IEEE International Conference on Internet of Things (iThings) and IEEE Green Computing and Communications (GreenCom) and IEEE Cyber, Physical and Social Computing (CPSCom) and IEEE Smart Data (SmartData)
Secure Communication Based on a Modified RB-HARQ Protocol
This paper presents a secure communication scheme based on a modified Reliability-Based Hybrid Automatic Repeat reQuest (RB-HARQ) protocol over the additive white Gaussian noise (AWGN) wiretap channel. RB-HARQ protocol is firstly implemented in the secure communication system and showed a significant enhancement of the physical layer security. The retransmission encoding scheme is the main difference between traditional RB-HARQ and modified RB-HARQ, which can encode the unreliable bits of the authorized user (Bob) and retransmit the encoded unreliable bits through the AWGN wiretap channel. With the retransmission encoding scheme, the maximum retransmission number of RB-HARQ protocol can be largely reduced and secure communication can still be ensured, which is much more practical in long distance communication system. Bit error rate (BER) at both the authorized user (Bob) and eavesdropper (Eve) is used to assess the secrecy performance in this paper. So we calculate the BER of our proposed scheme through theoretical analysis and simulations. The results suggest that the modified RB-HARQ protocol can strongly enhance the reliability and security of our system, with the maximum retransmission number at a low level.
This paper presents a secure communication scheme based on a modified Reliability-Based Hybrid Automatic Repeat reQuest (RB-HARQ) protocol over the additive white Gaussian noise (AWGN) wiretap channel. RB-HARQ protocol is firstly implemented in the secure communication system and showed a significant enhancement of the physical layer security. The retransmission encoding scheme is the main difference between traditional RB-HARQ and modified RB-HARQ, which can encode the unreliable bits of the authorized user (Bob) and retransmit the encoded unreliable bits through the AWGN wiretap channel. With the retransmission encoding scheme, the maximum retransmission number of RB-HARQ protocol can be largely reduced and secure communication can still be ensured, which is much more practical in long distance communication system. Bit error rate (BER) at both the authorized user (Bob) and eavesdropper (Eve) is used to assess the secrecy performance in this paper. So we calculate the BER of our proposed scheme through theoretical analysis and simulations. The results suggest that the modified RB-HARQ protocol can strongly enhance the reliability and security of our system, with the maximum retransmission number at a low level.
In this paper, we proposed a secure communication scheme based on Reliability-Based Hybrid Automatic Repeat reQuest (RB-HARQ) protocol over the additive white Gaussian noise (AWGN) wiretap channel. RB-HARQ protocol aims at retransmitting the unreliable bits required for the authorized user's (Bob) successfully decoding and minimizing the information leakage that may benefit to eavesdropper (Eve). The secrecy level in this paper is assessed through the bit error rate (BER) at both the authorized user (Bob) and eavesdropper (Eve). Therefore, we analyze the BER of our proposed scheme through theoretical arguments and simulations. Numerical results suggest that RB-HARQ protocol can significantly enhance the security performance of our communication system.
In physical layer secure communication system,the existing retransmission technology retransmits the whole wrong message when the legitimate user is in error,which may lead to the eavesdropper receives a lot of useful information.Aiming at solving the above problems,the Reliability-based Hybrid Automatic Repeat Request (RB-HARQ) protocol is introduced in,and a secure communication technology is proposed.RB-HARQ protocol can just retransmit the unreliable bits required by the legitimate user and minimizing the information leak to eavesdropper,thus secure and reliable communication can be achieved.Simulation results show that,compared with the traditional HARQ protocol,RB-HARQ protocol can enhance the physical layer security performance of the communication system.
Consider a wireless transmission from Alice to Bob in the presence of an eavesdropper, Eve. We propose a technique to allow Alice to send a message such that Bob can decode it but Eve can get little information about the message. This scenario is a classic example of the wiretap channel, for which several researchers have begun to develop practical schemes. However, we consider a challenging version in which the channel from Alice to Eve may be as good or better than the channel from Alice to Bob. There have been no practical secrecy coding techniques that have been developed for this scenario. The key to allow secret communication in such a scenario is feedback from Bob to Alice (which Eve can also observe). The scheme we develop uses reliability-based hybrid automatic-repeat-request (RB-HARQ) over a fast fading channel to provide a decoding advantage at Bob. Bob requests information about received symbols that suffer from deep fades. The retransmitted symbols improve Bobpsilas ability to decode the message faster than at Eve, who sees retransmission of bits with random reliabilities. We evaluate the proposed scheme by performance measures such as the probability of successful decoding and the equivocation rate at Eve.
