Dynamic Bandwidth/Channel Access Technique Using FFT-Based Block Signal Transmission for Future Broadband Mobile Satellite Communication Systems

A concept for a future advanced mobile satellite communications system using a geostationary satellite is described. In the satellite of this system, a multiple spotbeam antenna, onboard beam interconnection, and millimeter-wave and Ka-band components are required. The configuration of the payloads of Japan's COMETS (Communications and Broadcasting Engineering Test Satellite) for advanced mobile satellite communication experiments is also described. The transponder has an IF filter bank and a SCPC/TDM (signal-carrier-per-channel/time-dimension multiplexing) regenerative modem for beam interconnection. >

Experiments on mobile satellite communications are being carried out to determine if they are technically feasible for future domestic satellite services in the Experimental Mobile Satellite System project, which uses Engineering Test Satellite-V. Experimental ISDN (integrated services digital network) basic-rate communications services have also been offered for marine vehicles. The authors describe the configuration of an experimental system for maritime ISDN satellite communications, and the characteristics of ISDN basic-rate interface connections for the digital telephones, G4 facsimiles, and color video-phone terminals of terrestrial ISDN services. This experiment provided much information for designing future mobile satellite communications systems. Moreover, it indicates that forward error correction in a mobile satellite link with poor transmission quality is very effective at improving the communication quality of mobile satellite systems. >

A multibeam digital beamforming (DBF) antenna, developed for a future mobile satellite communications system, is mounted on a vehicle for a receiving experiment in a mobile environment using a satellite signal in the L band. The multibeam is formed by 2-dimensional FFT signal processing. Automatic acquisition and tracking of an arriving signal are achieved by selecting a maximum beam out of the multiple beams in real-time.

An increase in the size of on‐board antenna reflectors is a key technology in providing economical services by miniaturized portable equipment in future mobile satellite communication systems. In practice, a mesh antenna can be used as the on‐board antenna. However, since the reflector surface of this antenna is supported by the cable and the mesh, and its size is larger, the surface is subject to larger thermal deformation in orbit than is the solid antenna reflector. Conventional compensation methods such as passive thermal control or rotation of the antenna reflector cannot maintain the required antenna performances. Various methods have been reported to compensate for the deterioration of antenna performance by thermal deformation.This paper describes a static shape control system for a 10‐m diameter antenna which actively compensates for the deformation by using a shape‐measuring sensor and shape‐compensation actuator. The configuration of the sensor and the experimental results by a functional model are described to confirm the design validity. The shape‐compensation method by the actuator was confirmed to be useful in achieving a required surface accuracy.

We calculate the availability of circuit service to a user in a mobile satellite communication system. The availability, i.e., the percentage of time the user can expect to communicate reliably using the communication system is a function of the power available to the user and the channel (Rician or Rayleigh fading) encountered by the user. In a mobile satellite communication system, the channel is a function of user position, the number of satellites visible to the user, and their positions. Using a simulation of the constellation orbits and an associated channel model, we calculate the availability provided by various proposed mobile satellite communication systems that use LEO and MEO satellites. A conclusion of this paper is that the visibility of multiple satellites is imperative for high availability.

A highly innovative global broadband mobile communication system concept

In this paper, we describe the development of a GSM-derived regional mobile satellite communication system. We first discuss the market needs of a regional mobile communication system, and stress the technical requirements for such a system to be successful in the commercial world. We then point out the advantages of deriving such a system from the popular GSM standard and discuss the similarities and differences between the two systems. We then describe a system designed by Lockheed Martin Corp., known as ACeS, which serves the telecommunication needs of Asia. The ACeS system works in both the cellular and satellite environments and is designed to make optimal use of the similarities and differences to the GSM system. We end the paper by discussing some challenges in the evolving area of mobile satellite communication systems.

Wide-band digital indoor and future mobile communication systems are being developed in the quasi-millimeter and millimeter wave frequency bands. In such high-speed systems, the degradation of transmission quality by multipath fading constitutes a limiting barrier. Multipath fading, which results from reflection, refraction and scattering of radio waves by buildings and other structures, gives rise to more than one path reaching the receiver and produces a distorted version of the transmitted signal. In mobile and indoor communication systems it cannot be eliminated, therefore the multipath channel must be well characterized in order to reduce its effect in the design of such systems. The objective of this research is to study the multipath fading and delay spread effects due to buildings in an urban propagation channel. In particular, the effects of the building materials, shapes and number of buildings on multipath fading are being studied.

