| 1. |
- Chu, Thi My Chinh, et al.
(författare)
-
Adaptive Modulation and Coding with Queue Awareness in Cognitive Incremental Decode-and-Forward Relay Networks
- 2014
-
Konferensbidrag (refereegranskat)abstract
- This paper studies the performance of adaptive modulation and coding in a cognitive incremental decode-and-forward relaying network where a secondary source can directly communicate with a secondary destination or via an intermediate relay. To maximize transmission efficiency, a policy which flexibly switches between the relaying and direct transmission is proposed. In particular, the transmission, which gives higher average transmission efficiency, will be selected for the communication. Specifically, the direct transmission will be chosen if its instantaneous signal-to-noise ratio (SNR) is higher than one half of that of the relaying transmission. In this case, the appropriate modulation and coding scheme (MCS) of the direct transmission is selected only based on its instantaneous SNR. In the relaying transmission, since the MCS of the transmissions from the source to the relay and from the relay to the destination are implemented independently to each other, buffering of packets at the relay is necessary. To avoid buffer overflow at the relay, the MCS for the relaying transmission is selected by considering both the queue state and the respective instantaneous SNR. Finally, a finite-state Markov chain is modeled to analyze key performance indicators such as outage probability and average transmission efficiency of the cognitive relay network.
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| 2. |
- Chu, Thi My Chinh, et al.
(författare)
-
Amplify-and-Forward Relay Assisting both Primary and Secondary Transmissions in Cognitive Radio Networks over Nakagami-m Fading
- 2012
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we study the performance for the primary and secondary transmissions in cognitive radio networks where the amplify-and-forward (AF) secondary relay helps to transmit the signals for both the primary and secondary transmitters over independent Nakagami-m fading. First, we derive exact closed-form expressions for outage probability and symbol error rate (SER) of the primary network. Then, we derive an exact closed-form expression for outage probability and a closed-form expression of a tight upper bound for SER of the secondary network. Furthermore, we also make a comparison for the performance of the primary system with and without the help of the secondary relay.
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| 3. |
- Chu, Thi My Chinh, et al.
(författare)
-
Beamforming Transmission in Cognitive AF Relay Networks with Feedback Delay
- 2013
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we investigate the effect of feedback delay on outage probability (OP) and symbol error rate (SER) of cognitive amplify-and-forward (AF) relay networks with beamforming transmission in Rayleigh fading environment. It is assumed that the secondary transmitter and the secondary receiver are equipped with multiple antennas, whereas the relay and the primary user comprise of a single antenna. Furthermore, in this system, the secondary users use the underlay scheme in which the secondary transmitter and the relay can coexist with the primary user as long as their interference caused to the primary receiver is below a predefined threshold. Through our analysis, numerical results are provided to show the level of degradation of cognitive AF relay systems in proportion to the degree of feedback delay. In addition, we also present the effect of the number of antennas at the secondary transceiver on the performance of the considered system.
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| 4. |
- Chu, Thi My Chinh, et al.
(författare)
-
Channel Reservation for Dynamic Spectrum Access of Cognitive Radio Networks with Prioritized Traffic
- 2015
-
Ingår i: 2015 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATION WORKSHOP. - : IEEE Communications Society. - 9781467363051 ; , s. 883-888
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we propose a strategy to coordinate the dynamic spectrum access (DSA) of different types of traffic. It is assumed that the DSA assigns spectrum bands to three kinds of prioritized traffic, the traffic of the primary network, the Class 1 traffic and Class 2 traffic of the secondary network. Possessing the licensed spectrum, the primary traffic has the highest access priority and can access the spectrum bands at anytime. The secondary Class 1 traffic has higher priority compared to secondary Class 2 traffic. In this system, a channel reservation scheme is deployed to control spectrum access of the traffic. Specifically, the optimal number of reservation channels is applied to minimize the forced termination probability of the secondary traffic while satisfying a predefined blocking probability of the primary network. To investigate the system performance, we model state transitions of the DSA as a multi-dimensional Markov chain with three-state variables representing the number of primary, Class 1, and Class 2 packets in the system. Based on this chain, important performance measures, i.e., blocking probability and forced termination probability are derived for the Class 1 and Class 2 secondary traffic.
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| 5. |
- Chu, Thi My Chinh, et al.
(författare)
-
Cognitive AF Relay Assisting both Primary and Secondary Transmission with Beamforming
- 2014
-
Konferensbidrag (refereegranskat)abstract
- This paper investigates the system performance of a cognitive relay network with underlay spectrum sharing wherein the relay is exploited to assist both the primary and secondary transmitters in forwarding their signals to the respective destinations. To exploit spatial diversity, beamforming transmission is implemented at the transceivers of the primary and secondary networks. Particularly, exact expressions for the outage probability and symbol error rate (SER) of the primary transmission and tight bounded expressions for the outage probability and SER of the secondary transmission are derived. Furthermore, an asymptotic analysis for the primary network, which is utilized to investigate the diversity and coding gain of the network, is developed. Finally, numerical results are presented to show the benefits of the proposed system.
