Cognitive Radio Physical Layer Authentication With Embedded Error Correcting Coding

Cognitive radio technology is an effective scheme to solve the problems of shortage of wireless spectrum resources and diversification of communication standards.In the cognitive radio network system,the primary user has the highest priority level.The secondary user can temporarily substitute the primary user to transmit the data only when the channel is idle.When the primary user needs to use the channel,the secondary user must immediately withdraw from the channel.So the attackers often imitate the primary user to occupy the channel illegally.In order to solve the problem of imitation attacks,it is necessary to authenticate the identity of the primary user before the access to the channel.In modern wireless communication system,the signal authentication on layers above the physical layer is inefficient and slow because of complex analysis operation to the signals.However,the physical layer authentication technology can solve these problems.It uses the one-way character of Hash function to effectively solve the primary user authentication problem with directly detect on the physical layer signals.Meanwhile it can realize the hidden transmission of the authentication with physical layer low-rate transmission to minimize the interference to legitimate users.It can strengthen the security of the wireless network in case of attackers' access.In this paper,we focus on two methods for embedding authentication tags in cognitive radio physical layer security authentication: embedded modulation and embedded error correct coding(ECC).The main research work and innovation of this paper are as follows:(1)At first,the modulation scheme in cognitive radio physical layer security authentication is studied.The capacity of embedded authentication channel in cognitive radio is investigated.By employing the log-likelihood ratios(LLRs)of a tag bit and its approximation,we show that the equivalent authentication channel observed by the secondary receiver can be viewed as a binary-input additive white Gaussian noise(BI-AWGN)channel.(2)We investigate the practical performance of the embedded authentication channel with the use of LDPC coding.With the approximate form of LLRs,we find that it performs very close to decoding performance of the ideal BI-AWGN channel.Hence,we conclude that a good error-control coding scheme for a BI-AWGN channel is also good for embedded authentication channel.(3)The encoding scheme in cognitive radio physical layer security authentication is studied.We propose to use LDPC coding schemes for the ECC tagging approach,where both the main and tag channels are protected by the powerful LDPC codes.Then,the proposed LDPC-ECC tagging approach is compared to that of the reported RS-ECC tagging approach,where the Reed-Solomn coding scheme is employed.According to the simulation results,the performance of the LDPC-ECC scheme is better than the RS-ECC scheme.(4)The modulation tagging is compared to the ECC tagging in both performance of the probability of error and transmitting rate of tags.It is shown that under the same error rate and SNR,the QPSK modulation tagging is superior to that of the ECC tagging whenever the transmission time is concerned.