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Buffer-Aided Relaying with Adaptive Link Selection
"... In this paper, we consider a simple network consisting of a source, a half-duplex decode-and-forward relay, and a destination. We propose a new relaying protocol employing adaptive link selection, i.e., in any given time slot, based on the channel state information of the source-relay and the relay- ..."
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Cited by 21 (4 self)
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In this paper, we consider a simple network consisting of a source, a half-duplex decode-and-forward relay, and a destination. We propose a new relaying protocol employing adaptive link selection, i.e., in any given time slot, based on the channel state information of the source-relay and the relay-destination link a decision is made whether the source or the relay transmits. In order to avoid data loss at the relay, adaptive link selection requires the relay to be equipped with a buffer such that data can be queued until the relay-destination link is selected for transmission. We study both delay constrained and delay unconstrained transmission. For the delay unconstrained case, we characterize the optimal link selection policy, derive the corresponding throughput, and develop an optimal power allocation scheme. For the delay constrained case, we propose to starve the buffer of the relay by choosing the decision threshold of the link selection policy smaller than the optimal one and derive a corresponding upper bound on the average delay. Furthermore, we propose a modified link selection protocol which avoids buffer overflow by limiting the queue size. Our analytical and numerical results show that buffer-aided relaying with adaptive link selection achieves significant throughput gains compared to conventional relaying protocols with and without buffers where the relay employs a fixed schedule for reception and transmission. I.
Opportunistic relay selection for cooperative networks with secrecy constraints
- IET Communications
, 2010
"... Abstract—In this paper, a relay selection policy is proposed that fully exploits the flexibility offered by the buffering ability of the relay nodes in order to maximize the achieved diversity gain. The suggested scheme incorporates the instantaneous strength of the wireless links as well as the sta ..."
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Cited by 11 (0 self)
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Abstract—In this paper, a relay selection policy is proposed that fully exploits the flexibility offered by the buffering ability of the relay nodes in order to maximize the achieved diversity gain. The suggested scheme incorporates the instantaneous strength of the wireless links as well as the status of the finite relay buffers and adapts the relay selection decision on the strongest available link by dynamically switching between relay reception and transmission. We show that the proposed relay selection scheme significantly outperforms conventional relay selection policies for all cases and ensures a diversity gain equal to two times the number of relays for large buffer sizes. I.
Buffer-aided Successive Opportunistic Relaying with Inter-Relay Interference Cancellation
"... Abstract—In this paper we consider a simple cooperative network consisting of a source, a destination and a cluster of decode-and-forward relays characterized by the half-duplex constraint. At each time-slot the source and (possibly) one of the relays transmit a packet to another relay and the desti ..."
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Cited by 3 (2 self)
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Abstract—In this paper we consider a simple cooperative network consisting of a source, a destination and a cluster of decode-and-forward relays characterized by the half-duplex constraint. At each time-slot the source and (possibly) one of the relays transmit a packet to another relay and the destination, respectively. When the source and a relay transmit simulta-neously, inter-relay interference is introduced at the receiving relay. In this work, with the aid of buffers at the relays, we mitigate the detrimental effect of inter-relay interference through either interference cancellation or mitigation. More specifically, we propose the min − power opportunistic relaying protocol that minimizes the total energy expenditure per time slot under an inter-relay interference cancellation scheme. The min − power relay-pair selection scheme, apart from minimizing the energy expenditure, also provides better throughput and lower outage probability than existing works in the literature. The perfor-mance of the proposed scheme is demonstrated via illustrative examples and simulations in terms of outage probability and average throughput. I.
Capacity Improvement through Buffer-Aided Successive Opportunistic Relaying
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Wireless physical layer security enhancement with buffer-aided relaying
- in Proc. 47th Asilomar Conf
, 2013
"... Abstract—We consider utilizing a buffer-aided relay to enhance security for two-hop half-duplex relay networks with an external eavesdropper. We propose a link selection scheme that adapts re-ception and transmission time slots based on the channel quality, while considering both the two-hop transmi ..."
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Cited by 2 (1 self)
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Abstract—We consider utilizing a buffer-aided relay to enhance security for two-hop half-duplex relay networks with an external eavesdropper. We propose a link selection scheme that adapts re-ception and transmission time slots based on the channel quality, while considering both the two-hop transmission efficiency and the security. Closed-form expressions for the secrecy throughput and the secrecy outage probability (SOP) are derived, and the selection parameters are optimized to maximize the secrecy throughput or minimize the SOP. We also study two sub-optimal link selection schemes that only require a line search to solve the optimization problem. Numerical results show that buffer-aided relaying provides a significant improvement in security compared to conventional unbuffered relaying. I.
Distributed Joint Relay-Pair Selection for Buffer-Aided Successive Opportunistic Relaying
"... Abstract—In this work, we propose a buffer-aided successive opportunistic relay scheme where each time a relay-pair is selected with the target of rate maximization. Due to overlapping transmissions by the source and the relay which transmits to the destination, inter-relay interference arises. The ..."
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Cited by 2 (1 self)
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Abstract—In this work, we propose a buffer-aided successive opportunistic relay scheme where each time a relay-pair is selected with the target of rate maximization. Due to overlapping transmissions by the source and the relay which transmits to the destination, inter-relay interference arises. The efficient mitigation of inter-relay interference either through cancellation or avoidance, requires increased channel state information. Thus, in order to reduce the implementation complexity induced by centralized selection, distributed switch-and-stay combining is combined with buffer-aided successive opportunistic relaying. In this way, by applying a rate threshold we can avoid increased relay-pair switching and channel state information acquisition. The efficiency of the proposed scheme is demonstrated through simulations and comparisons with other state-of-the-art relay selection policies. I.
