Coded Wireless Video Broadcast / Multicast: A Cross-layer Framework With Protections To Harvest The True Potential of 4G Access Networks James She, Ph.D. Research Fellow, Computer Laboratory Presentation @ The Chinese University of Hong Kong, Hong Kong – Jan 2011 1 Outline 1. Introduction & Background 2. A Preliminary Cross-layer Design 3. Coded Wireless Video Broadcast/Multicast 4. An Information-theoretical Bound of Expected Distortion 5. Conclusion & Future Work 2 4G/Broadband Wireless Access and 1-to-many/all Video Applications Wireless Broadcast/Multicast and Problems In a single-hop wireless network: • efficient use of spectrum • higher system scalability 1. Multi-user channel diversity: Rate is limited to receiver with the worst channel low video quality 2. Error Control: Retransmission Not efficient or scalable 4 Research Objectives Limitations of Existing Cross Layer Designs (CLDs): 1. Many for unicast are not applicable 2. Some for multicast/broadcast using erasure/network codings: – Some statistical number of receivers within a multi/broadcast group – Multi-hop wired/wireless infrastructure Research Objectives: 1. Practical and generic cross-layer frameworks (advanced source + channel coding) for single-hop network 2. Fundamental understanding of the proposed frameworks, using information theory 3. Possible implementations 5 Outline 1. Introduction & Background 2. A Preliminary Cross-layer Design 3. Coded Wireless Video Broadcast/Multicast 4. An Information-theoretical Bound of Expected Distortion 5. Conclusion & Future Work 6 A preliminary cross-layer design - Superposition Coded Multicast Scalable Video Source (MPEG4/ H.264AVC): Bitstream with successive refinable layers Layered Channel (Superposition coding): Multi-resolution modulated (layered) broadcast signals e.g., 2 layered video data (basic + enh. qualities) layer 1 (BPSK) layer 2 (QPSK) layered broadcast signal Encoding: superimpose two modulated signals (i.e., vector additions: x1 + x2 x ) … … … … … Decoding, y: 1. decode the lower order signal (BPSK), y1, from received signal, y 2. substract it from y for decoding y2.(QPSK) (i.e., y - y1 y2.) 7 Superposition Coded Multicast (SCM) Base station 2 quality layers (base & enhancement) Receiver(s) Novelty: exploits the layered properties in scalable source and multi-resolution channel BS only broadcasts/multicasts a single type of radio signals that contains all layers decodable by receivers at various channel levels for multiple rate of video delivery. Simulation Results Compare achievable video qualities (PSNR): • Normal Multicast vs. SCM PS: ‘Normal’ uses the rate everyone supports poor receiver (low SNR avg.) good receiver (high SNR avg.) Conclusion: Higher video quality regardless of the avg. channel SNR of a receiver! 9 SCM Summary Two critical components identified: 1. Scalable video (source) 2. Multi-resolution modulation (channel) Resolved multi-user channel diversity + video quality improvement. An limitaiton: • Video quality fluctuates with channel condition at a receiver regardless of the SNR avg. Error control problem! 10 Outline 1. Introduction & Background 2. A Preliminary Cross-layer Design 3. Coded Wireless Video Broadcast/Multicast 4. An Information-theoretical Bound of Distortion Bound 5. Conclusion & Future Works 11 Proposed - Coded Wireless Video Broadcast/Multicast Deal with error control & multi-user channel diversity: Introduced protections to each successive layer at the source Achievable by modifying the Multiple Description Coding based on Reed Solomon RS(N, K) [18] Note: For any layer l, a smaller Kl value, the higher robustness to tolerate fading duration for that layer. Each MDC/protected packet (with multiple layers of bitstreams) is sent through SCM as a multi-resolution modulated signal [18] P. A. Chou, H. J. Wang, and V. N. Padmanabhan, “Layered multiple description coding,” Proc. PV 13th Int. Packet Video Workshop, Nantes, France, Apr. 2003. 