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17
Coalitions in cooperative wireless networks
, 2008
"... Cooperation between rational users in wireless networks is studied using coalitional game theory. Using the rate achieved by a user as its utility, it is shown that the stable coalition structure, i.e., set of coalitions from which users have no incentives to defect, depends on the manner in which ..."
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Cited by 13 (0 self)
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Cooperation between rational users in wireless networks is studied using coalitional game theory. Using the rate achieved by a user as its utility, it is shown that the stable coalition structure, i.e., set of coalitions from which users have no incentives to defect, depends on the manner in which the rate gains are apportioned among the cooperating users. Specifically, the stability of the grand coalition (GC), i.e., the coalition of all users, is studied. Transmitter and receiver cooperation in an interference channel (IC) are studied as illustrative cooperative models to determine the stable coalitions for both flexible (transferable) andfixed (nontransferable) apportioning schemes. It is shown that the stable sumrate optimal coalition when only receivers cooperate by jointly decoding (transferable) is the GC. The stability of the GC depends on the detector when receivers cooperate using linear multiuser detectors (nontransferable). Transmitter cooperation is studied assuming that all receivers cooperate perfectly and that users outside a coalition act as jammers. The stability of the GC is studied for both the case of perfectly cooperating transmitters (transferrable) and under a partial decodeandforward strategy (nontransferable). In both cases, the stability is shown to depend on the channel gains and the transmitter jamming strengths.
The impact of CSI and power allocation on relay channel capacity and cooperation strategies
 IEEE Trans. Inform. Theory
"... Capacity gain from transmitter and receiver cooperation are compared in a relay network where the cooperating nodes are close together. Under quasistatic channels, when all nodes have equal average transmit power along with full channel state information (CSI), it is shown that transmitter cooperat ..."
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Cited by 8 (1 self)
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Capacity gain from transmitter and receiver cooperation are compared in a relay network where the cooperating nodes are close together. Under quasistatic channels, when all nodes have equal average transmit power along with full channel state information (CSI), it is shown that transmitter cooperation outperforms receiver cooperation, whereas the opposite is true when power is optimally allocated among the cooperating nodes but only CSI at the receiver (CSIR) is available. When the nodes have equal power with CSIR only, cooperative schemes are shown to offer no capacity improvement over noncooperation under the same network power constraint. When the system is under optimal power allocation with full CSI, the decodeandforward transmitter cooperation rate is close to its cutset capacity upper bound, and outperforms compressandforward receiver cooperation. Under Rayleigh fading in the high SNR regime, similar conclusions follow. Cooperative systems provide resilience to channel fading; however, capacity becomes more sensitive to power allocation, and the cooperating nodes need to be closer together for the decodeandforward scheme to be capacityachieving. Moreover, to realize capacity improvement, full CSI is necessary in transmitter cooperation, while in receiver cooperation optimal power allocation is essential. Index Terms Capacity, transmitter cooperation, receiver cooperation, channel state information (CSI), power allocation, relay channel.
When network coding and dirty paper coding meet in a cooperative ad hoc network
 IEEE Trans. Wireless Commun
, 2008
"... Abstract — We develop and analyze new cooperative strategies for ad hoc networks that are more spectrally efficient than classical DF cooperative protocols. Using analog network coding, our strategies preserve the practical halfduplex assumption but relax the orthogonality constraint. The introduct ..."
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Cited by 6 (1 self)
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Abstract — We develop and analyze new cooperative strategies for ad hoc networks that are more spectrally efficient than classical DF cooperative protocols. Using analog network coding, our strategies preserve the practical halfduplex assumption but relax the orthogonality constraint. The introduction of interference due to nonorthogonality is mitigated thanks to precoding, in particular Dirty Paper coding. Combined with smart power allocation, our cooperation strategies allow to save time and lead to more efficient use of bandwidth and to improved network throughput with respect to classical RDF/PDF. I.
Message and State Cooperation in Multiple Access Channels
"... Abstract—We investigate the capacity of a multiple access channel with cooperating encoders where partial state information is known to each encoder and full state information is known to the decoder. The cooperation between the encoders has a twofold purpose: to generate empirical state coordinati ..."
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Cited by 5 (0 self)
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Abstract—We investigate the capacity of a multiple access channel with cooperating encoders where partial state information is known to each encoder and full state information is known to the decoder. The cooperation between the encoders has a twofold purpose: to generate empirical state coordination between the encoders, and to share information about the private messages that each encoder has. For twoway cooperation, this twofold purpose is achieved by doublebinning, where the first layer of binning is used to generate the state coordination similarly to the twoway source coding, and the second layer of binning is used to transmit information about the private messages. The complete result provides the framework and perspective for addressing a complex level of cooperation that mixes states and messages in an optimal way. Index Terms—Channel state information, cooperating encoders, coordination, doublebinning, messagestate cooperation, multiple access channel, superbin. I.
Relayassisted interference network: Degrees of freedom
 IEEE Transactions on Information Theory, accepted
"... Abstract—This paper investigates the degrees of freedom of the interference channel in the presence of a dedicated multipleinput multipleoutput (MIMO) relay. The relay is used to manage the interference at the receivers. It is assumed that all nodes including the relay have channel state informati ..."