Hybrid Cooperation through Full-Duplex Opportunistic Relaying and Max-Link Relay Selection with Transmit Power Adaptation
"... Abstract—In this work, we study a cooperative network with multiple full-duplex buffer-aided relays. A hybrid cooperative relaying policy is proposed that employs power adaptation and consists of two alternative schemes: (i) full-duplex transmission through the relay which requires the least total p ..."
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Abstract—In this work, we study a cooperative network with multiple full-duplex buffer-aided relays. A hybrid cooperative relaying policy is proposed that employs power adaptation and consists of two alternative schemes: (i) full-duplex transmission through the relay which requires the least total power expendi-ture and loop interference is mitigated through power adaptation; (ii) buffer-aided max − link selection with power adaptation, when full-duplexity is not feasible. Aiming to reduce the overhead of channel state information (CSI) acquisition and processing, we propose a suboptimal distributed method for relay selection, for which the network performance is not degraded significantly. We show that power adaptation offers reduced overhead of CSI acquisition. Numerical results and comparisons with other state-of-the-art relaying schemes are provided and performance evaluation in terms of throughput, power minimization and switching rate, show the benefits of the proposed hybrid scheme. Index Terms—Cooperative networks, full-duplex, opportunistic relaying, buffer-aided relays, hybrid relay selection. I.
Buffer-Aided Relaying for Two-Hop Secure Communication
"... Abstract—We consider using a buffer-aided relay to enhance security for two-hop half-duplex relay networks with an external eavesdropper. We propose a link selection scheme that adapts reception and transmission time slots based on channel quality, while considering both the two-hop transmission eff ..."
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Abstract—We consider using a buffer-aided relay to enhance security for two-hop half-duplex relay networks with an external eavesdropper. We propose a link selection scheme that adapts reception and transmission time slots based on channel quality, while considering both the two-hop transmission efficiency and security. Closed-form expressions for the secrecy throughput and the secrecy outage probability (SOP) are derived, and the selection parameters are optimized to maximize the secrecy throughput or minimize the SOP. We then analyze two sub-optimal link selection schemes that in general only require a line search to solve the optimization problem, and we show that, under certain conditions, these approaches also admit closed-form solutions. All schemes are discussed in the context of two different scenarios where the relay either knows or does not know the channel to the legiti-mate receiver. In the former case, the relay adopts adaptive-rate transmission, whereas for the latter, it uses fixed-rate transmis-sion. Numerical results show that buffer-aided relaying provides a significant improvement in security compared with conventional unbuffered relaying. Furthermore, the performance of the sub-optimal schemes is shown to approach the optimal one for certain ranges of signal-to-noise-ratio (SNR) or SOP constraints. Index Terms—Buffered relay, wiretap channel, physical layer security, outage probability, relay networks. I.
1A Buffer-aided Successive Opportunistic Relay Selection Scheme with Power Adaptation and Inter-Relay Interference Cancellation for Cooperative Diversity Systems
"... Abstract—In this paper, we present a relay selection scheme which combines the spectral efficiency of successive opportunistic relaying with the robustness of single-link relay selection. More specifically, we propose a scheme that minimizes the total energy expenditure per time slot under an inter- ..."
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Abstract—In this paper, we present a relay selection scheme which combines the spectral efficiency of successive opportunistic relaying with the robustness of single-link relay selection. More specifically, we propose a scheme that minimizes the total energy expenditure per time slot under an inter-relay interference cancellation scheme. The new relay selection policy is analyzed in terms of outage probability and diversity by modeling the evolution of relay buffers as a Markov Chain. We construct the state transition matrix of the Markov Chain and obtain its stationary distribution, which in turn, yields the outage proba-bility. The proposed scheme outperforms relevant state-of-the-art relay selection schemes in terms of throughput, diversity, energy efficiency and average delay, as demonstrated via representative numerical examples. Index Terms—Cooperative relaying, relay selection, power minimization, inter-relay interference, Markov Chains. I.
1Modeling Buffer-Aided Relay Selection in Networks with Direct Transmission Capability
"... Abstract—We consider a wireless relay network that consists of a source, half-duplex decode-and-forward buffer-aided relays and a destination. While the majority of previous works on relay selection assume no direct transmission between source and destination in such a setting, we lift this assumpti ..."
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Abstract—We consider a wireless relay network that consists of a source, half-duplex decode-and-forward buffer-aided relays and a destination. While the majority of previous works on relay selection assume no direct transmission between source and destination in such a setting, we lift this assumption and propose a link selection policy that exploits both the buffering ability and the opportunity for successful reception of a packet directly from the source. The proposed relay selection scheme incorporates the instantaneous strength of the wireless links and adapts the relay selection decision based on the strongest available link. The evolution of the network as a whole is modeled by means of a Markov chain and thus, the outage probability is associated with the steady state of the Markov chain. It is deduced that even if the link between the source and the destination is in principle a very unreliable link, it is always beneficial for the source to multicast a packet to both the relay with the strongest available link and the destination. Index Terms—Cooperative networks, relay channel, buffer-aided relays, direct transmissions, outage probability. I.
