Capacity of Cognitive Interference Channels With and Without Secrecy

Like the conventional two-user interference channel, the cognitive interference channel consists of two transmitters whose signals interfere at two receivers. It is assumed that there is a common message (message 1) known to both transmitters, and an additional independent message (message 2) known only to the cognitive transmitter (transmitter 2). The cognitive receiver (receiver 2) needs to decode messages 1 and 2, while the noncognitive receiver (receiver 1) should decode only message 1. Furthermore, message 2 is assumed to be a confidential message which needs to be kept as secret as possible from receiver 1, which is viewed as an eavesdropper with regard to message 2. The level of secrecy is measured by the equivocation rate. In this paper, a single-letter expression for the capacity-equivocation region of the discrete memoryless cognitive interference channel is obtained. The capacity-equivocation region for the Gaussian cognitive interference channel is also obtained explicitly. Moreover, particularizing the capacity-equivocation region to the case without a secrecy constraint, the capacity region for the two-user cognitive interference channel is obtained, by providing a converse theorem.      

Secure Communication Over Fading Channels

The fading broadcast channel with confidential messages (BCC) is investigated, where a source node has common information for two receivers (receivers 1 and 2), and has confidential information intended only for receiver 1. The confidential information needs to be kept as secret as possible from receiver 2. The broadcast channel from the source node to receivers 1 and 2 is corrupted by multiplicative fading gain coefficients in addition to additive Gaussian noise terms. The channel state information (CSI) is assumed to be known at both the transmitter and the receivers. The parallel BCC with independent subchannels is first studied, which serves as an information-theoretic model for the fading BCC. The secrecy capacity region of the parallel BCC is established, which gives the secrecy capacity region of the parallel BCC with degraded subchannels. The secrecy capacity region is then established for the parallel Gaussian BCC, and the optimal source power allocations that achieve the boundary of the secrecy capacity region are derived. In particular, the secrecy capacity region is established for the basic Gaussian BCC. The secrecy capacity results are then applied to study the fading BCC. The ergodic performance is first studied. The ergodic secrecy capacity region and the optimal power allocations that achieve the boundary of this region are derived. The outage performance is then studied, where a long-term power constraint is assumed. The power allocation is derived that minimizes the outage probability where either the target rate of the common message or the target rate of the confidential message is not achieved. The power allocation is also derived that minimizes the outage probability where the target rate of the confidential message is not achieved subject to the constraint that the target rate of the common message must be achieved for all channel states.     

On the Secrecy Capacity of Fading Channels

We consider the secure transmission of information over an ergodic fading channel in the presence of an eavesdropper. Our eavesdropper can be viewed as the wireless counterpart of Wyner's wiretapper. The secrecy capacity of such a system is characterized under the assumption of asymptotically long coherence intervals. We first consider the full channel state information (CSI) case, where the transmitter has access to the channel gains of the legitimate receiver and the eavesdropper. The secrecy capacity under this full CSI assumption serves as an upper bound for the secrecy capacity when only the CSI of the legitimate receiver is known at the transmitter, which is characterized next. In each scenario, the perfect secrecy capacity is obtained along with the optimal power and rate allocation strategies. We then propose a low-complexity on/off power allocation strategy that achieves near-optimal performance with only the main channel CSI. More specifically, this scheme is shown to be asymptotically optimal as the average signal-to-noise ratio (SNR) goes to infinity, and interestingly, is shown to attain the secrecy capacity under the full CSI assumption. Overall, channel fading has a positive impact on the secrecy capacity and rate adaptation, based on the main channel CSI, is critical in facilitating secure communications over slow fading channels.      

Nakagami信道下MIMO解码转发中继系统的安全性能分析

在协同自适应解码转发中继系统中,该文针对Nakagami-m衰落信道,研究了基于多天线低复杂度的机会式传输策略的物理层安全性能。为充分利用天线分集增益提升系统安全性能,发送节点均采用发送天线选择策略,接收节点均采用最大比合并策略。推导了系统安全中断概率的闭合表达式,并进一步提供了渐近性能分析,得到了系统的安全分集阶数。仿真结果验证了理论分析的正确性,并揭示了各系统参数对机会式传输方案的安全性能的影响。结果表明,通过增加合法节点的天线数和增大合法信道的Nakagami衰落信道参数可显著提升系统安全性能。     

Discrete Memoryless Interference and Broadcast Channels With Confidential Messages: Secrecy Rate Regions

