The two-user broadcast channel (BC) with receivers connected by bidirectional cooperation links of finite capacities, known as conferencing decoders, is considered. A novel capacity region outer bound is established based on multiple applications of the Csiszár-Körner identity. Achievable rate regions are derived by using Marton’s coding as the transmission scheme, together with different combinations of decode-and-forward and quantize-bin-and-forward strategies at the receivers. It is shown that the outer bound coincides with the achievable rate region for a new class of semi-deterministic BCs with degraded message sets; for this class of channels, one-round cooperation is sufficient to achieve the capacity. Capacity result is also derived for a class of more capable semi-deterministic BCs with both common and private messages and one-sided conferencing. For the Gaussian BC with conferencing decoders, if the noises at the decoders are perfectly correlated (i.e., the correlation is either 1 or -1), the new outer bound yields exact capacity region for two cases: i) BC with degraded message sets; ii) BC with one-sided conferencing from the weaker receiver to the stronger receiver. When the noises have arbitrary correlation, the outer bound is shown to be within half a bit from the capacity region for these same two cases. Finally, for the general Gaussian BC, a one-sided cooperation scheme based on decode-and-forward from the stronger receiver to the weaker receiver is shown to achieve the capacity region to within 1/2 log(2/1-|λ|) bits, where λ is the noise correlation. An interesting implication of these results is that for a Gaussian BC with perfectly negatively correlated noises and conferencing decoders with finite cooperation link capacities, it is possible to achieve a strictly positive rate using only an infinitesimal amount of transmit power.

The two-user Gaussian broadcast channel (BC) with correlated noises and with decoders connected by cooperative links of finite capacities (known as conferencing decoders) is considered. A novel outer bound on the capacity region is established. For the channel with fully correlated noises (i.e., the noise correlation is either 1 or -1), the new outer bound yields exact capacity region for two cases: 1) BCs with degraded message sets; 2) BCs with one-sided conferencing from the weaker receiver to the stronger receiver. For these two cases, it is also shown that the outer bound is within half bits to the capacity region for arbitrary noise correlation. Furthermore, for the Gaussian BC with arbitrary noise correlation λ, we show that regardless of the capacities of conferencing links, a one-sided cooperative scheme (from the stronger user to the weaker one) based on decode-and-forward is sufficient to achieve the capacity region to within $\frac{1}{2}\log \left( {\frac{2}{{1 - |\lambda |}}} \right)$ bits.

The two-user broadcast channel (BC) with decoders connected by cooperative links of given capacities (known as conferencing decoders) is considered. A novel outer bound on the capacity region is established. This outer bound is derived using multiple applications of the Csiszár-Körner identity. A new achievable rate region for the channel is also presented which is derived by applying Marton’s coding as the transmission scheme, and quantize-bin-and-forward at one receiver and decode-and-forward at the other receiver as cooperative strategy. It is proved that the outer bound coincides with the achievable region for a class of semi-deterministic BCs with degraded message sets. This is the first capacity result for the two-user BC with bidirectional conferencing decoders. This result demonstrates that a one-round cooperation scheme is sufficient to achieve capacity for this class of semi-deterministic BCs with degraded message set. A capacity result is also derived for a new class of more capable semi-deterministic BCs with both common and private messages and one-sided conferencing.

This paper aims to characterize the capacity limits of a wireless cellular network with a full-duplex (FD) base-station (BS) and half-duplex user terminals, in which three independent messages are communicated: the uplink message m1from the uplink user to the BS, the downlink message m2from the BS to the downlink user, and the device-to-device (D2D) message m3from the uplink user to the downlink user. From an information theoretical perspective, the overall network can be viewed as a generalization of the FD relay broadcast channel with a side message transmitted from the relay to the destination. We begin with a simpler case that involves the uplink and downlink transmissions of (m1, m2) only, and propose an achievable rate region based on a novel strategy that uses the BS as a FD relay to facilitate the interference cancellation at the downlink user. We also prove a new converse, which is strictly tighter than the cut-set bound, and characterize the capacity region of the scalar Gaussian FD network without a D2D message to within a constant gap. This paper further studies a general setup wherein (m1, m2, m3) are communicated simultaneously. To account for the D2D message, we incorporate Marton's broadcast coding into the previous scheme to obtain a larger achievable rate region than the existing ones in the literature. We also improve the cut-set bound by means of genie and show that by using one of the two simple rate-splitting schemes, the capacity region of the scalar Gaussian FD network with a D2D message can already be reached to within a constant gap. Finally, a generalization to the vector Gaussian channel case is discussed. Simulation results demonstrate the advantage of using the BS as relay in enhancing the throughput of the FD cellular network.

