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  • 1. Bao, Vo Nguyen Quoc
    et al.
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Exact Outage Probability of Cognitive Underlay DF Relay Networks with Best Relay Selection2012In: IEICE transactions on communications, ISSN 0916-8516, E-ISSN 1745-1345, Vol. E95-B, no 6, p. 2169-2173Article in journal (Refereed)
    Abstract [en]

    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.

  • 2. Bao, Vo Nguyen Quoc
    et al.
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Outage Analysis of Cognitive Multihop Networks under Interference Constraints2012In: IEICE transactions on communications, ISSN 0916-8516, E-ISSN 1745-1345, Vol. E95-B, no 3Article in journal (Refereed)
    Abstract [en]

    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.

  • 3. Bao, Vo Nguyen Quoc
    et al.
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    da Costa, Daniel Benevides
    Alexandropoulos, George C.
    Nallanathan, A.
    Cognitive Amplify-and-Forward Relaying with Best Relay Selection in Non-Identical Rayleigh Fading2013In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 17, no 3, p. 475-478Article in journal (Refereed)
    Abstract [en]

    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.

  • 4. Bao, Vo Nguyen Quoc
    et al.
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Tellambura, Chintha
    On the performance of cognitive underlay multihop networks with imperfect channel state information2013In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 61, no 12, p. 4864-4873Article in journal (Refereed)
    Abstract [en]

    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.

  • 5. Bao, Vo Nguyen Quoc
    et al.
    Duong, Trung Quang
    Blekinge Institute of Technology, School of Computing.
    Nallanathan, Arugumam
    Karagiannidis, George K.
    Distributed Switch-and-Stay Combining in Cognitive Relay Networks under Spectrum Sharing Constraints2013In: 2013 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM), IEEE Communications Society, 2013, p. 1927-1932Conference paper (Refereed)
    Abstract [en]

    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.

  • 6. Bao, Vo Nguyen Quoc
    et al.
    Duong, Trung Quang
    Blekinge Institute of Technology, School of Computing.
    Nallanathan, Arugumam
    Tellambura, Chintha
    Effect of Imperfect Channel State Information on the Performance of Cognitive Multihop Relay Networks2013In: 2013 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM), 2013, p. 3458-3463Conference paper (Refereed)
    Abstract [en]

    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.

  • 7. Chu, Thi My Chinh
    et al.
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, School of Computing.
    MRT/MRC for Cognitive AF Relay Networks under Feedback Delay and Channel Estimation Error2012Conference paper (Refereed)
    Abstract [en]

    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.

  • 8.
    Chu, Thi My Chinh
    et al.
    Blekinge Institute of Technology, School of Computing.
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, School of Computing.
    Performance analysis for multiple-input multiple output- maximum ratio transmission systems with channel estimation error, feedback delay and co-channel interference2013In: IET Communications, ISSN 1751-8628, Vol. 7, no 4, p. 279-285Article in journal (Refereed)
    Abstract [en]

    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.

  • 9.
    Chu, Thi My Chinh
    et al.
    Blekinge Institute of Technology, School of Computing.
    Phan, Hoc
    Blekinge Institute of Technology, School of Computing.
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Elkashlan, Maged
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, School of Computing.
    Beamforming Transmission in Cognitive AF Relay Networks with Feedback Delay2013Conference paper (Refereed)
    Abstract [en]

    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.

  • 10. Du, Xu
    et al.
    Vo, Nguyen-Son
    Cheng, Wenqing
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Shu, Lei
    Joint Replication Density and Rate Allocation Optimization for VoD Systems over Wireless Mesh Networks2013In: IEEE transactions on circuits and systems for video technology (Print), ISSN 1051-8215, E-ISSN 1558-2205, Vol. 23, no 7, p. 1260-1273Article in journal (Refereed)
    Abstract [en]

    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.

  • 11.
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    On the Performance Analysis of Cooperative Communications with Practical Constraints2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    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.

  • 12.
    Duong, Quang Trung
    et al.
    Blekinge Institute of Technology, School of Computing.
    Bao, Vo Nguyen Quoc
    Tran, Hung
    Blekinge Institute of Technology, School of Computing.
    Alexandropoulos, George C.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, School of Computing.
    Effect of primary network on performance of spectrum sharing AF relaying2012In: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 48, no 1, p. 25-U95Article in journal (Refereed)
    Abstract [en]

    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.

  • 13.
    Duong, Quang Trung
    et al.
    Blekinge Institute of Technology, School of Computing.
    Costa, Daniel Benevides da
    Elkashlan, Maged
    Bao, Vo Nguyen Quoc
    Cognitive Amplify-and-Forward Relay Networks over Nakagami-m Fading2012In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 61, no 5, p. 2368-2374Article in journal (Refereed)
    Abstract [en]

    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.

