We consider the problem of K-user interference channel with confidential messages (IC-CM) with intersymbol interference (ISI). The main contribution of this paper is to show that sum-secure degrees of freedom (SDoF) can be made to linearly increase with the number of users K in the absence of channel state information at the transmitters (CSIT). The proposed scheme entails three main ingredients : a) leveraging the simple channel matrix structures resulting from the orthogonal frequency division multiplexing (OFDM) type transmission technique in order to eliminate interference and allow coherent decoding of each message at its respectively intended receiver. b) exploiting the inherent heterogeneity in channel impulse response (CIR) lengths between the transmitters and the receivers (which results from the wireless multipath propagation), and c) injection of artificial noise into the transmitted signal from a strategically chosen small number of transmitters J that act as cooperative jammers in order to preserve full confidentiality of the messages at the unintended receivers. This is the first work showing that the SDoF of the K-user IC-CM with ISI can linearly increase with the number of users without CSIT.
We consider the problem of K-user interference channel with confidential messages (IC-CM) with intersymbol interference (ISI). The main contribution of this paper is to show that sum-secure degrees of freedom (SDoF) can be made to linearly increase with the number of users K in the absence of channel state information at the transmitters (CSIT). The proposed scheme entails three main ingredients : a) leveraging the simple channel matrix structures resulting from the orthogonal frequency division multiplexing (OFDM) type transmission technique in order to eliminate interference and allow coherent decoding of each message at its respectively intended receiver. b) exploiting the inherent heterogeneity in channel impulse response (CIR) lengths between the transmitters and the receivers (which results from the wireless multipath propagation), and c) injection of artificial noise into the transmitted signal from a strategically chosen small number of transmitters J that act as cooperative jammers in order to preserve full confidentiality of the messages at the unintended receivers. This is the first work showing that the SDoF of the K-user IC-CM with ISI can linearly increase with the number of users without CSIT.
We consider the K-user interference channel with confidential messages (IC-CM) with intersymbol interference (ISI). The main contribution of this paper is to show that sum-secure degrees of freedom (SDoF) can be made to linearly increase with the number of users K with no channel state information at the transmitters (CSIT). We demonstrate that this is true whenever the channel impulse response (CIR) lengths from the legitimate transmitters towards their respectively intended receivers are larger than those from the interfering transmitters towards the unintended receivers. To design this scheme, we use: a) the simple channel matrix structures of the received signal space to eliminate interference and allow decodability at the intended receivers. b) an injection of artificial noise into the transmitted signal from a strategically chosen small number of transmitters that act as cooperative jammers in order to preserve confidentiality of messages at unintended receivers. This is the first work showing that the SDoF of the K-user IC-CM with ISI can linearly increase with K, the number of users.
We investigate the secure degrees of freedom (SDoF) of the multiple-input multiple-output (MIMO) wiretap channel with intersymbol interference (ISI) in the presence of a multi-antenna cooperative jammer. We focus on the practically relevant setting with no channel state information at the transmitters (CSIT). More specifically, the legitimate transmitter and the cooperative jammer only have statistical knowledge of the channel in terms of the effective number of ISI channel taps, i.e., channel impulse response (CIR) lengths, toward the legitimate receiver and the eavesdropper. Our main contribution is to show that in the absence of CSIT, positive SDoF can be achieved by carefully exploiting: 1) the heterogeneity of the CIR lengths toward both receivers and 2) the relative number of antennas at the four terminals. To achieve secrecy, we propose a scheme in which the transmitter strategically sends a mixture of information and artificial noise symbols in a way that exploits the heterogeneity of CIR lengths. Additionally, the cooperative jammer transmits artificial noise symbols in a way that completely masks all the information symbols that are received at the eavesdropping node. Under the proposed scheme, positive SDoF can be achieved, even when the number of antennas at the legitimate receiver is less than the number of antennas at the eavesdropper.
In this paper, the K-user interference channel with confidential messages is considered with delayed channel state information at transmitters (CSIT). We propose a novel secure transmission scheme in which the transmitters carefully mix information symbols with artificial noises to ensure confidentiality. Achieving confidentiality is challenging due to the delayed nature of CSIT, and the distributed nature of the transmitters. Our scheme works over two phases: phase one in which each transmitter sends information symbols mixed with artificial noises, and repeats such transmission over multiple rounds. In the next phase, each transmitter uses delayed CSIT of the previous phase and sends a function of the net interference and artificial noises (generated in previous phase), which is simultaneously useful for all receivers. These phases are designed to ensure the decodability of the desired messages while satisfying the confidentiality constraints. The proposed scheme achieves a sum secure degrees of freedom (SDoF) of at least [1/2](√K-6). To the best of our knowledge, this is the first result on the K-user interference channel with confidential messages and delayed CSIT that achieves a SDoF which scales with K -.
In this paper, the K-user interference channel with secrecy constraints is considered with delayed channel state information at transmitters (CSIT). We propose a novel secure retrospective interference alignment scheme in which the transmitters carefully mix information symbols with artificial noises to ensure confidentiality. Achieving positive secure degrees of freedom (SDoF) is challenging due to the delayed nature of CSIT, and the distributed nature of the transmitters. Our scheme works over two phases: Phase one, in which each transmitter sends information symbols mixed with artificial noises, and repeats such transmission over multiple rounds. In the next phase, each transmitter uses the delayed CSIT of the previous phase and sends a function of the net interference and artificial noises (generated in previous phase), which is simultaneously useful for all receivers. These phases are designed to ensure the decodability of the desired messages while satisfying the secrecy constraints. We present our achievable scheme for three models, namely: (1) K-user interference channel with confidential messages (IC-CM), and we show that 1 2 ( K − 6 ) SDoF is achievable; (2) K-user interference channel with an external eavesdropper (IC-EE); and (3) K-user IC with confidential messages and an external eavesdropper (IC-CM-EE). We show that for the K-user IC-EE, 1 2 ( K − 3 ) SDoF is achievable, and for the K-user IC-CM-EE, 1 2 ( K − 6 ) is achievable. To the best of our knowledge, this is the first result on the K-user interference channel with secrecy constrained models and delayed CSIT that achieves an SDoF which scales with K , square-root of number of users.
In this paper, the sum secure degrees of freedom (SDoF) of the K-user Multiple Input/Single Output (MISO) Broadcast Channel with Confidential Messages (BCCM) and alternating Channel State Information at the Transmitter (CSIT) is investigated. In the MISO BCCM, a K-antenna transmitter (TX) communicates toward K single-antenna receivers (RXs), so that message for RX k is kept secret from RX j with jsum= (2K − 1)/2. Interestingly, this SDoFsumis attained by a rather simple achievability in which the TX uses artificial noise to prevent the decoding of the message of the unintended receivers at RX 1. The proof for the case K = 3 is discussed in detail.
We investigate secure degrees of freedom (SDoF) of a single-input single-output (SISO) wiretap channel with a single helper without channel state information at the transmitters (CSIT). Wireless communication systems inherently suffer from intersymbol interference (ISI) due to channel dispersion. In this paper, we propose a novel blind cooperative jamming scheme that exploits the ISI heterogeneity to achieve positive SDoF, even without any CSIT. In order to achieve positive SDoF, the proposed approach only requires statistical properties of the ISI channel. In particular, we show that if LB is the effective ISI channel multipath link length towards the legitimate receiver (Bob) and LE is the link length towards the eavesdropper (Eve), a positive SDoF of LB-LE is achievable. To the best of our 2(LB -1) knowledge, this is the first work that exploits ISI link length heterogeneity to achieve positive secure degrees of freedom.