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FemtoCaching: Wireless Video Content Delivery through Distributed Caching Helpers,” submitted for publication, available on http://arxiv.org/pdf/1109.4179v1
"... Abstract—We suggest a novel approach to handle the ongoing explosive increase in the demand for video content in mobile devices. We envision femtocelllike base stations, which we call helpers, with weak backhaul links but large storage capabilities. These helpers form a wireless distributed caching ..."
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Cited by 56 (9 self)
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Abstract—We suggest a novel approach to handle the ongoing explosive increase in the demand for video content in mobile devices. We envision femtocelllike base stations, which we call helpers, with weak backhaul links but large storage capabilities. These helpers form a wireless distributed caching network that assists the macro base station by handling requests of popular files that have been cached. We formalize the wireless distributed caching optimization problem for the case that files are encoded using fountain/MDS codes. We express the problem as a convex optimization. By adding additional variables we reduce it to a linear program. On the practical side, we present a detailed simulation of a university campus scenario covered by a single 3GPP LTE R8 cell and several helper nodes using a simplified 802.11n protocol. We use a real campus trace of video requests and show how distributed caching can increase the number of served users by as much as 600 − 700%. I.
Index coding: An interference alignment perspective
 in International Symposium on Information Theory
, 2012
"... The index coding problem is studied from an interference alignment perspective providing new results as well as new insights into, and generalizations of, previously known results. An equivalence is established between the capacity of the multiple unicast index coding (where each message is desired ..."
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Cited by 33 (9 self)
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The index coding problem is studied from an interference alignment perspective providing new results as well as new insights into, and generalizations of, previously known results. An equivalence is established between the capacity of the multiple unicast index coding (where each message is desired by exactly one receiver), and groupcast index coding (where a message can be desired by multiple receivers), which settles the heretofore open question of insufficiency of linear codes for the multiple unicast index coding problem by equivalence with groupcast settings where this question has previously been answered. Necessary and sufficient conditions for the achievability of rate half per message in the index coding problem are shown to be a natural consequence of interference alignment constraints, and generalizations to feasibility of rate 1 L+1 per message when each destination desires at least L messages, are similarly obtained. Finally, capacity optimal solutions are presented to a series of symmetric index coding problems inspired by the local connectivity and local interference characteristics of wireless networks. The solutions are based on vector linear coding.
Topological interference management through index coding
, 2013
"... While much recent progress on interference networks has come about under the assumption of abundant channel state information at the transmitters (CSIT), a complementary perspective is sought in this work through the study of interference networks with no CSIT except a coarse knowledge of the topolo ..."
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Cited by 30 (14 self)
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While much recent progress on interference networks has come about under the assumption of abundant channel state information at the transmitters (CSIT), a complementary perspective is sought in this work through the study of interference networks with no CSIT except a coarse knowledge of the topology of the network that only allows a distinction between weak and significant channels and no further knowledge of the channel coefficients ’ realizations. Modeled as a degreesoffreedom (DoF) study of a partially connected interference network with no CSIT, the problem is found to have a counterpart in the capacity analysis of wired networks with arbitrary linear network coding at intermediate nodes, under the assumption that the sources are aware only of the end to end topology of the network. The wireless (wired) network DoF (capacity) region, expressed in dimensionless units as a multiple of the DoF (capacity) of a single point to point channel (link), is found to be bounded above by the capacity of an index coding problem where the antidotes graph is the complement of the interference graph of the original network and the bottleneck link capacity is normalized to unity. The problems are shown to be equivalent under linear solutions over the same field. An interference alignment
Bipartite index coding
 in Proc. IEEE Int. Symp. Inf. Theory
, 2012
"... Abstract—We analyze a generalized index coding problem that allows multiple users to request the same packet. For this problem we introduce a novel coding scheme called partition multicast. Our scheme can be seen as a natural generalization of clique cover for directed index coding problems. Further ..."
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Cited by 16 (3 self)
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Abstract—We analyze a generalized index coding problem that allows multiple users to request the same packet. For this problem we introduce a novel coding scheme called partition multicast. Our scheme can be seen as a natural generalization of clique cover for directed index coding problems. Further, partition multicast corresponds to an achievable scheme for the generalized bipartite index coding problem that we introduce in this paper. Our scheme partitions the nodes into groups and solves a multicasting problem within each group. We show that Partition Multicast is optimal for a few families of graphs and generalizes previous achievable schemes, namely directed cycle covers. We also show that finding the best partition is computationally intractable to compute in general. I.
On the Complementary Index Coding Problem
 in Information Theory Proceedings (ISIT), 2011 IEEE International Symposium on, 2011
"... Abstract—The Index Coding problem is one of the basic problems in wireless network coding. In this problem, a server needs to deliver a set P of packets to several clients through a noiseless broadcast channel. Each client needs to obtain a certain subset of P and has prior side information about a ..."