  • 14.
    Duong, Quang Trung
    et al.
    Blekinge Institute of Technology, School of Computing.
    da Costa, Daniel Benevides
    Tsiftsis, Theodoros A.
    Zhong, Caijun
    Nallanathan, Arumugam
    Outage and Diversity of Cognitive Relaying Systems under Spectrum Sharing Environments in Nakagami-m Fading2012In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 12, no 11Article in journal (Refereed)
    Abstract [en]

    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

  • 15.
    Duong, Quang Trung
    et al.
    Blekinge Institute of Technology, School of Computing.
    Kim, Kyeongjin
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, School of Computing.
    Tellambura, Chintha
    Opportunistic relaying for cognitive network with multiple primary users over Nakagami-m fading2013Conference paper (Refereed)
    Abstract [en]

    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.

  • 16.
    Duong, Quang Trung
    et al.
    Blekinge Institute of Technology, School of Computing.
    Ngo, Hien Quoc
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, School of Computing.
    Nallanathan, Arumugam
    Distributed Space-Time Coding in Two-Way Fixed Gain Relay Networks over Nakagami-m Fading2012Conference paper (Refereed)
    Abstract [en]

    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.

  • 17.
    Duong, Quang Trung
    et al.
    Blekinge Institute of Technology, School of Computing.
    Shu, Lei
    Chen, Min
    Vo Nguyen Quoc, Bao
    Dac Binh, Ha
    Performance analysis of cooperative spatial multiplexing networks with AF/DF relaying and linear receiver over Rayleigh fading channels2015In: Wireless Communications & Mobile Computing, ISSN 1530-8669, E-ISSN 1530-8677, Vol. 15, no 3, p. 500-509Article in journal (Refereed)
    Abstract [en]

    Cooperative spatial multiplexing (CSM) system has played an important role in wireless networks by offering a substantial improvement in multiplexing gain compared with its cooperative diversity counterpart. However, there is a limited number of research works that consider the performance of CSM systems. As such, in this paper, we have derived exact performance of CSM with amplify-and-forward and decode-and-forward relays in terms of outage capacity and ergodic capacity. We have shown that CSM systems yield a unity diversity order regardless of the number of antennas at the destination and the number of relays in the networks, which is the direct result of diversity and multiplexing gain trade-off. Our analytical expressions are corroborated by Monte-Carlo simulations.

  • 18.
    Duong, Quang Trung
    et al.
    Blekinge Institute of Technology, School of Computing.
    Suraweera, Himal A.
    Tsiftsis, Theodoros A.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, School of Computing.
    Nallanathan, Arumugam
    Keyhole Effect in Dual-Hop MIMO AF Relay Transmission with Space-Time Block Codes2012In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 60, no 12, p. 1-11Article in journal (Refereed)
    Abstract [en]

    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.

  • 19.
    Duong, Quang Trung
    et al.
    Blekinge Institute of Technology, School of Computing.
    Suraweera, Himal A.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, School of Computing.
    Yuen, Chau
    Beamforming in Two-Way Fixed Gain Amplify-and-Forward Relay Systems with CCI2012Conference paper (Refereed)
    Abstract [en]

    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.

  • 20.
    Duong, Quang Trung
    et al.
    Blekinge Institute of Technology, School of Computing.
    Vo, Nguyen-Son
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, School of Computing.
    Shu, Lei
    Du, Xu
    Cheng, Wenping
    Replication Strategies for Video On-Demand over Wireless Mesh Networks: A Cross-Layer Optimization Approach2012In: Using Cross-Layer Techniques for Communication Systems / [ed] Rashvand, Habib F.; Kavian, Yousef S., IGI , 2012, p. 349-375Chapter in book (Refereed)
    Abstract [en]

    In this chapter, dependencies between the different protocol layers and across the hops through WMNs will be exploited to deliver video streaming with high QoE. Specifically, a cross-layer optimization approach is applied to a replication strategy for video on-demand over WMNs. Additionally, the authors consider a distributed implementation algorithm, namely Mod&Timer, to handle the placement of replicas for saving storage resources of the network. Simulation results are shown to demonstrate that the proposed cross-layer design outperforms many existing schemes in terms of QoE. More importantly, compared to other strategies without cross-layer interaction, the proposed cross-layer design satisfies the heterogeneous bandwidth constraint of end users.

  • 21.
    Duong, Quang Trung
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Yeoh, Phee Lep
    Vo, Nguyen Quoc Bao
    Elkashlan, Maged
    Yang, Nan
    Cognitive Relay Networks With Multiple Primary Transceivers Under Spectrum-Sharing2012In: IEEE Signal Processing Letters, ISSN 1070-9908, E-ISSN 1558-2361, Vol. 19, no 11, p. 741-744Article in journal (Refereed)
    Abstract [en]

    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.

  • 22.
    Duong, Quang Trung
    et al.
    Blekinge Institute of Technology, School of Computing.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, School of Computing.
    Cross-Layer Design for Packet Data Transmission in Maximum Ratio Transmission Systems with Imperfect CSI and Co-Channel Interference2012In: Using Cross-Layer Techniques for Communication Systems / [ed] Rashvand, Habib F.; Kavian, Yousef S., IGI , 2012, p. 376-399Chapter in book (Refereed)
    Abstract [en]

    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.

