41 research outputs found
Physical Layer Security with Threshold-Based Multiuser Scheduling in Multi-antenna Wireless Networks
Cooperative Transmission in Mobile Wireless Sensor Networks with Multiple Carrier Frequency Offsets: A Double-Differential Approach
As a result of the rapidly increasing mobility of sensor nodes, mobile wireless sensor networks (MWSNs) would be subject to multiple carrier frequency offsets (MCFOs), which result in time-varying channels and drastically degrade the network performance. To enhance the performance of such MWSNs, we propose a relay selection (RS) based double-differential (DD) cooperative transmission scheme, termed RSDDCT, in which the best relay sensor node is selected to forward the source sensor node’s signals to the destination sensor node with the detect-and-forward (DetF) protocol. Assuming a Rayleigh fading environment, first, exact closed-form expressions for the outage probability and average bit error rate (BER) of the RSDDCT scheme are derived. Then, simple and informative asymptotic outage probability and average BER expressions at the large signal-to-noise ratio (SNR) regime are presented, which reveal that the RSDDCT scheme can achieve full diversity. Furthermore, the optimum power allocation strategy in terms of minimizing the average BER is investigated, and simple analytical solutions are obtained. Simulation results demonstrate that the proposed RSDDCT scheme can achieve excellent performance over fading channels in the presence of unknown random MCFOs. It is also shown that the proposed optimum power allocation strategy offers substantial average BER performance improvement over the equal power allocation strategy
Secure Multiuser Communications in Wireless Sensor Networks with TAS and Cooperative Jamming
In this paper, we investigate the secure transmission in wireless sensor networks (WSNs) consisting of one multiple-antenna base station (BS), multiple single-antenna legitimate users, one single-antenna eavesdropper and one multiple-antenna cooperative jammer. In an effort to reduce the scheduling complexity and extend the battery lifetime of the sensor nodes, the switch-and-stay combining (SSC) scheduling scheme is exploited over the sensor nodes. Meanwhile, transmit antenna selection (TAS) is employed at the BS and cooperative jamming (CJ) is adopted at the jammer node, aiming at achieving a satisfactory secrecy performance. Moreover, depending on whether the jammer node has the global channel state information (CSI) of both the legitimate channel and the eavesdropper's channel, it explores a zero-forcing beamforming (ZFB) scheme or a null-space artificial noise (NAN) scheme to confound the eavesdropper while avoiding the interference to the legitimate user. Building on this, we propose two novel hybrid secure transmission schemes, termed TAS-SSC-ZFB and TAS-SSC-NAN, for WSNs. We then derive the exact closed-form expressions for the secrecy outage probability and the effective secrecy throughput of both schemes to characterize the secrecy performance. Using these closed-form expressions, we further determine the optimal switching threshold and obtain the optimal power allocation factor between the BS and jammer node for both schemes to minimize the secrecy outage probability, while the optimal secrecy rate is decided to maximize the effective secrecy throughput for both schemes. Numerical results are provided to verify the theoretical analysis and illustrate the impact of key system parameters on the secrecy performance.This work was supported by the National Science Foundation of China (No. 61501507), and the Jiangsu Provincial Natural Science Foundation of China (No. BK20150719). The work of Nan Yang is supported by the Australian Research Council Discovery Project (DP150103905)
Outage analysis of cognitive hybrid satellite-terrestrial networks with hardware impairments and multi-primary users
This paper investigates the effects of practical hardware impairments (HIs) on a cognitive hybrid satellite-terrestrial networks (CHSTN) with multiple primary users (PUs). The widely-employed Shadowed-Rician fading distribution is adopted to model the satellite-terrestrial channel. CHSTN can provide comprehensive wireless coverage as well as enhanced spectrum resource usage by considering the requirements of both spectrum efficiency and reliability. Specifically, we derive the closed-form expression of the outage probability (OP) for the considered system in the presence of interference power constraints imposed by multiple adjacent terrestrial PUs. To gain further insights at high signal-to-noise ratios (SNRs), the asymptotic expression for the OP is also derived. Numerical results confirm the correctness and effectiveness of our performance analysis
Secrecy Enhancement of Multiuser MISO Networks Using OSTBC and Artificial Noise
In this paper, we propose a novel physical layer
strategy to improve the secrecy performance of multiuser
multiple-input single-output networks. In this strategy, orthogonal
space-time block code (OSTBC) is employed at an AAantenna
base station (BS) and artificial noise (AN) is employed
at an AJ-antenna cooperative relay to enhance the security
level of the network. Moreover, two opportunistic scheduling
schemes, namely, selection combining (SC) and scan-and-wait
combining (SWC), are leveraged to select one legitimate user
for data transmission. To evaluate the secrecy performance of
the proposed OSTBC-SC-AN and OSTBC-SWC-AN schemes, we
derive new exact closed-form expressions for the secrecy outage
probability and the effective secrecy throughput. Using numerical
results, we show that the OSTBC-SWC-AN scheme outperforms
the OSTBC-SC-AN scheme when the switching threshold is
carefully chosen. We also show that increasing AA brings down
the secrecy performance in the presence of a high switching
threshold.ARC Discovery Projects Grant DP150103905
A Robust Cooperative Spectrum Sensing-Assisted Multiuser Resource Allocation Scheme
