Cross layer hybrid ARQ2 : cooperative diversity.
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Date
2008
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Abstract
Cooperative communication allows for single users in multi user wireless network to share
their antennas and achieve virtual antenna transmitters, which leads to transmit diversity.
Coded Cooperation introduced channel coding into cooperative diversity over traditional
pioneer cooperative diversity methods which were based on a user repeating its partner's
transmitted signals in a multi-path fading channel environment in order to improve Bit Error
Rate (BER) performance..
In this dissertation the Coded Cooperation is simulated and the analytical bounds are
evaluated in order to understand basic cooperation principles. This is done using Rate
Compatible Punctured Convolutional Codes (RCPC). Based on the understanding of these
principles a new protocol called Cross Layer Hybrid Automatic Repeat reQuest (ARQ) 2
Cooperative Diversity is developed to allow for improvements in BER and throughput.
In Cross Layer Hybrid ARQ 2 Cooperation, Hybrid ARQ 2 (at the data-link layer) is
combined with cooperative diversity (at the physical layer), in a cross layer design manner, to
improve the BER and throughput based on feedback from the base station on the user's initial
transmissions. This is done using RCPC codes which partitions a full rate code into sub code
words that are transmitted as incremental packets in an effort to only transmit as much parity
as is required by the base station for correct decoding of a user's information bits. This allows
for cooperation to occur only when it is necessary unlike with the conventional Coded
Cooperation, where bandwidth is wasted cooperating when the base station has already
decoded a user's information bits.
The performance of Cross Layer Hybrid ARQ 2 Cooperation is quantised by BER and
throughput. BER bounds of Cross Layer Hybrid ARQ 2 Cooperation are derived based on the
Pairwise Error Probability (PEP) of the uplink channels as well as the different inter-user and
base station Cyclic Redundancy Check (CRC) states. The BER is also simulated and
confirmed using the derived bound. The throughput of this new scheme is also simulated and
confirmed via analytical throughput bounds. This scheme maintains BER and throughput
gains over the conventional Coded Cooperation even under the worst inter-user channel
conditions.
Description
Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2008.
Keywords
Wireless networks., Wireless communication systems., Theses--Electronic engineering.