  • 23.
    Duong, Trung Quang
    et al.
    Blekinge Institute of Technology, School of Computing.
    Duy, Tran Trung
    Matthaiou, Michail
    Tsiftsis, Theodoros
    Karagiannidis, George K.
    Cognitive Cooperative Networks in Dual-Hop Asymmetric Fading Channels2013In: 2013 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM), 2013, p. 955-961Conference paper (Refereed)
    Abstract [en]

    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.

  • 24. Elkashlan, Maged
    et al.
    Yeoh, Phee Lep
    Yang, Nan
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Leung, Cyril
    A Comparison of Two MIMO Relaying Protocols in Nakagami- m Fading2012In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 61, no 3, p. 416-1422Article in journal (Refereed)
    Abstract [en]

    Transmit antenna selection with receive maximal-ratio combining (TAS/MRC) and transmit antenna selection with receive selection combining (TAS/SC) are two attractive multiple-input–multiple-output (MIMO) protocols. In this paper, we present a framework for the comparative analysis of TAS/MRC and TAS/SC in a two-hop amplify-and-forward relay network. In doing so, we derive exact and asymptotic expressions for the symbol error rate (SER) in Nakagami-mfading. Using the asymptotic expressions, the SNR gap between the two protocols is quantified. Given that the two protocols maintain the same diversity order, we show that the SNR gap is entirely dependent on the array gain. Motivated by this, we derive the SNR gap as a simple ratio of the respective array gains of the two protocols. This ratio explicitly takes into account the impact of the number of antennas and the fading severity parameter m. In addition, we address the fundamental question of “How to allocate the total transmit power between the source and the relay in such a way that the SER is minimized?” Our answer is given in the form of new compact expressions for the power allocation factor, which is a practical design tool that optimally distributes the total transmit power in the network.

  • 25. Han, Guangjie
    et al.
    Shen, Wen
    Duong, Quang Trung
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Guizani, Mohsen
    Hara, Takahiro
    A proposed security scheme against denial of service attacks in cluster-based wireless sensor networks2014In: Security and Communication Networks, ISSN 1939-0114, E-ISSN 1939-0122, Vol. 7, no 12, p. 2542-2554Article in journal (Refereed)
    Abstract [en]

    Traditional security schemes developed for sensor networks are not suitable for cluster-based wireless sensor networks (WSNs) because of their susceptibility to Denial of Service (DoS) attacks. In this paper, we provide a security scheme against DoS attacks (SSAD) in cluster-based WSNs. The scheme establishes trust management with energy character, which leads nodes to elect trusted cluster heads. Furthermore, a new type of vice cluster head node is proposed to detect betrayed cluster heads. Theoretical analyses and simulation results show that SSAD can prevent and detect malicious nodes with high probability of success

  • 26. Han, Guangjie
    et al.
    Shen, Wen
    Duong, Trung Q.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Guizani, Mohsen
    Hara, Takahiro
    A proposed security scheme against Denial of Service attacks in cluster-based wireless sensor networks2014In: SECURITY AND COMMUNICATION NETWORKS, ISSN 1939-0114, Vol. 7, no 12, p. 2542-2554Article in journal (Refereed)
    Abstract [en]

    Traditional security schemes developed for sensor networks are not suitable for cluster-based wireless sensor networks (WSNs) because of their susceptibility to Denial of Service (DoS) attacks. In this paper, we provide a security scheme against DoS attacks (SSAD) in cluster-based WSNs. The scheme establishes trust management with energy character, which leads nodes to elect trusted cluster heads. Furthermore, a new type of vice cluster head node is proposed to detect betrayed cluster heads. Theoretical analyses and simulation results show that SSAD can prevent and detect malicious nodes with high probability of success

  • 27. Han, Guangjie
    et al.
    Xu, Huihui
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Jiang, Jinfang
    Hara, Takahiro
    Localization algorithms of Wireless Sensor Networks: a survey2013In: Telecommunications Systems, ISSN 1018-4864, E-ISSN 1572-9451, Vol. 52, no 4, p. 2419-2436Article in journal (Refereed)
    Abstract [en]

    In Wireless Sensor Networks (WSNs), localization is one of the most important technologies since it plays a critical role in many applications, e.g., target tracking. If the users cannot obtain the accurate location information, the related applications cannot be accomplished. The main idea in most localization methods is that some deployed nodes (landmarks) with known coordinates (e.g., GPS-equipped nodes) transmit beacons with their coordinates in order to help other nodes localize themselves. In general, the main localization algorithms are classified into two categories: range-based and range-free. In this paper, we reclassify the localization algorithms with a new perspective based on the mobility state of landmarks and unknown nodes, and present a detailed analysis of the representative localization algorithms. Moreover, we compare the existing localization algorithms and analyze the future research directions for the localization algorithms in WSNs.

  • 28. Kim, Kyeong Jin
    et al.
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Poor, H. Vincent
    Lee, Moon Ho
    Performance Analysis of Adaptive Decode-and-Forward Cooperative Single-Carrier Systems2012In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 61, no 7Article, review/survey (Refereed)
    Abstract [en]

    A cyclic prefixed single-carrier (CP-SC) relay network incorporating an adaptive decode-and-forward (ADF) protocol is proposed in this paper. For a two-hop ADF protocol, a general expression for the effective end-to-end signal to noise ratio (ESNR) is examined for multiple relays. With the help of a derived probability density function (PDF) for the ESNR, closedform expressions for the outage probability and an asymptotic average symbol error rate (AASER) are obtained. An asymptotic analysis revealing the diversity gain is also performed. Monte Carlo simulations verify these derived analytical results.

