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Signal Constellation Construction via Radio Frequency Mirrors

Majid Nasiri Khormuji

TL;DR

The paper analyzes media-based modulation (MBM) using multi-state RF mirrors around a single-antenna transmitter, identifying that open-loop MBM suffers from declining minimum distance as spectral efficiency grows. It introduces a closed-loop MBM with feedback, applying complex weights $w_i$ to form the constellation $\\mathbb{S}^{(cl)} = \\{w_i h_i\\}$ under a power constraint, and optimizes these weights via a stochastic perturbation algorithm to maximize the minimum distance. Results show that closed-loop MBM markedly improves constellation regularity and distance, with SER performance approaching AWGN and notable gains over open-loop MBM, including higher-order constellations like 16-MBM. The work suggests a viable pathway for MBM-enabled reliable communications and informs future 6G design, with potential extensions to learning-based constellation shaping. $h_i \\sim \\mathcal{CN}(0,1)$ and $d_{min}$ play central roles in quantifying improvements.

Abstract

By integrating feedback with Radio Frequency (RF) mirrors, we develop a closed-loop media-based modulation system for efficient utilization of the signal space. Specifically, this closed-loop construction optimizes the inherited signal constellation from the media, achieving a significantly larger minimum pairwise Euclidean distance than the original configuration. The initial signal constellation, derived from the media, is used to compute a set of complex weights for all activation patterns of the RF mirrors. These complex weights are then fed back to the transmitter to refine the transmit signal before it reaches the mirrors. This feedback mechanism ensures that the received, shaped signal constellation retains improved properties, enabling more reliable transmission. Notably, the closed-loop approach enables the media-based modulation to approach the performance of an AWGN channel, while the channel from each mirror to the single-antenna receiver is modeled as Rayleigh fading.

Signal Constellation Construction via Radio Frequency Mirrors

TL;DR

The paper analyzes media-based modulation (MBM) using multi-state RF mirrors around a single-antenna transmitter, identifying that open-loop MBM suffers from declining minimum distance as spectral efficiency grows. It introduces a closed-loop MBM with feedback, applying complex weights to form the constellation under a power constraint, and optimizes these weights via a stochastic perturbation algorithm to maximize the minimum distance. Results show that closed-loop MBM markedly improves constellation regularity and distance, with SER performance approaching AWGN and notable gains over open-loop MBM, including higher-order constellations like 16-MBM. The work suggests a viable pathway for MBM-enabled reliable communications and informs future 6G design, with potential extensions to learning-based constellation shaping. and play central roles in quantifying improvements.

Abstract

By integrating feedback with Radio Frequency (RF) mirrors, we develop a closed-loop media-based modulation system for efficient utilization of the signal space. Specifically, this closed-loop construction optimizes the inherited signal constellation from the media, achieving a significantly larger minimum pairwise Euclidean distance than the original configuration. The initial signal constellation, derived from the media, is used to compute a set of complex weights for all activation patterns of the RF mirrors. These complex weights are then fed back to the transmitter to refine the transmit signal before it reaches the mirrors. This feedback mechanism ensures that the received, shaped signal constellation retains improved properties, enabling more reliable transmission. Notably, the closed-loop approach enables the media-based modulation to approach the performance of an AWGN channel, while the channel from each mirror to the single-antenna receiver is modeled as Rayleigh fading.

Paper Structure

This paper contains 8 sections, 1 theorem, 24 equations, 8 figures.

Table of Contents

  1. Introduction
  2. Baseline: Open-Loop MBM
  3. Minimum Distance Properties of Open-Loop MBM
  4. Closed-Loop MBM
  5. Weight Optimization Algorithm
  6. Exemplary Optimized MBM Constellations
  7. Performance Evaluations
  8. Conclusions

Key Result

Proposition 1

For the open-loop M-MBM configured with $M = 2^k$, the average minimum pairwise distance of the signal constellation is bounded as

Figures (8)

  • Figure 1: Baseline MBM transmitter with RF mirror controller.
  • Figure 2: Closed-loop MBM transmitter with feedback circuitry.
  • Figure 3: Stochastic algorithm for computing optimized weights.
  • Figure 4: Examples of 16-MBM signal point constellations showing both open-loop design and the corresponding optimized closed-loop after the configuration of the optimized weights.
  • Figure 5: SER comparison of 4-MBM with QPSK.
  • ...and 3 more figures

Theorems & Definitions (2)

  • Proposition 1
  • proof