In this paper, we provide a comprehensive study of secrecy transmission in decode-and-forward (DF) relay networks subjected to slow fading. With only channel distribution information (CDI) of the wiretap channels, we aim at maximizing secrecy throughput of the two-hop transmission under a secrecy outage constraint through optimizing transmission region, rate parameters of the wiretap codes and power allocation between the source and relay. We propose fixed transmission parameter scheme (FTPS) and variable transmission parameter scheme (VTPS), which are based on the CDI and instantaneous channel state information of the main channels, respectively. In both schemes, source and relay use the same codeword, and the eavesdropper can use maximum ratio combining (MRC) reception. To improve the secrecy throughput, we further propose VTPS-D1 and VTPS-D2 schemes, where the source and relay either use independent codewords with identical code rates, or different codebooks with different code rates so that the eavesdropper can only decode the two-hop signals individually rather than using MRC. We provide explicit results on the design for all proposed schemes. Numerical results and comparisons on the secrecy throughput of these schemes are presented to reveal their respective superiorities and give some insights into the choice of design scheme.
In this paper, we provide a comprehensive study of secrecy transmission in decode-and-forward (DF) relay networks subjected to slow fading. With only channel distribution information (CDI) of the wiretap channels, we aim at maximizing secrecy throughput of the two-hop transmission under a secrecy outage constraint through optimizing transmission region, rate parameters of the wiretap codes and power allocation between the source and relay. We propose fixed transmission parameter scheme (FTPS) and variable transmission parameter scheme (VTPS), which are based on the CDI and instantaneous channel state information of the main channels, respectively. In both schemes, source and relay use the same codeword, and the eavesdropper can use maximum ratio combining (MRC) reception. To improve the secrecy throughput, we further propose VTPS-D1 and VTPS-D2 schemes, where the source and relay either use independent codewords with identical code rates, or different codebooks with different code rates so that the eavesdropper can only decode the two-hop signals individually rather than using MRC. We provide explicit results on the design for all proposed schemes. Numerical results and comparisons on the secrecy throughput of these schemes are presented to reveal their respective superiorities and give some insights into the choice of design scheme.
This paper comprehensively studies the secure decode-and-forward (DF) relaying transmission in slow fading channels. To maximize the secrecy throughput under a secrecy outage probability constraint, we propose three adaptive transmission schemes (ATSs) with different complexity and flexibility, and design system parameters according to the instantaneous channel state information of the legitimate receiver. Specifically, in ATS-SW, source and relay use the same codeword, and eavesdropper employs the maximal ratio combining (MRC) reception; whereas in ATS-DWSR and ATS-DBDR, the source and relay either use independent codewords with identical code rates, or different codebooks with different code rates so that the eavesdropper can only decode the two-hop signals individually instead of MRC method. For all the three ATSs, we provide explicit solutions on the optimal system parameters, including the resource allocation between the source and relay, and the code rates. We also present numerical results and comparisons on the secrecy throughput of these schemes.
In this paper, a source communicates to the destination with the cooperation of a relay, in the presence of an eavesdropper. All the links undergo Rayleigh fading and perfect decoding at the relays is not considered. The secrecy outage probability expression is evaluated for a decode-and-forward (DF) dual-hop cooperative relay network, both with and without the presence of direct source to eavesdropper transmission link. The performance of the maximal ratio combining (MRC) and selection combining (SC) diversity at the eavesdropper is investigated. Asymptotic and diversity gain analysis for both the single relay and multi-relay system is obtained, when average SNRs of source-relay and relay-destination links are balanced or unbalanced. We have shown that the increase in target secrecy rate and eavesdropper channel quality significantly affects the outage performance of the system. We have investigated the outage probability of optimal relay selection scheme, when either full instantaneous channel state information (ICSI) or statistical channel state information (SCSI) of all the links is available and have shown that there is improvement in the secrecy performance with the increase in the number of relays.