  • 29. Kim, Kyeong Jin
    et al.
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Poor, H. Vincent
    Shu, Lei
    Performance Analysis of Cyclic Prefixed Single-Carrier Spectrum Sharing Relay Systems in Primary User Interference2012In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 60, no 12, p. 6729-6734Article in journal (Refereed)
    Abstract [en]

    For cyclic prefixed single-carrier (CP-SC) spectrum sharing relay systems, the joint impact of the primary transmitter and primary receiver on the performance of secondary networks is investigated. A two-hop amplify-and-forward (AF) relay protocol is employed, and then its end-to-end signal-to-interference-ratio (e2e-SIR) is defined. An upper bound on the cumulative distribution function (CDF) of this e2e-SIR is derived for the CP-SC system. Having investigated an asymptotic expression for the CDF, the asymptotic outage diversity and coding gain can be obtained. Also, under a total transmission constraint, a suboptimal power allocation (sub-OPA) is derived for approximately minimizing the asymptotic outage probability. Monte Carlo simulations verify the derived outage probability and its asymptotic diversity gain with and without power allocation. It is shown that the primary transmitter has a major impact on the secondary network performance. Importantly, it is observed that when the interference from the primary transmitter proportionally increases with the interference power constraint at the primary receiver, the spectrum-sharing system results in no diversity gain for the full range of the SIR.

  • 30. Kim, Kyeong Jin
    et al.
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Tran, Xuan Nam
    Performance Analysis of Cognitive Spectrum-Sharing Single-Carrier Systems With Relay Selection2012In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 60, no 12, p. 6435-6449Article in journal (Refereed)
    Abstract [en]

    In this paper, we analyze the performance of cooperative spectrum sharing single-carrier (SC) relay systems. Taking into account the peak interference power at the primary user (PU) and the maximum transmit power at the secondary user (SU) network, two separate power allocation constraints are formed. For a two-hop decode-and-forward (DF) relaying protocol and two power allocation constraints, two relay selection schemes, namely, a full-channel state information (CSI)-based best relay selection (BRS) and a partial CSI-based best relay selection (PBRS), are proposed. The distributions of the end-to-end signal-to-noise ratios (e2e-SNRs) for the four cases are derived first, and then their outage probabilities and asymptotic outage probabilities are derived in closed-form. The derived asymptotic outage probabilities are utilized to see different diversity gains. Monte Carlo simulations have verified the derived diversity gains for the four different cases. We also present upper bounds on the ergodic capacities for two particular cases.

  • 31. Kim, Kyeong Jin
    et al.
    Duong, Trung Quang
    Blekinge Institute of Technology, School of Computing.
    Elkashlan, Maged
    Yeoh, Phee Lep
    Nallanathan, Arumugam
    Two-Way Cognitive Relay Networks with Multiple Licensed Users2013In: 2013 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM), 2013, p. 992-997Conference paper (Refereed)
    Abstract [en]

    This paper tackles the important question of how to compensate the inherent spectrum efficiency loss in cognitive relay networks. Particularly, by considering two-way cognitive relaying, we seek to enhance the performance of the secondary network in terms of the reliability due to limited transmit power, and the spectral efficiency of the half-duplex dual-hop relay transmission. We derive new closed-form expressions for the outage probability of a cognitive relay network with two-way communications in the presence of multiple primary users. Our expressions accurately take into account the impact of the maximum allowable interference constraint at the primary users on the secondary network.

  • 32. Kim, Kyeong Jin
    et al.
    Duong, Trung Quang
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Elkashlan, Maged
    Yeoh, Phee Lep
    Poor, H. Vincent
    Lee, Moon Ho
    Spectrum Sharing Single-Carrier in the Presence of Multiple Licensed Receivers2013In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 12, no 10, p. 5223-5235Article in journal (Refereed)
    Abstract [en]

    In this paper, maximal-ratio combining (MRC) and selection combining (SC) are proposed in spectrum sharing single-carrier networks with multiple primary user receivers (PU-Rxs). Taking into account the peak interference power at the PU-Rx's and the maximum transmit power at the secondary user (SU), the impact of multiple PU-Rx's on the secondary network is characterized when the secondary user receiver (SURx) is equipped with multiple antennas. In doing so, exact and asymptotic expressions are derived for the cumulative distribution function, taking into account two realistic scenarios: 1) non-identical frequency selective fading between the secondary user transmitter (SU-Tx) and the PUs, and 2) frequency selective fading between the SU-Tx and the SU-Rx. Based on these, exact and asymptotic expressions for the outage probability and average bit error rate are derived. Furthermore, an exact closedform expression for the ergodic capacity is derived. It is shown that the asymptotic diversity gain depends only on the number of receive antennas and the number of multipath channels. It is further shown that the number of PU-Rx's and fading severities between the SU-Tx and the PU-Rx's have no impact on the asymptotic diversity gain.