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| 6. |
- Chu, Thi My Chinh, et al.
(författare)
-
Cognitive MIMO AF Relay Network with TAS/MRC Under Peak Interference Power Constraint
- 2013
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we study the use of transmit antenna selection (TAS) and maximal ratio combining (MRC) for a cognitive multiple-input multiple-output (MIMO) amplify-andforward (AF) relay network. We focus on the scenario that each of the source and relay selects only a single antenna which maximizes the instantaneous signal-to-noise ratio (SNR) to transmit and forward the signal while the receiver combines the signals from all receive antennas. Utilizing TAS, the considered cognitive network not only offers advantages such as achieving full diversity order with low transmit complexity but also reduces the interference induced to the primary transmission as compared to maximum ratio transmission (MRT). This in turn becomes beneficial for the secondary network when this network operates under the interference power constraint of the primary receiver. In particular, we derive expressions for the outage probability and symbol error rate (SER) of the network to evaluate the system performance. We also develop an asymptotic analysis for the outage probability and the SER to obtain diversity and coding gain. With the tractable asymptotic expressions, the effect of network parameters such as the number of antennas, the transmission distances, and the interference power constraint of the primary receiver on the system performance are readily revealed.
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| 7. |
- Chu, Thi My Chinh, et al.
(författare)
-
Delay Analysis for Cognitive Ad Hoc Networks Using Multi-channel Medium Access Control
- 2014
-
Ingår i: IET Communications. - : IET. - 1751-8628 .- 1751-8636. ; 8:7, s. 1083-1093
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, the authors analyse the average end-to-end packet delay for a cognitive ad hoc network where multiple secondary nodes randomly contend for accessing the licensed bands of primary users in non-slotted time mode. Before accessing the licensed bands, each node must perform spectrum sensing and collaboratively exchange the sensing results with other nodes of the corresponding communication as a means of improving the accuracy of spectrum sensing. Furthermore, the medium access control with collision avoidance mechanism based distributed coordination function specified by IEEE802.11 is applied to coordinate spectrum access for this cognitive ad hoc network. To evaluate the system performance, the authors model the considered network as an open G/G/1 queuing network and utilise the method of diffusion approximation to analyse the end-to-end packet delay. The authors’ analysis takes into account not only the number of secondary nodes, the arrival rate of primary users and the arrival rate of secondary users but also the effect of the number of licensed bands when assessing the average end-to-end packet delay of the networks.
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| 8. |
- Chu, Thi My Chinh, et al.
(författare)
-
Dynamic Spectrum Access for Cognitive Radio Networks with Prioritized Traffics
- 2014
-
Ingår i: IEEE Communications Letters. - : IEEE. - 1089-7798 .- 1558-2558. ; 18:7, s. 1218-1221
-
Tidskriftsartikel (refereegranskat)abstract
- We develop a dynamic spectrum access (DSA) strategy for cognitive radio networks where prioritized traffic is considered. Assume that there are three classes of traffic, one traffic class of the primary user and two traffic classes of the secondary users, namely, Class 1 and Class 2. The traffic of the primary user has the highest priority, i.e., the primary users can access the spectrum at any time with the largest bandwidth demand. Furthermore, Class 1 has higher access and handoff priority as well as larger bandwidth demand as compared to Class 2. To evaluate the performance of the proposed DSA, we model the state transitions for DSA as a multi-dimensional Markov chain with three-state variables which present the number of packets in the system of the primary users, the secondary Class 1, and secondary Class 2. In particular, the blocking probability and dropping probability of the two secondary traffic classes are assessed.
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| 9. |
- Chu, Thi My Chinh, et al.
(författare)
-
Hybrid Interweave-Underlay Spectrum Access for Cognitive Cooperative Radio Networks
- 2014
-
Ingår i: IEEE Transactions on Communications. - : IEEE. - 0090-6778 .- 1558-0857. ; 62:7, s. 2183-2197
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we study a hybrid interweave-underlay spectrum access system that integrates amplify-and-forward relaying. In hybrid spectrum access, the secondary users flexibly switch between interweave and underlay schemes based on the state of the primary users. A continuous-time Markov chain is proposed to model and analyze the spectrum access mechanism of this hybrid cognitive cooperative radio network (CCRN). Utilizing the proposed Markov model, steady-state probabilities of spectrum access for the hybrid CCRN are derived. Furthermore, we assess performance in terms of outage probability, symbol error rate (SER), and outage capacity of this CCRN for Nakagami-m fading with integer values of fading severity parameter m. Numerical results are provided showing the effect of network parameters on the secondary network performance such as the primary arrival rate, the distances from the secondary transmitters to the primary receiver, the interference power threshold of the primary receiver in underlay mode, and the average transmit signal-to-noise ratio of the secondary network in interweave mode. To show the performance improvement of the CCRN, comparisons for outage probability, SER, and capacity between the conventional underlay scheme and the hybrid scheme are presented. The numerical results show that the hybrid approach outperforms the conventional underlay spectrum access.
