Example
fc = 300 MHzλ = 1 meter
Signal to rightantenna delayedby 333.3 picosecond( = 10% wavelength)with respect to rightantenna.
λ/2
Directivity Strength
Two Omni Array ExampleTwo Omni Array Example
fc = 300 MHzλ = 1 meter
Signal to leftantenna delayedby 333.3 picosecond( = 10% wavelength)with respect to rightantenna.
λ/2
Directivity Strength
Two Omni Array ExampleTwo Omni Array Example
fc = 300 MHzλ = 1 meter
Signal to leftantenna delayedby 833.3 picosecond( = 25% wavelength)with respect to rightantenna.
λ/2
Directivity Strength
Two Omni Array ExampleTwo Omni Array Example
fc = 300 MHzλ = 1 meter
Signal to leftantenna delayedby 1 2/3 nanosecond( = 50% wavelength)with respect to rightantenna.
λ/2
Directivity Strength
I/O LAN Antenna CombinationsI/O LAN Antenna Combinations SISOSISO
Common TodayCommon Today SIMO, MISO, & MIMOSIMO, MISO, & MIMO
Starting to see use on wireless LAN's & MAN'sStarting to see use on wireless LAN's & MAN's SIMO & MISOSIMO & MISO
Can help cancel effects of multi-pathCan help cancel effects of multi-path MIMOMIMO
Can provide Can provide spatial diversityspatial diversity Increases amount of usable RF bandwidthIncreases amount of usable RF bandwidth
Satcom & Flat Panel Antenna ArraysSatcom & Flat Panel Antenna Arrays
USS Lake Champlain: Aegis Guided Missile Cruiserimage source: wikipedia
Bit Error Rate Unsatisfactory?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
Crank up transmitter power outCrank up transmitter power out Use directional antennasUse directional antennas
Use more effective modulation techniqueUse more effective modulation technique Slow down the transmitted symbol rateSlow down the transmitted symbol rate Use less noisy receiver electronicsUse less noisy receiver electronics
Voyager II Deep Space ProbeVoyager II Deep Space Probe Used all of previous techniques on downlink:Used all of previous techniques on downlink:
2:1 FEC Coding (different code than in previous examples)2:1 FEC Coding (different code than in previous examples) Increasingly sophisticated earth receive antennasIncreasingly sophisticated earth receive antennas Binary PSK signalingBinary PSK signaling Reduced bit rates Reduced bit rates Cryogenically cooled receiver electronicsCryogenically cooled receiver electronics
Flight historyFlight history LaunchLaunch , August 1977 , August 1977 Jupiter fly-by, July 1979, Message bit rate: 115.2 KbpsJupiter fly-by, July 1979, Message bit rate: 115.2 Kbps Saturn fly-by, August 1981, Message bit rate: 44 KbpsSaturn fly-by, August 1981, Message bit rate: 44 Kbps Uranus fly-by, Uranus fly-by, January 1986, Message bit rate: 29.9 KbpsJanuary 1986, Message bit rate: 29.9 Kbps Neptune fly-by, August 1989, Message bit rate: 21.6 KbpsNeptune fly-by, August 1989, Message bit rate: 21.6 Kbps Now well past Pluto. NASA is still in contact.Now well past Pluto. NASA is still in contact.
Pre-Cellular Mobile Telephony Pre-Cellular Mobile Telephony
source: Telecommunications by Warren Hioki, 1st Edition
0th Generation Mobile Phones0th Generation Mobile Phones
Source: http://www.wb6nvh.com/MTSfiles/Carphone1.htm
Cellular Telephone SystemCellular Telephone Systemso
urc
e: T
elec
omm
un
icat
ion
s by
War
ren
Hio
ki, 1
st E
diti
on
ISP
Cellular Telephony Advantages:Cellular Telephony Advantages: Frequency Reuse Reduced Transmitter Power Out Reduced Multipath Problems Reduced brain damage? Subdividing Cells increases System
Capacity More Reliable due to cell overlap
Cellular Telephony Disadvantages:Cellular Telephony Disadvantages:
More complexMore complex More installation hasslesMore installation hassles
BS to MTSO link (Backhaul) & switching BS to MTSO link (Backhaul) & switching requirements can get out of hand requirements can get out of hand
1987 Mobile Phone1987 Mobile Phone
source: September 1987Electronic Design Magazine
One Big CellOne Big Cell
30 Channelscould support
30 users
Seven Smaller CellsSeven Smaller Cells
Set #310 Channels
Set #110 Channels
Set #210 ChannelsCan
Support70 Userswith sameChannelset.
Mobile TrafficMobile Traffic
Source: "The Great Spectrum Famine", IEEE Spectrum Magazine, October 2010.
London, 1995London, 1995
Hidden Cell TowersHidden Cell Towers
sources: businessweek.commobilitydigest.com