Network QoS and quality perception of compressed and uncompressed high-resolution video transmissions [Elektronische Ressource] = Netzwerk-Dienstqualität (QoS) und Qualitätswahrnehmung bei komprimierten und unkomprimierten hochauflösenden Videoübertragungen / vorgelegt von Susanne G. Naegele-Jackson

De
Network QoS and Quality Perception of Compressed and Uncompressed High-Resolution Video Transmissions (Netzwerk Dienstqualität (QoS) und Qualitätswahrnehmung bei komprimierten und unkomprimierten hochauflösenden Videoübertragungen) Der Technischen Fakultät der Universität Erlangen-Nürnberg zur Erlangung des Grades D O K T O R – I N G E N I E U R vorgelegt von Susanne G. Naegele-Jackson Erlangen - 2006 Als Dissertation genehmigt von der Technischen Fakultät der Universität Erlangen-Nürnberg Tag der Einreichung: ……………………………….……….. 07.03.2006 Tag der Promotion: ………………………………….………. 14.11.2006 Dekan: ………………………………………... Prof. Dr.-Ing. A. Leipertz Berichterstatter: Prof. Dr-Ing. R. German, Universität Erlangen-Nürnberg Prof. em. Dr.-Ing. E. Jessen, Techn. Universität München Table of Contents List of Figures ______________________________________________________ vi List of Tables _______________________________________________________ xi Abstract and Keywords________________________________________________xii Abstrakt____________________________________________________________xii Acknowledgements__________________________________________________ xiii Introduction _________________________________________________________1 PART I - Quality of Service Mechanisms for Video Transmissions ____________12 1.
Publié le : dimanche 1 janvier 2006
Lecture(s) : 23
Tags :
Source : WWW.OPUS.UB.UNI-ERLANGEN.DE/OPUS/VOLLTEXTE/2006/483/PDF/SUSANNENAEGELE-JACKSONDISSERTATION.PDF
Nombre de pages : 223
Voir plus Voir moins

Network QoS and Quality Perception of
Compressed and Uncompressed
High-Resolution Video Transmissions

(Netzwerk Dienstqualität (QoS) und
Qualitätswahrnehmung bei komprimierten und
unkomprimierten hochauflösenden Videoübertragungen)



Der Technischen Fakultät der
Universität Erlangen-Nürnberg
zur Erlangung des Grades




D O K T O R – I N G E N I E U R




vorgelegt von

Susanne G. Naegele-Jackson

Erlangen - 2006






























Als Dissertation genehmigt von
der Technischen Fakultät der
Universität Erlangen-Nürnberg


Tag der Einreichung: ……………………………….……….. 07.03.2006
Tag der Promotion: ………………………………….………. 14.11.2006
Dekan: ………………………………………... Prof. Dr.-Ing. A. Leipertz
Berichterstatter: Prof. Dr-Ing. R. German, Universität Erlangen-Nürnberg
Prof. em. Dr.-Ing. E. Jessen, Techn. Universität München

Table of Contents

List of Figures ______________________________________________________ vi
List of Tables _______________________________________________________ xi
Abstract and Keywords________________________________________________xii
Abstrakt____________________________________________________________xii
Acknowledgements__________________________________________________ xiii
Introduction _________________________________________________________1

PART I - Quality of Service Mechanisms for Video Transmissions ____________12
1. Video Signals ________________________________________________13
2. Quality of Service Mechanisms for Individual OSI Layers___________15
2.1. Physical Layer ________________________________________________________17
2.2. Data Link Layer_______________________________________________________17
2.2.1. ATM ___________________________________________________________18
2.2.2. IP Switching _____________________________________________________20
2.2.3. Fibre Channel ____________________________________________________21
2.2.4. IEEE 1394 FireWire _______________________________________________22
2.3. Network Layer23
2.3.1. Integrated Services_________________________________________________24
2.3.2. Differentiated Services _____________________________________________25
2.3.3. MPLS / GMPLS __________________________________________________27
2.4. Transport Layer28
2.4.1. XTP, TPX, MTP and RTP/RTCP _____________________________________29
2.4.2. RSVP ___________________________________________________________31
2.5. Session Layer _________________________________________________________32
2.6. Presentation Layer_____________________________________________________33
2.7. Application Layer40
3. End-to-End QoS Architectures _________________________________41
3.1. The Heidelberg, QoS-A and OMEGA Architectures _________________________41
®3.2. TrueCircuit Technology _______________________________________________43


