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We consider an unsourced random access (URA) system enhanced with a feedback mechanism that serves both communication and sensing tasks. While traditional URA systems do not incorporate feedback, we propose a novel feedback signal design…

Information Theory · Computer Science 2025-06-26 Mohammad Javad Ahmadi , Mohammad Kazemi , Rafael F. Schaefer

Unsourced random access (URA) has emerged as a candidate paradigm for massive machine-type communication (MTC) in next-generation wireless networks. While many excellent uplink schemes have been developed for URA, these schemes do not…

Information Theory · Computer Science 2022-06-06 Jamison R. Ebert , Krishna R. Narayanan , Jean-Francois Chamberland

This work introduces security for unsourced random access (URA) by employing physical layer security techniques. To achieve confidentiality, the proposed system opportunistically exploits intrinsic features of feedback-aided URA without…

Information Theory · Computer Science 2026-03-26 Mohammad Javad Ahmadi , Rafael F. Schaefer , H. Vincent Poor

Unsourced random access (URA) is a particular form of grant-free uncoordinated random access wherein the users' identities are not associated to specific waveforms at the physical layer. Tensor-based modulation (TBM) has been recently…

Signal Processing · Electrical Eng. & Systems 2023-04-25 Alberto Rech , Alexis Decurninge , Luis G. Ordóñez

Current wireless networks are designed to optimize spectral efficiency for human users, who typically require sustained connections for high-data-rate applications like file transfers and video streaming. However, these networks are…

Information Theory · Computer Science 2025-09-30 Kirill Andreev , Pavel Rybin , Alexey Frolov

We study the problem of unsourced random access (URA) over Rayleigh block-fading channels with a receiver equipped with multiple antennas. We employ multiple stages of orthogonal pilots, each of which is randomly picked from a codebook. In…

Information Theory · Computer Science 2022-05-20 Mohammad Javad Ahmadi , Tolga M. Duman

This paper investigates the unsourced random access (URA) problem with a massive multiple-input multiple-output receiver that serves wireless devices in the near-field of radiation. We employ an uncoupled transmission protocol without…

Information Theory · Computer Science 2024-01-26 Xinyu Xie , Yongpeng Wu , Jianping An , Derrick Wing Kwan Ng , Chengwen Xing , Wenjun Zhang

Unsourced random access (URA) is a recently proposed communication paradigm attuned to machine-driven data transfers. In the original URA formulation, all the active devices share the same number of bits per packet. The scenario where…

Information Theory · Computer Science 2021-02-16 Vamsi K. Amalladinne , Allen Hao , Stefano Rini , Jean-Francois Chamberland

This paper considers an unsourced random access (URA) set-up equipped with a passive reconfigurable intelligent surface (RIS), where a massive number of unidentified users (only a small fraction of them being active at any given time) are…

Information Theory · Computer Science 2024-08-27 Mohammad Javad Ahmadi , Mohammad Kazemi , Tolga M. Duman

This paper investigates the massive random access for a huge amount of user devices served by a base station (BS) equipped with a massive number of antennas. We consider a grant-free unsourced random access (U-RA) scheme where all users…

Information Theory · Computer Science 2020-09-15 Xinyu Xie , Yongpeng Wu , Junyuan Gao , Wenjun Zhang

Multiple access communication systems enable numerous users to share common communication resources, playing a crucial role in wireless networks. With the emergence of the sixth generation (6G) and beyond communication networks, supporting…

Information Theory · Computer Science 2025-11-17 Mert Ozates , Mohammad Javad Ahmadi , Mohammad Kazemi , Deniz Gündüz , Tolga M. Duman

This paper investigates the unsourced random access (URA) scheme to accommodate numerous machine-type users communicating to a base station equipped with multiple antennas. Existing works adopt a slotted transmission strategy to reduce…

Information Theory · Computer Science 2022-02-17 Xinyu Xie , Yongpeng Wu , Jianping An , Junyuan Gao , Wenjun Zhang , Chengwen Xing , Kai-Kit Wong , Chengshan Xiao

Unsourced random access (URA) is an increasingly popular communication paradigm attuned to machine driven data transfers in \textit{Internet-of-Things} (IoT) networks. In a typical URA setting, a small subset of active devices within a very…

Information Theory · Computer Science 2021-05-06 Vamsi K. Amalladinne , Jean-Francois Chamberland , Krishna R. Narayanan

This paper explores the fundamental limits of unsourced random access (URA) with a random and unknown number ${\rm{K}}_a$ of active users in MIMO quasi-static Rayleigh fading channels. First, we derive an upper bound on the probability of…

Information Theory · Computer Science 2024-04-16 Junyuan Gao , Yongpeng Wu , Giuseppe Caire , Wei Yang , Wenjun Zhang

For the multiuser multiple-input multiple-output (MIMO) downlink channel, the users feedback their channel state information (CSI) to help the base station (BS) schedule users and improve the system sum rate. However, this incurs a large…

Information Theory · Computer Science 2011-03-22 Jin-Hao Li , Hsuan-Jung Su , Yu-Lun Tsai

We consider unsourced random access (uRA) in user-centric cell-free (CF) wireless networks, where random access users send codewords from a common codebook during specifically dedicated random access channel (RACH) slots. The system is…

Information Theory · Computer Science 2024-08-16 Eleni Gkiouzepi , Burak Çakmak , Manfred Opper , Giuseppe Caire

Unsourced random access (URA) has emerged as a pragmatic framework for next-generation distributed sensor networks. Within URA, concatenated coding structures are often employed to ensure that the central base station can accurately recover…

Information Theory · Computer Science 2021-12-02 Vamsi K. Amalladinne , Jamison R. Ebert , Jean-Francois Chamberland , Krishna R. Narayanan

We study the problem of unsourced random access (URA) over Rayleigh block-fading channels with a receiver equipped with multiple antennas. We propose a slotted structure with multiple stages of orthogonal pilots, each of which is randomly…

Information Theory · Computer Science 2023-07-17 Mohammad Javad Ahmadi , Mohammad Kazemi , Tolga M. Duman

Identification and authentication are two basic functionalities of traditional random access protocols. In ALOHA-based random access, the packets usually include a field with a unique user address. However, when the number of users is…

Unsourced random-access (U-RA) is a type of grant-free random access with a virtually unlimited number of users, of which only a certain number $K_a$ are active on the same time slot. Users employ exactly the same codebook, and the task of…

Information Theory · Computer Science 2021-12-10 Alexander Fengler , Peter Jung , Giuseppe Caire
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