Link Selection Schemes For Cooperative Buffer-Aided Relay Networks
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Date
2018-03-01
Authors
Siddig, Ali Ahmed Mohamed
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
Recently, cooperative buffer-aided relaying technique has emerged. In which, the
flexibility offered by the buffering capability is exploited to improve the performance
in many aspects such as capacity, diversity gain and power consumption. However, the
improvement comes at the price of higher transmission delay. In this thesis, the objectives
are to develop the cooperative relaying systems with and without delay constraints
as well as to determine an optimal link selection scheme that maximizes the throughput
of cooperative relaying systems with simultaneous wireless information and power
transfer (SWIPT). First, for cooperative relaying systems without delay constraints, a
new link selection scheme that minimizes the outage probability is proposed. It exploits
the channel state information (CSI) and buffer state information (BSI) to maintain
the states of the buffers, thereby minimizing the outage probability. The outage
probability performances in independent and identically distributed (i.i.d.) and independent
and non-identically distributed (i.n.d.) Rayleigh fading channels are investigated.
As compared to the buffer-state-based (BSB) scheme that offers the minimum
outage probability among previous schemes, simulation results show that the proposed
scheme offers lower outage probability and can achieve the BSB scheme’s performance
using less transmission power. In the three-node network, the offered reduction
in power has reached 2.5 dBW at some power values (e.g., using 17 dBW instead of
19.5 dBW). For real-time cooperative relaying systems with specific information rates
and delay constraints, a new link selection scheme is proposed. The proposed scheme
exploits the CSI, BSI and delay state information (DSI) to minimize the outage and
packet dropping probabilities and achieve higher throughput. In order to achieve that,
it uses these information to compromise between the selections of relays for reception
and transmission. The proposed scheme is analysed in the i.i.d. and i.n.d. Rayleigh
fading channels. For systems with high delay constraints, simulation results show that
the proposed scheme offers lower packet dropping probability and higher throughput
as compared to the renowned relay selection schemes. The proposed scheme offers
reduction in power that exceeds 1 dBW in some simulations. Lastly, SWIPT in cooperative
buffer-aided relaying systems is investigated. Power splitting (PS) technique is
considered for SWIPT implementation. An optimal link selection scheme that maximizes
the system throughput is proposed. In each time slot, an optimal PS ratio is
employed if the source is chosen for transmission, while the relay transmits with optimal
power if selected. As compared to the conventional schemes that use predefined
transmission schedule, simulation results show that the proposed scheme offers higher
throughput and signal-to-ratio (SNR) gain that exceeds 10 dB at some SNR regions.