Interconnected Systems Modern Telecommunication Systems and their Impact on QoS and Q oe

Transcription

1 Interconnected Systems - Modern Telecommunication Systems and their Impact on QoS and QoE H. W. Gierlich HEAD acoustics GmbH

2 Parameters influencing QoS Memory/ Experience Emotions Attitude/ Motivation User Quality of Service/ Experience? Speech Communication Quality Service Performance Equipment Performance Usability Satisfaction Comfort Costs Acceptance *based on S. Möller: Assessment and Prediction of Speech Quality in Telecommunications Interconnected Systems HEAD acoustics GmbH 2

3 Speech Communication from the user s perspective talking situation speech quality listening situation conversational situation Interconnected Systems HEAD acoustics GmbH 3

4 Outline Communication systems and interconnection overview Impact of Delay Coding Noise and noise cancellation Insufficient echo loss/improper echo cancellation Cascading of signal processing Missing signaling information between endpoints and network elements Summary Interconnected Systems HEAD acoustics GmbH 4

5 Terminal - Network typical elements found in modern connections Coder 1 Coder 2 VAD jitter buffer MT BSS MSC EC 1 EC 2 GW GW EC ISC EC 4 jitter buffer VAD Mobile Network IP-Network PSTN Long distance carrier Provider A Provider B Coder 3 Coder 4 VAD jitter buffer ISC GW GW 3 4 ISC LE CT EC 5 EC 6 EC 7 EC 8 jitter buffer VAD PSTN IP-Network Provider C PSTN Interconnected Systems HEAD acoustics GmbH 5

6 Delay aggregation g (I) Coder 1 Coder 2 VAD jitter buffer MT BSS MSC EC 1 EC 2 GW GW 1 2 EC 3 ISC EC 4 jitter buffer VAD Mobile Network Provider A IP-Network Provider B PSTN Long distance carrier t MT1 t MNA t IPB t PSTN1 t LDC (10-50ms) ( 80ms) (10-400ms) (1-10ms) ( 240ms, Satellite) ( 20 ms, fiber) Interconnected Systems HEAD acoustics GmbH 6

7 Delay aggregation g (II) Coder 4 Coder 3 VAD jitter buffer ISC GW GW 3 4 ISC LE CT EC 5 EC 6 EC 7 EC 8 jitter buffer VAD PSTN IP-Network Provider C PSTN t PSTN2 t IPC t PSTN3 t CT1 (1-10ms) 10 (10-400ms) (1-10ms) 10 (13ms) Interconnected Systems HEAD acoustics GmbH 7

8 Delay and Influence of Jitter: Gateways max. MOS-LQO TOSQA delay average min TMOS de elay / ms 2 min average max. delay %, 0ms, 0%, 0ms 1%, 0ms 2%, 0ms 3%, 0ms 5%, 0ms 1%, 20ms, 1%, 20ms, VAD on r=0.9 (fix r=0.5 (fix delay 50ms) delay 50ms) network conditions 0 average, min. and max. PESQ for all manufacturers Source: ETSI SQTE, G.711, 10 ms Interconnected Systems HEAD acoustics GmbH 8

9 Delay aggregation g (III) t oneway = t MT1 + t MNA + t IPB + t PSTN1 + t LDC + t PSTN2 + t IPC + t PSTN3 Best case (no sattelite) = ( )ms = 146ms Worst case = ( )ms = 1113 ms Interconnected Systems HEAD acoustics GmbH 9

10 E-model: Influence of delay If no terminal impairment except TCLw: 146 ms/55 db TCLw 1113 ms/55 db TCLw R_ 87,9 MOS (4.5) 4,2 R_ 26,6 MOS (4.5) 1,5 146 ms/35 db TCLw 1113 ms/35 db TCLw R_ 82,1 MOS (4.5) 4,1 R_ 4,3 MOS (4.5) 1 Interconnected Systems HEAD acoustics GmbH 10

11 ITU-T G.114: Effect of transmission time Users very satisfied Users satisfied ting R E-model rat Mouth-to-ear-delay/ms Some users dissatisfied Many users dissatisfied Nearly all users dissatisfied G.114_F01 Interconnected Systems HEAD acoustics GmbH 11

12 Terminal - Network Coding and transcoding AMR/EFR G. 729 Coder 1 Coder 2 VAD jitter buffer MT BSS MSC EC 1 EC 2 GW GW 1 2 EC 3 ISC EC 4 jitter buffer VAD Mobile Network IP-Network PSTN Long distance carrier Provider A Provider B G. 723 Coder 3 G. 726 Coder 4 VAD jitter buffer ISC GW GW 3 4 ISC LE CT EC 5 EC 6 EC 7 EC 8 jitter buffer VAD PSTN IP-Network Provider C PSTN Interconnected Systems HEAD acoustics GmbH 12

13 E-Model: The effect of codec tandeming Type Ie (G.113) Coder 1 EFR (ACELP) 5 Coder 2 G (CS-ACELP) Coder 3 G. 723 (ACELP, 5.3 kbit/s) Coder 4 G. 726 (ADPCM, 32 kbit/s) 19 => Ie(tot) = = 46 R_ 47,2 MOS (4.5) 243 2,43 7 Interconnected Systems HEAD acoustics GmbH 13

