Video Telephony Services in EV-DO Systems

Transcription

1 Video Telephony Services in EV-DO Systems QUALCOMM, November 2006

2 Agenda - VT Overview 1. Introduction: VT Services 2. Packet Switched VT Advantages 3. Wireless VT Requirements EV-DO Full Rev A QoS VT Device: Performance Enhancing Techniques Core Network 4. Capacity Simulations 5. Summary 2

3 Introduction: VT Services 3

4 Hi Hi, look at how she s pretty Congratulations Corporate Technical Marketing Many applications derive from a regular VT (voice+video to voice+video) call VT Enabled Applications Instant Messaging with video Adding 1-way video into a VoIP call for a small duration Push-to-Chat with Video Video-Sharing OLD Push-to-Talk NEW Instant-MultiMedia Push-to-X 4

5 VT Usage Scenarios Teens Young Adults Families Consumer usage examples Sharing Emotions Social gatherings, babies' first steps, communicating w/ family while on travel See What I See Showing others what the caller is seeing Second opinion for shopping Nice view Potential house purchase Enhancing interaction Dating, adult services Business usage examples Video conferencing Journalism and reporting Insurance claims Remote healthcare Police work Security systems Visual proof of construction Visual proof of a signed contract or a new prototype Executives Field Force VT Enables a Complete Multimedia Communication Experience 5

6 VT Advantages for Operators VT is an appealing service that truly identifies 3G VT provides technology and service differentiation in the marketplace Although VT is not expected to replace regular voice communication, it will contribute to overall data ARPU increase Market research indicates that by 2010 there will be 150 million VT users and annual revenues will reach $9 billion* VT Provides Operators with Increased Data Revenue and Market Differentiation Opportunities ource: Strategic Analyst 6

7 Packet Switched Video Telephony Advantages 7

8 Packet-Switched VT Advantages (1) Migration of all services to IP networks Economies of scale and high volume cost curves Take advantage of IP network elements and IMS core network Easier integration with other packet based services, such as IM, LBS, etc Packet-Switched (PS) VT services are more spectrally efficient solution than Circuit-Switched (CS) Able to dynamically adapt rate to channel and loading conditions In PS network, channel rate adapts to physical/loading conditions on both FL and RL Encoder chooses rate to fit the channel, maintaining delay and error rate performance Able to deviate from fixed rate over short intervals reacting to image complexity, motion, and error event Less need to maintain per-packet fixed rate (rate control) More flexibility in handling I-frames/macroblocks Able to react to specific packet error events Intra-encoding can be based almost solely on actual error events, which are kept rare Allows reduction in open-loop updating of non-differentially encoded data (e.g. I-frames or I-macroblock update rate) This increases overall quality for the same transmission rate 8

9 Packet-Switched VT Advantages (2) CSVT Channel guarantees a fixed rate/packet size is transmitted at a fixed interval No matter what the actual channel conditions or loading Advantages Encoder knows exactly what rate is available PHY per-packet delay is fixed Admission control criterion well-defined Disadvantages In poor channels, PHY error rate can be high Rate control must be precise or incurs delay, leaving minimal flexibility to handle transient events No cross-layer feedback on actual transmission events Restricted use for end-to-end feedback, channel transmission and error rate is non-adaptive Overall network quality is hard to guarantee across network dynamics (handoff, mobility, channel quality, source variation), admission control must use backoff PSVT Channel adapts average/peak rate to conditions PHY PER is kept fixed Dynamic adaptation to current channel state and loading Advantages PHY PER is maintained, encoder can count on what is encoded being received Rate available on channel dynamically adapts to physical and loading conditions, efficient BW usage Soft tradeoff between admission control and user quality, capacity fills as possible Bursty xmit ability means rate control need not be precise, and I- frames/macroblocks can be quickly transmitted Local H-ARQ feedback allows for cross-layer per-packet success information End-to-end feedback used to fit encoding to end-to-end channel rate Disadvantages For best performance, encoder should adapt encoding to available rate at each frame, using local and end-to-end feedback But PSVT can always run in CSVT-like mode with open-loop encoder and circuit-like QoS allocation 9

10 PS VT Advantages (3) PSVT Application-Layer Control Loops Two levels of control RL control is based on immediate channel state and packet success measurements End-to-end control is based on slower feedback messaging (RTCP), but still fast enough to react to channel/loading dynamics and error events 10