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| 10. |
- Chu, Thi My Chinh, et al.
(författare)
-
Hybrid spectrum access with relay assisting both primary and secondary networks under imperfect spectrum sensing
- 2016
-
Ingår i: EURASIP Journal on Wireless Communications and Networking. - : Springer. - 1687-1472 .- 1687-1499.
-
Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a novel hybrid interweave-underlay spectrum access for a cognitive amplify-and-forward relay network where the relay forwards the signals of both the primary and secondary networks. In particular, the secondary network (SN) opportunistically operates in interweave spectrum access mode when the primary network (PN) is sensed to be inactive and switches to underlay spectrum access mode if the SN detects that the PN is active. A continuous-time Markov chain approach is utilized to model the state transitions of the system. This enables us to obtain the probability of each state in the Markov chain. Based on these probabilities and taking into account the impact of imperfect spectrum sensing of the SN, the probability of each operation mode of the hybrid scheme is obtained. To assess the performance of the PN and SN, we derive analytical expressions for the outage probability, outage capacity, and symbol error rate over Nakagami-m fading channels. Furthermore, we present comparisons between the performance of underlay cognitive cooperative radio networks (CCRNs) and the performance of the considered hybrid interweave-underlay CCRN in order to reveal the advantages of the proposed hybrid spectrum access scheme. Eventually, with the assistance of the secondary relay, performance improvements for the PN are illustrated by means of selected numerical results.
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| 11. |
- Chu, Thi My Chinh, et al.
(författare)
-
MIMO Incremental AF Relay Networks with TAS/MRC and Adaptive Modulation
- 2013
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we study the use of adaptive modulation (AM) for a dual-hop multiple-input multiple-output (MIMO) network with transmit antenna selection (TAS) at the transmitter and maximal ratio combining (MRC) at the receiver. Our system deploys incremental amplify-and-forward (AF) relaying with AM to forward the source signal. A switching policy for selecting between the relaying and the direct communications is utilized to maximize spectrum efficiency. In particular, we derive expressions for the outage probability, spectrum efficiency, and bit error rate (BER) for the considered system over Nakagamim fading. The considered network not only takes advantage of TAS transmission such as achieving full diversity order with low transmit complexity but also inherits the beneficial feature of AM such as spectrum efficiency improvement.
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| 12. |
- Chu, Thi My Chinh, et al.
(författare)
-
On the Performance of Underlay Cognitive Radio Networks Using M/G/1/K Queuing Model
- 2013
-
Ingår i: IEEE Communications Letters. - : IEEE. - 1089-7798 .- 1558-2558. ; 17:5, s. 876-879
-
Tidskriftsartikel (refereegranskat)abstract
- Motivated by a realistic scenario for cognitive radio systems, we model the underlay cognitive radio network (CRN) under interference power constraint imposed by the primary network as an M/G/1/K queueing system. The respective embedded Markov chain is provided to analyze several key queueing performance measures. In particular, the equilibrium probabilities of all states are derived and utilized to evaluate throughput, blocking probability, mean packet transmission time, mean number of packets in the system, and mean waiting time of an underlay CRN with Nakagami-m fading channels.
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| 13. |
- Chu, Thi My Chinh, et al.
(författare)
-
Opportunistic Spectrum Access for Cognitive Amplify-and-Forward Relay Networks
- 2013
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we study the performance of cognitive amplify-and-forward (AF) relay networks where the secondary users opportunistically access M licensed bands of the primary users over Nakagami-m fading channels. In order to enhance the accuracy of spectrum sensing and strongly protect the primary users from being interfered by the secondary transmission, collaborative spectrum sensing is deployed among the secondary transmitter, secondary relay, and secondary receiver. In particular, an analytical expression for the capacity of the considered network is derived. Numerical results are provided to show the influence of the arrival rate of the primary users on the channel utilization of licensed bands. Finally, the impact of the number of the licensed bands, channel utilization of the primary users, false alarm probability, and transmission distances on the capacity of the considered system are investigated.
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| 14. |
- Chu, Thi My Chinh, et al.
(författare)
-
Optimal Secrecy Capacity of Underlay Cognitive Radio Networks with Multiple Relays
- 2016
-
Ingår i: MILCOM 2016 - 2016 IEEE MILITARY COMMUNICATIONS CONFERENCE. - 9781509037810 ; , s. 162-167
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we study the secrecy capacity of an underlay cooperative cognitive radio network (CCRN) where multiple relays are deployed to assist the secondary transmission. An optimal power allocation algorithm is proposed for the secondary transmitter and secondary relays to obtain the maximum secrecy capacity while satisfy the interference power constraint at the primary receiver and the transmit power budget of the CCRN. Since the optimization problem for the secrecy capacity is non-convex, we utilize an approximation and fitting method to convert the optimization problem into a geometric programming problem which then is solved by applying the Logarithmic barrier function. Numerical results are provided to study the effect of network parameters on the secrecy capacity. Through the numerical results, the advantage of the proposed power allocation algorithm compared to equal power allocation can also be observed.
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| 15. |
- Chu, Thi My Chinh, et al.
