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Sökning: WFRF:(Duong Quang Trung)

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1.
  • Duong, Trung Quang, et al. (författare)
  • Cognitive Cooperative Networks in Dual-Hop Asymmetric Fading Channels
  • 2013
  • Ingår i: 2013 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM). - 2334-0983 .- 2576-6813. - 9781479913534 ; , s. 955-961
  • Konferensbidrag (refereegranskat)abstract
    • Previous works on cognitive relay networks (CRNs) considered only symmetric fading channels. However, in practical wireless propagation scenarios, it is likely that the channels of the secondary user (SU) and primary user (PU) may undergo different fading characteristics. In this paper, we assume that the channels of the secondary network (SU-source -> SU-relay -> SU-destination) are subject to Rician fading, whereas the channels of the link from the SU to the PU experience Rayleigh fading. Based on this framework, the end-to-end outage probability (OP) of CRNs is investigated for two different relaying schemes: i) in the absence of the direct link with decode-and-forward (DF) protocol and ii) in the presence of the direct link with incremental DF protocol. In particular, we derive both exact and asymptotic OP expressions for the considered CRNs. Our analysis reveals important insights into the impact of fading parameters on the CRN performance under distinct fading distributions.
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2.
  • Al-Qahtani, Fawaz S., et al. (författare)
  • Performance Analysis of Dual-Hop AF Systems with Interference in Nakagami-m Fading Channels
  • 2011
  • Ingår i: IEEE Signal Processing Letters. - : IEEE. - 1070-9908. ; 18:8, s. 454-457
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, we investigate the performance of dual-hop channel state information-assisted amplify-and-forward relaying systems over Nakagami-m fading channels in the presence of multiple interferers at the relay. Assuming integer fading parameter m, we derive closed-form expressions for the exact outage probability and accurate approximation for symbol error rate of the system. Furthermore, we look into the asymptotical high signal to noise ratio regime, and characterize the diversity order achieved by the system. All the analytical results are validated via Monte Carlo simulations.
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3.
  • Al-Qahtani, Fawaz S., et al. (författare)
  • Selection Decode-and-Forward Relay Networks with Rectangular QAM in Nakagami-m Fading Channels
  • 2010
  • Konferensbidrag (refereegranskat)abstract
    • In this paper, we investigate the average symbol error probability (SEP) of fixed decode-and-forward relay networks over independent but not identically distributed Nakagami-m fading channels. We have derived closed form expression of SEP for general rectangular quadrature amplitude modulation (QAM) under relay selection scheme where only the best relay forwards message from the source to the destination. The expressions are in terms of hypergeometric series which can be efficiently numerically evaluated. The numerical results are validated with Monte-Carlo simulations.
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4.
  • Bao, Vo Nguyen Quoc, et al. (författare)
  • Cognitive Amplify-and-Forward Relaying with Best Relay Selection in Non-Identical Rayleigh Fading
  • 2013
  • Ingår i: IEEE Communications Letters. - : IEEE. - 1089-7798 .- 1558-2558. ; 17:3, s. 475-478
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper investigates several important performance metrics of cognitive amplify-and-forward (AF) relay networks with a best relay selection strategy and subject to nonidentical Rayleigh fading. In particular, assuming a spectrum sharing environment consists of one secondary user (SU) source,K SU relays, one SU destination, and one primary user (PU) receiver, closed-form expressions for the outage probability (OP), average symbol error probability (SEP), and ergodic capacity of the SU network are derived. The correctness of the proposed analysis is corroborated via Monte Carlo simulations and readily allows us to evaluate the impact of the key system parameters on the end-to-end performance. An asymptotic analysis is also carried out and reveals that the diversity gain is defined by the number of relays pertaining to the SU network (i.e., K), being therefore not affected by the interference power constraint of the PU network.
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5.
  • Bao, Vo Nguyen Quoc, et al. (författare)
  • Distributed Switch-and-Stay Combining in Cognitive Relay Networks under Spectrum Sharing Constraints
  • 2013
  • Ingår i: 2013 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM). - : IEEE Communications Society. - 9781479913534 ; , s. 1927-1932
  • Konferensbidrag (refereegranskat)abstract
    • Distributed switch-and-stay combining (DSSC) has been envisioned as an effective transmission technique to achieve spatial diversity in a distributed fashion, with low implementation complexity. In this paper, we take a step further to incorporate DSSC into spectrum-limited environment, where the operating nodes have to share the frequency radio spectrum with licensed users. In particular, by deploying DSSC scheme in cognitive radio networks, we have shown that the low transmit power at unlicensed users, inflicted by the peak interference power constraint at licensed users, can be alleviated. We present closed-form expressions for outage probability and spectral efficiency, enabling us to evaluate and optimize the considered network performance. Numerical and simulation results show that when the switching threshold is below the outage threshold the full diversity order can be guaranteed at the secondary networks.
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6.
  • Bao, Vo Nguyen Quoc, et al. (författare)
  • Effect of Imperfect Channel State Information on the Performance of Cognitive Multihop Relay Networks
  • 2013
  • Ingår i: 2013 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM). - 9781479913534 ; , s. 3458-3463
  • Konferensbidrag (refereegranskat)abstract
    • Cognitive relay technology has been envisioned as a promising transmission scheme to enhance the reliability and coverage of secondary networks. However, the performance of cognitive relay networks (CRNs) is limited by the lack of accurate channel state information (CSI). As such, this paper adequately addresses the impact of imperfect CSI on the performance of cognitive multihop networks by proposing a simple yet effective backoff control power method. In addition, novel exact and asymptotic expressions for outage probability and ergodic capacity over Rayleigh fading channels are also derived. These tractable analytical results reveal new insight into the design, e.g., the number of hops for secondary network, and optimization of cognitive multihop networks.
