logo EDITE Martina CARDONE
Identité
Martina CARDONE
État académique
Thèse soutenue le 2015-04-24
Sujet: Techniques de coopération appliquées aux futurs réseaux cellulaires
Direction de thèse:
Encadrement de thèse:
Laboratoire:
Voisinage
Ellipse bleue: doctorant, ellipse jaune: docteur, rectangle vert: permanent, rectangle jaune: HDR. Trait vert: encadrant de thèse, trait bleu: directeur de thèse, pointillé: jury d'évaluation à mi-parcours ou jury de thèse.
Productions scientifiques
oai:hal.archives-ouvertes.fr:hal-00875052
Gaussian Half-Duplex Relay Networks: Improved Gap and a Connection with the Assignment Problem
This paper studies a Gaussian relay network, where the relays can either transmit or receive at any given time, but not both. Known upper (cut-set) and lower (noisy network coding) bounds on the capacity of a memoryless full-duplex relay network are specialized to the half-duplex case and shown to be to within a constant gap of one another. For fairly broad range of relay network sizes, the derived gap is smaller than what is known in the literature, and it can be further reduced for more structured networks such as diamond networks. It is shown that the asymptotically optimal duration of the listen and transmit phases for the relays can be obtained by solving a linear program; the coefficients of the linear constraints of this linear program are the solution of certain 'assignment problems' for which efficient numerical routines are available; this gives a general interesting connection between the high SNR approximation of the capacity of a MIMO channel and the 'assignment problem' in graph theory. Finally, some results available for diamond networks are extended to general networks. For a general relay network with 2 relays, it is proved that, out of the 4 possible listen/transmit states, at most 3 have a strictly positive probability. Numerical results for a network with K − 2 < 9 relays show that at most K−1 states have a strictly positive probability, which is conjectured to be true for any number of relays.
IEEE Information Theory Workshopconference, seminar, workshop communication 2013-09-09
oai:hal.archives-ouvertes.fr:hal-00875049
Approximate Sum-Capacity of Full- and Half-Duplex Asymmetric Interference Channels with Unilateral Source Cooperation
This paper focuses on the causal cognitive radio channel. This model consists of a two-user Gaussian interference channel where a cooperative secondary/cognitive source can causally learn the message of a primary source through a noisy link. The generalized Degrees-of-Freedom (gDoF) and the sum- capacity to within a constant gap are characterized for channels where one destination does not experience interference, referred to as interference-asymmetric channels. Both cases where the cognitive source operates in full- and half-duplex mode are considered. The different models are compared among themselves and with the case of interference-symmetric channels with either bilateral or unilateral source cooperation. In particular, the parameter regimes where causal cognition, or unilateral cooperation, attains the same gDoF of classical channel models, such as the noncooperative interference channel and the non- causal cognitive channel, are identified in order to determine when causal cognitive radio offers benefits in practical systems.
Information Theory and Applications Workshop (ITA), 2013 Information Theory and Applications Workshopconference proceeding 2013-02-15
oai:hal.archives-ouvertes.fr:hal-00875051
Gaussian Half-Duplex Relay Channels: Generalized Degrees of Freedom and Constant Gap Result
This paper considers the Gaussian relay channel where the relay node operates in half-duplex mode. The exact capacity of the linear deterministic approximation of the Gaus- sian channel at high SNR is derived first. This result is then used to inspire an achievable scheme valid for any SNR in the original channel. The scheme is quite simple: it uses successive decoding and does not incur in the typical delay of backward decoding. The achievable rate is then showed to be at most 3 bits away from the cut-set upper bound, which allows to analytically determine the generalized Degrees-of-Freedom of the channel. A closed form expression for the gDoF-optimal fraction of time the relay node transmits is found as well.
IEEE International Conference on Communicationsconference, seminar, workshop communication 2013-06-09
oai:hal.archives-ouvertes.fr:hal-00875050
On the Interference Channel with Causal Cognition
This paper considers the causal cognitive interfer- ence channel that consists of two full-duplex transmitter-receiver pairs sharing the same channel, where one transmitter can causally learn the message of the other transmitter through a noisy link. This channel models unilateral source cooperation. The work focuses on the generalized degrees-of-freedom of the symmetric, i.e. the two interfering links and the two direct links have the same strength, sum-capacity for the Gaussian noise channel. It is shown through evaluation of various achievable schemes that known sum-rate upper-bounds are achievable to within a constant gap regardless of the strength of the channel parameters. The achievable schemes are quite simple in the sense that only superposition coding is used, while it is shown that more complex schemes using binning can achieve a smaller gap.
