The Experts below are selected from a list of 202290 Experts worldwide ranked by ideXlab platform
Yingchang Liang - One of the best experts on this subject based on the ideXlab platform.
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intelligent user association for symbiotic radio Networks using deep reinforcement learning
2020Co-Authors: Qianqian Zhang, Yingchang Liang, Vincent H PoorAbstract:In this paper, we are interested in symbiotic radio Networks (SRNs), in which an Internet-of-Things (IoT) Network parasitizes in a Primary cellular Network to achieve spectrum-, energy-, and infrastructure-efficient communications. Each IoT device transmits its own information by backscattering the signals from the Primary Network without using active radio-frequency (RF) transmitter chain. We consider the symbiosis between the cellular Network and the IoT Network and focus on the user association problem in SRN. Specifically, the base station (BS) in the Primary Network serves multiple cellular users using time division multiple access (TDMA) and each IoT device is associated with one cellular user for information transmission. The objective of user association is to link each IoT device to an appropriate cellular user by maximizing the sum rate of all IoT devices. However, the difficulty in obtaining the full real-time channel information makes it difficult to design an optimal policy for this problem. To overcome this issue, we propose two deep reinforcement learning (DRL) algorithms, both use historical information to infer the current information in order to make appropriate decisions. One algorithm, referred to as centralized DRL, makes decisions for all IoT devices at one time with globally available information. The other algorithm, referred to as distributed DRL, makes a decision only for one IoT device at one time using locally available information. Finally, simulation results show that the two proposed DRL algorithms achieve performance comparable to the optimal user association policy which requires perfect real-time information, and the distributed DRL algorithm has the advantage of scalability.
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a two level mac protocol strategy for opportunistic spectrum access in cognitive radio Networks
2011Co-Authors: Qian Chen, Yingchang Liang, Mehul Motani, Waichoong WongAbstract:In this paper, we consider medium access control (MAC) protocol design for random-access cognitive radio (CR) Networks. A two-level opportunistic spectrum access strategy is proposed to optimize the system performance of the secondary Network and to adequately protect the operation of the Primary Network. At the first level, secondary users (SUs) maintain a sufficient detection probability to avoid interference with Primary users (PUs), and the spectrum sensing time is optimized to control the total traffic rate of the secondary Network allowed for random access when the channel is detected to be available. At the second level, two MAC protocols called the slotted cognitive radio ALOHA (CR-ALOHA) and cognitive-radio-based carrier-sensing multiple access (CR-CSMA) are developed to deal with the packet scheduling of the secondary Network. We employ normalized throughput and average packet delay as the Network metrics and derive closed-form expressions to evaluate the performance of the secondary Network for our proposed protocols. Moreover, we use the interference and agility factors as the performance parameters to measure the protection effects on the Primary Network. For various frame lengths and numbers of SUs, the optimal performance of throughput and delay can be achieved at the same spectrum sensing time, and there also exists a tradeoff between the achievable performance of the secondary Network and the effects of protection on the Primary Network. Simulation results show that the CR-CSMA protocol outperforms the slotted CR-ALOHA protocol and that the PUs' activities have an influence on the performance of SUs for both the slotted CR-ALOHA and CR-CSMA.
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power control and channel allocation in cognitive radio Networks with Primary users cooperation
2010Co-Authors: Anh Tuan Hoang, Yingchang Liang, M H IslamAbstract:We consider a point-to-multipoint cognitive radio Network that shares a set of channels with a Primary Network. Within the cognitive radio Network, a base station controls and supports a set of fixed-location wireless subscribers. The objective is to maximize the throughput of the cognitive Network while not affecting the performance of Primary users. Both downlink and uplink transmission scenarios in the cognitive Network are considered. For both scenarios, we propose two-phase mixed distributed/centralized control algorithms that require minimal cooperation between cognitive and Primary devices. In the first phase, a distributed power updating process is employed at the cognitive and Primary nodes to maximize the coverage of the cognitive Network while always maintaining the constrained signal to interference plus noise ratio of Primary transmissions. In the second phase, centralized channel assignment is carried out within the cognitive Network to maximize its throughput. Numerical results are obtained for the behaviors and performance of our proposed algorithms.
