Kommunikatsiooniteenuste arendus IRT0080 Loeng 3 Avo Ots telekommunikatsiooni õppetool, TTÜ raadio- ja sidetehnika inst. avo.ots@ttu.ee

Võrgukihi kommutaator

PBX Transformation Telephony Server PBX Strategic Planning Assumption: Irrespective of user benefits, by 2004, vendors will succeed in making IP-based telephony products the de facto architecture standard for new premise-based voice switching (0.8 probability). Telephony Server PBX Source: Gartner Research The driving forces for the adoption of IP/PBX systems are vendor “push” and lower purchasing prices to enterprises — not new features and applications as stressed by the media. Initial products include those of Lucent, Siemens and Cisco; these products are geared to small-enterprise sites. Our product evaluations and cost analysis demonstrate that, at best, present day IP/PBX systems have no cost advantage over traditional proprietary circuit-switched PBXs. We expect that the high prices of the IP Telephony equipment will continue until at least mid-2003 (0.7 probability). Manufacturers of IP/PBX systems will look to lower prices by eliminating PBX hardware components, which will offer a means for centralized management using centralized directories that communicate across various platforms. They will also offer extensions from a central PBX to branch IP/PBX systems and significantly discount software applications. Action Item: Enterprises should not move to IP/PBX systems unless a lower total cost of ownership (TCO) can be achieved. They must also ascertain whether new architecture systems will have the features required for their business; “feature debt” for IP/PBX systems vs. traditional circuit switches will continue during the next two years.

Application layer protocol Transport protocol Data loss Bandwidth Time sensitive Application layer protocol Transport protocol File transfer No Elastic FTP TCP E-mail SMTP Web documents Elastic, Kbps HTTP Real-time audio/video Yes Kbps, Mbps Yes, 100s of Msec Proprietary TCP or UDP Stored audio/video Yes, sec Proprietary, NFS Interactive games Kbps Financial applications Both Transmission Control Protocol User Datagram Protocol TCP: guarantee: deliver all data; no guarantee: rate, delay; connection; congestion control UDP: no guarantee: deliver all data, order, delay; no connection; no congestion control

Efficiency of transport Efficiency & quality Packet size Codec Efficiency of transport Voice quality Dejittering delay Echo control Header compression

Paketi moodustamine IP päis Kaadri päis Transpordi päis lugemid One Sample One 8-bit Sample 00000100 00000011 00000111 Analog Signal ADC We have been looking at analog-to-digital conversion. Signals coming from the PSTN, however, need to undergo digital to analog conversion. Each sample is reconverted into a volume level, which is maintained for 1/8000 second. Although the resultant signal does not look analog, if there are 8,000 samples per second it will sound analog—smoothly changing in volume. IP päis Kaadri päis Transpordi päis lugemid

Kõne pakettvõrgus Kõnesignaali komprimeeriv koodek (ITU-T G.729A, 8 kbit/s) VAD (Voice Activity Detection), Silence Suppression , Comfort Noise Generation Töödeldava lugemikogumi pikkus: 20 ms, => Payload 20 octets Ethernet+FCS+Preamble: 26 bytes 802.1q VLAN Tagging 4 bytes IP: 20 bytes UDP: 8 bytes RTP: 12 bytes Voice Payload: 20 bytes ---------- 90 bytes

Paketiülekande hinnangud

Areng Virtual Reality WLAN Bluetooth evolved 3G Always Best Connected 384 kbps - 20 Mbps Always Best Connected Ad hoc networks xMbps @ 60 GHz TDMA EDGE WCDMA cdma2000 3G 384 kbps - 2 Mbps Always Best Connected GSM MC1X GPRS evolved 2G 64–144 kbps PDC New air- interface? Optical Networking cdmaOne 2G 9.6 - 14.4 kbps 4G 100 Mbps?

User interface, e.g. screen-size Mobiilsus High-end Datacom users Mobility Processing capacity User interface, e.g. screen-size

Network paradigm shift Current Future In a converged network, services will no longer be tied to a one type of network. Instead, the converged network will deliver all services.

Kõne (voice) & heli (audio) Kõne telefonis Ws = 4 kHz → 8000 lugemit/s 8 b/lugem Rs=8x8000 = 64 kb/s CD Audio Ws = 22 kHz → 44100 lugemit/s 16 b/lugem Rs=16x44100= 705,6 kb/s ühe helikanali kohta

IKM (PCM) PAM diskreetija kvantija kodeerija Pidev ajas, Pidev amplituud, Analoog sisendsignaal Ajas diskreetne, PAM impulsid Diskreetne ajas, Diskreetne amplituud, PCM impulsid Digitaalne Bitivoog väljundsignaal Thus, PCM starts with a continuous-time, continuous-amplitude (analog) signal, from which a digital signal is produced, as shown in Stallings DCC8e Figure 5.17. The digital signal consists of blocks of n bits, where each n-bit number is the amplitude of a PCM pulse. On reception, the process is reversed to reproduce the analog signal. Notice, however, that this process violates the terms of the sampling theorem. By quantizing the PAM pulse, the original signal is now only approximated and cannot be recovered exactly. This effect is known as quantizing error or quantizing noise. Each additional bit used for quantizing increases SNR by about 6 dB, which is a factor of 4.

Analoogsignaali digitaliseerimine Lugemid (sample) diskreetses ajas ja lähendatud amplituudväärtustel Original signal Sample value D/2 3D/2 5D/2 7D/2 -D/2 -3D/2 -5D/2 -7D/2 Approximation 3 bits / sample Rs = Bit rate = # bits/sample x # samples/second

Kvanteerimine Quantizer maps input into closest of 2m representation values output y(nT) 3.5 2.5 1.5 0.5     -0.5     Quantization error: “noise” = x(nT) – y(nT) -1.5 input x(nT) -2.5 -3.5 D/2 3D/2 5D/2 7D/2 -D/2 -3D/2 -5D/2 -7D/2 Original signal Sample value Approximation 3 bits / sample

A/D ja D/A muundus A/D D/A diskreetimissamm=1/(2Fmax) muunduse viga=1/(2n) Diskreetimissamm 125 mikrosek, kvantimisnivoosid 256 64 kbit/s, ~ ITU-T G.711

Voice Codec Standards G.711 64 kbps using PCM G.723.1 5-6 kbps using LP G.726 16-40 kbps using ADPCM G.728 16 kbps using low delay LP G.729 8 kbps using LP

Aegmultipleksimine A B C D t

IKM kaader

Aeg ja ruumiline kommuteerimine sisendid väljundid t

TSI Timeslot interchange MUX DEMUX Kaadrimälu Juhtmälu 1 j c i (i) (j) Timeslot interchange MUX DEMUX Kaadrimälu Juhtmälu Ajapilude loendur Time slot counter Write access Read Data in out

Kõnekvaliteedi kategooriad MOS P.800 1,0…5,0 E-mudel MOS 1,0…4,5 NetIQ Rmax=91,96 MOS 1,0…4,38

Mobiilsus home agent Internet w/ Mobile IP mobile access network base station home agent Internet w/ Mobile IP mobile mobile access network

Lingid http://en.wikipedia.org/wiki/Time-division_multiplexing http://en.wikipedia.org/wiki/QoS http://en.wikipedia.org/wiki/PBX http://en.wikipedia.org/wiki/Digital_phone http://en.wikipedia.org/wiki/Telephone