ECEN5553 Telecom SystemsWeek #9[19a] "IT Helps Passengers, Crew Navigate Gigantic Oasis of

the Seas Cruise Ship"[19b] "Open source IP PBX saves serious cash for Michigan CAT"[19c] "SIP Trunking: The Savings Are There But Transition is Complex"[20a] "All-Optical Networking- Evolution, Benefits,

Challenges"[20b] "Breaking the Light Barrier"[21] "Evolution of Packet-Optical Integration in Backbone and

Metropolitan High-Speed Networks"

Final Results for Exam #1 (90 points)Hi = 65.6, Low = 46.4, Ave = 69.96, σ = 10.05A > 78, B > 65, C > 56, D > 47

Exam #2 (Internet thru ???)28 October (Live)< 4 November (Distant Learning)

ECEN5553 Telecom SystemsWeek #9[19a] "IT Helps Passengers, Crew Navigate Gigantic Oasis of

the Seas Cruise Ship"[19b] "Open source IP PBX saves serious cash for Michigan CAT"[19c] "SIP Trunking: The Savings Are There But Transition is Complex"[20a] "All-Optical Networking- Evolution, Benefits,

Challenges"[20b] "Breaking the Light Barrier"[21] "Evolution of Packet-Optical Integration in Backbone and

Metropolitan High-Speed Networks"

Final Results for Exam #1 (90 points)Hi = 65.6, Low = 46.4, Ave = 69.96, σ = 10.05A > 78, B > 65, C > 56, D > 47

Exam #2 (Internet thru ???)28 October (Live)< 4 November (Distant Learning)

VoIP System with Gateways VoIP System with Gateways

1

RoutersA

B

4 3

Voice Switch/Gateways

MPLS could nail down paths.DiffServ could give voice priority.

Voice Switch/Gateways

2

Network Used for Numerical Results to follow... Network Used for Numerical Results to follow...

1

OC-12 VoIP Backbone

Routers

A

B

43

Voice Switch/Gateways

OC-3 Access

G.729 Coders.MPLS could nail down paths.20 msec end-to-end propagation delay

Voice Switch/Gateways

2

150 msec End-to-End Delay1 Frame per packet150 msec End-to-End Delay1 Frame per packet

Voice Coding Delay (.015)+ Packet Assembly Delay (1*.010)

+ End-to-End Propagation Delay (.020) + Service Times

+ worst case Queuing Delays at the voice source and all intermediate packet switches

+ Receiver De-Jitter Buffer Delay+ Voice Decoding Delay (.010)

= 55 msec

95 msec to spend - trunks can be heavily loaded

But most bits moved are overhead (47 out of 57B).

Gateway A to Gateway B PathGateway A to Gateway B Path

Tim

e

Our Packet

GA R4 R3 R2 GB OC-3 OC-12 OC-12 OC-3

Packet 1

Packet 1

Packet 4M

Packet 1

Packet 4M

Packet M Packet 1

Packet M

M Packets

IAT

Packet 1

Wor

st C

ase

Del

iver

y

Distance

150 msec End-to-End Delay5 Frames per packet150 msec End-to-End Delay5 Frames per packet

Voice Coding Delay (.015)+ Packet Assembly Delay (5*.010)

+ End-to-End Propagation Delay (.020) + Service Times

+ worst case Queuing Delays at the voice source and all intermediate packet switches

+ Receiver De-Jitter Buffer Delay+ Voice Decoding Delay (.010)

= 95 msec

55 msec to spend

Optimal for this example.

150 msec End-to-End Delay10 Frames per packet150 msec End-to-End Delay10 Frames per packet

Voice Coding Delay (.015)+ Packet Assembly Delay (10*.010)

+ End-to-End Propagation Delay (.020) + Service Times

+ worst case Queuing Delays at the voice source and all intermediate packet switches

+ Receiver De-Jitter Buffer Delay+ Voice Decoding Delay (.010)

= 145 msec

5 msec to spend - Trunks can't carry much traffic

But traffic carried is 2/3 voice (100 out of 147B).

