A multi-beam low-earth orbit leo satellite delivers widespread coverage by forming spot beams that tessellate cells on the surface of the Earth. In doing so, co-channel interference manifests between cells when reusing frequency spectrum across spot beams. To permit forecasting of such multi-beam satellite communication system performance, this work characterizes desired and interference signal powers under the Shadowed Rician (SR) sky-to-ground channel model, along with SNR, INR, SIR, and SINR. Specifically, we present a framework for analyzing system performance by capitalizing on the fact that the desired and interfering signals travel along almost the same path in such multi-beam satellite systems. We then introduce a minor approximation on the fading order of SR channels that significantly simplifies the probability distribution function and cumulative distribution function of these quantities and facilitates performance analyses of LEO satellite systems. We conclude this paper with an evaluation of multi-beam LEO satellite communication in SR channels of varying intensity with shadowing parameters fitted from existing measurements. Our numerical results highlight the effect satellite elevation angle has on SNR, INR, and SINR, which brings attention to the variability in system state and potential performance as a satellite traverses across the sky along its orbit.

Full-duplex millimeter wave (mmWave) communication has shown increasing promise for self-interference cancellation via hybrid precoding and combining. This paper proposes a novel mmWave multiple-input multiple-output (MIMO) design for configuring the analog and digital beamformers of a full-duplex transceiver. This work is the first to holistically consider the key practical constraints of analog beamforming codebooks, a minimal number of radio frequency (RF) chains, limited channel knowledge, beam alignment, and a limited receive dynamic range. To prevent self-interference from saturating receive components, such as LNAs and ADCs, a design framework is developed that limits the degree of self-interference on a per-antenna and per-RF chain basis. We present a means for constructing analog beamforming candidates from beam alignment measurements to afford our design greater flexibility in its aim to reduce self-interference. Numerical results evaluate the design in a variety of settings and validate the need to prevent receiver-side saturation. These results and corresponding insights serve as useful design references and benchmarks for practical full-duplex mmWave transceivers.

This work develops LONESTAR, a novel enabler of full-duplex millimeter wave (mmWave) communication systems through the design of analog beamforming codebooks. LONESTAR codebooks deliver high beamforming gain and broad coverage while simultaneously reducing the self-interference coupled by transmit and receive beams at a full-duplex mmWave transceiver. Our design framework accomplishes this by tolerating some variability in transmit and receive beamforming gain to strategically shape beams that reject self-interference spatially while accounting for digitally-controlled analog beamforming networks and self-interference channel estimation error. By leveraging the coherence time of the self-interference channel, a mmWave system can use the same LONESTAR design over many time slots to serve several downlink-uplink user pairs in a full-duplex fashion without the need for additional self-interference cancellation. Compared to those using conventional codebooks, full-duplex mmWave systems employing LONESTAR codebooks can mitigate higher levels of self-interference, tolerate more cross-link interference, and demand lower SNRs in order to outperform half-duplex operation—all while supporting beam alignment. This makes LONESTAR a potential standalone solution for enabling simultaneous transmission and reception in mmWave systems, from which it derives its name.

Modern millimeter wave (mmWave) communication systems rely on beam alignment to deliver sufficient beamforming gain to close the link between devices. We present a novel beam selection methodology for multi-panel, full-duplex mmWave systems, which we call Steer, that delivers high beamforming gain while significantly reducing the full-duplex self-interference coupled between the transmit and receive beams. Steer does not necessitate changes to conventional beam alignment methodologies nor additional over-the-air feedback, making it compatible with existing cellular standards. Instead, Steer uses conventional beam alignment to identify the general directions beams should be steered, and then it makes use of a minimal number of self-interference measurements to jointly select transmit and receive beams that deliver high gain in these directions while coupling low self-interference. We implement Steer on an industry-grade 28 GHz phased array platform and use further simulation to show that full-duplex operation with beams selected by Steer can notably outperform both half-duplex and full-duplex operation with beams chosen via conventional beam selection. For instance, Steer can reliably reduce self-interference by more than 20 dB and improve SINR by more than 10 dB, compared to conventional beam selection. Our experimental results highlight that beam alignment can be used not only to deliver high beamforming gain in full-duplex mmWave systems but also to mitigate self-interference to levels near or below the noise floor, rendering additional self-interference cancellation unnecessary with Steer.

This work provides a rigorous assessment of the feasibility of spectrum sharing between large low-earth orbit (LEO) satellite constellations. For concreteness, we focus on the existing Starlink system and the soon-to-be-launched Kuiper system, the latter of which is prohibited from inflicting excessive interference onto incumbent Starlink ground users. We carefully model and study the potential downlink interference between the two systems at 20 GHz and investigate how strategic satellite selection may be used by Kuiper to serve its own ground users while also protecting Starlink ground users. We then extend this notion of satellite selection to the case where Kuiper has limited knowledge of Starlink’s serving satellite. Throughout our analysis, we examine the distribution of interference and SINR over time as each constellation orbits the globe. Our findings reveal that there is virtually always the potential for very high or extremely low interference, depending on which Starlink and Kuiper satellites are being used to serve their ground users. Consequently, we show that Kuiper can protect Starlink ground users, with high probability, by strategically selecting which of its satellites are used to serve its ground users. Simultaneously, Kuiper is capable of delivering near-maximal downlink SINR to its own ground users. This highlights a potential feasible route to the coexistence of two dense LEO satellite systems, even in scenarios where one system has limited knowledge of the other’s serving satellites.

In recent years, there has been extensive research on millimeter-wave (mmWave) communication and on in-band full-duplex (FD) communication, but work on the combination of the two is relatively lacking. FD mmWave systems could offer increased spectral efficiency and decreased latency while also suggesting the redesign of existing mmWave applications. While FD technology has been well- explored for sub-6 GHz systems, the developed methods do not translate well to mmWave. This turns us to a method called beamforming cancellation (BFC), where the highly directional mmWave beams are steered to mitigate self-interference (SI) and enable simultaneous transmission and reception in- band. In this paper, we present BFC designs for two fully-connected hybrid beamforming scenarios, both of which sufficiently suppress the SI such that the sum spectral efficiency approaches that of a SI- free FD system. A simulation and its results are then used to verify our designs.