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Performance evaluation of adaptive hybrid ARQ systems Bakhtiyari, Sattar E.
Abstract
In the analysis of ARQ schemes, it is typically assumed that the feedback channel is noiseless and perfect synchronization can be achieved. These assumptions may not be valid for the situations where the channel error rate is high especially with memory ARQ schemes. In such cases, a more realistic evaluation of the performance is required to provide accurate results for the schemes in question. A general investigation of ARQ schemes with and without memory, taking into account the sensitivity of frame header and return channel errors, is presented and the resulting throughput expressions are obtained. Knowing the influence of these parameters on the system performance, we propose efficient techniques to reduce their effects on the performance degradation. These techniques range from employing more powerful error correction codes to transmitting a few copies of the same sequence for the header and acknowledgment message consecutively and combining the noisy sequences at the receiver. Even though ARQ schemes offer appreciable throughput improvement in AWGN, their performance suffers greatly in the Rayleigh fading environment. In such a scenario, the optimum solution is to adapt the rate of error correction code to the prevailing channel conditions. An adaptive Type-I Hybrid ARQ (HARQ) scheme, in which the transmitter selects the code rate for each message based on the assessed channel conditions, is proposed and investigated. A model for evaluating the throughput of the scheme is presented, and it is illustrated that an accurate assessment of the channel conditions is crucial in the achievement of high throughput. Moreover, an adaptive Type-II HARQ with Complementary Punctured Convolutional Codes (CPC) is presented. This protocol stores the corrupted copies of a packet encoded with CPC codes at the receiver and combines them to improve the reliability of the system and reduce the number of unnecessary retransmissions.
Item Metadata
Title |
Performance evaluation of adaptive hybrid ARQ systems
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
1993
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Description |
In the analysis of ARQ schemes, it is typically assumed that the feedback channel is
noiseless and perfect synchronization can be achieved. These assumptions may not be valid
for the situations where the channel error rate is high especially with memory ARQ schemes.
In such cases, a more realistic evaluation of the performance is required to provide accurate
results for the schemes in question. A general investigation of ARQ schemes with and
without memory, taking into account the sensitivity of frame header and return channel
errors, is presented and the resulting throughput expressions are obtained. Knowing the
influence of these parameters on the system performance, we propose efficient techniques to
reduce their effects on the performance degradation. These techniques range from employing
more powerful error correction codes to transmitting a few copies of the same sequence for
the header and acknowledgment message consecutively and combining the noisy sequences
at the receiver.
Even though ARQ schemes offer appreciable throughput improvement in AWGN, their
performance suffers greatly in the Rayleigh fading environment. In such a scenario, the
optimum solution is to adapt the rate of error correction code to the prevailing channel
conditions. An adaptive Type-I Hybrid ARQ (HARQ) scheme, in which the transmitter
selects the code rate for each message based on the assessed channel conditions, is proposed
and investigated. A model for evaluating the throughput of the scheme is presented, and it is
illustrated that an accurate assessment of the channel conditions is crucial in the achievement
of high throughput. Moreover, an adaptive Type-II HARQ with Complementary Punctured
Convolutional Codes (CPC) is presented. This protocol stores the corrupted copies of a
packet encoded with CPC codes at the receiver and combines them to improve the reliability
of the system and reduce the number of unnecessary retransmissions.
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Extent |
3377525 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-02-20
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0064874
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
1994-05
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.