Ten Voice Frames per PacketTen Voice Frames per Packet Trunk Capacity limits (622.08 Mbps trunk)Trunk Capacity limits (622.08 Mbps trunk)

594.4 Mbps * 100 msec/IAT = 59.44 Mb/IAT594.4 Mbps * 100 msec/IAT = 59.44 Mb/IAT Packet Size = 47B + 100B = 1,176 bitsPacket Size = 47B + 100B = 1,176 bits (59.44 Mb/IAT) / (1,176 bits/packet) (59.44 Mb/IAT) / (1,176 bits/packet)

= 50,544 packets can be moved every 100 msec= 50,544 packets can be moved every 100 msec End-to-End Delivery DelayEnd-to-End Delivery Delay

Time to inject on 622.08 Mbps line = Time to inject on 622.08 Mbps line = 1,176 / 594.4 Mbps = 1.978 micro sec1,176 / 594.4 Mbps = 1.978 micro sec

Time to inject on 155.52 Mbps line =Time to inject on 155.52 Mbps line =1,176 / 148.6 Mbps = 7.914 micro sec1,176 / 148.6 Mbps = 7.914 micro sec

5 msec 5 msec >> (M +1)7.914 micro + 2*1.978 micro (M +1)7.914 micro + 2*1.978 micro M M << 630 calls 630 calls

Can support 4*M = 2,520 OC-12 callsCan support 4*M = 2,520 OC-12 calls

150 msec End-to-End Delay11 Frames per packet150 msec End-to-End Delay11 Frames per packet

Voice Coding Delay (.015)+ Packet Assembly Delay (11*.010)

+ End-to-End Propagation Delay (.020) + Service Times

+ worst case Queuing Delays at the voice source and all intermediate packet switches

+ Receiver De-Jitter Buffer Delay+ Voice Decoding Delay (.010)

White Items = 155 msec0 msec to spend

Impossible to meet delivery specification.

Voice Calls Possible Over an OC-12 Trunk

(G.729 Fixed Rate Coder) Voice Calls Possible Over an OC-12 Trunk

(G.729 Fixed Rate Coder)

Number of Frames per Packet

Tru

nk

Voi

ce c

alls

su

pp

orta

ble

0

10000

20000

30000

40000

1 2 3 4 5 6 7 8 9 10 11

fixed100 msec150 msec

POTS can support 8,192 calls on an OC-12

G.729 Variable Rate Coderwith Silence Suppression

G.729 Variable Rate Coderwith Silence Suppression

On a typical interactive conversation…On a typical interactive conversation…A Specific Voice is Active 40% of timeA Specific Voice is Active 40% of timeCoder generates 8 KbpsCoder generates 8 Kbps

Voice is Quiet 60% of timeVoice is Quiet 60% of timeTransmit 0 KbpsTransmit 0 Kbps

Average of 3.2 Kbps generated per Average of 3.2 Kbps generated per simplex callsimplex call

Full MeshFull MeshCO CO

CO CO

N(N-1)/2 Links 4*3/2 = 6 Links for this example.

HierarchicalHierarchical

CO CO

CO CO

One connection per Central Office.

TO

CO ConnectivityCO Connectivity

CO CO

CO CO

HierarchicalDirect Connect2nd Parallel Hierarchical

TO

TO

Minimum of two diverse routes out of Central Office.

