On Fading Channel Dependency Structures with a Positive Zero-Outage Capacity

Abstract

With emerging technologies like 6G, many new applications like autonomous systems evolve which have strict demands on the reliability of data communications. In this work, we consider a system with multiple slowly fading channels that constitute a diversity system. We show that the joint distribution of the fading coefficients has a tremendous impact on the outage performance of a communication system. In particular, we investigate the zero-outage capacity (ZOC) and characterize the joint fading distributions with a strictly positive ZOC. Interestingly, the set of joint distributions, that lead to positive ZOCs, is larger than a singleton in general. We also derive expressions for the maximum ZOC with respect to all possible joint distributions for selection combining (SC) as diversity combining technique at the receiver. For maximum ratio combining (MRC), we characterize the maximum ZOC within a finite number of bits. Finally, the results are evaluated explicitly for the special cases of Rayleigh fading and Nakagami-m fading in order to quantify the ZOCs for common fading models.

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“…The above observation implies that we can achieve a positive ZOC by constantly changing the N RIS phases independently. This is an interesting phenomenon since the ZOC is zero for the typically considered slow-fading channels with independent fading, e.g., multi-antenna systems with independent Rayleigh fading [16].…”

Multi-User Frequency Assignment for Ultra-Reliable mmWave Two-Ray Channels

“…Among others, it has been observed that negative dependency between channel gains can significantly improve reliability [3]- [5]. The basic idea is to establish diversity and ensure that always one communication link is available, if the others fail.…”