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7.
  • Bao, Vo Nguyen Quoc, et al. (författare)
  • Exact Outage Probability of Cognitive Underlay DF Relay Networks with Best Relay Selection
  • 2012
  • Ingår i: IEICE transactions on communications. - : IEICE. - 0916-8516 .- 1745-1345. ; E95-B:6, s. 2169-2173
  • Tidskriftsartikel (refereegranskat)abstract
    • In this letter, we address the performance analysis of underlay selective decode-and-forward (DF) relay networks in Rayleigh fading channels with non-necessarily identical fading parameters. In particular, a novel result on the outage probability of the considered system is presented. Monte Carlo simulations are performed to verify the correctness of our exact closed-form expression. Our proposed analysis can be adopted for various underlay spectrum sharing applications of cognitive DF relay networks.
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8.
  • Bao, Vo Nguyen Quoc, et al. (författare)
  • On the performance of cognitive underlay multihop networks with imperfect channel state information
  • 2013
  • Ingår i: IEEE Transactions on Communications. - : IEEE. - 0090-6778 .- 1558-0857. ; 61:12, s. 4864-4873
  • Tidskriftsartikel (refereegranskat)abstract
    • 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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9.
  • Bao, Vo Nguyen Quoc, et al. (författare)
  • Outage Analysis of Cognitive Multihop Networks under Interference Constraints
  • 2012
  • Ingår i: IEICE transactions on communications. - : IEICE. - 0916-8516 .- 1745-1345. ; E95-B:3
  • Tidskriftsartikel (refereegranskat)abstract
    • The closed-form expressions for outage probability, bit error rate, and ergodic capacity of spectrum sharing-based multi-hop decode-and-forward relay networks in non-identical Rayleigh fading channels are derived. Utilizing these precise and tractable analytical formulas, we can study the impact of key network parameters on the performance of cognitive multi-hop relay networks under interference constraints. The analytical expressions are verified by Monte-Carlo simulations.
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10.
  • Chen, Yuanfang, et al. (författare)
  • The scheme of mitigating the asymmetric links problem in wireless sensor networks
  • 2010
  • Konferensbidrag (refereegranskat)abstract
    • This paper investigates the radio irregularity (RI) phenomenon and its impact on communication performance in wireless sensor networks (WSNs). Based on the theoretical analysis, we find that the RI phenomenon induces the asymmetric links problem. According to this discovery, we propose a novel HCT (Hop-count Correction Tree) scheme to handle this problem. HCT utilizes graph theoretical method to get a search tree and correct the hop count error that appears in the adjacent nodes. Practical results obtained from testbed experiments demonstrate that this solution can greatly improve localization accuracy in the presence of RI
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11.
  • Chu, Thi My Chinh, et al. (författare)
  • Beamforming Transmission in Cognitive AF Relay Networks with Feedback Delay
  • 2013
  • Konferensbidrag (refereegranskat)abstract
    • In this paper, we investigate the effect of feedback delay on outage probability (OP) and symbol error rate (SER) of cognitive amplify-and-forward (AF) relay networks with beamforming transmission in Rayleigh fading environment. It is assumed that the secondary transmitter and the secondary receiver are equipped with multiple antennas, whereas the relay and the primary user comprise of a single antenna. Furthermore, in this system, the secondary users use the underlay scheme in which the secondary transmitter and the relay can coexist with the primary user as long as their interference caused to the primary receiver is below a predefined threshold. Through our analysis, numerical results are provided to show the level of degradation of cognitive AF relay systems in proportion to the degree of feedback delay. In addition, we also present the effect of the number of antennas at the secondary transceiver on the performance of the considered system.
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12.
  • Chu, Thi My Chinh, et al. (författare)
  • MRT/MRC for Cognitive AF Relay Networks under Feedback Delay and Channel Estimation Error
  • 2012
  • Konferensbidrag (refereegranskat)abstract
    • In this paper, we examine the performance of multiple-input multiple-output cognitive amplify-and-forward (AF) relay systems with maximum ratio transmission (MRT). In particular, closed-form expressions in terms of a tight upper bound for outage probability (OP) and symbol error rate (SER) of the system are derived when considering channel estimation error (CEE) and feedback delay (FD) in our analysis. Through our works, one can see the impact of FD and CEE on the system as well as the benefits of deploying multiple antennas at the transceivers utilizing the spatial diversity of an MRT system.
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13.
  • Chu, Thi My Chinh, et al. (författare)
  • On Optimal Channel Uses in Ultra-Reliable Short-Packet Relaying Communications
  • 2022
  • Ingår i: ICCE 2022 - 2022 IEEE 9th International Conference on Communications and Electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781665497442 ; , s. 13-17
  • Konferensbidrag (refereegranskat)abstract
    • To support ultra-reliable low latency communication (URLLC) services in fifth-generation mobile networks, short-packet transmission is essential. However, due to the limited packet size, errors cannot be reduced to arbitrarily low levels for a given coding rate as for conventional communication systems covered by the Shannon theory. In this paper, we consider URLLC in dual-hop decode-and-forward relaying networks where the channel in each hop varies fast. A simple but efficient optimization of the block lengths is performed to minimize the block error rate (BLER) of the proposed system. In particular, we deploy machine learning models using the linear regression and normalized method to determine the optimal fraction of channel uses for the transmission over each hop. Numerical results show that the BLER of the consider relaying system with optimal block lengths for each hop based on the machine learning model outperforms conventional relaying systems with equal block lengths. © 2022 IEEE.
