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Unsourced random access (URA) is a recently proposed multiple access paradigm tailored to the uplink channel of machine-type communication networks. By exploiting a strong connection between URA and compressed sensing, the massive multiple…

Information Theory · Computer Science 2022-06-28 Jamison R. Ebert , Vamsi K. Amalladinne , Stefano Rini , Jean-Francois Chamberland , Krishna R. Narayanan

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 2021-01-11 Alexander Fengler , Peter Jung , Giuseppe Caire

We consider the problem of unsourced random access (U-RA), a grant-free uncoordinated form of random access, in a wireless channel with a massive MIMO base station equipped with a large number $M$ of antennas and a large number of wireless…

Information Theory · Computer Science 2020-05-21 Alexander Fengler , Saeid Haghighatshoar , Peter Jung , Giuseppe Caire

We consider the unsourced random access problem with multiple receivers and propose a cell-free type solution for that. In our proposed scheme, the active users transmit their signals to the access points (APs) distributed in a geographical…

Emerging Technologies · Computer Science 2025-01-20 Mert Ozates , Mohammad Kazemi , Eduard Jorswieck , Deniz Gunduz

Massive machine-type communications (mMTC) demand robust solutions to support extensive connectivity efficiently. Unsourced random access (URA) has emerged as a promising approach, delivering high spectral and energy efficiency. Among URA…

Information Theory · Computer Science 2025-12-25 Liandong Hu , Jian Dang , Zaichen Zhang

The core requirement of massive Machine-Type Communication (mMTC) is to support reliable and fast access for an enormous number of machine-type devices (MTDs). In many practical applications, the base station (BS) only concerns the list of…

Information Theory · Computer Science 2022-01-03 Jingze Che , Zhaoyang Zhang , Zhaohui Yang , Xiaoming Chen , Caijun Zhong , Derrick Wing Kwan Ng

In this work, we discuss the problem of unsourced random access (URA) over a Gaussian multiple access channel (GMAC). To address the challenges posed by emerging massive machine-type connectivity, URA reframes multiple access as a…

Information Theory · Computer Science 2025-05-06 Zhentian Zhang , Mohammad Javad Ahmadi , Jian Dang , Kai-Kit Wong , Zaichen Zhang , Christos Masouros

In this paper, we design a novel two-phase unsourced random access (URA) scheme in massive multiple input multiple output (MIMO). In the first phase, we collect a sequence of information bits to jointly acquire the user channel state…

Information Theory · Computer Science 2023-06-28 Jia-Cheng Jiang , Hui-Ming Wang

This work considers the problem of integrated sensing and communications (ISAC) with a massive number of unsourced and uncoordinated users. In the proposed model, known as the unsourced ISAC system (UNISAC), all active communication and…

Information Theory · Computer Science 2026-04-21 Mohammad Javad Ahmadi , Rafael F. Schaefer , H. Vincent Poor

We put forward a new algorithmic solution to the massive unsourced random access (URA) problem, by leveraging the rich spatial dimensionality offered by large-scale antenna arrays. This paper makes an observation that spatial signature is…

Information Theory · Computer Science 2020-09-16 Volodymyr Shyianov , Faouzi Bellili , Amine Mezghani , Ekram Hossain

We investigate fully asynchronous unsourced random access (URA), and propose a high-performing scheme that employs on-off division multiple access (ODMA). In this scheme, active users distribute their data over the transmit block based on a…

Signal Processing · Electrical Eng. & Systems 2025-04-16 Mert Ozates , Mohammad Kazemi , Gianluigi Liva , Deniz Gündüz

Unsourced random access (URA) has emerged as a promising paradigm for enabling massive connectivity in Internet-of-Things (IoT) networks. However, since URA transmissions do not contain device identifiers, the receiver may not associate…

Signal Processing · Electrical Eng. & Systems 2026-05-19 Wenbo Fan , Zeping Sui , Yuhei Takahashi , Jun Cheng , Zilong Liu , Pingzhi Fan

We investigate the unsourced random access scheme assuming that the base station is equipped with multiple antennas, and propose a high-performing solution utilizing on-off-division multiple access. We assume that each user spreads its…

Information Theory · Computer Science 2024-06-11 Mert Ozates , Mohammad Kazemi , Tolga M. Duman

This paper is a tutorial introduction to the field of unsourced multiple access (UMAC) protocols. We first provide a historical survey of the evolution of random access protocols, focusing specifically on the case in which uncoordinated…

Information Theory · Computer Science 2024-08-20 Gianluigi Liva , Yury Polyanskiy

We consider unsourced random access (uRA) in a cell-free (CF) user-centric wireless network, where a large number of potential users compete for a random access slot, while only a finite subset is active. The random access users transmit…

Information Theory · Computer Science 2025-05-01 Burak Çakmak , Eleni Gkiouzepi , Manfred Opper , Giuseppe Caire

Massive machine-type communications (mMTC) or massive access is a critical scenario in the fifth generation (5G) and the future cellular network. With the surging density of devices from millions to billions, unique pilot allocation becomes…

Information Theory · Computer Science 2025-04-03 Zhentian Zhang , Jian Dang , Zaichen Zhang , Liang Wu , Bingcheng Zhu , Lei Wang

In this paper, we explore an efficient uncoupled unsourced random access (UURA) scheme for 6G massive communication. UURA is a typical framework of unsourced random access that addresses the problems of codeword detection and message…

Information Theory · Computer Science 2024-05-07 Feiyan Tian , Xiaoming Chen , Chongwen Huang , Zhaoyang Zhang

In this paper, we propose a novel fully Bayesian approach for the massive multiple-input multiple-output (MIMO) massive unsourced random access (URA). The payload of each user device is coded by the sparse regression codes (SPARCs) without…

Information Theory · Computer Science 2023-06-28 Jia-Cheng Jiang , Hui-Ming Wang

We examine unsourced random access in a fully asynchronous setup, where active users transmit their data without restriction on the start time over a fading channel. In the proposed scheme, the transmitted signal consists of a pilot…

Information Theory · Computer Science 2025-12-23 Mert Ozates , Mohammad Kazemi , Gianluigi Liva , Deniz Gündüz

This paper considers the unsourced random access (URA) problem with a random and unknown number of active users in multiple-input multiple-output (MIMO) quasi-static Rayleigh fading channels. We derive non-asymptotic achievability bounds on…

Information Theory · Computer Science 2025-03-24 Junyuan Gao , Yongpeng Wu , Giuseppe Caire , Wei Yang , H. Vincent Poor , Wenjun Zhang