POTS ConnectivityPOTS Connectivity Small Cities have a COSmall Cities have a CO

Big Cities have CO’sBig Cities have CO’s Hierarchical system, addHierarchical system, add

High Usage Direct Lines between CO’sHigh Usage Direct Lines between CO’s Tandem (Trunk-to-Trunk) SwitchesTandem (Trunk-to-Trunk) Switches

Minimum of two physically separate routes Minimum of two physically separate routes out of all switches desiredout of all switches desired

Best compromise of cost & reliabilityBest compromise of cost & reliability

POTSPOTS Items in a typical wired phone:Items in a typical wired phone:

microphone & speakermicrophone & speakerhybridhybriddialing circuitry (DTMF)dialing circuitry (DTMF)on/off hook switchon/off hook switchring circuitryring circuitry

Items in a typical CO:Items in a typical CO:crosspoint switchcrosspoint switchhybridshybridsA/D & D/A convertersA/D & D/A convertersecho cancelersecho cancelersTDM or VoIPTDM or VoIP

Home PhoneHome PhoneSpeaker

Microphone

Hybrid

DialingCircuitry

RingCircuitry

WallSocket

OffHook

OnHook

4 Wire 2 Wire

Home PhoneHome PhoneSpeaker

Microphone

Hybrid

DialingCircuitry

RingCircuitry

WallSocket

OffHook

OnHook

4 Wire 2 Wire

Inbound Audio

Home PhoneHome PhoneSpeaker

Microphone

Hybrid

DialingCircuitry

RingCircuitry

WallSocket

OffHook

OnHook

4 Wire 2 Wire

Sidetone

Outbound Audio

One WireOne WireSpeakerMicrophone

To get audio out of speaker, need a closed path to get a To get audio out of speaker, need a closed path to get a voltage drop across the speaker inputsvoltage drop across the speaker inputs

Need two 'wires' to get a voltage drop across a speakerNeed two 'wires' to get a voltage drop across a speaker one wire can be an actual wireone wire can be an actual wire second 'wire' can be the earthsecond 'wire' can be the earth

Very Susceptible to staticVery Susceptible to static

Earth Ground

Two WiresTwo WiresSpeakerMicrophone

Resistant to staticResistant to static Susceptible to EM interference over long distancesSusceptible to EM interference over long distances

Twisting the wires slashes interferenceTwisting the wires slashes interferenceUsed widely after 1891Used widely after 1891

This configuration provides one-way commoThis configuration provides one-way commo Need another mic, speaker, & 2 more wiresNeed another mic, speaker, & 2 more wires

Two WiresTwo Wires Speaker

Hybrids allow Telco Two Wire lines to carry both Hybrids allow Telco Two Wire lines to carry both outbound and inbound trafficoutbound and inbound traffic short distances (local loop)short distances (local loop)

Two wire local loops, instead of 4 wireTwo wire local loops, instead of 4 wire saves $$ on cable plantsaves $$ on cable plant

HybridHybrid

Four WiresFour WiresSpeakerMicrophone

Easier to amplify traffic moving one directionEasier to amplify traffic moving one direction Telco Four Wire linesTelco Four Wire lines

2, one-way, 2 wire connections2, one-way, 2 wire connections Long distanceLong distance

Speaker Microphone

Amp

Amp

Dual Tone MultifrequencyDual Tone Multifrequency

POTS Connectivity (1920)POTS Connectivity (1920)

Phone Phone

CO CO

CopperLocalLoop

CopperLocalLoop

4 Wire 4 Wire2 Wire 2 Wire

Analog

CopperLongHaul

4 Wire

POTS Connectivity (1970)POTS Connectivity (1970)

Phone Phone

CO CO

CopperLocalLoop

CopperLocalLoop

4 Wire 4 Wire2 Wire 2 Wire

CopperLongHaul

4 Wire

Analog Analog Digital TDM64 Kbps

POTS Connectivity (1990)POTS Connectivity (1990)

Phone Phone

CO CO

Fiber OpticTrunk

CopperLocalLoop

CopperLocalLoop

4 Wire 4 Wire2 Wire 2 Wire‘4 Wire’

Analog Analog Digital TDM64 Kbps

Simplified Central Office SwitchSimplified Central Office Switch

SpaceSwitch

Loc

al L

oop

s

Hybrid EchoCanceler

A/D

D/A

TDMMux

TDMdeMux

+

T1 Line2 Wire 4 Wire

Analog Digital

Simplified CO-to-CO connectivitySimplified CO-to-CO connectivity

SpaceSwitch

Loc

al L

oops

HybridEcho

Canceler

A/D

D/A

TDMMux

TDMdeMux

+

SpaceSwitch

Loc

al L

oops

HybridEcho

Canceler

A/D

D/A

TDMMux

TDMdeMux

+

The Legacy Phone System...The Legacy Phone System... Parts are 4 wire (headset and long haul)Parts are 4 wire (headset and long haul)