12 System Model And Error Control Advantages App. layer 3 Video in Scalable Video Encoder MAC layer 1 PHY layer Superposition Modulation Scalabe bitstream 2 BPSK modulated analog forms layer 1 buffer Multicast Scalable Error Controls: addressed Coded Wireless Video Broadcast/ + Receiver recovers its own lost bitstreams of layer l when successfully superposed Multicast signals Multicast analog forms received any Kl “partial” MDClayerpackets of layer l. 2 buffer addressed 16QAM modulated analog forms Wireless Channel Protection Coder e.g. Reed-Solomon 4 5 layer 1 buffer Demodulated base layer data Superposition Demodulation + layer 2 buffer Video Decoder Demodulated enhancement layer data Coded Wireless Video Broadcast/ Multicast signals superposed analog forms Video out 13 A Quick Video (00:00:51-00:02:05) Formulations For Analysis Performance/video quality measurement: Total received/recovered bitstreams, Tm, of a GoF by a receiver m. • Prob. of receiving/recovering a layer l by receiver m (i.e., receiving at least Kl partial packets of layer l by receiver m) N N K j N j j l ( P l o s s ( S N R ) ) ( 1 l o s s ( S N R ) ) l , m l , m l , m j 0 •With the layers dependency, the amount of received/ recovered bitstreams of a layer l in a GoF: layer l l P T ( bb ) i , m l , m l l 1i 1 Total received/recovered bitstream of a GoF: L T T, m l 1 lm 15 Optimized & Experimental Results Compare layered broadcast w/o protection (e.g., SCM) and the proposed one: • 2 layers w/ optimized (searched) parameters • 2 different standard video sequences (Foreman and Paris) Note: SS-1: lowest SNR avg. SS-10: highest SNR avg. SS-1 (Foreman) Coded Wireless Video Broadcast/Multicast • better video quality even in a poorer channel • smaller quality difference between receivers with highest and lowest SNR avg. 16 poor receiver Layered source+channel (SCM) Layered source+channel with protection good receiver Summary Novelties: 1. Introduced protections on successive layers over layered broadcast 2. Utilized partial MDC (protected) packets (never discussed in wired infrastructure) 3. Modified existing MDC for practical implementation 4. An analytical model for analysis and optimization. Resolved both multi-user channel diversity and error control problems which are not possible in all previous and recent works [1-4] [1] Chris T. K. Ng et al., “Recursive Power Allocation in Gaussian Layered Broadcast Coding with Successive Refinement,” IEEE Intl. Conf. on Comm. (ICC), Jun 24–27, 2007, Glasgow, Scotland, pp. 889–896. [2] C. Tian et al., “Successive Refinement Via Broadcast: Optimizing Expected Distortion of a Gaussian Source Over a Gaussian Fading Channel”, IEEE Trans. on Information Theory, vol. 54, no 7, pp.2903-2918, Jul. 2008. [3] Y. S. Chan et al., “An End-to-End Embedded Approach for Multicast/Broadcast of Scalable Video over Multiuser CDMA Wireless Networks”, IEEE Trans. on Multimedia, vol. 9, no. 3, pp. 655-667, Apr. 2007. [4] Murali R. Chari et al., “FLO Physical Layer: An Overview”, IEEE Trans. on Broadcasting, vol. 53, no. 3, pp. 145-160, Mar. 2007 18 Outline 1. Introduction & Background 2. A Preliminary Cross-layer Design 3. Coded Wireless Video Broadcast/Multicast 4. An Information-theoretical Bound of Expected Distortion 5. Conclusion & Future Works 19 Informaton-theoretical Bound of Expected Distortion Did you realize that we send less video data? Costs of protections If / when the proposed framework is better than a similar layered broadcast WITHOUT protections? The expected distortion without layers [3] : where each source symbol is sent by a channel symbol under symbol error, perr. Assume a successive refinable source with Gaussian distribution (i.e., L layers in each source symbol, S) Apply a generic (n, kl) protection code in a layer l: i.e. A source symbol, S n protected layered source symbol, Vi , where i=1,..., n. Recall: smaller kl value for layer l, more robustness, but less effective data sent [3] X. Yu and En-hui Yang, “Optimal quantization for noisy channels with random index assignment", Proc. of the 2008 IEEE Intern. Symp. Inform. Theory, Toronto, Canada, July 6-11, 2008. 20 Bound of Expected Distortion protected layered source symbols, Vi x(i) Each Vi a layered channel symbol, x(i), for each coded broad/multicast transmission: A receiver collects n channel symbols, x(1), ... ..., x(n) over n channel symbol durations. Each x(i) is decoded into Vi ~ up to layer l with prob. pl upon the receiver`s instantaneous channel condition. 