(författare)
-
Performance analysis of MIMO cognitive amplify-and-forward relay networks with orthogonal space–time block codes
- 2015
-
Ingår i: Wireless Communications & Mobile Computing. - : John Wiley & Sons. - 1530-8669 .- 1530-8677. ; 15, s. 1659-1679
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we study the performance of multiple-input multiple-output cognitive amplify-and-forward relay networks using orthogonal space–time block coding over independent Nakagami-m fading. It is assumed that both the direct transmission and the relaying transmission from the secondary transmitter to the secondary receiver are applicable. In order to process the received signals from these links, selection combining is adopted at the secondary receiver. To evaluate the system performance, an expression for the outage probability valid for an arbitrary number of transceiver antennas is presented. We also derive a tight approximation for the symbol error rate to quantify the error probability. In addition, the asymptotic performance in the high signal-to-noise ratio regime is investigated to render insights into the diversity behavior of the considered networks. To reveal the effect of network parameters on the system performance in terms of outage probability and symbol error rate, selected numerical results are presented. In particular, these results show that the performance of the system is enhanced when increasing the number of antennas at the transceivers of the secondary network. However, increasing the number of antennas at the primary receiver leads to a degradation in the secondary system performance.
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| 16. |
- Chu, Thi My Chinh, et al.
(författare)
-
Performance Evaluation of Cognitive Multi-Relay Networks with Multi-Receiver Scheduling
- 2014
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we investigate the performance of cognitive multiple decode-and-forward relay networks under the interference power constraint of the primary receiver wherein the cognitive downlink channel is shared among multiple secondary relays and secondary receivers. In particular, only one relay and one secondary receiver which offers the highest instantaneous signal-to-noise ratio is scheduled to transmit signals. Accordingly, only one transmission route that offers the best end-to-end quality is selected for communication at a particular time instant. To quantify the system performance, we derive expressions for outage probability and symbol error rate over Nakagami-m fading with integer values of fading severity parameter m. Finally, numerical examples are provided to illustrate the effect of system parameters such as fading conditions, the number of secondary relays and secondary receivers on the secondary system performance.
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| 17. |
- Hoc, Phan, et al.
(författare)
-
Full-Rate Distributed Space-Time Coding for Bi-directional Cooperative Communications
- 2010
-
Konferensbidrag (refereegranskat)abstract
- In this paper, a protocol for bi-directional cooperative communications applying full-rate distributed space-time codes and physical network coding is proposed. This scheme uses L relays to transmit the codewords in a distributed fashion. It takes 3 time slots for two sources to transmit two corresponding codewords by exploiting physical network coding and self-interference cancelation at each source. We prove that this scheme obtains full diversity. The analytical results show that the diversity order of this scheme will be L+1, where L is the number of relays. In addition, we assess the sum-rate of the bi-directional cooperative communication scheme and reveal that it achieves larger spectral efficiency compared to one-way cooperative communication scheme. We employ Monte Carlo simulations to validate the symbol error rate and the ergodic sum-rate of the scheme.
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| 18. |
- Hoc, Phan, et al.
(författare)
-
MIMO AF Semi-blind Relay Networks with OSTBC Transmission over Nakagami-m Fading
- 2011
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we investigate the end-to-end performance of dual-hop multiple-input multiple-output (MIMO) amplify-and-forward (AF) semi-blind relay networks with orthogonal space{-}time block coding (OSTBC) transmission over mutually independent, non-identically distributed (i.n.i.d.) Nakagami-m fading channels. Our analysis considers a semi-blind relay equipped with a single antenna, and a multiple-antenna source and destination. We first derive a closed-form expression for the cumulative distribution function (CDF) of the instantaneous signal-to-noise ratio (SNR). Utilizing this CDF, closed-form expressions for the outage probability (OP) and the symbol error rate (SER) of the considered relay networks are derived. Furthermore, a closed-form approximation expression for the ergodic capacity is presented along with a respective asymptotic formula. Numerical results are given to verify our analysis through representative examples. In particular, the approximation curves are in very close agreement with the Monte Carlo simulations. In the high SNR regime, the asymptotic curves tightly converge to the approximation and simulations.
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| 19. |
- Hoc, Phan, et al.
(författare)
-
Outage Performance for Opportunistic Decode-and-Forward Relaying Coded Cooperation Networks over Nakagami-m Fading
- 2011
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we analyze the outage performance of an opportunistic decode-and-forward (DF) relaying coded cooperation network over independent, and identically distributed Nakagami-m fading channels. In this scheme, cooperative diversity gain is obtained by integrating opportunistic relaying (OR) selection with channel coding. We have derived an analytical expression for the outage probability (OP) of the considered coded cooperation networks for both error-free relays and errors at relays. Furthermore, for comparison, we derive an expression for the OP of a conventional OR cooperative network. For both systems, it has been observed that achievable diversity gain is the same. However, the coded cooperation scheme achieves higher coding gain than the conventional cooperative scheme. Finally, numerical results are provided showing a tightly match between the Monte Carlo simulations and analytical curves.