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design and analysis for an 802 11 based cognitive radio Network
2009Co-Authors: Anh Tuan Hoang, David Tung Chong Wong, Yingchang LiangAbstract:This paper considers a distributed opportunistic spectrum access (D-OSA) scenario in which multiple cognitive radio (CR) users attempt to access a channel licensed to some Primary Network. CR users operate on a frame-by-frame basis and need to carry out spectrum sensing at the beginning of each frame to determine if the Primary Network is active or idle. Upon detecting the Primary Network being idle, each CR user employs a modified 802.11 DCF protocol for contention-based channel access. Spectrum sensing is imperfect and introduces false alarms and mis-detections. To protect Primary users, it is required that the combined probability of mis-detection of all CR users must be below a specified threshold. We provide concrete protocol design, performance analysis, and extensive simulation results for our D-OSA design. Our results highlight the importance of taking a cross-layer view and jointly designing PHY-layer spectrum sensing and MAC-layer channel access.
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opportunistic spectrum access for energy constrained cognitive radios
2009Co-Authors: Anh Tuan Hoang, Yingchang Liang, David Tung Chong Wong, Yonghong Zeng, Rui ZhangAbstract:This paper considers a scenario in which a secondary user (SU) opportunistically accesses a channel allocated to some Primary Network (PN) that switches between idle and active states in a time-slotted manner. At the beginning of each time slot, SU can choose to stay idle or to carry out spectrum sensing to detect the state of PN. If PN is detected to be idle, SU can carry out data transmission. Spectrum sensing consumes time and energy and introduces false alarms and mis-detections. The objective is to dynamically decide, for each time slot, whether SU should stay idle or carry out sensing, and if so, for how long, to maximize the expected reward. We formulate this as a partially observable Markov decision process and prove important properties of the optimal control policies. Heuristic control policies with low complexity and good performance are also proposed. Numerical results show the significant performance gain of our dynamic control approach for opportunistic spectrum access.
Trung Q. Duong - One of the best experts on this subject based on the ideXlab platform.
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Cognitive full-duplex relay Networks under the peak interference power constraint of multiple Primary users
2017Co-Authors: Xuan-toan Doan, Nam-phong Nguyen, Cheng Yin, Daniel B. Da Costa, Trung Q. DuongAbstract:This paper investigates the outage performance of cognitive spectrum-sharing multi-relay Networks in which the relays operate in a full-duplex (FD) mode and employ the decode-and-forward (DF) protocol. Two relay selection schemes, i.e., partial relay selection (PRS) and optimal relay selection (ORS), are considered to enhance the system performance. New exact expressions for the outage probability (OP) in both schemes are derived based on which an asymptotic analysis is carried out. The results show that the ORS strategy outperforms PRS in terms of OP, and increasing the number of FD relays can significantly improve the system performance. Moreover, novel analytical results provide additional insights for system design. In particular, from the viewpoint of FD concept, the Primary Network parameters (i.e., peak interference at the Primary receivers, number of Primary receivers, and their locations) should be carefully considered since they significantly affect the secondary Network performance.
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secure full duplex small cell Networks in a spectrum sharing environment
2016Co-Authors: Nam-phong Nguyen, Trung Q. Duong, Chinmoy Kundu, Berk CanberkAbstract:In this paper, we propose three relay selection schemes for full-duplex heterogeneous Networks in the presence of multiple cognitive radio eavesdroppers. In this setup, the cognitive small-cell nodes (secondary Network) can share the spectrum licensed to the macro-cell system (Primary Network) on the condition that the quality-of-service of the Primary Network is always satisfied subjected to its outage probability constraint. The messages are delivered from one small-cell base station to the destination with the help of full-duplex small-cell base stations, which act as relay nodes. Based on the availability of the Network’s channel state information at the secondary information source, three different selection criteria for full-duplex relays, namely: 1) partial relay selection; 2) optimal relay selection; and 3) minimal self-interference relay selection, are proposed. We derive the exact closed-form and asymptotic expressions of the secrecy outage probability for the three criteria under the attack of non-colluding/colluding eavesdroppers. We demonstrate that the optimal relay selection scheme outperforms the partial relay selection and minimal self-interference relay selection schemes at the expense of acquiring full channel state information knowledge. In addition, increasing the number of the full-duplex small-cell base stations can improve the security performance. At the illegitimate side, deploying colluding eavesdroppers and increasing the number of eavesdroppers put the confidential information at a greater risk. Besides, the transmit power and the desire outage probability of the Primary Network have great influences on the secrecy outage probability of the secondary Network.
