An Efficient Uplink Multi-Connectivity Scheme for 5G mmWave Control Plane Applications

The millimeter wave (mmWave) frequencies offer the potential of orders of magnitude increases in capacity for next-generation cellular systems. However, links in mmWave networks are susceptible to blockage and may suffer from rapid variations in quality. Connectivity to multiple cells - at mmWave and/or traditional frequencies - is considered essential for robust communication. One of the challenges in supporting multi-connectivity in mmWaves is the requirement for the network to track the direction of each link in addition to its power and timing. To address this challenge, we implement a novel uplink measurement system that, with the joint help of a local coordinator operating in the legacy band, guarantees continuous monitoring of the channel propagation conditions and allows for the design of efficient control plane applications, including handover, beam tracking and initial access. We show that an uplink-based multi-connectivity approach enables less consuming, better performing, faster and more stable cell selection and scheduling decisions with respect to a traditional downlink-based standalone scheme. Moreover, we argue that the presented framework guarantees (i) efficient tracking of the user in the presence of the channel dynamics expected at mmWaves, and (ii) fast reaction to situations in which the primary propagation path is blocked or not available.Comment: Submitted for publication in IEEE Transactions on Wireless Communications (TWC

Proceedings of the Second International Mobile Satellite Conference (IMSC 1990)

Presented here are the proceedings of the Second International Mobile Satellite Conference (IMSC), held June 17-20, 1990 in Ottawa, Canada. Topics covered include future mobile satellite communications concepts, aeronautical applications, modulation and coding, propagation and experimental systems, mobile terminal equipment, network architecture and control, regulatory and policy considerations, vehicle antennas, and speech compression

Timing and Carrier Synchronization in Wireless Communication Systems: A Survey and Classification of Research in the Last 5 Years

Timing and carrier synchronization is a fundamental requirement for any wireless communication system to work properly. Timing synchronization is the process by which a receiver node determines the correct instants of time at which to sample the incoming signal. Carrier synchronization is the process by which a receiver adapts the frequency and phase of its local carrier oscillator with those of the received signal. In this paper, we survey the literature over the last 5 years (2010–2014) and present a comprehensive literature review and classification of the recent research progress in achieving timing and carrier synchronization in single-input single-output (SISO), multiple-input multiple-output (MIMO), cooperative relaying, and multiuser/multicell interference networks. Considering both single-carrier and multi-carrier communication systems, we survey and categorize the timing and carrier synchronization techniques proposed for the different communication systems focusing on the system model assumptions for synchronization, the synchronization challenges, and the state-of-the-art synchronization solutions and their limitations. Finally, we envision some future research directions

MSAT-X: A technical introduction and status report

A technical introduction and status report for the Mobile Satellite Experiment (MSAT-X) program is presented. The concepts of a Mobile Satellite System (MSS) and its unique challenges are introduced. MSAT-X's role and objectives are delineated with focus on its achievements. An outline of MSS design philosophy is followed by a presentation and analysis of the MSAT-X results, which are cast in a broader context of an MSS. The current phase of MSAT-X has focused notably on the ground segment of MSS. The accomplishments in the four critical technology areas of vehicle antennas, modem and mobile terminal design, speech coding, and networking are presented. A concise evolutionary trace is incorporated in each area to elucidate the rationale leading to the current design choices. The findings in the area of propagation channel modeling are also summarized and their impact on system design discussed. To facilitate the assessment of the MSAT-X results, technology and subsystem recommendations are also included and integrated with a quantitative first-generation MSS design

Laboratory and field trials evaluation of transmit delay Diversity applied to DVB-T/H networks

