Low-Delay Video Communication System over Wireless Channels Based on HEVC and OFDM

Produktbeschreibung

This thesis provides an analysis of the entire video communication system assuming a wireless, frequency- and time-selective channel under low-delay constraints. The whole system consists of a standard-compliant video codec (HEVC), a channel codec and a modem (OFDM). A design methodology in terms of the rate-distortion optimization and a suitable framework to asses the entire system is proposed. It has synchronization capabilities and a suitable metric that turns out to be a key component of the rate-distortion based optimization procedure.

The trade-offs and interrelations of the parameters that have the most significant impact in the total distortion and robustness of the video signal are investigated. By means of intensive and sufficient simulations of an entire video transmission chain, it has been shown that the multiple techniques introduced and described in this thesis are viable tools for the design and optimization of specific video communication systems and its components.

C O N T E N T S
1 introduction 1
1.1 Basics of Video Communication Systems . . . . . . . . . . 1
1.2 Challenges . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2.1 Shannon’s Separation Principle . . . . . . . . . . . 3
1.2.2 System Design Parameters . . . . . . . . . . . . . . 4
1.2.3 Evaluation Framework . . . . . . . . . . . . . . . . 5
1.3 Contributions . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.4 Related Works . . . . . . . . . . . . . . . . . . . . . . . . 8
1.5 Outline of this Thesis . . . . . . . . . . . . . . . . . . . . . 9
1.6 List of Publications . . . . . . . . . . . . . . . . . . . . . . 9
2 digital video compression 15
2.1 Digital Video Signals . . . . . . . . . . . . . . . . . . . . 16
2.1.1 Chroma Subsampling . . . . . . . . . . . . . . . . . 17
2.1.2 Spatial and Temporal Information . . . . . . . . . 18
2.1.3 Non-stationarity . . . . . . . . . . . . . . . . . . . 20
2.2 Hybrid Video Compression . . . . . . . . . . . . . . . . . . 22
2.3 Objective Video Quality Metric . . . . . . . . . . . . . . . 24
2.4 Basics of High Efficiency Video Coding . . . . . . . . . . . 25
2.4.1 Quantization Parameter QP . . . . . . . . . . . . . 26
2.4.2 Temporal Coding Structure . . . . . . . . . . . . . 26
2.4.3 Spatial Coding Structure . . . . . . . . . . . . . . . 29
2.4.4 Network Abstraction Layer . . . . . . . . . . . . . 32
2.5 Basics of Versatile Video Coding . . . . . . . . . . . . . . 32
2.6 Analysis of Video Encoder Parameters . . . . . . . . . . . 32
2.6.1 Quantization Parameter QP . . . . . . . . . . . . . 33
2.6.2 GOP Structure and Length . . . . . . . . . . . . . 34
2.6.3 Slices . . . . . . . . . . . . . . . . . . . . . . . . . . 34
2.6.4 Pixel Resolution . . . . . . . . . . . . . . . . . . . . 35
2.6.5 Frames Rate . . . . . . . . . . . . . . . . . . . . . . 37
2.6.6 Optimal Parameter Selection . . . . . . . . . . . . 39
2.7 Novel Error Concealment Method . . . . . . . . . . . . . . 42
2.7.1 Error Concealment Neural Network (ECNN) . . . . 44
2.7.2 Error Concealment Evaluation . . . . . . . . . . . . 45
3 communication systems 50
3.1 Channel Models . . . . . . . . . . . . . . . . . . . . . . . . 51
3.1.1 Wireless Mobile Channel . . . . . . . . . . . . . . . 52
3.1.2 Wireless Channel Model . . . . . . . . . . . . . . . 54
3.1.3 Digital Channel Model . . . . . . . . . . . . . . . . 55
3.2 Multi-carrier Systems . . . . . . . . . . . . . . . . . . . . . 58
3.3 OFDM Modem . . . . . . . . . . . . . . . . . . . . . . . . 60
VVI contents
3.3.1 Cyclic Prefix . . . . . . . . . . . . . . . . . . . . . 64
3.3.2 Channel Estimation . . . . . . . . . . . . . . . . . 66
3.3.3 OFDM Frame . . . . . . . . . . . . . . . . . . . . . 68
3.3.4 Performance Evaluation . . . . . . . . . . . . . . . 69
3.4 Channel Coding . . . . . . . . . . . . . . . . . . . . . . . . 71
3.4.1 Serial Concatenated Codes . . . . . . . . . . . . . . 73
3.4.2 Reed-Solomon Codes . . . . . . . . . . . . . . . . . 74
3.4.3 Convolutional Codes . . . . . . . . . . . . . . . . . 75
3.4.4 Interleaver . . . . . . . . . . . . . . . . . . . . . . . 77
3.4.5 Performance Evaluation . . . . . . . . . . . . . . . 78
3.5 Performance of a Communication System . . . . . . . . . 80
3.5.1 Throughput . . . . . . . . . . . . . . . . . . . . . . 81
3.5.2 Optimal Parameter Selection . . . . . . . . . . . . 83
4 video communication system 85
4.1 Video Transmission over Error Prone Channel . . . . . . . 85
4.2 Resource Allocation and Constraints . . . . . . . . . . . . 87
4.2.1 Channel Capacity and Channel Transmission Rate 88
4.2.2 Buffers and Delay Constraints . . . . . . . . . . . . 90
4.2.3 Bit Allocation . . . . . . . . . . . . . . . . . . . . . 93
4.3 Optimal Parameter Selection . . . . . . . . . . . . . . . . 95
4.4 Evaluation Methodology . . . . . . . . . . . . . . . . . . . 97
4.4.1 Synchronization . . . . . . . . . . . . . . . . . . . . 97
4.4.2 Quality Measure of the Video at the Decoder . . . 98
4.5 Experimental Results . . . . . . . . . . . . . . . . . . . . . 103
4.5.1 System Parameters . . . . . . . . . . . . . . . . . . 103
4.5.2 Evaluation Procedure . . . . . . . . . . . . . . . . . 104
4.5.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . 107
4.6 Low-delay Systems, a Practical Scenario . . . . . . . . . . 113
4.6.1 Adaptive Scheme . . . . . . . . . . . . . . . . . . . 113
4.6.2 Practical Demonstration . . . . . . . . . . . . . . . 117
5 conclusions 120
bibliography 125

Keywords: Videocodierung, Fehlerverschleierung, Videokommunikationssysteme, Orthogonal Frequency-Division Multiplexing (OFDM), Video coding, error concealment, video communication systems, Orthogonal Frequency-Division Multiplexing (OFDM)