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A modified version of Costa's dirty paper channel is studied, in which both the input signal and the state experience stationary and ergodic time-varying fading. The fading coefficients are assumed to be known exclusively at the receiver. An inner bound of the achievable rates using lattice codes is derived and compared to an outer bound of the capacity. For a wide range of fading distributions, the gap to capacity is within a constant value that does not depend on either the power of the input signal or the state. The results presented in this paper are applied to a class of ergodic fading broadcast channels with receive channel state information, where the achievable rate region is shown to be close to capacity under certain configurations.

We investigate the coexisting network of hybrid broadcast and point-to-point channels, where there is a public message required by each receiver except its own private message in the broadcast channel. Based on distributed zero-forcing approach, the minimum antenna configuration is deduced, under the condition of least antennas at each receiver. Then we propose a linear transceiver design for the network. Performance analyses including the antenna efficiency and achievable rate are provided and further validated by simulations.

In this paper, we focus on Multi-User MIMO Broadcast Channels with few users feeding back their channel estimates, i.e. K linear in the number M of transmitting antennas. Under this condition, the chance of finding a subset of users almost orthogonal vanishes when M gets large. For this reason, we show that the Zero Forcing (ZF) beamformer, commonly accepted for practical implementations, can be easily outperformed by other schemes based on QR decomposition, approaching the channel capacity. Our beamformer construction is less complex than ZF greedy algorithms and more robust than semi-orthogonal construction. At high SNR, we show that even the sub-optimal Tomlinson-Harashima encoding technique outperforms the ZF beamforming, halving the gap with respect to Dirty Paper Coding.

Recently, studies on suboptimal precoding techniques for multiple-input multiple-output broadcast channels (MIMO-BC), which achieve performance near to that of the dirty paper coding (DPC), have drawn attention to vector perturbation (VP) precoding. In practice, each antenna or more generally each antenna group has its own limit on the transmitted power, which makes per-antenna-group power constraints more meaningful than the sum power constraint. In this paper, we introduce an optimization technique for VP precoding employing the minimum mean-square error (MMSE) criterion with per-antenna-group power constraints. This technique is inspired by the p-sphere encoding in a sense that it involves finding the node with the lowest mean-square error (MSE) over a lattice. We demonstrate that the MSE metric, as well as the p-norm one, can be enclosed in a proper Frobenius-norm ball. This Frobenius-norm ball shrinks until it captures the perturbing vector minimizing the MSE. Numerical results show that the proposed algorithm outperforms conventional VP precoding and the p-sphere encoding, but at higher complexity. Consequently, we investigate a couple of simplified techniques employing the MMSE criterion, which perform almost as well as the proposed precoding technique, but are less complex.

Tomlinson-Harashima-precoding can be used as dirty-paper-coding method for transmissions over a broadcast channel. From single user systems it is known that this symbol wise precoding method suffers, amongst others, from a power loss. However, for broadcast scenarios it is also possible to observe a power gain. This paper investigates the required transmit power for Tomlinson-Harashima-precoding in broadcast systems. Additionally, upper and lower bounds on the required power are derived.

Multiple watermarking is concerned with embedding several messages into the same host signal, with different robustness and transparency requirements. This paper proposes two implementable scalar schemes for multiple user "dirty paper coding". The first - straightforward - approach consists of an independent superposition of two scalar dirty paper coding schemes. The second consists in the joint design of a scalar dirty paper coding. This joint approach is based on the ideal dirty paper coding scheme for broadcast channels with noncausal side information known to the transmitter. For this purpose, the "scalar Costa scheme" that has been originally conceived for one user is extended to two users. Performance evaluations, including bit error rates and capacity region curves are provided for both methods, illustrating the improvements brought by a joint design.

In this paper, we study the limited feedback model for partial CSI at the basestation (BS) for multiple antenna broadcast channels: the BS has the knowledge of quantized CSI of each user. We first give a practical limited feedback scheme designed for multiple antenna broadcast channels. Then, we study the sum rate performance of zero-forcing dirty paper coding under the proposed limited feedback scheme. An upper bound is also derived to get some insight about the impact of the use of limited feedback. Interestingly, we find that the systems experience a ceiling effect on the sum rate for a fixed feedback rate.

