Results 1 
9 of
9
CompressandForward Scheme for a Relay Network: Approximate Optimality and Connection to Algebraic Flows
 Proc. of IEEE ISIT
, 2011
"... We study a wireless relay network, with a single source and a single destination. Our main result is to show that an appropriate compressandforward scheme supports essentially the same reliable data rate as the quantizemapandforward and noisy network coding schemes [1, 2]; thus, it is approxima ..."
Abstract

Cited by 14 (1 self)
 Add to MetaCart
(Show Context)
We study a wireless relay network, with a single source and a single destination. Our main result is to show that an appropriate compressandforward scheme supports essentially the same reliable data rate as the quantizemapandforward and noisy network coding schemes [1, 2]; thus, it is approximately optimal – in the sense the data rate is a universal constant away from the cutset upper bound. We characterize the compressandforward scheme through an abstract flow formulation, a generalization of flow on linking systems. This characterization allows for efficient computation of the minimal amount of information that has to flow through each node in the network. We also generalize these results to the network with multiple sources with independent messages intended for a single destination; and to the broadcast network with a single source intending to communicate independent messages to multiple destinations. 1
Degrees of freedom of a class of nonlayered two unicast wireless networks,” Full paper in preparation
"... Abstract—Previous work showed that the fully connected layered 2L interference channel, i.e., the multihop interference network formed by concatenation of L − 1 2user interference channels, achieves the mincut outer bound value of 2 DoF. In this paper, we study the effects of nonlayered crosslay ..."
Abstract

Cited by 5 (2 self)
 Add to MetaCart
(Show Context)
Abstract—Previous work showed that the fully connected layered 2L interference channel, i.e., the multihop interference network formed by concatenation of L − 1 2user interference channels, achieves the mincut outer bound value of 2 DoF. In this paper, we study the effects of nonlayered crosslayer links on the fully connected layered 2L networks. In particular, we consider the 24 interference channel with arbitrary crosslayer connectivity. We show that the mincut outer bound value of 2 DoF can be always achieved (almost surely) except if there is a direct link from a source to its interfering destination. In this case, the DoF collapse to 1. I.
Distributed Decode–Forward for Multicast
"... Abstract—A new coding scheme for multicasting a message over a general relay network is presented that extends both network coding for graphical networks by Ahlswede, Cai, Li, and Yeung, and partial decode–forward for relay channels by Cover and El Gamal. For the Nnode Gaussian multicast network, ..."
Abstract

Cited by 2 (0 self)
 Add to MetaCart
(Show Context)
Abstract—A new coding scheme for multicasting a message over a general relay network is presented that extends both network coding for graphical networks by Ahlswede, Cai, Li, and Yeung, and partial decode–forward for relay channels by Cover and El Gamal. For the Nnode Gaussian multicast network, the scheme achieves within 0.5N bits from the capacity, improving upon the best known capacity gap results. The key idea is to use multicoding at the source as in Marton coding for broadcast channels. Instead of recovering a specific part of the message as in the original partial decode–forward scheme, a relay in the proposed distributed decode–forward scheme recovers an auxiliary index that implicitly carries some information about the message and forwards it in block Markov coding. This scheme can be adapted to broadcasting multiple messages over a general relay network, extending and refining a recent result by Kannan, Raja, and Viswanath. I.
Distributed decodeforward for broadcast,” Information Theory
 ISIT), 2014 IEEE International Symposium on
, 2014
"... Abstract—A new coding scheme for broadcasting multiple messages over a general relay network is presented. The proposed distributed decode–forward scheme combines Marton coding for singlehop broadcast channels and partial decode–forward for relay channels by Cover and El Gamal. For the Nnode Gau ..."
Abstract

