Wireless Physical Layer Research Articles

Multi-antenna relay aided wireless physical layer security

With the growing popularity of mobile Internet, providing secure wireless services has become a critical issue. Physical layer security (PHY-security) has been recognized as an effective means to enhance wireless security by exploiting wireless medium characteristics, for example, fading, noise, and interference. A particularly interesting PHY-security technology is cooperative relay due to the fact that it helps to provide distributed diversity and shorten access distance. This article offers a tutorial on various multi-antenna relaying technologies to improve security at physical layer. The state-of-the-art research results on multi-antenna relay aided PHY-security as well as some secrecy performance optimization schemes are presented. In particular, we focus on large-scale MIMO relaying technology, which is effective in tackling various challenging issues for implementing wireless PHY-security, such as short-distance interception without eavesdropper CSI and with imperfect legitimate CSI. Moreover, the future directions are identified for further enhancement of secrecy performance.

Full-Duplex Relay for Enhancing Physical Layer Security in Multi-Hop Relaying Systems

In this letter, we consider secure communications in multi-hop relaying systems, where full-duplex relays (FDRs) operate to enhance wireless physical layer security. Each FDR is designed to transmit jamming signals to the eavesdropper when it receives information signals from the previous adjacent node. The achievable secrecy rate with the proposed decode-and-forward (DF) FDRs are analyzed with a total transmit power constraint. The transmit power allocation problem is solved by using the geometric programming (GP) method. Numerical results present that the proposed FDRs significantly enhance the secrecy rate compared to the conventional half-duplex relays (HDRs).

Ziria

Software-defined radio (SDR) brings the flexibility of software to wireless protocol design, promising an ideal platform for innovation and rapid protocol deployment. However, implementing modern wireless protocols on existing SDR platforms often requires careful hand-tuning of low-level code, which can undermine the advantages of software. Ziria is a new domain-specific language (DSL) that offers programming abstractions suitable for wireless physical (PHY) layer tasks while emphasizing the pipeline reconfiguration aspects of PHY programming. The Ziria compiler implements a rich set of specialized optimizations, such as lookup table generation and pipeline fusion. We also offer a novel -- due to pipeline reconfiguration -- algorithm to optimize the data widths of computations in Ziria pipelines. We demonstrate the programming flexibility of Ziria and the performance of the generated code through a detailed evaluation of a line-rate Ziria WiFi 802.11a/g implementation that is on par and in many cases outperforms a hand-tuned state-of-the-art C++ implementation on commodity CPUs.

Ziria

Software-defined radio (SDR) brings the flexibility of software to wireless protocol design, promising an ideal platform for innovation and rapid protocol deployment. However, implementing modern wireless protocols on existing SDR platforms often requires careful hand-tuning of low-level code, which can undermine the advantages of software. Ziria is a new domain-specific language (DSL) that offers programming abstractions suitable for wireless physical (PHY) layer tasks while emphasizing the pipeline reconfiguration aspects of PHY programming. The Ziria compiler implements a rich set of specialized optimizations, such as lookup table generation and pipeline fusion. We also offer a novel -- due to pipeline reconfiguration -- algorithm to optimize the data widths of computations in Ziria pipelines. We demonstrate the programming flexibility of Ziria and the performance of the generated code through a detailed evaluation of a line-rate Ziria WiFi 802.11a/g implementation that is on par and in many cases outperforms a hand-tuned state-of-the-art C++ implementation on commodity CPUs.

MASK-BAN: Movement-Aided Authenticated Secret Key Extraction Utilizing Channel Characteristics in Body Area Networks

