An Adaptive Video Streaming Platform with Adaptive Channel Coding

Tao Han

Advisor: Prof. Dapeng Oliver Wu

|| Introduction || Experiment 1 || Experiment 2 || Experiment 3 || Experiment 4 || Download || Useful Links ||

Introduction

The goal of this project is to provide the methods and framework for a general multimedia wireless test-bed. The test-bed is built with GNU Radio and Universal Software Radio Peripheral (USRP). In Multimedia Communications and Networking Laboratory (MCN) at University of Florida, there are some works have been done for the test-bed, including Real-world Transmission with GNU Radio and USRP and Cross-layer wireless video testbed. In this project, I continue to do some related works on it, especially in providing approach to plugin cross layered codec and framework of modular adaptive codec for multimedia wireless test-bed.

The following is the testbed architecture:

To implement adaptive control in the testbed architecture, we need to design a flexible framework and a universal well-defined codec interface. In this project, I use Python and C/C++ combined programming to implement some very simple but workable sample softwares in several experiments:

Experiment 1: Send live video stream data via GNU Radio and USRP
Experiment 2: Send video stream data via wireless channel without MAC
Experiment 3: Send video data via wireless channel with channel coding
Experiment 4: Send data via wireless channel with RCPC channel coding

The purpose of the experiment 1 is to build a simple but flexible video data transpotation system. In experiment 2, the CSMA/CD MAC layer is removed from the transportation system so that it works more efficiently in point-to-point wireless transport which doesn't need CSMA/CD MAC layer. In experiment 3, I provide a general mechanism to add custmized codec (or modulation) modules into the transport system. Finally, I add a RCPC channel codec module into the transport system in experiment 4.

You can download source codes in the experiment sections, and you can follow the result links of these experiments to interact with flash clips to know how I do the experiment as well. Also you can go to the download section to download all the demonstration flash clips and all source codes in one file. Lastly, you can find some information in useful links section.

Experiment 1: Send Video Data by a TCP/IP tunnel (with MAC Layer ENABLED) based on GNU Radio and USRP

The purpose of this experiment is to show how a simple video transport system works on GNU Radio and USRP boards. The experiment builds a wireless TCP/IP tunnel between two Linux PCs based on GNU Radio and USRP, and sends video data on it.

As a foundation of the wireless testbed, the data transportation mechanism must be flexible and easy to use. I choose TCP/IP as the core of the data transportation mechanism so that all TCP/IP based applications can send and receive data by it. So I start my work based on tunnel.py, which is a GNU Radio example python program building a wireless TCP/IP tunnel among nodes on a CSMA/CD transmission medium. Program tunnel.py uses binary exponential back-off(BEB) algorithm as its MAC mechanism.

In this experiment, I have two Linux PCs with GNU Radio 3.3.0 installed on it. There is a example program GNU_RADIO_BASE_DIRECTORY/gnuradio-examples/python/digital/tunnel.py, which I will use to set up the wireless TCP/IP channel between the two PCs. I use VLC media player as the video stream data sender and receiver, in fact you can use any TCP/IP based video capture/replay/streaming software instead of VLC media player.

In this experiment, I didn't write any new program code, I just use tunnel.py to perform all the data transportation. But according to my experience, we should be very careful to adjust the USRP parameters to get them work. Here is my tunnel.py command lines, which make sure the USRP boards work well in our laboratory.

You should adjust all the parameters to get them work in your own circumstance. For your convenience, I provide the source files you can download here.

The following is the demonstration in flash clip, which I create using WINK. You can interact with it to have a look at what I do in my experiment. Please be very patient to wait for the flash clip loading, typically you have to wait more than 1 minute when you are on a 1Mbps ADSL link. To get acceptable display, I recommend you use a large screen which has at least 1366 pixels in width resolution. When you play the flash clip, you can click the green buttons if necessary. You may also need to know some concept about X-Window to know what the demonstration is showing.

Click to look at the the result of experiment 1.

The result of experiment 1 indicates that video stream goes well over GNU Radio and USRP boards.

Experiment 2: Send video stream data via wireless channel without MAC

In experiment 1, I have set up a wireless channel between host A and host B, which supports TCP/IP tunnel over it. As a default aspect, between IP layer and PHY layer there is a MAC layer, which enables CSMA/CD on a broadcast medium and allows multiple nodes access the medium simultaneously. In our wirless testbed, we hope provide a flexible framework for research purpose on wireless communication, for example, sometime we want to remove MAC from the system to acquire better performance in a point-to-point wireless communication system.

In this experiment, I modify the tunnel.py and rename it as tun_nomac.py, in which I remove the MAC mechanism. Without MAC mechanism, I don't need to worry about the tx amplitute, rx gain and threshold required by CSMA/CD, so that I can set these parameters very freely to get much better performance in our lab's circumstance. For example, I can set a higher rx gain to improve demodulation capacity without worrying about the CSMA/CD threshold.

You can download the source code and decompress the files, then run the program tun_nomac.py with some suitable command line options to get best performance in your own circumstance.

The following are the demonstration flash clips, enjoy it!

Result of experioment 2-1: Compare the performance between with and without CSMA/CD MAC.

Result of experioment 2-2: Transport video data by non-MAC channel.

As the result of experiment 2-1 shows, in point-to-point environment, the performance of wireless channel without MAC is better than one with MAC. I will use the non-MAC channel as the base of the experiment 3 and experiment 4.

Experiment 3: Send video data via wireless channel with channel coding

To do research work on wireless communication, we often need to add our own channel coding module to the system. Here I write a very simple example program to show how to write a channel codec module and invoke it from the testbed wireless framework. In this experiment, I use SWIG to wrap the C/C++ codec module code into framework Python code, please refer to SWIG manual to learn how it works and how to use it.

You can download source code, decompress all the files to a directory and then run the following commands to build the programs:

swig -c++ -python pycodec.i
python setupcodec.py build_ext --inplace

And then, run the program tun_nomac_codec.py on both Linux PCs to setup a wireless channel with channel coding between the PCs.

The following is the demonstration of using ping command to test the wireless channel with channel coding.

Result of experiment 3.

Experiment 4: Send data via wireless channel with RCPC channel coding

Based on experiment 3, I write wrap code to invoke a RCPC FEC channel codec module. You can download the source code here. It is very simple example code using fixed code family and code number, you may want to modify it and add adaptive control to fit to wireless fading channel and multimedia data transportation requirements.

The following is the demonstration.

Result of experiment 4.

Download

You can download all the demonstration flash clips in one file, and you can also download all the source files.

Useful Links

Here are some useful links:

Python:
Python Programming Language – Official Website

X-Window:
X Window System

VLC:
Official page for VLC media player, the Open Source video framework!

SWIG:
Simplified Wrapper and Interface Generator

WINK:
WINK Homepage