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

Abstract

We consider a multi-user two-ray ground reflection scenario with unknown distances between transmitter and receivers. By using two frequencies per user in parallel, we can mitigate possible destructive interference and ensure ultrareliability with only very limited knowledge at the transmitter. In this work, we consider the problem of assigning two frequencies to each receiver in a multi-user communication system such that the average minimum receive power is maximized. In order to solve this problem, we introduce a generalization of the quadratic multiple knapsack problem to include heterogeneous profits and develop an algorithm to solve it. Compared to random frequency assignment, we report a gain of around 6 dB in numerical simulations.

Outage Probability Calculation for Two-Ray Ground Reflection Scenarios with Frequency Diversity

“…One way to achieve this is the use of a second frequency in parallel [5]. The resulting total sum receive power P s is shown in (3) at the top of the next page.…”

“…In the following, we will consider the lower bound P s of the actual sum receive power which is shown in (4) at the top of the next page, cf. [5,Lem. 1].…”

“…In [5], the authors consider a similar scenario, where they focus on the optimization of the frequency spacing ∆ω for maximizing the minimum receive power without knowledge of the distribution of the distance d. In contrast, we assume knowledge of the distribution F d in this work, which allows us to solve the problem of calculating the outage probability for a fixed frequency spacing ∆ω.…”

Frequency Diversity for Ultra-Reliable and Secure Communications in Sub-THz Two-Ray Scenarios

“…It can be seen that there occur drops in the receive power at certain distances where the LoS and the reflected component superimpose destructively at the receiver. The location of the drops can be influenced by the choice of the frequency spacing ∆ω [19]. Additionally, the receive power decreases overall with an increasing distance due to the higher path loss.…”

QMKPy: A Python Testbed for the Quadratic Multiple Knapsack Problem

“…However, this type of problem arises in many areas of research. In addition to the typical problems in Operations Research, it also occurs in distributed computing (Rust et al, 2020) and in the area of wireless communications (Besser et al, 2022).…”