Papers for

satellite communication teams

Papers whose findings have a practical use for this group, as judged from the abstract. Open a paper to read what it means in practice.

Relay channel capacity explained by three signal schemes

The Capacity of the Relay Channel

Abstract: The capacity of the relay channel is characterized by three schemes: decode-forward, coordinated compress-forward, and uncoordinated compress-forward. The proof relies entirely on properties of typical sequences.

Mon 14 SeptInformation Theory
The gist
This paper looks at how much information can be reliably sent through a relay channel, which is a way to transfer messages via an intermediate helper. The authors identify three key methods to do this efficiently: decode-forward, coordinated compress-forward, and uncoordinated compress-forward. Their proof uses the idea of typical sequences, a mathematical concept for understanding patterns in communication. This helps explain the limits of communication through relay channels.
Open → 2609.15709v1

Continuous waveform design reduces interference in communication signals

Resolving the Discontinuity of Continuous-Time AFDM Waveforms

Abstract: Continuous-time affine frequency division multiplexing (AFDM) waveforms, constructed via frequency wrapping and phase correction, are known to be sample-wise equivalent to the widely adopted discrete AFDM framework. In this paper, we uncover a fundamental and previously overlooked flaw in this construction: its complex envelope is inherently discontinuous for generic chirp parameters. We show that these discontinuities are the direct cause of the high out-of-band emission (OOBE). To resolve this issue, we propose a fundamentally different continuous-time waveform, termed stepped frequency division multiplexing (SFDM). Unlike conventional approaches that allow continuous frequency variation, SFDM freezes the instantaneous frequency at the midpoint of the underlying chirp trajectory within each Nyquist sampling interval. This design yields a complex envelope that is strictly continuous over the entire symbol duration while preserving exact sample-wise equivalence with discrete AFDM. A unified spectral analysis reveals that the superior OOBE performance of SFDM stems from the absence of internal jump discontinuities, which otherwise dominate the far-out spectral roll-off. Numerical results confirm that SFDM consistently achieves significantly lower OOBE across a wide range of chirp rates.

Mon 7 SeptInformation Theory
The gist
Communication signals need to be smooth to avoid interfering with other signals. The authors found that a common method creates sudden jumps in the waveform, causing unwanted noise outside the main signal range. They introduced a new method called SFDM that keeps the waveform smooth and continuous, which reduces this interference. Their tests show this method works better across different signal settings.
Open → 2609.07480v1