Adaptive Joint Source-Channel Coding of Real-Time Multimedia for Cognitive Radio
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Date
2014-09-02
Authors
Kedia, Aditya
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Abstract
Radio spectrum has become a scarce and priced resource due to the rapid growth of wireless
networks. However, recent surveys conducted by the FCC indicate that a large part of
the allotted frequency spectrum lies unused. Cognitive radio systems, built on the software
defined radios, allow the efficient usage of these unused frequency spectrum. Cognitive
radio systems can be modeled as a multiple access channel in which certain users have the
priority (primary users) while others (cognitive or secondary users) are allowed to access
the channels without causing any interference to the primary users. However a secondary
user’s transmissions not only encounter high levels of uncertainty and variability in the
number of channels available to them, but they also suffer data losses if a primary user
activity occurs. Under such rigid constraints, the reliable transmission of real time multimedia
of a secondary user with an acceptable quality of service becomes challenging.
Multimedia transmission in a cognitive system requires channel adaptive source and
channel coding schemes. In order to address this problem, this thesis investigates and develops
a novel joint source-channel coding (JSCC) approach. The proposed JSCC allows
the dynamic generation of codes, which minimizes the end-to-end distortion. This JSCC
is based on quantized frame expansions to introduce redundancy into transmitted data. An
algorithm has been developed to determine the optimal trade-off between redundancy and
quantization rate, under a constraint on channel capacity. The proposed approach does
not require the communication of any overhead data between the transmitter and receiver.
When compared to codes commonly used to deal with packet losses, simulation results
indicate that the proposed JSCC can achieve lower distortion for secondary user’s transmissions
in cognitive radio systems.
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Keywords
Joint Source-Channel Coding, Multiple description coding, Quantized frame expansion, Cognitive radio