We propose a secure transmission scheme for a relay wiretap channel, where a source communicates with a destination via a decode-and- forward relay in the presence of spatially random- distributed eavesdroppers. We assume that the source is equipped with multiple antennas, whereas the relay, the destination, and the eavesdroppers are equipped with a single antenna each. In the proposed scheme, in addition to information signals, the source transmits artificial noise signals in order to confuse the eavesdroppers. With the target of maximizing the secrecy throughput of the relay wiretap channel, we derive a closed-form expression for the transmission outage probability and an easy-to-compute expression for the secrecy outage probability. Using these expressions, we determine the optimal power allocation factor and wiretap code rates that guarantee the maximum secrecy throughput, while satisfying a secrecy outage probability constraint. Furthermore, we examine the impact of source antenna number on the secrecy throughput, showing that adding extra transmit antennas at the source brings about a significant increase in the secrecy throughput.
This paper addresses the physical layer security of a two-hop decode-and-forward (DF) wireless relay network in the presence of several eavesdroppers. The wiretap channel model consists of a source, several eavesdroppers, couples of trusted relays and a destination. For this DF based cooperative relay scheme, the relays use different code words independent of the source code words to transmit a weighted version of the recoded messages as with the source messages to the legitimate receiver and jam the eavesdropper. We fix the transmit power of the source ( Ps ) to obtain the weights for secrecy rate maximization, assuming that global channel state information (CSI) is available. The maximization problem can be made to a generalized eigenvector problem, and it is easy to obtain the corresponding eigenvector that is the optimal relay weight vector by using the matrix computations. The closed-form optimal solution is derived for the relay weights that maximize the achievable secrecy rate.
In this paper, we consider secure communications of one source-destination pair in wireless multi-hop decode-and-forward (DF) relay networks. In the presence of an eavesdropper, we derive an optimal power allocation strategy to maximize achievable secrecy rates under an overall transmit power constraint assuming that a single relay is located at each individual hop. We demonstrate that the optimal power allocation is obtained when the overall power constraint and the DF-relaying constraints necessary to guarantee that each DF relay correctly decodes the information signals hold with equality, which rely on channel conditions between the source, relays, and destination. The channel conditions for the eavesdropper are shown to only influence relays that may be inactive for secrecy rate maximization. We also consider multiple cooperative relays at each hop to perform cooperative beamforming in the presence of multiple eavesdroppers. To improve the secrecy rate in multi-hop relay networks, which include more than two hops, we propose an iterative cooperative beamformer design and transmit power allocation scheme with relay selection. Numerical results are presented to investigate the secrecy capacity obtained by the optimal power allocation in multi-hop DF relay networks and to confirm the secrecy rate enhancement of the proposed cooperative beamforming scheme.
In this paper, we investigate the secrecy outage performance of decode-and-forward (DF) buffer-aided relaying networks with a multi-antenna destination in the presence of an eavesdropper. In order to take full advantage of the benefits provided by the multiple antennas at the destination and the available relays, we adopt the max-link relay selection scheme and propose a half-duplex and two full-duplex secure transmission schemes for secrecy improvement, i.e., 1) maximal-ratio combining (MRC), 2) maximal-ratio combining/cooperative jamming (MRC/CJ), and 3) zero-forcing beamforming/cooperative jamming (ZFB/CJ). For all proposed schemes, we present exact and asymptotic closed-form expressions of the secrecy outage probability by modeling the dynamic buffer state transitions as a Markov chain. Moreover, simple and informative asymptotic results are provided under both L → ∞ and L → ∞ scenarios (where L denotes the buffer size), from which we can obtain further insights on the secrecy diversity gain and the secrecy coding gain. The highlights of this paper can be summarized as follows: 1) Under L → ∞ scenario, the secrecy diversity gains of all proposed schemes both reach M. When L → ∞, the secrecy diversity gains of MRC, MRC/CJ and ZFB/CJ increase to M (1 + ND), MND and 2M respectively, where M is the number of relays and ND represents the number of antennas at the destination; 2) The secrecy coding gain of the system differs with different schemes, and it improves with the increase of M and ND under both the two scenarios; and 3) Under the scenario L → ∞, ZFB/CJ outperforms MRC and MRC/CJ across the entire signal-to-noise ratio (SNR) range of interest, however, when L→ ∞, ZFB/CJ outperforms MRC/CJ and MRC in the low SNR regime, while the opposite holds in the high SNR regime.