# Joint Power Allocation and Link Selection for Multi-Carrier Buffer Aided Relay Network
## 1 Introduction  
In the field of wireless communication, relay networks acquired much consideration to provide better coverage and throughput [1; 2]. For the efficient utilization of wireless resources to provide good quality of services to the users, resource allocation is considered as an important factor [3; 4]. The problem of outage probability and ergodic capacity was studied in energy harvesting relay networks [5]. Under amplify and forward (AF) relaying protocol, the joint power optimization was studied to maximize the throughput of the secondary users [6]. A dual decomposition framework was adopted to solve the problem. In order to increase the spectrum efficiency with an additional multi-user diversity gain, authors [7] proposed a generalized sub-carrier pairing strategy and a low complexity resource allocation scheme for the decode and forward (DF)-based two-way relay network. For both the AF and the DF-based networks, described in [6; 7] respectively, authors assumed that the relay is operating under the conventional protocol (data packets are received from the base station (BS) in one time slot and forwarded to the mobile user (MU) in the next consecutive time slot). A range-division user relay selection strategy was provided to improve the coverage and capacity efficiency of non-orthogonal multiple access (NOMA)-based cooperative networks [8]. Buffer aided relaying (BAR) emerged as a new paradigm for the wireless communication systems and has provided freedom to the link selection, i.e., the choice to choose a particular hop for transmission in a given time slot [9]. With this addition, the resource allocation problem becomes more challenging and is coupled with the link selection. The optimization techniques designed for memoryless relaying nodes cannot be applied for BAR transmission. Thus, the problem of power allocation and link selection for the BAR has received significant attention in the research community [10; 11; 12; 13; 14; 15; 16; 17; 18; 19; 20]. Considering a full-duplex network, power allocation at the source and relay node was studied in [10]. Authors maximized the source arrival rate under the assumption of imperfect self-interference cancellation and statistical delay constraints. For the underlay cognitive radio network with buffer aided DF relay, an adaptive link selection scheme was presented in [11]. A closed-form expression for the data rate was derived by assuming peak power and interference constraints at the secondary nodes. The authors in [12] considered a system where multiple source nodes are communicating with a single destination through a common BAR. Under the total transmit power constraint at each node, this work presented a link selection and a power allocation strategy. The problem of cross-layer resource allocation considering asymmetric time duration over two hops was investigated in [13]. The work in [14] proposed different BAR schemes under full-duplex (FD) relay transmission with self-interference cancellation (SIC) capability at the relaying node. The results showed the considerable gains of the proposed scheme over the conventional FD relay transmission. Further, the authors in [15] studied the security and the delay issues in the buffer enhanced dual-hop transmission. The relay selection schemes for links with equal weights have recently been explored in [16]. Depending on the status of the buffer at each relaying node, the authors in [17] proposed a max-link selection analysis framework. With the Markov chain approach, analytical expressions for the outage probability, the average bit error rate, and the steady-state probability vector were derived. More recently, the problem of link selection for satellite-terrestrial relays was considered in [21] for correlated fading. The joint link selection and power optimization for the uplink-based BAR network were proposed in [19]. Throughput of the system was maximized under limited power budget at all nodes.