11 PS VT Advantages (4) Rate of compressed video highly variable within a video stream For a given target video quality, bit rate vary based on image complexity, scene variability and video encoding parameters (e.g., I-frame interval) Example of a high variation source (MPEG-4 source, 7.5 fps, QCIF, fixed quality): 160 foreman 7.5fps QP12 GOP8 qcif 140 Moving Throughput Average TP (kbps) (kbps) I-Frames: 110 to 150kbps bursts P-Frames: 20 to 110kbps bursts 20 GOP Moving Moving-average Average Frame Instantaneous Moving-average Rate t (sec) PS Networks Better Adapt to Video Source Burstiness 11

12 PS VT Advantages (5) Video streams bit rates are source dependent Example of a source with low image variation (MPEG-4 source, 7.5 fps, QCIF, fixed quality) 100 akiyo 7.5fps QP12 GOP8 qcif 90 Moving Average TP (kbps) Throughput (kbps) I-Frames: Bursts close to 100kbps P-Frames: Bursts around 10kbps 10 GOP Moving Moving-average Average Frame Instantaneous Moving-average Rate t (sec) PS Networks Better Adapt to the Different Source Types 12

13 PS VT Advantages (6) CS VT video quality highly fluctuates as scene changes Video encoding rate targeted at fixed value (e.g., 48kbps) Video quality (PSNR*) degrades proportionally to image variability 35 Video Quality Fluctuation for Foreman Test Sequence 60 Average Bit Rate Fluctuion for Foreman Test Sequence Video Quality in PSNR (db) ~10dB quality variation Average Bit Rate (Kbps) 50 48Kbps Time (second) Time (second) SNR is a metric to easure video quality CS VT Results in Variable Video Quality and Under-Utilization Utilization of Channel Capacity 13

14 PS VT Advantages (7) PS VT sustains video quality by variable encoding rate PS networks have the flexibility of allocating resources on demand Video encoders can generate higher data bursts and the PS network is able to serve them appropriately without introducing delays 35 Video Quality Fluctuation for Foreman Test Sequence 160 Average foreman Bit Rate Fluctuation 7.5fps QP12 for Foreman GOP8 Test qcif Sequence 140 Video Quality in PSNR (db) ~3dB quality variation Average Bit Rate (Kbps) Time (second) Frame Moving-average Time (second) PS VT Enables Consistent User Experience While Optimizing Network Resources 14

15 PS VT Advantages (8) PS VT allows balancing available bandwidth and video quality Tradeoff between available network resources and video quality Video quality may be adjusted based on available user throughput Operators may decide at which maximum and minimum quality levels to provide service PSNR (db) foreman 10AT GOP=8 fps=7.5throughput v.s. PSNR mtp (kbps) Average Throughput (kbps) PS VT is a Flexible Solution Enabling the Tradeoff Between Quality, Resource Availability and Capacity 15

16 Wireless VT Architecture 16

17 Video Telephony (VT) Traffic Characteristics Video Telephony service provides a real-time full duplex audio and video communication solution VT service generates three distinct traffic flows: Control flow Low data rate, low delay and reliable delivery Audio flow Low data rate delay / jitter sensitive and higher priority than video, can tolerate minimal loss Video flow Medium data rate, bursty, delay / jitter sensitive and lower priority than audio, can tolerate some loss Encoding rate is proportional to the video quality (resolution and frame rate) A wireless Packet Switched VT solution needs to sustain adequate QoS levels for the three traffic flows 17

18 Wireless PSVT Architecture 1. EV-DO Rev A QoS Network 2. VT enabled devices EV-DO Rev A, IMS/SIP capable with appropriate VT software 3. Core Network SIP Servers or IMS core for registration and call setup AAA SIP Servers / IMS BTS BSC / PCF PDSN Internet QoS Domain 18