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mimo cognitive relay Networks with correlated antennas over rayleigh fading channels
2016Co-Authors: Ahmed Abd H Elmalek, Trung Q. Duong, Fawaz S Alqahtani, Salam A Zummo, Hussein AlnuweiriAbstract:In this paper, we examine orthogonal space–time block coding with receiver maximal ratio combining (OSTBC/MRC) and selection combining (OSTBC/SC) in multiple-input–multiple-output (MIMO) decode-and-forward (DF) relay Networks with underlay spectrum sharing, considering optimal and suboptimal cases. The secondary Network under consideration is equipped with multiple correlated antennas at the source, the relay, and the destination. On the other hand, the Primary Network is composed of $L$ Primary users (PUs), each of which is equipped with multiple correlated antennas. For the considered underlay spectrum sharing, the transmit power condition is related by an interference limit on the Primary Network and the maximum transmission power in the secondary Network. In particular, new exact expressions for the outage probability of the adopted system models are obtained. Moreover, simple asymptotic expressions for the outage probability are provided to enable the characterization of the achievable diversity orders and coding gains. To enhance the secondary Network performance, optimal power allocation (PA) between the secondary source and the secondary relay is obtained based on the asymptotic outage probability under the constraints of total allowable transmit power at the secondary user (SU) and maximum allowable interference power limit at the PU. The derived analytical formulas herein are supported by numerical results to clarify the main contributions.
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on the security of cognitive radio Networks
2015Co-Authors: Maged Elkashlan, Trung Q. Duong, Lifeng Wang, George K Karagiannidis, Arumugam NallanathanAbstract:Cognitive radio has emerged as an essential recipe for future high-capacity, high-coverage multitier hierarchical Networks. Securing data transmission in these Networks is of the utmost importance. In this paper, we consider the cognitive wiretap channel and propose multiple antennas to secure the transmission at the physical layer, where the eavesdropper overhears the transmission from the secondary transmitter to the secondary receiver. The secondary receiver and the eavesdropper are equipped with multiple antennas, and passive eavesdropping is considered where the channel state information (CSI) of the eavesdropper's channel is not available at the secondary transmitter. We present new closed-form expressions for the exact and asymptotic secrecy outage probability. Our results reveal the impact of the Primary Network on the secondary Network in the presence of a multiantenna wiretap channel.
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On the Performance of Cognitive Underlay Multihop Networks with Imperfect Channel State Information
2013Co-Authors: Vo Nguyen Quoc Bao, Trung Q. Duong, Chintha TellamburaAbstract:This paper proposes and analyzes cognitive multihop decode-and-forward Networks in the presence of interference due to channel estimation errors. To reduce interference on the Primary Network, a simple yet effective back-off control power method is applied for secondary multihop Networks. For a given threshold of interference probability at the Primary Network, we derive the maximum back-off control power coefficient, which provides the best performance for secondary multihop Networks. Moreover, it is shown that the number of hops for secondary Network is upper-bounded under the fixed settings of the Primary Network. For secondary multihop Networks, new exact and asymptotic expressions for outage probability (OP), bit error rate (BER) and ergodic capacity over Rayleigh fading channels are derived. Based on the asymptotic OP and BEP, a pivotal conclusion is reached that the secondary multihop Network offers the same diversity order as compared with the Network without back off. Finally, we verify the performance analysis through various numerical examples which confirm the correctness of our analysis for many channel and system settings and provide new insight into the design and optimization of cognitive multihop Networks.
Anh Tuan Hoang - One of the best experts on this subject based on the ideXlab platform.
