T. Rossi

EHF for Satellite Communications: The New Broadband Frontier

The exploitation of extremely high-frequency (EHF) bands (30-300 GHz) for broadband transmission over satellite links is currently a hot research topic. In particular, the Q-V band (30-50 GHz) and W-band (75-110 GHz) seem to offer very promising perspectives. This paper aims at presenting an overview of the current status of research and technology in EHF satellite communications and taking a look at future perspectives in terms of applications and services. Challenges and open issues are adequately considered together with some viable solutions and future developments. The proposed analysis highlighted the need for a reliable propagation model based on experimental data acquired in orbit. Other critical aspects should be faced at the PHY-layer level in order to manage the tradeoff between power efficiency, spectral efficiency, and robustness against link distortions. As far as networking aspects are concerned, the large bandwidth availability should be converted into increased throughput by means of suitable radio resource management and transport protocols, able to support very high data rates in long-range aerospace scenarios.

Experimental Missions in W -Band: A Small LEO Satellite Approach

W-band (75-110 GHz) is proposed nowadays as a valuable alternative to intensively-exploited Ku- and Ka-bands for high-speed transmission over satellite networks. In such a framework, some experiments are being carried out, which are targeted to verify the feasibility of exploitation of W-band for broadband service deployment. From a theoretical viewpoint, the large bandwidth availability and the scarce amount of interference typical of W-band should guarantee high capacities. Nevertheless, many crucial aspects are still to be carefully investigated, e.g., signal propagation issues, RF impairments, choice of modulation and coding, efficient antenna design, etc. In this paper, an overview is made on the low Earth orbit (LEO) nano-satellite mission in-orbit key-test and validation of W-band (IKNOW). IKNOW mission is an ongoing advanced feasibility study part of an Italian Space Agency Project, named W-band analysis and verification (WAVE), coordinated by the Department of Electronic Engineering, University of Rome ldquoTor Vergatardquo. The main objective of the IKNOW mission is to tackle some of the unexplored critical aspects concerning W-band satellite transmission. In such a perspective, IKNOW should be regarded as a ldquopilot mission,rdquo whose results will be used for a first uplink-downlink satellite channel characterization, in-orbit validation of W-band technology, and space qualification processes. This paper is focused on the research work carried out in a preliminary phase of the IKNOW study and will also consider a number of elements related to the mission configuration, payload architecture, link analysis, potential RF impairment factors, and atmospheric effects. Proposed analysis and preliminary results shown can provide to interested readers the basic guidelines that will drive the practical implementation of IKNOW mission, as well as the most relevant issues to be faced by future developers of W-band missions using small LEO satellites.

Efficient Waveform Design for High-Bit-Rate W-band Satellite Transmissions

In the EHF (extremely high frequency) domain, W-band (75-110 GHz) offers promising perspectives for future satellite communications, mainly in terms of large bandwidth availability for high-bit-rate transmission. In this work an innovative physical (PHY) layer design for broadband satellite connections operating in W-band is proposed, which is based on the prolate spheroidal wave functions (PSWFs). PSWF waveforms (originally proposed in short-range indoor ultra-wideband communications) are aimed at optimizing the tradeoff between the concentration of pulse energy in a finite time interval and in a limited bandwidth. In our paper, PSWF-based 4-ary pulse shape modulation (PSM), characterized by a nearly optimal compromise between spectral and envelope compactness, has been tested for the radio interface of a W-band geostationary (GEO) downlink connection. The effect of nonlinear distortions, introduced by power-efficient saturating amplifiers, can be drastically reduced without any power back-off and will maintain a very good spectral efficiency. Experimental results obtained by means of realistic simulations fully demonstrate the potential advantages taken by PSWF in terms of increased spectral efficiency, link availability, and net payload rate with respect to state-of-the-art pulse-shaped modulations, raised-cosine filtered quadrature amplitude modulation (QAM), and Gaussian minimum shift keying (GMSK) commonly employed in satellite communications.