  • 33. Kim, KyeongJin
    et al.
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Poor, H. Vincent
    Performance analysis of cyclic prefixed single-carrier cognitive amplify-and-forward relay systems2013In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 12, no 1, p. 195-205Article in journal (Refereed)
    Abstract [en]

    A cyclic prefixed single-carrier (CP-SC) relaying system is considered for cognitive radio networks under spectrum sharing condition. The outage probability of secondary users employing a two-hop amplify-and-forward (AF) relay protocol is investigated under an interference constraint inflicted by the secondary user-source and the secondary user-relay on a primary user (PU). Assuming channel-state-information (CSI) is available, the end-to-end signal-to-noise-ratio (e2e-SNR) is first derived, and then an analytical expression for the cumulative distribution function (CDF) of this e2e-SNR is derived. Based on this derived CDF, analytical expressions for the exact outage probability, the approximate symbol error rate (SER), and approximate achievable rate can be obtained. In addition, to reveal further insights into the impact of channel lengths on the diversity and coding gains, the asymptotic outage probability and SER are provided. It is important to note that the performance of cognitive radio networks is degraded due to the limited power constraint inflicted on the primary network. As such, the optimal power allocation (OPA) is also derived to achieve a better asymptotic outage probability.

  • 34. Kim, Kyeongjin
    et al.
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Tsiftsis, Theodoros
    Bao, Vo Nguyen Quoc
    Cognitive multihop networks in spectrum sharing environment with multiple licensed users2013Conference paper (Refereed)
    Abstract [en]

    Multihop network has been considered as a breakthrough frontier to enhance the coverage of wireless network. Spectrum-sharing is an efficient technique to enhance the utilization of the limited radio frequency bandwidth. In this paper, we therefore consider the extension of multihop network to cognitive radio networks with the spectrum sharing approach. In particular, we investigate the cognitive multihop networks in the presence of multiple licensed transmitters and receivers. Under the stringent power constraint imposed by the licensed users, we derive the closed-form and asymptotic expressions for the outage probability over Nakagami-m fading channels. The tractable closed-form expressions reveal the impact of important network parameters such as the fading severity parameters of the unlicensed network, the number of licensed users, the peak interference power imposed by the licensed receivers, the interference power from licensed transmitters. A significant observation corroborated by our study shows that the cognitive multihop networks benefit both cognitive radio and multihop networks for improving the coverage extension and frequency spectrum utilization.

  • 35. KyeongJin, Kim
    et al.
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    H. Vincent, Poor
    Outage probability of single-carrier cooperative spectrum sharing systems with decode-and-forward relaying and selection combining2013In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 12, no 2, p. 806-817Article in journal (Refereed)
    Abstract [en]

    For cyclic prefixed single-carrier (CP-SC) spectrum sharing relaying systems, a two-hop decode-and-forward (DF) relaying protocol with a direct link and selection combining are employed in the secondary user relay network. For this cooperative CP-SC spectrum sharing system, the end-to-end signal-to-noise ratio (e2e-SNR) is first derived, and then the outage probability performance of the secondary user relaying system is investigated. Having derived an asymptotic expression for the cumulative distribution function of the e2e-SNR, the asymptotic outage diversity is obtained under a limited maximum transmit power at the secondary source and relay while satisfying the maximum allowable interference at the primary user. Notably, when the maximum allowable interference is independent of a limited transmission power, an outage probability floor is observed. Moreover, under the assumption of an unlimited transmit power at the secondary nodes, the asymptotic outage diversity is derived as a function of the interference. It can be seen that the same outage diversity gain can be achieved as in the non-spectrum-sharing CP-SC relaying system. Analytically derived asymptotic outage diversity gains for limited and unlimited transmission power cases are verified by Monte Carlo simulations.

  • 36. Li, Jung Shian
    et al.
    Liu, Kun Hsuan
    Chilamkurti, Naveen
    Shu, L.
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Scheduling performance enhancement by network coding in wireless mesh networks2012In: IET Communications, ISSN 1751-8628, E-ISSN 1751-8636, Vol. 6, no 13, p. 1912-1919Article in journal (Refereed)
    Abstract [en]

    When a wireless mesh network accommodates interactive applications with quality of service requirements, schedule-based protocols are more suitable than contention-based protocols. In this paper, the problem of determining an appropriate schedule assignment for multiple group transmissions within a spatial time division multiple access link scheduling network is referred to as an integrated multiple-group communication and link scheduling problem. A polynomial-time scheduling algorithm, designated as a source-parallel-aware assignment (SPAA), is proposed to increase the spatial utilisation within each time slot in order to enhance the network throughput. Furthermore, an advanced version of SPAA, designated as joint source-parallel-aware assignment with network coding (JSANC), is proposed to reduce the effects of bottleneck paths on the schedule frame length by flexibly applying conventional or opportunistic network coding approaches. Simulation results show that the proposed algorithms achieve a better network throughput than existing flow-based or particular order-based scheduling schemes.

