A Survey on Wireless Security: Technical Challenges, Recent Advances and Future Trends

This paper examines the security vulnerabilities and threats imposed by the inherent open nature of wireless communications and to devise efficient defense mechanisms for improving the wireless network security. We first summarize the security requirements of wireless networks, including their authenticity, confidentiality, integrity and availability issues. Next, a comprehensive overview of security attacks encountered in wireless networks is presented in view of the network protocol architecture, where the potential security threats are discussed at each protocol layer. We also provide a survey of the existing security protocols and algorithms that are adopted in the existing wireless network standards, such as the Bluetooth, Wi-Fi, WiMAX, and the long-term evolution (LTE) systems. Then, we discuss the state-of-the-art in physical-layer security, which is an emerging technique of securing the open communications environment against eavesdropping attacks at the physical layer. We also introduce the family of various jamming attacks and their counter-measures, including the constant jammer, intermittent jammer, reactive jammer, adaptive jammer and intelligent jammer. Additionally, we discuss the integration of physical-layer security into existing authentication and cryptography mechanisms for further securing wireless networks. Finally, some technical challenges which remain unresolved at the time of writing are summarized and the future trends in wireless security are discussed.Comment: 36 pages. Accepted to Appear in Proceedings of the IEEE, 201

An Overview of Physical Layer Security with Finite-Alphabet Signaling

Providing secure communications over the physical layer with the objective of achieving perfect secrecy without requiring a secret key has been receiving growing attention within the past decade. The vast majority of the existing studies in the area of physical layer security focus exclusively on the scenarios where the channel inputs are Gaussian distributed. However, in practice, the signals employed for transmission are drawn from discrete signal constellations such as phase shift keying and quadrature amplitude modulation. Hence, understanding the impact of the finite-alphabet input constraints and designing secure transmission schemes under this assumption is a mandatory step towards a practical implementation of physical layer security. With this motivation, this article reviews recent developments on physical layer security with finite-alphabet inputs. We explore transmit signal design algorithms for single-antenna as well as multi-antenna wiretap channels under different assumptions on the channel state information at the transmitter. Moreover, we present a review of the recent results on secure transmission with discrete signaling for various scenarios including multi-carrier transmission systems, broadcast channels with confidential messages, cognitive multiple access and relay networks. Throughout the article, we stress the important behavioral differences of discrete versus Gaussian inputs in the context of the physical layer security. We also present an overview of practical code construction over Gaussian and fading wiretap channels, and we discuss some open problems and directions for future research.Comment: Submitted to IEEE Communications Surveys & Tutorials (1st Revision

Physical Layer Service Integration in 5G: Potentials and Challenges

High transmission rate and secure communication have been identified as the key targets that need to be effectively addressed by fifth generation (5G) wireless systems. In this context, the concept of physical-layer security becomes attractive, as it can establish perfect security using only the characteristics of wireless medium. Nonetheless, to further increase the spectral efficiency, an emerging concept, termed physical-layer service integration (PHY-SI), has been recognized as an effective means. Its basic idea is to combine multiple coexisting services, i.e., multicast/broadcast service and confidential service, into one integral service for one-time transmission at the transmitter side. This article first provides a tutorial on typical PHY-SI models. Furthermore, we propose some state-of-the-art solutions to improve the overall performance of PHY-SI in certain important communication scenarios. In particular, we highlight the extension of several concepts borrowed from conventional single-service communications, such as artificial noise (AN), eigenmode transmission etc., to the scenario of PHY-SI. These techniques are shown to be effective in the design of reliable and robust PHY-SI schemes. Finally, several potential research directions are identified for future work.Comment: 12 pages, 7 figure

