Contribution of non‐orthogonal multiple access signalling to practical multibeam satellite deployments

This work explores the contribution of non-orthogonal multiple access (NOMA) signalling to improve some relevant metrics of a multibeam satellite downlink. Users are paired to exploit signal-to-noise ratio (SNR) imbalances coming from the coexistence of different types of terminals, and they can be flexibly allocated to the beams, thus relaxing the cell boundaries of the satellite footprint. Different practical considerations are accommodated, such as a spatially non-uniform traffic demand, non-linear amplification effects and the use of the DVB-S2X air interface. Results show how higher traffic volumes can be channelized by the satellite, thanks to the additional bit rates which are generated for the strong users under the superposition of signals, with carefully designed power levels for DVB-S2X modulation and coding schemes in the presence of non-linear impairments.Agencia Estatal de Investigación | Ref. PID2019-105717RB-C21Agencia Estatal de Investigación | Ref. PDC2021-120959-C22Xunta de GaliciaUniversidade de Vigo/CISU

Constellation design for future communication systems: a comprehensive survey

[EN] The choice of modulation schemes is a fundamental building block of wireless communication systems. As a key component of physical layer design, they critically impact the expected communication capacity and wireless signal robustness. Their design is also critical for the successful roll-out of wireless standards that require a compromise between performance, efficiency, latency, and hardware requirements. This paper presents a survey of constellation design strategies and associated outcomes for wireless communication systems. The survey discusses their performance and complexity to address the need for some desirable properties, including consistency, channel capacity, system performance, required demapping architecture, flexibility, and independence. Existing approaches for constellation designs are investigated using appropriate metrics and categorized based on their theoretical algorithm design. Next, their application to different communication standards is analyzed in context, aiming at distilling general guidelines applicable to the wireless building block design. Finally, the survey provides a discussion on design directions for future communication system standardization processes.This work was supported in part by the Basque Government under Grant IT1234-19, in part by the PREDOC under Program PRE_2020_2_0105, and in part by the Spanish Government through the Project PHANTOM (MCIU/AEI/FEDER, UE) under Gran

RAN Functional Splits in NTN: Architectures and Challenges

While 5G networks are already being deployed for commercial applications, Academia and industry are focusing their effort on the development and standardization of the next generations of mobile networks, i.e., 5G-Advance and 6G. Beyond 5G networks will revolutionize communications systems providing seamless connectivity, both in time and in space, to a unique ecosystem consisting of the convergence of the digital, physical, and human domains. In this scenario, NonTerrestrial Networks (NTN) will play a crucial role by providing ubiquitous, secure, and resilient infrastructure fully integrated into the overall system. The additional network complexity introduced by the third dimension of the architecture requires the interoperability of different network elements, enabled by the disaggregation and virtualization of network components, their interconnection by standard interfaces and orchestration by data-driven network artificial intelligence. The disaggregation paradigm foresees the division of the radio access network in different virtualized block of functions, introducing the concept of functional split. Wisely selecting the RAN functional split is possible to better exploit the system resources, obtaining costs saving, and to increase the system performances. In this paper, we firstly provide a discussion of the current 6G NTN development in terms of architectural solutions and then, we thoroughly analyze the impact of the typical NTN channel impairments on the available functional splits. Finally, the benefits of introducing the dynamic optimization of the functional split in NTN are analyzed, together with the foreseen challenges

Uncoded space-time labeling diversity with three transmit antennas: symbol mapping designs and error performance analysis.

Doctoral Degrees. University of KwaZulu-Natal, Durban.Abstract available in PDF.Publications on page iii

Dual polarized modulation and reception for next generation mobile satellite communications

This paper presents the novel application of polarized modulation (PMod) for increasing the throughput in mobile satellite transmissions. One of the major drawbacks in mobile satellite communications is the fact that the power budget is often restrictive, making it unaffordable to improve the spectral efficiency without an increment of transmitted power. By using dual polarized antennas in the transmitter and receiver, the PMod technique achieves an improvement in throughput of up to 100% with respect to existing deployments, with an increase of less than 1 dB at low Eb/N0 regime. Additionally, the proposed scheme implies minimum hardware modifications with respect to the existing dual polarized systems and does not require additional channel state information at the transmitter; thus it can be used in current deployments. Demodulation (i.e., detection and decoding) alternatives, with different processing complexity and performance, are studied. The results are validated in a typical mobile interactive scenario, the newest version of TS 102 744 standard [Broadband Global Area Network (BGAN)], which aims to provide interactive mobile satellite communications.Peer ReviewedPostprint (author's final draft