협력 재밍을 이용한 중계 네트워크의 보안 통신을 위한 최적화 및 할당 기법

학위논문 (박사)-- 서울대학교 대학원 : 공과대학 전기·정보공학부, 2019. 2. 이재홍.Physical layer security is a promising technology in the upcoming fifth generation (5G) wireless communication because the wireless communication is vulnerable to eavesdrop and it is complex to encrypt a data signal. In physical layer security, secure transmission is satisfied by using the physical characteristics of the wireless channel. Cooperative jamming is one of the efficient techniques to enhance secrecy performance in physical layer security. In cooperative jamming, a cooperating node transmits a jamming signal to interfere the eavesdropper. However, this jamming signal effects not only the eavesdropper but also the destination, which degrades the secrecy performance and causes waste of transmit power. It means the jamming signal transmission needs to be designed properly with optimization and power allocation to enhance security. The dissertation consists of two main results. First, we investigate a two-hop relay network consists of a source, an AF relay, a destination, and an eavesdropper. In this network, cooperative jamming is utilized in which the destination and the source transmit jamming signals in phase 1 and 2, respectively. At the destination, its own jamming signal transmitted in phase 1 is perfectly cancelled, and the jamming signal from the source has negligible strength due to the weak channel condition from the source to destination. We propose an optimal source power allocation for the network to enhance the secrecy performance based on the channel knowledge available at the source. Simulation results show that the proposed source power allocation scheme achieves higher secrecy rate and lower secrecy outage probability than the fixed power allocation schemes. Second, we investigate a two-hop relay network consists of a source, multiple AF relays, a destination, and an eavesdropper. In this network, one relay is selected out of the relays to forwards the data signals. Also, cooperative jamming is utilized in which the destination and the source transmit jamming signals in phase 1 and 2, respectively. We propose power allocation and relay selection scheme to minimize secrecy outage probability with the total power constraint and the power constraints for each phases, respectively. In total power constraint case, power allocation and relay selection problem is formulated and it is divided into a master problem and a subproblem by using the primal decomposition method. Simulation results show that the proposed scheme achieves lower secrecy outage probability than the conventional jamming power allocation scheme as well as without jamming scheme.물리 계층 보안은 무선통신의 보안에 대한 취약점과 암호화의 복잡성이라는 특징으로 인하여, 5세대(5G) 이동통신을 위한 핵심 기술로 간주되고 있다. 물리 계층 보안은 무선 채널의 물리적 특성을 이용하여 보안 통신을 가능하게 한다. 협력 재밍(cooperative jamming)은 물리 계층 보안에서의 보안 성능을 향상시키는 효과적인 기술로, 협력 노드가 재밍 신호를 전송함으로써 도청자를 방해하고, 보안을 달성한다. 그러나, 이러한 재밍 신호는 도청자 뿐 아니라 수신단 역시 방해하게 되므로 과도한 재밍 신호 전송은 보안 성능 향상에 지장을 주고 전력을 낭비하게 된다. 따라서 보안 성능을 향상시키기 위해서는 재밍 신호의 전력 할당 및 최적화를 하는 것이 필수적이다. 본 논문에서의 두 가지 주요한 연구 결과는 다음과 같다. 첫째, 하나의 송신단, 증폭 후 재전송 중계기, 수신단 및 도청자가 존재하는 중계 네트워크를 분석한다. 이 때 수신단 및 송신단이 협력 재밍을 통해 각각 첫 번째 및 두 번째 페이즈에서 재밍 신호를 전송하도록 한다. 수신단이 첫 번째 페이즈에 전송한 재밍 신호는 중계기를 통해 증폭되지만 수신단이 제거할 수 있으며, 송신단의 재밍 신호는 송신단과 수신단 사이의 채널이 약하기 때문에 수신단에 미치지 못한다. 이 때 본 네트워크에서 네트워크의 보안 전송률(secrecy rate) 및 보안 불능 확률(secrecy outage probability)을 향상시키는 송신단의 각 페이즈 별 전송 전력을 송신단이 가진 채널 정보를 통해 최적화한다. 모의 실험을 통해 제안한 전력 할당 기법이 다른 고정 전력 할당 기법에 비해 높은 보안 전송률과 낮은 보안 불능 확률을 달성함을 확인한다. 둘째, 하나의 송신단, 다수의 증폭 후 재전송 중계기들, 하나의 수신단 및 도청자가 존재하는 중계 네트워크를 분석한다. 다수의 중계기 중 하나의 중계기가 선택되어 신호를 전송하게 되며, 협력 재밍을 통해 수신단 및 송신단이 재밍 신호를 전송한다. 이 때 네트워크의 보안 불능 확률을 최소화하기 위한 중계기 선택 및 전력 할당 기법을 다양한 전력 제한에 맞게 분석한다. 네트워크 전체 전력이 제한된 경우에서는 중계기 선택 및 전력 할당 문제를 풀기 위해 두 개의 부문제(subproblem) 로 분할한다. 모의 실험을 통해 제안한 기법이 기존의 기법 및 재밍 신호를 전송하지 않는 기법에 비해 낮은 보안 불능 확률을 달성함을 확인한다.Abstract i 1 Introduction 1 1.1 Background and Related Work 2 1.1.1 Physical Layer Security 2 1.1.2 Cooperative Jamming 3 1.2 Outline of Dissertation 5 1.3 Notations 6 2 Source Power Allocation for Cooperative Jamming in Amplify-and- Forward Relay Network with Eavesdropper 9 2.1 System Model 10 2.2 Source Power Allocation 16 2.2.1 Full CSI for All Links 16 2.2.2 Full CSI for Desired Links only 18 2.3 Simulation Results 23 2.3.1 Identical Channel Condition 23 2.3.2 Non-identical Channel Condition 32 2.3.3 Multiple Antenna Eavesdropper 50 2.4 Summary 50 3 Power Allocation and Relay Selection for Cooperative Jamming in AF Relay Network with Multiple Relays and an Eavesdropper 53 3.1 System Model 55 3.2 Secrecy Outage Probability Analysis 61 3.3 Power Allocation and Relay Selection 66 3.3.1 Total Power Constraint 66 3.3.2 Power Constraints for Each Phases 68 3.4 Numerical Results 70 3.4.1 Multiple Antenna Eavesdropper 86 3.5 Extension to Multiple Relay Selection 86 3.6 Summary 88 4 Conclusion 89 4.1 Summary 89 4.2 Future Works 90 A Obtainment of Optimal Values of alpha in R1 and R2 92 Bibliography 95 Korean Abstract 104Docto

