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A general framework for computing by digital communication

Time: Mon 2023-11-20 13.00

Location: E32, Osquars backe 2, E-huset, huvudbyggnaden, Lindstedtsvägen 3, floor 3

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Language: English

Subject area: Telecommunication

Doctoral student: Saeed Razavikia , Nätverk och systemteknik

Opponent: Professor Deniz Gunduz, Imperial College, London, UK

Supervisor: Professor Carlo Fischione, Nätverk och systemteknik; Assistant professor José Mairton Barros da Silva Jr., Division of Computer Systems, Uppsala University, Uppsala, Sweden

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QC 20231031


The imminent Internet of Things, fueled by 6G networks and machine learning technologies, is set to shift wireless communication to machine-centric paradigms, revolutionizing sectors such as healthcare or industrial automation through efficient data handling. However, this connectivity boom poses challenges, including straining existing communication systems due to increased data traffic and computational demands.

Over-the-air computation (OAC) presents a feasible solution, allowing the summation of transmitted signals at a common receiver through analog amplitude modulation. Designed to enable concurrent data collection and computation at the network edge, OAC seeks to lessen the central system burden, reducing latency and energy usage while enabling real-time analytics. This approach is particularly beneficial for federated learning, a machine learning technique that operates across decentralized devices. However, OAC's dependence on analog communication poses notable challenges, including signal distortion during transmission and the limited availability of devices supporting analog modulations. Digital modulation is a preferable alternative, recognized for its excellent channel correction capabilities and broad acceptance in modern wireless devices. Nevertheless, its integration into OAC is perceived as a significant hurdle, with overlapping digitally modulated signals threatening the fundamental concept of simultaneous data collection and computation.

The first part of the thesis provides an overview of communication systems, specifically focusing on the relevant OAC methodologies for analog and digital parts and their application in ML, particularly in training federated learning models. Subsequently, an exhaustive literature review concerning analog OAC techniques is undertaken, identifying existing limitations within this domain. The central thrust of our research is then introduced, proposing an innovative digital OAC approach along with a fresh perspective on the communication systems models designed for executing the computation. The chapter concludes with a summary of the principal contributions of each paper included within the thesis.

In the second part, we introduce ChannelComp, a groundbreaking computing approach compatible with current digital communication systems, including smartphones and IoT devices. A detailed analysis of ChannelComp's functions reveals how it enables digital modulation schemes to perform computations, addressing a critical gap in previous research. Moreover, introducing pre-coders designed for function computation over the multiple access channel, combined with a feasibility optimization problem framework, allows for seamless integration with current systems. Compared to OAC, restricted to analog modulations, ChannelComp exhibits broader computational capabilities and adherence to strict computation time constraints, thus showcasing its robust potential for future massive machine-type communications. This innovative method signifies a promising direction toward sustainable and efficient future wireless communication.