ECEN5553 Telecom Systems Week #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 = A > 78, B > 65, C > 56, D > 47 Exam #2 (Internet thru ???) 28 October (Live) < 4 November (Distant Learning)

VoIP System with Gateways 1 Routers A 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... 1 OC-12 VoIP Backbone Routers A B 4 3 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 Delay 1 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 Path Time Our Packet GA R4 R3 R2 GB OC-3 OC-12 OC-12 OC-3 Packet 1 Packet 4M Packet 1 Packet 4M Packet M Packet 1 Packet M M Packets IAT Packet 1 Worst Case Delivery Distance

150 msec End-to-End Delay 5 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 Delay 10 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 Packet n Trunk Capacity limits ( Mbps trunk) u Mbps * 100 msec/IAT = Mb/IAT u Packet Size = 47B + 100B = 1,176 bits u (59.44 Mb/IAT) / (1,176 bits/packet) = 50,544 packets can be moved every 100 msec n End-to-End Delivery Delay u Time to inject on Mbps line = 1,176 / Mbps = micro sec u Time to inject on Mbps line = 1,176 / Mbps = micro sec u 5 msec > (M +1)7.914 micro + 2*1.978 micro F M < 630 calls n Can support 4*M = 2,520 OC-12 calls

150 msec End-to-End Delay 11 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 msec 0 msec to spend Impossible to meet delivery specification.

Voice Calls Possible Over an OC-12 Trunk (G.729 Fixed Rate Coder) Number of Frames per Packet Trunk Voice calls supportable fixed 100 msec 150 msec POTS can support 8,192 calls on an OC-12

G.729 Variable Rate Coder with Silence Suppression n On a typical interactive conversation… A Specific Voice is Active 40% of time Coder generates 8 Kbps n Voice is Quiet 60% of time Transmit 0 Kbps n Average of 3.2 Kbps generated per simplex call

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

Hierarchical CO One connection per Central Office. TO

CO Connectivity CO Hierarchical Direct Connect 2nd Parallel Hierarchical TO Minimum of two diverse routes out of Central Office.

POTS Connectivity  Small Cities have a CO Big Cities have CO’s  Hierarchical system, add  High Usage Direct Lines between CO’s  Tandem (Trunk-to-Trunk) Switches  Minimum of two physically separate routes out of all switches desired  Best compromise of cost & reliability

POTS  Items in a typical wired phone: microphone & speaker hybrid dialing circuitry (DTMF) on/off hook switch ring circuitry  Items in a typical CO: crosspoint switch hybrids A/D & D/A converters echo cancelers TDM or VoIP

Home Phone Speaker Microphone Hybrid Dialing Circuitry Ring Circuitry Wall Socket Off Hook On Hook 4 Wire 2 Wire

Home Phone Speaker Microphone Hybrid Dialing Circuitry Ring Circuitry Wall Socket Off Hook On Hook 4 Wire 2 Wire Inbound Audio

Home Phone Speaker Microphone Hybrid Dialing Circuitry Ring Circuitry Wall Socket Off Hook On Hook 4 Wire 2 Wire Sidetone Outbound Audio

One Wire Speaker Microphone n To get audio out of speaker, need a closed path to get a voltage drop across the speaker inputs n Need two 'wires' to get a voltage drop across a speaker u one wire can be an actual wire u second 'wire' can be the earth n Very Susceptible to static Earth Ground

Two Wires Speaker Microphone n Resistant to static n Susceptible to EM interference over long distances u Twisting the wires slashes interference Used widely after 1891 n This configuration provides one-way commo u Need another mic, speaker, & 2 more wires

Two Wires Speaker n Hybrids allow Telco Two Wire lines to carry both outbound and inbound traffic u short distances (local loop) n Two wire local loops, instead of 4 wire u saves $$ on cable plant Hybrid

Four Wires SpeakerMicrophone n Easier to amplify traffic moving one direction n Telco Four Wire lines u 2, one-way, 2 wire connections u Long distance SpeakerMicrophone Amp

Dual Tone Multifrequency

POTS Connectivity (1920) Phone CO Copper Local Loop Copper Local Loop 4 Wire 2 Wire Analog Copper Long Haul 4 Wire

POTS Connectivity (1970) Phone CO Copper Local Loop Copper Local Loop 4 Wire 2 Wire Copper Long Haul 4 Wire Analog Digital TDM 64 Kbps

POTS Connectivity (1990) Phone CO Fiber Optic Trunk Copper Local Loop Copper Local Loop 4 Wire 2 Wire ‘4 Wire’ Analog Digital TDM 64 Kbps

Simplified Central Office Switch Space Switch Local Loops Hybrid Echo Canceler A/D D/A TDM Mux TDM deMux + T1 Line2 Wire 4 Wire AnalogDigital

Simplified CO-to-CO connectivity Space Switch Local Loops Hybrid Echo Canceler A/D D/A TDM Mux TDM deMux + Space Switch Local Loops Hybrid Echo Canceler A/D D/A TDM Mux TDM deMux +

The Legacy Phone System...  Parts are 4 wire (headset and long haul)  4 wire = two unidirectional simplex signals  simplex signals make amplification a lot easier  Parts are 2 wire (local loop)  2 wire = one bi-directional full duplex signal  Turn-of-the-century decision to save $$$ and go 2 wire on local loops  Parts are analog (phone & local loop)  About 70-80% of U.S. Local Loops are copper all-the-way  Parts are digital (long haul, most CO switches, some local loops)  About 20-30% of U.S. Local Loops use Digital Loop Carriers

The Legacy Phone System...  4 Wire to 2 Wire Conversion at Central Office Hybrids can cause some problems  Singing (Cure: Attenuation)  Echoes (Cure: Echo Canceler)  Analog to Digital Conversion points also cause some problems  CO Switch filters on analog voice lines, necessary to limit noise and interference on voice circuits, limit dial-up modem data speeds to about 33 Kbps  Trend is to an all-digital system  U.S. long haul POTS voice circuits use digital Time Division Multiplexing or VOIP

TDM frequency time etc. One 8 bit time slot provided for each phone call every 1/8000th second. 24 bits in 1/8000 second (192 Kbps)

Integrated Services Digital Network Phone CO Fiber Optic Trunk Copper Local Loop Copper Local Loop 4 Wire 2 Wire ‘4 Wire’ Digital TDM 64 Kbps

PC Modems & POTS n Band Pass Filter suppresses energy outside voice bandwidth (about 3,500 Hz) Band Pass Filter ≈ 3.5 KHz Sampler F s = 8 KHz Twisted Pair Cable Quantize 256 levels Code 8 bits/sample 64 Kbps A/D Converter

PC Dial-Up Modems & POTS n PC Bit Stream has a significant amount of energy outside 3.5 KHz filter BW. n Modems squash the energy into the pass band of the filter (at a much reduced bit rate). PC Quantize 256 levels Code 8 bits/sample 64 Kbps Band Pass Filter ≈ 3.5 KHz) Sampler F s = 8 KHz Twisted Pair Cable

PSTN Digital Hierarchy n Now obsolete except for some T1 & T3 on Local Loops