Semi-grant-free (SGF) transmission scheme enables grant-free (GF) users to utilize resource block... more Semi-grant-free (SGF) transmission scheme enables grant-free (GF) users to utilize resource blocks allocated for grant-based (GB) users while maintaining the quality of service of GB users. This work investigates the secrecy performance of non-orthogonal multiple access (NOMA)-aided SGF systems. First, analytical expressions for the exact and asymptotic secrecy outage probability (SOP) of NOMAaided SGF systems with a single GF user are derived. Then, the SGF systems with multiple GF users and the best-user scheduling scheme is considered. By utilizing order statistics theory, analytical expressions for the exact and asymptotic SOP are derived. Monte Carlo simulation results are provided and compared with two benchmark schemes. The effects of system parameters on the SOP of the considered system are demonstrated and the accuracy of the developed analytical results is verified. The results indicate that both the outage target rate for GB and the secure target rate for GF are the main factors of the secrecy performance of SGF systems. Index Terms Non-orthogonal multiple access (NOMA), semi-grant-free (SGF) transmission scheme, grant-free (GF) user, grant-based (GB) user, secrecy outage probability. I. INTRODUCTION A. Background and Related Work Ultra-reliable low latency communications (URLLC) and massive machine-type communications (mMTC) are the two most important scenarios for the next internet of things (IoT). URLLC focuses on mission-critical applications wherein unprecedented levels of reliability and latency Manuscript received.
We analyze the secrecy outage performance of a mixed radio frequency-free space optical (RF-FSO) ... more We analyze the secrecy outage performance of a mixed radio frequency-free space optical (RF-FSO) transmission system with imperfect channel state information (CSI). We deal with a single-input multiple-output (SIMO) wiretap model, where a base station (works as the relay) forwards the signal transmitted from a user (source) to a data center (works as the destination), while an eavesdropper wiretaps the confidential information by decoding the received signal. Both the relay and the eavesdropper are armed with multiple antennas and maximal ratio combining scheme is utilized to improve the received signal-to-noise ratio (SNR). The effects of imperfect CSI of the RF link and the FSO link, misalignment, detection schemes, and relaying schemes on the secrecy outage performance of mixed RF-FSO systems are studied. Firstly, the cumulative distribution function and probability density function of FSO links with pointing error and two different detection technologies are derived. Then we derive the closed-form expressions for the lower bound of the secrecy outage probability (SOP) with fixed-gain relaying and variable-gain relaying schemes. Furthermore, asymptotic results for SOP are investigated by exploiting the unfolding of Meijer's G-function when the electrical SNR of FSO link approaches infinity. Finally, Monte-Carlo simulation results are presented to corroborate the correctness of the analysis.
Dedicated control channel protocol is a kind of classic multi-channel MAC (Medium Access Control)... more Dedicated control channel protocol is a kind of classic multi-channel MAC (Medium Access Control) protocol, in which a common channel is used as a control channel to negotiate, and the remaining channels are used for data exchange. However, a large number of overhead produced in channel consultation easily leads to control channel saturation problem, which reduces both the network throughput and channel utilization. In this paper, we propose a new multiple radio MAC protocol named Enhanced Dedicated Control Channel (EDCC) protocol. A strategy named TXOP (Transmission Opportunity) is used to solve this problem for WMNs. Several continuous data frames don't need to negotiate channel and are transmitted on the same channel which was selected before. This scheme can drastically reduce the overhead for consultation on the control channel and make the common control channel become not as busy as before. Simulation results show that EDCC improves the throughput of each data channel through reducing consultation overhead and makes the control channel be able to support negotiation for more data channels. As a result, system performance is improved.
Semi-grant-free (SGF) transmission scheme enables grant-free (GF) users to utilize resource block... more Semi-grant-free (SGF) transmission scheme enables grant-free (GF) users to utilize resource blocks allocated for grant-based (GB) users while maintaining the quality of service of GB users. This work investigates the secrecy performance of non-orthogonal multiple access (NOMA)-aided SGF systems. First, analytical expressions for the exact and asymptotic secrecy outage probability (SOP) of NOMAaided SGF systems with a single GF user are derived. Then, the SGF systems with multiple GF users and the best-user scheduling scheme is considered. By utilizing order statistics theory, analytical expressions for the exact and asymptotic SOP are derived. Monte Carlo simulation results are provided and compared with two benchmark schemes. The effects of system parameters on the SOP of the considered system are demonstrated and the accuracy of the developed analytical results is verified. The results indicate that both the outage target rate for GB and the secure target rate for GF are the main factors of the secrecy performance of SGF systems. Index Terms Non-orthogonal multiple access (NOMA), semi-grant-free (SGF) transmission scheme, grant-free (GF) user, grant-based (GB) user, secrecy outage probability. I. INTRODUCTION A. Background and Related Work Ultra-reliable low latency communications (URLLC) and massive machine-type communications (mMTC) are the two most important scenarios for the next internet of things (IoT). URLLC focuses on mission-critical applications wherein unprecedented levels of reliability and latency Manuscript received.
We analyze the secrecy outage performance of a mixed radio frequency-free space optical (RF-FSO) ... more We analyze the secrecy outage performance of a mixed radio frequency-free space optical (RF-FSO) transmission system with imperfect channel state information (CSI). We deal with a single-input multiple-output (SIMO) wiretap model, where a base station (works as the relay) forwards the signal transmitted from a user (source) to a data center (works as the destination), while an eavesdropper wiretaps the confidential information by decoding the received signal. Both the relay and the eavesdropper are armed with multiple antennas and maximal ratio combining scheme is utilized to improve the received signal-to-noise ratio (SNR). The effects of imperfect CSI of the RF link and the FSO link, misalignment, detection schemes, and relaying schemes on the secrecy outage performance of mixed RF-FSO systems are studied. Firstly, the cumulative distribution function and probability density function of FSO links with pointing error and two different detection technologies are derived. Then we derive the closed-form expressions for the lower bound of the secrecy outage probability (SOP) with fixed-gain relaying and variable-gain relaying schemes. Furthermore, asymptotic results for SOP are investigated by exploiting the unfolding of Meijer's G-function when the electrical SNR of FSO link approaches infinity. Finally, Monte-Carlo simulation results are presented to corroborate the correctness of the analysis.
Dedicated control channel protocol is a kind of classic multi-channel MAC (Medium Access Control)... more Dedicated control channel protocol is a kind of classic multi-channel MAC (Medium Access Control) protocol, in which a common channel is used as a control channel to negotiate, and the remaining channels are used for data exchange. However, a large number of overhead produced in channel consultation easily leads to control channel saturation problem, which reduces both the network throughput and channel utilization. In this paper, we propose a new multiple radio MAC protocol named Enhanced Dedicated Control Channel (EDCC) protocol. A strategy named TXOP (Transmission Opportunity) is used to solve this problem for WMNs. Several continuous data frames don't need to negotiate channel and are transmitted on the same channel which was selected before. This scheme can drastically reduce the overhead for consultation on the control channel and make the common control channel become not as busy as before. Simulation results show that EDCC improves the throughput of each data channel through reducing consultation overhead and makes the control channel be able to support negotiation for more data channels. As a result, system performance is improved.
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Papers by Hongjiang Lei