Abstract
In this paper, we analyze the outage probability of an amplify-and-forward (AF) cooperative non-orthogonal multiple access (NOMA) model in multi-relay multiuser networks. In contrast to conventional cooperative networks, relays in the considered network have no embedded energy supply; they need to rely on the energy harvested from the signals broadcasted by the source for their cooperative NOMA transmission. Based on this structure, a new relay selection scheme is proposed, considering both channel state information (CSI) and battery status of relays. Assuming each relay has infinite or finite energy storage for accumulating energy, we use the infinite or finite Markov chain to capture the evolution of relay batteries and certain simplified assumptions to reduce computational complexity of the Markov chain analysis. The approximate closed-form expressions for the outage probability of the proposed scheme are derived therefrom. All theoretical results are validated by numerical simulations. The impacts of the system parameters, such as relay number, energy harvesting threshold and battery size, on the performance are extensively investigated.
Highlights
With the aim of increasing system capacity and achieving higher spectral efficiency, non-orthogonal multiple access (NOMA) has been recognized as a promising multiple access technique for fifth generation (5G) networks due to its superior spectral efficiency [1].The key idea of NOMA is to serve multiple users in the same frequency band, but with different power levels, which is a domain fundamentally different from conventional orthogonal access technologies [2]
Power-domain NOMA allocates less transmitting power to users with better channel conditions and more transmit power to users with worse channel conditions in order to achieve a balanced tradeoff between system throughput and user fairness
Our scheme can guarantee acceptable system performance (the best outage probability is 10−5 when transmission signal to noise ratio (SNR)is 20dB) even if the relays do not use their own batteries to power the relay transmission which demonstrates the superiority of our scheme compared to the common cooperative system or common NOMA system
Summary
With the aim of increasing system capacity and achieving higher spectral efficiency, non-orthogonal multiple access (NOMA) has been recognized as a promising multiple access technique for fifth generation (5G) networks due to its superior spectral efficiency [1].The key idea of NOMA is to serve multiple users in the same frequency band, but with different power levels, which is a domain fundamentally different from conventional orthogonal access technologies [2]. EH capabilities have received much attention as they use the energy harvested from the source signal to perform information forwarding [9] This can solve the problem of the energy supply of relays and expand the application of EH-based wireless communications. In [10], a wireless cooperative network is considered in which multiple source-destination pairs communicate with each other via an energy harvesting relay. Our scheme can guarantee acceptable system performance (the best outage probability is 10−5 when transmission signal to noise ratio (SNR)is 20dB) even if the relays do not use their own batteries to power the relay transmission which demonstrates the superiority of our scheme compared to the common cooperative system or common NOMA system
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