The concept of single-frequency, dual-system (SF-DS) real-time kinematic (RTK) positioning has become feasible since, for instance, the Chinese BeiDou Navigation Satellite System (BDS) has become operational in the Asia-Pacific region. The goal of the present contribution is to investigate the single-epoch RTK performance of such a dual-system and compare it to a dual-frequency, single-system (DF-SS). As the SF-DS we investigate the L1 GPS + B1 BDS model, and for DF-SS we take L1, L2 GPS and B1, B2 BDS, respectively. Two different locations in the Asia-Pacific region are analysed with varying visibility of the BDS constellation, namely Perth in Australia and Dunedin in New Zealand. To emphasize the benefits of such a model we also look into using low-cost ublox single-frequency receivers and compare such SF-DS RTK performance to that of a DF-SS, based on much more expensive survey-grade receivers. In this contribution a formal and empirical analysis is given. It will be shown that with the SF-DS higher elevation cut-off angles than the conventional $$10^{\circ }$$
 or $$15^{\circ }$$
 can be used. The experiment with low-cost receivers for the SF-DS reveals (for the first time) that it has the potential to achieve comparable ambiguity resolution performance to that of a DF-SS (L1, L2 GPS), based on the survey-grade receivers.

Single-frequency, dual-GNSS versus dual-frequency, single-GNSS: a low-cost and high-grade receivers GPS-BDS RTK analysis

The integration of the Chinese BDS with other systems, such as the American GPS, makes precise RTK positioning possible with low-cost receivers. We investigate the performance of low-cost ublox receivers, which cost a few hundred USDs, while making use of L1 GPS + B1 BDS data in Dunedin, New Zealand. Comparisons will be made to L1 + L2 GPS and survey-grade receivers which cost several thousand USDs. The least-squares variance component estimation procedure is used to determine the code and phase variances and covariances of the receivers and thus formulate a realistic stochastic model. Otherwise, the ambiguity resolution and hence positioning performance would deteriorate. For the same reasons, the existence of receiver-induced time correlation is also investigated. The low-cost RTK performance is then evaluated by formal and empirical ambiguity success rates and positioning precisions. It will be shown that the code and phase precision of the low-cost receivers can be significantly improved by using survey-grade antennas, since they have better signal reception and multipath suppression abilities in comparison with low-cost patch antennas. It will also be demonstrated that the low-cost receivers can achieve competitive ambiguity resolution and positioning performance to survey-grade dual-frequency GPS receivers.

/pdf/low-cost-high-precision-single-frequency-gps-bds-rtk-2gaq65og58.pdf

Low-cost, high-precision, single-frequency GPS---BDS RTK positioning

A generic internet of things architecture for controlling electrical energy consumption in smart homes

This article proposes an innovative resource management framework for the next generation heterogeneous satellite networks (HSNs), which can achieve cooperation between independent satellite systems and maximizing resource utilization. The key points of the proposed design lie in the architecture that supports the intercommunication between different satellite systems, and the SDN/NFV-based management offering the matching between resources and services. Based on the framework, we then apply deep reinforcement learning (DRL) into the system due to its strong ability in optimal matching. The two problems of multiobjective reinforcement learning and multiagent reinforcement learning are studied to adapt the development of the HSN. The combination of the DRL and resource allocation achieves integrated resource management across different satellite systems and achieves resource allocation in the HSN which can be implemented more flexibly and efficiently.

The Next Generation Heterogeneous Satellite Communication Networks: Integration of Resource Management and Deep Reinforcement Learning

The emerging GNSSs make single-frequency (SF) RTK positioning possible In this contribution two different types of low-cost (few hundred USDs) RTK receivers are analyzed, which can track L1 GPS, B1 BDS, E1 Galileo and L1 QZSS, or any combinations thereof, for a location in Dunedin, New Zealand These SF RTK receivers can potentially give competitive ambiguity resolution and positioning performance to that of more expensive (thousands USDs) dual-frequency (DF) GPS receivers A smartphone implementation of one of these SF receiver types is also evaluated The least-squares variance component estimation (LS-VCE) procedure is first used to formulate a realistic stochastic model, which assures that our receivers at hand can achieve the best possible ambiguity resolution and RTK positioning performance The best performing low-cost SF RTK receiver types are then assessed against DF GPS receivers and survey-grade antennas Real data with ionospheric disturbances at low, medium and high levels are analyzed, while making use of the ionosphere-weighted model It will be demonstrated that when the presence of the residual ionospheric delays increases, instantaneous RTK positioning is not possible for any of the receivers, and a multi-epoch model is necessary to use It is finally shown that the low-cost SF RTK performance can remain competitive to that of more expensive DF GPS receivers even when the ionospheric disturbance level reaches a Kp-index of 7−, ie for a strong geomagnetic storm, for the baseline at hand

