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Advances in Cognitive Radio Networks: A Survey
- IEEE JOURNAL OF SELECTED TOPICS IN SIGNAL PROCESSING
, 2011
"... With the rapid deployment of new wireless devices and applications, the last decade has witnessed a growing demand for wireless radio spectrum. However, the fixed spectrum assignment policy becomes a bottleneck for more efficient spectrum utilization, under which a great portion of the licensed spe ..."
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Cited by 105 (1 self)
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With the rapid deployment of new wireless devices and applications, the last decade has witnessed a growing demand for wireless radio spectrum. However, the fixed spectrum assignment policy becomes a bottleneck for more efficient spectrum utilization, under which a great portion of the licensed spectrum is severely under-utilized. The inefficient usage of the limited spectrum resources urges the spectrum regulatory bodies to review their policy and start to seek for innovative communication technology that can exploit the wireless spectrum in a more intelligent and flexible way. The concept of cognitive radio is proposed to address the issue of spectrum efficiency and has been receiving an increasing attention in recent years, since it equips wireless users the capability to optimally adapt their operating parameters according to the interactions with the surrounding radio environment. There have been many significant developments in the past few years on cognitive radios. This paper surveys recent advances in research related to cognitive radios. The fundamentals of cognitive radio technology, architecture of a cognitive radio network and its applications are first introduced. The existing works in spectrum sensing are reviewed, and important issues in dynamic spectrum allocation and sharing are investigated in detail.
1 Protocol Design and Throughput Analysis for Multi-user Cognitive Cooperative Systems
, 2009
"... This paper deals with protocol design for cognitive cooperative systems with many secondary users. In contrast with previous cognitive configurations, the channel model considered assumes a cluster of secondary users which perform both a sensing process for transmitting opportunities and can relay d ..."
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Cited by 28 (3 self)
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This paper deals with protocol design for cognitive cooperative systems with many secondary users. In contrast with previous cognitive configurations, the channel model considered assumes a cluster of secondary users which perform both a sensing process for transmitting opportunities and can relay data for the primary user. Appropriate relaying improves the throughput of the primary users and can increase the transmission opportunities for the cognitive users. Based on different multi-access protocols, the schemes investigated enable relaying either between the primary user and a selected secondary user or between two selected secondary users. This collaboration can be a simple distributed multipleinput single-output transmission of the primary data or a simultaneous transmission of primary and secondary data using dirty-paper coding (DPC). The parametrization of DPC as well as its combination with opportunistic relay selection yields an interesting trade-off between the primary and the secondary performance which is investigated by theoretical and simulation results under the perspective of a desired primary throughput. The proposed protocols are studied from a networking point of view and the stable throughput for primary and secondary users is derived based on the principles of queueing theory. Index Terms analysis.
Stability analysis and power optimization for energy harvesting cooperative networks
- IEEE Signal Process. Lett
, 2012
"... Abstract—In this letter, we investigate the effects of network-layer cooperation in a wireless three-node network with energy-harvesting nodes and bursty data traffic. By modelling energy har-vesting in each node as a queue (buffer) that stores the received energy, we study the interaction between d ..."
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Cited by 24 (5 self)
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Abstract—In this letter, we investigate the effects of network-layer cooperation in a wireless three-node network with energy-harvesting nodes and bursty data traffic. By modelling energy har-vesting in each node as a queue (buffer) that stores the received energy, we study the interaction between data and energy queues when only knowledge of the arrival rates is available. The max-imum stable throughput (in packets/slot) of the source as well as the required transmitted power for both a non-cooperative and an orthogonal decode-and-forward cooperative schemes are derived in closed-form. We prove that cooperation achieves a higher max-imum stable throughout than direct link for scenarios with poor energy arrival rates. Index Terms—Cooperative networks, energy harvesting, power optimization, stable throughput. I.
Buffer-aided relay selection for cooperative diversity systems without delay constraints
- IEEE Trans. Wireless Commun
, 2012
"... Abstract—In this paper, we study the relay selection problem for a finite buffer-aided decode-and-forward cooperative wireless network. A relay selection policy that fully exploits the flexibility offered by the buffering ability of the relay nodes in order to maximize the achieved diversity gain is ..."
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Cited by 16 (7 self)
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Abstract—In this paper, we study the relay selection problem for a finite buffer-aided decode-and-forward cooperative wireless network. A relay selection policy that fully exploits the flexibility offered by the buffering ability of the relay nodes in order to maximize the achieved diversity gain is investigated. This new 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. In order to analyse the new relay selection policy in terms of outage probability and diversity gain, a theoretical framework that models the evolution of the relay buffers as a Markov chain (MC) is introduced. The construction of the state transition matrix and the related steady state of the MC are studied and their impact on the derivation of the outage probability is investigated. 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. Index Terms—Cooperative networks, relay channel, buffers, relay selection, outage probability, Markov chain. I.
Stability Analysis for Cognitive Radio with Multi-Access Primary Transmission
"... Abstract—This letter analyzes the impact, from a networklayer perspective, of having a single cognitive radio transmitterreceiver pair share the spectrum with multiple primary users wishing to communicate to a single receiver in a multi-access channel (MAC). In contrast to previous work which assume ..."
