Fundamental Limits of MIMO ISAC: An Antenna Array Architecture Perspective
Abstract
This paper investigates the fundamental limits of MIMO integrated sensing and communications (ISAC) systems, specifically comparing sparse arrays (SAs) against conventional uniform linear arrays (ULAs). A unified theoretical analysis of ergodic channel capacity and the Cramérunicodex2013Rao bound (CRB) for angle estimation is developed while accounting for the array geometry. Utilizing the framework of stochastic majorization, the study reveals that SAs consistently outperform ULAs by creating a more unicodex201Cuniformunicodex201D spatial eigenvalue distribution, which decorrelates the multipath environment and increases communication capacity. For sensing, the paper proves that the angle CRB is inversely proportional to the array's second-order central moment of antenna positions asymptotically, demonstrating that SAs achieve superior accuracyunicodex2014improving by up to the square of the number of antennasunicodex2014due to their increased physical aperture. These analyses and conclusions are demonstrated to be also valid for MIMO ISAC systems employed with the modern waveforms OTFS and OFDM, suggesting that spatial geometry, rather than waveform, is the primary driver of fundamental performance gains in the spatial dimension.
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BibTeX
@misc{chen2026fundamental,
title = {{Fundamental Limits of MIMO ISAC: An Antenna Array Architecture Perspective}},
author = {Po-Chih Chen and Ming-Chun Lee and Yu-Chih Huang},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2607.20200},
eprint = {2607.20200},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2607.20200},
}
RIS
TY - UNPB
TI - Fundamental Limits of MIMO ISAC: An Antenna Array Architecture Perspective
AU - Po-Chih Chen
AU - Ming-Chun Lee
AU - Yu-Chih Huang
PY - 2026
DA - 2026/09/12
PB - arXiv
DO - 10.48550/arxiv.2607.20200
UR - https://arxiv.org/abs/2607.20200
AB - This paper investigates the fundamental limits of MIMO integrated sensing and communications (ISAC) systems, specifically comparing sparse arrays (SAs) against conventional uniform linear arrays (ULAs). A unified theoretical analysis of ergodic channel capacity and the Cramérunicodex2013Rao bound (CRB) for angle estimation is developed while accounting for the array geometry. Utilizing the framework of stochastic majorization, the study reveals that SAs consistently outperform ULAs by creating a more unicodex201Cuniformunicodex201D spatial eigenvalue distribution, which decorrelates the multipath environment and increases communication capacity. For sensing, the paper proves that the angle CRB is inversely proportional to the array's second-order central moment of antenna positions asymptotically, demonstrating that SAs achieve superior accuracyunicodex2014improving by up to the square of the number of antennasunicodex2014due to their increased physical aperture. These analyses and conclusions are demonstrated to be also valid for MIMO ISAC systems employed with the modern waveforms OTFS and OFDM, suggesting that spatial geometry, rather than waveform, is the primary driver of fundamental performance gains in the spatial dimension.
ER -