4 wire = two unidirectional simplex signals4 wire = two unidirectional simplex signals simplex signals make amplification a lot easiersimplex signals make amplification a lot easier

Parts are 2 wire (local loop)Parts are 2 wire (local loop) 2 wire = one bi-directional full duplex signal2 wire = one bi-directional full duplex signal Turn-of-the-century decision to save $$$ and go 2 wire on local Turn-of-the-century decision to save $$$ and go 2 wire on local

loopsloops Parts are analog (phone & local loop)Parts are analog (phone & local loop)

About 70-80% of U.S. Local Loops are copper all-the-wayAbout 70-80% of U.S. Local Loops are copper all-the-way Parts are digital Parts are digital

(long haul, most CO switches, some local loops)(long haul, most CO switches, some local loops) About 20-30% of U.S. Local Loops use Digital Loop Carriers About 20-30% of U.S. Local Loops use Digital Loop Carriers

The Legacy Phone System...The Legacy Phone System...

4 Wire to 2 Wire Conversion at Central 4 Wire to 2 Wire Conversion at Central Office Hybrids can cause some problemsOffice Hybrids can cause some problems Singing (Cure: Attenuation)Singing (Cure: Attenuation) Echoes (Cure: Echo Canceler)Echoes (Cure: Echo Canceler)

Analog to Digital Conversion points also cause some Analog to Digital Conversion points also cause some problemsproblems CO Switch filters on analog voice lines, necessary to limit CO Switch filters on analog voice lines, necessary to limit

noise and interference on voice circuits, limit dial-up modem noise and interference on voice circuits, limit dial-up modem data speeds to about 33 Kbpsdata speeds to about 33 Kbps

Trend is to an all-digital systemTrend is to an all-digital system U.S. long haul POTS voice circuits use digital Time U.S. long haul POTS voice circuits use digital Time

Division Multiplexing or VOIPDivision Multiplexing or VOIP

TDMTDMfrequency

tim

e

1

2

3

1etc.

One 8 bit time slot provided for eachphone call every 1/8000th second.

24 bits in

1/8000 second

(192 Kb

ps)

Integrated Services Digital NetworkIntegrated Services Digital Network

Phone Phone

CO CO

Fiber OpticTrunk

CopperLocalLoop

CopperLocalLoop

4 Wire 4 Wire2 Wire 2 Wire‘4 Wire’

Digital TDM64 Kbps

PC Modems & POTSPC Modems & POTS Band Pass Filter suppresses energy Band Pass Filter suppresses energy

outside voice bandwidth (about 3,500 Hz)outside voice bandwidth (about 3,500 Hz)

Band Pass Filter

≈ 3.5 KHz

SamplerFs = 8 KHz

TwistedPair Cable

Quantize256 levels

Code8 bits/sample

64 Kbps

A/D Converter

A/D Converter

PC Dial-Up Modems & POTSPC Dial-Up Modems & POTS PC Bit Stream has a significant amount of energy outside 3.5 KHz filter BW.PC Bit Stream has a significant amount of energy outside 3.5 KHz filter BW. Modems squash the energy into the pass band of the filter (at a much reduced Modems squash the energy into the pass band of the filter (at a much reduced

bit rate).bit rate).

PC

Quantize256 levels

Code8 bits/sample

64 Kbps

Band Pass Filter

≈ 3.5 KHz)

SamplerFs = 8 KHz

TwistedPair Cable

PSTN Digital HierarchyPSTN Digital Hierarchy

Now obsolete except for some T1 & T3Now obsolete except for some T1 & T3on Local Loopson Local Loops