## 1 Introduction
### Related Works  
Cooperative DF/AF relaying systems have been studied by several authors and their performance was analyzed using different adaptive transmission schemes in various fading environments. An AF relaying system with adaptive techniques was investigated for Rayleigh fading channels in [9]. In [10], using different adaptive schemes in a repetition-based AF relaying system, the authors analyzed the average capacity and outage performance over Rayleigh fading channels, where the selection combining method was used at the destination. The system performance of an opportunistic two-hop AF relaying system was analyzed for Rayleigh fading channels in [11; 12; 13], where communication occurs through direct (i.e., source-destination) and indirect (i.e., best relay) links. From the set of multiple relays, the best relay was chosen for communication, such that the SNR at the destination is maximized. In [14; 15], considering the impacts of outdated channel state information (CSI), a performance analysis of cooperative two-hop AF relay selection schemes was conducted for identical and non-identical Rayleigh fading environments. The closed-form solution of the outage probability (OP) and average capacity expressions for different adaptive policies were also derived. Furthermore, in [16; 17], the DF opportunistic relay and AF partial relay selection systems, with an outdated CSI, were investigated in a Rayleigh fading environment. In [18], the performance of a DF relaying system was investigated in Rician environments. The capacity performance of an AF relaying system, in conjunction with adaptive transmission techniques, was analyzed, in [19; 20; 21], for Rician and Nakagami-\(\hat{m}\) fading channels. The system performance of a two-hop opportunistic AF relaying system, with antenna selection, was evaluated, in [2], in Rayleigh fading environment. In [22], orthogonal space-time block-codes (OSTBCs) were used in a two-hop multiple-input multiple-output (MIMO) AF relaying system over Nakagami-\(\hat{m}\) fading channels. The effect of antenna correlation on OSTBCs in two-hop AF relaying in Rayleigh fading environments was analyzed in [23]. Furthermore, the multi-hop systems, with DF and AF relays, were studied using adaptive transmission techniques in Rician and Nakagami-\(\hat{m}\) environments in [24; 25], respectively. The work mentioned in the above literature emphasized the performance analysis of dual-hop cooperative relaying systems, in conjunction with various adaptive transmission policies for classical fading channels. However, in a real scenario, transmission links can suffer from fading as well as shadowing, either concurrently or separately. In [26], the \(\kappa-\mu\) shadowed fading model was introduced to emulate such general channel conditions. This model provides us a generalization of different conventional fading models. It deals with the effects of both large-scale fading (i.e., shadowing) and small-scale fading and can transform into \(\kappa-\mu\), Rician, Rayleigh, One-sided Gaussian, Nakagami-\(\hat{m}\), and Rician-shadowed fading channels. The \(\kappa-\mu\) shadowed fading model is widely used for modeling the point-to-point (P2P) and relay links using non-adaptive transmission techniques [4; 26; 27; 28; 29; 30; 31; 32; 33]. First, in [26], the \(\kappa-\mu\) shadowed fading model was introduced, and the probability density function (PDF), momentum generating function (MGF), and cumulative distribution function (CDF) were derived in closed-form for a P2P communication system. It considers only single-hop P2P channel while our work deals with dual-hop relay channel which is applicable to recent advanced cellular relay systems. The average capacity in a closed-form expression of a P2P system was obtained in [27; 28], and the system performance was analyzed for different fading and shadowing parameters.