Recently, most wireless network security schemes merely based on physical layer characteristics tackle the two fundamental issues-device authentication and secret key extraction separately. It remains an open problem to simultaneously achieve device authentication and fast secret key extraction merely using wireless physical layer characteristics, without the help of advanced hardware or out-of-band channel. In this paper, we answer this open problem in the setting of wireless body area networks (BANs). We propose MASK-BAN, a lightweight fast authenticated secret key extraction scheme for intra-BAN communication. Our scheme neither introduces advanced hardware nor relies on out-of-band channels. To perform device authentication and fast secret key extraction at the same time, we exploit the heterogeneous channel characteristics among the collection of on-body channels during body motion. On one hand, MASK-BAN achieves authentication through multihop stable channels, which greatly reduces the false positive rate as compared to existing work. On the other hand, based on dynamic channels, key extraction between two on-body devices with multihop relay nodes is modeled as a max-flow problem, and a novel collaborative secret key generation algorithm is introduced to maximize the key generation rate. Extensive real-world experiments on low-end commercial-off-the-shelf sensor devices validate MASK-BAN's great authentication capability and high-secret key generation rate.

A Novel Method of Modeling Wireless Sensor Network Using Fuzzy Graph and Energy Efficient Fuzzy Based k-Hop Clustering Algorithm

Clustering is one of the widely used methods to save energy, increase spatial re usability, and scalability. In this paper, we have proposed a new fuzzy graph based modeling approach for wireless sensor network which takes into account the dynamic nature of network, volatile aspects of radio links and physical layer uncertainty. The fuzzy graph constructs fuzzy neighborhoods which are used to identify all the prospective member nodes of a cluster. For computation of optimum centrality of a cluster, we have defined a new centrality metric namely fuzzy k-hop centrality. The proposed centrality metric considers residual energy of individual nodes, link quality, hop distance between the prospective cluster head and respective member nodes to ensure better cluster head selection and cluster quality. Finally, a new computationally inexpensive clustering algorithm has been developed. The simulation results demonstrate that the proposed algorithm resulted in prolonged network lifetime in terms of clustering rounds, scalability, higher energy efficiency and uniform cluster head and cluster members distribution, as compare to LEACH-ERE and CHEF.

Polling in the frequency domain: a new MAC protocol for industrial wireless network for factory automation

Wireless technologies are becoming more and more attractive for industrial communication. In the field of factory automation, the high communication requirements in terms of predictability, reliability and real-time make the adoption of wireless technologies challenging, due to the inefficiency of the wireless physical layer and deterministic medium access control MAC protocols. In this paper, a frequency domain polling MAC protocol FDP-MAC is proposed, which takes advantage of the orthogonal frequency-division multiplexing OFDM technology to achieve simultaneously polling. In the FDP-MAC, a dynamic time division multiple access TDMA scheduling and a downlink acknowledgements aggregation method are also presented to improve the communication efficiency further. We validate the effectiveness of FDP-MAC through simulations, and results indicate that FDP-MAC can meet typical factory automation applications' communication requirements.

Wireless infrastructure protection using low-cost radio frequency fingerprinting receivers

Low-data-rate wireless networks incorporated in critical infrastructure applications can be protected through 128-bit encryption keys and address-based access control lists. However, these bit-level credentials are vulnerable to interception, extraction and spoofing using software tools available free of charge on the Internet. Recent research has demonstrated that wireless physical layer device fingerprinting can be used to defend against replay and spoofing attacks. However, radio frequency (RF) fingerprinting typically uses expensive signal collection systems; this is because fingerprinting wireless devices with low-cost receivers has been reported to have inconsistent accuracy. This paper demonstrates a robust radio frequency fingerprinting process that is consistently accurate with both high-end and low-cost receivers. Indeed, the results demonstrate that low-cost software-defined radios can be used to perform accurate radio frequency fingerprinting and to identify spoofing attacks in critical IEEE 802.15.4-based infrastructure networks such as ZigBee.

Timestamp Validation Strategy for Wireless Sensor Networks Based on IEEE 802.15.4 CSS

Network time distribution relies on timestamping, which is employed by local nodes to assign a time value to incoming timing packets. Clearly, any error affecting the timestamp has a direct impact on the final synchronization accuracy of the system. In wireless sensor networks (WSNs), impairments affecting the wireless physical layer are the primary cause of such timestamping errors, and it would be advantageous to flag suspect timestamp values before feeding them into a synchronization algorithm. This paper discusses a new strategy for validating timestamps in a WSN based on IEEE 802.15.4 chirp spread spectrum. The considered system employs physical-level timestamping, which generates one timestamp for each symbol belonging to a packet. Such set of timestamps is processed using a Kalman filter (KF) that compares them with predicted values, employing statistical thresholds referred to the KF innovation process. Experimental results obtained over a long observation period shows that even in a noisy environment with several interfering communication sources, the algorithm is able to detect untrusted timestamps.