19 Related 3GPP2 Specs PSVT relies on several 3GPP2 documents Number Main Features for PSVT Comments Published IS-856-A EV-DO Rev A Highly recommended 1Q04 IS-835-D QoS Procedures Highly recommended 1Q06 TIA-878-A QoS Procedures - A interface, CSNA Highly recommended 1Q06 A.S0008-B/C Cross-connectivity, inter-an HO, no- PPP encapsulation Optional 3Q06/1Q07* TIA EMFPA, RoHC and no-ppp encapsulation negotiation Optional VT may be implemented with MFPA and without header compression 1Q05 C.S Codecs, error resiliency, compression, IMS call flows, supplemental services Optional features may be implemented before standard publication 4Q06* C.S0055-A Adaptive Rate adaptation, others being defined Optional features may be implemented before standard publication 3Q07* X.R VoIP and PSVT End to End System Design Technical Report Guideline document for VoIP and VT implementations 2Q06 TIA-873 (X) IMS general specs Optional PSVT may be deployed without IMS * Estimated publication date 19

20 VT Over EV-DO Full Rev A QoS 20

21 VT over Full Rev A QoS Rev A increased RL capacity efficiently supports VT services Due to more symmetric FL and RL, Rev A better accommodates VT traffic Rev A enhanced features allow high VT performance Lower packet latency Better differentiation of RL traffic flows (Enhanced) Multi-Flow RLP Optimized handoffs Related standard revisions introduce end-to-end QoS negotiation, optional header compression, precise accounting and authorization features e.g., IS-835-D and TIA-878-A Full Rev A QoS Networks Support VT at High Performance and Efficiency Levels Full Rev A QoS RAN QoS Features & Rev A Air Interface Software Features Rev A (CSM6800) MSM 6800 MSM

22 Rev A Performance Improvements Rev A key air interface features provide optimized performance and efficiency to support VT Multi-user packets Smaller packets New DRC definitions Reduce delays and PER and improve packing efficiency for VT packets Reverse Link Hybrid ARQ Data Source Control (DSC) channel Early indication of cell switching minimizes service outage for VT flows Improved access channel Faster rate optimizes connection set up time 22

23 Rev A RL Improvements RL MAC Subtype 3 enables meeting strict QoS requirements on the RL Multiple RL MAC flows Device may map multiple link flows to multiple RL MAC flows that correspond to QoS priority levels May control individual VT RL MAC flows Traffic-to-pilot (T2P) is used as an indicator of sector resource usage Provides finer control of individual flows Better serve high data bursts from video source DEVICE IP Packet VT - Audio Flow 1 VT - Video. Flow 2 Flow n VT - Control RL MAC 1 RL MAC 2. RL MAC n 23

24 Multi Flow Air Interface and QoS Profiles (Enhanced) Multi-Flow RLP Enable separation of audio, video and control on different link flows QoS Profiles 1 are introduced and associated to link flows Implicitly specifies delay, throughput, jitter requirements for each flow QoS Scheduler BTS QoS scheduler prioritizes packets on FL according to link flow QoS profile Audio Link Flow Video Link Flow Control Link Flow HTTP Link Flow (BE) HTTP Link Flow (BE) SMTP Link Flow (BE) QoS Scheduler at BTS RAN QoS Profile Examples 1 : 1. Real-time Voice 2. Real-time video 3. Video-Streaming 4. Best-Effort 5. other QoS FlowProfileIDs are specified in 3GPP2 C.R1001 RevE 24

25 QoS Negotiation and Setup Rev A enables IP flow QoS negotiation at application launch and QoS activation when call initiated Allow minimal setup delays while consuming no resources until activation 1 Power Up Open EV-DO session RAN 2 3 VT app starts Call initiated Reservation request for audio, video and control Link Flows and RTCMAC Configuration QoS Activation 25

26 Admission Control Admission Control verifies the availability of airlink resources at the time a VT flow is activated RAN admits or rejects new VT calls based on performance bounds required by VT flows and FL/RL loading information Ensures number of connected VT users will not grow and affect quality of existing VT calls Activate VT Connection RAN Accepts / Rejects 26

27 Standards Revision (1) IS-835-D and TIA-878-A introduce key features for QoS and VT implementation Support for multiple A10s per user QoS IP flows are mapped to separate A10 connections. A10 connections are matched to respective Link Flows Enable accurate QoS Accounting and improved Authorization process User is authorized for individual QoS profiles. AAA provides allowed QoS profiles RAN signals when QoS link flow is activated. Allows precise billing based on call duration or MB Audio Link Flow Audio A10 connection Video Link Flow Control Link Flow RAN Video A10 connection Control A10 connection PDSN QoS profile authorization Indication of flow activation AAA 27