Perspectives of W-Band for Space Communications

In this paper, the main trends of the latest space missions will be outlined, dealing with the advantages of using W-band in space communication systems. In the first part, an overview of the current projects involved in the study of W-band is shown, highlighting the reasons of its future widespread.

Experimental Italian Q/V band satellite network

Broadband technologies are taking a predominant role in the emerging information society. In particular, broadband satellite communication systems, with their global access and broadcasting capabilities, are well suited to answer to the requirements of the information society. This paper focuses on the efforts that are currently spent toward the development of EHF (Extremely High Frequency) satellite communications systems. In particular, Q/V (35–75 GHz) and W (75–110 GHz) bands, represent an almost “free” spectrum resource that could be used to realize the so-called satellite gigabit-connectivity, in order to support innovative broadband applications. This paper presents the most important features of an experimental Q/V band satellite network based on the Alphasat TDP#5 (Technology Demonstration Payload), an ongoing project, funded by the Italian Space Agency, that aims at carrying out communication and propagation experiments over a Q/V band satellite link.

Waveform design solutions for EHF broadband satellite communications

The problematic RF environment experienced by broadband satellite communications at EHF frequency bands, in particular Q/W bands, call for the use of novel waveforms. This paper presents a detailed comparison of several waveforms in presence of nonlinear distortions and typical values of phase noise introduced at Q/W band. Two main types of waveforms have been compared: Constant Envelope multicarrier waveforms (CE-OFDM and CE-SCFDMA) and single carrier impulse-based waveforms (TH-UWB, DS-UWB and PSWF-based PSM). This comparison will allow to draw some practical guidelines for the waveforms design of EHF broadband satellite communications.

Flower Constellation of Orbiters for Martian Communication

Flower Constellations are a particular set of satellite constellations where every satellite covers the same repeating space track. When the Flower Constellations are visualized on an Earth centered Earth fixed reference frame, the relative orbits show flower-shaped figures centered on the Earth. This innovative type of constellation presents features useful to be used in several applications, such as telecommunications, navigation, Earth science and interferometric radar. Several missions are foreseen to explore Mars in the next years to collect data in order to enhance our knowledge of the red planet. This effort requires the development of a reliable orbital infrastructure to support telecommunications with orbiters, landers and rovers. In this paper, a novel telecommunication architecture is presented, based on the previously introduced Flower Constellations. We designed an optimized Flower Constellation for the coverage of sites/regions of interest of the Mars surface. We proved that our proposed constellation provides better performance with respect to a reference constellation called 4retro 111 in terms of access duration and average gap time.

Satellite communication and propagation experiments through the alphasat Q/V band Aldo Paraboni technology demonstration payload

Current high-throughput satellite (HTS) systems for broadband distributed user access are designed following two main concepts: The use of Ka band radio frequency (RF) links both for the forward and for the return link; this choice is due to the congestion of lower frequency bands and to the relatively large bandwidth available in the Ka band. Moreover, the RF technology in the Ka band is mature [1], [2]. The use of multispot coverage: this technique is largely applied to increase the system throughput through frequency reuse and system reconfigurability [2], [3].

Mode Switching Algorithms for DVB-S2 Links in W Band

In this paper an analysis on the use of Adaptive Coding and Modulation (ACM) techniques for EHF satellite communications is presented. In particular, our analysis is focused on W-band channels and includes the main channel impairments in this frequency band, i.e. rain fading and HPA non-linearity. The aim of the analysis is to identify modifications to the ACM mode switching algorithm to optimize their use at those high frequency bands.

The WAVE mission payload

In this paper, an overview of the WAVE mission payload architecture is presented. WAVE (W-band Analysis and VErification) is the new project funded by the Italian Space Agency (ASI). The aim is to design and develop a W-band geostationary (GEO) payload to be deployed for scientific experimental studies of the W-band channel and possible utilization in satellite data communications. The large bandwidth availability in the W-band range allows conceiving and proposing advanced services for future scenarios in order to meet high-quality requirements for a large number of users. The major parameters of the payload architecture are discussed in addition to the different requirements and specifications of the on-board transmission and reception components and their dependence on the host platform