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14.
  • Chu, Thi My Chinh, et al. (författare)
  • Outage Probability and Ergodic Capacity for MIMO-MRT Systems under Co-Channel Interference and Imperfect CSI
  • 2011
  • Konferensbidrag (refereegranskat)abstract
    • In this paper, we investigate the performance of multiple-input multiple-output (MIMO) systems deploying maximum ratio transmission (MRT). Our analysis takes into account not only imperfect channel estimation at the receiver and feedback delay at the transmitter, but also includes co-channel interference (CCI). In particular, we first derive the statistical properties of the signal-to-interference-plus-noise ratio (SINR). Next, we obtain a closed-form expression for outage probability and an approximation for capacity. Finally, we show the consistency between analytical results and Monte-Carlo simulations. Our results indicate that the system performance is improved considerably in proportion to the number of transceiver antennas. Conversely, the outage probability increases, and the capacity decreases significantly with the severity of channel estimation error, feedback delay, and CCIs.
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15.
  • Chu, Thi My Chinh, et al. (författare)
  • Performance analysis for multiple-input multiple output- maximum ratio transmission systems with channel estimation error, feedback delay and co-channel interference
  • 2013
  • Ingår i: IET Communications. - : IET. - 1751-8628 .- 1751-8636. ; 7:4, s. 279-285
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study, the authors analyse the impact of channel estimation error (CEE), feedback delay (FD), and co-channel interference (CCI) on the performance of multiple-input multiple-output (MIMO) systems deploying maximum ratio transmission (MRT). In particular, the authors derive closed-form expressions for the ergodic capacity and the symbol error rate (SER) as well as the outage probability (OP). In addition, to reveal the effect of CEE, FD and CCI on the MIMO-MRT system, the authors adopt more simplified and tractable formulas in terms of asymptotic expressions for the ergodic capacity, SER and OP. The analysis shows that the system performance is degraded considerably under imperfect transmission conditions such as CEE, FD and CCI. However, the authors can compensate part of this degradation by deploying MRT transmission with a large number of antennas at the transmitter and receiver. Finally, the selected examples exhibit consistency between analytical results and Monte Carlo simulations.
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16.
  • Du, Xu, et al. (författare)
  • Joint Replication Density and Rate Allocation Optimization for VoD Systems over Wireless Mesh Networks
  • 2013
  • Ingår i: IEEE transactions on circuits and systems for video technology (Print). - : IEEE. - 1051-8215 .- 1558-2205. ; 23:7, s. 1260-1273
  • Tidskriftsartikel (refereegranskat)abstract
    • Due to the limited resources and dynamically varying nature of wireless links, guaranteeing high quality demands for a large number of heterogeneous users is very challenging in video streaming over wireless networks. In this paper, we introduce a layered multiple description coding with an embedded forward error correction scheme (LMDC-FEC). The combination of layered MDC and FEC aims at coping with not only the diverse bandwidth and unreliability of wireless links but also the heterogeneous user devices. We further propose a joint replication density and rate allocation (RD-RA) optimization problem in the context of video on-demand systems (VoDs) over wireless mesh networks (WMNs), and employ a genetic algorithms based approach to solve the optimization problem. Our objective is to elaborately distribute proper replication density for each video segment and allocate optimal bit rate to each layer of each segment in order to gain high userperceived quality (UPQ) with small consumption of storage resource. By this method, both optimal replication densities and rate allocations are found in accordance with the access rate of segments, the diverse loss characteristics of descriptions in each segment, and the rate–distortion relationship of segments, so as to thoroughly optimize UPQ and storage resource consumption. Simulation results demonstrate that our proposed method significantly enhances the streaming performance of VoDs over WMNs.
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17.
  • Duong, Quang Trung, et al. (författare)
  • Adaptive Transmission Scheme for Wireless Cooperative Communications
  • 2009
  • Konferensbidrag (refereegranskat)abstract
    • An adaptive transmission scheme for cooperative communications is proposed in this paper. Communication protocols with amplify-and-forward relays based on the distributed-Alamouti space-time code (achieving spatial diversity gain) and cooperative spatial multiplexing (C-SM) (pertaining spatial multiplexing gain) are considered. Specifically, under a fix transmission rate, we use adaptively the cooperative diversity (C-DIV) and C-SM according to channel conditions. With this strategy, either C-DIV with higher order modulation or C-SM with lower order modulation can be properly selected to enhance the error rate performance. The proposed adaptive protocol is shown to provide superior performance compared to C-DIV and C-SM.
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18.
  • 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.
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19.
  • Duong, Quang Trung, et al. (författare)
  • Average Sum-Rate of Distributed Alamouti Space--Time Scheme in Two-Way Amplify-and-Forward Relay Networks
  • 2010
  • Konferensbidrag (refereegranskat)abstract
    • In this paper, we propose a distributed Alamouti space-time code (DASTC) for two-way relay networks employing a single amplify-and-forward (AF) relay. We first derive closed-form expressions for the approximated average sum-rate of the proposed DASTC scheme. Our analysis is validated by a comparison against the results of Monte-Carlo simulations. Numerical results verify the effectiveness of our proposed scheme over the conventional DASTC with one-way communication.
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20.