An Overview of Physical Layer Security with Finite Alphabet Signaling

Providing secure communications over the physical layer with the objective of achieving secrecy without requiring a secret key has been receiving growing attention within the past decade. The vast majority of the existing studies in the area of physical layer security focus exclusively on the scenarios where the channel inputs are Gaussian distributed. However, in practice, the signals employed for transmission are drawn from discrete signal constellations such as phase shift keying and quadrature amplitude modulation. Hence, understanding the impact of the finite-alphabet input constraints and designing secure transmission schemes under this assumption is a mandatory step towards a practical implementation of physical layer security. With this motivation, this article reviews recent developments on physical layer security with finite-alphabet inputs. We explore transmit signal design algorithms for single-antenna as well as multi-antenna wiretap channels under different assumptions on the channel state information at the transmitter. Moreover, we present a review of the recent results on secure transmission with discrete signaling for various scenarios including multi-carrier transmission systems, broadcast channels with confidential messages, cognitive multiple access and relay networks. Throughout the article, we stress the important behavioral differences of discrete versus Gaussian inputs in the context of the physical layer security. We also present an overview of practical code construction over Gaussian and fading wiretap channels, and discuss some open problems and directions for future research

Low-cost Interference Mitigation and Relay Processing for Cooperative DS-CDMA Systems

In wireless communications, propagation aspects such as fading, shadowing and path loss are the major constraints that seriously limit the overall performance of systems. Indeed, severe fading has a detrimental effect on the received signals and can lead to a degradation of the transmission of information and the reliability of the network. In this case, diversity techniques are introduced in order to mitigate fading. Among various kinds of diversity techniques, cooperative diversity with relaying nodes is a modern technique that has been widely considered in recent years as an effective tool to deal with this problem. Several cooperative protocols have been proposed in the literature, and among the most effective ones are Amplify-and-Forward (AF) and Decode-and-Forward (DF). Cooperative diversity can be combined with direct sequence code division multiple access (DS-CDMA) systems to further enhance the information security. However, due to the multiple access interference (MAI) that arises from nonorthogonal received waveforms in the DS-CDMA systems, the system performance may easily be affected. To deal with this issue, novel multiuser detection (MUD) technique is introduced as a useful relay processing strategy for the uplink of cooperative DS-CDMA systems. Apart from that, distributed space-time coding (DSTC) is another effective approach that can be combined with cooperative diversity to further improve the transmission performance. Moreover, in order to increase the throughput of the cooperative DS-CDMA network, physical-layer network coding (PNC) scheme is then adopted together with the cooperative DS-CDMA network. Clearly, better performance gain and lower power consumption can be obtained when appropriate relaying strategies are applied

Smart Wireless Sensor Networks

The recent development of communication and sensor technology results in the growth of a new attractive and challenging area - wireless sensor networks (WSNs). A wireless sensor network which consists of a large number of sensor nodes is deployed in environmental fields to serve various applications. Facilitated with the ability of wireless communication and intelligent computation, these nodes become smart sensors which do not only perceive ambient physical parameters but also be able to process information, cooperate with each other and self-organize into the network. These new features assist the sensor nodes as well as the network to operate more efficiently in terms of both data acquisition and energy consumption. Special purposes of the applications require design and operation of WSNs different from conventional networks such as the internet. The network design must take into account of the objectives of specific applications. The nature of deployed environment must be considered. The limited of sensor nodes� resources such as memory, computational ability, communication bandwidth and energy source are the challenges in network design. A smart wireless sensor network must be able to deal with these constraints as well as to guarantee the connectivity, coverage, reliability and security of network's operation for a maximized lifetime. This book discusses various aspects of designing such smart wireless sensor networks. Main topics includes: design methodologies, network protocols and algorithms, quality of service management, coverage optimization, time synchronization and security techniques for sensor networks