The focus of this paper is an information-theoretic study of retransmission protocols for reliable packet communication under a secrecy constraint. Thehybridautomaticretransmission request (HARQ) protocol is revisited for a block-fading wiretap channel. Here, two legitimate users communicate over a block-fading channel in the presence of a passive eavesdropper who intercepts the transmissions through an independent block-fading channel. In this model, the transmitter obtains a 1-bit ACK/NACK feedback from the legitimate receiver via an error-freepublicchannel. Both reliability and confidentiality of secure HARQ protocols are studied through the joint consideration of channel coding, secrecy coding, and retransmission protocols. In particular, the error and secrecy performance ofrepetition time diversity(RTD) andincremental redundancy(INR) protocols are investigated based on Wyner code sequences. These protocols ensure that the confidential message is decoded successfully by the legitimate receiver and is kept completely secret from the eavesdropper for a set of channel realizations. This paper illustrates that there exists a rate-compatible Wyner code family which ensures a secure INR protocol. Further, it defines theconnection outageandsecrecy outageprobabilities to characterize the tradeoff between the reliability of the legitimate communication link and the confidentiality with respect to the eavesdropper's link. For a given connection/secrecy outage probability pair, an achievable throughput of secure HARQ protocols is derived for block-fading channels. Finally, both asymptotic analysis and numerical calculations demonstrate the benefits of HARQ protocols to throughput and secrecy.
Wireless systems are susceptible to eavesdropping as an unwelcome result of the broadcast nature of the wireless medium. Fortunately, the wireless medium also provides endowments including the temporal dispersion, the capability of signal superposition and other properties, to facilitate defending against eavesdropping. The focus of the thesis is to provide schemes for utilizing these properties at the physical layer and their performance analysis from an information-theoretic secrecy perspective. The work is based on Wyner's results on the wire-tap channel, in which the transmission between two legitimate users (Alice and Bob) is eavesdropped upon by Eve. The secrecy level is measured by the equivocation rate at Eve. The system performance is measured by the secrecy capacity. This is the maximum rate at which a message can be sent from Alice to Bob, while constraining the equivocation rate at Eve equal to the communication rate, and thus ensuring that Eve cannot deduce any useful information asymptotically. First, the scenario where a secret message needs to be delivered to the intended receiver within a given delay constraint and without the knowledge of the channel state information (CSI) at the transmitter is considered. In particular, hybrid automatic retransmission request (HARQ) protocols are revisited for a block-fading wire-tap channel via a joint consideration of channel coding, secrecy coding, and retransmission protocols. Two secure HARQ protocols: a repetition time diversity (RTD) scheme with maximal-ratio combining, and an incremental redundancy (INR) scheme based on ratecompatible Wyner secrecy codes are analyzed via an outage-based formulation. The throughput of RTD and INR protocols under probabilistic outage requirements is derived. Asymptotic analysis and numerical computations are given to demonstrate both the benefits of HARQ protocols and the tradeoff between reliability and confidentiality in delay-constrained communications. Second, the effects of interference on information-theoretic secret communication is considered. More specifically, the wiretap channel with a helping interferer (WT-HI) is proposed and studied. Here, an interferer, which does not know the confidential message, helps in ensuring the secrecy of the message by sending independent signals. Achievable secrecy rates and upper bounds on the secrecy capacity are given for both discrete memoryless and Gaussian channels. Interference has conventionally been regarded as a harmful phenomenon that leads to decreasing the rate and the reliability performance of wireless systems. In this work, it is shown that interference can be exploited to assist wireless secrecy. Lastly, the problem of secret key generation over fading channels, in which there exists an additional authenticated, public and error-free feedback channel from Bob to Alice, is considered. A key generation scheme consisting of a communication phase and a key-generation phase is presented. The communication phase is based on layered broadcast coding, which adapts the decoded rate at Bob to the actual channel state without requiring CSI available at Alice. The key-generation phase is based on the messages decoded by Bob after the communication phase and the public feedback. The achievable secrecy key rate and the optimal power distribution over coded layers for maximizing the secrecy key rate are characterized. Theoretical and numerical results show that the broadcast approach outperforms the single-level-coding based approach significantly, and hence demonstrate the role of introducing self-interference in facilitating secret-key generation over slowly fading channels when transmit CSI is not available.
In applications of wireless packet-oriented data networks, a special coding scheme, the hybrid automatic retransmission request (HARQ) exhibits high throughput efficiency by adapting its error correcting code redundancy to channel conditions. Motivated by the increasing importance of secure communication over wireless networks, we investigate secure packet communication based on HARQ over block-fading (BF) channels. More specifically, we consider two legitimate users communicating over a BF channel in the presence of a passive eavesdropper who intercepts the transmission through another independent BF channel. We assume that the transmitter can obtain a 1-bit ACK/NACK feedback from the receiver via a reliable public channel. Under this setting, we consider incremental redundancy (IR) and repetition time diversity (RTD) HARQ schemes based on rate-compatible Wyner secrecy codes from an information theoretic point of view. We study a good Wyner code sequence, with which the legitimate receiver can decode the message and the eavesdropper can be perfectly confused. For a given pair of reliability/secrecy outage probabilities, we derive an achievable secrecy throughput of HARQ protocols for block-fading channels. Finally, we illustrate numerically that HARQ can benefit both throughput and secrecy.