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Cited by 3 (0 self)
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Abstract—This paper investigates the degrees of freedom of the interference channel in the presence of a dedicated multipleinput multipleoutput (MIMO) relay. The relay is used to manage the interference at the receivers. It is assumed that all nodes including the relay have channel state information only for their own links and that the relay has antennas in auser network. We pose the question: what is the benefit of exploiting the direct links from the source to destinations compared to a simpler twohop strategy. To answer this question, we first establish the degrees of freedom of the interference channel with an MIMO relay, showing that apair network with an MIMO relay has 2 degrees of freedom. Thus, appropriate signaling in a twohop scenario captures the degrees of freedom without the need for the direct links. We then consider more sophisticated encoding strategies in search of other ways to exploit the direct links. Using a number of hybrid encoding strategies, we obtain nonasymptotic achievable sum rates. We investigate the case where the relay (unlike other nodes) has access to abundant power, showing that when sources have power and the relay is allowed power proportional to ( 2), the full degrees of freedom are available to the network. Index Terms—Degrees of freedom (DOF), interference channel (IFC), relay channel, wireless networks. I.
On the Symmetric Gaussian Interference Channel with Partial Unidirectional Cooperation
, 2009
"... A twouser symmetric Gaussian Interference Channel (IC) is considered in which a noiseless unidirectional link connects one encoder to the other. Having a constant capacity, the additional link provides partial cooperation between the encoders. It is shown that the available cooperation can dramatic ..."
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Cited by 2 (0 self)
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A twouser symmetric Gaussian Interference Channel (IC) is considered in which a noiseless unidirectional link connects one encoder to the other. Having a constant capacity, the additional link provides partial cooperation between the encoders. It is shown that the available cooperation can dramatically increase the sumcapacity of the channel. This fact is proved based on comparison of proposed lower and upper bounds on the sumcapacity. Partitioning the data into three independent messages, namely private, common, and cooperative ones, the transmission strategy used to obtain the lower bound enjoys a simple type of HanKobayashi scheme together with a cooperative communication scheme. A Genieaided upper bound is developed which incorporates the capacity of the cooperative link. Other upper bounds are based on the sumcapacity of the Cognitive Radio Channel and cutset bounds. For the strong interference regime, the achievablity scheme is simplified to employ common and/or cooperative messages but not the private one. Through a careful analysis it is shown that the gap between these bounds is at most one and two bits per real dimension for strong and weak interference regimes, respectively. Moreover, the Generalized DegreesofFreedom of the channel is characterized.
PRACTICAL COMPRESSANDFORWARD COOPERATION FOR THE CLASSICAL RELAY NETWORK
"... This paper proposes a practical compressandforward cooperation scheme with vector coding at the relay node for a threeterminal classical relay network. We discuss the framework of the relay receiver and analyse two practical vector coding algorithms for the cooperation, nearest neighbour quantiza ..."
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This paper proposes a practical compressandforward cooperation scheme with vector coding at the relay node for a threeterminal classical relay network. We discuss the framework of the relay receiver and analyse two practical vector coding algorithms for the cooperation, nearest neighbour quantization and lattice vector quantization. The error rate performance of the compressandforward cooperation and some other protocols under different SNRs is investigated. The impact of the quantization rate at the relay node is also characterised. It is shown that for a quantization rate larger than 2 bits/sample, the vector coding whether employing nearest neighbour quantization or lattice vector quantization, outerforms both the decodeandforward protocol and scalar coding. 1.
Cooperation and Optimal . . .
, 2007
"... In wireless networks, we can improve system performance by exploiting cooperative communications, where neighbor nodes may interact to jointly encode, decode, or relay information. In this thesis, we show that cooperation can improve capacity, but only when the right cooperation strategy is chosen b ..."
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In wireless networks, we can improve system performance by exploiting cooperative communications, where neighbor nodes may interact to jointly encode, decode, or relay information. In this thesis, we show that cooperation can improve capacity, but only when the right cooperation strategy is chosen based on the network topology, signaltonoise ratio (SNR), channel state information (CSI), and power allocation assumptions. In particular, when we consider the deployment of relay nodes in a wireless network, CSI at the transmitter is necessary for effective transmitter cooperation, while transmission power allocation between the cooperating nodes is crucial for receiver cooperation. The benefits of cooperation are further studied when the relay and receiver can iterate to exchange information over orthogonal, finitecapacity channels known as conference links. We show that a tworound iterative decoding scheme can achieve a higher capacity over noniterative cooperation. This thesis also investigates crosslayer resource allocation where network resources such
Resource Allocation and Relay Selection for Collaborative Communications 1
, 2008
"... We investigate the relay selection problem for a decode and forward collaborative network. Users are able to collaborate; decode messages of each other, reencode and forward along with their own messages. We study the performance obtained from collaboration in terms of 1) increasing the achievable ..."
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We investigate the relay selection problem for a decode and forward collaborative network. Users are able to collaborate; decode messages of each other, reencode and forward along with their own messages. We study the performance obtained from collaboration in terms of 1) increasing the achievable rate, 2) saving the transmit energy and 3) reducing the resource requirement (resource means timebandwidth). To ensure fairness, we fix the transmitenergytorate ratio among all users. We allocate resource optimally for the collaborative protocol (CP), and compare the result with the noncollaborative protocol (NCP) where users transmits their messages directly. The collaboration gain is a function of the channel gain and available energies and allows us 1) to decide to collaborate or not, 2) to select one relay among the possible relay users, and 3) to determine the involved gain and loss of possible collaboration. A considerable gain can be obtained if the direct sourcedestination channel gain is significantly smaller than those of alternative involved links. We demonstrate that a rate and energy improvement of up to 1 + η