Cited by 1 (0 self)
 Add to MetaCart
(Show Context)
Abstract—A new coding scheme for broadcasting multiple messages over a general relay network is presented. The proposed distributed decode–forward scheme combines Marton coding for singlehop broadcast channels and partial decode–forward for relay channels by Cover and El Gamal. For the Nnode Gaussian broadcast relay network, the scheme achieves within 0.5N bits from the capacity region, extending and refining a recent result by Kannan, Raja, and Viswanath. The main idea of the scheme is to precode all the codewords initially at the source and to decode and forward parts of them on the fly at the relays. I.
1Towards FullDuplex Multihop Multiflow — A Study of NonLayered Two Unicast Wireless Networks
"... Abstract—Starting from the elemental 2 2 2 interference channel, there has been much progress in the understanding of multihop multiflow wireless networks through degrees of freedom (DoF) studies that have produced important ideas such as (aligned) interference neutralization. However, much of thi ..."
Abstract
 Add to MetaCart
(Show Context)
Abstract—Starting from the elemental 2 2 2 interference channel, there has been much progress in the understanding of multihop multiflow wireless networks through degrees of freedom (DoF) studies that have produced important ideas such as (aligned) interference neutralization. However, much of this progress has been limited to layered connectivity models that are essentially motivated by the assumption that wireless networks can only operate in halfduplex mode. Motivated by recent breakthroughs in fullduplex radio technology, in this work we expand the 2 2 2 interference channel model beyond layered connectivity in order to study the impact of fullduplex operation. In particular we study the impact of intralayer connectivity between relays that are in the same layer, the impact of direct interlayer connectivity between sources and destinations, and the impact of intermediate interlayer connectivity that connects sources or destinations, not directly to each other, but to relay nodes in nonadjacent layers in a 2 2 2 2 interference channel. We show that intralayer links and intermediate interlayer interference links do not cause a collapse of DoF while direct interference links do cause a collapse of DoF. Index Terms—Capacity, degrees of freedom, fullduplex, interference neutralization, multihop multiflow I.
On feedback in Gaussian multihop networks
"... Abstract—The study of feedback has been mostly limited to singlehop communication settings. In this paper, we consider Gaussian networks where sources and destinations can communicate with the help of intermediate relays over multiple hops. We assume that links in the network can be bidirected pro ..."
Abstract
 Add to MetaCart
(Show Context)
Abstract—The study of feedback has been mostly limited to singlehop communication settings. In this paper, we consider Gaussian networks where sources and destinations can communicate with the help of intermediate relays over multiple hops. We assume that links in the network can be bidirected providing opportunities for feedback. We ask the following question: can the information transfer in both directions of a link be critical to maximizing the endtoend communication rates in the network? Equivalently, could one of the directions in each bidirected link (and more generally at least one of the links forming a cycle) be shut down and the capacity of the network still be approximately maintained? We show that in any arbitrary Gaussian network with bidirected edges and cycles, and unicast, multipleaccess or broadcast traffic, we can always identify a directed acyclic subnetwork that approximately maintains the capacity of the original network. On the other hand, with multicast and multiple unicast traffic bidirected flow across links can be critical to maximizing the endtoend capacity. I.
On UplinkDownlink Duality for Cellular IA
"... In our previous work [1], [2] we considered the uplink of a hexagonal cellular network topology and showed that linear “oneshot ” interference alignment (IA) schemes are able to achieve the optimal degrees of freedom (DoFs) per user, under a decodedmessage passing framework that allows basestatio ..."
Abstract
 Add to MetaCart
(Show Context)
In our previous work [1], [2] we considered the uplink of a hexagonal cellular network topology and showed that linear “oneshot ” interference alignment (IA) schemes are able to achieve the optimal degrees of freedom (DoFs) per user, under a decodedmessage passing framework that allows basestations to exchange their own decoded messages over local backhaul links. In this work, we provide the dual framework for the downlink of cellular networks with the same backhaul architecture, and show that for every “oneshot ” IA scheme that can achieve d DoFs per user in the uplink, there exists a dual “oneshot ” IA scheme that can achieve the same DoFs in the downlink. To enable “Cellular IA ” for the downlink, basestations will now use the same local backhaul links to exchange quantized versions of the dirtypaper precoded signals instead of user messages. I.
1Gaussian HalfDuplex Relay Networks: Improved Constant Gap and Connections with the Assignment Problem
"... Abstract—This paper considers a Gaussian relay network where a source transmits a message to a destination with the help of N halfduplex relays. The information theoretic cutset upper bound to the capacity is shown to be achieved to within 1.96(N + 2) bits by noisy network coding, thereby reducing ..."
Abstract
 Add to MetaCart
(Show Context)
Abstract—This paper considers a Gaussian relay network where a source transmits a message to a destination with the help of N halfduplex relays. The information theoretic cutset upper bound to the capacity is shown to be achieved to within 1.96(N + 2) bits by noisy network coding, thereby reducing the previously known gap. This gap is obtained as a special case of a more general constant gap result for Gaussian halfduplex multicast networks. It is then shown that the generalized DegreesofFreedom of this network is the solution of a linear program, where the coefficients of the linear inequality constraints are proved to be the solution of several linear programs referred as the assignment problem in graph theory, for which efficient numerical algorithms exist. The optimal schedule, that is, the optimal value of the 2N possible transmitreceive configuration states for the relays, is investigated and known results for diamond networks are extended to general relay networks. It is shown, for the case of N = 2 relays, that only N + 1 = 3 out of the 2N = 4 possible states have a strictly positive probability and suffice to characterize the capacity to within a constant gap. Extensive experimental results show that, for a general Nrelay network with N ≤ 8, the optimal schedule has at most N + 1 states with a strictly positive probability. As an extension of a conjecture presented for diamond networks, it is conjectured that this result holds for any HD relay network and any number of relays. Finally, a network with N = 2 relays is studied in detail to illustrate the channel conditions under which selecting the best relay is not optimal, and to highlight the nature of the rate gain due to multiple relays. Index Terms—Assignment problem, capacity to within a constant gap, generalized degreesoffreedom, halfduplex, inner bound, outer bound, relay networks, weighted bipartite matching problem. Eurecom’s research is partially supported by its industrial partners: BMW