12-06-2014, 11:11 AM
Correlation-Aware QoS Routing With Differential Coding for Wireless Video Sensor Networks
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Abstract
The spatial correlation of visual information retrieved
from distributed camera sensors leads to considerable
data redundancy in wireless video sensor networks, resulting
in significant performance degradation in energy efficiency
and quality-of-service (QoS) satisfaction. In this paper, a correlation-
aware QoS routing algorithm (CAQR) is proposed to
efficiently deliver visual information under QoS constraints by
exploiting the correlation of visual information observed by
different camera sensors. First, a correlation-aware inter-node
differential coding scheme is designed to reduce the amount of
traffic in the network. Then, a correlation-aware load balancing
scheme is proposed to prevent network congestion by splitting the
correlated flows that cannot be reduced to different paths. Finally,
the correlation-aware schemes are integrated into an optimization
QoS routing framework with an objective to minimize energy consumption
subject to delay and reliability constraints. Simulation
results demonstrate that the proposed routing algorithm achieves
efficient delivery of visual information under QoS constraints in
wireless video sensor networks.
INTRODUCTION
RECENT advances in imaging hardware and wireless
communications have fostered the use of video sensors
in various distributed sensing applications [10], [16]. By integrating
imaging sensor, embedded processor, memory, and
wireless transceivers on a single device, a video sensor node is
able to retrieve, process, store, and transmit visual information
under limited power supply. Networks of interconnected video
sensor nodes are referred to as wireless video sensor networks
(WVSNs) [2], [24], in which multiple video sensors collaborate
with each other to provide enriched observations of the
environment. WVSNs can enhance a lot of applications such
as environmental monitoring, traffic enforcement, and remote
health care. Most of these applications require that visual information
be delivered under predefined quality-of-service (QoS)
constraints. This is a challenging task because video sensors
are constrained in battery and processing capabilities, while the
delivery of visual information is resource-demanding.
RELATED WORK
Joint compression/aggregation and routing has been proposed
to deal with scalar data in sensor networks. In [22], the
performances of different routing with compression schemes
are analyzed. The problem of correlated data gathering is
studied in [5] and [18], where the goal is to minimize the total
communication cost in the network. The Minimum Fusion
Steiner Tree (MFST) routing algorithm [20] is proposed for
energy efficient data gathering with aggregation, in which
both costs for data transmission and data fusion are optimized.
Although these results work well for scalar data, new solutions
are needed for the delivery of visual information which has
high bandwidth demand and QoS requirements.
Video In-Network Compression
Due to the huge size of raw visual information, images
and video sequences are compressed prior to transmission. A
lot of standardized techniques can be applied for image and
video coding, such as JPEG/JPEG 2000 and H.26x/MPEG.
These standards are based on the predictive coding concept.
In contrast, distributed video coding (DVC) [11] allows for
separate encoding of correlated sources and joint decoding at
the end user. DVC is introduced to reduce the computational
complexity at the encoders, however, there is a lack of practical
implementations of DVC in sensor networks. On the other
hand, there are many studies on reducing the computational
complexity on low-power DSPs for standardized coding techniques.
For these reasons, we consider the standardized coding
techniques in our work.
CORRELATION-AWARE QOS ROUTING
We propose a correlation-aware QoS routing algorithm
(CAQR) for the delivery of visual information in WVSNs. By
utilizing the correlation characteristics of video sensors, the
algorithm achieves energy-efficient delivery of visual information
while satisfying QoS constraints. CAQR is a distributed
routing solution for WVSNs, and its components are designed
to be implemented on each sensor node. In the following, we
explain the CAQR algorithm in detail.
Coding Efficiency in QoS Routing
We now evaluate the gain of correlation-aware coding when
it is implemented in the QoS routing algorithm. We find solutions
to the packet delivery ratio update (PDRU) problem
in Section IV-C, and then we test the best average differential
coding efficiency after channel coding in (35).
The parameters in the PDRU problem (32) are determined as
follows. The average size of an intra frame is determined from
the statistics of the video traces in [23]. The payload length of a
packet is set to 50 Bytes. The number of packets in a frame can
then be estimated from the average size of the frame and the
packet length. We use a series of block codes with structures
[17] for dynamic channel coding. The block length is
set to 127, and the number of correctable bits varies from 1 to
31. A single hop scenario with BPSK modulation is considered,
where the received SNR is assumed to be uniformly distributed
between dB and 15 dB.
CONCLUSION
We have proposed a correlation-aware QoS routing algorithm
for wireless video sensor networks. Based on the correlation
characteristics of visual information in sensor networks, we
introduce a correlation-aware inter-node differential coding
scheme and a correlation-aware load balancing mechanism.
These correlation-aware operations are integrated in a distributed
routing framework. The whole routing algorithm
minimizes energy consumption under delay and reliability
constraints. The performance of the algorithm is evaluated
in terms of energy efficiency, delay performance, and frame
delivery ratio. Evaluation results show that, by integrating correlation-
aware operations in the routing process, the proposed
algorithm achieves efficient delivery of visual information in
wireless video sensor networks.