This paper explores the fundamental downlink performance limits of multicell networks when cooperation is allowed between all the base station in the network. Toward this end, we infer the asymptotic sum rate of a capacity-achieving technique (known as dirty paper coding) for the broadcast channel in the limit of a large number of transmit antennas and single-antenna users. The users have unequal SNRs characterized by a doubly-regular gain matrix and we show that this condition can be satisfied in a finite cellular network of hexagonal cells where users are placed on corners of hexagons centered on the bases. Under this placement, we can compute the asymptotic rate per user when dirty paper coding is used across base stations in a coordinated network. We extend the analysis to an infinite coordinated network and show that its performance is lower-bounded by that of a single isolated cell. Performance comparisons are also made with conventional cellular networks where coordination among bases is not allowed.

We consider the beamformer design for zero-forcing dirty paper coding (ZF-DPC), a suboptimal transmission technique for MISO broadcast channels (MISO BCs). Beamformers for ZF-DPC are designed to maximize a performance measure, subject to some power constraints and zero-interference constraints. For the sum rate maximization problem under a total power constraint, the existing beamformer designs in the literature are based on the QR decomposition (QRD), which is used to satisfy the ZF constraints. However, the optimality of the QRD-based design is still unknown. First, we prove that the QRD-based design is indeed optimal for ZF-DPC for any performance measure under a sum power constraint. For the per-antenna power constraints, the QRD-based designs become suboptimal, and we propose an optimal design, using a convex optimization framework. Low-complexity suboptimal designs are also presented. © 2012 IEEE.

In this work, we propose using Faster than Nyquist (FTN) signaling to achieve transmission over continuous-time Gaussian broadcast channel. In the FTN broadcasting, different users' messages are completely separated in the coding stage; hence removing the joint encoding that is typically needed in the previously proposed broadcast channel coding schemes. Furthermore, users' data symbols are explicitly and separately transmitted over the channel using the FTN signaling; thus, alleviating the definition of auxiliary random variables used in the broadcast channel coding theorems. This work shows that the FTN broadcast signaling allows achieving the capacity boundaries of the Gaussian broadcast channel. This implies that FTN can be a viable alternative to the standard capacity-achieving techniques considered in discrete-time Gaussian broadcast channel, i.e., superposition coding and dirty paper coding.

We study the gain of dirty paper coding (DPC) by investigating the sum rate as the number of antennas at the transmitter grows in a multi-user MISO broadcast channel. We show a comparative sum rate gain of DPC over the zero forcing (ZF) scheme. The sum rate gap between DPC and ZF is analyzed assuming asymptotically high signal-to-noise ratio (SNR) in the case when the number of users is the same as the number of antennas at the transmitter. As a result, we find the sum rate gap is linearly increased as the number of transmit antennas is increased. Also, numerical results of DPC and ZF are shown in a M-by-1 MISO, M-user Rayleigh fading channel, where M=2, 4, 8, 16. We conclude that the more the number of transmit antennas is, the more attractive DPC becomes with respect to the sum rate.

Outer and inner bounds are established on the capacity region of two-sender, two-receiver interference channels where one transmitter knows both messages. The transmitter with extra knowledge is referred to as being cognitive. One of the outer bounds is based on the Nair-EI Gamal outer bound for broadcast channels. The inner bound is based on strategies that generalize prior work to include rate-splitting, dirty-paper coding, and carbon-copying. The bounds are demonstrated for Gaussian channels.

In this paper we want to make a fair comparison between TDMA and DPC in terms of the BER region and maximum number of satisfied users. For this purpose we choose the coding/decoding schemes as follows : DPC is based on a trellis coded quantization implementation and successive coding while TDMA uses trellis coded modulation. Simulation results are provided both for the perfect and imperfect channel state information cases. In the perfect CSI case all the tested scenarios show that TDMA generally outperfoms DPC. In the imperfect CSI case DPC is shown to be less sensitive than TDMA to channel estimation errors.