  • Duong, Quang Trung, et al. (författare)
  • Beamforming in Two-Way Fixed Gain Amplify-and-Forward Relay Systems with CCI
  • 2012
  • Konferensbidrag (refereegranskat)abstract
    • We analyze the outage performance of a two-way fixed gain amplify-and-forward (AF) relay system with beamforming, arbitrary antenna correlation, and co-channel interference (CCI). Assuming CCI at the relay, we derive the exact individual user outage probability in closed-form. Additionally, while neglecting CCI, we also investigate the system outage probability of the considered network, which is declared if any of the two users is in transmission outage. Our results indicate that the position of the relay in this system plays an important role in determining the user as well as the system outage probability via such parameters as signal-to-noise imbalance, antenna configuration, spatial correlation, and CCI power. To render further insights into the effect of antenna correlation and CCI on the diversity and array gains, an asymptotic expression which tightly converges to exact results is also derived.
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21.
  • Duong, Quang Trung, et al. (författare)
  • Cognitive Amplify-and-Forward Relay Networks over Nakagami-m Fading
  • 2012
  • Ingår i: IEEE Transactions on Vehicular Technology. - : IEEE. - 0018-9545 .- 1939-9359. ; 61:5, s. 2368-2374
  • Tidskriftsartikel (refereegranskat)abstract
    • 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 for determining the transmit powers of the secondary network. Specifically, the transmit power conditions of the proposed spectrum sharing network are governed by either: (i) the combined power constraint of the interference on the primary network and maximum transmission power at the secondary network; or (ii) 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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22.
  • Duong, Quang Trung, et al. (författare)
  • Cognitive Relay Networks With Multiple Primary Transceivers Under Spectrum-Sharing
  • 2012
  • Ingår i: IEEE Signal Processing Letters. - : IEEE. - 1070-9908 .- 1558-2361. ; 19:11, s. 741-744
  • Tidskriftsartikel (refereegranskat)abstract
    • We examine the impact of multiple primary transmitters and receivers (PU-TxRx) on the outage performance of cognitive decode-and-forward relay networks. In such a joint relaying/spectrum-sharing arrangement, we address fundamental questions concerning three key power constraints: 1) maximum transmit power at the secondary transmitter (SU-Tx), 2) peak interference power at the primary receivers (PU-Rx), and 3) interference power at SU-Rx caused by the primary transmitter (PU-Tx). Our answers to these are given in new analytical expressions for the exact and asymptotic outage probability of the secondary relay network. Based on our asymptotic expressions, important design insights into the impact of primary transceivers on the performance of cognitive relay networks is reached. We have shown that zero diversity order is attained when the peak interference power at the PU-Rx is independent of the maximum transmit power at the SU-TX.
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23.
  • Duong, Quang Trung, et al. (författare)
  • Cooperative spectrum sharing networks with AF relay and selection diversity
  • 2011
  • Ingår i: Electronics Letters. - : Institution of Engineering and Technology - IET. - 0013-5194 .- 1350-911X. ; 47:20, s. 1149-1151
  • Tidskriftsartikel (refereegranskat)abstract
    • The exact outage probability (OP) of cognitive dual-hop relay networks equipped with a single amplify-and-forward (AF) relay and a selection combining receiver at the destination is derived under spectrum sharing constraint on a primary user. The tractable closed-form OP readily enables evaluation of system performance, which indicates the significance of using a relay in cognitive radio networks with a spectrum sharing approach. The proposed analysis is validated by numerical examples.
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24.
  • Duong, Quang Trung, et al. (författare)
  • Cooperative Wireless Communications with Unequal Error Protection and Fixed Decode-And-Forward Relays
  • 2010
  • Konferensbidrag (refereegranskat)abstract
    • In this paper, we examine an unequal error protection (UEP) scheme for wireless imaging that is based on utilizing the distributed diversity offered by decode-and-forward (DF) networks. Specifically, the data stream after source encoding is divided into high and low priority sub-streams depending on their importance for image reconstruction. A relay-selection combining (R-SC) scheme is exploited for high priority image data to achieve high reliability while cooperative spatial multiplexing is employed to low priority image data to support high spectral efficiency. In this work, we specifically take into account the setting that relays may forward erroneously detected signals to the destination when cooperating with fixed DF. In this context, the analytical and numerical results validate that R-SC outperforms other relaying protocols in terms of average symbol error probability while the considered UEP approach offers the highest spectral efficiency among the examined relaying schemes.
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25.
  • Duong, Quang Trung, et al. (författare)
  • Cross-Layer Design for Integrated Mobile Multimedia Network with Strict Priority Traffic
  • 2010
  • Konferensbidrag (refereegranskat)abstract
    • In mobile multimedia networks, different traffic classes require various levels of quality of service (QoS). In this paper, we propose a cross-layer design to provide diverse QoS provisions for integrated realtime/non-realtime traffic by jointly taking into account the physical layer, data link layer, and application layer. Specifically, at the physical layer, adaptive modulation and coding (AMC) is employed to cope with the time-varying nature of fading channels whereas impairments due to queuing effects are considered at the data link layer. At the application layer, realtime and non-realtime traffic are classified into high and low priority classes, respectively, with strict priority levels. The cross-layer scheme is characterized as a discrete Markov modulated Poisson process. Solving the steady state probability of this Markov model readily enables us to investigate several important performance metrics such as packet drop rate due to buffer overflow and packet error rate due to transmission errors and network impairments. Our proposed cross-layer design is verified by comparing the analytical results with Monte-Carlo simulations. Furthermore, it has been shown that the proposed cross-layer design can flexibly guarantee QoS requirements for each traffic class.
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26.