In order to realize a higher-code-gain forward error correction scheme in mobile satellite communication systems, a novel concatenated coding scheme employing soft decision decoding for not only inner codes but also outer codes (double soft decision, or DSD, concatenated forward error correction scheme) is proposed. Soft-decision outer decoding can improve the bit error probability of inner decoded data. In this scheme, likelihood information from an inner Viterbi decoder is used in the decoding of outer codes. A technique using the path memory circuit status 1.0 ratio for likelihood information is proposed, and is shown to be the most reliable even though it requires the simplest hardware among the alternative methods. A computer simulation clarifies that the DSD scheme improves Pe performance to one-third of that of the conventional hard-decision outer decoding. Moreover, to reduce the interleaving delay time in fading channels or inner decoded data of concatenated codes, a parallel forward error correction scheme is proposed. >

Diversity combining methods for mobile satellite communication systems employing convolutional encoding and soft-decision Viterbi decoding are evaluated. Computer simulation clarifies that the pre-Viterbi-decoding maximal ratio combining method has better performance than other methods in Rician fading channels. The simulation results agree with the Pe (bit error probability) performance derived from the numerical analysis for slow fading using the approximate Pe performance of Viterbi decoding in AWGN (additive white Gaussian noise) channels and the probability density function of Rician fading. Applying this diversity method to the multi-beam mobile satellite communication systems, a satellite beam diversity reception scheme is proposed. A computer simulation result shows that the proposed scheme decreases the packet error rate of the control signals to less than 1/100 around the satellite beam boundary. >

In this paper, we present a novel approach for using the smart antennas (SA) to exploit the space diversity for the next generations of mobile communication systems. We propose a combination of the MUltiple SIgnal Classification (MUSIC) and the Least Mean Squares (LMS) algorithms in one algorithm named MLMS. We propose the MUSIC algorithm for finding the direction of the users in the cell while we consider the LMS algorithm for enhancing the accuracy of the obtained Direction of Arrival (DOA) angles, performing the beam generation process, and keep tracking of the users in the cell. Furthermore, we propose a scheduling algorithm that performs the scheduling in terms of the generated beams. The space diversity, together with the time and frequency diversities of LTE (Long Term Evaluation) provide a large capacity enhancement to the next generations of wireless mobile communication systems. Our simulation results show that our novel approach has the capability to converge and completely follow the desired user signal with a very high resolution. The convergence and the accurate tracking of the desired user signal take place after 13 iterations while in the traditional LMS, the convergence needs 85 iterations to take place. This means 84.7% improvement over the traditional LMS algorithm for the same number of calculations in each iteration. In addition, our proposed scheduling scheme based on beamforming shows a gain of around 15% in the total aggregated data rate for each 10° decrease in the beam size.