Securing While Sampling in Wireless Body Area Networks With Application to Electrocardiography.

Stringent resource constraints and broadcast transmission in wireless body area network raise serious security concerns when employed in biomedical applications. Protecting data transmission where any minor alteration is potentially harmful is of significant importance in healthcare. Traditional security methods based on public or private key infrastructure require considerable memory and computational resources, and present an implementation obstacle in compact sensor nodes. This paper proposes a lightweight encryption framework augmenting compressed sensing with wireless physical layer security. Augmenting compressed sensing to secure information is based on the use of the measurement matrix as an encryption key, and allows for incorporating security in addition to compression at the time of sampling an analog signal. The proposed approach eliminates the need for a separate encryption algorithm, as well as the predeployment of a key thereby conserving sensor node's limited resources. The proposed framework is evaluated using analysis, simulation, and experimentation applied to a wireless electrocardiogram setup consisting of a sensor node, an access point, and an eavesdropper performing a proximity attack. Results show that legitimate communication is reliable and secure given that the eavesdropper is located at a reasonable distance from the sensor node and the access point.

Detection of man‐in‐the‐middle attacks using physical layer wireless security techniques

AbstractCompared with a wired network, a wireless network is not protected by the cable transmission medium. Information is broadcasted over the air and it can be intercepted by anyone within the transmission range. Even though the transmissions could potentially be protected by security authentication mechanisms, malicious users can still intercept the information by mimicking the characteristics of normal user or a legitimate access point. This scenario is referred as a man‐in‐the‐middle (MITM) attack. In the MITM attack, the attackers can bypass the security mechanisms, intercept the unprotected transmission packets, and sniff the information. Because of several vulnerabilities in the IEEE 802.11 protocol, it is difficult to defend against a wireless MITM attack. In this paper, a received signal strength indicator (RSSI)‐based detection mechanism for MITM attacks is proposed. RSSI information is an arbitrary integer that indicates the power level being received by the antenna. The random RSSI values are processed via a sliding window, yielding statistic information about the signal characteristics such as mean and standard deviation profiles. By analyzing those profiles, the detection mechanism can detect if a rogue access point, the key component of an MITM attack, is launched. Our proposed approach has been validated via hardware experimentation using Backtrack 5 tools and MATLAB software suite. Copyright © 2014 John Wiley & Sons, Ltd.

Evaluating transport protocol performance over a wireless mesh backbone

IEEE 802.11n wireless physical layer technology increases the deployment of high throughput wireless indoor mesh backbones for ubiquitous Internet connectivity at the urban and metropolitan areas. Most of the network traffic flows in today’s Internet use ‘Transmission Control Protocol’ (TCP) as the transport layer protocol. There has been extensive works that deal with TCP issues over wireless mesh networks as well as noisy wireless channels. Further, IEEE 802.11n is well known for its susceptibility to increased channel losses during high data rate communication. This paper investigates the dynamics of an end-to-end transport layer protocol like TCP in the presence of burst and correlated losses during IEEE 802.11n high data rate communication, while maintaining fairness among all the end-to-end flows. For this purpose, we evaluate four TCP variants-Loss Tolerant TCP (LT-TCP), Network Coded TCP (TCP/NC), TCP-Horizon and Wireless Control Protocol (WCP), where the first two protocols are known to perform very well in extreme lossy networks, and the last two are specifically designed for mesh networks. Our evaluation shows that WCP performs better in a IEEE 802.11n supported mesh networks compared to other three variants. However, WCP also results in negative impact at high data rates, where end-to-end goodput drops with the increase in physical data rate. The analysis of the results reveals that explicit loss notifications and flow balancing are not sufficient to improve transport protocol performance in an IEEE 802.11n supported mesh backbone, rather a specific mechanism is required to synchronize the transport queue management with lower layer scheduling that depends on IEEE 802.11n features, like channel bonding and frame aggregation. The findings of this paper give the direction to design a new transport protocol that can utilize the full capacity of IEEE 802.11n mesh backbone.