28 Standards Revision (2) IS-835-D and TIA-878-A enable QoS Profiles to be included in UDR (Usage Data Record) sent to AAA Charge according to duration of media interaction or based on regular MByte volume AAA RAN QoS Profiles PDSN Includes QoS Profile in UDRs Operators have precise information on duration of QoS services and amount of data exchanged Example: VoIP conversation that includes video during a portion of the time 28

29 Overall VT Call Procedures 1. Device power up: Radio session establishment PPP establishment 2. VT application launch QoS configuration AT sends traffic flow s QoS requirements to RAN which sets up and configure air interface parameters PDSN and RAN establish A10 connections for each flow AT sends Resv message to PDSN with IP packet filters SIP registration Audio Link Flow 3. VT call origination QoS activation SIP call setup 4. Call Duration IP packets that match packet filters in PDSN are directed to the configured VT A10 connections on FL Device applies appropriate RTCMAC treatment to each traffic flow 5. VoIP call release SIP call release QoS deactivation Audio A10 connection IP Packet Filters: -audio -video -control Video Link Flow Control Link Flow RAN Video A10 connection Control A10 connection PDSN QoS negotiation at application startup 29

30 Media Header Compression RoHC is an efficient compression method to reduce packet overhead Critical for VoIP services Although desirable for VT media flows, initial services may not utilize it RoHC negotiation enabled by Enhanced Multi Flow Packet Application (EMFPA) Voice Frame Bundling VoIP Header to Total BW Ratio VT Header to Total BW Ratio* No Comp. 72% 21% RoHC 11% 5% Increases efficiency if RoHC not implemented, however: Incurs in higher delays and correlated errors Not compatible w/ VoIP design Two IP packets per video frame 30

31 VT Device Enhancing Features 31

32 VT Devices: Qvideophone Qvideophone enables VT services using EV-DO MSMs Simpler and lower cost solution Implemented on MSM6800 and MSM7500 Video File Format: MPEG-4 and H.263 Audio File Format: EVRC and AMR-NB Performance: up to QCIF Protocols: SIP RFC SIP: Session Initiation Protocol RFC SDP: Session Description Protoco RFC An Offer/Answer Model with SDP 32

33 VT Enhancing Features Dynamic Loss Recovery CS Service Notification Rate Adaptation Advanced codecs In-call media management (e.g., video-sharing) PS Optimized Features Media/Signaling Compression 33

34 Error Resiliency: Packet Loss Feedback C.S introduces Packet Loss Feedback feature Receiver sends RTCP message reporting video packet losses Benefits Mitigates propagation of errors in video decoding Minimizes generation of unnecessary I-frames reducing BW required for VT Wireless Network Packet X Loss RTCP Message Indicating Packet Loss Packet Loss Feedback Improves Video Quality and Optimizes Systems Resources 34

35 Loss Feedback Improves VT Solution No Packet Lost Feedback I-frames generated periodically (GOP structure) Error propagation until next I-frame received Packet Lost Feedback I-frames adaptively generated optimizing link efficiency* (do not need to rely on GOP structure for I-frames) * Other actions may be taken to stop error propagation Error propagation limited to one round-trip! 35

36 PSNR PSNR is a video quality metric Comparison between the original clip and reconstructed one Sample videos at QCIF, fps=7.5 PSNR= 30.1dB PSNR= 36.4dB PSNR = 10log 10 (255 2 /MSE) MSE: mean-squared-error between original clip and reconstructed one PSNR= 26.91dB Original clip 36

37 Packet Loss Feedback Performance Results Results for Foreman Clip*: Avg PSNR [db] Quality Fluctuation STD PSNR [db] Degraded Video Duration pdvd [%]** Clean NA No Feedback (I-frame every 100 frames) No Feedback (I-frame every 50 frames) With Feedback Lower quality fluctuation - important for human visual system perception Significant reduction of degraded video duration One round trip time (RTT) delay 500 msec; One video frame per RTP packet; FER of 1.5% *e.g. Percentage of time with >1dB degradation 37

38 Qvideophone Instant Loss Recovery In addition to end-to-end packet loss feedback, RL PHY layer packet loss information is used by the encoder to improve performance Sender generates I-frame to stop the propagation of errors at the receiver No standards impact supported by Qvideophone 38

