Energy-Efficient Video Multicast in 4G Wireless Systems

Ya-Ju Yu1, Pi-Cheng Hsiu2,3, and Ai-Chun Pang1,4

1 Graduate Institute of Networking and Multimedia, National Taiwan University2 Research Center for Information Technology Innovation, Academia Sinica

3 Institute of Information Science, Academia Sinica4 Department of Computer Science and Information Engineering, National Taiwan University

IEEE Transactions on Mobile Computing. DOI: 10.1109/TMC.2011.186

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 Raterequirement

Base Layer

Enhancement Layer 1

Base Layer

Enhancement Layers 1

Base Layer

Enhancement Layers 2

Introduction

• Multiple description coding (MDC)

Section 1 Section 2 … Section i … Section N-1 Section 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.

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2

3

4

5

6

7

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al N

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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)

• Ng: Number of users in group g

• Ng: Number of m-modulation users in group ggmN

System model and problem definition

• Lg: 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

• γm: Application rate carried by a single tile with modulation m

• : Number of tiles required to transmit layer l for group g with modulation m

gmR

gm

( , )g lmt

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

( , )g lm

( , )( , , )

g lm s c

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)

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.

( , )g lm

Group 1Layer 1 for (U1, U2) with modulation 1Layer 2 for (U1, U2) with modulation 1Layer 3 for (U1, U2) with modulation 1Layer 4 for (U2) with modulation 2

Algorithm 1 (for SVC)

• Stage 2 of algorithm 1 determines– Resource allocation for minimizing the number of symbols

( , )( , , )

g lm s c

Group 1Layer 1 for (U1, U2) with modulation 1Layer 2 for (U1, U2) with modulation 1Layer 3 for (U1, U2) with modulation 1Layer 4 for (U2) with modulation 2

Algorithm 2 (for MDC)

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

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

TheENDThanks for your attention !