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Stability and Performance Issues of a Relay Assisted Multiple Access Scheme
"... Abstract—In this paper, we examine the operation of a node relaying packets from a number of users to a destination node. We assume that the relay does not have packets of its own, the traffic from the users is saturated and we have random access of the medium with slotted time. We study the impact ..."
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Abstract—In this paper, we examine the operation of a node relaying packets from a number of users to a destination node. We assume that the relay does not have packets of its own, the traffic from the users is saturated and we have random access of the medium with slotted time. We study the impact of the relay node on the throughput per user and the aggregate throughput for the group of users. We obtain analytical expressions for the arrival and service rate of the queue of the relay, the stability conditions and the average length of the queue. We quantify the above, analytically and through simulations, for different numbers of users and different transmission characteristics of the users and the relay and give the conditions under which there are significant advantages from the deployment of the relay. I.
Relay-Assisted Multiple Access With Full-Duplex Multi-Packet Reception
"... Abstract-The effect of full-duplex cooperative relaying in a random access multiuser network is investigated here. First, we model the self-interference incurred due to full-duplex operation, assuming multi-packet reception capabilities for both the relay and the destination node. Traffic at the so ..."
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Abstract-The effect of full-duplex cooperative relaying in a random access multiuser network is investigated here. First, we model the self-interference incurred due to full-duplex operation, assuming multi-packet reception capabilities for both the relay and the destination node. Traffic at the source nodes is considered saturated and the cooperative relay, which does not have packets of its own, stores a source packet that it receives successfully in its queue when the transmission to the destination has failed. We obtain analytical expressions for key performance metrics at the relay, such as arrival and service rates, stability conditions, and average queue length, as functions of the transmission probabilities, the self interference coefficient, and the links' outage probabilities. Furthermore, we study the impact of the relay node and the self-interference coefficient on the per-user and aggregate throughput, and the average delay per packet. We show that perfect self-interference cancelation plays a crucial role when the SINR threshold is small, since it may result to worse performance in throughput and delay comparing with the half-duplex case. This is because perfect self-interference cancelation can cause an unstable queue at the relay under some conditions.
On Opportunistic Cooperation for Maximizing the Stability Region With Multipacket Reception
"... Abstract. We investigate the composite effects of multipacket reception (MPR) and relaying capability in affecting the stability region of a wireless network. With a general MPR channel, a trade-off arises as to whether to activate the relay simultaneously with the source so that both transmissions ..."
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Abstract. We investigate the composite effects of multipacket reception (MPR) and relaying capability in affecting the stability region of a wireless network. With a general MPR channel, a trade-off arises as to whether to activate the relay simultaneously with the source so that both transmissions might be successful, or to let the relay remain silent to overhear the source’s transmission and then activate the cooperation. As such, we consider a two-user multiple-access system where the user with a better user-destination channel may act as the relay for the other. An opportunistic cooperation scheme through scheduling the relay’s transmission is proposed. By assuming bursty arrivals, the optimal scheduling probability for maximizing the stability region is characterized, and the corresponding stability region is derived. We show that after applying opportunistic scheduling, higher performance gains can be achieved over conventional cooperation. Moreover, the stability region of the opportunistic scheme may be convex under certain channel conditions.
Network-Level Cooperation for a 1 Multiple-Access Channel via Dynamic Decode-and-Forward
, 2009
"... In this paper, we investigate some cross-layer cooperative strategies for cognitive Time-Division Multiple-Access relay channels with bursty arrivals. The proposed schemes adopt an advanced physical (PHY) layer cooperation and an “intelligent ” cognitive network-layer cooperation in order to improve ..."
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In this paper, we investigate some cross-layer cooperative strategies for cognitive Time-Division Multiple-Access relay channels with bursty arrivals. The proposed schemes adopt an advanced physical (PHY) layer cooperation and an “intelligent ” cognitive network-layer cooperation in order to improve the stable throughput region of the system. In contrast to previously reported work, where relaying is only enabled on periods of source silence, here, we incorporate a Dynamic Decode-and-Forward (DDF) policy which allows relaying assistance also during the source transmission. The enhancement of cognitive relaying with DDF provides more cooperative opportunities which results in faster emptying of the user queues and higher stable throughput compared to the conventional approaches. In addition to this PHY-layer relaying, the cognitive cooperation is supported by an adaptive superposition scheme which allows the relay node to simultaneously forward packets from different users. We demonstrate that adaptive superposition can further increase the transmission opportunities and significantly improve the stable throughput region. The proposed schemes are studied from a networking perspective and their advantages are shown through both theoretical results and computer simulations.