The Interference Channels (ICs) represent fundamental building blocks of many wireless communication networks. Despite considerable progress in network information theory, available capacity results for ICs, specifically those with more than two users, are still very limited. One of the main difficulties in the analysis of these networks is how to establish useful capacity outer bounds for them. In this paper, novel techniques requiring subtle sequential applications of the Csiszar-Korner identity are developed to establish efficient single-letter outer bounds on the sum-rate capacity of interference networks. Then, by using the derived outer bounds, a full characterization of the sum-rate capacity is obtained for various multi-user ICs under specific conditions. Our capacity results hold for both discrete and Gaussian networks.

This paper examines the achievable rate region and the converse of a full-duplex relay broadcast channel with three independent messages: from the source to the relay, from the source to the destination, and from the relay to the destination. We are motivated to study this channel, because it models a full-duplex wireless cellular network in which the uplink user also wishes to send an independent device-to-device message to the downlink users. For the discrete memoryless channel case, we incorporate Marton's broadcast coding to obtain a new achievable rate region which is larger than previous rate regions. We further propose a tighter converse than the cut-set bound. For the Gaussian scalar channel case, we show that by using one of two rate-splitting schemes depending on the channel condition, we can already achieve the capacity region of this particular relay broadcast channel to within a constant gap. The proposed scheme outperforms the benchmark methods in terms of the symmetric generalized degree-of-freedom.

This paper explores the information theoretical capacity limits of uplink-downlink transmissions in a wireless cellular network with full-duplex FD base station (BS) and half-duplex user terminals. We recognize the cross-channel interference between the terminals as the main capacity bottleneck, and propose novel strategies that use BS as a relay to facilitate interference cancellation. We model the FD cellular system as a two-user interference channel with an extra cross-link feedback from the uplink receiver to the downlink transmitter, and show that the feedback allows a larger achievable rate region than the conventional non-feedback schemes. This paper further provides a converse and shows that the proposed scheme achieves the capacity of the full-duplex cellular network to within a constant additive gap. Finally, this paper considers a new scenario in which the uplink terminal has additional information to transmit to the downlink terminal directly. Relaying by the BS is shown to play a crucial role in maximizing the achievable rates in this case.

Capacity bounds for the two-user interference channels with cooperative receivers via conferencing links of finite capacities are investigated. Capacity results known for these communication scenarios are limited to a very few special cases of the one-sided channels. One of the major challenges in analyzing such cooperative networks is how to establish efficient capacity outer bounds for them. In this paper, by applying new techniques, novel capacity outer bounds are established for the interference channels with conferencing receivers. Using the outer bounds, several new capacity results are proved for interesting channels with unidirectional cooperation in strong and mixed interference regimes. A fact is that a conferencing link (between receivers) may be utilized to provide one receiver with information about its corresponding signal or its non-corresponding signal (interference signal). As an interesting consequence, it is demonstrated that both strategies can be helpful to achieve capacity. Lastly, for the case of Gaussian interference channel with conferencing receivers, it is argued that our outer bound is strictly tighter than the previous one derived by Wang and Tse.