PART II - QoS Measurements and User Perception ________________________45
4. Network Quality of Service_____________________________________46
4.1. Network QoS Parameters46
4.2. Performance Metrics ___________________________________________________53
iii
4.3. Measurements over Real Networks _______________________________________54
4.3.1. Measurements over the German Research Network G-WiN_________________54
4.3.2. Delay Measurements of Multipoint Video Conferences over the G-WiN Network65
4.3.3. Measurements over the Gigabit Testbed South (GTB) _____________________69
4.3.3.1. Test Scenario 1: ATM CTD, CDV and Cell Loss under Different Workloads_70
4.3.3.2. Test Scenario 2: ATM Cell Interarrival Times under Increasing Workloads __72
4.3.3.3. Test Scenario 3: IP over ATM vs. Internet Response Times ______________73
5. User Quality of Service ________________________________________78
5.1. Objective and Subjective Evaluation of Video Quality________________________78
5.2. Human Perception of Network Impairments _______________________________80
5.3. MPEG-2 Compression and Error Perception84
5.3.1. MPEG-2 Encapsulation _____________________________________________85
5.3.2. MPEG-2 Error Propagation and Concealment Techniques __________________88
5.3.2.1. MPEG-2 Error Propagation _______________________________________90
5.3.2.2. Error Concealment Techniques_____________________________________92
5.3.3. MPEG-2 Traffic Characteristics and Video Quality _______________________95
5.4. SDI over X Technologies ________________________________________________97
5.5. Related Work _________________________________________________________98
6. The Perception of MPEG-2 and SDI over X Video Quality under the
Influence of Network Impairments ________________________________100
6.1. QoS Impairments and Measurements ____________________________________100
6.2. Subjective Quality Evaluations of High Bit Rate MPEG-2 Video over ATM
Networks ____________________________________________________________107
6.2.1. MPEG-2 over ATM: Quality Evaluation Without Impairments _____________108
6.2.2. MPEG-2 over ATM: Measurements of Compression Delays _______________110
6.2.3. MPEG-2 over ATM: Evaluation of Loss Ratios _________________________111
6.2.4. Evaluation of Jitter ______________________________115
6.3. Subjective Quality Evaluations of High Bit Rate MPEG-2 Video over IP Networks _
_________________________________________________________________118
6.3.1. MPEG-2 over IP: Quality Evaluation Without Impairments________________119
6.3.2. MPEG-2 over IP: Compression Delays ________________________________120
6.3.3. MPEG-2 over IP: Investigation of Loss Ratios __________________________120
6.3.4. Jitter Measurements123
6.4. Subjective Quality Evaluations of Uncompressed SDI Video over ATM Networks128
6.4.1. SDI over ATM: Adaptation Delays and Loss Impairments_________________131
6.4.2. SDI over ATM: Jitter Investigations __________________________________132
6.5. Subjective Quality Evaluations of Uncompressed SDI Video over IP Networks __135
6.5.1. SDI over IP: Quality Evaluation without Impairments ____________________136
6.5.2. SDI over IP: Adaptation Delays _____________________________________137
6.5.3. SDI over IP: Investigation of Loss Ratios ______________________________137
6.5.4. SDI over IP: Jitter Impairments ______________________________________140
6.6. Subjective and Objective Error Characterization __________________________143
6.6.1. Subjective Error Characterization ____________________________________143
6.6.1.1. Subjective Observations of Block Errors ____________________________144
6.6.1.2. Subjective Evaluation of Image Definition___________________________145
6.6.1.3. Subjective Observations of Continuous Motion _______________________145
6.6.1.4. Subjective Evaluations of Color Changes146
6.6.2. Objective Error Characterization _____________________________________147
6.6.2.1. Objective Data Analysis of MPEG-2 Block Errors_____________________147
iv
6.6.2.2. Objective Data Analysis of MPEG-2 Picture Traces ___________________149
6.6.2.3. Objective Data Analysis of Frozen Frames___________________________150
6.6.2.4. Objective Investigation of Color Changes151
6.6.3. Error Frequency__________________________________________________152
6.6.4. Assessment of User Behavior _______________________________________156
7. QoS Classification ___________________________________________158
7.1. Comparison of Loss Impairments158
7.2. Comparison of Jitter Impairments162
7.3. QoS Classification Model ______________________________________________164
7.3.1. QoS Model: Dimension of Delay ____________________________________165
7.3.2. QoS Model: Dimension of Loss Ratios ________________________________166
7.3.3. QoS Model: Dimension of Jitter _____________________________________170
8. Discussion of Results _________________________________________174

