1. Kommunikatsiooniteenuste arendus IRT0080
Loeng 3 Avo Ots telekommunikatsiooni õppetool,
TTÜ raadio- ja sidetehnika inst.

2. Võrgukihi kommutaator

3. 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.

4. Application layer protocol Transport protocol
Data loss
Bandwidth
Time sensitive
Application layer protocol
Transport protocol
File transfer No
Elastic
FTP
TCP
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

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

6. Paketi moodustamine IP päis Kaadri päis Transpordi päis lugemid One
Sample
One 8-bit
Sample
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

7. 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: bytes UDP: bytes RTP: bytes Voice Payload: 20 bytes bytes

8. Paketiülekande hinnangud

9. Areng Virtual Reality WLAN Bluetooth evolved 3G Always Best Connected
384 kbps - 20 Mbps
Always Best Connected
Ad hoc networks
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
kbps 4G
100 Mbps?

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

11. 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.

12. 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 → lugemit/s
16 b/lugem
Rs=16x44100= 705,6 kb/s ühe helikanali kohta

13. 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 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.

14. 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

15. 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

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

17. Voice Codec Standards G.711 64 kbps using PCM
G kbps using LP
G kbps using ADPCM
G kbps using low delay LP
G kbps using LP

18. Aegmultipleksimine A B C D t

19. IKM kaader

20. Aeg ja ruumiline kommuteerimine
sisendid
väljundid t

21. TSI Timeslot interchange MUX DEMUX Kaadrimälu Juhtmälu1 j c i
(i)
(j)
Timeslot interchange
MUX
DEMUX
Kaadrimälu
Juhtmälu
Ajapilude loendur
Time slot counter
Write
access
Read
Data in
out

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

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

24. Lingid http://en.wikipedia.org/wiki/Time-division_multiplexing