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Cited by 16 (1 self)
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Abstract—This letter analyzes the impact, from a networklayer perspective, of having a single cognitive radio transmitterreceiver pair share the spectrum with multiple primary users wishing to communicate to a single receiver in a multi-access channel (MAC). In contrast to previous work which assumes a time division multi-access strategy, here, we assume the set of primary users simultaneously access the channel to deliver their packets to a common destination. We derive the symmetric stable throughput regions, consisting of maximal arrival rates for primary and secondary (or cognitive radio) users under two investigated protocols. The first protocol is a conventional MAC scheme where the primary and secondary nodes operate independenly. The second protocol corresponds to a multi-access relay channel (MARC) which exploits user cooperation between primary and secondary nodes. We prove that cooperation is beneficial in the considered MARC as it enables higher throughputs for both primary and secondary users. Index Terms—Cooperative diversity, cognitive radio, multiaccess relay channel, queueing theory. I.
Protocol-level Cooperation in Wireless Networks: Stable Throughput and Delay Analysis
"... Abstract—We study the impact of user cooperation in wireless networks on improving the stable throughput and delay performance. Specifically, we consider a multiaccess system in which a set of source users generate packets to deliver to a common destination. A cooperation strategy is proposed at the ..."
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Cited by 13 (9 self)
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Abstract—We study the impact of user cooperation in wireless networks on improving the stable throughput and delay performance. Specifically, we consider a multiaccess system in which a set of source users generate packets to deliver to a common destination. A cooperation strategy is proposed at the protocol level, where users with a better channel to the destination have the option to relay packets from users that are farther afield. For the case of erasure channels with single-packet reception, we derive the stable throughput regions under different multiple access policies based on such cooperation strategy. Then we prove that the stable throughput region of the cooperative system strictly contains the stable throughput region achieved without cooperation. We also assess the delay performance, and show that cooperation significantly reduces the delay of all users. Finally, we characterize the effect of inter-user channel quality on performance, and show that the gain in performance through cooperation increases as the channel quality improves. Our work offers an innovative perspective by implementing cooperation at the network protocol level, while taking into consideration of fading and attenuation at the physical layer as well as the nature of traffic burstiness in a network. 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.
Opportunistic multiple access for cognitive radio networks
- IEEE J. Sel. Areas Commun
, 2011
"... Abstract—In this paper, opportunistic multiple access to the under-utilized channel resources is investigated. Exploiting source burstiness, secondary cognitive nodes utilizes primary nodes ’ periods of silence to access the channel and transmit their packets. Cognitive relays could also make use of ..."
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Cited by 10 (5 self)
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Abstract—In this paper, opportunistic multiple access to the under-utilized channel resources is investigated. Exploiting source burstiness, secondary cognitive nodes utilizes primary nodes ’ periods of silence to access the channel and transmit their packets. Cognitive relays could also make use of these silence periods to offer spatial diversity without incurring bandwidth efficiency losses. First, we consider the cognitive cooperation protocol and propose two different relay assignment schemes. Comparison between the proposed schemes is carried out through a maximum stable throughput analysis of the network. Then, secondary nodes access to the remaining idle channel resources is investigated. Queueing theoretical analysis and numerical results reveal that despite the fact that relays occupy part of the idle resources to provide cooperation, secondary nodes surprisingly achieve higher throughput in the presence of relays. The rationale is that relays help primary nodes empty their queues at faster rates, therefore, secondary nodes observe increased access opportunities to the channel. Index Terms—Cooperative communications, cognitive radio, queuing theory, multiple access. I.
A.: Cooperation Above the Physical Layer: the Case of a Simple Network
- In: IEEE International Symposium on Information Theory, (to appear). Seoul, Korea
, 2009
"... Abstract—In this paper, we investigate the effects of “networklevel” cooperation in a wireless three-node network with packet erasure links. Cooperation is achieved through the relaying of packets from the node farthest away from the destination by the intermediate node. We consider both scheduled a ..."
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Cited by 9 (7 self)
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Abstract—In this paper, we investigate the effects of “networklevel” cooperation in a wireless three-node network with packet erasure links. Cooperation is achieved through the relaying of packets from the node farthest away from the destination by the intermediate node. We consider both scheduled access and random access, and compare the performance metrics of “stability region ” and “throughput region”. We observe that the throughput region depends on the priority choices at the relay node, and may or may not be equal to the stability region, which is shown to be independent of the priority choices. By contrast, in the non-cooperative random access system, the stability region and the throughput region are proved to be identical. Furthermore, if we apply network coding at the relay node, there is no improvement either in the stability region or in the throughput region over plain store-and-forward routing. I.
Optimal Random Access and Random Spectrum Sensing for an Energy Harvesting Cognitive Radio with and without Primary Feedback Leveraging
"... We consider a secondary user (SU) with energy harvesting capability. We design access schemes for the SU which incorporate random spectrum sensing and random access, and which make use of the primary automatic repeat request (ARQ) feedback. We study two problem-formulations. In the first problem-for ..."
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Cited by 8 (7 self)
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We consider a secondary user (SU) with energy harvesting capability. We design access schemes for the SU which incorporate random spectrum sensing and random access, and which make use of the primary automatic repeat request (ARQ) feedback. We study two problem-formulations. In the first problem-formulation, we characterize the stability region of the proposed schemes. The sensing and access probabilities are obtained such that the secondary throughput is maximized under the constraints that both the primary and secondary queues are stable. Whereas in the second problem-formulation, the sensing and access probabilities are obtained such that the secondary throughput is maximized under the stability of the primary queue and that the primary queueing delay is kept lower than a specified value needed to guarantee a certain quality of service (QoS) for the primary user (PU). We consider spectrum sensing errors and assume multipacket reception (MPR) capabilities. Numerical results show the enhanced performance of our proposed systems.