This paper investigates the three-receiver (Y 1 , Y 2 , Y 3 ) discrete memoryless (DM) broadcast channel (BC) for eight receive message cognition settings in which the weakest receiver Y 3 knows the message intended for the intermediate receiver Y 2 , Y 2 may or may not know the message intended for Y 3 , and the strongest receiver Y 1 knows none, one, or both of the messages intended for receivers Y 2 and Y 3 . For these eight settings, but for the Gaussian BC, the capacity regions were obtained previously by Asadi et al. In this paper, we establish the capacity regions for all eight cases for the class of less noisy DM BCs, thereby lifting the previously known capacity results from the Gaussian BC to the less noisy BC. To further expand the optimality results to strictly larger classes of broadcast channels, we propose a coding scheme that includes rate-splitting and indirect decoding, techniques not needed for the less noisy or Gaussian BCs, for four of the eight message cognition cases in which receiver Y 2 knows the message intended for Y 3 , and show that this more general scheme achieves capacity without requiring that receiver Y 2 be stronger than Y 3 in any sense (and when Y 1 knows the message intended for Y 2 , Y 1 is not required to be stronger than Y 2 either whereas when Y 1 does not know the message intended for Y 2 it is assumed that Y 1 is more capable than Y 2 ) whereas it is assumed that Y 1 is less noisy than Y 3 in all four cases. Moreover, the converse proof for the second set of capacity results require both the Nair-Wang information inequality and the Csiszar sum lemma.

In this paper, we consider precoder design for multiuser multiple-input-multiple-output (MIMO) Gaussian broadcast (BC) channels and propose a generalized zero-forcing (GZF) precoder based on successive dirty-paper coding (DPC), i.e., the GZF-DP precoder. The GZF-DP precoder is an extension of the GZF-DP precoder designed earlier for multi-input-single-output broadcast (MISO-BC) channels, and also a generalization of both the linear block-diagonalization ZF (BD-ZF) and the successive ZF with DPC (SZF-DPC) precoders. With the GZF-DP precoder, the depth of the inter-user interference after precoding (and before the DPC) can be specified at will by a parameter ν, which provides a trade-off between the optimal rates and the DPC implementation-complexity. Utilizing DPC, the known non-causal inter-user interferences from the other (up to) ν users are canceled through successive encoding. Within the class of GZF-DP, we analyze the optimal precoder designs both for sum-rate and minimum user-rate maximizations, which are solved in closed-forms in conjunction with water-filling algorithms depending on ν. We show through numerical results that, the proposed GZF-DP precoder with a small ν renders significant rate increments compared to the linear BD-ZF precoder, and is close to the SZF-DP preocder with a much less DPC complexity.

The broadcast channel under delayed, mixed, hybrid, or no CSIT Is a subject of much Interest but has been studied only under i.i.d. fading and perfect CSIR for all users. Models that go beyond i.i.d. fading and perfect CSIR are of practical Importance since users may experience unequal fading block-length (coherence time) and unequal CSIR availability due to different mobility and scattering environment. This paper studies a two-user MISO broadcast channel with hybrid CSIR, where one static user (with slower fading) has CSIR and one dynamic user (with faster fading) does not have free CSIR. Under this hybrid CSIR condition, the paper studies the degrees of freedom under various CSIT scenarios: no, delayed, and hybrid CSIT. For no CSIT, we provide an outer bound that meets the achievable degrees of freedom region when the coherence times of the users are the same. For both delayed and hybrid CSIT, the achievable regions partially meet their corresponding outer bounds, and furthermore the corresponding gaps decrease with the dynamic user coherence time.

We investigate the maximum coding rate achievable over a two-user broadcast channel for the scenario where a common message is transmitted using variable-length stop-feedback codes. Specifically, upon decoding the common message, each decoder sends a stop signal to the encoder, which transmits continuously until it receives both stop signals. For the point-to-point case, Polyanskiy, Poor, and Verd\'u (2011) recently demonstrated that variable-length coding combined with stop feedback significantly increases the speed at which the maximum coding rate converges to capacity. This speed-up manifests itself in the absence of a square-root penalty in the asymptotic expansion of the maximum coding rate for large blocklengths, a result a.k.a. zero dispersion. In this paper, we show that this speed-up does not necessarily occur for the broadcast channel with common message. Specifically, there exist scenarios for which variable-length stop-feedback codes yield a positive dispersion., Comment: Extended version of a paper submitted to ISIT 2015

