| 1. |
- Duong, Quang Trung, et al.
(författare)
-
Keyhole Effect in Dual-Hop MIMO AF Relay Transmission with Space-Time Block Codes
- 2012
-
Ingår i: IEEE Transactions on Communications. - : IEEE. - 0090-6778 .- 1558-0857. ; 60:12, s. 1-11
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, the effect of keyhole on the performance of multiple-input multiple-output (MIMO) amplifyand-forward (AF) relay networks with orthogonal space-time block codes (OSTBCs) transmission is investigated. In particular, we analyze the asymptotic symbol error probability (SEP) performance of a downlink communication system where the amplifying processing at the relay can be implemented by either the linear or squaring approach. Our tractable asymptotic SEP expressions enable us to obtain both diversity and array gains. Our finding reveals that with condition nS > min(nR, nD), the linear approach can provide the full achievable diversity gain of min(nR, nD) when only the second hop suffers from the keyhole effect, i.e., single keyhole effect (SKE), where nS, nR, and nD are the number of antennas at source, relay, and destination, respectively. However, for the case that both the source-relay and relay-destination links experience the keyhole effect, i.e., double keyhole effect (DKE), the achievable diversity order is only one regardless of the number of antennas. In contrast, utilizing the squaring approach, the overall diversity gain can be achieved as min(nR, nD) for both SKE and DKE. An important observation corroborated by our studies is that for satisfying the tradeoff between performance and complexity, we should use the linear approach for SKE and the squaring approach for DKE.
|
|
| 2. |
- Duong, Quang Trung, et al.
(författare)
-
OSTBC Transmission in MIMO AF Relay Systems with Keyhole and Spatial Correlation Effects
- 2011
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we investigate the degenerative effects of antenna correlation and keyhole on the performance of multiple-input multiple-output (MIMO) amplify-and-forward (AF) relay networks. In particular, we considered a downlink MIMO AF relay system consisting of an nS-antenna base station S, an nR-antenna relay station R, and an nD-antenna mobile station D, in which the signal propagation originated from the mobile station suffers from keyhole and spatial correlation effects. We have derived an exact expression for the moment generation function of the instantaneous signal-to-noise ratio which enables us to analyze the symbol error probability and outage probability of the considered system.We have shown that although the mobile station is in a poor scattering environment, i.e., keyhole, the relay channel (S → R → D link) still achieves a cooperative diversity order of min(nR, nD) provided that the channel from the source (S → R link) is keyhole-free. This result is important to radio system designers since under such a severe scenario it is unnecessary to deploy a large number of antennas on the relay station (nR) but only requires nR = nD to obtain the maximum achievable diversity gain.
|
|
| 3. |
- Wang, Kewei, et al.
(författare)
-
Reconfigurable Intelligent Surfaces Aided Energy Efficiency Maximization in Cell-Free Networks
- 2024
-
Ingår i: IEEE Wireless Communications Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 2162-2337 .- 2162-2345. ; 13:6, s. 1596-1600
-
Tidskriftsartikel (refereegranskat)abstract
- As we move towards next-generation wireless networks, the need for sustainability through energy efficiency (EE) concepts becomes more important than ever. Meanwhile, technology enablers, such as beamforming and reconfigurable intelligent surfaces (RISs), if appropriately used in a synergetic manner, can deliver profound excellence in terms of EE. Motivated by this, in this letter, we introduce an EE maximization policy that accounts for the rate demands of the end-users in RIS-assisted cell-free networks. The policy aims at performing joint optimization of the transmit beamforming vectors and the RIS phase-shift matrices in order to maximize the EE. In this direction, we first formulate the corresponding optimization problem, which is non-convex. To solve it, we rely on advanced optimization methods such as quadratic and Lagrangian dual transforms. Numerical results highlight the superiority of the presented policy in comparison to baseline approaches and reveal the most impactful network parameters.
|
|
| 4. |
- Bao, Jinchen, et al.
