Transmit Antenna Selection Schemes for NOMA with Randomly Moving Interferers in Interference-Limited Environment  
[PERSON]  
1 Wireless Communications Research Group, Faculty of Electrical and Electronics Engineering,  
Ton Duc Thang University, Ho Chi Minh City 700000, Vietnam 1  
2 Faculty of Electronics Technology, Industrial University of Ho Chi Minh City (IUH),  
Ho Chi Minh City 700000, Vietnam; [EMAIL_ADDRESS]  
2  
[PERSON]  
2 Faculty of Electronics Technology, Industrial University of Ho Chi Minh City (IUH),  
Ho Chi Minh City 700000, Vietnam; [EMAIL_ADDRESS]  
2  
[PERSON]  
System performance of NOMA users are evaluated in several scenarios [13; 14; 15; 16; 17]. Having the ability to provide high spectrum efficiency and massive connections, the authors in [13] studied multiple-input multiple-output (MIMO) employing NOMA to fulfill the escalating demands of higher connectivity and data rates. Such emerging wireless applications of MIMO-NOMA are evaluated in derived formulas to indicate improvement in terms of the sum rate and capacity and this model benefits from the antenna with RAS over Rayleigh fading channel. A NOMA downlink system is explored in which a BS is designed with multi-antenna and single-antenna users operate in two multicast groups [14]. They considered a case that one group can afford to be served opportunistically and low-power devices with limited processing capabilities are served in the other group [14]. As a main characteristic, more NOMA users are allowed to access than OMA. Furthermore, the strategy to allocate power to each user and user selection schemes are the main concerns to provide better performance as evaluating NOMA system. In [18], an optimal problem under QoS requirements is considered by minimizing the total transmit power. They introduced how to search for optimal subcarrier assignments for users and suitable allocated power levels are set for subcarriers [18]. Considering downlink and uplink in NOMA network as in [19], two users with the outage probability and the average rate can be achieved to adapt to flexibly meeting various QoS requirements. The exact expressions and approximate expressions at a high signal-to-noise ratio are provided to benefit the proposed system comparing to existing systems [19]. In addition, optimal power allocation within each cell is examined in visible light communication (VLC); multi-cell networks relying on NOMA and such schemes need to perform to obtain a better achievable user rate under user QoS constraints [20]. NOMA is able to be employed with integrated satellite terrestrial networks in [21] in different scenarios of user scheduling schemes. Recently, the authors in [22; 23] studied the outage performance of users whose direct links were unavailable in hybrid satellite terrestrial relay networks relying on NOMA. However, the fixed power allocation strategy is implemented in these works [22; 23]. Although multiple antenna designs in NOM benefits higher performance gains, unfortunately, a larger number of antennas results in higher cost and complexity in computation. Fortunately, to reduce the undesirable effects of serving multiple antennas at the same time, antenna selection (AS) is introduced as a practical scheme to implement in NOMA. In addition, AS scheme still preserves the diversity and throughput benefits in the scenario of multi-antenna design. For instance, full diversity gain is achieved in AS techniques [24]. In addition, AS in combination with NOMA is introduced in various works [25; 26; 27; 28]. In particular, by employing transmit AS (TAS) at the BS, downlink NOMA was investigated in terms of the outage performance [25]. In addition, maximal sum-rate in downlink MIMO-NOMA networks can be obtained in efficient AS; techniques were proposed by recent works [25; 27]. More recently, NOMA networks considered some stochastic geometry models to describe the location of nodes and users.