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| 20. |
- Hoc, Phan, et al.
(författare)
-
SER of Amplify-and-Forward Cooperative Networks with OSTBC Transmission in Nakagami-m Fading
- 2011
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we study the symbol error rate (SER) performance of dual-hop multiple-input multiple-output (MIMO) cooperative relay networks with orthogonal space-time block coding (OSTBC) transmission over independent, not necessarily identical Nakagami-m fading channels. Our analysis considers channel state information (CSI)-assisted amplify-and-forward (AF) relaying with the availability of the direct communication from the source to the destination. In particular, we derive a closed-form expression for moment generating function (MGF) of the instantaneous signal-to-noise ratio (SNR). Utilizing this result, we can analyze the SER performance of the considered systems for M-ary phase shift-keying (M-PSK) and M-ary quadrature amplitude (M-QAM) modulations. We further investigate the cooperative diversity behavior of the considered relay systems by deriving asymptotic approximations of SER in the high SNR regime. Finally, representative numerical results are presented showing an excellent agreement with the Monte-Carlo simulations which validates our analysis.
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| 21. |
- Phan, Hoc, et al.
(författare)
-
Adaptive transmission in MIMO AF relay networks with orthogonal space-time block codes over Nakagami-m fading
- 2012
-
Ingår i: EURASIP Journal on Wireless Communications and Networking. - : Springer. - 1687-1472 .- 1687-1499. ; :11
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 22. |
- Phan, Hoc, et al.
(författare)
-
Amplify-and-forward relay networks with underlay spectrum access over frequency selective fading channels
- 2015
-
Ingår i: IEEE Vehicular Technology Conference Proceedings. - : IEEE Communications Society. - 9781479980888 ; , s. Article number 7145676-
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we investigate the system performance in terms of outage probability and symbol error rate of cognitive relay networks with underlay spectrum access over Nakagami-m frequency selective fading channels. Underlay spectrum access is deployed at the secondary transmitters, i.e., the secondary source and relay, as a means of providing high spectrum utilization efficiency. It is assumed that the whole system operates in frequency selective fading channels which commonly occur in broadband communication networks. In addition, direct communication from the secondary source to destination is present together with relay communication such that the selection combining is applied at the destination. That is, either the direct or relay channel is selected for communication depending on which one provides the best signal-to-noise ratio (SNR). Analytical expressions for crucial performance measures such as outage probability and symbol error rate are formulated. Based on these analytical outcomes, respective system performance is investigated through numerical results for various system parameters and scenarios. © 2015 IEEE.
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| 23. |
- Phan, Hoc, et al.
(författare)
-
Beamforming Amplify-and-Forward Relay Networks With Feedback Delay and Interference
- 2012
-
Ingår i: IEEE Signal Processing Letters. - : IEEE. - 1070-9908 .- 1558-2361. ; 19:1, s. 16-19
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 24. |
- Phan, Hoc, et al.
(författare)
-
Cognitive amplify-and-forward relay networks with beamforming under primary user power constraint over Nakagami-m fading channels
- 2015
-
Ingår i: Wireless Communications & Mobile Computing. - : Wiley. - 1530-8669 .- 1530-8677. ; 15:1, s. 56-70
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 25. |
- Phan, Hoc, et al.
(författare)
-
Delay and Throughput Analysis for Opportunistic Decode-and-Forward Relay Networks
- 2013
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we develop a queueing analysis for opportunistic decode-and-forward (DF) relay networks. It is assumed that the networks undergo Nakagami-m fading and that the external arrival process follows a Poisson distribution. By selecting the best relay according to the opportunistic relaying scheme, the source first transmits its signal to the best relay which then attempts to decode the reception and forwards the output to the destination. It is assumed that each relay operates in full-duplex mode, i.e., it can receive and transmit signals simultaneously. The communication process throughout the network can be modeled as a queueing network which is structured from sub-systems of M/G/1 and G/G/1 queueing stations. We invoke the approximate analysis, so-called method of decomposition, to analyze the performance behavior of the considered relay network. The whole queueing network is broken into separate queues which are then investigated individually. Based on this approach, the end-to-end packet transmission time and throughput of the considered relay network are quantified in comparison with the networks with partial relay selection (PRS).
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| 26. |
- Phan, Hoc, et al.
(författare)
-
Distributed orthogonal space–time block coding in wireless relay networks
- 2013
-
Ingår i: IET Communications. - : IET. - 1751-8628 .- 1751-8636. ; 7:16
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, the authors consider distributed orthogonal space–time block coding for relay-based channel state information-assisted amplify-and-forward networks. Specifically, they show that opportunistic relaying (OR) is an optimal solution in terms of instantaneous signal-to-noise ratio (SNR), that is, it provides the maximum instantaneous SNR under the constraint of fixed transmit power for the relays. In particular, instead of allocating the given transmit power to all relays, letting the best relay transmit with this power is an optimal solution for maximising the received SNR. To exhibit this benefit, Monte Carlo simulations are presented showing superior performance of the OR scheme compared to equal power allocation policy for the considered relay networks. For the considered optimal scenario, the authors further derive analytical expressions for the outage probability and symbol error rate (SER) over quasi-static independent, not necessarily identically distributed Nakagami-m fading channels. They further present asymptotically tight approximations for the outage probability and SER in the high SNR regime, rendering insights into the cooperative diversity behaviour. Finally, numerical results are provided to examine the effect of network parameters on the system performance of the considered network.
