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AuthorShaban, Ahmed Wagdy
AuthorSeif, Mohamed
AuthorKhattab, Tamer
AuthorEl-Keyi, Amr
AuthorNafie, Mohammed
AuthorZorba, Nizar
Available date2024-07-14T07:57:20Z
Publication Date2022
Publication NameIEEE Canadian Journal of Electrical and Computer Engineering
ResourceScopus
Identifierhttp://dx.doi.org/10.1109/ICJECE.2022.3195957
ISSN26941783
URIhttp://hdl.handle.net/10576/56595
AbstractThe coexistence of communication and sensing services in the next wireless communication systems, i.e., beyond 5G and 6G systems, revive the central role of interference management techniques such as interference alignment, coordinated multipoint transmission, and cell-free massive multiple-input–multiple-output (MIMO), in defeating interference and achieving the network capacity. In this article, we consider the $K$ -user single-input–single-output (SISO) X-channel and its variants ( $2 \times K$ and $K \times 2$ ) in fast-fading environments. This can theoretically model many practical use cases for beyond 5G and 6G networks. For instance, it can model the case of having $K$ cars communicating with another $K$ cars, while former cars are sensing environment using the latter ones (in a cooperative, bistatic, and active approach) over the same time and frequency resources. We assume that the transmitters have access to synergistic alternating channel state information at the transmitter (CSIT) where it alternates between three states: perfect (P), delayed (D), and no-CSIT (N), and these states are associated with fractions of time denoted by $\lambda _{P}$ , $\lambda _{D}$ , and $\lambda _{N}$ , respectively. We develop novel degree-of-freedom (DoF) achievability schemes that exploit the synergy of the instantaneous CSIT and the delayed CSIT to retrospectively align interference in the subsequent channel uses. In particular, we show that the sum DoF of the $K$ -user SISO X-channel is at least ${2K}/{K + 1}$ , using a two-phase transmission scheme over finite symbols channel extension and under a certain distribution of the CSIT availability of $\Lambda (\lambda _{P}=({1}/{3}), \lambda _{D}= ({1}/{3}), \lambda _{N}=({1}/{3}))$ . This achievability result can be considered as a tight lower bound where it coincides with the best lower bound known for the same network but with partial output feedback instead of alternating CSIT. In addition, it shows that the role of synergistically alternating CSIT with distribution $\Lambda ({1}/{3},{1}/{3},{1}/{3})$ is equivalent to the one of the partial output feedback. Moreover, we show the optimality of the proposed two-phase-based scheme using a simple combinatorial proof. This establishes a DoF lower bound, which is strictly better than the best lower bound known for the case of delayed CSI for all values of $K$ . Thus, the proposed schemes offer higher DoF gain in comparison to delayed CSIT and no-CSIT.
SponsorManuscript received 7 February 2022; revised 10 June 2022; accepted 13 July 2022. Date of publication 7 November 2022; date of current version 9 November 2022. This research work was made possible by support from the Qatar National Research Fund (QNRF), a member of the Qatar Foundation (QF), under Grant No. AICC03-0530-200033. The work of Prof. Zorba was supported by Qatar University Grant QUHI-CENG-21/22-1. Open Access funding provided by the Qatar National Library. The statements made herein are the sole responsibility of the authors. (Corresponding author: Nizar Zorba.) Ahmed Wagdy Shaban is with the Department of Electrical and Computer Engineering, University of Waterloo, Waterloo, ON N2L 3G1, Canada (e-mail: ahmed.w.shaban@uwaterloo.ca). Mohamed Seif is with the Department of Electrical and Computer Engineering, Princeton University, Princeton, NJ 08544 USA (e-mail: mseif@princeton.edu).
Languageen
PublisherIEEE Canada
Subject6G communications
degrees of freedom (DoF)
joint communications and sensing
multiple-input-multiple-output (MIMO) communication
precoding
TitleOn the DoF of X-Networks With Synergistic Alternating CSIT: A Step Towards Integrated Communication and Sensing
TypeArticle
Pagination199-214
Issue Number3
Volume Number45
dc.accessType Open Access


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