As the main basic building blocks of the interference networks, in this paper the broadcast channel, the classical interference channel (CIC), and the cognitive radio channel (CRC) are considered. New capacity outer bounds are established for these channels. These outer bounds are all derived based on a novel unified framework. Using the derived outer bounds, some new capacity results are proved for the CIC and the CRC; a mixed interference regime is identified for the two-user CIC, where decoding interference at one receiver and treating interference as noise at the other one is sum-rate optimal. In addition, a noisy interference regime is derived for the one-sided CIC. Our new capacity theorems for the CIC contain the previously obtained results regarding the Gaussian channel as special cases. For the CRC, a full characterization of the capacity region for a class of more-capable channels is derived. Moreover, it is shown that the derived outer bounds are useful to study channels with one-sided receiver side information wherein one of the receivers has access to the nonintended message; capacity bounds are also discussed in details for such scenarios. Our results lead to new insights regarding the nature of information flow in the basic interference networks.

In this paper, capacity limits are explored for the Cognitive Radio Channel (CRC) with confidential messages. As an idealized information theoretic model for the cognitive radio, this channel includes two transmitters which send independent messages to their corresponding receivers such that one transmitter, i.e., the cognitive transmitter, has access non-causally to the message of the other transmitter, i.e., the primary transmitter. The message designated to each receiver is required to be kept confidential with respect to the other receiver. The secrecy level for each message is evaluated using the equivocation rate. Novel inner and outer bounds for the capacity-equivocation region are established. It is shown that these bounds coincide for some special cases. Specifically, the capacity-equivocation region is derived for a class of less-noisy CRCs and also a class of semi-deterministic CRCs. For the case where only the message of the cognitive transmitter is required to be kept confidential, the capacity-equivocation region is also established for the Gaussian CRC with weak interference.

In this paper, a full characterization of the sum-rate capacity is established for the general degraded single-hop communication networks with any arbitrary topology. It is proved that a successive decoding scheme is sum-rate optimal for these networks. Also, it is shown that the transmission of only a certain subset of messages is sufficient to achieve the sum-rate capacity in such networks. An algorithm is presented to determine this subset of messages explicitly. This algorithm is described using novel graphical illustrations. The sum-rate expression for the degraded networks is then used to derive a unified outer bound on the sum-rate capacity of arbitrary non-degraded networks. Some variations of the degraded networks are given for which the derived outer bound is sum-rate optimal. Specifically, for the first time, network scenarios are identified where the incorporation of both successive decoding and treating interference as noise achieves their sum-rate capacity.

One of the key open problems in network information theory is to obtain the capacity region for the two-user Interference Channel (IC). In this paper, new results are presented for this channel. First, a novel outer bound on the capacity region is given. It is shown that this outer bound is optimal in the strong interference regime. Moreover, by using the derived outer bound, some new capacity theorems are proved. Specifically, a mixed interference regime is identified for the general IC where decoding interference at one receiver and treating interference as noise at the other one is sum-rate optimal. Also, a class of one-sided ICs with weak interference is identified for which treating interference as noise is sum-rate optimal. Our new capacity theorems include the previously obtained results for the mixed Gaussian IC and the weak Gaussian one-sided IC as special cases. Next, some results are given on the Han-Kobayashi (HK) achievable rate region. The evaluation of this rate region is in general difficult. In this paper, a simple characterization of the HK rate region is derived for a novel very weak interference regime. It is shown that for this very weak interference regime, the achievable sum-rate due to the HK region is identical to the one given by the simple treating interference as noise strategy. Finally, by using a novel genie-aided technique, a noisy interference regime is identified for the general IC (non-Gaussian) where the sum-rate capacity is achieved by treating interference as noise at the receivers. This result includes the noisy interference regime previously obtained for the Gaussian channel as a special case.

