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Multicast Capacity of Large Homogeneous Multihop Wireless Networks
"... Abstract—Most existing work on multicast capacity of large homogeneous networks is based on a simple model for wireless channel, namely the Protocol Model [12], [19], [22]. In this paper, we exploit a local capacity tool called arena which we introduced recently in order to render multicast accessib ..."
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Cited by 18 (0 self)
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Abstract—Most existing work on multicast capacity of large homogeneous networks is based on a simple model for wireless channel, namely the Protocol Model [12], [19], [22]. In this paper, we exploit a local capacity tool called arena which we introduced recently in order to render multicast accessible to analysis also under more realistic, and notably less pessimistic channel models. Through the present study we find three regimes of the multicast capacity (λm) for a homogeneous network depending on the ratio of terminals among the nodes of the network. We note that the upper bounds we establish under the more realistic channel assumptions are only � log(n) larger than the existing bounds. Further, we propose a multicast routing and time scheduling scheme to achieve the computed asymptotic bound over all channel models except the simple Protocol Model. To this end, we employ percolation theory among other analytical tools. Finally, we compute the multicast capacity of large mobile wireless networks. Comparing the result to the static case reveals that mobility increases the multicast capacity. However, the mobility gain decreases when increasing the number of terminals in a fixed size mobile network. I.
Performance of Fountain Codes in Collaborative Relay Networks
 IEEE Trans. Wireless Comm
, 2007
"... Cooperative communications, where parallel relays forward information to a destination node, can greatly improve the energy efficiency and latency in adhoc networks. However, current networks do not fully exploit its potential, as they only use traditional energyaccumulation, which is often used i ..."
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Cited by 13 (5 self)
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Cooperative communications, where parallel relays forward information to a destination node, can greatly improve the energy efficiency and latency in adhoc networks. However, current networks do not fully exploit its potential, as they only use traditional energyaccumulation, which is often used in conjunction with repetition coding or cooperative spacetime codes. In this paper, we show that the concept of mutualinformationaccumulation can be realized with the help of fountain codes, and leads to a lower energy expenditure and a lower transmission time than energy accumulation. We then provide an analysis of the performance of mutual information accumulation in relay networks with N relay nodes. We first analyze the quasisynchronuous scenario where the source stops transmitting and the relay nodes start transmitting after L relay nodes have successfully decoded the source data. We show that an optimum L exists and is typically on the order of 3 or 4. We also give closedform equations for the energy savings that can be achieved by the use of mutualinformationaccumulation at the receiver. We then analyze and provide bounds for an alternate scenario where each relay node starts its transmission to the destination as soon as it has decoded the source data, independent of the state of the other relay nodes. This approach further reduces the transmission time, because the transmission by the relay nodes helps the other relay nodes that are still receiving.
Cooperative relay networks using fountain codes
 IN PROC. GLOBECOM
, 2006
"... We investigate a cooperative communications scheme with N parallel relays, where both the transmissions from the source to the relays and from the relays to the destination use fountain codes. Receiver for codes can accumulate mutual information, while traditional energy collection methods, such as ..."
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Cited by 9 (6 self)
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We investigate a cooperative communications scheme with N parallel relays, where both the transmissions from the source to the relays and from the relays to the destination use fountain codes. Receiver for codes can accumulate mutual information, while traditional energy collection methods, such as repetition or cooperative spacetime codes, only accumulate energy. As a consequence, using fountain codes can reduce the total energy required for transmitting data from the source to the destination. We first analyze the scenario where the source stops transmitting and the relay nodes start transmitting after L relay nodes have successfully decoded the source data. We optimize L, and also give closedform equations for the energy savings that can be achieved by the use of mutualinformationcollection at the receiver instead of the traditional energycollection methods. We then analyze an alternate scenario where each relay node starts its transmission to the destination as soon as it has decoded the source data, and helps the other relay nodes that are still in reception mode. Doing so further reduces the total transmission time and energy consumption.
Hierarchical Beamforming for Large OneDimensional Wireless Networks
"... Abstract—We consider a wireless network with a large number of sourcedestination pairs distributed over a line. Under lineofsight propagation, this network has only one degree of freedom for communication. At high SNR, this one degree of freedom can be readily achieved by multihop relaying betwee ..."
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Cited by 1 (1 self)
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Abstract—We consider a wireless network with a large number of sourcedestination pairs distributed over a line. Under lineofsight propagation, this network has only one degree of freedom for communication. At high SNR, this one degree of freedom can be readily achieved by multihop relaying between nodes. At low SNR, however, the performance is determined by the power transfer in the network. We show that none of the existing architectures can achieve optimal capacity scaling. We develop a digital hierarchical beamforming architecture and show that it is scaling optimal. This result reveals a new regime for large wireless networks, where beamforming techniques are needed to achieve capacity. I.
Certified by..........................................................
, 2009
"... This thesis studies the problem of determining achievable rates in heterogeneous wireless networks. We analyze the impact of location, traffic, and service heterogeneity. Consider a wireless network with n nodes located in a square area of size n communicating with each other over Gaussian fading ch ..."
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This thesis studies the problem of determining achievable rates in heterogeneous wireless networks. We analyze the impact of location, traffic, and service heterogeneity. Consider a wireless network with n nodes located in a square area of size n communicating with each other over Gaussian fading channels. Location heterogeneity is modeled by allowing the nodes in the wireless network to be deployed in an arbitrary manner on the square area instead of the usual random uniform node placement. For traffic heterogeneity, we analyze the n × n dimensional unicast capacity region. For service heterogeneity, we consider the impact of multicasting and caching. This gives rise to the n × 2 n dimensional multicast capacity region and the 2 n × n dimensional caching capacity region. In each of these cases, we obtain an explicit informationtheoretic characterization of the scaling of achievable rates by providing a converse and a matching (in the scaling sense) communication architecture.