Shuai Han

Optimal Power Allocation for Dual-Hop Full-Duplex Decode-and-Forward Relay

The full-duplex relayed transmission is an expansion of relay technique. In this paper, we investigate an optimal power allocation strategy for the dual-hop full-duplex decode-and-forward (DF) relay system with joint constraint of individual and global power. We prove that the optimal allocation solution is located on the three boundary conditions of the constraint domain. The golden section search algorithm is used to obtain the highly accurate numerical solution of the optimal allocation strategy. Simulation results indicate that the optimal power allocation strategy enhances the outage performance.

A Complete Complementary Coded MIMO System and Its Performance in Multipath Channels

In this paper, we propose a new system architecture using complete complementary (CC) codes for a multicarrier MIMO CDMA system to combat multipath fading in wireless channels. Unlike traditional MIMO systems, complementary codes were designed at chip-level to achieve time and frequency-spreading for each antenna. We analyze the system performance in multipath fading channels. A closed form expression of bit error rate (BER) performance is obtained. Extensive simulations were conducted to verify the analytical results. Our results indicate that a CC coded MIMO system can effectively decrease BER and take advantage of diversity gain.

Automatic Precision Control Positioning for Wireless Sensor Network

By deploying a radio propagation model, we will be able to deduce the distance between the transmitter and the receiver based on received signal strength (RSS). This method is widely adopted in wireless sensor network (WSN) positioning systems. The ranging accuracy of such a system is extremely poor because of slow and fast fading. Although the former has been thoroughly analyzed, the latter is rarely discussed. This is based on the assumption that fast fading can be compensated for by averaging, but how many times RSS should be measured to obtain a certain level of precision remains unclear. In addition, positioning error is related to the distribution of sensors, which makes it both unstable and unreliable. In this paper, ranging error and positioning error are thoroughly discussed to achieve a better understanding of the poor performance of the system. Based on these theoretical analyses, an automatic precision control algorithm is proposed as a solution for the instability of RSS-based WSN positioning systems. Supported by both deduction and simulations, this method will improve the stability of WSN location systems. In addition, the energy consumption of ranging processes is minimized, while positioning accuracy is guaranteed.

Outage probability of multi-hop full-duplex DF relay system over Nakagami-m fading channels

The full-duplex relay is an expansion of relay technique. In this paper, we investigate the outage performance of multi-hop full-duplex decode-and-forward (DF) relay system over Nakagami-m fading channels. The theoretical expression based on the infinite Gamma series representation for the end-to-end outage probability of multi-hop full-duplex DF relay is derived for the first time. Besides, a loose lower bound and a highly accurate approximation for the outage probability are presented. With the increasing of self-interference energy, the outage performance of full-duplex system is even worse than that of half-duplex system. Moreover, the simulation results confirm the validity of the motivation and the analysis.

An indoor radio propagation model considering angles for WLAN infrastructures

Wireless local area network fingerprint-based indoor location system is a hot topic these years because it needs no extra hardware and is very easy to deploy. However, it demands a database containing the distribution of received signal strength RSS of the area of interest,called radio map. Conventionally, we need to grid the area densely and manually measure RSS values on intersections, which will consume a lot of time and human resources. What is worse, change of the environment may render this database totally useless. Our consideration is to measure RSS on a small amount of these intersections and use them to build a radio propagation model. Then, this model can be deployed to predict RSS values of other intersections and reconstruct the radio map. In other words, we only need to collect a very small part the radio map and utilize the radio propagation model to recover the whole one. So far, many models have been proposed, among which the one suggested by Seidel, named floor attenuation factor propagation model, achieves great balance between computational request and accuracy. But it is not compatible with environments in some scenarios. So as to compensate for this deficiency, we take into account the angles formed by signal and surfaces of obstacles, and the results show better compatibility. The proposed model has four parameters that are related to the environments, and our second contribution in this paper is to propose a method to determine them. In fact, after collecting a small part of the radio map, we can estimate these parameters with least square method. Then, these parameters can be used to predict the signal strength at any other points in the same environment, and the whole radio map is rebuilt. According to practical experiments, performance of the radio map built by the proposed model is not as good as the manually collected one, but 80% of collecting labor is saved. Copyright

