NOMA for Energy-Efficient LiFi-Enabled Bidirectional IoT Communication

Chen Chen, Shu Fu, Xin Jian, Min Liu, Xiong Deng, Zhiguo Ding

Research output: Contribution to journalArticlepeer-review

60 Scopus citations


In this paper, we consider a light fidelity (LiFi)-enabled bidirectional Internet of Things (IoT) communication system, where visible light and infrared light are used in the downlink and uplink, respectively. In order to efficiently improve the energy efficiency (EE) of the bidirectional LiFi-IoT system, non-orthogonal multiple access (NOMA) with a quality-of-service (QoS)-guaranteed optimal power allocation (OPA) strategy is applied to maximize the EE of both downlink and uplink channels. We derive closed-form OPA sets based on the identification of the optimal decoding orders in both downlink and uplink channels, which can enable low-complexity power allocation. Moreover, we propose an adaptive channel and QoS-based user pairing approach by jointly considering users' channel gains and QoS requirements. We further analyze the EE and the user outage probability (UOP) performance of both downlink and uplink channels in the bidirectional LiFi-IoT system. Extensive analytical and simulation results demonstrate the superiority of NOMA with OPA in comparison to orthogonal multiple access (OMA) and NOMA with typical channel-based power allocation strategies. It is also shown that the proposed adaptive channel and QoS-based user pairing approach greatly outperforms individual channel/QoS-based approaches, especially when users have diverse QoS requirements.

Original languageBritish English
Article number9326355
Pages (from-to)1693-1706
Number of pages14
JournalIEEE Transactions on Communications
Issue number3
StatePublished - Mar 2021


  • energy efficiency (EE)
  • Internet of Things (IoT)
  • light fidelity (LiFi)
  • Non-orthogonal multiple access (NOMA)
  • user outage probability (UOP)


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