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TwoUnicast Wireless Networks: Characterizing the DegreesofFreedom
, 2012
"... We consider twosource twodestination (i.e., twounicast) multihop wireless networks that have a layered structure with arbitrary connectivity. We show that, if the channel gains are chosen independently according to continuous distributions, then, with probability 1, twounicast layered Gaussi ..."
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Cited by 33 (9 self)
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We consider twosource twodestination (i.e., twounicast) multihop wireless networks that have a layered structure with arbitrary connectivity. We show that, if the channel gains are chosen independently according to continuous distributions, then, with probability 1, twounicast layered Gaussian networks can only have 1, 3/2 or 2 sum degreesoffreedom (unless both sourcedestination pairs are disconnected, in which case no degreesoffreedom can be achieved). We provide sufficient and necessary conditions for each case based on network connectivity and a new notion of sourcedestination paths with manageable interference. Our achievability scheme is based on forwarding the received signals at all nodes, except for a small fraction of them in at most two key layers. Hence, we effectively create a “condensed network” that has at most four layers (including the sources layer and the destinations layer). We design the transmission strategies based on the structure of this condensed network. The converse results are obtained by developing informationtheoretic inequalities that capture the structures of the network connectivity. Finally, we extend this result and characterize the full degreesoffreedom region of twounicast layered wireless networks.
Crosslayer Optimization for Wireless Networks with Deterministic Channel Models
"... Abstract—Existing work on crosslayer optimization for wireless networks adopts simple physicallayer models, i.e., treating interference as noise. In this paper, we adopt a deterministic channel model proposed in [11, 12], a simple abstraction of the physical layer that effectively captures the eff ..."
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Cited by 8 (4 self)
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Abstract—Existing work on crosslayer optimization for wireless networks adopts simple physicallayer models, i.e., treating interference as noise. In this paper, we adopt a deterministic channel model proposed in [11, 12], a simple abstraction of the physical layer that effectively captures the effect of channel strength, broadcast and superposition in wireless channels. Within the Network Utility Maximization (NUM) framework, we study the crosslayer optimization for wireless networks based on this deterministic channel model. First, we extend the wellapplied conflict graph model to capture the flow interactions over the deterministic channels and characterize the feasible rate region. Then we study distributed algorithms for general wireless multihop networks. The convergence of algorithms is proved by Lyapunov stability theorem and stochastic approximation method. Further, we show the convergence to the bounded neighborhood of optimal solutions with probability one under constant steps and constant update intervals. Our numerical evaluation validates the analytical results. I.
Capacity of Multiple Unicast in Wireless Networks: A Polymatroidal Approach
, 2011
"... A classical result in undirected wireline networks is the near optimality of routing (flow) for multipleunicast traffic (multiple sources communicating independent messages to multiple destinations): the min cut upper bound is within a logarithmic factor of the number of sources of the max flow. In ..."
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Cited by 2 (1 self)
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A classical result in undirected wireline networks is the near optimality of routing (flow) for multipleunicast traffic (multiple sources communicating independent messages to multiple destinations): the min cut upper bound is within a logarithmic factor of the number of sources of the max flow. In this paper we “extend” the wireline result to the wireless context. Our main result is the approximate optimality of a simple layering principle: local physicallayer schemes combined with global routing. We use the reciprocity of the wireless channel critically in this result. Our formal result is in the context of channel models for which “good ” local schemes, that achieve the cutset bound, exist (such as Gaussian MAC and broadcast channels, broadcast erasure networks, fast fading Gaussian networks). Layered architectures, common in the engineeringdesign of wireless networks, can have nearoptimal performance if the locality over which physicallayer schemes should operate is carefully designed. Feedback is shown to play a critical role in enabling the separation between the physical and the network layers. The key technical idea is the modeling of a wireless network by an undirected “polymatroidal” network, for which we establish a maxflow mincut approximation theorem.
SumCapacity of a Class of Kuser Gaussian Interference Channels within O(K) bits
"... Though the capacity of the 2user Gaussian interference channel has long eluded information theorists, recent progress has been made by focussing on approximations with provable bounds. However, extensions to a general Kuser network has proven to be nonobvious, in particular due to the role of in ..."
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Cited by 2 (0 self)
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Though the capacity of the 2user Gaussian interference channel has long eluded information theorists, recent progress has been made by focussing on approximations with provable bounds. However, extensions to a general Kuser network has proven to be nonobvious, in particular due to the role of interference alignment in these cases. In this paper, we look at a special case of a Kuser Gaussian interference network where only one of the users interferes with and is also interfered by all the other users. We determine the sumcapacity of such a network within O(K) bits for all possible values of the channel parameters, provided the direct signal is stronger than the receiver noise.
Sum DegreesofFreedom of TwoUnicast Wireless Networks
"... Abstract—We consider twosource twodestination (i.e., twounicast) multihop wireless networks that have a layered structure with arbitrary connectivity. We show that, if the channel gains are independently drawn from continuous distributions, then, with probability 1, twounicast layered Gaussian ..."
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Cited by 2 (1 self)
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Abstract—We consider twosource twodestination (i.e., twounicast) multihop wireless networks that have a layered structure with arbitrary connectivity. We show that, if the channel gains are independently drawn from continuous distributions, then, with probability 1, twounicast layered Gaussian networks can only have 1, 3/2 or 2 sum degreesoffreedom1. We provide necessary and sufficient conditions for each case based on the network topology and a new notion of sourcedestination paths with manageable interference. I.