The Title of the Paper

Channel side information (CSI) information varies very fast in the millimeter wave radio frequencies so its coherent time is much smaller than that of the CSI in low-frequencies (about 6 GHz or below) under the same mobility conditions. Further, when the feedback channels, regardless of being wireless or wireline, have a backhaul / transmission delay which is practically so much higher than the coherent time of the CSI in the millimeter wave radio frequencies. As such in practical scenarios, the CSI will be inherently changed in the fading environment before successfully reaches to the central entity (CE) through feedback channels, which specifically means that the CSI reached at the CE certainly becomes inaccurate, and therefore the CSI cannot be promptly and successfully used for relay selection protocols (RSPs). Correspondingly, the system performance drastically deteriorates. However, the shadowing side information (SSI) varies more slowly such that its coherent time is substantially greater than both that of the CSI and backhaul / transmission delays in feedback channels. Within this concept to circumvent these undesirable limitations, we suggest in this paper that some performance gain can be still obtained utilizing only the SSI for RSPs. In contrast to the other RSPs available in the literature, we propose a partial-RSP in dual-hop amplify-and-forward relaying system utilizing only the SSI of the relay terminals instead of their CSI. Furthermore, we offer a unified and generic performance expression of the proposed partial-RSP, spontaneously combining the analyzes of the average bit error probability, ergodic capacity, and moment generating function as a single analysis. Finally, as an illustration of the mathematical formalism, some numerical and simulation results are carried out for the generalized composite fading environments whose fading envelope follows extended generalized-K distribution, and these numerical and simulation results are shown to be in perfect agreement.