(författare)
-
Bit-Interleaved Coded SCMA With Iterative Multiuser Detection : Multidimensional Constellations Design
- 2018
-
Ingår i: IEEE Transactions on Communications. - : IEEE Press. - 0090-6778 .- 1558-0857. ; 66:11, s. 5292-5304
-
Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the constellation/codebook design of a promising uplink multiple access technique, sparse code multiple access (SCMA), proposed for the fifth generation mobile networks. The application of bit-interleaved coded modulation with iterative multiuser detection is considered for uplink SCMA over fading channels. Extrinsic information transfer chart is used to aid the analysis and the design of multidimensional constellations, and the design criteria for multidimensional constellations and labelings optimization are thus established. Furthermore, a new and simple approach of multi-stage optimization for the multidimensional constellation design is proposed for SCMA, to improve the bit-error rate performance and alleviate the complexity of turbo multiuser detection. Numerical and simulation results are also provided to demonstrate the performance and verify the efficiency of the proposed scheme, compared with the state of the art.
|
|
| 5. |
- Ding, Guoru, et al.
(författare)
-
Robust Online Spectrum Prediction With Incomplete and Corrupted Historical Observations
- 2017
-
Ingår i: IEEE Transactions on Vehicular Technology. - : IEEE. - 0018-9545 .- 1939-9359. ; 66:9, s. 8022-8036
-
Tidskriftsartikel (refereegranskat)abstract
- A range of emerging applications, from adaptive spectrum sensing to proactive spectrum mobility, depend on the ability to foresee spectrum state evolution. Despite a number of studies appearing about spectrum prediction, fundamental issues still remain unresolved: 1) The existing studies do not explicitly account for anomalies, which may incur serious performance degradation; 2) they focus on the design of batch spectrum prediction algorithms, which limit the scalability to analyze massive spectrum data in real time; 3) they assume the historical data are complete, which may not hold in reality. To address these issues, we develop a Robust Online Spectrum Prediction (ROSP) framework, with incomplete and corrupted observations, in this paper. We first present data analytics of real-world spectrum measurements to reveal the correlation structures of spectrum evolution and to analyze the impact of anomalies on the rank distribution of spectrum matrices. Then, from a spectral–temporal 2-D perspective, we formulate the ROSP as a joint optimization problem of matrix completion and recovery by effectively integrating the time series forecasting techniques and develop an alternating direction optimization method to efficiently solve it. We apply ROSP to a wide range of real-world spectrum matrices of popular wireless services. Experiment results show that ROSP outperforms state-of-the-art spectrum prediction schemes.
|
|
| 6. |
- Duong, Quang Trung, et al.
(författare)
-
Amplify-and-Forward MIMO Relaying with OSTBC over Nakagami-m Fading Channels
- 2010
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we analyze the performance of dual-hop channel state information (CSI)-assisted amplify-andforward (AF) cooperative networks using orthogonal space-time block codes (OSTBCs) over independent but not identically distributed Nakagami-m fading channels. Specifically, we present closed-form expressions of the outage probability (OP) and the symbol error probability (SEP). The analytical results are given in tractable forms which readily allow us to assess the performance of AF relay systems using OSTBCs. For sufficiently large signal-to-noise ratio, we obtain the asymptotic results for OP and SEP which reveal insights into the effect of fading factors on the diversity and coding gains. It has been shown that between the two hops the more severe link solely determines the diversity and coding gains. In particular, these two gains strictly depend on the fading severity parameters and the channel mean powers of the more rigorous hop, respectively. Numerical results are provided showing an excellent agreement between our analytical results and those of Monte-Carlo simulations for selected scenarios.
|
|
| 7. |
- Duong, Quang Trung, et al.
