Current-Future Rate Tradeoffs in ISAC Under Random Path Changes

Hang Ruan; Zhaofeng Liu; Taneli Riihonen

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arXiv · 2611.04798

Current-Future Rate Tradeoffs in ISAC Under Random Path Changes

Hang Ruan·Zhaofeng Liu·Taneli Riihonen

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Abstract

In mobile wireless links, motion changes path directions and visibility, and blockage can shift communication to a different propagation path. Integrated sensing and communication (ISAC) allows a base station (BS) to use echoes of data transmissions to monitor these changes and guide subsequent beam selection. Illuminating objects that govern future path availability may reduce the beamforming gain on the current communication route. Existing sensing-communication tradeoffs and dynamic beam-control frameworks do not directly quantify the future communication gain from this current-rate sacrifice. We quantify sensing value by the future-rate gain enabled by echo-adaptive beam selection. We derive explicit expressions for the future communication gain and the net gain after accounting for the current-rate loss. The analysis uses a coupled communication-echo channel with binary-state Markov motion over a finite burst informed by one processed echo. We show that monitoring is worthwhile when its future-rate gain exceeds the current loss, while more informative observations yield zero additional future rate if they cannot change any future optimal beam. We derive interpretable gain bounds exposing the roles of improved scene discrimination, motion memory and future beam-rate differences. Reciprocal-channel tests demonstrate positive net accumulated-rate gains from monitoring a moving blocker during reflected-path service, including continuous position uncertainty.

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Hang Ruan, Zhaofeng Liu, Taneli Riihonen. 2026-11-03. Current-Future Rate Tradeoffs in ISAC Under Random Path Changes. https://arxiv.org/abs/2611.04798

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