# Two-Way Transmission for Low-Latency and High-Reliability 5G Cellular V2X Communications  
[PERSON]  
1 Wireless Communications Research Group, Faculty of Electrical and Electronics Engineering, Ton Duc Thang University, Ho Chi Minh City 700000, Vietnam; [EMAIL_ADDRESS]  
[PERSON]  
2 Faculty of Electronics Technology, Industrial University of Ho Chi Minh City (IUH), Ho Chi Minh City 700000, Vietnam; [EMAIL_ADDRESS] (T.-T.N.J. ; [EMAIL_ADDRESS] (C.-B.L.) [PERSON]  
2 Faculty of Electronics Technology, Industrial University of Ho Chi Minh City (IUH), Ho Chi Minh City 700000, Vietnam; [EMAIL_ADDRESS] (T.-T.N.J. ; [EMAIL_ADDRESS] (C.-B.L.) [PERSON]  
33 School of Electrical and Electronics Engineering, Chung-Ang University, Seoul 06974, Korea 33*Correspondence: [EMAIL_ADDRESS]; Tel. : +82-2-820-57343  
radio access technology to overcome aforementioned drawback of OMA and fully utilize the capacity area, and is considered as a potential solution for fifth-generation (5G) wireless networks [7]. In NOMA, transmitters send multiple signals in a superimposed form by exploiting power domain multiplexing, and receivers facilitate successive interference cancellation (SIC) to detect desired signals [8]. NOMA is able to provide lower system delays, higher reliability, higher transmission rates, and lower-cost service requirements in comparison with the OMA scheme [9; 10]. Recently, cooperative communications have been actively studied, whose major benefits are wider cell coverage and higher spectrum efficiency (SE). Cooperative power domain non-orthogonal multiple access (CNOMA) have received a lot of attention as an example of cooperative communications [11]. In CNOMA, near users (NU) obtain their own signals by decoding the superposed signal and forward far users' (FU) signals to FUs who have weaker links with a base station (BS). CNOMA shows performance improvement in terms of outage probability and average sum rate. To maximize fairness for paired user group and further improve the performance of CNOMA, power allocation among multiple users are considered under a half-duplex mode [12]. To obtain higher SE, a full-duplex mechanism has recently been proposed for CNOMA [13], in which downlink (DL) full-duplex CNOMA system is studied in terms of outage probability and ergodic rate without direct link between BS and FU. Power allocation architecture was also presented for the purpose of maximizing the minimum achievable rate and minimizing outage probability of users. Most of related works have focused on DL transmission, in which NUs support FUs' transmissions while uplink (UL) transmission is also important for cooperative relaying. [PERSON] et al. designed time and power allocations for two-hop decode-and-forward (DF) NOMA relaying protocol to satisfy two NOMA users' different quality-of-service (QoS) requirements [14]. In [15], a two-way relay-based CNOMA (TW-CNOMA) scheme for DL and UL transmissions of two users was presented, in which FU is assisted by a dedicated relay node equipped with two antennas for simultaneous reception of bidirectional signals. Compared with conventional one-way relay-based CNOMA (OW-CNOMA) and OMA, works in [15] confirmed higher SE gain and a lower amount of required time slots. A power allocation scheme maximizing the achievable sum-rate was proposed in [16], where a relay node provides the ability to allow multiple FUs' DL and UL transmissions in the TW-CNOMA scheme. [PERSON] and [PERSON] studied NOMA systems with an AF/DF-aided BS-assisting communication from a wireless powered device to a nonenergy harvesting device, where two devices have distinct predefined QoS requirements [17]. In [18; 19], energy harvesting (EH)-enabled CNOMA network accommodating two users, a source and an EH-assisted relay were studied under an imperfect channel state information (CSI) environment. In [20], a cognitive radio system employing NOMA technology was investigated, where the outage performance of the secondary network using relay selection policies was examined.