| 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. |
- Al-Qahtani, Fawaz S., et al.
(författare)
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Performance Analysis of Dual-Hop AF Systems with Interference in Nakagami-m Fading Channels
- 2011
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Ingår i: IEEE Signal Processing Letters. - : IEEE. - 1070-9908. ; 18:8, s. 454-457
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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)
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Selection Decode-and-Forward Relay Networks with Rectangular QAM in Nakagami-m Fading Channels
- 2010
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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)
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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
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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)
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Distributed Switch-and-Stay Combining in Cognitive Relay Networks under Spectrum Sharing Constraints
- 2013
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Ingår i: 2013 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM). - : IEEE Communications Society. - 9781479913534 ; , s. 1927-1932
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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)
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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
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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)
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Exact Outage Probability of Cognitive Underlay DF Relay Networks with Best Relay Selection
- 2012
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Ingår i: IEICE transactions on communications. - : IEICE. - 0916-8516 .- 1745-1345. ; E95-B:6, s. 2169-2173
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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)
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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
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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)
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Outage Analysis of Cognitive Multihop Networks under Interference Constraints
- 2012
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Ingår i: IEICE transactions on communications. - : IEICE. - 0916-8516 .- 1745-1345. ; E95-B:3
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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)
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The scheme of mitigating the asymmetric links problem in wireless sensor networks
- 2010
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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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