We study the physical-layer security of a spectrum-sharing heterogeneous wireless network in the face of an eavesdropper, which is composed of multiple source-destination (SD) pairs, where an eavesdropper intends to wiretap the signal transmitted by the SD pairs. In order to protect the wireless transmission against eavesdropping, we propose a heterogeneous cooperation framework relying on two stages. Specifically, an SD pair is selected to access the shared spectrum using an appropriately designed scheme at the beginning of the first stage. The other source nodes (SNs) transmit their data to the SN of the above-mentioned SD pair through a reliable short-range wireless interface during the first stage. Then, the SN of the chosen SD pair transmits the data packets containing its own messages and the other SNs' messages to its dedicated destination node (DN) in the second stage, which in turn will forward all the other DNs' data to the corresponding DNs via the backhaul. We conceive two specific SD pair selection schemes, termed as space-time coding aided source-destination pair selection (STC-SDPS), and the transmit antenna selection aided source-destination pair selection (TAS-SDPS), respectively. We derive the secrecy outage probability (SOP) expressions for both the STC-SDPS and for the TAS-SDPS schemes. Furthermore, we carry out the secrecy diversity gain analysis in the high main-to-eavesdropper ratio (MER) region, showing that both the STC-SDPS and TAS-SDPS schemes are capable of achieving the maximum attainable secrecy diversity order. Additionally, increasing the number of the heterogeneous transmission pairs will reduce the SOP, whilst increasing the secrecy diversity order of the STC-SDPS and TAS-SDPS schemes.
We study the physical-layer security of a spectrum-sharing heterogeneous wireless network in the face of an eavesdropper, which is composed of multiple source-destination (SD) pairs, where an eavesdropper intends to wiretap the signal transmitted by the SD pairs. In order to protect the wireless transmission against eavesdropping, we propose a heterogeneous cooperation framework relying on two stages. Specifically, an SD pair is selected to access the shared spectrum using an appropriately designed scheme at the beginning of the first stage. The other source nodes (SNs) transmit their data to the SN of the above-mentioned SD pair through a reliable short-range wireless interface during the first stage. Then, the SN of the chosen SD pair transmits the data packets containing its own messages and the other SNs' messages to its dedicated destination node (DN) in the second stage, which in turn will forward all the other DNs' data to the corresponding DNs via the backhaul. We conceive two specific SD pair selection schemes, termed as space-time coding aided source-destination pair selection (STC-SDPS), and the transmit antenna selection aided source-destination pair selection (TAS-SDPS), respectively. We derive the secrecy outage probability (SOP) expressions for both the STC-SDPS and for the TAS-SDPS schemes. Furthermore, we carry out the secrecy diversity gain analysis in the high main-to-eavesdropper ratio (MER) region, showing that both the STC-SDPS and TAS-SDPS schemes are capable of achieving the maximum attainable secrecy diversity order. Additionally, increasing the number of the heterogeneous transmission pairs will reduce the SOP, whilst increasing the secrecy diversity order of the STC-SDPS and TAS-SDPS schemes.
We study the physical-layer security of a multiple source-destination (SD) pairs coexisting wireless network in the face of an eavesdropper, where an eavesdropper intends to wiretap the signal transmitted by the SD pairs. In order to protect the wireless transmission against eavesdropping, we propose a cooperation framework relying on two stages. Specifically, an SD pair is selected to access the total allocated spectrum using an appropriately designed scheme at the beginning of the first stage. The other source nodes (SNs) simultaneously transmit their data to the SN of the above-mentioned SD pair relying on an orthogonal way during the first stage. Then, the SN of the chosen SD pair transmits the data packets containing its own messages and the other SNs' messages to its dedicated destination node (DN) in the second stage, which in turn will forward all the other DNs' data to the application center via the core network. We conceive a specific SD pair selection scheme, termed as the transmit antenna selection aided source-destination pair selection (TAS-SDPS). We derive the secrecy outage probability (SOP) expressions for the TAS-SDPS, as well as for the conventional round-robin source-destination pair selection (RSDPS) and non-cooperative (Non-coop) schemes for comparison purposes. Furthermore, we carry out the secrecy diversity gain analysis in the high main-to-eavesdropper ratio (MER) region, showing that the TAS-SDPS scheme is capable of achieving the maximum attainable secrecy diversity order.
We study the physical-layer security of multiple source-destination (SD) pairs communicating within a wireless network in the face of an eavesdropper attacking the SD pairs. In order to protect the wireless transmission against eavesdropping, we propose a cooperation framework relying on two stages. Specifically, an SD pair is selected to access the total allocated spectrum using an appropriately designed scheme at the beginning of the first stage. The other source nodes (SNs) simultaneously transmit their data to the SN of the above-mentioned SD pair relying on orthogonal resources during the first stage. Then, the SN of the chosen SD pair transmits the data packets containing its own messages and the other SNs' messages to its dedicated destination node (DN) in the second stage. Finally, this dedicated DN will forward all the other DNs' data to the application center via the core network. We conceive a specific SD pair selection scheme, termed as the transmit antenna selection aided source-destination pair selection (TAS-SDPS). We continue by deriving the secrecy outage probability (SOP) expressions of both the TAS-SDPS conceived, as well as of the conventional round-robin source-destination pair selection (RSDPS) and of the conventional non-cooperative (Non-coop) schemes for comparison. Furthermore, we carry out the secrecy diversity gain analysis in the high main-to-eavesdropper ratio (MER) region, showing that the TAS-SDPS scheme is capable of achieving the maximum attainable secrecy diversity order. Additionally, we show that increasing the number of transmitting pairs will reduce the SOP, whilst increasing the secrecy diversity order of the TAS-SDPS scheme. It is demonstrated that the SOP of the TAS-SDPS scheme is better than that of the RSDPS and of the conventional Non-coop schemes. We also demonstrate that the secrecy diversity gain of the proposed TAS-SDPS scheme is M times that of the RSDPS scheme in the high-MER region, where M is the number of the SD pairs.