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| 27. |
- Phan, Hoc, et al.
(författare)
-
Impact of interference power constraint on multi-hop cognitive amplify-and-forward relay networks over Nakagami-m fading
- 2013
-
Ingår i: IET Communications. - : IET. - 1751-8628 .- 1751-8636. ; 7:9, s. 860-866
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Tidskriftsartikel (refereegranskat)abstract
- In this article, the authors study the effect of peak interference power constraint given by the primary receiver on the performance of multi-hop cognitive amplify-and-forward (AF) relay networks. The athours assume that all involved channels are subject to independent, not necessarily identically distributed Nakagami-m fading and the secondary multi-hop relay network operates in channel state information-assisted AF mode. An analysis of the system performance in terms of outage probability and symbol error rate (SER) is presented. Accordingly, closed-form expressions for the tightly bounded outage probability and SER are formulated which are used for quantifying the impact of the fading channels, the interference power constraint and the number of hops on system performance. More importantly, an asymptotic performance analysis, which intuitively reveals benefits of cooperative diversity of the secondary relay network, is established. The analysis shows that the diversity gain of the considered cognitive relay networks is equal to the minimum of the fading severity parameters of all relaying hops. Also, the interference power constraint imposed by the primary receiver only affects the coding gain of the secondary relay network.
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| 28. |
- Phan, Hoc, et al.
(författare)
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Packet Loss Priority of Cognitive Radio Networks with Partial Buffer Sharing
- 2015
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Ingår i: 2015 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC). - : IEEE Computer Society. - 9781467364324 ; , s. 7646-7652
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Konferensbidrag (refereegranskat)abstract
- In this paper, we consider the application of partial buffer sharing to an M/G/1/K queueing system for cognitive radio networks (CRNs). It is assumed that the CRN is subject to Nakagami-m. fading. Secondary users are allowed to utilize the licensed radio spectrum of the primary users through underlay spectrum access. A finite buffer at the secondary transmitter is partitioned into two regions, the first region serves both classes of packets while the second region serves only packets of the highest priority class. Therefore, the examined CRN can be modeled as an M/G/1/K queueing system using partial buffer sharing. An embedded Markov chain is applied to analyze the queueing behavior of the system. Utilizing the balance equations and the normalized equation, the equilibrium state distribution of the system at an arbitrary time instant can be found. This outcome is utilized to investigate the impact of queue length, arrival rates, and fading parameters on queueing performance measures such as blocking probability, throughput, mean packet transmission time, channel utilization, mean number of packets in the system, and mean packet waiting time for each class of packets.
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| 29. |
- Phan, Hoc, et al.
(författare)
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Performance analysis of decouple-and-forward MIMO relaying in Nakagami-m fading
- 2012
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Ingår i: IEICE transactions on communications. - : IEICE. - 0916-8516 .- 1745-1345. ; E95-B:9, s. 3003-3006
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 30. |
- Phan, Hoc
(författare)
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Performance Assessment of Cooperative Relay Networks with Advanced Radio Transmission Techniques
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the past decade, cooperative communications has been emerging as a pertinent technology for the current and upcoming generations of mobile communication infrastructure. The indispensable benefits of this technology have motivated numerous studies from both academia and industry on this area. In particular, cooperative communications has been developed as a means of alleviating the effect of fading and hence improve the reliability of wireless communications. The key idea behind this technique is that communication between the source and destination can be assisted by several intermediate nodes, so-called relay nodes. As a result, cooperative communication networks can enhance the reliability of wireless communications where the transmitted signals are severely impaired because of fading. In addition, through relaying transmission, communication range can be extended and transmit power of each radio terminal can be reduced as well. The objective of this thesis is to analyze the system performance of cooperative relay networks integrating advanced radio transmission techniques and using the two major relaying protocols, i.e., decode-and-forward (DF) and amplify-and-forward (AF). In particular, the radio transmission techniques that are considered in this thesis include multiple-input multiple-output (MIMO) systems and orthogonal space-time block coding (OSTBC) transmission, adaptive transmission, beamforming transmission, coded cooperation, and cognitive radio transmission. The thesis is divided into an introduction section and six parts based on peer-reviewed journal articles and conference papers. The introduction provides the readers with some fundamental background on cooperative communications along with several key concepts of cognitive radio systems. In the first part, performance analysis of cooperative single and multiple relay networks using MIMO and OSTBC transmission is presented wherein the diversity gain, coding gain, outage probability, symbol error rate, and channel capacity are assessed. It is shown that integrating MIMO and OSTBC transmission into cooperative relay networks provides full diversity gain. In the second part, the performance benefits of MIMO relay networks with OSTBC and adaptive transmission strategies are investigated. In the third part, the performance improvement with respect to outage probability of coded cooperation applied to opportunistic DF relay networks over conventional cooperative networks is shown. In the fourth part, the effects of delay of channel state information feedback from the destination to the source and co-channel interference on system performance is analyzed for beamforming AF relay networks. In the fifth part, cooperative diversity is investigated in the context of an underlay cognitive AF relay network with beamforming. In the sixth part, finally, the impact of the interference power constraint on the system performance of multi-hop cognitive AF relay networks is investigated.
