No abstract

No abstract

Simultaneously transmitting and receiving on the same frequency has long been considered a fundamental impossibility in wireless communication. Recent research activity has sought to challenge this limit. The main challenge is dealing with very high self-interference due to the high power transmit (TX) signal leaking into the receive (RX) path. The larger the difference between the TX and RX power, the more challenging the problem. A link to a low Earth orbit (LEO) satellite requires at least 130 dB of cancellation for full duplex communication to be achievable. This paper presents initial results for a ground-LEO full-duplex link. Starting with a link budget, we derive the expected power levels, and therefore the required cancellation. We then formulate features of the satellite channel that make it feasible to even consider achieving 130 dB of cancellation. Unlike previous efforts that focused on relatively low-cost implementations suitable for commercial market, this effort relies on expensive and hand-tuned components. The initial goal is to develop a link suitable for a small LEO satellite (e.g. cubesat) with limited (1 MHz) bandwidth. The paper then provides initial experimental results using high-end RF and mixed-signal components. Cancellation is achieved using a combination of RF and baseband techniques. This paper presents the best known amount of self-interference cancellation with RF and baseband techniques. This goal is clearly ambitious and the work is not yet complete. However, the results are promising enough to warrant additional research.

No abstract

The capability to achieve high-precision positioning accuracy has been considered as one of the most critical requirements for vehicle-to-everything (V2X) services in the fifthgeneration (5G) cellular networks. The non-line-of-sight (NLOS) connectivity, coverage, reliability requirements, the minimum number of available anchors, and bandwidth limitations are among the main challenges to achieve high accuracy in V2X services. This work provides an overview of the potential solutions to provide the new radio (NR) V2X users (UEs) with high positioning accuracy in the future 3GPP releases. In particular, we propose a novel selective positioning solution to dynamically switch between different positioning technologies to improve the overall positioning accuracy in NR V2X services, taking into account the locations of V2X UEs and the accuracy of the collected measurements. Furthermore, we use high-fidelity system-level simulations to evaluate the performance gains of fusing the positioning measurements from different technologies in NR V2X services. Our numerical results show that the proposed hybridized schemes achieve a positioning error ≤ 3 m with ≈ 76% availability compared to ≈ 55% availability when traditional positioning methods are used. The numerical results also reveal a potential gain of ≈ 56% after leveraging the roadside units (RSUs) to improve the tail of the UE's positioning error distribution, i.e., worst-case scenarios, in NR V2X services.