We study information-theoretic security for discrete memoryless interference and broadcast channels with independent confidential messages sent to two receivers. Confidential messages are transmitted to their respective receivers while ensuring mutual information-theoretic secrecy. That is, each receiver is kept in total ignorance with respect to the message intended for the other receiver. The secrecy level is measured by the equivocation rate at the eavesdropping receiver. In this paper, we present inner and outer bounds on secrecy capacity regions for these two communication systems. The derived outer bounds have an identical mutual information expression that applies to both channel models. The difference is in the input distributions over which the expression is optimized. The inner bound rate regions are achieved by random binning techniques. For the broadcast channel, a double-binning coding scheme allows for both joint encoding and preserving of confidentiality. Furthermore, we show that, for a special case of the interference channel, referred to as the switch channel, derived bounds meet. Finally, we describe several transmission schemes for Gaussian interference channels and derive their achievable rate regions while ensuring mutual information-theoretic secrecy. An encoding scheme in which transmitters dedicate some of their power to create artificial noise is proposed and shown to outperform both time-sharing and simple multiplexed transmission of the confidential messages.     

Capacity Bounds for Broadcast Channels With Confidential Messages

This paper studies capacity bounds for discrete memoryless broadcast channels with confidential messages. Two private messages as well as a common message are transmitted; the common message is to be decoded by both receivers, while each private message is only for its intended receiver. In addition, each private message is to be kept secret from the unintended receiver where secrecy is measured by equivocation. Both inner and outer bounds are proposed to the rate equivocation region for broadcast channels with confidential messages. The proposed inner bound generalizes Csiszar and Korner's rate equivocation region for broadcast channels with a single confidential message, Liu 's achievable rate region for broadcast channels with perfect secrecy, Marton's and Gel'fand-Pinsker's achievable rate region for general broadcast channels. The proposed outer bounds, together with the inner bound, help establish the rate equivocation region of several classes of discrete memoryless broadcast channels with confidential messages, including the less noisy, deterministic, and semideterministic broadcast channels. Furthermore, specializing to the general broadcast channel by removing the confidentiality constraint, the proposed outer bounds reduce to new capacity outer bounds for the discrete memory broadcast channel.     

Secrecy Trade-off at the Physical Layer over Mixed Fading Multicast Channels Employing Antenna Diversity

This paper deals with the secrecy performance analysis of a multicast network over mixed fading scenarios in which a cluster of passive eavesdroppers is trying to overhear the secret transmission. Our key contribution is to prevent this malicious attack of the illegitimate receivers. Rayleigh/ Rician mixed fading channels are considered to model alternately the multicast/ eavesdropper and eavesdropper/ multicast channels as such mixed fading scenarios are often encountered in cellular communication where only one link (either multicast or eavesdropper) undergo a line-of-sight propagation path. At first, we derive the probability density functions for the single-input-multiple-output multicast scenarios and then the secrecy analysis is carried out by obtaining closed-form expressions for the performance matrices such as the probability of non-zero secrecy multicast capacity, ergodic secrecy multicast capacity, and secure outage probability for multicasting. The derived expressions are beneficial to investigate how the antenna diversity can combat the detrimental impact of fading as well as the number of multicast users and eavesdroppers, and improve the secrecy level to the acceptable limit. Moreover, the best secure scenario in terms of the secrecy parameters is obtained when the multicast channels undergo Rician fading whereas the eavesdropper channels experience Rayleigh fading. Finally, the analytical expressions are justified via the Monte-Carlo simulations.

     

面向物理层安全的广义随机空间调制技术

针对窃听信道质量优于合法信道质量时的物理层安全传输问题,提出了一种广义随机空间调制技术。该技术利用合法信道的瞬时状态信息随机扰乱比特到符号的映射关系,实现物理层安全传输。首先给出了广义随机空间调制系统的收发机结构。然后计算了合法接收用户的误码率上界和系统保密容量。从误码率上界的表达式得出,所提广义随机空间调制系统可靠性与传统广义空间调制相同,由此可在不损失系统可靠性的前提下实现安全传输。保密容量的计算表明,安全通信速率不随窃听方天线增多而下降,因此能抵抗具备海量天线的窃听者。最后用仿真验证理论分析的准确性和所提方案的有效性。     

概率译码转发中继系统中的安全极化编码方法

该文针对中继节点依概率辅助译码转发的通信场景,提出一种中继辅助的安全极化编码方法,保证私密信息可靠传输的同时,达到提高安全传输速率的目的。首先,发送端分别进行两层极化编码——中继概率转发行为构成的虚拟二进制删除信道下的极化编码和实际传输信道下的极化编码,并将私密信息分别隐藏在两层码字中,分时隙广播出去。然后,中继依概率译码后提取出合法用户无法直接接收的固定信息再次进行安全极化编码并转发。最后,接收端利用收到的中继转发码字和发端码字依次分层进行译码。理论和仿真分析证明,所提方法下合法用户能够可靠接收私密信息,而窃听者无法获取任何私密信息信息量;安全传输速率随着码长和中继转发概率的增加而增大,且高于一般的安全极化编码方法。     