39 End-to-End Video Encoding Rate Adaptation C.S0055-A proposes End-to-End Rate Adaptation feature* E2E signaling to maintain video packet delay within defined range If delay is out of target interval, receiving end-point requests sender to adjust encoding Feedback information sent over RTCP Wireless Network Delayed Packets RTCP Message Packet Delay Adjust Request E2E= End-to-End *Considering advancing it to C.S Frame Delay T2 T1 Decrease Quality No Quality Change Increase Quality 39

40 Rate Adaptation and Delay Results for Forman clip (8 ATs per sector - total of 456 users, 7.5 fps) Without rate adaptation average delays vary significantly ( ms) Rate adaptation keeps majority of users with under 350ms average delays Distribution of Average E2E Frame Delay 40

41 Qvideophone Instant Rate Adaptation In addition to E2E rate adaptation, current RLMAC information is used to optimize video delivery Video stream encoding rate adjusted to the best quality supported by Rev A network Example: AT moving to the cell edge may be power limited and may not able to sustain target video bit rate. Thus, bit rate is adjusted to the best quality that can still be transported in a timely fashion No standards impact - supported in QVideophone QUALCOMM Proprietary 41

42 Video-Telephony Capacity Simulations 42

43 Simulation Setup Layout 57 EV-DO Rev A Sectors with wrap-around 8/10/12 ATs per Sector Same link budget as standard 1x footprint CellHoneyComb19, 10AT per sector, slots y (km) x (km) 43

44 Simulation Assumptions All EV-DO Rev A terminals have dual receive diversity Packets are simulated from source to destination including network constant delays (packet processing, codec, etc). De-jitter buffer delay not included Rev A parameters 12-slot termination target for audio and video flows on the RL D-ARQ on FL RLP retransmissions disabled on FL and RL Adaptive RL resource allocation (based on RAB) Audio Fixed allocation is also possible for equal-gos. However it requires a stringent admission control algorithm MSO model RoHC no packet bundling Video Video sequence: foreman (aggressive source, since it has high variability) at random starting point for each AT MPEG-4 codec with simple profile QCIF, 7.5fps, 1 I-frame per second Adaptive encoding rate based on end-to-end delay and RL delay 44

45 Video Delay with Rate Adaption (E2E Delay) All video packets experience delays lower than the 400ms threshold With 12 ATs per sector, some users have a slightly higher end-to-end delay, but still within the allowable range for a good user experience Percent of video frames AT 10 AT 12 AT E2E Delay (ms) 45

46 Video Delay: No E2E Feedback Distribution of Average E2E I Frame Delay No adaptive rate control: High avg. delay variance and many users experience large E2E delays 46

47 Video Quality with E2E Feedback For 8 ATs per sector, high quality video is achieved by majority of users More calls per sector introduce modest quality degradation An average quality level of 26.3dB PSNR or higher is achieved by: 77% of users in 12 ATs scenario 90% of users in 10 ATs scenario 95% of users in 8 ATs scenario Even at 12 ATs per sector, performance of 24.4dB or better is achieved by 95% of the users CDF AT 10 AT 12 AT PSNR (db) 47

48 Video Quality: No E2E Feedback Cumulative Distribution Function of PSNR No adaptive rate control: Majority of users experience lower than 25dB PSNR In 12 AT scenario, 80% have less 18dB PSNR For packets that do not arrive in time for playout, most recent decodable frame is displayed instead of delayed frame 48

49 Comparison of Path Loss vs. Received PSNR Video quality is sustained throughout the cell coverage area A small number of users experience higher degradation at cell edge Application may remove video flow and continue with voice only PSNR (db) AT 10 AT 12 AT Path loss (db) 49

50 Rise-Over-Thermal ROT is within safe range of operation 10 0 CellHoneyComb19, 24AT, slots 8 AT 10 AT 12 AT 10-1 ccdf ROT (db) 50

51 Summary 51

52 EV-DO VT Solution Summary Packet Switched VT over EV-DO results in higher efficiency and flexibility Full Rev A QoS provides the required features for highquality wireless PSVT performance Enhanced device features such as adaptive encoding rate and packet loss feedback optimize PSVT solution Simulations show sector capacity of 8 simultaneous VT calls for enhanced quality Additional simultaneous calls with modest quality degradation New features such as RL Interference Cancellation and 4-way BTS receive diversity provide additional RL capacity and higher efficiency 52