NeTS: Small: Low Latency Uplink Communications in Low Earth Orbit (LEO) Satellite Networks with Chirp Permutation Multiple Access (CPMA)

Florida State University, Tallahassee FL

Investigators

Abstract

In this project, Chirp Permutation Multiple Access (CPMA) is proposed, which is a novel wireless communication technology for Low-Earth-Orbit (LEO) satellite networks aiming at achieving minimum communication latency on the uplink from the user terminals to the satellite. LEO satellite networks have emerged as a strong option to complement the existing wireless infrastructure, especially for providing broadband data services to areas that are traditionally difficult to reach, such as rural areas and oceans. CPMA addresses one of the key challenges in LEO satellite networks, namely, the communication latency, and will enable applications that are highly sensitive to latency, such as automatic driving and gaming. CPMA minimizes latency by reducing it to the one-way propagation delay from the user terminal to the satellite, because CPMA allows user terminals to transmit packets at any time without coordinating with each other or waiting for decisions on resource allocations. By enabling novel applications, CPMA will benefit society and improve quality of life. This project will advance the knowledge and understanding on grant-free communications in wireless networks. Results from this project will be integrated with education, such as used in course projects. Undergraduate students and students from underrepresented and minority groups will be actively recruited. The key novelty of CPMA is its physical layer, which allows the satellite to decode overlapping packets from multiple user terminals and enables grant-free communications over the uplink. The CPMA modulates data by transforming the chirp waveform, which is a complex vector with constant magnitude and linearly increasing frequency. The key transformation is the permutation of the chirp, which can effectively reduce the impact of interference across packets. In this project, both the physical layer and the link layer of CPMA will be designed, implemented, and tested. The physical layer will be optimized with permutations with proven guarantees and multiple types of transformations of the chirp. The link layer will fully harness the capabilities of the physical layer and solve problems such as efficient packet retransmission and transmission power control based on collective feedback from multiple user terminals close to each other. Theoretical analysis will be conducted to reveal the network capacity and prove the optimality of the design. CPMA is expected to achieve ultra-low latency, high data rate, and high network capacity. CPMA will be implemented on USRPs and demonstrated in open platforms such as POWDER, as well as evaluated with simulations driven by channel traces and widely accepted channel models. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.