Towards an enhanced noncoherent massive MU-MIMO system

PhD ThesisMany multiple-input multiple-output (MIMO) downlink transmission schemes assume channel state information (CSI) is available at the receiver/transmitter. In practice, knowledge of CSI is often obtained by using pilot symbols transmitted periodically. However, for some systems, due to high mobility and the cost of channel training and estimation, CSI acquisition is not always feasible. The problem becomes even more difficult when many antennas are used in the system and the channel is changing very rapidly before training is completed. Moreover, as the number of transmit/receive antennas grows large, the number of pilot symbols, system overheads, latency, and power consumption will grow proportionately and thereby the system becomes increasingly complex. As an alternative, a noncoherent system may be used wherein the transmitter/receiver does not need any knowledge of the CSI to perform precoding or detection. This thesis focuses on the design of a noncoherent downlink transmission system to jointly improve the performance and achieve a simple low complexity transmission scheme in three MIMO system scenarios: low rate differential spacetime block coding (STBC) in a downlink multiuser (MU-MIMO) system; high rate differential algebraic STBC in a downlink MU-MIMO system; and differential downlink transmission in a massive MU-MIMO system. Three novel design methods for each of these systems are proposed and analysed thoroughly. For the MIMO system with a low rate noncoherent scheme, a differential STBC MU-MIMO system with a downlink transmission scheme is considered. Specifically, downlink precoding combined with differential modulation (DM) is used to shift the complexity from the receivers to the transmitter. The block diagonalization (BD) precoding scheme is used to cancel co-channel interference (CCI) in addition to exploiting its advantage of enhancing diversity. Since the BD scheme requires channel knowledge at the transmitter, the downlink spreading technique along with DM is also proposed, which does not require channel knowledge neither at the transmitter nor at the receivers. The orthogonal spreading (OS) scheme is employed to have similar principle as code division multiple access (CDMA) multiplexing scheme in order to eliminate the interference between users. As a STBC scheme, the Alamouti code is used that can be encoded/decoded using DM thereby eliminating the need for channel knowledge at the receiver. The proposed schemes yield low complexity transceivers while providing good performance. For the MIMO system with a high rate noncoherent scheme, a differential STBC MU-MIMO system that operates at a high data rate is considered. In particular, a full-rate full-diversity downlink algebraic transmission scheme combined with a differential STBC systems is proposed. To achieve this, perfect algebraic space time codes and Cayley differential (CD) transforms are employed. Since CSI is not needed at the differential receiver, differential schemes are ideal for multiuser systems to shift the complexity from the receivers to the transmitter, thus simplifying user equipment. Furthermore, OS matrices are employed at the transmitter to separate the data streams of different users and enable simple single user decoding. In the OS scheme, the transmitter does not require any knowledge of the CSI to separate the data streams of multiple users; this results in a system which does not need CSI at either end. With this system, to limit the number of possible codewords, a sphere decoder (SD) is used to decode the signals at the receiving end. The proposed scheme yields low complexity transceivers while providing full-rate full-diversity system with good performance. Lastly, a differential downlink transmission scheme is proposed for a massive MIMO system without explicit channel estimation. In particular, a downlink precoding technique combined with a differential encoding scheme is used to simplify the overall system complexity. A novel precoder is designed which, with a large number of transmit antennas, can effectively precancel the multiple access interference (MAI) for each user, thus enhancing the system performance. Maximising the worst case signal-to-interference-plus-noise ratio (SINR) is adopted to optimise the precoder for the users in which full power space profile (PSP) knowledge is available to the base station (BS). Also, two suboptimal solutions based on the matched and the orthogonality approach of PSP are provided to separate the data streams of multiple users. The decision feedback differential detection (DFDD) technique is employed to further improve the performance. In summary, the proposed methods eliminate MAI, enhance system performance, and achieve a simple low complexity system. Moreover, transmission overheads are significantly reduced, the proposed methods avoid explicit channel estimation at both ends.King Fahad Security Collage at the Ministry of Interior - Saudi Arabia

Radio Communications

In the last decades the restless evolution of information and communication technologies (ICT) brought to a deep transformation of our habits. The growth of the Internet and the advances in hardware and software implementations modified our way to communicate and to share information. In this book, an overview of the major issues faced today by researchers in the field of radio communications is given through 35 high quality chapters written by specialists working in universities and research centers all over the world. Various aspects will be deeply discussed: channel modeling, beamforming, multiple antennas, cooperative networks, opportunistic scheduling, advanced admission control, handover management, systems performance assessment, routing issues in mobility conditions, localization, web security. Advanced techniques for the radio resource management will be discussed both in single and multiple radio technologies; either in infrastructure, mesh or ad hoc networks