| 1. |
- Duong, Trung Quang, et al.
(författare)
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Cognitive Cooperative Networks in Dual-Hop Asymmetric Fading Channels
- 2013
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Ingår i: 2013 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM). - 2334-0983 .- 2576-6813. - 9781479913534 ; , s. 955-961
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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. |
- Duong, Quang Trung, et al.
(författare)
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Effect of primary network on performance of spectrum sharing AF relaying
- 2012
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Ingår i: Electronics Letters. - : IET. - 0013-5194 .- 1350-911X. ; 48:1, s. 25-U95
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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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| 3. |
- Kim, Kyeong Jin, et al.
(författare)
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Performance Analysis of Cognitive Spectrum-Sharing Single-Carrier Systems With Relay Selection
- 2012
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Ingår i: IEEE Transactions on Signal Processing. - : IEEE. - 1053-587X .- 1941-0476. ; 60:12, s. 6435-6449
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 4. |
- Tran, Hung, et al.
(författare)
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Average Waiting Time of Packets with Different Priorities in Cognitive Radio Networks
- 2010
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Konferensbidrag (refereegranskat)abstract
- In this paper, we investigate the average waiting time of packets with different priorities in cognitive radio networks (CRN) using a preemptive priority queuing system. Specifically, we consider two scenarios for CRN, the first with the secondary user (SU) sensing at the beginning of each time slot and the other with the SU having continues sensing ability. Our analysis shows that the average waiting time of packets for the SU does not only depend on the size of packets and arrival rate of the SU traffic but also depends on the arrival rate and size of packets from primary users (PU). Moreover, the results show that an SU with continuous sensing ability can utilize spectrum better than sensing at the beginning of each time slot.
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| 5. |
- Tran, Hung, et al.
(författare)
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Delay performance of cognitive radio networks for point-to-point and point-to-multipoint communications
- 2012
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Ingår i: EURASIP Journal on Wireless Communications and Networking. - : Springer. - 1687-1472 .- 1687-1499. ; :9
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 6. |
- Tran, Hung, et al.
(författare)
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On the Performance of Spectrum Sharing Systems Over Alpha-Mu Fading Channel for Non-identical Mu Parameter
- 2011
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Konferensbidrag (refereegranskat)abstract
- Spectrum sharing is a promising approach in cognitive radio networks to improve the spectrum utilization of wireless communication systems. In this paper, we analyze the performance of spectrum sharing systems under the peak interference constraint for a general fading model, namely the Alpha-Mu fading channel. In particular, we derive expressions for statistical characteristics such as probability density function and cumulative distribution function of the end-to-end signal-tonoise ratio for dissimilar parameter Mu. Using these statistics, we obtain the closed-form expressions for outage probability, amount of fading and approximate ergodic capacity for the considered spectrum sharing system. Finally, Monte Carlo simulations are presented to verify the analytical results.
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| 7. |
- Tran, Hung, et al.
(författare)
-
Performance Analysis of Cognitive Relay Networks Under Power Constraint of Multiple Primary Users
- 2011
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Konferensbidrag (refereegranskat)abstract
- Cognitive relaying is a promising technique to improve spectrum utilization in mobile networks. In this paper, we consider a scenario in which a secondary transmitter communicates with a secondary receiver by the help of a secondary relay. The secondary user should adjust its transmission power in order to not cause any harmful interference to the multiple primary users operating in the licensed spectrum. In this context, we investigate the end-to-end performance of cognitive relay networks in terms of outage probability and ergodic capacity over Nakagami-m fading channels. A closed-form expression for outage probability and an approximation for ergodic capacity are derived. Furthermore, the presented numerical examples illustrate the impact of the number of primary users on the performance of cognitive relay networks.
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| 8. |
- Tran, Hung, et al.
(författare)
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Performance of a Spectrum Sharing System over Nakagami-m Fading Channels
- 2010
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Konferensbidrag (refereegranskat)abstract
- In this paper, we derive the probability density function and cumulative distribution function of packet transmission time in a spectrum sharing system. In combination with the time-out characteristics of packets, we further study the outage probability and average transmission time under peak power interference constraint over Nakagami-m fading channel. Especially, we employ the M/G/1 queuing model to calculate the average waiting time of packets and average number of packets waiting in the queue of a secondary user. The numerical results show the importance of the peak interference power constraint on the delay of packets at the secondary user.
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| 9. |
- Tran, Hung, et al.
(författare)
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Queuing Analysis For Cognitive Radio Networks Under Peak Interference Power Constraint
- 2011
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Konferensbidrag (refereegranskat)abstract
- In this paper, we study the effect of peak interference power constraint on outage probability and transmission time of packets for secondary user (SU) in a spectrum sharing environment. In the considered cognitive radio network scenario, a secondary user transmitter sends its packets over a Rayleigh fading channel. In combination with the analysis of time out characteristics, queuing models are deployed to evaluate average transmission time of packets, average waiting time of packets, and average number of packets waiting in the queue of the cognitive user.
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| 10. |
- Tran, Nguyen Nam, et al.
(författare)
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Training Design upon Mutual Information for Spatially Correlated MIMO-OFDM
- 2010
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Konferensbidrag (refereegranskat)abstract
- Our goal in this paper is to address channel estimations for spatially correlated multiple-input multiple-output with orthogonal frequency-division multiplexing (MIMO-OFDM) system upon the conditional mutual information (CMI). The design of superimposed training signal by maximizing the channel CMI is fully investigated. First, the interior-point-method is employed to obtain the optimal superimposed training signals for the general case of channel correlations. In addition, two efficient approximate designs are also proposed by invoking Karush-Kuhn-Tucker condition for optimality of convex programming. The first approximate design is obtained by proposing a iterativebisection-procedure (IBP), while the second one is in “waterfilling” closed-form. Numerical results demonstrate the excellent performance of the proposed designs and give the connection between channel estimation error and mutual information.
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