Physical layer security solutions against passive and colluding eavesdroppers in large wireless networks and impulsive noise environments

Wireless networks have experienced rapid evolutions toward sustainability, scalability and interoperability. The digital economy is driven by future networked societies to a more holistic community of intelligent infrastructures and connected services for a more sustainable and smarter society. Furthermore, an enormous amount of sensitive and confidential information, e.g., medical records, electronic media, financial data, and customer files, is transmitted via wireless channels. The implementation of higher layer key distribution and management was challenged by the emergence of these new advanced systems. In order to resist various malicious abuses and security attacks, physical layer security (PLS) has become an appealing alternative. The basic concept behind PLS is to exploit the characteristics of wireless channels for the confidentiality. Its target is to blind the eavesdroppers such that they cannot extract any confidential information from the received signals. This thesis presents solutions and analyses to improve the PLS in wireless networks. In the second chapter, we investigate the secrecy capacity performance of an amplify-andforward (AF) dual-hop network for both distributed beamforming (DBF) and opportunistic relaying (OR) techniques. We derive the capacity scaling for two large sets; trustworthy relays and untrustworthy aggressive relays cooperating together with a wire-tapper aiming to intercept the message. We show that the capacity scaling in the DBF is lower bounded by a value which depends on the ratio between the number of the trustworthy and the untrustworthy aggressive relays, whereas the capacity scaling of OR is upper bounded by a value depending on the number of relays as well as the signal to noise ratio (SNR). In the third chapter, we propose a new location-based multicasting technique, for dual phase AF large networks, aiming to improve the security in the presence of non-colluding passive eavesdroppers. We analytically demonstrate that the proposed technique increases the security by decreasing the probability of re-choosing a sector that has eavesdroppers, for each transmission time. Moreover, we also show that the secrecy capacity scaling of our technique is the same as for broadcasting. Hereafter, the lower and upper bounds of the secrecy outage probability are calculated, and it is shown that the security performance is remarkably enhanced, compared to the conventional multicasting technique. In the fourth chapter, we propose a new cooperative protocol, for dual phase amplify-andforward large wireless sensor networks, aiming to improve the transmission security while taking into account the limited capabilities of the sensor nodes. In such a network, a portion of the K relays can be potential passive eavesdroppers. To reduce the impact of these untrustworthy relays on the network security, we propose a new transmission protocol, where the source agrees to share with the destination a given channel state information (CSI) of source-trusted relay-destination link to encode the message. Then, the source will use this CSI again to map the right message to a certain sector while transmitting fake messages to the other sectors. Adopting such a security protocol is promising because of the availability of a high number of cheap electronic sensors with limited computational capabilities. For the proposed scheme, we derived the secrecy outage probability (SOP) and demonstrated that the probability of receiving the right encoded information by an untrustworthy relay is inversely proportional to the number of sectors. We also show that the aggressive behavior of cooperating untrusted relays is not effective compared to the case where each untrusted relay is trying to intercept the transmitted message individually. Fifth and last, we investigate the physical layer security performance over Rayleigh fading channels in the presence of impulsive noise, as encountered, for instance, in smart grid environments. For this scheme, secrecy performance metrics were considered with and without destination assisted jamming at the eavesdropper’s side. From the obtained results, it is verified that the SOP, without destination assisted jamming, is flooring at high signal-to-noise-ratio values and that it can be significantly improved with the use of jamming