Distributed QoS Based Robust Transmission Design for MISO Wiretap Channel with Cooperative Jamming

A communication network that consists of a transmitter, a legitimate receiver, an eavesdropper and several friendly helpers is considered. Both the transmitter and the helpers are equipped with multiple antennas while the legitimate receiver or the eavesdropper has one antenna. The transmitter and the helpers have the channel state information to the legitimate receiver. The channels to the eavesdropper are partially known and modeled with uncertainty ellipsoids. The transmitter applies maximum ratio transmission to the legitimate receiver. The helpers generate interference to degrade the receiving performance of the eavesdropper. The transmit power of the helpers is optimized with the worst-case secrecy rate requirement as the Quality of Service constraint. Based on robust convex optimization, a centralized optimization problem is developed for the helpers to generate interference efficiently with minimum total transmit power. A distributed algorithm is developed which scales well with a large number of helpers.     

MISO窃听信道下有限反馈波束成形算法的保密速率分析(英文)

The secrecy rate of limited feedback beamforming is studied for a Multiple-Input Single-Output(MISO) wiretap channel with a multi-antenna eavesdropper.We first obtain the secrecy rate of limited feedback beamforming achieved at the legitimate receiver.We then derive a lower bound for the asymptotic secrecy rate in the large system limit.From this bound,we observe a threshold for the ratio of eavesdrop antennas to transmit antennas to obtain a positive secrecy rate.We further show that the secrecy rate loss due to limited feedback decays with the number of feedback bits per transmit antenna.     

A physical layer security scheme for full-duplex communication systems with residual self-interference and non-eavesdropping CSI

We discuss the physical layer security scheme in the Full-Duplex (FD) MIMO point-to-point two-way communication system with residual self-interference, in which legitimate nodes send confidential information and null space Artificial Noise (AN) while receiving information. Because the Channel State Information (CSI) of the eavesdropper is unavailable, we optimize the covariance matrices of the information signal as well as the allocation of the antenna for transmitting and receiving to minimize the signal power consumption under the target rate constraint. As a result, the power of AN is maximized within the limit of total power, so the interception capability of the eavesdropper is suppressed as much as possible. Since self-interference cannot be completely eliminated, the optimization process of one legitimate node depends on the optimization result of the other. By substituting self-interference power in the secrecy rate formula with its average value, the joint optimization process at the two nodes is transformed into two separate and solvable optimization processes. Then, the Water-Filling Algorithm (WFA) and bisection algorithm are used to get the optimal covariance matrices of the signal. Furthermore, we derive the theoretical lower bound of ergodic achievable secrecy rate under rayleigh channels to evaluate the performance of the scheme. The simulation results show that the theoretical derivation is correct, and the actual achievable rate is very close to the target rate, which means that the approximation in the optimization is feasible. The results also show that secrecy transmission can be realized because a considerable secrecy rate can be achieved.     

过时信道状态信息下的机会式中继选择系统的安全性能分析

在 Nakagami m衰落信道下,目的端和窃听者采用最大比合并策略,本文研究了在机会式自适应解码转发中继选择安全协作系统中的安全性能。由于实际信道中的反馈延迟,最优的合法中继选择基于合法信道反馈的过时信道状态信息。为了评价机会式中继选择在改善安全性能上的表现,分别推导了准确的正安全容量概率和准确的安全中断概率闭合表达式。此外,针对两种不同情况, 推导了形式简单的渐近表达式,并明确给出安全分集阶数和安全阵列增益。理论分析和数值仿真表明,增加中继个数和目的节点的天线数能够改善安全中断概率的性能表现,且在信道状态信息过时的条件下,系统的安全分集阶数与中继数无关。      

Wireless secure enhancement with cooperative jamming

Secrecy capacity of intrinsically secure communication graph (iS-Graph) can be increased by reducing the signal quality of eavesdroppers with adding controlled interferences.The transmission of secret messages over wireless channels in which the legitimate nodes were aided by cooperative jamming was studied,and a secure communication graph with jamming,jS-Graph was proposed.First,the security properties of jS-Graph was characterized.Then,jamming strategies to confuse eavesdroppers were proposed.To tackle the nearby eavesdropper problem,a two-stage cooperative jamming strategy to jam the eavesdroppers near the source or the destination was applied.The results demonstrate that,with the aid of cooperative jamming the secure communication graph can lead to secrecy gains.These results help to clarify how the presence of eavesdroppers and the cooperative jamming can influence secure connectivity in wireless networks.     