Future Alternative Positioning, Navigation, and Timing Techniques: A Survey

The GNSS has been considered the first choice for providing PNT services to telecommunications, power industry, and transportation applications because of its advantages of wide coverage, high accuracy, and low cost. However, the GNSS is inherently vulnerable to intended or unintended radio interference, and this threat has become more serious because of the easy availability of GNSS jammers on the market. From the robustness and safety perspectives, PNT services should not solely rely on GNSS. APNT solutions must be made available in the case of a GNSS outage. In this article, we investigate APNT solutions for aerial vehicles for which highly standardized PNT services are required to ensure secure and safe transportation, including solutions that have been proposed by the FAA in North America. We discuss the basic principle of each solution and analyze and compare their characteristics under different application scenarios. Finally, we conclude the article by predicting future trends in APNT solutions.

A novel anti-spoofing method based on particle filter for GNSS

The Global Navigation Satellite System (GNSS) has been widely used by militaries as well as civilians. Generally, the locating accuracy is high, but the system is lack of immunity against spoofing attack, which may deceive the receiver into error positioning. In order to deal with the problem, a maximum particle weight monitoring scheme based on particle filter (PF) is proposed for spoofing detection in this paper. The scheme exploits the relation between spoofing and particle weight, and it can detect spoofing by catching the abnormal maximum particle weight. After detection process, an improved robust estimation method is applied in the spoofing suppression, thereby eliminating the impairing. Both the theoretical analyses and the simulation results verify the effectiveness of the spoofing detection and suppression schemes.

A survey of two kinds of complementary coded CDMA wireless communications

In this article, we present a comprehensive survey of existing literature in the area of complementary coded CDMA (CC-CDMA) technique for wireless communications to provide an introduction and overview to the field. According to the kinds of independent sub-channels, we divide the existing CC-CDMA solutions into two categories: time division multiplex (TDM) and frequency division multiplex (FDM) CC-CDMA systems. Then we compared them in terms of resistance of multiuser interference and multi-path interference, implementation complexity and spread and spectrum efficiency.

A novel collaborative navigation architecture based on decentralized and distributed Ad-hoc networks

To provide services for other applications, promoting the availability of Global Positioning System (GPS)-is very important. While in the urban environments or with the high-power malicious interference, GPS signal is shaded by buildings or overwhelmed by interference. Hence the receivers may not acquire correct pseudo random noise (PRN) codes. Assisted GPS (A-GPS) technologies can solve the shaded problem, and antenna array with adaptive digital beam forming (ADBF) or spacetime adaptive processing (STAP) has been proved the effective methodology for interference suppressing. However, A-GPS may be not available, and the radio-frequency (RF) front end is too costly and cumbersome for a single customer. This paper investigates the collaborative navigation technology, utilizing GPS group users with dynamic Ad-hoc network and internal range measurements. Decentralized and distributed network architectures are presented for shading and interference presences, based on which user assistance and ambiguity removing for ADBF are proposed. Simulation results verify the performance improvement of the collaborative navigation based on dynamic Ad-hoc networking for different presences.

A Localization Based Routing Protocol for Dynamic Underwater Sensor Networks

Owing to the rapid development of underwater applications, the research on underwater wireless sensor networks (UWSNs) is becoming more and more significant. Low bandwidth, high latency, limited energy and node float mobility are basic challenges for underwater sensor networks. Most of the theories for terrestrial sensor networks can not be applied to underwater sensor networks. In this paper, we focus on the localization and routing issues for dynamic UWSNs. Location based routing protocols can suit the dynamic situation of UWSNs well. However, most research assumes that the nodes know their locations, which may be not appropriate for some applications. This paper combines these two aspects together to design a localization based routing protocol for dynamic UWSNs. The simulation results show our method can effectively route data from the source nodes to the sink nodes in a dynamic environment.