21 Bound of Expected Distortion After n channel symbol durations (or n transmissions), kL kl k1 V1 ... ... Vn The Bound of Expected Distortion: l k 1 l i n k R j n j j j j 1 2 1 1 p p M , i M , i j L 0 i 1 j D p l k 1 l i l 1 n j n j 2 1 1 1 p p , i M , i M l j j 0 i 1 Applicable to a system without protection (i.e., kl =n) The discreteness (i.e., binomial CDF terms) can be approximated by a normal CDF to determine optimal k values for optimization. 22 Numerical Anylysis -1 Fixed symbol error at layer 2 (a) higher pM,1 (k1*=5, k2*=2) (b) lower pM,1 (k1*=14, k2*=2) Fixed symbol error at layer 1 (a)higher pM,2 (k1*=18, k2*=1) (b) lower pM,2 (k1*=18, k2*=3) 23 Numerical Anlysis - 2 Expected distortions of two systems (with and without protections) under various pM,1 in layer 1 and pM,2 in layer 2. Simulation Comparisons Layered broadcast without and with protections under optimized parameters: Fixed lower, pM,2, in layer 2 Fixed higher, pM,2, in layer 2 Systems with their optimized configurations . 25 Summary of Expected Distortion Novelties: A general closed-form formula for the bound of expected distortion Generic to any (n, k) protection code and any number of layers (source/channel), useful for a new coding design More accurate analysis/optimization, instead of using simply using throughput/bitstream amount. Outline 1. Introduction & Background 2. A Preliminary Cross-layer Design 3. Coded Wireless Video Broadcast/Multicast 4. An Information-theoretical Bound of Expected Distortion 5. Conclusion & Future Works 27 Contributions 1st framework using protections for tackling multi-user diversity and error control. 1st realization through existing codings, as well as the associated analytical and optimization models. 1st information-theoretical distortion bound for comparisons, and optimization through a simple search. Advanced the fields by introducing a new design dimension – protections, for cross-layer designs that was unapparent in the past literature. LESS is MORE sometimes! 28 Future Work Extend into cooperative communications under multi-BSs wireless networks (e.g., optical-wireless hybrid network) by considering space-time coding Promising results from preliminary investigations in EPON-WiMAX access networks Final Remark: a cross-layer design with protections is shown to be useful in cooperative networks for better video broadcast/multicast 29 On-gogin Research and Industrial Collaborations • WiMAX/LTE BS system and cooperative broadcasting networks (prototype and research) (Taiwan) (Italy) Electrical & Computer Engineering • SPC chipset and software-defined radio platform (research) • New scalable source coding with protection (research) (Saudi Arabia) Electrical & Computer Engineering (Ottawa) • WiFi platform (prototype) • Coded MIMO Broadcast/Multicast (research) Electrical & Electronic Engineering Acknowledgement Prof. Pin-Han Ho, University of Waterloo Prof. En-hui Yang, University of Waterloo Dr. Xiang Yu, Research-In-Motion Sponsors: IPMG Collaborators: 31 Collaborations and students 1. Looking for like-minded researchers and organizations/industries for collaborations and funs! 2. Looking for smart, creative and entrepreneurial students to join me as my research interns. Email: james.she@cl.cam.ac.uk Web: http://www.cl.cam.ac.uk/~js864 32 The End THANK YOU 33 Selected Publication From This Research SCM: [1] J. She, et al., “IPTV over WiMAX: Key Success Factors, Challenges and Solutions”, IEEE Communications Magazine, vol. 45, no. 8, pp.87-93, Aug. 2007. (Top 50 most accessed article in IEEE Xplore 2008, and cited in Wikipedia under MobileTV) Coded Wireless Video Broadcast/Multicast: [2] J. She, et al., “A Cross-Layer Design Framework for Robust IPTV Services over IEEE 802.16 Networks”, IEEE Journal of Selected Areas on Communications (JSAC), vol. 27, no. 2, Feb. 2009, pp. 235-245. [3] J. She, et al., “A Framework of Cross-Layer Superposition Coded Multicast for Robust IPTV Services over WiMAX”, Proceedings of the IEEE Wireless Communication and Networking Conference, pp. 3139-3144, Mar. 2008, Las Vegas, Nevada, USA. (Nominated for the Best Student Paper Award) Expected Distortion Comparison: [4] J. She, et al., “Distortion Comparisons For Protected Successive Refined Over Broadcast Channel ”, submitted to Trans. Multimedia, Jul. 2010. L-SPC: [5] J. She, et al., “Logical Superposition Coded Modulation”, submitted to Trans. Wireless Communication, Nov. 2010. 34