Cognitive radio (CR), which is proposed as a solution for spectrum scarcity, imposes some threats to the network. One severe attack to cognitive radio network is the primary user emulation attack (PUEA), in which an attacker may transmit its signal with high power or mimic specific features of the primary user's signal to prevent secondary users from accessing the licensed spectrum. In this paper, we study a subcarrier and power allocation problem for orthogonal frequency division multiple access-(OFDMA-) based CR systems in the presence of PUEA. To maximize the system throughput while keeping the interference introduced to the primary user (PU) below given thresholds with a certain probability, a joint design of a robust cooperative spectrum sensing and a resource allocation scheme is proposed. In the proposed scheme, the inaccurate classification of PU signals and PUEA signals provided by robust cooperative spectrum sensing is utilized by resource scheduling module. To further exploit the underutilized spectrum bands, we also evaluate the performance of the proposed scheme in the hybrid overlay/underlay spectrum access mechanism. Numerical results demonstrate the effectiveness of the proposed scheme compared to conventional scheme regardless of the number of SUs or the kind of spectrum access mechanism being used
Stochastic Geometry-Based Analysis of Cache-Enabled Hybrid Satellite-Aerial-Terrestrial Networks With Non-Orthogonal Multiple Access
Due to the emergence of non-terrestrial platformswith extensive coverage, flexible deployment, and reconfigurablecharacteristics, the hybrid satellite-aerial-terrestrial networks(HSATNs) can accommodate a great variety of wireless accessservices in different applications. To effectively reduce the trans-mission latency and facilitate the frequent update of files withimproved spectrum efficiency, we investigate the performanceof cache-enabled HSATN, where the user retrieves the requiredcontent files from the cache-enabled aerial relay or the satellitewith the non-orthogonal multiple access (NOMA) scheme. If therequired content files of the user are cached in the aerial relay,the cache-enabled relay would serve directly. Otherwise, the userwould retrieve the content file from the satellite system, where thesatellite system seeks opportunities for proactive content pushingto the relay during the user content delivery phase. Specifically,taking into account the uncertainty of the number and locationof aerial relays, along with the channel fading of terrestrialusers, the outage probability and hit probability of the considerednetwork are, respectively, derived based on stochastic geometry.Numerical results unveil the effectiveness of the cache-enabledHSATN with the NOMA scheme and proclaim the influence ofkey factors on the system performance. The realistic, tractable,and expandable framework, as well as associated methodology,provide both useful guidance and a solid foundation for evolvednetworks with advanced configurations in the performance ofcache-enabled HSATN
Auction-based Multi-Channel Cooperative Spectrum Sharing in Hybrid Satellite-Terrestrial IoT Networks
In this paper, we investigate the multi-channel cooperative
spectrum sharing in hybrid satellite-terrestrial internet
of things (IoT) networks with the auction mechanism, which is
designed to reduce the operational expenditure of the satellitebased
IoT (S-IoT) network while alleviating the spectrum scarcity
issues of terrestrial-based IoT (T-IoT) network. The cluster
heads of selected T-IoT networks assist the primary satellite
users transmission through cooperative relaying techniques in
exchange for spectrum access. We propose an auction-based
optimization problem to maximize the sum transmission rate
of all primary S-IoT receivers with the appropriate secondary
network selection and corresponding radio resource allocation
profile by the distributed implementation while meeting the
minimum transmission rate of secondary receivers of each TIoT
network. Specifically, the one-shot Vickrey-Clarke-Groves
(VCG) auction is introduced to obtain the maximum social
welfare, where the winner determination problem is transformed
into an assignment problem and solved by the Hungarian algorithm.
To further reduce the primary satellite network decision
complexity, the sequential Vickrey auction is implemented by
sequential fashion until all channels are auctioned. Due to
incentive compatibility with those two auction mechanisms, the
secondary T-IoT cluster yields the true bids of each channel,
where both the non-orthogonal multiple access (NOMA) and time
division multiple access (TDMA) schemes are implemented in
cooperative communication. Finally, simulation results validate
the effectiveness and fairness of the proposed auction-based
approach as well as the superiority of the NOMA scheme in
secondary relays selection. Moreover, the influence of key factors
on the performance of the proposed scheme is analyzed in detail
A Cooperative Mobile Satellite Communication System with the Dynamic Space-Time Coding
Channels of mobile satellite communications are affected by multipath fading and shadowing attenuation. At the same time, diversity gains are believed to improve the transmission reliability in fading channels. Considering that the traditional Space-Time Coding (STC) is not suitable for the cooperative mobile satellite communication, in this paper, a new cooperative mobile satellite communication system is proposed based on the Dynamic Space-Time Coding (D-STC). The transmitting energy of the proposed scheme is saved by avoiding forwarding erroneous signals in cooperative users. Meanwhile, this system benefits from diversity gains and the transmission is robust. Additionally, a closed-form expression of the outage probability for the proposed scheme is derived, and then it is demonstrated that this scheme is much better than the existing noncooperative scheme and schemes with traditional STCs in the outage performance. Finally, the analytical result is supported and validated by numerical simulations