By Asha Iype Shashanka CD 12/07/2011 Video transmission using
USRP
Slide 2
Introduction Mobile multimedia communications USRP as a
platform to excavate mobile computing environments Simple DVB setup
Webcam on the air using USRP Modulation in software using GNU
Radio
Slide 3
Basic block diagram Video file source (webcam or a video file)
GNU Radio modulator and processing USRP transmitter USRP receiver
GNU Radio demodulator and processing File sink (video playback
e.g., VLC player)
Slide 4
Video Transmitter GNU Radio
Slide 5
Real time video streaming Why do we need VLC streaming? How do
we link webcam and GNU radio?
Slide 6
Real time video streaming A webcam is one of the simplest of
camera designs, containing no video encoder onboard VLC streamer
for encoding and streaming The stream output feature in VLC outputs
the stream read by the VLC to a file
Slide 7
Real time video streaming A UNIX "pipe" : what's written at one
end shows up as available data at the other end Create the pipe
using the command mkfifo
Slide 8
GNU Radio Transmitter File Source Packet Encoder GMSK Mod
Multiply Constant USRP Sink
Slide 9
GNU Radio Transmitter Flow Diagram
Slide 10
USRP Transmitter FPGA Digital up conversion Interpolation USB
USB2 interface to PC DAC High Speed 14-bit DA DAC Clock - 128MS/s
RF Transceiver RFx2400 RFX2400 has a band-pass filter around the
2400 to 2483 MHz
Slide 11
Video receiver USRP GNU Radio VLC player
Slide 12
USRP receiver RF front- end ADCFPGAUSB 2.412 GHz 0101011 .bit
stream -Downconversion -High-BW math -Reduce data rate -Cypress FX2
- For PC interface RFX2400 -12bit High Speed AD - 64MSamples/s
Slide 13
GNU Radio USRP source Low-pass filter GMSK demodulator Packet
decoder File sink
Slide 14
GNU Radio flow diagram
Slide 15
Real-time streaming using VLC player Receiving pipe just gets
the input stream at one end and delivers to the other end Create
the receiving pipe mkfifo rx.ts Transcoding MPEG2 + MPGA (TS)
Display locally option Start streaming UNIX pipe
Slide 16
Project activities Simulation without USRPs Stored video file
and loop back Transmission with USRPs Stored video file with USRP
Real time video transmission Streaming with USRP
Slide 17
Results and Observations Received signal FFT plot with USRPs 3
meter apart Received signal FFT plot with USRPs >9 meter
apart
Slide 18
Delay in reception of the video Delay with large distance
(>9m) between USRPs Delay with short distances (1m) between
USRPs Delay with stored video file Delay is mainly because of
streaming and processing (encoding and multiplexing) Results and
Observations
Slide 19
Packet loss at reception of the video Negligible packet loss at
short distances (1-3m) Distortion in video received at large
distances (>9m) showing more packet loss Distortion was
extremely high with increased distances and with interferences like
wall and furniture
Slide 20
Results and Observations Distortion observed at large
distances
Slide 21
Results and Observations FFT plot fluctuation at the receiver
showing packet loss uUuUuU ( USRP Underrun) at the transmitter The
speed of the computer processor plays a role
Slide 22
Future work Try with different player and different codec for
faster and better encoding Different modulation schemes suitable
for video transmission Implementing good error correcting schemes
to correct the video frames received and hence reduce
distortion