Throughput optimization of cooperative non orthogonal multiple access
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Throughput optimization of cooperative non orthogonal multiple access Ghassan Alnwaimi1
· Hatem Boujemaa2 · Kamran Arshad3
Accepted: 22 September 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract This paper derives the outage and packet error probabilities of Non Orthogonal Multiple Access (NOMA) systems. In the first time slot, the Base Station transmits a combination of two symbols sw and ss dedicated for weak and strong users. This signal is received by the two users and a relay. In the second time slot, the relay amplifies the received signal to the two users. Both users use the signal with the highest Signal to Interference plus Noise Ratio among direct and relayed signals. The weak user detects only its signal. Strong user first detects symbol sw of weak user. After removing the contribution of weak user, strong user detects its own symbol ss . In this article, expressions for outage probability, Packet Error Probability and the throughput of cooperative NOMA are derived. We also optimize the power allocated to weak and strong users to maximize the system throughput. Keywords NOMA · Cooperative systems · Outage probability · PEP · Throughput · Rayleigh fading channels
1 Introduction NOMA is a promising access technique for future wireless systems and allows a higher spectral efficiency than Orthogonal Multiple Access (OMA) [1,2]. In NOMA based-systems, the Base Station (BS) transmits a superposition of two symbols dedicated to strong and weak users. Weak user has a low Signal to Interference plus Noise Ratio (SINR), detects only its signal and treats the signal of strong user as interference. The strong user has a larger SINR than weak user, it first detects the symbol of weak user. After removing the contribution of weak user sw , strong user detects its own symbol ss . Cooperative NOMA has been proposed in [3] where the best users act as relays for the other users. In [4], cooperative
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NOMA was studied with nodes dedicated to relay the users’ signals. NOMA for Multiple Input Multiple Output (MIMO) systems has been studied in [5]. In [6–8], it has been shown that the spectral efficiency of NOMA systems improves when there are both direct and relayed signals. NOMA systems with Simultaneous Wireless Information and Power Transfer (SWIPT) has been studied in [9–11]. The relay can harvest energy from the base station using the Radio Frequency (RF) signals. NOMA for Cognitive Radio Networks (CRN) has been suggested in [12,13]. In CRN, Primary Users (PU) and Secondary Users (SU) share the same frequency band, and SU may transmit while PU are idle. Resource allocation techniques for NOMA systems have been suggested in [14–16]. The security aspects of NOMA systems have been studied in [17–19]. Jamming signals can be added to avoid that an eavesdropper decodes the base station data.
Ghassan Alnwaimi [email protected] Hatem Boujemaa [email protected] Kamran Arshad [email protected]
1
King Abdulaziz University, Jeddah, Kingdom of Saudi Arabia
2
Sup’Com, COSIM La
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