Performance Study of Live Video
Streaming over Highway Vehicular
Ad hoc Networks
Author:Fei Xie, Kien A. Hua, Wenjing
Wang, and Yao H. Ho
2007 IEEE
Speaker: L.Y.-Wu
Outline
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I. INTRODUCTION
II. RELATED WORK
III. DATA FORWARDING SCHEMES
IV. EXPERIMENTAL STUDY
V. CONCLUDING REMARKS
I. INTRODUCTION
• Live Video streaming over Vehicular Ad hoc
Networks (VANET) is an attractive feature to many
applications, such as emergency live video
transmission, road-side video advertisement
broadcasting and inter-vehicle video conversation.
• The performance of video streaming suffers from the
delay and packet loss incurred by the long time
disconnection.
• In disaster recovery or traffic accident, it is
important to support the first responders with
live multimedia information about the
emergency situation.
• Transmission the multimedia information over the
inter-vehicle network is a good alternative in the
case where there is no available communication
infrastructure in the emergency area or when a
driver is unable to respond in the critical time.
• Roadside businesses, such as restaurants and hotels,
can broadcast the video advertisement via roadside
infrastructure (e.g., 802.11 access point) to vehicles
driving through.
• Passengers in nearby cars can setup a video
conversation by using the inter-vehicle streaming
technology. Drivers or passengers could also enjoy
watching live news or football match, while the video
data is conveyed by other relay vehicles.
• Thus the node in VANET is powerful to forward
continuous video data to other vehicles or roadside
receivers.
• Furthermore, the IEEE 802.11 standard can support
up to 54Mbps transmission rate. Even between high
speed driving vehicles, it is reasonable to expect a
1Mbps data rate.
• As to the transmission data rate required by
compressed video, if we assume a 320*240 screen
with 16 bits color, a frame rate about 15fps, the
widely-used MPEG compressed video stream rate is
estimated to be about 100 to 150kbps.
• Hence there is enough bandwidth to support video
streaming between vehicles.
• Two network metrics, packet delay and packet loss,
greatly affect the quality of the video in the receiver
end.
• In video streaming, a single video frame is
decomposed into many smaller packets and sent into
the network.
• If the percentage of lost packets excesses the bound
of error correction, the receiver can not playback this
frame.
• Similarly, if the packet arrival time is later than the
playback deadline of the corresponding frame, it will
also be dropped by the decoder in receiver.
• The challenge of video streaming over VANET can
be interpreted by the high dynamics of the vehicles.
• The high velocity and limited communication range
of the vehicles incur frequent link disconnection and
even network partition.
• It takes time for vehicle to catch up with other
vehicles ahead and reconnect the network. We call
this amount of time as catch-up delay .
• During the catch-up phase, the routing protocol uses
the store-and-forward (SF) scheme to buffer the
packet and send it in the next chance.
• In this paper, we are interested in forwarding video
data in highway, because vehicle density in highway
is more suitable to support continuous video
streaming.
• We use real video data and NS2 to study the
performance of video streaming under different
traffic conditions and different data forwarding
schemes.
• Instead of using delay and packet loss ratio, we
evaluate the Peak Signal to Noise Ratio (PSNR) as
the quality of the decoded video in the receiver.
• PSNR is widely used as the major performance
metric in the research of video streaming
II. RELATED WORK
• The procedure of the video streaming application
over VANET has two phases.
– First phase is to send a video trigger to the area of
interest or vehicle via other vehicles.
– The second phase is to transmit the streaming
video data back from the video source.
• Authors proposed a fast triggering method which
uses a distributed method to estimate the backward
and frontward transmission ranges of vehicles.
• V3 presented an architecture for live video streaming
over VANET.
• However, because no real video data are used in their
simulation, only the delay is reported in the
experimental study.
• The end to end delay can not directly reflect the
performance of video streaming, since in many cases,
the delay variance could be absorbed by the receiver
buffer.
• Although there are many researches on video over
MANET using mpeg video data, their network
simulation are statistical model based.
• As for data forwarding in VANET, there are three
classes of schemes that could be applied to VANET.
• One class is the traditional route based forwarding,
like DSR and AODV.
• The second and third classes are sender based and
receiver based forwarding respectively. Both classes
incorporate geographic information and greedily
decide the next relay node.
• There are some routing protocols in VANET using the
street topology information to help the data
forwarding.
• Since we focus on highway scenario in this research,
the topology is not a concern.
• Decoded video quality at the receiver is therefore
affected by two factors:
– encoder compression performance.
– distortion due to the packet loss or late arrivals.
• The video distortion can be modeled as:
• The encoder distortion may be modeled by:
• Where R is the rate of the video stream, and the
parameters D0, θ and R0 are estimated from empirical
rate-distortion curves via regression techniques.
• In this work, we are interested in Dloss,which can be
modeled by
• where Dpkt_loss and Ddelay represent the distortion
contributed by packet loss or delay respectively.
III. DATA FORWARDING SCHEMES
• To compare the sender based forwarding (SBF) and
receiver based forwarding (RBF) schemes in highway,
we implement two data forwarding schemes SBF-H
and RBF-H which are representatives of RBF and
SBR respectively.
• In a highway scenario, there are typically two
directions.
– Denote
as forwarding direction of packet p.
–
as node
driving direction.
• The video sender decide based on the receiver’s
location piggybacked in the video trigger.
Destination
• Let
denote the distance from node
destination .
• We use
• We denote
to the
to denote value of the velocity of
as:
.
• The SBF-H is an extension of GPSR while the RBFH modifies the CBF. The SBF-H is an extension of
GPSR while the RBF-H modifies the CBF.
• In SBF-H, nodes maintain a data structure called
neighbor list (NL).
• Nodes periodically broadcast its location, velocity
and driving direction information.
• Other nodes receive this broadcast packet store the
information in its NL.
• A node chooses the next hop to forward packet p
based on the following three rules:
• Rule 1 has the highest priority.
• We apply Rule 2 to the nodes which satisfy Rule 1, unless
there is no node meets Rule 1.
• The threshold in Rule 2 could be the safe distance
between cars.
• Rule 3 is applied to the nodes selected by Rule 2.
• In Rule 3, we choose the nodes with the maximum
velocity and driving in the same direction as the packet
forwarding direction.
• In RBF-H, a relay node broadcast the packet p to all
the neighboring nodes.
• If the destination receives this packet, it broadcasts an
ACK packet right away.
• Other nodes receiving the ACK simply discard the
packet.
• Each node in the contention uses (2) to estimate t,
which is the time to reach the destination.
•
is the velocity of the destination. If the destination
is static, is zero, or we simply can use the highway
speed limit as
.
IV. EXPERIMENTAL STUDY
• A. Simulation Setup
• We encoded the 10 seconds CIF video sequence
Foreman into MPEG4 data format at 30 fps. Each
frame is packetized into packets of 1024bits and sent
to the network at their playout time in the sender.
• B. Performance Evaluation
• We transmit a 10 second encoded video over a 2 km
road section with different traffic densities.
• Each data point is the average result of 100
simulations with different randomly generated
mobility trace.
V. CONCLUDING REMARKS
• We study the performance of video streaming over
highway VANET.
• We propose two data forwarding schemes particularly
for highway environment, which are SBF-H and
RBF-H.
• These two schemes try to choose the best packet
forwarder in a bi-directional multiple lanes highway.
END