  • Duong, Quang Trung, et al. (författare)
  • Cross-Layer Design for MRT Systems with Channel Estimation Error and Feedback Delay
  • 2011
  • Ingår i: Wireless personal communications. - : Springer. - 0929-6212 .- 1572-834X. ; 58:4, s. 681-694
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, we analyze the effect of channel estimation error and delayed feedback on the performance of a cross-layer scheme combining adaptive modulation for maximum ratio transmission (MRT) at the physical layer and truncated automatic repeat request (T-ARQ) at the link layer. The cross-layer attempts to maximize the spectral efficiency under predetermined quality of service requirements, namely, delay and packet-loss constraints. In particular, we derive closed-form expressions for the average packet error rate, average achievable spectral efficiency, and the outage probability, hence, enabling to evaluate the performance of the cross-layer scheme in the presence of imperfect channel estimation at the receiver and delayed feedback path between the receiver and transmitter. The final expressions are given in terms of the minimum and maximum number of transceiver antennas as well as the channel estimation error and feedback delay parameters. We further show that with a small amount of channel estimation error and/or feedback delay the system performance is severely degraded. Specifically, numerical results demonstrate that with channel estimation error and feedback delay the performance of the cross-layer scheme is even worse than that of T-ARQ only. We also observe an irreducible outage probability floor appearing in the high signal-to-noise regime.
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27.
  • Duong, Quang Trung, et al. (författare)
  • Cross-Layer Design for Packet Data Transmission in Maximum Ratio Transmission Systems with Imperfect CSI and Co-Channel Interference
  • 2012
  • Ingår i: Using Cross-Layer Techniques for Communication Systems. - : IGI. - 9781466609600 ; , s. 376-399
  • Bokkapitel (refereegranskat)abstract
    • This chapter will therefore present some new results for the cross-layer design for packet data transmission applied to co-located MIMO with maximum ratio transmission. In this context, closed-form expressions for the average packet error rate, average achievable spectral efficiency, and outage probability are derived. This enables one to evaluate the performance of the cross-layer design under predetermined delay and packet loss constraints. Some important results in the high Signal-to-Noise Ratio (SNR) regime are also provided, revealing insights on how system and channel parameters affect system performance. More importantly, a mathematical analysis is proved to be a powerful tool to investigate the impact of practical issues such as channel estimation error, feedback delay, antenna correlation, and rank-deficient MIMO channel matrix, on the performance of cross-layer design.
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28.
  • Duong, Quang Trung, et al. (författare)
  • Distributed Space-Time Block Codes with Amicable Orthogonal Designs
  • 2008
  • Konferensbidrag (refereegranskat)abstract
    • In this paper, we generalize the construction of distributed space–time block codes (DSTBCs) using amicable orthogonal designs which are originally applied to co-located multiple-antenna systems. We also derive the closed-form expression of average symbol error probability (SEP). The result is obtained in the form of single finite-range integral whose integrand contains only the trigonometric functions. Using the asymptotic (high signal-to-noise ratio) SEP formulas we show that the orthogonal DSTBCs achieve full diversity order. We also perform Monte-Carlo simulation to validate the analysis.
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29.
  • Duong, Quang Trung, et al. (författare)
  • Distributed Space-Time Coding in Two-Way Fixed Gain Relay Networks over Nakagami-m Fading
  • 2012
  • Ingår i: Proceedings of the IEEE International Conference on Communicatons (ICC). - Ottawa : IEEE. - 9781457720512 - 9781457720529 ; , s. 3521-3525
  • Konferensbidrag (refereegranskat)abstract
    • The distributed Alamouti space-time code in two-way fixed gain amplify-and-forward (AF) relay is proposed in this paper. In particular, closed-form expressions for approximated ergodic sum-rate and exact pairwise error probability (PWEP) are derived for Nakagami-m fading channels. To reveal further insights into array and diversity gains, an asymptotic PWEP is also obtained. Finally, numerical results are provided to corroborate the proposed theoretical analysis.
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30.
  • Duong, Quang Trung, et al. (författare)
  • Effect of primary network on performance of spectrum sharing AF relaying
  • 2012
  • Ingår i: Electronics Letters. - : IET. - 0013-5194 .- 1350-911X. ; 48:1, s. 25-U95
  • Tidskriftsartikel (refereegranskat)abstract
    • 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.
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31.
  • Duong, Quang Trung, et al. (författare)
  • End-to-End Performance of Randomized Distributed Space-Time Codes
  • 2010
  • Konferensbidrag (refereegranskat)abstract
    • The exact closed-form expressions for symbol error probability and outage probability of randomized distributed space-time codes (RDSTC) under Rayleigh fading are derived. The diversity gain derived in the literature uses the Chernoff bound which may not be achievable in general. Utilizing the exact expression, the achievable diversity gain of RDSTCs is validated. The closed-form expressions are verified by Monte-Carlo simulations.
  •  
32.
  • Duong, Quang Trung, et al. (författare)
  • Ergodic Capacity of Cooperative Networks Using Adaptive Transmission and Selection Combining
  • 2009
  • Konferensbidrag (refereegranskat)abstract
    • Closed-form expressions for channel capacity of repetition-based cooperative networks under adaptive transmission with selection combining are presented under the assumption of independent Rayleigh fading. Specifically, three different adaptive techniques are investigated: optimal simultaneous power and rate adaptation (OPRA), constant power with optimal rate adaptation (OPA) and channel inversion with fixed rate (TIFR). Among them, for an arbitrary number of relays, TIFR gives the worst channel capacity; OPRA gives the best channel capacity and ORA has a channel capacity quality in between the others. The analysis results, based on the upper and lower bound of the end-to-end SNR, agree very well with the simulated results and definitely show the impact of selection combining on the calculated channel capacity per unit bandwidth
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33.
