On the Fundamental Tradeoff of Integrated Sensing and Communications Under Gaussian Channels

By Yifeng Xiong, F. Liu, Yuanhao Cui, Weijie Yuan, T. Han, Giuseppe Caire. IEEE Transactions on Information Theory, 2022

415 citations recorded by the source corpus.

Integrated Sensing and Communication (ISAC) is recognized as a promising technology for the next-generation wireless networks, which provides significant performance gains over individual sensing and communications (S&C) systems via the shared use of wireless resources. The characterization of the S&C performance tradeoff is at the core of the theoretical foundation of ISAC. In this paper, we consider a point-to-point (P2P) ISAC model under vector Gaussian channels, and propose to use the Cramér-Rao bound (CRB)-rate region as a basic tool for depicting the fundamental S&C tradeoff. In particular, we consider the scenario where a unified ISAC waveform is emitted from a dual-functional ISAC transmitter (Tx), which simultaneously communicates information to a communication receiver (Rx) and senses targets with the help of a sensing Rx. In order to perform both S&C tasks, the ISAC waveform is required to be random to convey communication information, with realizations being perfectly known at both the ISAC Tx and the sensing Rx as a reference sensing signal as in typical radar systems. In this context, we treat the ISAC waveform as a random but known nuisance parameter in the sensing signal model, and define a Miller-Chang type CRB for the analysis of the sensing performance. As the main contribution of this paper, we characterize the S&C performance at the two corner points of the CRB-rate region, namely, $P_{\mathrm{ SC}}$ indicating the maximum achievable communication rate constrained by the minimum CRB, and $P_{\mathrm{ CS}}$ indicating the minimum achievable CRB constrained by the maximum communication rate. In particular, we derive the high-SNR communication capacity at $P_{\mathrm{ SC}}$ , and provide lower and upper bounds for the sensing CRB at $P_{\mathrm{ CS}}$ . We show that these two points can be achieved by the conventional Gaussian signalling and a novel strategy relying on the uniform distribution over the set of semi-unitary matrices, i.e., the Stiefel manifold, respectively. Based on the above-mentioned analysis, we provide an outer bound and various inner bounds for the achievable CRB-rate regions. Our main results reveal a two-fold tradeoff in ISAC systems, consisting of the subspace tradeoff (ST) and the deterministic-random tradeoff (DRT) that depend on the resource allocation and data modulation schemes employed for S&C, respectively. Within this framework, we examine the state-of-the-art ISAC signalling strategies and study a number of illustrative examples, which are validated through numerical simulations.

Subfields: Aerospace Engineering, Computer Networks and Communications, Electrical and Electronic Engineering

View Paper: https://www.semanticscholar.org/paper/ed4e132afb4f0b99642aec163a94802c9d9b5e0f

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In Aerospace Engineering

  1. Yuanhao Cui
  2. Weijie Yuan
  3. Nuria González-Prelcic

In Computer Networks and Communications

  1. Nuria González-Prelcic
  2. Jia Zhu
  3. Yuanhao Cui
  4. Weijie Yuan

In Electrical and Electronic Engineering

  1. Nuria González-Prelcic
  2. Jia Zhu
  3. Yuanhao Cui
  4. Weijie Yuan
  5. Ahmed Alkhateeb

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