Summary__________________________________________________________178
Appendix__________________________________________________________182
Glossary183
Abbreviations ______________________________________________________184
Hardware _________________________________________________________187
Bibliography_______________________________________________________188
v
Inhaltsverzeichnis

Auflistung der Grafiken_______________________________________________ vi
Auflistung der Tabellen xi
Abstract and Keywords________________________________________________xii
Abstrakt____________________________________________________________xii
Anerkennungen ____________________________________________________ xiii
Einführung__________________________________________________________1

Teil I – Mechanismen zur Unterstützung der Dienstqualität beiVideoübertragungen
___________________________________________________________________12
1. Video Signale ________________________________________________13
2. Mechanismen zur Unterstützung der Dienstqualität auf einzelnen OSI
Ebenen ________________________________________________________15
2.1. Physikalische Ebene____________________________________________________17
2.2. Data Link Ebene ______________________________________________________17
2.2.1. ATM ___________________________________________________________18
2.2.2. IP Switching _____________________________________________________20
2.2.3. Fibre Channel21
2.2.4. IEEE 1394 FireWire _______________________________________________22
2.3. Netzwerk Ebene _______________________________________________________23
2.3.1. Integrated Services_________________________________________________24
2.3.2. Differentiated Services _____________________________________________25
2.3.3. MPLS / GMPLS __________________________________________________27
2.4. Transport Ebene ______________________________________________________28
2.4.1. XTP, TPX, MTP und RTP/RTCP _____________________________________29
2.4.2. RSVP ___________________________________________________________31
2.5. Session Ebene _________________________________________________________32
2.6. Präsentationsebene_____________________________________________________33
2.7. Applikationsebene _____________________________________________________40
3. End-to-End QoS Architekturen _________________________________41
3.1. Die Heidelberg, QoS-A und OMEGA Architekturen _________________________41
®3.2. TrueCircuit Technologie _______________________________________________43