  • Duong, Quang Trung, et al. (författare)
  • Exact Average Symbol Error Rate of Cooperative Spatial Multiplexing in Composite Channels
  • 2008
  • Konferensbidrag (refereegranskat)abstract
    • Performance of cooperative spatial multiplexing systems over composite channels is presented. In particular, we derive the exact closed-form average symbol error rate (SER) expressions for cooperative spatial multiplexing systems with linear equalization receiver (e.g., Zero-Forcing) and M-ary modulation scheme in the composite channel of log-normal shadowing and Rayleigh fading. Using the Gauss-Hermite quadrature integration, the average SER is expressed in the forms of Appell hypergeometric function. Applying the series representation of Appell hypergeometric function, we derive a very tight approximation for the average SER. We also perform Monte-Carlo simulations to validate our analysis.
  •  
34.
  • Duong, Quang Trung (författare)
  • Exact Closed-Form Expression for Average Symbol Error Rate of MIMO-MRC Systems
  • 2008
  • Konferensbidrag (refereegranskat)abstract
    • In this paper, we derive closed-form expressions for exact average symbol error rate (SER) of multiple-input multiple-output (MIMO)-maximum ratio combining (MRC) systems with M-ary modulations. We obtain the tractable compact closed-form expressions for the average SER in terms of the Gauss and Appell hypergeometric functions which are provided as library functions in common mathematical softwares such as MAPLE and MATHEMATICA. The analysis is validated by comparing with Monte-Carlo simulations and we further show that our general SER expressions reduce to the previous known results for binary signals (M=2) as a special case. Applying the series representation of the Gauss and Appell hypergeometric function, we derive a very tight approximation for the average SER
  •  
35.
  • Duong, Quang Trung, et al. (författare)
  • Exact outage probability of cognitive AF relaying with underlay spectrum sharing
  • 2011
  • Ingår i: Electronics Letters. - : Institution of Engineering and Technology -IET. - 0013-5194 .- 1350-911X. ; 47:17, s. 1001-1002
  • Tidskriftsartikel (refereegranskat)abstract
    • The exact closed-form expression for the outage probability (OP) of cognitive radio dual-hop amplify-and-forward (AF) relay networks is derived. The tractable expression of the OP, given in the form of elementary functions, readily enables evaluating the effect of primary users on the secondary system performance. It has been shown that the use of AF relaying significantly improves the performance of cognitive radio networks compared to its direct transmission counterpart.
  •  
36.
  • Duong, Quang Trung, et al. (författare)
  • Hybrid Decode-Amplify-Forward Cooperative Communications with Multiple Relays
  • 2009
  • Konferensbidrag (refereegranskat)abstract
    • In this paper, we investigate the performance gain of hybrid decode-amplify-forward (HDAF) relay protocol over the two conventional ones: the adaptive decode-forward (ADF) and amplify-forward (AF) in dual-hop multiple-relay networks. We analyze the performance gain in terms of the symbol error probability (SEP) in the high signal-to-noise ratio (SNR) regime. Similarly as in the single relay case [1], under a specific modulation scheme, these gains only depend on the ratio of channel mean power between the first-hop and second-hop transmission. In particular, we show that the HDAF protocol obtains a large gain, medium gain, and small gain over ADF, AF as the relays are placed close to the destination, half-way between the source and destination (symmetric case), and nearby the source, respectively. In contrast to the single-relay case in which the HDAF scheme has no benefit compared to ADF and AF as the relay is located close to the source [1], HDAF still achieves a small gain with multiple relays. Interestingly, we further show that for all cases the performance gains are saturated as the number of relays is large.
  •  
37.
  • 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.
  •  
38.
  • Duong, Quang Trung, et al. (författare)
  • Multi-Keyhole Effect in MIMO AF Relay Downlink Transmission with Space-Time Block Codes
  • 2011
  • Konferensbidrag (refereegranskat)abstract
    • Multi-keyhole bridges the gap between single keyhole and full-scattering multiple-input multiple-output (MIMO) channels. In this paper, we therefore investigate the multi-keyhole effect on the MIMO amplify-and-forward (AF) relay downlink transmission with orthogonal space-time block codes. In particular, we derive the analytical symbol error rate (SER) expression for the considered system with arbitrary number of keyholes. Moreover, SER approximations in the high SNR regime for several important special scenarios of multi-keyhole channels are further derived. These asymptotic results provide important insights into the impact of system's parameters on the SER performance. Our analysis is confirmed by comparing with Monte-Carlo simulations.
  •  
39.
  • Duong, Quang Trung (författare)
  • On Cooperative Communications and Its Application to Mobile Multimedia
  • 2010
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • With the rapid growth of multimedia services, future generations of wireless communications require higher data rates and a more reliable transmission link while keeping satisfactory quality of service. In this respect, multipleinput multiple-output (MIMO) antenna systems have been considered as an efficient approach to address these demands by offering significant multiplexing and diversity gains over single-antenna systems without increasing requirements on radio resources such as bandwidth and power. Although MIMO systems can unfold their huge benefit in cellular base stations, they may face limitations when it comes to their deployment in mobile handsets. In particular, the typically small-size of mobile handsets makes it impractical to deploy multiple antennas. To overcome this drawback, the concept of cooperative communications has recently been proposed and gained large interest in the research community. The key idea is to form a virtual MIMO antenna array by utilizing a third terminal, a so-called relay node, which assists the direct communication. After receiving the source’s message, the relay processes and forwards it to the destination. With this approach, the benefits of MIMO systems can be attained in a distributed fashion. Furthermore, cooperative communications can efficiently combat the severity of fading and shadowing effects through the assistance of relay terminals. It has been shown that using the relay can extend the coverage of wireless networks. In this thesis, we focus on the performance evaluation of such cooperative communication systems and their application to mobile multimedia. The thesis is divided into five parts. In particular, the first part proposes a hybrid decode-amplify-forward (HDAF) relaying protocol which can significantly improve the performance of cooperative communication systems compared to the two conventional schemes of decode-and-forward (DF) and amplify-and-forward (AF). It is interesting to see that the performance gain of HDAF over DF and AF strictly depends on the relative value of channel conditions between the two hops. The second part extends HDAF to the case of multiple relays. It is important to note that the gains are saturated as the number of relays tends to be a large value. This observation motivates us to use a small number of relays to reduce network overhead as well as system complexity while the obtained gains are still as much as in the large-number case. In the third part, we analyze the performance of DF relaying networks with best relay selection over Nakagami-m fading channels. Besides the diversity gain, we show that the spatial multiplexing gain can be achieved by cooperative communications. We analyze the performance of cooperative multiplexing systems in terms of symbol error rate and ergodic capacity over composite fading channels. Finally, in the fifth part, we exploit the benefit of both diversity and multiplexing gain by proposing an unequal error transmission scheme for mobile multimedia services using cooperative communications.