One of the challenges of the mobile industry is to cope with the growth of mobile traffic demand expected for the next years, primarily driven by the increasing usage of mobile video services. Indeed, the existence of increasingly powerful terminals is encouraging the consumption of high-quality video content. Usually, video services are identified with linear Television (TV) and scheduled broadcast (point-to-multipoint (p-t-m)) distribution. However, the consumption of video content over mobile networks is different from traditional fixed TV because contents are mainly consumed on-demand with unicast point-to-point (p-t-p) connections. Then, the convergence of linear TV and on-demand content delivery represents a challenge that requires a combined broadcast/unicast transmission model. This dissertation addresses the use of broadcasting technologies for the provision of mobile multimedia services in Fourth Generation (4G) mobile broadband networks and beyond. Specifically, the dissertation focuses on the broadcast technology included in 4G Long Term Evolution (LTE) and LTE Advanced (LTE-A) networks, known as Enhanced Multicast Broadcast Multimedia Services (eMBMS). It analyses the benefits of the eMBMS physical layer aspects regarding Multimedia Broadcast Multicast Services over a Single Frequency Network (MBSFN) deployments and identifies the current limitations of eMBMS at physical layer by comparing with the broadcast technology of the other 4G mobile system, the Institute of Electrical and Electronics Engineers (IEEE) 802.16m standard. Those limitations are the use of a dedicated carrier and Multiple-Input Multiple-Output (MIMO) techniques for broadcast transmissions. Our investigations employ a complete simulation platform including link-level and system-level simulations to evaluate the performance of broadcast transmissions in these real technologies. The research on eMBMS services is aimed at finding the optimum delivery of streaming and file download services focusing on the Radio Resource Management (RRM) problem and trade-off between Physical layer ? Forward Error Correction (PHY-FEC) and Application Layer - Forward Error Correction (AL-FEC). Concerning streaming services, results show that the use of AL-FEC increases the coverage level and, then, the maximum service data rate. The gain due to AL-FEC is greater in scenarios with high mobility users, although, this gain is limited if low zapping times are desired. Regarding file delivery services, this dissertation analyses the duration of the transmission required to guarantee the correct file reception and the reduction in the mean throughput of unicast users with different delivery modes. They are the unicast delivery, the eMBMS delivery and a hybrid approach, which combines a first eMBMS delivery with a post-delivery error repair phase with unicast transmissions. Our results show that the hybrid delivery is the most efficient configuration in terms of file download time, although it further reduces unicast performance. On the other hand, as an exemplary use case, this dissertation also investigates the use of LTE networks for the provision of vehicular safety services comparing both unicast and eMBMS delivery modes. Results highlight the significant benefits in terms of resource usage, end-to-end latency and cost delivery saving that can be achieved by using eMBMS for the delivery of road safety applications. In addition, research also addresses the problem associated with the support of road safety applications over the current eMBMS architecture, the configuration of the Intelligent Transportation Systems (ITS) server in charge of distributing safety messages as well as on its interaction with the mobile network operator. Finally, this dissertation analyzes feasible options of convergence between mobile and broadcast industry to ensure the success of the mobile broadcasting deployments in the future. A separated evolution of the broadcast technologies of both industries would lead to a scenario with two complete different industries, with different network infrastructures and business models competing for market and spectrum. This dissertation proposes an approach by which the definition of the future Fifth Generation (5G) mobile broadband communication system could bring together the cellular and broadcast industries to form a single fixed and mobile converged network and offer a full alternative to terrestrial TV broadcasting as a universal service

This paper presents the design of a compact planar inverted-F antenna (PIFA) suitable for mobile handset applications. The prototype of the proposed antenna designs to satisfy specific bandwidth specifications of present-day mobile cellular communication systems, including the global system for mobile communication (GSM; 890-960 MHz), the digital communication system (DCS; 1710-1880 MHz), the personal communication system (PCS; 1850- 1990 MHz), and the universal mobile telecommunication system (UMTS; 1920- 2170 MHz). Therefore, it could be applicable for the existing and future mobile communication systems. Design details and experimental results are also presented and discussed.

Mobile communication systems rely on radiofrequency waves to operate. Given the popularity and ubiquity of mobile communication devices as well as network densification, the level of Electromagnetic Field (EMF) exposure to the public is expected to rise significantly over the next few years. Although there is no clear evidence linking short-term exposure to EMF emission from wireless communication systems with adverse health effects, the International Agency for Research on Cancer (IARC) has concluded that EMF radiation is possibly carcinogenic. To cope with the concerns of the general public, the European Environmental Agency has recommended non-technical precautionary approaches to minimize exposure to EMF emissions. Rather than relying on these non-technical approaches, EMF, latency, network resilience and connection density, alongside traditional criteria such as spectral efficiency and energy efficiency are expected to take centre stage in the development of 5G systems. This book focuses on innovative EMF exposure research for future generations of mobile and wireless communications. This timely publication highlights the novel work done on reducing EMF emissions in future mobile communication systems and how to develop smart integrated technical solutions.

In this paper we investigate the effect of an adaptive fuzzy closed-loop power control (CLPC) scheme on the performance of the DS/CDMA-based mobile satellite communication systems with a low earth orbit (LEO) satellite constellation in which the long round trip delay (RTD) and fading effect according to elevation angle should be considered. Since the RTD between mobile terminals (MT) and earth station (ES) via satellite in LEO is on the order of 10-20 ns and fading is more severe, a conventional closed-loop power control with fixed step size is much less effective than it is on a terrestrial channel. In order to cope with this performance degradation, we propose a closed-loop power control scheme by adaptive fuzzy rule-based step size decision method which is based on fuzzy logic control (FLC). So, in this paper, we compare the performance of the adaptive fuzzy closed-loop power control with that of the conventional fixed step closed-loop power control, we show that the proposed method makes better performance.