IEEE International Conference on Communications 2013conference, seminar, workshop communication 2013-06-09
oai:hal.archives-ouvertes.fr:hal-00875048
The Capacity to within a constant gap of the Gaussian Half-Duplex Relay Channel
This paper studies the Gaussian half duplex relay channel, where the relay node can not transmit and receive at the same time. The main contribution lies in showing that both Partial-Decode-Forward and Compress-Forward achieve the Cut- Set upper bound to within a constant gap regardless of the channel parameters. This provides a closed form characterization of the Generalized Degrees-of-Freedom (gDoF) of the channel, which for certain channel parameters is strictly smaller than the gDoF of the full duplex channel. Half duplex channels can convey information through the random switch between the receive and retransmit phases; this work shows numerically that random switch achieves larger rates compared to deterministic switch, which is usually considered in the literature.
Information Theory Proceedings (ISIT), 2013 IEEE International Symposium on IEEE International Symposium on Information Theoryconference proceeding 2013-07-12
oai:hal.archives-ouvertes.fr:hal-00875022
The symmetric sum-capacity of the Gaussian Half-Duplex Causal Cognitive Interference Channel to within a constant gap
This paper studies the sum-capacity of the Gaussian half-duplex causal cognitive interference channel, a channel model with two transmitter-receiver pairs where a (cognitive) source cooperates with the other (primary) source in sending data through a shared channel. In contrast to the classical cognitive radio model, here the cognitive source can not transmit and receive at the same time and must causally learn the primary message through a noisy channel. Achievable strategies are developed and shown to match known upper bounds on the symmetric sum-capacity of this channel to within a constant gap for all values of channel parameters. In the process, the generalized degrees of freedom of the channel is characterized.
Information Theory Proceedings (ISIT), 2013 IEEE International Symposium on IEEE International Symposium on Information Theoryconference proceeding 2013-07-12
oai:hal.archives-ouvertes.fr:hal-00981901
New Outer Bounds for the Interference Channel with Unilateral Source Cooperation
This paper studies the two-user interference channel with unilateral source cooperation, which consists of two source-destination pairs that share the same channel and where one full-duplex source can overhear the other source through a noisy in-band link. Novel outer bounds of the type 2R1 + R2 and R1 + 2R2 are developed for the class of injective semi-deterministic channels with independent noises at the different source-destination pairs. The bounds are then specialized to the Gaussian noise case. Interesting insights are provided about when these types of bounds are active, or in other words, when unilateral cooperation is too weak and leaves some system resources underutilized.
IEEE International Symposium on Information Theory (ISIT), 2014 IEEE International Symposium on Information Theory (ISIT), 2014conference proceeding 2014-07-07
oai:hal.archives-ouvertes.fr:hal-00981878
On the Gaussian Interference Channel with Unilateral Generalized Feedback
This paper studies the Gaussian interference channel with unilateral generalized feedback, a system where two source-destination pairs share the same channel and where one full-duplex source overhears the other through a noisy in-band link. A superposition coding scheme is shown to achieve a known outer bound to within a small number of bits for a subset of the weak interference regime, outside which more sophisticated coding techniques based on binning are conjectured to be needed. By using the generalized Degrees of Freedom (gDoF) as performance metric, unilateral generalized feedback is shown to strictly increase the gDoF region compared to the non-cooperative case only when the strength of the cooperation link is larger than a threshold, thus providing an indication on when cooperation among users is beneficial in practical wireless systems.
International Symposium on Communications, Control and Signal Processing (ISCCSP), 2014 International Symposium on Communications, Control and Signal Processing (ISCCSP), 2014conference proceeding 2014-05-26
oai:hal.archives-ouvertes.fr:hal-00981886
On the Capacity of Full-Duplex Causal Cognitive Interference Channels to within a Constant Gap
This paper considers the two-user Gaussian Causal Cognitive Interference Channel (GCCIC), which consists of two source-destination pairs that share the same channel and where one full-duplex cognitive source can causally learn the message of the primary source through a noisy link. The GCCIC is an interference channel with unilateral source cooperation that models practical cognitive radio networks. Different achievable strategies are shown to be at most a finite number of bits away from an outer bound for a set of the channel parameters that, roughly speaking, excludes the case of weak interference at both receivers.
