7 research outputs found
Byzantine Attack and Defense in Cognitive Radio Networks: A Survey
The Byzantine attack in cooperative spectrum sensing (CSS), also known as the
spectrum sensing data falsification (SSDF) attack in the literature, is one of
the key adversaries to the success of cognitive radio networks (CRNs). In the
past couple of years, the research on the Byzantine attack and defense
strategies has gained worldwide increasing attention. In this paper, we provide
a comprehensive survey and tutorial on the recent advances in the Byzantine
attack and defense for CSS in CRNs. Specifically, we first briefly present the
preliminaries of CSS for general readers, including signal detection
techniques, hypothesis testing, and data fusion. Second, we analyze the spear
and shield relation between Byzantine attack and defense from three aspects:
the vulnerability of CSS to attack, the obstacles in CSS to defense, and the
games between attack and defense. Then, we propose a taxonomy of the existing
Byzantine attack behaviors and elaborate on the corresponding attack
parameters, which determine where, who, how, and when to launch attacks. Next,
from the perspectives of homogeneous or heterogeneous scenarios, we classify
the existing defense algorithms, and provide an in-depth tutorial on the
state-of-the-art Byzantine defense schemes, commonly known as robust or secure
CSS in the literature. Furthermore, we highlight the unsolved research
challenges and depict the future research directions.Comment: Accepted by IEEE Communications Surveys and Tutoiral
Practical Secrecy at the Physical Layer: Key Extraction Methods with Applications in Cognitive Radio
The broadcast nature of wireless communication imposes the risk of information leakage to adversarial or unauthorized receivers. Therefore, information security between intended users remains a challenging issue. Currently, wireless security relies on cryptographic techniques and protocols that lie at the upper layers of the wireless network. One main drawback of these existing techniques is the necessity of a complex key management scheme in the case of symmetric ciphers and high computational complexity in the case of asymmetric ciphers. On the other hand, physical layer security has attracted significant interest from the research community due to its potential to generate information-theoretic secure keys. In addition, since the vast majority of physical layer security techniques exploit the inherent randomness of the communication channel, key exchange is no longer mandatory. However, additive white Gaussian noise, interference, channel estimation errors and the fact that communicating transceivers employ different radio frequency (RF) chains are among the reasons that limit utilization of secret key generation (SKG) algorithms to high signal to noise ratio levels. The scope of this dissertation is to design novel secret key generation algorithms to overcome this main drawback. In particular, we design a channel based SKG algorithm that increases the dynamic range of the key generation system. In addition, we design an algorithm that exploits angle of arrival (AoA) as a common source of randomness to generate the secret key. Existing AoA estimation systems either have high hardware and computation complexities or low performance, which hinder their incorporation within the context of SKG. To overcome this challenge, we design a novel high performance yet simple and efficient AoA estimation system that fits the objective of collecting sequences of AoAs for SKG.
Cognitive radio networks (CRNs) are designed to increase spectrum usage efficiency by allowing secondary users (SUs) to exploit spectrum slots that are unused by the spectrum owners, i.e., primary users (PUs). Hence, spectrum sensing (SS) is essential in any CRN. CRNs can work both in opportunistic (interweaved) as well as overlay and/or underlay (limited interference) fashions. CRNs typically operate at low SNR levels, particularly, to support overlay/underlay operations. Similar to other wireless networks, CRNs are susceptible to various physical layer security attacks including spectrum sensing data falsification and eavesdropping. In addition to the generalized SKG methods provided in this thesis and due to the peculiarity of CRNs, we further provide a specific method of SKG for CRNs. After studying, developing and implementing several SS techniques, we design an SKG algorithm that exploits SS data. Our algorithm does not interrupt the SS operation and does not require additional time to generate the secret key. Therefore, it is suitable for CRNs
Compressive Sensing Over TV White Space in Wideband Cognitive Radio
PhDSpectrum scarcity is an important challenge faced by high-speed wireless communications.
Meanwhile, caused by current spectrum assignment policy, a large portion of
spectrum is underutilized. Motivated by this, cognitive radio (CR) has emerged as one
of the most promising candidate solutions to improve spectrum utilization, by allowing
secondary users (SUs) to opportunistically access the temporarily unused spectrum,
without introducing harmful interference to primary users. Moreover, opening of TV
white space (TVWS) gives us the con dence to enable CR for TVWS spectrum. A crucial
requirement in CR networks (CRNs) is wideband spectrum sensing, in which SUs
should detect spectral opportunities across a wide frequency range. However, wideband
spectrum sensing could lead to una ordably high sampling rates at energy-constrained
SUs. Compressive sensing (CS) was developed to overcome this issue, which enables
sub-Nyquist sampling by exploiting sparse property. As the spectrum utilization is low,
spectral signals exhibit a natural sparsity in frequency domain, which motivates the
promising application of CS in wideband CRNs.
This thesis proposes several e ective algorithms for invoking CS in wideband CRNs.
Speci cally, a robust compressive spectrum sensing algorithm is proposed for reducing
computational complexity of signal recovery. Additionally, a low-complexity algorithm is
designed, in which original signals are recovered with fewer measurements, as geolocation
database is invoked to provide prior information. Moreover, security enhancement issue
of CRNs is addressed by proposing a malicious user detection algorithm, in which data
corrupted by malicious users are removed during the process of matrix completion (MC).
One key spotlight feature of this thesis is that both real-world signals and simulated
signals over TVWS are invoked for evaluating network performance. Besides invoking
CS and MC to reduce energy consumption, each SU is supposed to harvest energy from radio frequency. The proposed algorithm is capable of o ering higher throughput by
performing signal recovery at a remote fusion center
SPATIAL TRANSFORMATION PATTERN DUE TO COMMERCIAL ACTIVITY IN KAMPONG HOUSE
ABSTRACT Kampung houses are houses in kampung area of the city. Kampung House oftenly transformed into others use as urban dynamics. One of the transfomation is related to the commercial activities addition by the house owner. It make house with full private space become into mixused house with more public spaces or completely changed into full public commercial building. This study investigate the spatial transformation pattern of the kampung houses due to their commercial activities addition. Site observations, interviews and questionnaires were performed to study the spatial transformation. This study found that in kampung houses, the spatial transformation pattern was depend on type of commercial activities and owner perceptions, and there are several steps of the spatial transformation related the commercial activity addition.
Keywords: spatial transformation pattern; commercial activity; owner perception, kampung house; adaptabilit