Teil II – Messungen der Dienstqualität und Benutzerwahrnehmung___________45
4. Netzwerk Dienstqualität _______________________________________46
4.1. Netzwerk QoS Parameter _______________________________________________46
vi
4.2. Performanz Metrik ____________________________________________________53
4.3. Messungen über reale Netze _____________________________________________54
4.3.1. Messungen über das Deutsche Forschungsnetz G-WiN ____________________54
4.3.2. Latenzmessungen bei Multipoint Video Konferenzen über das G-WiN ________65
4.3.3. Messungen über das Gigabit Testbed Süd (GTB) _________________________69
4.3.3.1. Test 1: ATM CTD, CDV und Zellverluste bei unterschiedlichen Auslastungen70
4.3.3.2. Test 2: ATM Cell Interarrival Times bei steigenden Auslastungen _________72
4.3.3.3. Test 3: IP über ATM vs. Internet Response Zeiten______________________73
5. Dienstqualität beim Benutzer___________________________________78
5.1. Objektive und Subjektive Bewertung von Video Qualität _____________________78
5.2. Menschliche Wahrnehmung von Netzwerkstörungen ________________________80
5.3. MPEG-2 Komprimierung und Fehlerwahrnehmung _________________________84
5.3.1. MPEG-2 Abbildung________________________________________________85
5.3.2. MPEG-2 Fehlerfortpflanzung und Techniken zur Fehlerverbergung __________88
5.3.2.1. MPEG-2 Fehlerfortpflanzung ______________________________________90
5.3.2.2. Techniken zur Fehlerverbergung ___________________________________92
5.3.3. MPEG-2 Verkehrscharakteristik und Video Qualität ______________________95
5.4. SDI über X Technologien _______________________________________________97
5.5. Verwandte Studien_____________________________________________________98
6. Die Wahrnehmung von MPEG-2 und SDI über X Video Qualität unter
dem Einfluss von Netzstörungen __________________________________100
6.1. QoS Störungen und Messungen _________________________________________100
6.2. Subjektive Qualitätsbewertungen von hochbitratigem MPEG-2 Video über ATM
Netze _______________________________________________________________107
6.2.1. MPEG-2 über ATM: Qualitätsbewertung ohne Störungen _________________108
6.2.2. MPEG-2 über ATM: Messungen der Komprimierungslatenz _______________110
6.2.3. MPEG-2 über: Bewertung von Verlustraten _______________________111
6.2.4. Bewertung von Jittereinfluss115
6.3. Subjektive Qualitätsbewertungen bei hochbitratigem MPEG-2 Video über IP Netze
_________________________________________________________________118
6.3.1. MPEG-2 über IP: Qualitätsbewertung ohne Störungen____________________119
6.3.2. MPEG-2 über IP: Komprimierungslatenzen ____________________________120
6.3.3. MPEG-2 über IP: Untersuchung von Verlustraten _______________________120
6.3.4. Jittermessungen____________________________________123
6.4. Subjektive Qualitätsbewertungen von unkomprimiertem SDI Video über ATM
Netze _______________________________________________________________128
6.4.1. SDI über ATM: Adaptationslatenz und Störungen bei Verlusten ____________131
6.4.2. SDI über ATM: Jitteruntersuchungen _________________________________132
6.5. Subjektive Qualitätsbewertungen von unkomprimiertem SDI Video über IP Netze _135
6.5.1. SDI über IP: Qualitätsbewertung ohne Störungen________________________136
6.5.2. SDI über IP: Adaptationslatenz ______________________________________137
6.5.3. SDI über IP: Untersuchung von Verlustraten ___________________________137
6.5.4. SDI über IP: Jitterstörungen ________________________________________140
6.6. Subjektive und Objektive Fehlercharakterisierung _________________________143
6.6.1. Subjektive Fehlercharakterisierung ___________________________________143
6.6.1.1. Subjektive Wahrnehmung von Blockfehlern144
6.6.1.2. Subjektive Bewertung der Bildschärfe ______________________________145
vii
6.6.1.3. Subjektive Wahrnehmung von kontinuierlicher Bewegung ______________145
6.6.1.4. Subjektive Wahrnehmung von Farbveränderungen ____________________146
6.6.2. Objektive Fehlercharakterisierung____________________________________147
6.6.2.1. Objektive Daten Analyse von MPEG-2 Blockfehlern __________________147
6.6.2.2. Objektive Dateyse von MPEG-2 Bildrestspuren _________________149
6.6.2.3. Objektive Daten Analyse von Bildstillstand __________________________150
6.6.2.4. Objektive Untersuchung von Farbveränderungen______________________151
6.6.3. Fehlerhäufigkeit__________________________________________________152
6.6.4. Einschätzung von Benutzerverhalten__________________________________156
7. QoS Klassifikation ___________________________________________158
7.1. Vergleich von Verluststörungen _________________________________________158
7.2. Vergleich von Jitterstörungen162
7.3. QoS Klassifikationsmodell______________________________________________164
7.3.1. QoS Modell: Latenzdimension ______________________________________165
7.3.2. QoS Modell: Verlustdimension166
7.3.3. QoS Modell: Jitterdimension________________________________________170
8. Diskussion der Ergebnisse ____________________________________174

Zusammenfassung __________________________________________________178
Anhang ___________________________________________________________182
Glossar183
Abkürzungen ______________________________________________________184
Hardware _________________________________________________________187
Bibliographie188