Capacity limits are studied for the two-user wireless ergodic fading Interference Channel (IC) with partial Channel State Information at the Transmitters (CSIT) where each transmitter is equipped with an arbitrary deterministic function of the channel state (this model yields a full control over how much state information is available). One of the main challenges in the analysis of fading networks, specifically multi-receiver networks including fading ICs, is to obtain efficient capacity outer bounds. In this paper, a novel capacity outer bound is established for the two-user ergodic fading IC. Besides being well-described, our outer bound is efficient from several aspects. Specifically, it is optimal for the fading IC with uniformly strong interference. Also, it is sum-rate optimal for the channel with uniformly mixed interference. More importantly, it is proved that when each transmitter has access to any amount of CSIT that includes the interference to noise ratio at its non-corresponding receiver, the outer bound differs by no more than one bit from the achievable rate region given by Han-Kobayashi scheme. This result is viewed as a generalization of the Etkin-Tse-Wang “to within one bit” capacity result for the static channel to the time-varying wireless fading case.

The two-user wireless ergodic fading Broadcast Channel (BC) with partial Channel State Information at the Transmitter (CSIT) is considered. The CSIT is given by an arbitrary deterministic function of the channel state. This characteristic yields a full control over how much state information is available, from perfect to no information. A novel approach is developed to adapt and explicitly evaluate the well-known UV-outer bound for the Gaussian fading channel using the entropy power inequality. Our approach indeed sheds light on the role of broadcast auxiliaries in the fading channel. It is shown that the derived outer bound is optimal for the channel with perfect CSIT. Our bounds are also directly applicable to the case without CSIT which has been recently considered in several papers. Next, the approach is developed to analyze for the fading BC with secrecy. In the case of perfect CSIT, a full characterization of the secrecy capacity region is derived for the channel with common and confidential messages. This result completes a gap in a previous work by Ekrem and Ulukus. For the channel without common message, the secrecy capacity region is also derived when the transmitter has access only to degradedness ordering of the channel.

This paper presents a solution for one of the open problems in network information theory: “What is the generalization of the strong interference regime to the K-user interference channel?” A new approach is developed based on which one can obtain strong interference regimes not only for the multi-user interference channels but also for other interference networks with any arbitrary topology. To this development, some new lemmas are proved which have a central role in our derivations. As a result, this paper establishes the first non-trivial capacity result for the general multi-user classical interference channel (for both discrete and Gaussian channels).

In this paper, capacity inner and outer bounds are established for multiuser channels with Channel State Information (CSI) known non-causally at the transmitters: The Multiple Access Channel (MAC), the Broadcast Channel (BC) with common information, and the Relay Channel (RC). For each channel, the actual capacity region is also derived in some special cases. Specifically, it is shown that for some deterministic models with non-causal CSI at the transmitters, similar to Costa's Gaussian channel, the availability of CSI at the deterministic receivers does not affect the capacity region.

The authors consider ‘partially’ and ‘fully cooperative’ state-dependent relay broadcast channels (RBCs), where partial channel state information (CSI) is available at the nodes causally. First, the authors derive an achievable rate region for general discrete memoryless partially cooperative RBC (PC-RBC) with partial causal CSI, by exploiting superposition coding at the source, decode-and-forward scheme at the relay and Shannon's strategy at the source and the relay. Then, they establish the capacity region of the discrete memoryless physically degraded PC-RBC with partial causal CSI. They also characterise the capacity region of discrete memoryless PC-RBC with feedback and partial causal CSI, and show that feedback does not affect the capacity region of the physically degraded channel. Moreover, for the fully cooperative RBC (FC-RBC) with partial causal CSI the authors obtain the same results as for the state-dependent PC-RBC. The authors' results subsume the previously known results for the degraded broadcast and relay channels with causal CSI. Finally, they extend their achievable rate regions to the Gaussian cases. Providing some numerical examples for the Gaussian cases, they compare the achievable rate regions derived for different situations.

This paper investigates the capacity problem for some multiple-access scenarios with cooperative transmitters. First, a general Multiple-Access Channel (MAC) with common information, i.e., a scenario where p transmitters send private messages and also a common message to q receivers and each receiver decodes all of the messages, is considered. The capacity region of the discrete memoryless channel is characterized. Then, the general Gaussian fading MAC with common information wherein partial Channel State Information (CSI) is available at the transmitters (CSIT) and perfect CSI is available at the receivers (CSIR) is investigated. A coding theorem is proved for this model that yields an exact characterization of the throughput capacity region. Finally, a two-transmitter/one-receiver Gaussian fading MAC with conferencing encoders with partial CSIT and perfect CSIR is studied and its capacity region is determined. For the Gaussian fading models with CSIR only (transmitters have no access to CSIT), some numerical examples and simulation results are provided for Rayleigh fading.