  • 37. Ngo, Hien Quoc
    et al.
    Matthaiou, Michail
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Larsson, Erik G.
    Uplink Performance Analysis of Multicell MU-SIMO Systems with ZF receivers2013In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 62, no 9, p. 4471-4483Article in journal (Refereed)
    Abstract [en]

    We consider the uplink of a multicell multiuser single-input multiple-output system, where the channel experiences both small and large-scale fading. The data detection is done by using the linear zero-forcing technique, assuming the base station (BS) has perfect channel state information of all users in its cell. We derive new, exact analytical expressions for the uplink rate, symbol error rate, and outage probability per user, as well as a lower bound on the achievable rate. This bound is very tight and becomes exact in the large-number-of-antennas limit. We further study the asymptotic system performance in the regimes of high signal-to-noise ratio (SNR), large number of antennas, and large number of users per cell. We show that at high SNRs, the system is interference-limited and hence, we cannot improve the system performance by increasing the transmit power of each user. Instead, by increasing the number of BS antennas, the effects of interference and noise can be reduced, thereby improving the system performance. We demonstrate that, with very large antenna arrays at the BS, the transmit power of each user can be made inversely proportional to the number of BS antennas while maintaining a desired quality-of-service. Numerical results are presented to verify our analysis

  • 38. Ngo, Hien Quoc
    et al.
    Matthaiou, Michail
    Duong, Trung Q.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Larsson, Erik G.
    Uplink Performance Analysis of Multicell MU-SIMO Systems With ZF Receivers2013In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 62, no 9, p. 4471-4483Article in journal (Refereed)
    Abstract [en]

    We consider the uplink of a multicell multiuser single-input multiple-output system (MU-SIMO), where the channel experiences both small- and large-scale fading. The data detection is done by using the linear zero-forcing technique, assuming the base station (BS) has perfect channel state information of all users in its cell. We derive new exact analytical expressions for the uplink rate, the symbol error rate (SER), and the outage probability per user, as well as a lower bound on the achievable rate. This bound is very tight and becomes exact in the large-number-of-antenna limit. We further study the asymptotic system performance in the regimes of high signal-to-noise ratio (SNR), large number of antennas, and large number of users per cell. We show that, at high SNRs, the system is interference limited, and hence, we cannot improve the system performance by increasing the transmit power of each user. Instead, by increasing the number of BS antennas, the effects of interference and noise can be reduced, thereby improving system performance. We demonstrate that, with very large antenna arrays at the BS, the transmit power of each user can be made inversely proportional to the number of BS antennas while maintaining a desired quality of service. Numerical results are presented to verify our analysis.

  • 39. Nguyen, Mui Van
    et al.
    Hong, Choong Seon
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Joint Optimal Rate, Power, and Spectrum Allocation in Multi-hop Cognitive Radio Networks2012Conference paper (Refereed)
    Abstract [en]

    Interference due to the sharing of common spectrum band among links and congestion due to the contention among flows sharing the same link have become obstacles to good performance in wireless networks, especially in multi-hop cognitive radio networks (MHCRNs). Consequently, the high end-to-end throughput for MHCRNs calls for a framework of cross-layer optimization design. In this paper, by taking into account the problem of joint optimal rate, power, and spectrum allocation (JORPS), we propose a new cross-layer optimization framework for MHCRNs under spectrum underlay manner using orthogonal frequency division multiple access (OFDMA). The formulation is shown to be a mix-integer non-linear non-convex optimization problem, which is NP-hard in general. To solve the problem, we develop a partially distributed solution, which has been proved to converge to the global optimum with the tradeoff complexity and convergence speed.

  • 40. Pha, Hoc
    et al.
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, School of Computing.
    MIMO Cooperative Multiple-Relay Networks with OSTBCs over Nakagami-m Fading2012Conference paper (Refereed)
    Abstract [en]

    In this paper, the performance of a dual-hop multiple-input multiple-output (MIMO) cooperative multiplerelay network using orthogonal space-time block coding (OSTBC) transmission is examined. The fading environment is modeled as independent, not identical distributed (i.n.i.d.) Nakagami-m fading. Also, we consider the case that each terminal in the network has multiple-antennas, the network operates in channel state information (CSI)-assisted amplify-and-forward (AF) relaying mode, and the direct transmission from the source to the destination is applicable. In particular, we derive a closed-form expression for the moment generating function (MGF) of the instantaneous signal-to-noise ratio (SNR). Utilizing this derivation, we can analyze the SER performance of the considered system for M-ary phase shift-keying (M-PSK) and M-ary quadrature amplitude modulation (M-QAM) scheme. Also, the outage performance of the considered relay networks is evaluated. We further investigate the cooperative diversity behavior by deriving asymptotic approximations for the OP and the SER. Finally, numerical results are provided showing very close agreement between the analytical results and the Monte-Carlo simulations.