/pdf/an-assessment-of-smartphone-and-low-cost-multi-gnss-single-1wadj9v5sx.pdf

An assessment of smartphone and low-cost multi-GNSS single-frequency RTK positioning for low, medium and high ionospheric disturbance periods

Wireless sensor networks (WSNs) are widely applied in monitoring and control of environment parameters. It is sometimes necessary to disseminate data through wireless links after they are deployed in order to adjust configuration parameters of sensors or distribute management commands and queries to sensors. Several approaches have been proposed recently for data dissemination in WSNs. However, none of these approaches achieves both high efficiency and low complexity simultaneously. To address this problem, cluster-tree based network architecture, which divides a WSN into hierarchies and clusters is proposed. Upon this architecture, data is delivered from base station to all sensors in clusters hierarchy by hierarchy. In each cluster, father broadcasts data to all his children with instantly decodable network coding (IDNC), and a novel scheme targeting to maximize total transmission gain (MTTG) is proposed. This scheme employs a new packet scheduling algorithm to select IDNC packets, which uses weight status feedback matrix (WSFM) directly. Analysis and simulation results indicate that the transmission efficiency approximate to the best existing approach maximum weight clique, but with much lower computational overhead. Hence, the energy efficiency achieves both in data transmission and processing.

Data dissemination in wireless sensor networks with instantly decodable network coding

Space Information Network (SIN) has recently become prevalent as a promising approach to solve the collaboration difficulty among current space programs. However, due to large scale, high component complexity and dynamic characteristics of the SIN, the task of proper SIN architecture design is challenging. We propose a novel architecture of SIN, which composed of Geostationary Earth Orbit (GEO) satellites as backbone network nodes, Low Earth Orbit (LEO) or Incline Geosynchronous Orbit (IGSO) satellites as enhanced coverage nodes, and high altitude platforms to meet the service requirements of emergency or hot-spot applications. Compared with most existing studies, the proposed architecture is autonomous system (AS) based. The complex and dynamic SIN is decoupled into semi-static subnetworks constituted by similar nodes which are easier to control.

A novel space information network architecture based on autonomous system

The Combined-GEO-IGSO constellation is the combination of Geostationary Earth Orbit (GEO) satellite and Inclining GeoSynchronous Orbit (IGSO) satellite. The Combined-GEO-IGSO constellation can integrate the advantages of GEO and IGSO to achieve regional coverage. In order to discuss the performances of the Combined-GEO-IGSO constellation, the performances of coverage, elevation, diversity, and transmission are simulated in China and surrounding regions by Satellite Tool Kit (STK). The simulation results show that: the combined constellation can reach higher multi-satellite coverage and higher communication elevation in China and surrounding areas; the Doppler shift, delay, and propagation loss of this constellation have little impact on the system. As regional coverage constellation, the Combined-GEO-IGSO is feasible.

Coverage performances analysis on Combined-GEO-IGSO satellite constellation

This article investigates the topology control problem in the space information network (SIN) using a hierarchical autonomous system (AS) approach. We propose an AS network topology control (AS-TC) algorithm to minimize the time delay in the SIN. Compared with most existing approaches for SIN where either the purely centralized or the purely distributed control method is adopted, the proposed algorithm is a hybrid control method. In order to reduce the cost of control, the control message exchange is constrained among neighboring sub-AS networks. We prove that the proposed algorithm achieve logical k-connectivity on the condition that the original physical topology is k-connectivity. Simulation results validate the theoretic analysis and effectiveness of the AS-TC algorithm.

A Hierarchical Autonomous System Based Topology Control Algorithm in Space Information Network

In this paper, the fundamental characteristics of cyclostationary signal are investigated. Firstly, through analyzing the cyclostationarity of some typical satellite communication signals (e.g. MPSK, MSK and QAM signals), the guidelines to blindly detect satellite communication signals are obtained. Then the simulation of the above signals' cyclic spectrum is performed based on engineering calculation formula of spectral correlation function. Furthermore, under the condition of low SNR, the signals detection is realized by searching the spectral peak on the section of cycle frequency. Last but not least, the performance of the algorithm is analyzed, and the simulation results prove the validity of the method.

Gengxin Zhang

Papers

Data dissemination in wireless sensor networks with instantly decodable network coding

A novel space information network architecture based on autonomous system

Coverage performances analysis on Combined-GEO-IGSO satellite constellation

A Hierarchical Autonomous System Based Topology Control Algorithm in Space Information Network

Blind detection of satellite communication signals based on cyclic spectrum