A Hybrid Scheme for Wireless Physical Layer Security Based on Encryption and Channel Pre-compensation

ABSTRACTIn this paper, a hybrid scheme to provide wireless physical layer security based on encryption and wireless channel pre-compensation is presented. The physical layer security is provided by converting the signal constellation into a higher order constellation by using conventional encryption (symmetric key encryption) and then using channel state information (i.e. amplitude and phase variation), which is location specific, to further encrypt the constellation before transmission. Since detection and demodulation are based upon the known signal constellation, which is not known in advance in our case, it becomes difficult for the eavesdropper to determine the original signal constellation. The data intercepted by the eavesdropper is unintelligible due to the combined effect of encryption and pre-compensation. Using bit error rate (BER) as performance metric, it is found that the eavesdropper suffers from high BER as compared to its legitimate counterpart hence providing secure communication. The developed scheme was tested with existing wireless communication standard IEEE 802.11 to show the practical application of the scheme.

CSI-Secured Orthogonal Jamming Method for Wireless Physical Layer Security

In this paper, we propose a new cooperative jamming (CJ) method to prevent eavesdroppers from using beam-formers to suppress the jamming signals. In this method, the broadcasting of system-node channel state information (CSI) is first averted. The transmitting and jamming signals are then aligned in two separate single dimensions in complex space. The decode-and-forward relaying protocol is employed.The proposed method is more effective than current CJ techniques.

An Agile Digital Radio System for UHF White Spaces

In recent years, we have experienced an impressive spread of mobile communications as well as the emergence of new communication protocols. This lead to an overutilization of some spectrum bands, while the utilization of other bands is sometimes minimal or insignificant. The exploration of the white spaces concept, which represents the unused portions of the spectrum, mainly due to the shutdown of analog TV transmissions, has arisen as a solution for spectrum reuse. Currently, the electromagnetic spectrum is statically allocated, associating each technology to a particular frequency band, which leads to an inefficient use of the spectrum. Thus, it would be advantageous to change the way the electromagnetic spectrum is accessed, adopting a dynamic access paradigm-dynamic spectrum access (DSA). However, for this to be possible, in addition to regulatory changes, it is necessary that the radio physical layer becomes flexible and adaptable, enabling the efficient configuration of various parameters such as transmit frequency and power, modulation, and bandwidth, among others. The well-known concepts or paradigms of software defined radio (SDR) and cognitive radio (CR) are precisely the key to meeting these requirements. Based on these concepts, it will be possible to build a smart, adaptable, efficient, self-aware, and self-learning radio that could easily implement the DSA paradigm [1].

A Hiding Algorithm for OFDM Constellation Mapping Based on Wireless Physical Layer Encryption

A Hiding Algorithm for OFDM Constellation Mapping Based on Wireless Physical Layer Encryption