Thirty Years of Machine Learning: The Road to Pareto-Optimal Wireless Networks

Future wireless networks have a substantial potential in terms of supporting a broad range of complex compelling applications both in military and civilian fields, where the users are able to enjoy high-rate, low-latency, low-cost and reliable information services. Achieving this ambitious goal requires new radio techniques for adaptive learning and intelligent decision making because of the complex heterogeneous nature of the network structures and wireless services. Machine learning (ML) algorithms have great success in supporting big data analytics, efficient parameter estimation and interactive decision making. Hence, in this article, we review the thirty-year history of ML by elaborating on supervised learning, unsupervised learning, reinforcement learning and deep learning. Furthermore, we investigate their employment in the compelling applications of wireless networks, including heterogeneous networks (HetNets), cognitive radios (CR), Internet of things (IoT), machine to machine networks (M2M), and so on. This article aims for assisting the readers in clarifying the motivation and methodology of the various ML algorithms, so as to invoke them for hitherto unexplored services as well as scenarios of future wireless networks.Comment: 46 pages, 22 fig

Enable Reliable and Secure Data Transmission in Resource-Constrained Emerging Networks

The increasing deployment of wireless devices has connected humans and objects all around the world, benefiting our daily life and the entire society in many aspects. Achieving those connectivity motivates the emergence of different types of paradigms, such as cellular networks, large-scale Internet of Things (IoT), cognitive networks, etc. Among these networks, enabling reliable and secure data transmission requires various resources including spectrum, energy, and computational capability. However, these resources are usually limited in many scenarios, especially when the number of devices is considerably large, bringing catastrophic consequences to data transmission. For example, given the fact that most of IoT devices have limited computational abilities and inadequate security protocols, data transmission is vulnerable to various attacks such as eavesdropping and replay attacks, for which traditional security approaches are unable to address. On the other hand, in the cellular network, the ever-increasing data traffic has exacerbated the depletion of spectrum along with the energy consumption. As a result, mobile users experience significant congestion and delays when they request data from the cellular service provider, especially in many crowded areas. In this dissertation, we target on reliable and secure data transmission in resource-constrained emerging networks. The first two works investigate new security challenges in the current heterogeneous IoT environment, and then provide certain countermeasures for reliable data communication. To be specific, we identify a new physical-layer attack, the signal emulation attack, in the heterogeneous environment, such as smart home IoT. To defend against the attack, we propose two defense strategies with the help of a commonly found wireless device. In addition, to enable secure data transmission in large-scale IoT network, e.g., the industrial IoT, we apply the amply-and-forward cooperative communication to increase the secrecy capacity by incentivizing relay IoT devices. Besides security concerns in IoT network, we seek data traffic alleviation approaches to achieve reliable and energy-efficient data transmission for a group of users in the cellular network. The concept of mobile participation is introduced to assist data offloading from the base station to users in the group by leveraging the mobility of users and the social features among a group of users. Following with that, we deploy device-to-device data offloading within the group to achieve the energy efficiency at the user side while adapting to their increasing traffic demands. In the end, we consider a perpendicular topic - dynamic spectrum access (DSA) - to alleviate the spectrum scarcity issue in cognitive radio network, where the spectrum resource is limited to users. Specifically, we focus on the security concerns and further propose two physical-layer schemes to prevent spectrum misuse in DSA in both additive white Gaussian noise and fading environments

Stability of secure routing protocol in ad hoc wireless network.

The contributions of this research are threefold. First, it offers a new routing approach to ad hoc wireless network protocols: the Enhanced Heading-direction Angle Routing Protocol (EHARP), which is an enhancement of HARP based on an on-demand routing scheme. We have added important features to overcome its disadvantages and improve its performance, providing the stability and availability required to guarantee the selection of the best path. Each node in the network is able to classify its neighbouring nodes according to their heading directions into four different zone-direction group. The second contribution is to present a new Secure Enhanced Heading-direction Angle Routing Protocol (SEHARP) for ad hoc networks based on the integration of security mechanisms that could be applied to the EHARP routing protocol. Thirdly, we present a new approach to security of access in hostile environments based on the history and relationships among the nodes and on digital operation certificates. We also propose an access activity diagram which explains the steps taken by a node. Security depends on access to the history of each unit, which is used to calculate the cooperative values of each node in the environment