  •  
40.
  • Duong, Quang Trung, et al. (författare)
  • On the Ergodic Capacity of Cooperative Spatial Multiplexing Systems in Composite Channels
  • 2009
  • Konferensbidrag (refereegranskat)abstract
    • The ergodic capacity of cooperative spatial multiplexing systems over composite channels is presented. Specifically, we derive the exact closed-form expressions for ergodic capacity of cooperative spatial multiplexing systems with linear receiver in the composite channel of log-normal shadowing and Rayleigh fading. Using the Gauss-Hermite quadrature integration, the final analytical result of ergodic capacity is described in a closed-form expression. We also perform Monte-Carlo simulations to validate our analysis. Subsequently, we apply the obtained analytical expression to evaluate some representative scenarios regarding to spatial multiplexing gain in relay composite channels
  •  
41.
  • Duong, Quang Trung (författare)
  • On the Performance Analysis of Cooperative Communications with Practical Constraints
  • 2012
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • With the rapid development of multimedia services, wireless communication engineers may face a major challenge to meet the demand of higher data-rate communication over error-prone mobile radio channels. As a promising solution, the concept of cooperative communication, where a so-called relay node is formed to assist the direct link, has recently been applied to alleviate the severe pathloss and shadowing effects in wireless systems. In addition, without spending extra spectrum and power resources, multiple-input multiple-output (MIMO) antenna systems have been shown to provide an immense improvement in system performance compared to its single-antenna counterpart. As such, cooperative MIMO communication is essential for wireless and mobile networks because of its remarkable increase in spectral efficiency and reliability. Although the utilization of cooperative communication in MIMO systems has gained great attention in the literature, most of the research works have assumed perfect conditions. Inspired by the aforementioned discussion, this thesis takes a step further to investigate the performance of cooperative communications with practical constraints. The thesis provides a general framework for performance analysis of cooperative communications subject to several practical constraints such as antenna correlation, rank-deficiency of the channel matrix, co-channel interference, and interference-limited constraint of cognitive radio networks based on an underlay spectrum-sharing approach. The thesis is divided into six parts. The first part investigates the performance of orthogonal space-time block codes (OSTBCs) over MIMO relay networks in Nakagami-m fading channels under the antenna correlation effect. The second part extends the full-rank MIMO channel to the case of the MIMO channel matrix being of rank-deficiency. Several important findings on the impact of the single-keyhole effect (SKE) and double-keyhole effect (DKE) are observed for two types of amplifying mechanism at the relay, namely, linear and squaring approaches. An important observation corroborated by our studies is that for offering a tradeoff between performance and complexity, we should use the linear approach for SKE and the squaring approach for DKE. The third part generalizes the keyhole effect to multi-keyhole channels. The exact and asymptotic expressions for symbol error probability (SEP) are derived for some specific cases such as multi-keyhole MIMO/multiple-input single-output (MISO) channel. The fourth part proposes a distributed Alamouti space-time code for two-way fixed gain amplify-and-forward (AF) relaying. In particular, closed-form expressions for approximated ergodic sum-rate and exact pairwise error probability (PWEP) are derived for Nakagami-m fading channels. To reveal further insights into array and diversity gains, an asymptotic PWEP is also obtained. The fifth part analyzes the outage performance of a two-way fixed gain AF relay system with beamforming, arbitrary antenna correlation, and co-channel interference (CCI). Finally, the sixth part investigates the impact of interference power constraint on the performance of cognitive relay networks based on the spectrum-sharing approach.
  •  
42.
  • Duong, Quang Trung, et al. (författare)
  • On the Performance Gain of Hybrid Decode-Amplify-Forward Cooperative Communications
  • 2009
  • Ingår i: EURASIP Journal on Wireless Communications and Networking. - : Hindawi Publishing Corporation. - 1687-1472 .- 1687-1499. ; 2009
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, we investigate the performance of adaptive decode-forward (ADF), amplify-forward (AF), and hybrid decode-amplify-forward (HDAF) relaying protocol. In particular, we derive the closedform expression of symbol error probability (SEP) for these three relaying protocols. For the AF protocol, we derive a simpler and more tractable final result than previously published work [1]. Furthermore, analyzing the high signal-to-noise ratio (SNR) regime, we derive an asymptotically tight approximation for SEP. Especially, for the AF protocol, our SEP approximation is tighter than the result in [2]. The SEP approximation is used to assess an important aspect between the three different relaying protocols, i.e., the SEP performance gain of HADF over the two conventional relaying schemes ADF and AF. It is shown that the performance gain of HDAF over ADF and AF significantly depends on the relative value of channel conditions between source-to-relay and relay-to- estination link (relay channels). Interestingly, it is shown that the HDAF protocol has no benefit compare to the two others if the relay is located close to the source. In contrast, the performance gains of HDAF over the ADF and AF scheme are remarkably large as the relay moves nearby the destination. Specifically, the numerical results given as well as our analysis indicate that for QPSK modulation, HDAF outperforms ADF and AF with a performance improvement by 5 dB and 6 dB, respectively.