viii
List of Figures

Fig. 1.1. Structure of a Video Signal ___________________________________________________14
Fig. 2.1. Protocol Stack for Video Data Transmissions ____________________________________16
Fig. 2.2. IP Switching Concept _______________________________________________________21
Fig. 2.3. IEEE 1394 Cycle Structure23
Fig. 2.4. Test Setup to Obtain Sample Sequences Based on Various “Lossy” Compression Formats _35
Fig. 2.5. Evaluation of the Overall Picture Quality of Different Compression Formats____________36
Fig. 2.7. Optimal Picture Quality with MPEG-2 [4:2:2] at 40 Mbps __________________________38
Fig. 2.8. Compression with MPEG-1 at 1.5 Mbps ________________________________________39
Fig. 2.9. Compression with MPEG-2 [4:2:0] at 4 Mbps39
®Fig. 3.1. Time Slot Assignment of TrueCircuit Technology_________________________________44
Fig. 4.1. End-to-end Delay for Multimedia Applications ___________________________________47
Fig. 4.2. Test Setup for Delay Measurements ____________________________________________48
Fig. 4.3. Topology of the G-WiN Core Nodes in November 2003 _____________________________55
Fig. 4.4. Collection of Active Measurements Across the G-WiN Network ______________________56
Fig. 4.5. Drifting of OWD Delays due to Time Synchronization Problems57
Fig. 4.6. Influence of Store-and Forward Delay __________________________________________57
Fig. 4.7. Periodic Loss Rates due to Missing ARP Entries __________________________________58
Fig. 4.8. One-Way Delay from Uni Erlangen to Uni Essen on November 12, 2003 _______________60
Fig. 4.9. Delay Variation from Uni Erlangen to Uni Essen on November 12, 200360
Fig. 4.10. G-WiN Measurements of Extreme Delays_______________________________________61
Fig. 4.11. Increase of Delay During Peak Times on June 10, 2003 ___________________________62
Fig. 4.12. Delay and Link Utilization __________________________________________________62
Fig. 4.13. Evenly Distributed Delays Independent of Network Loads__________________________64
(G-WiN / September 29, 2003) _______________________________________________________64
Fig.4.14. Peak Delay and Network Utilization (G-WiN / September 26, 2003) __________________65
Fig. 4.15. Test Setup for Delay and Jitter Measurements During a Videoconferencing Application
Across the G-WiN _________________________________________________________________67
Fig. 4.16. GPS-Based G-WiN Median Delays During the Videoconference_____________________68
Fig. 4.17. Oscilloscope-Based End-to-End Delays of the Videoconference68
Fig. 4.18. Gigabit Testbed South______________________________________________________69
Fig. 4.19. Test Configuration of Test 1 and 2 ____________________________________________70
Fig. 4.20. Test Configuration of Test 3 _________________________________________________71
Fig. 4.21. Test Configuration to Measure Cell Interarrival Times ____________________________72
Fig. 4.22. Cell Interarrival Time with 2 Traffic Streams at 97.35% Workload___________________73
Fig. 4.23. ATM Delay and Jitter Measurements __________________________________________74
Fig. 4.24. IP Measurements with “Qcheck” _____________________________________________75
Fig. 4.25. Traceroute Results for the Internet Connection __________________________________76
Fig. 5.1. Picture Differencing and Subjective Evaluation___________________________________79
Fig. 5.2. Mapping of MPEG-2 TS Packets Using the RTP/UDP/IP Protocol Stack _______________86
Fig. 5.3. Mapping of MPEG-2 TS Packets to AAL-1_______________________________________87
Fig. 5.4. MPEG-2 TS o AAL-588
Fig. 5.5. Delay Variation, Decoder Late Loss and Buffer Size _______________________________89
Fig. 5.6. Block Errors in MPEG Sequences91
Fig. 5.7. Variations of VBR Frame Sizes of a News and an Action Movie Video Segment __________96
Fig. 6.1. Video Source and Test Scene Selection_________________________________________101
Fig. 6.2. Typical Test Scenario Using Background Traffic _________________________________103
Fig. 6.3. Subjective Evaluations of Jitter and Loss Effects106
Fig. 6.4. Subjective Evaluations of Jitter Effects for Line Rates Below 100% __________________107
Fig. 6.5. Test Setup to Obtain Unimpaired Video Sequences _______________________________108
Fig. 6.6. MPEG-2 over ATM: Quality Perceptions Without Added Impairments ________________109
Fig. 6.7. Test Setup for Loss Impairments______________________________________________111
Fig. 6.8. MPEG-2 over ATM: Comparison of Loss Ratios112
Fig. 6.9. Typical Loss Errors for IF and IP-7 Encoded Video Clips__________________________114