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power control and channel allocation in cognitive radio Networks with Primary users cooperation
2010Co-Authors: Anh Tuan Hoang, Yingchang Liang, M H IslamAbstract:We consider a point-to-multipoint cognitive radio Network that shares a set of channels with a Primary Network. Within the cognitive radio Network, a base station controls and supports a set of fixed-location wireless subscribers. The objective is to maximize the throughput of the cognitive Network while not affecting the performance of Primary users. Both downlink and uplink transmission scenarios in the cognitive Network are considered. For both scenarios, we propose two-phase mixed distributed/centralized control algorithms that require minimal cooperation between cognitive and Primary devices. In the first phase, a distributed power updating process is employed at the cognitive and Primary nodes to maximize the coverage of the cognitive Network while always maintaining the constrained signal to interference plus noise ratio of Primary transmissions. In the second phase, centralized channel assignment is carried out within the cognitive Network to maximize its throughput. Numerical results are obtained for the behaviors and performance of our proposed algorithms.
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design and analysis for an 802 11 based cognitive radio Network
2009Co-Authors: Anh Tuan Hoang, David Tung Chong Wong, Yingchang LiangAbstract:This paper considers a distributed opportunistic spectrum access (D-OSA) scenario in which multiple cognitive radio (CR) users attempt to access a channel licensed to some Primary Network. CR users operate on a frame-by-frame basis and need to carry out spectrum sensing at the beginning of each frame to determine if the Primary Network is active or idle. Upon detecting the Primary Network being idle, each CR user employs a modified 802.11 DCF protocol for contention-based channel access. Spectrum sensing is imperfect and introduces false alarms and mis-detections. To protect Primary users, it is required that the combined probability of mis-detection of all CR users must be below a specified threshold. We provide concrete protocol design, performance analysis, and extensive simulation results for our D-OSA design. Our results highlight the importance of taking a cross-layer view and jointly designing PHY-layer spectrum sensing and MAC-layer channel access.
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opportunistic spectrum access for energy constrained cognitive radios
2009Co-Authors: Anh Tuan Hoang, Yingchang Liang, David Tung Chong Wong, Yonghong Zeng, Rui ZhangAbstract:This paper considers a scenario in which a secondary user (SU) opportunistically accesses a channel allocated to some Primary Network (PN) that switches between idle and active states in a time-slotted manner. At the beginning of each time slot, SU can choose to stay idle or to carry out spectrum sensing to detect the state of PN. If PN is detected to be idle, SU can carry out data transmission. Spectrum sensing consumes time and energy and introduces false alarms and mis-detections. The objective is to dynamically decide, for each time slot, whether SU should stay idle or carry out sensing, and if so, for how long, to maximize the expected reward. We formulate this as a partially observable Markov decision process and prove important properties of the optimal control policies. Heuristic control policies with low complexity and good performance are also proposed. Numerical results show the significant performance gain of our dynamic control approach for opportunistic spectrum access.
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downlink channel assignment and power control for cognitive radio Networks
2008Co-Authors: Anh Tuan Hoang, Yingchang LiangAbstract:We consider a cognitive radio Network in which a set of base stations make opportunistic spectrum access to support fixed-location wireless subscribers within their cells. The spectrum of interest is divided into independent channels using frequency division multiple access (FDMA) and is licensed to the operator of a Primary Network. Channel assignment and power control must be carried out in the cognitive Network so that no excessive interference is caused to users of the Primary Network. We are interested in the downlink channel/power allocation problem for the cognitive radio Network, with the objective of maximizing the total number of active subscribers that can be supported. Here, we assume that each subscriber of the cognitive Network can be either active or idle and only active subscribers require downlink transmission. We first consider the case when global knowledge of all active subscribers is available for making control decisions. In that case, a downlink channel/power allocation scheme that maximizes the number of supported subscribers can be obtained by solving a mixed-integer linear programming. We also propose a suboptimal scheme that can be obtained at lower complexity based on a dynamic interference graph. We then consider the case when control decisions can only be made based on local knowledge of active subscribers within each cell. For that, we propose a scalable two-phase channel/power allocation scheme. Numerical results show the effectiveness of our proposed schemes.
