## 1 Introduction  
In most traditional wireless communication systems, such as cellular networks and satellite communications, the diversity combining technique is one of the well-known and effective measures to mitigate the adverse effects of fading and to improve system performance and reliability [1]. Among the classical diversity combining techniques, gain diversity combining schemes, namely equal gain combining and maximum ratio combining (MRC), can achieve better system performance compared with selection combining schemes, including pure selection combining (PSC) and switched diversity combining (SDC) [2]. These gain combing schemes and PSC not only need to continually detect all diversity branches but also require some or all knowledge of the channel state information, resulting in a more complex system structure and energy consumption, whereas the advantage of the SDC scheme is that the receiver monitors only one branch at a time and switchesto the next branch when the input signal-to-noise ratio (SNR) of the current branch falls below a threshold SNR. Nowadays, the SDC scheme has three different models, namely dual-branch switch-and-stay combining (SSC) [1], multibranch switch-and examine combining (SEC) [3], and SEC with post-examining selection (SECps) [4]. In an SSC scheme, the receiver selects a particular antenna branch until its instantaneous SNR falls below a predetermined threshold. Whenever this occurs, the receiver switches to the other branch and stays there, regardless of the quality of the other branch. For an SEC scheme, the receiver chooses the first branch and estimates its instantaneous SNR at the beginning, then compares it with a predetermined threshold. If the SNR of the first branch is not less than the predetermined threshold, then the receiver employs the first branch for signal reception. Otherwise, the receiver switches to the second branch and examines it. This process continues until the receiver finds an acceptable branch. If no branch is available, then the receiver usually stays with the last examined branch. The SECps is a modified version of SEC, and the significant difference between SEC and SECps is that the SECps receiver chooses the branch with the maximum SNR instead of the last examined one in SEC, only when all estimated branches are unacceptable. Thus, the SECps can be considered as PSC with an output threshold. To this end, the performance of SSC, SEC, and SECps for conventional wireless communications applications has been widely investigated over different fading environments in the past decades. However, most studies have focused on multipath fading environments, such as independent Rayleigh [1; 3; 4; 5], Rician [1; 3; 4; 5], Nakagami-m [1; 3; 4; 5], generalized gamma [7], \(\kappa\)-\(\mu\)[8], \(\eta\)-\(\mu\)[8; 9], \(\alpha\)-\(\mu\)[10], correlated Nakagami-m [11], and correlated \(\alpha\)-\(\mu\)[12] environments. Additionally, only a few papers considered shadowing channels and gamma-based composite fading channels for SSC schemes, such as correlated log-normal [13], Rayleigh-gamma [14], generalized K [15], \(\kappa\)-\(\mu\)-gamma [16], and \(\alpha\)-\(\kappa\)-\(\mu\)-gamma [17] channels. Moreover, in some emerging wireless communications applications, such as wireless body area networks and low-cost Internet of Things, SDC schemes have gained more attention again because of their simple structure and ease of implementation. For indoor off-body communication [2] and outdoor wearable communication [18], the authors considered SSC, SEC, and SECps to improve signal reliability over Nakagami-m fading channels. For non-line-of-sight ultra-ultraviolet communication in [19], an SSC diversity reception was presented to overcome the fluctuations caused by strong atmospheric turbulence in a gamma-gamma condition. After this, they further applied the SSC scheme to a blind-spectrum sensing system for multiuser ultraviolet communication in [20].