14 Objective Testing based on ITU-T P.862 and others Instrumental measures based on hearing models - Perceptual models: Modeling the Results of Auditory Tests by Comparison of Reference Speech Signal with Processed Speech Signal Typical Processing Steps (Schematic): Results of Listening Tests! Speech Signal Test Object Adaptation processed signal reference signal Hearing Model Hearing Model Comparison, Reference, Reduction, Signal Value S index Q PSQM P.861 PESQ P.862 PSQM99 KPN PAMS BT TOSQA T-Systems ITU-T PACE Ascom VQI Ericsson P.OLQA Interconnected Systems HEAD acoustics GmbH 14

15 Example: Tandeming of Codecs CDMA CDMA GSM Variable Fixed enhanced rate max. fullrate rate Send signal (without coding): 1x coding/decoding (.wav) (.wav) 2x coding/decoding (.wav) (.wav) Source: Harman/Becker Interconnected Systems HEAD acoustics GmbH 15

16 Example: Tandeming of Codecs Vehicle BT GSM Preamp. A/D MOST- BUS Hands-Free Algorithm BT chip Mobile Phone GSM Network CVSD & EFR CVSD & FR Microphone & CVSD & FR Microphone (speech h& noise) )&CVSD&FR & (.wav) (.wav) (.wav) (.wav) (.wav) Interconnected Systems HEAD acoustics GmbH 16

17 Echo loss in IP DECT/CATiq configurations Assuming G.711 speech coder, no compression Assumimg no transcoding Assuming no VAD, sufficient bandwidth DECT Echo canceller w/o echo, ISDN echo canceller with low level echos Echoes, clipping! DECT terminals, delay. Audible echoes! ISDN GW IAD DECT Coding, packetization, buffer, Delay! Degrades conversational quality! EC in IAD!... DECT delay, DECT distortions! Packet loss and jitter under network load, PLC, jitter buffer Artifacts, delay! Interconnected Systems HEAD acoustics GmbH 17

18 Echo Performance Echo Cancellation in IAD Echo loss 36.7 db Simulated DECT echo Spectrum avg. FFT Size:8192 Overlap:0,0% Rectangle L/dB[V] EC t d f/hz t + Network delay 100, 150, ms!!! Echo loss 31 db t d 30 ms Interconnected Systems HEAD acoustics GmbH 18

19 DECT/CATiq Echoes t d DECT t d t d linear non-linear Spectrum avg. FFT Size:8192 Overlap:0,0% Rectangle L/dB[Pa] -20 Spectrum avg. FFT Size:8192 Overlap:0,0% Rectangle L/dB[Pa] -20 Spectrum avg. FFT Size:8192 Overlap:0,0% Rectangle L/dB[Pa] f/hz f/hz f/hz Echo loss 17.8 db Echo loss 31.0 db Echo loss 36.3 db Interconnected Systems HEAD acoustics GmbH 19

20 Tandeming of signal processing: Car hands-free and network Car audio Hands-free Mobile playback Terminal network system gain EQU gain gain Audio playback system in the echo path of ( both ) ECs EC EC Information exchange between gateway and terminal not possible ES NR NR Microphone array signal processing, NR, AGC,/gain ES NR, NR, AGC,/gain Tandemed, NR, AGC Interconnected Systems HEAD acoustics GmbH 20

21 Tandeming of echo cancellation and consequences on double talk performance Mobile Terminal gain Mobile Network Base Station gain EC EC Influence on double talk performance Both EC & ES active ES NR AGC/ gain ES NR AGC/ gain Network 1 Network 2 Interconnected Systems HEAD acoustics GmbH 21

22 Double Talk Performance Limits Characterization of HFT acc. to ITU-T P.340 MOS 4,0 4,0 3,5 3,5 3,0 3,0 2,5 2,5 2,0 2,0 TELR DT < 13 [db] A Hsdt [db] > 15 A Hrdt [db] > 12 Type 2 Type 1 Type 3 Type 2a Type 2b Type 2c TELR DT [db] < 21 A Hsdt [db] > 12 A Hrdt [db] > 10 Interconnected Systems HEAD acoustics GmbH 22

23 Background noise transmission Mobile Terminal gain Mobile Network Base Station gain EC EC CN Influence on double talk performance Both EC & ES active ES NR AGC/ gain (.wav) ES NR AGC/ gain Network 1 Network 2 Interconnected Systems HEAD acoustics GmbH 24

24 Testing and Qualification The new Objective Model for Speech with Background Noise: ETSI EG Processed speech p(k) Objective Model S-MOS (Speech-MOS) N-MOS (Noise-MOS) G-MOS (Global-MOS) Quality of speech + noise transmission Interconnected Systems HEAD acoustics GmbH 25

25 Summary Delay aggregation g is the biggest problem in modern network configurations! Potential problems in a connection may occur due to tandemed signal processing in terminals and networks Network planning and quality evaluation needs to involve all components of a connection and their interaction! Currently no signaling is possible between terminals and networks for information exchange about signal processing active in the different devices Related work: G developed in SG16: Mechanism for Dynamic Coordination of Signal Processing Functions G.115.x sub series (Logic and protocols for the control of signal processing network elements and functions) may potentially be enhanced to support this capability Interconnected Systems HEAD acoustics GmbH 32