Cooperative communications with optimal wireless energy harvesting

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ORIGINAL PAPER

Cooperative communications with optimal wireless energy harvesting Nadhir Ben Halima1 · Hatem Boujemâa2 Received: 9 August 2019 / Revised: 10 February 2020 / Accepted: 31 March 2020 © Springer-Verlag London Ltd., part of Springer Nature 2020

Abstract In this paper, we analyze the performance of cooperative communications with radio frequency energy harvesting (EH). Different relay selection techniques are studied with optimal harvesting duration. The frame with duration T is decomposed in 3 slots. The duration of first slot is αT , and it is dedicated for energy harvesting (0 < α < 1). The duration of second and third slots is (1 − α)T /2. The second and third slots are dedicated to source and relay transmission. When harvesting duration, αT, increases, the packet error probability (PEP) decreases since the harvested energy is large. However, the available time for transmission, (1 − α)T /2, decreases. If harvesting duration is small, the PEP is high due to a low harvested energy. In this paper, we choose the value of harvesting duration to enhance the throughput. The proposed optimal harvesting duration allows up to 4 dB gain with respect to α = 1/3, i.e., same duration used for EH and source transmission. Keywords Cooperative communications · Optimal harvesting duration · Throughput analysis

1 Introduction Relaying techniques with Amplify and Forward (AF) or Decode and Forward (DF) relays for energy harvesting (EH) systems have been studied in [1–6]. Half and full duplex systems were considered in [7–9]. Depending on whether the information can be transported simultaneously in both directions or not, it is referred as full-duplex or half-duplex channel, respectively. Two-way relaying with EH has been suggested in [10,11]. Power allocation has been studied in order to improve the throughput [12,13]. Multihop relaying as well as multiple input multiple output (MIMO) with EH has been suggested to benefit from spatial diversity [14,15]. EH for Nakagami fading channels was studied in [16]. EH has been also extended to cognitive radio networks (CRN) where spectrum sharing is used to improve spectrum utilization [17–19]. Two transmission strategies are available in CRN. The secondary nodes can transmit in frequency holes left unused by primary user. The second solution is to adapt the power of secondary nodes so that interference is low at

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Nadhir Ben Halima [email protected] Hatem Boujemâa [email protected]

1

College of Computer Science and Engineering in Yanbu, Taibah University, Medina, Saudi Arabia

2

COSIM Lab, Tunis, Tunisia

primary receivers. The outage probability of a mixed system with conventional and EH relays was derived in [20]. Harvesting duration optimization in the presence of relays is the aim of this paper. We consider different relaying techniques such as Opportunistic AF (O-AF), Opportunistic DF (O-DF), reactive and partial relay selection (P-RS and R-RS). The frame with duration T is decomposed in 3 parts. The first part, with duration αT, is dedicated for ene