Van-Tam Nguyen

Surveillance Strategies Against Primary User Emulation Attack in Cognitive Radio Networks

We investigate the primary user emulation (PUE) attack, which is a serious security problem in cognitive radio (CR) networks. There exist three types of PUE attackers: 1) a selfish one, which aims at maximizing its selfish usage of channel resource; 2) a malicious one, which points for obstructing the operation of CR network; and 3) a mixed one, which is between a selfish and malicious PUE attacker. For combating a selfish PUE attacker, a channel surveillance process has to be implemented in order to determine active users identification and so selfish PUE attacker. An extra-sensing process has to be implemented for observing new opportunities to access the channel and so for mitigating the malicious PUE attackers effect. Relevant strategies for deploying the above processes are obtained through a game theory-based analysis and the exhibition of Nash equilibrium (NE). We show the NE strongly depends on the network demand, the availability of the spectrum resource, and the type of the attacker.

How Many Bits Should Be Reported In Quantized Cooperative Spectrum Sensing

We introduce an algorithm for optimizing sensing parameters including the number of sensing samples and the number of reporting bits of a quantization-based cooperative spectrum sensing scheme in cognitive radio networks. This is obtained by maximizing the network throughput subject to a target detection probability. With Rayleigh fading and energy detector, the proposed algorithm simultaneously optimizes the number of sensing samples at a local node, the number of bits for quantizing local sensing data and the global threshold at a fusion center.

A novel digital calibration technique for gain and offset mismatch in parallel TIΣΔ ADCs

Time interleaved sigma-delta architecture is a potential candidate for high bandwidth analog to digital converters required for reconfigurable, versatile and multistandard receivers. However, this architecture is very sensitive to the unavoidable gain and offset mismatch resulting from the manufacturing process. This paper presents a novel digital calibration method for gain and offset mismatch. This new method takes advantage of the digital signal processing on each channel to reconstruct the useful signal and requires only few logic components for implementation. The run time calibration is estimated to 10 and 15 clock cycles for offset and gain mismatches respectively.

A 65 nm CMOS versatile ADC using time interleaving and ΣΔ modulation for multi-mode receiver

High performances wideband Analog to Digital Converter (ADC) remains a bottleneck to realize software and cognitive radio receivers. Time Interleaved Sigma-Delta (TIΣΔ) architecture is a good candidate to increase the bandwidth of the data converters with the lowest hardware complexity compared to other solutions using parallel sigma-delta modulators. This paper proposes a reconfigurable 4 channels TIΣΔ using the novel GMSCL (General Multi Stage Closed Loop) sigma-delta architecture and a new digital processing reducing considerably the hardware complexity. The sigma-delta modulators have been designed using switched-capacitor technique and implemented with STMicroelectronis 65 nm CMOS technology. Three different scenarios are possible : the first one for GSM standard clocked at 26 MHz and consumes 2.59 mW, the second one for UMTS/DVB-T standards clocked at 208 MHz and consumes 46 mW and the last one for WiFi/WiMax standards clocked at 208 MHz and consumes 92 mW. The total circuit die area is equal to 3 mm2. The digital filtering was validated and synthesized in a 1.2 V, 65 nm CMOS process using VHDL language. For a clock rate of 208 MHz, the evaluated die area is 0.115 mm2.

Extra-sensing game for malicious primary user emulator attack in cognitive radio network

Primary User Emulation (PUE) attack is a serious security problem in cognitive radio (CR) network. A PUE attacker emulates a primary signal during sensing duration in order the CR users not to use the spectrum. The PUE attacker is either selfish if it would like to take benefit of the spectrum, or malicious if it would like to do a Deny of Service of the CR network. In this paper, we only consider malicious PUE. We propose to perform sometimes an additional sensing step, called extra-sensing, in order to have a new opportunity to sense the channel and so to use it. Obviously the malicious PUE may still perform an attack during this extra-sensing. Therefore, our problem can be formulated as a zero-sum game to modeling and analyzing the strategies for two players. The equilibrium is expressed in closed-form. The results show that the benefit ratio and the probability of channels availability strongly influence the equilibrium. Numerical results confirm our claims.

Attack and surveillance strategies for selfish primary user emulator in cognitive radio network

Primary user emulation (PUE) attack is a serious security problem in cognitive radio (CR) networks. In PUE attack, attacker transmits an emulated primary signal during a spectrum sensing interval to fool the CR system causing a prohibition in the secondary access on the attacked channel. An attacker is called selfish attacker if it performs the PUE attack for its selfish own purpose. Since it is obligate to reveal the users identification in any communication link, a channel surveillance process can help to identify the selfish PUE attacker. In this paper, we formulate a non-zero-sum game with incomplete information for analyzing and modeling the selfish PUE attack and surveillance strategies simultaneously. Nash Equilibrium (NE) is figured out in closed form. The results show that the network demand and the penalty factor strongly influence the NE. Numerical simulations confirm our claims based on our analytic results.

Mitigating Primary Emulation Attacks in Multi-Channel Cognitive Radio Networks: A Surveillance Game

Primary User Emulation Attack (PUEA), in which attackers emulate primary user signals causing restriction of secondary access on the attacked channels, is a serious security problem in Cognitive Radio Networks (CRNs). A user performing a PUEA for selfishly occupying more channels is called a selfish PUEA attacker. Network managers could adopt a surveillance process on disallowed channels for identifying illegal channel occupation of selfish PUEA attackers and hence mitigating selfish PUEA. Determining surveillance strategies, particularly in multichannel context, is necessary for ensuring network operation fairness. In this paper, we formulate a game, called multi-channel surveillance game, between the selfish attack and the surveillance process in multi-channel CRNs. The sequence-form representation method is adopted to determine the Nash Equilibrium (NE) of the game. We show that performing the obtained NE surveillance strategy significantly mitigates selfish PUEA.

An energy minimization algorithm for cooperative spectrum sensing

We introduce an algorithm minimizing the consumed energy of a cooperative spectrum sensing-based cognitive radio network. The energy is minimized, while satisfying requirements for primary user protection and for secondary user data rate simultaneously, with respect to the powers for transmitting on control and data channels, the number of reported bits, and the thresholds of the global sensing test. Control and data channels are assumed not to be error-free. Simulation results finally confirm our claims.

A digital correction technique for channel mismatch in TI ΣΔ ADCs

Time interleaved sigma-delta analog to digital converter seems to be a potential solution for wide bandwidth analog to digital converter with the lowest hardware complexity compared to other solutions using parallel sigma-delta modulators. Its performance depends on the digital filter and is very sensitive to the channel mismatch. This paper summarizes our work on the digital signal processing for this kind of converter, including filtering, decimation and channel mismatch correction in order to reduce the implementation complexity while minimizing the channel mismatch effect.