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| 31. |
- Phan, Hoc, et al.
(författare)
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Performance of Cognitive Radio Networks with Finite Buffer Using Multiple Vacations and Exhaustive Service
- 2014
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Ingår i: 2014 8TH INTERNATIONAL CONFERENCE ON SIGNAL PROCESSING AND COMMUNICATION SYSTEMS (ICSPCS). - Gold Coast, Australia : IEEE. - 9781479952557
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Konferensbidrag (refereegranskat)abstract
- In this paper, we analyze the performance of a cognitive radio network where the secondary transmitter, besides its own transmission, occasionally relays the primary signal. It is assumed that the secondary transmitter employs the exhaustive service mode to transmit the secondary signal and multiple vacations to relay the primary signal. When assisting the primary transmitter, we assume that the secondary transmitter utilizes the decode-and-forward protocol to process the primary signal and forwards it to the primary receiver. Furthermore, the secondary transmitter has a finite buffer, the arriving packets of the secondary network are modeled as a Poisson process, and all channels are subject to Nakagami-m fading. Modeling the system as an M/G/1/K queueing system with exhaustive service and multiple vacations, using an embedded Markov chain approach to analyze the system, we obtain several key queueing performance indicators, i.e., the channel utilization, blocking probability, mean number of packets, and mean serving time of a packet in the system. The derived formulas are then utilized to evaluate the performance of the considered system.
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| 32. |
- Phan, Hoc, et al.
(författare)
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Physical-layer network coding with multi-antenna transceivers in interference limited environments
- 2016
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Ingår i: IET Communications. - : Institute of Engineering and Technology. - 1751-8628 .- 1751-8636. ; 10:4, s. 363-371
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Tidskriftsartikel (refereegranskat)abstract
- In this study, the authors first analyse system performance of beamforming amplify-and-forward two-way relay networks with physical-layer network coding under the impact of co-channel interference from multiple surrounding terminals and then propose the associated power allocation strategies. The performance of the two-way communications in terms of outage probability, symbol error rate (SER), and total ergodic channel capacity of the system is quantified. Asymptotic performance analysis for sufficiently high signal-to-noise ratio is also provided to obtain further valuable insights into system designs. Based on the analysis, power allocation strategies to minimise the asymptotic outage probability and SER as well as to maximise the ergodic channel capacity under the total power constraint are developed. The numerical results show that the proposed power allocation approaches outperform equal power allocation given the same total power budget and other system parameters. © The Institution of Engineering and Technology.
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| 33. |
- Tran, Hung, et al.
(författare)
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Cognitive Cooperative Networks with Cluster-Based Relaying under Interference Constraints
- 2013
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Konferensbidrag (refereegranskat)abstract
- In this paper, we consider the outage performance of a cognitive cooperative radio network (CCRN) in which the secondary base station (SBS) transmits signals to multiple secondary receivers (SU-Rx) through the help of multiple secondary relays (SRs). It is assumed that the SRs are geographically distributed in clusters and that the considered network operates in a Rayleigh environment. In addition, we assume that the transmit powers of the SBS and SRs are subject to peak interference power constraints of the primary users (PUs) in their respective coverage range. Specifically, a closed-form expression for the outage probability of the SU-Rx with the worst channel condition is derived for independently distributed Rayleigh fading. The obtained outage expression is further utilized to examine the impact of the channel mean powers, the number of SRs distributed in each cluster and the number of clusters on the system performance.
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| 34. |
- Tran, Hung, et al.
(författare)
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Cognitive cooperative networks with decode-and-forward relay selection under interference constraints of multiple primary users
- 2015
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Ingår i: Wireless Communications & Mobile Computing. - : Wiley. - 1530-8669 .- 1530-8677. ; 15:10, s. 1433-1443
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we study the performance of cognitive cooperative radio networks under the peak interference power constraints of multiple primary users (PUs). In particular, we consider a system model where the secondary user communication is assisted by multiple secondary relays (SRs) that operate in the decode-and-forward mode to relay the signal from a secondary transmitter to a secondary receiver. Moreover, we assume that the transmit powers of the secondary transmitter and the SRs are subject to the peak interference power constraints of multiple PUs that operate in their coverage range. Given this system setting, we first derive the cumulative distribution function of the instantaneous end-to-end signal-to-noise ratio. Then, we obtain a closed-form expression for the outage probability and an exact expression for the symbol error probability of the considered network. These tractable formulas enable us to examine the impact of the presence of multiple PUs on the performance of the considered spectrum sharing system. Furthermore, our numerical results show that system performance is improved significantly when the number of SRs increases or the channel mean power from the secondary user to the PUs is low. Also, any increase in the number of PUs in the coverage range of the secondary transmitter or the SRs leads to degradation in system performance. Finally, Monte Carlo simulations are provided to verify the correctness of our analytical results.