(författare)
-
Orthogonal Space-Time Block Codes with CSI-Assisted Amplify-and-Forward Relaying in Correlated Nakagami-m Fading Channels
- 2011
-
Ingår i: IEEE Transactions on Vehicular Technology. - : IEEE. - 0018-9545 .- 1939-9359. ; 60:3, s. 882-889
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, the performance of multiple-input multiple-output (MIMO) dual-hop amplify-and-forward (AF) relay systems using orthogonal space-time block codes (OSTBCs) over arbitrarily correlated Nakagami-m fading channels is analyzed. In particular, closed-form expressions for the end-to-end outage probability (OP) and the symbol error probability (SEP) with arbitrary number of transceiver antennas and general correlation matrices are derived. Their mathematically tractable forms readily enable us to evaluate the performance of MIMO AF relay systems that utilize OSTBCs. For sufficiently high signal-to-noise ratios, asymptotically tight approximations for the OP and SEP are also attained which reveal insights into the effects of fading parameters and antenna correlation on the system’s performance. Furthermore, we prove that the correlation has no impact on the achievable diversity gain which is equal to the minimum of the sum of fading parameters between the two hops. Selected numerically evaluated results are presented showing an excellent agreement between the proposed analysis and equivalent Monte-Carlo simulations.
|
|
| 8. |
- Duong, Quang Trung, et al.
(författare)
-
Outage and Diversity of Cognitive Relaying Systems under Spectrum Sharing Environments in Nakagami-m Fading
- 2012
-
Ingår i: IEEE Communications Letters. - : IEEE. - 1089-7798 .- 1558-2558. ; 12:11
-
Tidskriftsartikel (refereegranskat)abstract
- In this letter, the outage performance of dualhop cooperative spectrum sharing systems with a direct link is investigated. A selection combining receiver is employed at the destination in order to combine the signals received from the decode-and-forward (DF) relay and from the source. Assuming independent non-identically distributed Nakagami-m fading channels, exact and asymptotic closed-form expressions are derived for the outage probability. Our results reveal that the diversity order of the considered system is solely determined by the fading severity parameters of the secondary network, being equal to min(m1, m2) + m0, where m0, m1, and m2 represent the fading severity parameters of the secondary nodes i.e., source→destination, source→relay, and relay→destination links, respectivel
|
|
| 9. |
- Duong, Quang Trung, et al.
(författare)
-
Outage probability of MIMO AF relay networks over Nakagami-m fading channels
- 2010
-
Ingår i: Electronics Letters. - : The Institution of Engineering and Technology. - 0013-5194 .- 1350-911X. ; 46:17
-
Tidskriftsartikel (refereegranskat)abstract
- The outage probability (OP) of multiple-input multiple-output (MIMO) amplify-and-forward (AF) relay networks using orthogonal space-time block code is investigated. In particular, a closed-form tight lower bound expression for the OP over independently but not necessarily identically distributed Nakagami-m fading channels is derived. Moreover, an asymptotic approximation for OP which reveals the coding and diversity gains is presented. The analytical expressions are validated by Monte-Carlo simulations.
|
|
| 10. |
- Duong, Quang Trung, et al.
(författare)
-
Performance Analysis of Amplify-and-Forward MIMO Relay Networks with Transmit Antenna Selection over Nakagami-m Channels
- 2010
-
Konferensbidrag (refereegranskat)abstract
- We analyze the performance of amplify-and-forward (AF) multiple-input multiple-output (MIMO) cooperative networks over independent but not identically distributed Nakagami-$m$ fading channels. Specifically, we consider an AF MIMO relay network where the source deploys the transmit antenna selection scheme to communicate with the destination through the help of a relay. We derive closed-form approximations for outage probability (OP) and symbol error probability (SEP). Moreover, asymptotically tight approximations for OP and SEP have been obtained to facilitate insights on how fading parameters affect the performance. Our analytical results are verified by Monte-Carlo simulations for respective scenarios.
|
|
| 11. |
- Phan, Hoc, et al.