IEEE International Conference on Communications (ICC), 2014 IEEE International Conference on Communications (ICC), 2014conference proceeding 2014-06-16
oai:hal.archives-ouvertes.fr:hal-00981963
On the Gaussian Interference Channel with Half-Duplex Causal Cognition
This paper studies the two-user Gaussian interference channel with half-duplex causal cognition. This channel model consists of two source-destination pairs sharing a common wireless channel. One of the sources, referred to as the cognitive, overhears the other source, referred to as the primary, through a noisy link and can therefore assist in sending the primary's data. Due to practical constraints, the cognitive source is assumed to work in half-duplex mode, that is, it cannot simultaneously transmit and receive. This model is more relevant for practical cognitive radio systems than the classical information theoretic cognitive channel model, where the cognitive source is assumed to have a non-causal knowledge of the primary's message. Different network topologies are considered, corresponding to different interference scenarios: (i) the interference-symmetric scenario, where both destinations are in the coverage area of the two sources and hence experience interference, and (ii) the interference-asymmetric scenario, where one destination does not suffer from interference. For each topology the sum-rate performance is studied by first deriving the generalized Degrees of Freedom (gDoF), or "sum-capacity pre-log" in the high-SNR regime, and then showing relatively simple coding schemes that achieve a sum-rate upper bound to within a constant number of bits for any SNR. Finally, the gDoF of the channel is compared to that of the non-cooperative interference channel and to that of the non-causal cognitive channel to identify the parameter regimes where half-duplex causal cognition is useless in practice or attains its ideal ultimate limit, respectively.
preprint 2014-04-23
oai:hal.archives-ouvertes.fr:hal-00981981
On the Capacity of the Two-user Gaussian Causal Cognitive Interference Channel
This paper considers the two-user Gaussian Causal Cognitive Interference Channel (GCCIC), which consists of two source-destination pairs that share the same channel and where one full-duplex cognitive source can causally learn the message of the primary source through a noisy link. The GCCIC is an interference channel with unilateral source cooperation that better models practical cognitive radio networks than the commonly used model which assumes that one source has perfect non-causal knowledge of the other source's message. First the sum-capacity of the symmetric GCCIC is determined to within a constant gap. Then, the insights gained from the study of the symmetric GCCIC are extended to more general cases. In particular, the whole capacity region of the Gaussian Z-channel, i.e., when there is no interference from the primary user, and of the Gaussian S-channel, i.e., when there is no interference from the secondary user, are both characterized to within 2 bits. The fully connected general, i.e., no-symmetric, GCCIC is also considered and its capacity region is characterized to within 2 bits when, roughly speaking, the interference is not weak at both receivers. The parameter regimes where the GCCIC is equivalent, in terms of generalized degrees-of-freedom, to the noncooperative interference channel (i.e., unilateral causal cooperation is not useful), to the non-causal cognitive interference channel (i.e., causal cooperation attains the ultimate limit of cognitive radio technology), and to bilateral source cooperation are identified. These comparisons shed lights into the parameter regimes and network topologies that in practice might provide an unbounded throughput gain compared to currently available (non cognitive) technologies.
preprint 2014-04-23
oai:hal.archives-ouvertes.fr:hal-00981991
On the Gaussian Half-Duplex Relay Channel
This paper considers the Gaussian half-duplex relay channel (G-HD-RC): a channel model where a source transmits a message to a destination with the help of a relay that can not transmit and receive at the same time. It is shown that the cut-set upper bound on the capacity can be achieved to within a constant gap, regardless of the actual value of the channel parameters, by either Partial-Decode-and-Forward or Compress-and-Forward. The performance of these coding strategies is evaluated with both random and deterministic switch at the relay. Numerical evaluations show that the actual gap is less than what analytically obtained, and that random switch achieves higher rates than deterministic switch. As a result of this analysis, the generalized Degrees-of-Freedom of the G-HD-RC is exactly characterized for this channel. In order to get insights into practical schemes for the G-HD-RC that are less complex than Partial-Decode-and-Forward or Compress-and-Forward, the exact capacity of the Linear Deterministic Approximation (LDA) of the G-HD-RC at high-SNR is determined. It is shown that random switch and correlated non-uniform inputs bits are optimal for the LDA. It is then demonstrated that deterministic switch is to within one bit from the capacity. This latter scheme is translated into a coding strategy for the original G-HD-RC and its optimality to within a constant gap is proved. The gap attained by this scheme is larger than that of Partial-Decode-and-Forward, thereby pointing to an interesting practical tradeoff between gap to capacity and complexity.
preprint 2014-04-23
oai:hal.archives-ouvertes.fr:hal-00981999
Gaussian Half-Duplex Relay Networks: Improved Constant Gap and Connections with the Assignment Problem
This paper considers a Gaussian relay network where a source transmits a message to a destination with the help of N half-duplex relays. The information theoretic cut-set 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 half-duplex multicast networks. It is then shown that the generalized Degrees-of-Freedom 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 transmit-receive 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 2^N=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 N-relay 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.
preprint 2014-04-23
Soutenance
Thèse: "Techniques de coopération appliquées aux futurs réseaux cellulaires"
Soutenance: 2015-04-24