In this paper, a three-receiver (named as one-receiver two-eavesdropper) discrete memoryless broadcast channel (DM-BC) with three degraded message sets and side information is studied. The main objective of this paper is to present a theorem so as to give an achievable secrecy region for this one-receiver two-eavesdropper DM-BC with the side information available at the transmitter. In the achievability proof scheme, we use the superposition coding scheme to divide the available randomness into different levels for misleading the eavesdroppers. We establish the achievable secrecy region by using a combination of Gelfand-Pinsker binning scheme and rate splitting technique. Achievability in this case also follows from the new idea of Nair-El Gamal indirect decoding. The achievable secrecy region of this paper subsumes the steinberg rate region for two-receiver degraded BC with the side information as well as the secrecy capacity region for one-receiver two-eavesdropper DM-BC with no side information as its special cases.

This paper studies the blind interference alignment (BIA) in a homogeneous 3-user 2 × 1 broadcast channel (BC). In a homogeneous BC, each link connecting the transmitter and a user undergoes independent fading with identical coherence time. BIA refers to the implementation of interference alignment with no need of CSIT. It is shown in our early work [1] that, BIA can be easily accomplished in a homogeneous 2-user 2 × 1 BC with no requirement of using time-frequency extension, or mounting an extra antenna to each single-antenna receiver. In this paper, we extend the idea to a homogeneous 3-user 2 × 1 BC. We show that, if the three homogeneous 2 × 1 links satisfy certain offset condition, a homogeneous 3-user 2 × 1 BC can be completely decomposed into finite-time channel blocks, and each of which is BIA-feasible. By using a new technique that is different with the one in our early work, we prove a sufficient condition for a homogeneous 3-user 2 × 1 BC to be completely decomposable, i.e., to be suitable for BIA to achieve the optimal 3/2 DoF. We further study a multi-user 2 × 1 broadcast network, in which there are K ≥ 3 homogeneous users and their coherence time offsets are independently and uniformly distributed. We show that, if K ≥ 15, a 2-antenna transmitter can find, with more than 99% certainty, three users to form a BIA-feasible 3-user BC and achieve the optimal 3/2 DoF with no need of CSIT.

In this paper a scheduling algorithm based on proactive co-channel interference (CCI) evaluation for multiuser multiple-input multiple-output (MU-MIMO) broadcast channel (BC) is proposed. The strategy converts user scheduling to spatial subchannel selection problem. A new parameter η, named as proactive CCI evaluation factor is defined for estimating the existing and potential mutual interference. With different settings of η, the proposed algorithm can be generalized to some existing reactive scheduling methods. The user and subchannel scheduling criterion as well as processing procedure are presented in this paper. By appropriately choosing η and comprehensively considering candidate subchannel transmission gain, along with mutual interference among candidate and activated subchannels as well as those would be selected subsequently. A set of sub-channels with less CCI are scheduled, and an improvement of system sum rate is achieved. Simulation results show that compared with those reactive methods, given appropriate η the proposed algorithm could achieve better tradeoff between system sum rate improvement and computational complexity control.

This paper studies secure communication over the broadcast channels with an untrusted relay. The relay helps users with transmission in broadcast channels, but we also wish to keep the information secret against the relay. Compress-and-forward relaying is a potential strategy to achieve secrecy. We obtain the achievable rate-equivocation regions by combining it with Marton's coding scheme and Cover's superposition coding scheme respectively. The secrecy rate region based on Marton's coding scheme provides a general result, without knowing information regarding two users. If we know which user is better (i.e. receiving more information), we can design a simpler scheme with superposition encoding. Outer bound to the rate-equivocation regions is also provided in this paper.

