Multi-beam satellite systems have been studied a lot in the last ten years. They
have many promising features like power gain, interference reduction, high flexibility
to adapt the asymmetric traffic distribution, and the improvement of the system
capacity compared with single-beam systems. In multi-beam satellite systems, the
beamforming antenna can generate a number of spot beams over the coverage area.
However, each beam will compete with others for resources to achieve satisfactory
communication. This is due to the fact that the traffic demand is potentially highly
asymmetrical throughout the satellite coverage. Therefore, in order to achieve a good
match between offered and requested traffic, the satellite requires a certain degree
of flexibility in allocating power, bandwidth and time-slot resources. Current multibeam
satellite systems with regular frequency reuse and uniform power allocation
can not satisfy these increasing requirements, which motivate us to investigate new
transmission schemes to replace the current ones.
In this dissertation, we first propose a novel system design, flexible system, which
is an extension of current multi-beam systems. It is characterized by the non-regular
frequency reuse and the flexibility in bandwidth and power allocation. Then, the
Beam Hopping (BH) system is proposed to evaluate the performance improvement
with the flexibility in time/space and power domain. As we know, the flexible system
and BH system operate in frequency and time/space domain, respectively. In
order to know which domain shows the best overall performance, we propose a novel
formulation of the Signal-to-Interference plus Noise Ratio (SINR) which allows us to
prove the time/frequency duality of these two schemes. Furthermore, to efficiently
utilize the satellite resources (e.g., power and bandwidth), we propose two capacity
optimization approaches subject to per-beam SINR constraints. Moreover, due to
the realistic implementation, a general methodology is formulated including the technological
constraints, which prevent the two systems dual of each other (named as
technological gap). The Shannon capacity (upper bound) and the state-of-art Modulation
and Coding (MODCOD) are analyzed in order to quantify the gap and evaluate the
performance of the two candidate schemes. Comparing with the current conventional
systems, simulation results show significant improvements in terms of power gain,
spectral efficiency and traffic matching ratio. They also show that the BH system is
less complex design and outperforms the flexible system specially for non-real time
services. This part of the Ph.D. work supported by an ESA-funded project on next
generation system of “Beam Hopping Techniques for Multi-beam Satellite Systems”.
This research is in close collaboration with the leading space industry (e.g. INDRA, MDA) and space research institutions (e.g., ESA, DLR (German Space Agency)).
In addition, we extend the work to mobile environments (e.g., railway scenario).
Since the current air interface standards (e.g., DVB-S2/RCS) lack of specification for
mobile scenarios, a new Fade Mitigation Technique (FMT), i.e., Link Layer Forward
Error Correction (LL-FEC) is introduced as a fading countermeasure for DVB-S2/RCS
in mobile environments. This part of the work points out that LL-FEC can overcome
the deep fading in mobile satellite scenarios (e.g. railway) by optimizing the FEC
codes (e.g. Reed-Solomon and Raptor codes). We have to note that such air interface
standards might need change to adapt to the new proposed systems: flexible and BH.
However, the methodology presented is also applicable.
We further investigate the secure communication of multibeam satellite systems by
using the system model developed in the BH project. The physical (PHY) layer security
technique is investigated to protect the broadcasted data and make it impossible to be
wiretapped. A novel multibeam satellite system is designed to minimize the transmit
power under the constraints of the individual secrecy rate requested per user.
The main contributions of this Ph.D. dissertation can be summarized as:
a. We study the resource allocation optimization in multi-domain (frequency, time,
space and power) for multi-beam satellite systems. First, we develop novel
matricial-based analytical multibeam system-level models that directly allows
testing different payloads technology and system assumptions. Second, we prove
that the system performance can be increased by dynamically adapting the resource
allocation to the characteristics of the system, e.g., traffic requested by
the terminal.
b. Theoretical studies and simulations prove that the proposed novel transmission
schemes perform better than the current system design in terms of power gain,
spectral efficiency, etc.. In addition, BH system turns out to show a less complex
design and superior performance than the flexible system.
c. Our analytical models allows us to also prove the theoretical duality between
the flexible and BH systems, which work in frequency domain and time domain,
respectively. Moreover, we develop a general methodology to include technological
constraints due to realistic implementation, obtain the main factors that
prevent the two technologies dual of each other in practice, and formulate the
technological gap between them.
d. We extend the work to mobile scenarios and prove that LL-FEC is applicable for
mobile satellite systems (e.g., railway) to compensate the fade due to the mobility
by optimizing the FEC codes (Reed-Solomon and Raptor codes). The results show
that Multiple Protocol Encapsulation Inter-burst FEC (MPE-IFEC) and extended
MPE-FEC with Raptor codes - as finally specified in DVB Return Channel via
Satellite for Mobile Scenario (DVB-RCS+M) - consistently perform better than
other LL-FEC schemes for mobile scenarios.
e. We point out that how to change the signalling of current version of standards
(e.g., DVB-S2/RCS+M) in order to allow achievable performance in the mobile
scenarios. The proposal has been finally adopted by the DVB-RCS+M standard.
f. We finally make use of our developed system models to investigate whether the
multibeam scenario allows the use of PHY layer security, a very valuable feature
that would broaden multibeam satellite applications. We prove that our models
are directly applicable for the study of PHY layer security in terms of joint optimization
of power control and beamforming for the BH payload. Moreover, the
proposed algorithm can ensure the minimum power consumption subject to the
individual secrecy rate requested per user.
Based on the work of the Ph.D., three journal papers and eleven international
conference papers have been published, and these publications systematically cover
all the contributions of this doctoral thesis work.
| Identifer | oai:union.ndltd.org:TDX_UAB/oai:www.tdx.cat:10803/32082 |
| Date | 28 September 2010 |
| Creators | Lei, Jiang |
| Contributors | Vázquez Castro, María Ángeles, Universitat Autònoma de Barcelona. Departament de Telecomunicació i Enginyeria de Sistemes |
| Publisher | Universitat Autònoma de Barcelona |
| Source Sets | Universitat Autònoma de Barcelona |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/doctoralThesis, info:eu-repo/semantics/publishedVersion |
| Format | 191 p., application/pdf |
| Source | TDX (Tesis Doctorals en Xarxa) |
| Rights | info:eu-repo/semantics/embargoAccess, ADVERTIMENT. L'accés als continguts d'aquesta tesi doctoral i la seva utilització ha de respectar els drets de la persona autora. Pot ser utilitzada per a consulta o estudi personal, així com en activitats o materials d'investigació i docència en els termes establerts a l'art. 32 del Text Refós de la Llei de Propietat Intel·lectual (RDL 1/1996). Per altres utilitzacions es requereix l'autorització prèvia i expressa de la persona autora. En qualsevol cas, en la utilització dels seus continguts caldrà indicar de forma clara el nom i cognoms de la persona autora i el títol de la tesi doctoral. No s'autoritza la seva reproducció o altres formes d'explotació efectuades amb finalitats de lucre ni la seva comunicació pública des d'un lloc aliè al servei TDX. Tampoc s'autoritza la presentació del seu contingut en una finestra o marc aliè a TDX (framing). Aquesta reserva de drets afecta tant als continguts de la tesi com als seus resums i índexs. |
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