Energy-Efficient Video Multicast in 4G Wireless Systems Ya-Ju Yu 1, Pi-Cheng Hsiu 2,3, and Ai-Chun Pang 1,4 1 Graduate Institute of Networking and Multimedia, National Taiwan University 2 Research Center for Information Technology Innovation, Academia Sinica 3 Institute of Information Science, Academia Sinica 4 Department of Computer Science and Information Engineering, National Taiwan University IEEE Transactions on Mobile Computing. DOI: /TMC

Outline Introduction –Fourth generation wireless networks/ Video coding/ OFDMA System Model and Problem Definition The proposed Multicast Algorithm –Algorithm 1 (for SVC video coding) –Algorithm 2 (for MDC video coding) Simulations Conclusion

Introduction Advances in wireless communications have increased the popularity of mobile devices and motivated the development of various mobile applications and services. Fourth-generation wireless systems (WiMAX and LTE) –Video multicast services IPTV, Video conferencing, etc. –Energy Saving Mobility support

Introduction The high-speed multicast services can be the services of IPTV, video conferencing, and so on. –According to the audiovisual spec., the original video can be converted into different files with different resolution. –Scalable video coding (SVC) –Multiple description coding (MDC)

Introduction Scalable video coding (SVC) Data Rate requirement Base Layer Enhancement Layer 1 Base Layer Enhancement Layers 1 Base Layer Enhancement Layers 2

Introduction Multiple description coding (MDC) Section 1Section 2…Section i…Section N-1Section N i.(1)i.(2)i.(3)i.(4)…

Introduction An OFDMA frame consists of symbols in the time domain and subchannels in the frequency domain. Preamble FCH DL-MAP Sub-channel Logical Number OFDMA symbols tile

Introduction Example of resource allocation related to energy consumption

System model and problem definition S: Number of available symbols (1  s  S) C: Number of available subchannels (1  c  C) M: Number of possible modulation-coding schemes (1  m  M) m-modulation user –the highest rate modulation that the user can receive G: Number of multicast groups (1  g  G) N g : Number of users in group g N g : Number of m-modulation users in group g

System model and problem definition L g : Number of video layers for group g λ(g,l): the application rate of each layer l : Application rate required by an m-modulation user in group g : Application rate received by an m-modulation user in group g γ m : Application rate carried by a single tile with modulation m : Number of tiles required to transmit layer l for group g with modulation m

System model and problem definition : An indicator function –1, if layer l for group g is transmitted with modulation m. –0, otherwise : An indicator function –1, if layer l for group g is transmitted with modulation m in the tile comprised of symbol s and subchannel c. –0, otherwise

System model and problem definition Resource constraints –The number of allocated tiles cannot exceed the available symbols –The number of allocated tiles cannot exceed the available subchannels

System model and problem definition Modulation constraints –The number of tiles allocated to a layer with any modulation must not be less than the layer needs –A video layer for any group can be modulated with at most one modulation.

System model and problem definition Requirement constraints –Each user must be satisfied with the application rate it receives. –To avoid unsolvable or trivial situations, this paper assumes that

System model and problem definition Dependence constraints –In SVC, the decoding of an enhancement layer depends on its lower layers –If layer l is selected to transmit with modulation m, every layer lower than l must be selected to transmit with a modulation i  m

System model and problem definition Objective to the Energy-efficient layer-coded video multicast problem –Minimize the total energy consumption (number of symbols) of all users to receive the requested video data

The proposed algorithm Algorithm 1 (for SVC): –Energy-Efficient Scalable Video Multicast Algorithm 2 (for MDC): –Energy-Efficient Multiple Description Video Multicast

Algorithm 1 (for SVC)

Stage 1 of algorithm 1 determines –which video layers for each group should be transmitted with which modulations in order to satisfy the application rate requirements of all users. Group 1 Layer 1 for (U1, U2) with modulation 1 Layer 2 for (U1, U2) with modulation 1 Layer 3 for (U1, U2) with modulation 1 Layer 4 for (U2) with modulation 2

Algorithm 1 (for SVC) Stage 2 of algorithm 1 determines –Resource allocation for minimizing the number of symbols Group 1 Layer 1 for (U1, U2) with modulation 1 Layer 2 for (U1, U2) with modulation 1 Layer 3 for (U1, U2) with modulation 1 Layer 4 for (U2) with modulation 2

Algorithm 2 (for MDC)

Fill-Table –Modulation 1 –r: remaining requirements

Algorithm 2 (for MDC) Back-Trace –Modulation 1 –r: remaining requirements

Algorithm 2 (for MDC) Fill-Table and Back-Trace –For each modulation m Resource allocation –As the Stage 2 of Algorithm 1

Simulation Setup C++

Simulation Setup Modulations Compared with –OPT: Brute-force –CONV: Randomly allocates tiles to layers

Simulation

Simulation Setup Modulations and user distributions

Simulation

Conclusion This paper proposed energy-efficient multicasting algorithm to minimize the total energy consumption (i.e., the number of the symbols received for users) –SVC: scalable video coding –MDC: multiple description coding TheEND Thanks for your attention !