  • 41.
    Phan, Hoc
    et al.
    Blekinge Institute of Technology, School of Computing.
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Elkashlan, Maged
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, School of Computing.
    Beamforming Amplify-and-Forward Relay Networks With Feedback Delay and Interference2012In: IEEE Signal Processing Letters, ISSN 1070-9908, E-ISSN 1558-2361, Vol. 19, no 1, p. 16-19Article in journal (Refereed)
    Abstract [en]

    In this letter, we investigate the effect of feedback delay on the performance of a dual-hop amplify-and-forward (AF) relay network with beamforming in the presence of multiple interferers over Rayleigh fading channels. Specifically, we derive closed-form expressions for the outage probability (OP) and the symbol error rate (SER). Furthermore, to render insights into the effect of feedback delay and interference on the network performance, asymptotic OP and SER are also presented. These asymptotic expressions are very tight in the high signal-to-noise ratio regime, readily enabling us to obtain the diversity and coding gains of the considered network.

  • 42.
    Phan, Hoc
    et al.
    Blekinge Institute of Technology, School of Computing.
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, School of Computing.
    Performance analysis of decouple-and-forward MIMO relaying in Nakagami-m fading2012In: IEICE transactions on communications, ISSN 0916-8516, E-ISSN 1745-1345, Vol. E95-B, no 9, p. 3003-3006Article in journal (Refereed)
    Abstract [en]

    The end-to-end performance of dual-hop multiple-input multiple-output (MIMO) decouple-and-forward relaying with orthogonal space-time block code (OSTBC) transmission over Nakagami-m fading is analyzed. By considering the multiple antennas at all nodes, we derive exact closed-form and asymptotic expressions for the outage probability and symbol error rate, which enables us to evaluate the exact performance and reveals the diversity gains of the considered system. In addition, the closedform approximation and asymptotic expressions for the ergodic capacity are also derived. We show that OSTBC transmission over relay systems yields a unit order of multiplexing gain despite the fact that full diversity order, which is equal to the minimum fading severity between the two hops, is achieved.

  • 43.
    Phan, Hoc
    et al.
    Blekinge Institute of Technology, School of Computing.
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, School of Computing.
    Shu, Lei
    Adaptive transmission in MIMO AF relay networks with orthogonal space-time block codes over Nakagami-m fading2012In: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, no 11Article in journal (Refereed)
    Abstract [en]

    In this article, we apply different adaptive transmission techniques to dual-hop multiple-input multiple-output amplify-and-forward relay networks using orthogonal space-time block coding over independent Nakagami-m fading channels. The adaptive techniques investigated are optimal simultaneous power and rate (OSPR), optimal rate with constant power (ORCP), and truncated channel inversion with fixed rate (TCIFR). The expressions for the channel capacity of OSPR, ORCP, and TCIFR, and the outage probability of OSPR, and TCIFR are derived based on the characteristic function of the reciprocal of the instantaneous signal-to-noise ratio (SNR) at the destination. For sufficiently high SNR, the channel capacity of ORCP asymptotically converges to OSPR while OSPR and ORCP achieve higher channel capacity compared to TCIFR. Although TCIFR suffers from an increase in the outage probability relative to OSPR, it provides the lowest implementation complexity among the considered schemes. Along with analytical results, we further adopt Monte Carlo simulations to validate the theoretical analysis.

  • 44.
    Phan, Hoc
    et al.
    Blekinge Institute of Technology, School of Computing.
    Duong, Trung Q.
    Blekinge Institute of Technology, School of Computing.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, School of Computing.
    Tsiftsis, Theodoros A.
    Distributed orthogonal space–time block coding in wireless relay networks2013In: IET Communications, ISSN 1751-8628, E-ISSN 1751-8636, Vol. 7, no 16Article in journal (Refereed)
    Abstract [en]

    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.

  • 45.
    Phan, Hoc
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Duong, Quang Trung
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Tran, Hung
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Chu, Thi My Chinh
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Cognitive amplify-and-forward relay networks with beamforming under primary user power constraint over Nakagami-m fading channels2015In: Wireless Communications & Mobile Computing, ISSN 1530-8669, E-ISSN 1530-8677, Vol. 15, no 1, p. 56-70Article in journal (Refereed)
    Abstract [en]

    In this paper, we analyze the performance of cognitive amplify-and-forward (AF) relay networks with beamforming under the peak interference power constraint of the primary user (PU). We focus on the scenario that beamforming is applied at the multi-antenna secondary transmitter and receiver. Also, the secondary relay network operates in channel state information assisted AF mode, and the signals undergo independent Nakagami-m fading. In particular, closed-form expressions for the outage probability and symbol error rate (SER) of the considered network over Nakagami-m fading are presented. More importantly, asymptotic closed-form expressions for the outage probability and SER are derived. These tractable closed-form expressions for the network performance readily enable us to evaluate and examine the impact of network parameters on the system performance. Specifically, the impact of the number of antennas, the fading severity parameters, the channel mean powers, and the peak interference power is addressed. The asymptotic analysis manifests that the peak interference power constraint imposed on the secondary relay network has no effect on the diversity gain. However, the coding gain is affected by the fading parameters of the links from the primary receiver to the secondary relay network.