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a two phase channel and power allocation scheme for cognitive radio Networks
2006Co-Authors: Anh Tuan Hoang, Yingchang LiangAbstract:We consider a cognitive radio Network in which a set of base stations make opportunistic unlicensed spectrum access to transmit data to their subscribers. As the spectrum of interest is licensed to another (Primary) Network, power and channel allocation must be carried out within the cognitive radio Network so that no excessive interference is caused to any Primary user. For such a cognitive Network, we propose a two-phase channel/power allocation scheme that improves the system throughput, defined as the total number of subscribers that can be simultaneously served. In the first phase of our scheme, channels and power are allocated to base stations with the aim of maximizing their total coverage while keeping the interference caused to each Primary user below a predefined threshold. In the second phase, each base station allocates channels to their active subscribers based on a maximal bipartite matching algorithm. Numerical results show that our proposed resource allocation scheme yields significant improvement in the system throughput.
Vo Nguyen Quoc Bao - One of the best experts on this subject based on the ideXlab platform.
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On the Performance of Cognitive Underlay Multihop Networks with Imperfect Channel State Information
2013Co-Authors: Vo Nguyen Quoc Bao, Trung Q. Duong, Chintha TellamburaAbstract:This paper proposes and analyzes cognitive multihop decode-and-forward Networks in the presence of interference due to channel estimation errors. To reduce interference on the Primary Network, a simple yet effective back-off control power method is applied for secondary multihop Networks. For a given threshold of interference probability at the Primary Network, we derive the maximum back-off control power coefficient, which provides the best performance for secondary multihop Networks. Moreover, it is shown that the number of hops for secondary Network is upper-bounded under the fixed settings of the Primary Network. For secondary multihop Networks, new exact and asymptotic expressions for outage probability (OP), bit error rate (BER) and ergodic capacity over Rayleigh fading channels are derived. Based on the asymptotic OP and BEP, a pivotal conclusion is reached that the secondary multihop Network offers the same diversity order as compared with the Network without back off. Finally, we verify the performance analysis through various numerical examples which confirm the correctness of our analysis for many channel and system settings and provide new insight into the design and optimization of cognitive multihop Networks.
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Cognitive underlay communications with imperfect CSI: Network design and performance analysis
2013Co-Authors: Nguyen Hong Giang, Vo Nguyen Quoc Bao, Hung Nguyen-leAbstract:This paper is concerned with performance analysis of cognitive underlay partial relay Networks with imperfect channel state information (CSI). To assure the required quality of service (QoS) at Primary receivers, transmit power at secondary nodes is adjusted by using a back-off power scheme under imperfect CSI condition. The back-off power strategy reduces transmit power at secondary nodes and in turn degrades the secondary Network performance. Under the performance tradeoff between Primary and secondary Networks, this paper considers the use of multiple antennas at destination node and partial relay selection to enhance the secondary Network performance without sacrificing the performance of the Primary Network. To justify the benefit of using the Network design, several analytical and simulated results of the Network performance are provided under various system settings.
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cognitive amplify and forward relay Networks over nakagami m fading
2012Co-Authors: Trung Q. Duong, Maged Elkashlan, Daniel Benevides Da Costa, Vo Nguyen Quoc BaoAbstract:In this correspondence, the outage probability (OP) of dual-hop cognitive amplify-and-forward (AF) relay Networks subject to independent non-identically distributed (i.n.i.d.) Nakagami-m fading is examined. We assume a spectrum-sharing environment, where two different strategies are proposed to determine the transmit powers of the secondary Network. Specifically, the transmit power conditions of the proposed spectrum-sharing Network are governed by either the combined power constraint of the interference on the Primary Network and the maximum transmission power at the secondary Network or the single power constraint of the interference on the Primary Network. Closed-form lower bounds and asymptotic expressions for the OP are derived. Regardless of the transmit power constraint, we reveal that the diversity order is strictly defined by the minimum fading severity between the two hops of the secondary Network. This aligns with the well-known result for conventional dual-hop AF relaying without spectrum sharing. Furthermore, the impact of the Primary Network on the diversity-multiplexing tradeoff is investigated. We confirm that the diversity-multiplexing tradeoff is independent of the Primary Network.