(författare)
-
Distributed orthogonal space–time block coding in wireless relay networks
- 2013
-
Ingår i: IET Communications. - : IET. - 1751-8628 .- 1751-8636. ; 7:16
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, the authors consider distributed orthogonal space–time block coding for relay-based channel state information-assisted amplify-and-forward networks. Specifically, they show that opportunistic relaying (OR) is an optimal solution in terms of instantaneous signal-to-noise ratio (SNR), that is, it provides the maximum instantaneous SNR under the constraint of fixed transmit power for the relays. In particular, instead of allocating the given transmit power to all relays, letting the best relay transmit with this power is an optimal solution for maximising the received SNR. To exhibit this benefit, Monte Carlo simulations are presented showing superior performance of the OR scheme compared to equal power allocation policy for the considered relay networks. For the considered optimal scenario, the authors further derive analytical expressions for the outage probability and symbol error rate (SER) over quasi-static independent, not necessarily identically distributed Nakagami-m fading channels. They further present asymptotically tight approximations for the outage probability and SER in the high SNR regime, rendering insights into the cooperative diversity behaviour. Finally, numerical results are provided to examine the effect of network parameters on the system performance of the considered network.
|
|
| 12. |
- Qi, Nan, et al.
(författare)
-
A Learning-Based Spectrum Access Stackelberg Game : Friendly Jammer-Assisted Communication Confrontation
- 2021
-
Ingår i: IEEE Transactions on Vehicular Technology. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0018-9545 .- 1939-9359. ; 70:1, s. 700-713
-
Tidskriftsartikel (refereegranskat)abstract
- Defensive and offensive capabilities are both significant in communication confrontation games. By exploiting the above two capabilities, a new confrontation mechanism in the spectrum domain between two opposing teams denoted as the blue team (BT) and red team (RT), is designed. The basic idea is that by sacrificing parts of ally performance to severely deteriorate the opponent side communications. Specifically, a friendly and smart jammer (assuming in the BT) is deployed to weaken opponent (i.e., members in the RT) communications without causing great damages to other BT members, while the smart RT members try to evade the jamming and alleviate mutual interference. The interactions among the friendly jammer and other nodes are modeled as a Stackelberg game, with each player seeking for their respective utility maximization. We prove that each sub-game is an exact potential game. To efficiently search for the equilibrium solutions, a parallel log-linear learning algorithm is proposed, based on which each user intelligently decides their spectrum access policies. Numerical results demonstrate that: 1) RT communications are effectively suppressed; meanwhile, mutual interference among ally BT communication pairs is significantly alleviated; 2) the proposed algorithm achieves a close-to-optimal solution; 3) compared with the current state of solutions, i.e., random selection, stochastic learning automata, our algorithm performs better in terms of both utility and convergence.
|
|
| 13. |
- Qi, Nan, et al.
(författare)
-
Efficient Coded Cooperative Networks With Energy Harvesting and Transferring
- 2017
-
Ingår i: IEEE Transactions on Wireless Communications. - : Institute of Electrical and Electronics Engineers (IEEE). - 1536-1276 .- 1558-2248. ; 16:10, s. 6335-6349
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, a multi-user multi-relay network with integrated energy harvesting and transferring (IEHT) strategy is studied. In our system, a simultaneous two-level cooperation, i.e., information-and energy-level cooperation is conducted for uplink data transmissions (from the users to a destination). Specifically, network coding is employed at the relays to facilitate the information-level cooperation; meanwhile, ET is adopted to share the harvested energy among the users for the energy-level cooperation. For generality purposes, the Nakagami-m fading channels that are independent but not necessarily identically distributed (i.n.i.d.)are considered. The problem of energy efficiency maximization under constraints of the energy causality and a predefined outage probability threshold is formulated and shown to be non-convex. By exploiting fractional and geometric programming, a convex form-based iterative algorithm is developed to solve the problem efficiently. Close-to-optimal power allocation and energy cooperation policies across consecutive transmissions are found. Moreover, the effects of relay locations, wireless energy transmission efficiency, battery capacity as well as the existence of direct links are investigated. The performance comparison with the current state of solutions demonstrates that the proposed policies can manage the harvested energy more efficiently.
|
|
| 14. |
- Qi, Nan, et al.