Fig. 6.10. Test Setup for Subjective Evaluation of Jitter ___________________________________115
Fig. 6.11. Test Scenario for Jitter Measurements ________________________________________116
ix
Fig. 6.12. MPEG-2 over ATM: Jitter and MOS _________________________________________117
Fig. 6.13. MP IP: Quality Perceptions Without Impairments_______________________119
Fig. 6.14. MPEG-2 over IP: Generation of Loss Ratios ___________________________________121
Fig. 6.15. MPEG-2 over IP: MOS Ratings of Losses _____________________________________122
Fig. 6.16. MPEG-2 over IP: Jitter and Associated MOS Ratings ____________________________125
Fig. 6.17. MP IP: Priority and Non-Priority Traffic _____________________________125
Fig. 6.18. MPEG-2 over IP: Jitter Measurements _______________________________________126
Fig. 6.19. Typical Loss and Jitter Errors ______________________________________________127
Fig. 6.20. ATM Data Rate Based on Prototype AAL and RSE Error Recovery _________________129
Fig. 6.21. Continuous Bit Rate Traffic Independent of Video Content ________________________130
Fig. 6.22. Subjective Evaluation of Loss Ratios _________________________________________132
-1Fig. 6.23. SDI over ATM: Typical Loss Errors at a Loss Ratio of 10132
Fig. 6.24. Test Setup for SDI Jitter Measurements133
Fig. 6.25. Jitter Measurements for SDI over ATM Video __________________________________134
-2Fig. 6.26. Jitter and Loss Impacts on SDI over ATM Video (130 µs (jitter), 10 (loss)) __________135
Fig. 6.27. Quality Evaluation of SDI over IP Video without Impairments _____________________136
Fig. 6.28. MOS Scores for Various FEC Mechanisms with Loss Impairments__________________138
Fig. 6.29. Examples of Loss Effects on SDI over IP Video Clips ____________________________140
Fig. 6.30. Test Setup for Jitter Measurements of SDI over IP Sequences ______________________141
Fig. 6.31. Jitter Measurements and MOS Ratings for SDI over IP Video142
Fig. 6.32. Examples of MPEG-2 Block Errors __________________________________________144
Fig. 6.33. Subjective Error Characterization of Block Errors and Image Definition _____________144
Fig. 6.34. Subjective Characterization of Motion and Color Changes ___________________146
Fig. 6.35. Color Distortions for SDI Sequences _________________________________________146
Fig. 6.36. MPEG-2 Block Errors and Image Traces______________________________________148
Fig. 6.37. Examples of MPEG-2 Image Traces149
Fig. 6.38. Impact of Frozen Frames __________________________________________________150
Fig. 6.39. Color Changes and FEC Mechanisms ________________________________________152
Fig. 6.40. Editing of “bp”, “ext” and “bpext” Sequences _________________________________153
Fig. 6.41. Impact of Black Phases on Subjective Evaluations_______________________________154
Fig. 6.42. Mean Number of Frames between Error Periods________________________________155
Fig. 6.43. Comparison of Error Patterns ______________________________________________157
Fig. 7.1. Comparison of Loss Impacts on ATM Transmitted Video___________________________159
Fig. 7.2. Loss Impacts on IP Transmitted Video_____________________________160
Fig. 7.3. Comparison of Loss Impacts on MPEG-2 Encoded Video __________________________161
Fig. 7.4. Comparison of Loss Impacts on SDI Video _____________________________________162
Fig. 7.5. Comparison of Jitter Impacts on ATM Transmitted Video162
Fig. 7.6. Comparison pacts on IP Transmitted Video ____________________________163
Fig. 7.7. Comparison of Jitter Impacts on MPEG-2 Video _________________________________163
Fig. 7.8. Jitter Impacts on SDI Video164
Fig. 7.9. QoS Model: Delay and Compression Factor (= video transmission rate/video bit rate) ______165
Fig. 7.10. Loss Observations of Various Encoding and Transmission Modes __________________167
Fig. 7.11. MOS Defining Loss Ratios _________________________________________________168
Fig. 7.12(a). QoS Model: Loss Ratios vs. Compression Factor _____________________________169
Fig. 7.12(b). Loss Ratios vs. Compression Factor and MOS Categories ______________________170
Fig. 7.13. Jitter Observations of all Encoding and Transmission Modes170
Fig. 7.14. MOS Defining Jitter Intervals_______________________________________________171
Fig. 7.15(a). QoS Model: Jitter vs. Compression Factor __________________________________172
Fig. 7.15(b). Jitter vs. Compression Factor and MOS Categories ___________________________173
Fig. 7.16. Jitter Intervals vs. Loss Ratios and Resulting User QoP __________________________173
Fig. 8.1. Jitter Ranges Measured over G-WiN and GTB Networks176

x

Soyez le premier à déposer un commentaire !

17/1000 caractères maximum.