大规模MIMO中继系统中多用户物理层安全传输方案

研究大规模多输入多输出中继网络中的多用户物理层安全传输方案.系统模型中假设窃听节点与源节点和中继节点间都有直接链路,窃听节点可以接收到源节点和中继发送的信号.在不能获得窃听者信道状态信息的情况下,大规模MIMO中继采用简单的最大比合并/最大比发射信号处理方案,并配合中继零空间人工噪声和目的端的协作干扰实现多用户的信息安全传输.对保密速率及其在中继天线数无限增长时的渐近值进行了理论分析,并进行仿真.仿真结果显示系统的保密和速率随中继天线数的增长而增长,最终趋于理论渐近上界值.仿真结果也表明即使窃听节点具有多用户间干扰消除能力,并能同时拦截源节点和中继发送的信号,采用本文的方案仍然能获得可观保密速率.     

存在辅助节点的MIMO窃听信道安全性能研究

为了提高MIMO窃听信道的可达安全速率,提出了基于广义奇异值分解的合作干扰策略。该策略中源节点和辅助节点同时采用基于广义奇异值分解的波束形成技术,源节点发送消息信号,辅助节点发送独立于消息信号的噪声信号,噪声信号对目的节点和窃听节点都产生干扰。此外设计了源节点和辅助节点采用合作干扰策略时的联合最优功率分配算法。该算法可以实现源节点和辅助节点在总功率受限时的可达安全速率最大化。仿真结果表明,与现有的非合作最优功率分配算法相比,本文提出的合作干扰策略在大信噪比时可以显著提高系统的可达安全速率。      

一种基于时空编码的物理层安全算法

针对多天线窃听系统的物理层安全问题,提出一种基于时空编码的预编码算法。首先,合法接收者发送训练序列用于发送者估计主信道状态信息,而窃听信道的状态信息合法用户均未知;其次,发送者利用均匀信道分解的方法提取主信道状态信息的特征参数,生成发射端预编码矩阵和合法接收端均衡矩阵,收发联合加密处理提高物理层安全;最后,利用 Monte Carlo方法进行仿真实验,数值分析表明,该算法在窃听者天线数目增多时能够实现非负的保密容量,即使窃听信道质量较好时,窃听者的接收性能仍维持在很差的水平,误码率高达0.5。     

Co op erative Secrecy to Resist Authentication Error in Two-Hop Wireless Networks

The authentication error in two-hop wire-less networks is considered without knowledge of eaves-dropper channels and location. The wireless information-theoretic security has attracted considerable attention re-cently. A prerequisite for available works is the precise distinction between legitimate nodes and eavesdroppers. However it is unrealistic in the wireless environment. Error is always existing in the node authentication process. Best of our knowledge, there are no works focus on solving this problem in the information-theoretic security. This paper presents a eavesdropper model with authentication error and two eavesdropping ways. Then, the number of eaves-droppers can be tolerated is analyzed while the desired secrecy is achieved with high probability in the limit of a large number of relay nodes. Final, we draw two conclu-sions for authentication error: 1) The impersonate nodes are chosen as relay is the dominant factor of the transmit-ted message leakage, and the impersonation attack does seriously decrease the number of eavesdroppers can be tol-erated. 2) The error authentication to legitimate nodes is almost no effect on the number of eavesdroppers can be tolerated.     

Distributed Detection With Censoring Sensors Under Physical Layer Secrecy

We consider distributed binary detection problems in which the remote sensors of a network implement a censoring strategy to fulfill energy constraints, and the network works under the attack of an eavesdropper. The attacker wants to discover the state of the nature scrutinized by the system, but the network implements appropriate countermeasures to make this task hopeless. The goal is to achieve perfect secrecy at the physical layer, making the data available at the eavesdropper useless for its detection task. Adopting as performance metric certain Ali-Silvey distances, we characterize the detection performance of the system under physical layer secrecy. Two communication scenarios are addressed: parallel access channels and a multiple access channel. In both cases the optimal operative points from the network perspective are found. The most economic operative solution is shown to lie in the asymptote of low energy regime. How the perfect secrecy requirement impacts on the achievable performances, with respect to the absence of countermeasures, is also investigated.     

多组多播集中式大规模MIMO系统的安全性能分析

分析了主动攻击下的多组多播集中式大规模多输入多输出(Multiple-Input Multiple-Output,MIMO)系统的安全性能。基于上行导频训练估计的信道状态信息,系统采用功率限制下的共轭波束成形方案实现下行多播传输。通过分析合法用户安全速率的下界和窃听者信息速率的上界,得到了系统安全速率下界的闭合表达式。进一步,推导出基站天线数趋于无穷大情况下此安全传输系统能获取的极限安全速率。实验仿真验证了所得结果的正确性。