  • 46.
    Soffritti, Jacopo
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Duong, Trung Q.
    Merani, Maria Luisa
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Performance Analysis of Randomized Distributed Space-Time Codes over Composite Gamma/Lognormal Fading Channels2014Conference paper (Refereed)
    Abstract [en]

    This work investigates the end-to-end performance of randomized distributed space-time codes with complex Gaussian distribution, when employed in a wireless relay network. The relaying nodes are assumed to adopt a decode-and-forward strategy and transmissions are affected by small and large scale fading phenomena. Extremely tight, analytical approximations of the end-to-end symbol error probability and of the end-to-end outage probability are derived and successfully validated through Monte-Carlo simulation. For the high signal-to-noise ratio regime, a simple, closed-form expression for the symbol error probability is further provided.

  • 47. Suraweera, Himal
    et al.
    Ngo, Hienquoc
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Yuen, Chau
    Larsson, Erik
    Multi-pair amplify-and-forward relaying with very large antenna arrays2013Conference paper (Refereed)
    Abstract [en]

    We consider a multi-pair relay channel where multiple sources simultaneously communicate with destinations using a relay. Each source or destination has only a single antenna, while the relay is equipped with a very large antenna array. We investigate the power efficiency of this system when maximum ratio combining/maximal ratio transmission (MRC/MRT) or zero-forcing (ZF) processing is used at the relay. Using a very large array, the transmit power of each source or relay (or both) can be made inversely proportional to the number of relay antennas while maintaining a given quality-of-service. At the same time, the achievable sum rate can be increased by a factor of the number of source-destination pairs. We show that when the number of antennas grows to infinity, the asymptotic achievable rates of MRC/MRT and ZF are the same if we scale the power at the sources. Depending on the large scale fading effect, MRC/MRT can outperform ZF or vice versa if we scale the power at the relay.

  • 48.
    Tran, Hung
    et al.
    Blekinge Institute of Technology, School of Computing.
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, School of Computing.
    Delay performance of cognitive radio networks for point-to-point and point-to-multipoint communications2012In: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, no 9Article in journal (Refereed)
    Abstract [en]

    In this article, we analyze the packet transmission time in spectrum sharing systems where a secondary user (SU) simultaneously accesses the spectrum licensed to primary users (PUs). In particular, under the assumption of an independent identical distributed Rayleigh block fading channel, we investigate the effect of the peak interference power constraint imposed by multiple PUs on the packet transmission time of the SU. Utilizing the concept of timeout, exact closed-form expressions of outage probability and average packet transmission time of the SU are derived. In addition, employing the characteristics of the M/G/1 queuing model, the impact of the number of PUs and their peak interference power constraint on the stable transmission condition and the average waiting time of packets at the SU are examined. Moreover, we then extend the analysis for point-to-point to point-to-multipoint communications allowing for multiple SUs and derive the related closed-form expressions for outage probability and successful transmission probability for the best channel condition. Numerical results are provided to corroborate our theoretical results and to illustrate applications of the derived closed-form expressions for performance evaluation of cognitive radio networks.

  • 49. Tran, Thien Thanh
    et al.
    Bao, Vo Nguyen Quoc
    Dinh Thanh, Vu
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Performance analysis and optimal relay position of cognitive spectrum-sharing dual-hop decode-and-forward networks2013Conference paper (Refereed)
    Abstract [en]

    The performance of cognitive networks (CNs) has been significantly improved by deploying a third-party, namely relay, to assist the direct communication. However, under a limited transmit power governed by the maximum tolerable interference at the primary network, the cognitive relay network still suffers a performance loss compared to its non-cognitive counterpart. To alleviate this shortcoming, this paper has pro-posed a technique to optimally deploy the relay in CNs. In particular, by assuming the decode-and-forward (DF) relay, we first derive an exact expression for the outage probability (OP) of CNs with spectrum-sharing environment over Nakagami-m channels. Then, using the exact formula, we obtain the asymptotic OP expression which further reveals the impact of networks' parameters on the performance. In addition, the optimal relay placement, i.e., minimizing the system OP, is also investigated by utilizing the asymptotic OP result. We have shown through some representative scenarios that given a fixed coordinate of a primary receiver, the optimal relay deployment significantly outperforms the two conventional approaches, i.e., uniform and random topologies.

  • 50. Vo, Nguyen-Son
    et al.
    Chen, Wenqing
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Rate-user-perceived-quality aware replication strategy for video streaming over wireless mesh networks2011In: KSII Transactions on Internet and Information Systems, ISSN 1976-7277, Vol. 5, no 11, p. 2103-2120Article in journal (Refereed)
    Abstract [en]

    In this research, we consider the replication strategy for the applications of video streaming in wireless mesh networks (WMNs). In particular, we propose a closed-form of optimal replication densities for a set of frames of a video streaming by exploiting not only the skewed access probability of each frame but also the skewed loss probability and skewed encoding rate-distortion information. The simulation results demonstrate that our method improves the replication performance in terms of user-perceived quality (UPQ) which includes: 1) minimum average maximum reconstructed distortion for high peak signal-to-noise ratio (PSNR), 2) small reconstructed distortion fluctuation among frames for smooth playback, and 3) reasonable average maximum transmission distance for continuous playback. Furthermore, the proposed strategy consumes smaller storage capacity compared to other existing optimal replication strategies. More importantly, the effect of encoding rate is carefully investigated to show that high encoding rate does not always gain high performance of replication for video streaming.

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