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Cited by 14 (0 self)
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Abstract—The Index Coding problem is one of the basic problems in wireless network coding. In this problem, a server needs to deliver a set P of packets to several clients through a noiseless broadcast channel. Each client needs to obtain a certain subset of P and has prior side information about a different subset of P. The objective is to satisfy the requirements of all clients with the minimum number of transmissions. Recently, it was shown that the Index Coding problem is NPhard. Furthermore, this problem was shown to be hard to approximate under a widely accepted complexity assumption. In this paper, we consider a complementary problem whose goal is to maximize the number of saved transmissions, i.e., the number of transmissions that are saved by combining packets compared to the solution that does not involve coding. We refer to this problem as the the Complementary Index Coding problem. It turns out that the complementary problem can be approximated in certain cases of practical importance. We consider the multiple unicast and multiple multicast scenarios. In the multiple unicast scenario, each packet is requested by a single client; while in the multiple multicast scenario, each packet can be requested by several clients. For the multiple unicast scenario, we present approximation algorithms for finding scalar and vector linear solutions. For the multiple multicast scenario, we show that finding an approximation solution is NPhard. I.
On the capacity region for index coding
 IN PROC. IEEE INT. SYMP. INF. THEORY
, 2013
"... A new inner bound on the capacity region of the general index coding problem is established. Unlike most existing bounds that are based on graph theoretic or algebraic tools, the bound relies on a random coding scheme and optimal decoding, and has a simple polymatroidal singleletter expression. Th ..."
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Cited by 13 (5 self)
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A new inner bound on the capacity region of the general index coding problem is established. Unlike most existing bounds that are based on graph theoretic or algebraic tools, the bound relies on a random coding scheme and optimal decoding, and has a simple polymatroidal singleletter expression. The utility of the inner bound is demonstrated by examples that include the capacity region for all index coding problems with up to five messages (there are 9846 nonisomorphic ones).
Dynamic index coding for wireless broadcast networks. ArXiv
, 2011
"... Abstract — We consider a wireless broadcast station that transmits packets to multiple users. The packet requests for each user may overlap, and some users may already have certain packets. This presents a problem of broadcasting in the presence of side information, and is a generalization of the w ..."
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Cited by 10 (3 self)
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Abstract — We consider a wireless broadcast station that transmits packets to multiple users. The packet requests for each user may overlap, and some users may already have certain packets. This presents a problem of broadcasting in the presence of side information, and is a generalization of the well known (and unsolved) index coding problem of information theory. Rather than achieving the full capacity region, we develop a codeconstrained capacity region, which restricts attention to a prespecified set of coding actions. We develop a dynamic maxweight algorithm that allows for random packet arrivals and supports any traffic inside the codeconstrained capacity region. Further, we provide a simple set of codes based on cycles in the underlying demand graph. We show these codes are optimal for a class of broadcast relay problems. I.
Polar Codes for Broadcast Channels
, 2013
"... Polar codes are introduced for discrete memoryless broadcast channels. For muser deterministic broadcast channels, polarization is applied to map uniformly random message bits from m independent messages to one codeword while satisfying broadcast constraints. The polarizationbased codes achieve ra ..."
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Cited by 10 (1 self)
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Polar codes are introduced for discrete memoryless broadcast channels. For muser deterministic broadcast channels, polarization is applied to map uniformly random message bits from m independent messages to one codeword while satisfying broadcast constraints. The polarizationbased codes achieve rates on the boundary of the privatemessage capacity region. For twouser noisy broadcast channels, polar implementations are presented for two informationtheoretic schemes: i) Cover’s superposition codes; ii) Marton’s codes. Due to the structure of polarization, constraints on the auxiliary and channelinput distributions are identified to ensure proper alignment of polarization indices in the multiuser setting. The codes achieve rates on the capacity boundary of a few classes of broadcast channels (e.g., binaryinput stochastically degraded). The complexity of encoding and decoding is O(nlogn) where n is the block length. In addition, polar code sequences obtain a stretchedexponential decay of O(2−nβ) of the average block error probability where 0 < β < 1 2. Reproducible experiments for finite block
Optimal index codes with nearextreme rates
 in Proc. IEEE Int. Symp. Inf. Theory
, 2012
"... Abstract—The minrank of a digraph was shown by BarYossef et al. (2006) to represent the length of an optimal scalar linear solution of the corresponding instance of the Index Coding with Side Information (ICSI) problem. In this work, the graphs and digraphs of nearextreme minranks are characteri ..."
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Cited by 8 (0 self)
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Abstract—The minrank of a digraph was shown by BarYossef et al. (2006) to represent the length of an optimal scalar linear solution of the corresponding instance of the Index Coding with Side Information (ICSI) problem. In this work, the graphs and digraphs of nearextreme minranks are characterized. Those graphs and digraphs correspond to the ICSI instances having nearextreme transmission rates when using optimal scalar linear index codes. It is also shown that the decision problem of whether a digraph has minrank two is NPcomplete. By contrast, the same question for graphs can be answered in polynomial time. I.
Rouayheb, “Deterministic Algorithm for Coded Cooperative Data Exchange
 In Proc. of the QShine
, 2010
"... Abstract. We consider the problem of cooperative data exchange in a group of wireless clients. In this problem each client initially holds a subset of packets and needs to obtain all packets held by other clients. Each client can broadcast its own packets or a combinations thereof to other clients v ..."
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Cited by 8 (3 self)
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Abstract. We consider the problem of cooperative data exchange in a group of wireless clients. In this problem each client initially holds a subset of packets and needs to obtain all packets held by other clients. Each client can broadcast its own packets or a combinations thereof to other clients via an errorfree broadcast channel. Assuming that clients know which packets are available to other clients, our goal is to minimize the total number of transmissions needed to satisfy the demands of all clients. We present a deterministic algorithm that computes an optimal solution to this problem in polynomial time. 1