Integrated Sensing and Communication Waveform Design: A Survey

Abstract

Integrated sensing and communication (ISAC) has been widely recognized as a key technology in future sixth-generation (6G) wireless networks, especially for emerging applications and scenarios demanding both high-performance sensing and communication functionalities. The ISAC technique has the potential of enabling sensing and communication functionalities in a single hardware platform, even sharing the same waveform, thus, achieving the reduced cost of hardware implementation and the efficient use of spectrum resources. In this paper, we commence with the discussion on sensing and communication at the current stage from the view of motivations, applications, and challenges. Then, we provide a comprehensive survey of the state-of-the-art approaches to the ISAC technique from the waveform design perspective. To be specific, we classify the waveform design methods into three categories, namely, communicationcentric waveform design, sensing-centric waveform design, and joint waveform optimization and design. In addition, potential research directions and challenges for future ISAC waveform design are outlined.INDEX TERMS 6G, integrated sensing and communication, communication-centric waveform design, sensing-centric waveform design, joint waveform optimization and design.

Sensing Using Coded Communications Signals

“…denote the (discrete) time-domain representation of the common ISAC waveform transmitted by the i-th TX/radar, which can be interpreted as a collection of M signals, each of length N -i.e., {x (i) 1], and so on, as shown in Fig. 2a 2 .…”

“…1a). The former is the interference experienced at RX i due to the transmissions of TX j(̸ = i), while the latter is the interference at radar receiver i (colocated with TX i) due to the transmissions of TX/radar j(̸ = i) 1 . In general, the two types of interference are distinct in their profiles, and we are especially interested in cases where the sensing interference dominates the communications interference.…”

“…(iv) The c.c.s blocks, s (1) [n, m] and s (2) [n, m] -transmitted by TX 1 and TX 2, respectively -are obtained from a rate 120/1024 Polar code, followed by QPSK modulation. The corresponding message blocks, u (1) [n, m] and u (2) [n, m], are mutually independent. Finally, the SNR w.r.t to the near target is 0dB.…”

“…In this regard, the waveform used for each of the functionalities is a crucial aspect of system design. Broadly, there are two paradigms of waveform design for ISAC systems (see [1] for a comprehensive survey): a) Separate waveforms: Such an approach allows commercial stakeholders, who may have expertise in either communications or sensing but not both, to continue to independently design their hardware and systems, based on the desirable waveform properties for each functionality (e.g., FMCW for radar and OFDM for communications). The individual waveforms can either be transmitted orthogonally [2], [3] or superimposed [4]- [7], provided the mutual interference is effectively mitigated.…”

“…This is true for any linear code, and does not require systematic encoding (i.e., Assumption 2) 17. Strictly speaking, the convergence is to a scaled δ-function, with the scaling factor equal to the average symbol power; see(1).10 VOLUME ,…”