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effect of Primary Network on performance of spectrum sharing af relaying
2012Co-Authors: Trung Q. Duong, Hung Tran, Vo Nguyen Quoc Bao, George C Alexandropoulos, Hansjurgen ZepernickAbstract:Most of the research in spectrum sharing has neglected the effect of interference from Primary users. In this reported work, the performance of spectrum sharing amplify-and-forward relay Networks under interference-limited environment, where the interference induced by the transmission of Primary Networks is taken into account, is investigated. In particular, a closed-form expression tight lower bound of outage probability is derived. To reveal additional insights into the effect of Primary Networks on the diversity and array gains, an asymptotic expression is also obtained.
Hung Tran - One of the best experts on this subject based on the ideXlab platform.
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on the outage capacity of an underlay cognitive radio Network
2015Co-Authors: Louis Sibomana, Hans-Jürgen Zepernick, Hung TranAbstract:In this paper, we consider a point-to-multipoint underlay cognitive radio Network under the joint constraint of the Primary user peak interference power and maximum transmit power limit of the secondary user (SU). Analytical expressions for the secondary outage capacity are obtained based on exact as well as approximate expressions of the first and second moments of the channel capacity. Numerical results are provided to assess the effect of the number of SU receivers and a given SU outage probability. We also evaluate the impact of the Primary Network parameters on the secondary Network performance.
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On physical layer security for reactive DF cognitive relay Networks
2014Co-Authors: Louis Sibomana, Hans-Jürgen Zepernick, Hung TranAbstract:This paper analyzes the physical layer security for cognitive relay Networks under the peak interference power constraint of the Primary user receiver. In particular, a secondary user (SU) transmitter communicates with an SU receiver through the help of multiple secondary relays (SRs) using a decode-and-forward (DF) protocol. There exist multiple eavesdroppers (EAVs) who illegally listen to the secondary Network communication. We consider a reactive DF scheme, and only the SRs that satisfy a decoding threshold participate in the relay selection. Analytical expressions of the probability of existence of secrecy capacity and secrecy outage probability are obtained. Numerical results are provided to evaluate the impact of the number of SRs, number of EAVs and channel mean powers on the secondary system security. We also investigate the effect of the interference from the Primary Network to the secondary Network performance. Moreover, the performance of proactive DF is analyzed for the purpose of comparison.
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on non zero secrecy capacity and outage probability of cognitive radio Networks
2013Co-Authors: Louis Sibomana, Hung Tran, Hansjurgen Zepernick, Charles KabiriAbstract:In this paper, we consider a spectrum sharing cognitive radio Network (CRN) in the presence of an eavesdropper (EAV) who illegally listens to the Primary user (PU) communication. Under the PU outage and the secondary user (SU) peak transmit power constraints, the adaptive transmit power policy of the SU transmitter (SU-Tx) is obtained. Then, expressions for the probability of existence of a non-zero secrecy capacity of the Primary Network and the outage probability of the secondary Network are derived. Numerical results are provided to investigate the impact of the SU-Tx peak transmit power, PU average transmit power and channel mean powers among users on the outage probability and probability of existence of a non-zero secrecy capacity. Our results illustrate that the probability of existence of a non-zero secrecy capacity strongly depends on the channel conditions among users and SU-Tx adaptive transmit power policy.
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effect of Primary Network on performance of spectrum sharing af relaying
2012Co-Authors: Trung Q. Duong, Hung Tran, Vo Nguyen Quoc Bao, George C Alexandropoulos, Hansjurgen ZepernickAbstract:Most of the research in spectrum sharing has neglected the effect of interference from Primary users. In this reported work, the performance of spectrum sharing amplify-and-forward relay Networks under interference-limited environment, where the interference induced by the transmission of Primary Networks is taken into account, is investigated. In particular, a closed-form expression tight lower bound of outage probability is derived. To reveal additional insights into the effect of Primary Networks on the diversity and array gains, an asymptotic expression is also obtained.
