Spreading over OFDM for Integrated Sensing and Communications (ISAC) Ranging: Multi-user Interference Mitigation
Karim A. Said, Ibraheem Alturki, Husheng Li, Elizabeth Bentley, and, Lingjia Liu

TL;DR
This paper addresses mutual interference in OFDM-based integrated sensing and communication systems, proposing an orthogonal spreading method to reduce interference and improve ranging accuracy at the cost of spectral efficiency.
Contribution
It analytically characterizes inter-band interference in multi-user OFDM systems and introduces an orthogonal spreading layer to mitigate this interference.
Findings
Orthogonal spreading significantly reduces inter-band interference.
The proposed method lowers integrated sidelobe levels compared to standard OFDM.
Trade-off exists between sensing accuracy and spectral efficiency.
Abstract
In the context of communication-centric integrated sensing and communication (ISAC), the orthogonal frequency division multiplexing (OFDM) waveform was proven to be optimal in minimizing ranging sidelobes when random signaling is used. A typical assumption in OFDM-based ranging is that the max target delay is less than the cyclic prefix (CP) length, which is equivalent to performing a \textit{periodic} correlation between the signal reflected from the target and the transmitted signal. In the multi-user case, such as in Orthogonal Frequency Division Multiple Access (OFDMA), users are assigned disjoint subsets of subcarriers which eliminates mutual interference between the communication channels of the different users. However, ranging involves an aperiodic correlation operation for target ranges with delays greater than the CP length. Aperiodic correlation between signals from disjoint…
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Taxonomy
TopicsIndoor and Outdoor Localization Technologies