In this paper, we study the two-user Gaussian fading Multiple Access Channel (MAC) with cooperative encoders. Two different scenarios are studied: the Gaussian fading MAC with a common message, and the Gaussian fading MAC with conferencing encoders. The throughput capacity region of these channels with partial Channel State Information (CSI) at the transmitters (CSIT) and perfect CSI at the receiver (CSIR) is established. For the Gaussian fading systems with only CSIR (transmitters have no access to CSIT), some numerical examples and simulation results are provided for Rayleigh fading models.

The Partially Cooperative Relay-Broadcast Channel (PC-RBC) is a generalization of Relay Channel in which the relay node decodes its own private message. In this paper, we introduce a class of parallel PC-RBCs with three unmatched subchannels, in which the first component of the channel is assumed to be degraded, the second to be orthogonal and the third to be deterministic. We characterize the capacity region of this channel for the case where the source sends a private message for each of the users. We also investigate a class of parallel relay channels with three unmatched subchannels, in which the first component of the channel is degraded, the second is orthogonal and the third is semi-deterministic, and characterize the capacity of it. Our capacity results enlarge the family of PC-RBCs and relay channels for which the capacity region is known.

We consider the Gaussian Dirty Tape Channel (DTC) Y = X + S + Z, where S is an additive Gaussian interference known causally to the transmitter. The general expression maxPU,f(·),X = f(U, S)I(U; Y) is proposed for the capacity of this channel. For linear assignment to f(-), i.e., X = U - βS, this expression leads to the compensation strategy proposed previously by Willems to obtain an achievable rate for the DTC. We show that linear assignment to f(·) is optimal under the condition that there exists a real number β* such that the pair (X + β S, U) is independent of the interference S. Furthermore, by applying a time-sharing technique to the achievable rate derived by linear assignment to f (·), an improved lower bound on the capacity of DTC is obtained. We also consider the Gaussian multiple access channel with additive interference, and study two different scenarios for this system. In the first case, both transmitters know interference causally while in the second, one transmitter has access to the interference noncausally and the other causally. Achievable rate regions for these two scenarios are then established.

In this paper the Multiple Relay Channels (MRC) with delays, with and without channel state information (CSI) are investigated from an information theoretic point of view. For the MRC with unlimited look ahead where the relays can use the whole received block to encode, upper and lower bounds on the capacity are derived which are tight for the degraded case. For the MRC without-delay where the relays have access to the present received symbols in addition to the past symbols, the capacity of the degraded channel is established using Shannon's strategy for the channels with side information. Then we introduce the state dependent MRC with unlimited look ahead and derive a lower bound on the capacity when the CSI is noncausally available at the sender and relays, using Gel'fand-Pinsker coding technique. Finally, the capacity of the degraded Gaussian MRC with unlimited look ahead and with state noise (dirty paper problem) is established.

In this paper, we consider partially and fully cooperative state-dependent relay broadcast channels with perfect causal channel state information (CSI). For these two channels, we study three different situations: 1) both the source and the relay nodes have access to perfect CSI, 2) perfect CSI is only known to the relay nodes, 3) perfect CSI is only available at the source node. In each situation we obtain the capacity region for a degraded version of the channel. Our work subsumes previously obtained results for the degraded broadcast and relay channels with perfect causal CSI.

We investigate the parallel partially cooperative relay broadcast channel with unmatched degraded subchannels. We characterize the capacity region of this channel in the general setting that, transmitter sends a common message for both users and a private message for each of them. Our achievability result is based on the choosing appropriate parameters for the general achievable rate region of partially cooperative relay broadcast channel. We provide a converse proof for this achievable region as well, which establishes the capacity region.