A STUDY OF ZIGBEE TECHNOLOGY

The zigbee communication is a communication technology to connect local wireless nodes and provides high stability and transfer rate due to data communication with low power. In the nodes away from coordinator in one PAN, the signal strength is weak causing the network a shortage of low performance and inefficient use of resources due to transferring delay and increasing delay time and thus cannot conduct seamless communication. This study suggests the grouping method, that makes it possible to perform wide range data transferring depending on the node signal strength in zigbee node and analyzes the suggested algorithm through simulation. Based on IEEE 802.15.4 Low Rate-Wireless Personal Area Network (LR-WPAN) standard, the Zigbee standard has been proposed to interconnect simple, low rate and battery powered wireless devices. The de-ployment of Zigbee networks is expected to facilitate numerous applications such as Home-appliance net-works, home healthcare, medical monitoring and environmental sensors. An effective routing scheme is more important for Zigbee mesh networks. In order to achieve effective routing in Zigbee Mesh networks, a Zigbee protocol module is realized using NS-2. The suitable routing for different data services in the Zigbee application layer and a best routing strategy for Zigbee mesh network are proposed. The ZigBee standard provides network, security, and application support services operating on top of the IEEE 802.15.4 Medium AccessControl (MAC) and Physical Layer wireless standard. It employs a group of technologies to enable scalable, self-organizing, self-healing networks that can manage various data traffic patterns. ZigBee is a low-cost, low-power, wireless mesh networking standard. The low costal lows the technologyto be widely deployed in wireless control and monitoring applications, the low power-usage allows longerlife with smaller batteries, and the mesh networking which promises high reliability and larger range. ZigBee has-been developed to meet the growing demand for capable wireless networking between numerous low power devices. The aims of this network are to reduce the energy consumption and latency by enhancing routing algorithm. In a traditional tree routing when a node wants to transmit a packet to the destination, the packet has to follow child/parent relationship and go along tree topology, even if the destination is lying at nearby source. In order to solve this problem, an Enhanced Tree Routing Algorithm is introduced using ZigBee network. This algorithm can find the shortest path by computing the routing cost for all of router that stored in neighbor table, and transmit the packet to the neighbor router that can reduce the hop count of transmission. The enhanced tree routing algorithm can achieve more stable and better efficiency then the previous traditional tree routing algorithm.

Hybrid relaying and jamming for wireless physical layer security based on cooperative beamforming

To improve the information-theoretic security of two-way wireless cooperative communication systems, we propose in this study a hybrid relaying and jamming mechanism based on multi-node cooperative beamforming to enhance the security of the physical layer transmission of information. The basic concept is that in the cooperative transmission phase, some intermediate nodes adopt distributed beamforming to help the transmitter send messages to legitimate users and simultaneously others jam the eavesdropper, which can significantly improve the security performance of the system in the broadcast phase. Two different cooperative beamforming schemes are proposed with and without the instantaneous channel state information (CSI) of the eavesdropper. We show that optimizing both the schemes requires the mathematical solving of one or a series of second-order convex cone programming (SOCP) problems, which can be executed by efficiently using the interior point method. Simulation and comparisons show that our proposed hybrid relaying, jamming mechanism and beamforming approaches significantly increase the security sum rate of the two source terminals and outperform both the relays-only and jammers-only mechanisms when the number of intermediate nodes is relatively large.

Destination Assisted Cooperative Jamming for Wireless Physical-Layer Security

A wireless network with one source, one destination, one eavesdropper, and multiple decode-and-forward relays is considered. A two-slot cooperative relaying scheme is proposed that targets at maximizing the secrecy rate. In the first slot, the source transmits the information bearing signal, and at the same time, it cooperates with the destination in jamming the eavesdropper without creating interference at the relay. In the second slot, one optimally selected relay retransmits the decoded source signal, and at the same time, that particular relay cooperates with the source to jam the eavesdropper without creating interference at the destination. Optimal relay selection and also optimal power allocation among the first/second slot data signal and jamming noise are proposed. It is shown that the secrecy rate of the proposed scheme scales with the total system power P0 and the number of available relays K according to 1/2log2(1 + P0 /8logK) - 1.6 bits/channel use . Although the proposed power allocation and relay selection assume global CSI available, the performance under imperfect relay CSI is also investigated. Also, the performance under distributed relay selection with limited feedback is demonstrated.

Network properties of mobile tactical scenarios

The mobile tactical network is a practical implementation of the mobile ad hoc network. Formed across tactical radios operating in the military very high frequency and low ultrahigh frequency bands, the mobile tactical network has distinctive characteristics when compared with generic mobile ad hoc networks, in particular with respect to its network topological behaviors and connectivity attributes. These characteristics must be understood and considered when selecting suitable network protocols. To this end, in this paper, a network science-based systematic modeling approach is applied to analyze typical deployment scenarios and identify fundamental tactical network properties. The novel framework employs realistic scenario models as well as radio physical layer performance parameters and channel models to effectively capture the dynamic network behavior that needs to be considered for protocol design. The results provide critical insights and guidance to the development of tactical network solutions. © Her Majesty the Queen in Right of Canada 2013