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.The requirements for future DVB-T/H networks demand that broadcasters design and deploy networks that provide ubiquitous reception in challenging indoors and other obstructed situations. It is essential that such networks are designed cost-effectively and with minimized environmental impact. The use of transmit diversity techniques with multiple antennas have long been proposed to improve the performance and capacity of wireless systems. Transmit diversity exploits the scattering effect inherent in the channel by means of transmitting multiple signals in a controlled manner from spatially separated antennas, allowing independently faded signals to arrive at the receiver and improves the chances of decoding a signal of acceptable quality. Transmit diversity can complement receive diversity by adding an additional diversity gain and in situations where receiver diversity is not practical, transmit diversity alone delivers a comparable amount of diversity gain. Transmit Delay Diversity (DD) can be applied to systems employing the DVB standard without receiver equipment modifications. Although transmit DD can provide a gain in NLOS situations, it can introduce degradation in LOS situation. The aim of this thesis is to investigate the effectiveness in real-word applications of novel diversity techniques for broadcast transmitter networks. Tests involved laboratory experiments using a wireless MIMO channel emulator and the deployment of a field measurement campaign dedicated to driving, indoor and rooftop reception. The relationship between the diversity gain, the propagation environment and several parameters such as the transmit antenna separation, the receiver speed and the Forward Error Correction Codes (FEC) configuration are investigated. Results includes the effect of real-word parameter usually not modeled in the software simulation analysis, such as antenna radiation patterns and mutual coupling, scattering vegetation impact, non-Gaussian noise sources and receiver implementation. Moreover, a practical analysis of the effectiveness of experimental techniques to mitigate the loss due to transmit DD loss in rooftop reception is presented. The results of this thesis confirmed, completed and extended the existing predictions with real word measurement results

The GPS-Linked Transponder - A Command, Telemetry, and Positioning System for Small Spacecraft

A proposed GPS-Linked Transponder (GLT) Command, Telemetry, and Positioning System is described that offers significant advantages over present systems. The new system would replace the standard coherent transponder and modify existing ground-based systems to provide the U.S. space industry with significantly smaller and lighter-weight flight systems in addition to simplified ground stations with reduced operating costs. The GLT comprises a NASA STDN/ DSN-compatible or AFSCN/SGLS-compatible command receiver/detector, a 20-Mbps-capable PCM/PSK telemetry transmitter with a selectable-rate FEC encoder and optional encryptor, and a dual-mode spacecraft positioning subsystem including a full GPS receiver/navigator and/or GPS trans digitizer. The GLT design is based on similar hardware developed by APL for SDlO. The system will recover high accuracy spacecraft position and time data-either in real time autonomously or in near-real time on the ground-using advanced GPS positioning techniques. A simplified command receiver option is also available when compatibility with existing standards is not required and improved capability is desired. In the transdigitizer-only mode, mass and size are reduced to nearly one-tenth of existing transponder systems. Other advantages include reduced complexity and significantly higher uplink and downlink data rate communications than presently supported. Five ground-station configurations are defined, each providing varying levels of spacecraft positioning accuracies to the user

Active Terminal Identification, Channel Estimation, and Signal Detection for Grant-Free NOMA-OTFS in LEO Satellite Internet-of-Things

This paper investigates the massive connectivity of low Earth orbit (LEO) satellite-based Internet-of-Things (IoT) for seamless global coverage. We propose to integrate the grant-free non-orthogonal multiple access (GF-NOMA) paradigm with the emerging orthogonal time frequency space (OTFS) modulation to accommodate the massive IoT access, and mitigate the long round-trip latency and severe Doppler effect of terrestrial-satellite links (TSLs). On this basis, we put forward a two-stage successive active terminal identification (ATI) and channel estimation (CE) scheme as well as a low-complexity multi-user signal detection (SD) method. Specifically, at the first stage, the proposed training sequence aided OTFS (TS-OTFS) data frame structure facilitates the joint ATI and coarse CE, whereby both the traffic sparsity of terrestrial IoT terminals and the sparse channel impulse response are leveraged for enhanced performance. Moreover, based on the single Doppler shift property for each TSL and sparsity of delay-Doppler domain channel, we develop a parametric approach to further refine the CE performance. Finally, a least square based parallel time domain SD method is developed to detect the OTFS signals with relatively low complexity. Simulation results demonstrate the superiority of the proposed methods over the state-of-the-art solutions in terms of ATI, CE, and SD performance confronted with the long round-trip latency and severe Doppler effect.Comment: 20 pages, 9 figures, accepted by IEEE Transactions on Wireless Communication