(författare)
-
Energy-Efficient Cooperative Network Coding With Joint Relay Scheduling and Power Allocation
- 2016
-
Ingår i: IEEE Transactions on Communications. - : IEEE. - 0090-6778 .- 1558-0857. ; 64:11, s. 4506-4519
-
Tidskriftsartikel (refereegranskat)abstract
- The energy efficiency (EE) of a multi-user multi-relay system with the maximum diversity network coding (MDNC) is studied. We explicitly find the connection among the outage probability, energy consumption, and EE, and formulate the maximizing EE problem under the outage probability constraint. Relay scheduling (RS) and power allocation (PA) are applied to schedule the relay states (transmitting, sleeping, and so on) and optimize the transmitting power under the practical channel and power consumption models. Since the optimization problem is NP hard, to reduce computational complexity, the outage probability is first tightly approximated to a log-convex form. Furthermore, the EE is converted into a subtractive form based on the fractional programming. Then, a convex mixed-integer nonlinear problem is eventually obtained. With a generalized outer approximation algorithm, RS and PA are solved in an iterative manner. The Pareto-optimal curves between the EE and the target outage probability show the EE gains from PA and RS. Moreover, by comparing with the no network coding (NoNC) scenario, we conclude that with the same number of relays, MDNC can lead to EE gains. However, if RS is implemented, NoNC can outperform MDNC in terms of the EE when more relays are needed in the MDNC scheme.
|
|
| 15. |
- Qi, Nan, et al.
(författare)
-
Energy Efficient Two-Tier Network-Coded Relaying Systems Considering Processing Energy Costs
- 2019
-
Ingår i: IEEE Transactions on Vehicular Technology. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0018-9545 .- 1939-9359. ; 68:1, s. 999-1003
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, a two-tier network coding (TNC) scheme is proposed for the multi-user multi-relay transmission scenarios. Specifically, TNC is conducted at each individual relay, where two groups of source messages are combined into one network codeword that is forwarded to dual destinations. Finally, two groups of source messages are jointly recovered from different network codewords at the destinations. Both analytical and simulation results demonstrate that the proposed scheme outperforms the current state of art in terms of the energy efficiency (EE). In addition, the impacts of multiple parameters, including the number of users, SNR and relay locations on the average EE have been demonstrated, which provide valuable insights for the system designs of future wireless networks.
|
|
| 16. |
- Qi, Nan, et al.
(författare)
-
Traffic-Aware Two-Stage Queueing Communication Networks : Queue Analysis and Energy Saving
- 2020
-
Ingår i: IEEE Transactions on Communications. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0090-6778 .- 1558-0857. ; 68:8, s. 4919-4932
-
Tidskriftsartikel (refereegranskat)abstract
- To boost energy saving for the general delay-tolerant IoT networks, a two-stage, and single-relay queueing communication scheme is investigated. Concretely, a traffic-aware N-threshold and gated-service policy are applied at the relay. As two fundamental and significant performance metrics, the mean waiting time and long-term expected power consumption are explicitly derived and related with the queueing and service parameters, such as packet arrival rate, service threshold and channel statistics. Besides, we take into account the electrical circuit energy consumptions when the relay server and access point (AP) are in different modes and energy costs for mode transitions, whereby the power consumption model is more practical. The expected power minimization problem under the mean waiting time constraint is formulated. Tight closed-form bounds are adopted to obtain tractable analytical formulae with less computational complexity. The optimal energy-saving service threshold that can flexibly adjust to packet arrival rate is determined. In addition, numerical results reveal that: 1) sacrificing the mean waiting time not necessarily facilitates power savings; 2) a higher arrival rate leads to a greater optimal service threshold; and 3) our policy performs better than the current state-of-the-art.
|
|