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| 35. |
- Tran, Hung, et al.
(författare)
-
Cognitive Proactive and Reactive DF Relaying Schemes under Joint Outage and Peak Transmit Power Constraints
- 2013
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Ingår i: IEEE Communications Letters. - : IEEE. - 1089-7798 .- 1558-2558. ; 17:8, s. 1548-1551
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, outage performance of cognitive cooperative radio networks using two decode-and-forward (DF) schemes is investigated. Subject to the joint outage constraint of the primary user and the peak transmit power constraint of the secondary user, adaptive power allocation policies for the secondary transmitter and secondary relays are studied. Based on these strategies, expressions for the outage probability of proactive and reactive DF schemes are obtained. Interestingly, our results show that an increase in the transmit power of the primary transmitter (PU-Tx) does not always degrade the performance of the secondary network. In fact, the PU-Tx transmit power is a substantial parameter that the secondary users can adapt to in order to improve the system performance. The numerical results additionally show that the performance of the reactive DF scheme outperforms the proactive DF scheme if the outage threshold in the first hop of the reactive DF scheme is less than that of the proactive scheme.
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| 36. |
- Tran, Hung, et al.
(författare)
-
Impact of the Number of Antennas and Distances Among Users on Cognitive Radio Networks
- 2012
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we study the impact of the number of antennas and distances among users on the performance of a spectrum sharing system. In particular, we assume that a secondary transmitter is equipped with a single antenna while both secondary receiver and primary receiver have multiple antennas. Also, it is assumed that the secondary users are subject to the peak interference power constraint. On this basis, the cumulative distribution function and probability density function for the signal-to-noise ratio are derived for Rayleigh fading channels. Moreover, using these results, we obtain closed-form expressions for the outage probability, ergodic capacity and an exact expression for symbol error probability. These formulas allow us to examine the impact of the number of antennas of the SU-Rx, the PU-Rx and distance among users on the system performance. Finally, Monte-Carlo simulations are provided to verify our analytical results.
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| 37. |
- Tran, Hung, et al.
(författare)
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On Throughput and Quality of Experience in Cognitive Radio Networks
- 2016
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Ingår i: 2016 IEEE WIRELESS COMMUNICATIONS AND NETWORKING CONFERENCE. - : IEEE. - 9781467398145
-
Konferensbidrag (refereegranskat)abstract
- In this paper, a performance analysis for cognitive radio networks (CRNs) under the outage probability constraint of the primary user and peak transmit power constraint of the secondary user is conducted. Given an automatic repeat request protocol, analytical expressions for the packet delay and throughput of the CRN are derived. Most importantly, these expressions can be used to understand the quality of experience on web services which are assumed to be offered by the considered CRN.
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| 38. |
- Tran, Hung, et al.
(författare)
-
Outage Probability, Average Transmission Time, and Quality of Experience for Cognitive Radio Networks over General Fading Channels
- 2012
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we examine the delay performance in cognitive radio networks (CRNs) over general fading channels where secondary users are allowed to simultaneously access the spectrum licensed by primary users. In particular, subject to the peak interference power constraint, we investigate the effect of general fading channels on the delivery delay of data packets and acknowledgements (ACKs). A lower bound of outage probability and an upper bound of average transmission time are derived by utilizing the concept of timeout. Specifically, we apply the above results to investigate the quality of experience (QoE) for various fading channels, such as one-sided Gaussian, Rayleigh, Nakagami-m and Weibull channels. The numerical results indicate that the delay of ACKs under severe fading leads to a degradation of system performance.
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| 39. |
- Tran, Hung, et al.
(författare)
-
Performance Analysis of a Cognitive Radio Network with a Buffered Relay
- 2015
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Ingår i: IEEE Transactions on Vehicular Technology. - : IEEE. - 0018-9545 .- 1939-9359. ; 64:2, s. 566-579
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we analyze the packet transmission time in a cognitive cooperative radio network (CCRN) where a secondary transmitter (SU-Tx) sends packets to a secondary receiver (SU-Rx) through the help of a secondary relay (SR). In particular, we assume that the SU-Tx and SR are subject to the joint constraint of the timeout probability of the primary user (PU) and the peak transmit powers of the secondary users. On this basis, we investigate the impact of the transmit power of the PUs and channel mean powers on the packet transmission time of the CCRN. Utilizing the concept of timeout, adaptive transmit power allocation policies for the SU-Tx and SR are considered. More importantly, analytical expressions for the endto- end throughput, end-to-end packet transmission time, and stable condition for the SR operation are obtained. Our results indicate that the second hop of the considered CCRN is not a bottleneck if the channel mean powers of the interference links of the networks are small and the SR peak transmit power is set to a high value.
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