  •  
43.
  • Duong, Quang Trung, et al. (författare)
  • On the Performance of ROI-Based Image Transmission Using Cooperative Diversity
  • 2008
  • Konferensbidrag (refereegranskat)abstract
    • In this paper, we examine the spatial diversity of cooperative communications for image transmission without deploying multiple antennas at the transmitter. We propose a novel region of interest (ROI)-based scheme for image transmission over wireless cooperative/relay fading channels. By having the relay terminal assist the direct communications, we can increase the resilience for ROI against the error-prone fading channels. Our proposed scheme significantly improves the performance of ROI compared to the direct communications (no-cooperation) and conventional relay networks without performing any forward error correction. Although we focus on the adaptive decode-forward (ADF) relay protocol, our proposed scheme can be easily adopted to any other relaying protocol such as fixed decode-forward (FDF), amplify-forward (AF), hybrid decode-amplify-forward (HDAF), and distributed-Alamouti space--time coding. Simulation results show that under the the same total transmit power constraint our proposed scheme significant outperforms the conventional ones in terms of bit error rate (BER) and peak signal-to-noise ratio (PSNR).
  •  
44.
  • Duong, Quang Trung, et al. (författare)
  • On the Performance of Selection Decode-and-Forward Relay Networks over Nakagami-m Fading Channels
  • 2009
  • Ingår i: IEEE Communications Letters. - 1089-7798 .- 1558-2558. ; 13:3, s. 172-174
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, we present the performance of fixed decode-and-forward cooperative networks with relay selection over independent but not identically distributed Nakagamim fading channels, with integer values of the fading severity parameter m. Specifically, closed-form expressions for the symbol error probability and the outage probability are derived using the statistical characteristic of the signal-to-noise ratio. We also perform Monte-Carlo simulations to verify the analytical results
  •  
45.
  • Duong, Quang Trung, et al. (författare)
  • On the Performance of Two-Way Amplify-and-Forward Relay Networks
  • 2009
  • Ingår i: IEICE transactions on communications. - : IEICE. - 0916-8516 .- 1745-1345. ; E92-B:12, s. 3957-3959
  • Tidskriftsartikel (refereegranskat)abstract
    • The performance of two-way amplify-and-forward (AF) relay networks is presented. In particular, we derive exact closed-form expressions for symbol error rate (SER), average sum-rate, and outage probability of two-way AF relay systems in independent but not identically distributed (i.n.i.d.) Rayleigh fading channels. Our analysis is validated by a comparison against the results of Monte-Carlo simulations.
  •  
46.
  • Duong, Quang Trung, et al. (författare)
  • On The Symbol Error Probability of Distributed-Alamouti Scheme
  • 2009
  • Ingår i: Journal of Communications. - : Academy Publisher. - 1796-2021 .- 2374-4367. ; 4:7, s. 437-444
  • Tidskriftsartikel (refereegranskat)abstract
    • Taking into account the relay’s location, we analyze the maximum likelihood (ML) decoding performance ofdualhop relay network, in which two amplify-and-forward (AF) relays employ the Alamouti code in a distributed fashion. In particular, using the well-known moment generating function (MGF) approach we derive the closed-form expressions of the average symbol error probability (SEP) for M-ary phase-shift keying (M-PSK) when the relays are located nearby either the source or destination. The analytical result is obtained as a single integral with finite limits and the integrand composed solely of trigonometric functions. Assessing the asymptotic characteristic of SEP formulas in the high signal-to-noise ratio regime, we show that the distributed-Alamouti protocol achieves a full diversity order. We also perform the Monte-Carlo simulations to validate our analysis. In addition, based on the upper bound of SEP we propose an optimal power allocation between the first-hop (the source-to-relay link) and second-hop (the relay-to-destination link) transmission. We further show that as the two relays are located nearby the destination most of the total power should be allocated to the broadcasting phase (the first-hop transmission). When the two relays are placed close to the source, we propose an optimal transmission scheme which is a non-realtime processing, hence, can be applied for practical applications. It is shown that the optimal power allocation scheme outperforms the equal power scheme with a SEP performance improvement by 2-3 dB.
  •  
47.
  • Duong, Quang Trung, et al. (författare)
  • Opportunistic relaying for cognitive network with multiple primary users over Nakagami-m fading
  • 2013
  • Konferensbidrag (refereegranskat)abstract
    • The performance of cognitive spectrum sharing systems with opportunistic relay selection over Nakagami-m fading is analyzed in the presence of multiple primary users (PUs). In particular, we derive an exact closed-form expression for the outage probability (OP) of the considered cognitive relay systems under the joint impact of maximal transmit power Pt at secondary transmitter and peak interference power Ip at the primary user. Our general formulas cover several specific practical scenarios, e.g., where the maximal transmit power can be neglected compared to the peak interference power. In addition, a tractable expression for the asymptotic OP is also derived and reveals important insights into the system performance. We show that the number of PUs only affects the coding gain but not the diversity gain.
  •  
48.
  • 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.
  •  
49.
  • 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.
  •  
50.
  • 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
  •  
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