ECEN5553 Telecom Systems Week #9 [19a] "IT Helps Passengers, Crew Navigate Gigantic Oasis of the...
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Transcript of ECEN5553 Telecom Systems Week #9 [19a] "IT Helps Passengers, Crew Navigate Gigantic Oasis of the...
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