In this paper, we examine the physical-layer security for a spectrum sharing system consisting of multiple source-destination pairs, which dynamically access their shared spectrum for data transmissions in the presence of an eavesdropper. We propose a source cooperation (SC) aided opportunistic jamming framework for protecting the transmission confidentiality of the spectrum sharing system against eavesdropping. Specifically, when a source node is allowed to access the shared spectrum for data transmissions, another source is opportunistically selected in the spectrum sharing system to transmit an artificial noise for disrupting the eavesdropper without affecting the legitimate transmissions. We present two specific SC aided opportunistic jamming schemes, namely the SC aided random jammer selection (RJS) and optimal jammer selection (OJS), which are referred to as the SC-RJS and SC-OJS, respectively. We also consider the conventional non-cooperation as a baseline. We derive closed-form intercept probability expressions for the non-cooperation, SC-RJS and SC-OJS schemes, based on which their secrecy diversity gains are determined through an asymptotic intercept probability analysis in the high signal-to-noise ratio (SNR) region. It is proved that the conventional non-cooperation exhibits a secrecy diversity of zero, whereas the proposed SC-RJS and SC-OJS achieve a higher secrecy diversity of one. This also surprisingly means that no additional secrecy diversity gain is achieved by the optimal jammer selection compared to the random selection strategy. In addition, numerical results show that the intercept probability performance of the SC-OJS is always better than that of the SC-RJS and non-cooperation, even when the legitimate channel is worse than the eavesdropping channel.
This paper investigates the physical layer secrecy performance for an underlay wiretap spectrum sharing network with optimal relay and antenna selection (ORAS). It jointly selects a transmit antenna at a secondary source, a receive antenna at its destination, and a relay between them to maximize the secrecy rate at the destination under a passive eavesdropping scenario. We derive novel, exact expressions for secrecy outage probability (SOP) and secrecy throughput (ST) in a single integral-form. We also provide their accurate approximations in closed-form. Considering three distinct scenarios depending on whether the main link is stronger than the wiretap link and the nature of the primary interference constraint, we obtain different useful system design insights. Under a proportional interference constraint, secrecy diversity gain is achieved only when the main link is stronger than the wiretap link, otherwise the diversity gain is lost and leads to an SOP floor. Under a fixed interference constraint, the SOP floor is further increased. Through numerical results, we show the impact of different signal combining strategies by the eavesdropper on the SOP and ST. We also illustrate the efficacy of the ORAS scheme as compared to other relay and antenna selection schemes.
Abstract—In this paper, we consider a multiple-input multiple-output (MIMO) system consisting of one source, one destination and one eavesdropper, where each node is equipped with an arbitrary number of antennas. To improve the security of source-destination transmissions, we investigate the antenna selection at the source and propose the optimal antenna selection (OAS) and suboptimal antenna selection (SAS) schemes, depending on whether the source node has the global channel state information (CSI) of both the main link (from source to destination) and wiretap link (from source to eavesdropper). Also, the traditional space-time transmission (STT) is studied as a benchmark. We evaluate the secrecy performance of STT, SAS, and OAS schemes in terms of the probability of zero secrecy capacity. Furthermore, we examine the generalized secrecy diversity of STT, SAS, and OAS schemes through an asymptotic analysis of the probability of zero secrecy capacity, as the ratio between the average gains of the main and wiretap channels tends to infinity. This is different from the conventional secrecy diversity which assumes an infinite signal-to-noise ratio (SNR) received at the destination under the condition that the eavesdropper has a finite received SNR. It is shown that the generalized secrecy diversity orders of STT, SAS, and OAS schemes are the product of the number of antennas at source and destination. Additionally, numerical results show that the proposed OAS scheme strictly outperforms both the STT and SAS schemes in terms of the probability of zero secrecy capacity. Index Terms—MIMO, antenna selection, space-time code, eavesdropping attack, secrecy diversity.
In this paper, we consider a multiple-input-multiple-output (MIMO) system consisting of one source, one destination, and one eavesdropper, where each node is equipped with an arbitrary number of antennas. To improve the security of source-destination transmissions, we investigate the antenna selection at the source and propose the optimal antenna selection (OAS) and suboptimal antenna selection (SAS) schemes, depending on whether the source node has the global channel state information (CSI) of both the main link (from source to destination) and the wiretap link (from source to eavesdropper). Moreover, the traditional space-time transmission (STT) is studied as a benchmark. We evaluate the secrecy performance of STT, SAS, and OAS schemes in terms of the probability of zero secrecy capacity. Furthermore, we examine the generalized secrecy diversity of the STT, SAS, and OAS schemes through an asymptotic analysis of the probability of zero secrecy capacity as the ratio between the average gains of the main and wiretap channels tends to infinity. This is different from the conventional secrecy diversity that assumes an infinite signal-to-noise ratio (SNR) received at the destination under the condition that the eavesdropper has a finite received SNR. It is shown that the generalized secrecy diversity orders of the STT, SAS, and OAS schemes are the product of the number of antennas at source and destination. Additionally, numerical results show that the proposed OAS scheme strictly outperforms both the STT and the SAS schemes in terms of the probability of zero secrecy capacity.