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

本课题提出了一种新的低地球轨道卫星网络无线通信技术——Chirp置换多址（CPMA），其目标是在用户终端到卫星的上行链路上实现最小的通信延迟。低轨道卫星网络已成为补充现有无线基础设施的有力选择，特别是在向农村地区和海洋等传统上难以到达的地区提供宽带数据服务方面。CPMA解决了低轨道卫星网络中的关键挑战之一，即通信延迟，并将使自动驾驶和游戏等对延迟高度敏感的应用成为可能。CPMA通过将延迟减少到从用户终端到卫星的单向传播延迟来最小化延迟，因为CPMA允许用户终端在任何时间传输数据包，而无需相互协调或等待资源分配决策。通过实现新的应用，CPMA将造福社会，提高生活质量。该项目将促进对无线网络中免授权通信的认识和理解。这个项目的结果将与教育相结合，例如用于课程项目。将积极招收本科生和来自代表性不足和少数群体的学生。CPMA的关键新颖之处在于它的物理层，它允许卫星解码来自多个用户终端的重叠数据包，并在上行链路上实现免授权通信。CPMA通过变换啁啾波形来调制数据，啁啾波形是一个恒定幅度和线性增加频率的复矢量。变换的关键是对啁啾进行置换，有效地降低了分组间干扰的影响。本项目将对CPMA的物理层和链路层进行设计、实现和测试。物理层将通过具有经过验证的保证和多种类型的啁啾转换的排列进行优化。链路层将充分利用物理层的能力，根据多用户终端相互靠近的集体反馈，解决高效的分组重传和传输功率控制等问题。理论分析将揭示网络容量，并证明设计的最优性。CPMA有望实现超低延迟、高数据速率和高网络容量。CPMA将在usrp上实施，并在POWDER等开放平台上进行演示，并通过通道跟踪和广泛接受的通道模型驱动的模拟进行评估。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.