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