1Relay-Assisted Multiple Access with Multi-Packet Reception Capability and Simultaneous Transmission and Reception
"... In this work we examine the operation of a node relaying packets from a number of users to a destination node. We assume multi-packet reception capabilities for the relay and the destination node. The relay node can transmit and receive at the same time, so the problem of self interference arises. T ..."
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In this work we examine the operation of a node relaying packets from a number of users to a destination node. We assume multi-packet reception capabilities for the relay and the destination node. The relay node can transmit and receive at the same time, so the problem of self interference arises. The relay does not have packets of its own and the traffic at the source nodes is considered saturated. The relay node stores a source packet that it receives successfully in its queue when the transmission to the destination node has failed. We obtain analytical expressions for the characteristics of the relay’s queue (such as arrival and service rate of the relay’s queue), the stability condition and the average length of the queue as functions of the probabilities of transmissions, the self interference coefficient and the outage probabilities of the links. We study the impact of the relay node and the self interference coefficient on the throughput per user-source as well as the aggregate throughput. I.
1Relay-assisted Multiple Access with Full-duplex Multi-Packet Reception
"... The effect of full-duplex cooperative relaying in a random access multiuser network is investigated here. First, we model the self-interference incurred due to full-duplex operation, assuming multi-packet reception capabilities for both the relay and the destination node. Traffic at the source nodes ..."
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The effect of full-duplex cooperative relaying in a random access multiuser network is investigated here. First, we model the self-interference incurred due to full-duplex operation, assuming multi-packet reception capabilities for both the relay and the destination node. Traffic at the source nodes is considered saturated and the cooperative relay, which does not have packets of its own, stores a source packet that it receives successfully in its queue when the transmission to the destination has failed. We obtain analytical expressions for key performance metrics at the relay, such as arrival and service rates, stability conditions, and average queue length, as functions of the transmission probabilities, the self interference coefficient, and the links ’ outage probabilities. Furthermore, we study the impact of the relay node and the self-interference coefficient on the per-user and aggregate throughput, and the average delay per packet. We show that perfect self-interference cancelation plays a crucial role when the SINR threshold is small, since it may result to worse performance in throughput and delay comparing with the half-duplex case. This is because perfect self-interference cancelation can cause an unstable queue at the relay under some conditions.
1The Benefits of Deploying a Second Relay in Multi-User Cooperative Wireless Systems: A Networking Perspective
"... In wireless networks relay nodes can be used to assist the users ’ transmissions to reach their destination. This communication scheme, examining relay cooperation from the physical layer perspective, has up to now yielded well-known results. This paper takes a different stance focusing on the netwo ..."
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In wireless networks relay nodes can be used to assist the users ’ transmissions to reach their destination. This communication scheme, examining relay cooperation from the physical layer perspective, has up to now yielded well-known results. This paper takes a different stance focusing on the network-level cooperation. Extending previous results for a single relay, here we investigate the benefits from the deployment of a second one. We assume that the two relays do not generate packets of their own, the users have saturated queues and that the communication employs random access to the medium with slotted time. We obtain analytical expressions for the arrival and service rates of the queues of the two relays and the stability conditions, under the collision channel. We investigate a model of the system, in which the users are divided into clusters, each being served by one relay, and show its advantages in terms of aggregate and throughput per user. We quantify the above, analytically for the case of the collision channel and through simulations for the case of Multi-Packet Reception (MPR), and we illustrate when the deployment of a second relay in the system yields significant advantages. I.
ABSTRACT Title of dissertation: CROSS-LAYER ASPECTS OF COGNITIVE WIRELESS NETWORKS
"... We study cognitive wireless networks from a cross-layer perspective, where we investigate the effects of the PHY layer parameters and enhancements on the MAC layer performance. We quantify the benefit of using sophisticated techniques such as cooperative communications and network coding in cognitiv ..."
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We study cognitive wireless networks from a cross-layer perspective, where we investigate the effects of the PHY layer parameters and enhancements on the MAC layer performance. We quantify the benefit of using sophisticated techniques such as cooperative communications and network coding in cognitive networks. The first part deals with unicast scenarios. We first study the problem of ran-dom access over time varying channels with cognitive nodes adjusting their access probabilities according to the decentralized channel state information they acquire at the PHY layer. We derive the conditions for our random access scheme to out-perform orthogonal access. We then study the case where a set of secondary users (SUs) opportunistically ac-cesses the primary user’s (PU) spectrum whenever it is idle. Since sensing errors are unavoidable, we study the effect of the interference from the SUs on the stable throughput of the PU. We then compute the range of the SUs ’ transmission param-eters that guarantees the stability of the PU queue. In order to balance the negative effects of the interference from the SUs, we propose a PHY layer relaying protocol