Three-Receiver broadcast channels (BC) are of interest due to their information-theoretic differences with two-receiver one. In this paper, we derive achievable rate regions for two classes of 3-receiver BC with side information (SI), i.e. Multilevel BC (MBC) and 3-receiver less noisy BC, using a combination of superposition coding, Gelfand-Pinsker binning scheme and Nair-El Gamal indirect decoding. Our rate region for MBC subsumes Steinberg rate region for 2-receiver degraded BC with SI as its special case. We will also show that the obtained achievable rate regions in the first two cases are tight for several classes of non-deterministic, semi-deterministic, and deterministic 3-receiver BC when SI is available both at the transmitter and at the receivers. We also prove that as far as a receiver is deterministic in the three-receiver less noisy BC, the presence of side information at that receiver does not affect the capacity region. We have also provided the writing on dirty paper (WDP) property for 3-receiver BC is provided as an example. In the last section, we provide simple bounds on the capacity region of the Additive Exponential noise three-receiver broadcast channels with Additive Exponential interference (AEN-3BC-EI)., 13 pages, 4 figures, This paper is partially presented at 2012 IEEE International Symposium on Information Theory

Rational secret sharing, first introduced by Halpern and Teague, means that whether players send their shares relies on their utilities, whereas in traditional scheme, players are assumed to contribute their shares willingly. This paper introduces a new kind of player and puts forward a 2-out-of-2 rational secret sharing scheme where players run their reconstruction protocol in standard communication networks other than broadcast channels which are often used in previous papers. The 2-out-of-2 rational secret sharing scheme in standard communication networks can achieve fairness.

In this paper the University of Mosul Campus is considered as an outdoor wireless propagation case study for environmental fields. For this case study, the fields emitted from Asia Cell mobile base station identifier ID 4194 are measured, simulated and compared with the available electromagnetic safety standards such as ICNIRP, FCC, EUROPEAN, and Salzburg standards. The measurements are carried out using AARONIA Spectrum HF-6085 instrument for high frequency and the results obtained are compared with simulated results obtained using EFC-400TC software package version (2009) for high frequency. The measurements are carried out at 43 observation points in the site at height of 1.5 in the two systems GSM900 and GSM1800. Two cases are studied; the first is sectorwise radiation and the second is multiple radiations. For multiple radiations, two cases are simulated; the first when the base station is in the no-load condition, and the effect of Broadcast Control Channels (BCCHs) for the three 120° sectors in GSM900 and GSM1800 systems are considered; and the second when the base station is in the full-load condition, where the effect of BCCHs and all Traffic Channels (TCHs) for all sectors are considered in GSM900 and GSM1800 systems.

This paper presents outerbounds for the two-user Gaussian fading broadcast channel. These outerbounds are based on Costa's entropy power inequality (Costa-EPI) and are formulated mathematically as a feasibility problem. For classes of the two-user Gaussian fading broadcast channel where the outerbound is found to have a feasible solution, we find conditions under which a suitable inner and outer bound meet. For all such cases, this paper provides a partial characterization of the capacity region of the Gaussian two-user fading broadcast channel., Comment: Also submitted to ISIT 2011

In this paper, we investigate an interference alignment (IA) technique introduced by Cadambe and Jafar in mutually interfering broadcast channels (IFBCs). First, we study the spatial multiplexing gain (SMG) for the 3-cell IFBC where all base stations and mobile users are equipped with multiple antennas. To achieve the derived optimal SMG, we extend the IA algorithm designed for K-user multi-input multi-output (MIMO) interference channels (IFCs) to the IFBC. In this paper, we present the IA scheme in conjunction with user selection which outperforms the time division multiple access (TDMA) technique in the IFBC environment. The optimal scheduling method capitalizes on multiuser diversity to achieve a significant fraction of sum capacity by using an exhaustive search algorithm. Since the computational complexity of the optimal scheduling method is prohibitive, a reduced complexity suboptimal scheduling method is proposed based on a coordinate ascent approach. Simulation results confirm that the reduced complexity scheduling algorithm achieves the sum rate close to the optimal algorithm with much reduced complexity.

An input-symmetric (IS) degraded broadcast channel (DBC) is a discrete DBC whose component channels are input-symmetric and the intersection of their input-symmetry groups is transitive. The discrete additive DBC and the group-additive DBC are IS-DBCs. This paper introduces an independent encoding scheme which employs permutation functions of the independent codes. This permutation encoding approach for the group-additive DBC is to employ group additions of the independent codes. This paper shows that the permutation encoding approach achieves the boundary of the capacity region for IS-DBCs, and yields a simple characterization of that capacity region.

In this paper, we consider the isotropic fading broadcast channel. This channel refers to the case when no directional information is available at the transmitter side, and was studied by Jafar et al in. It was shown that the isotropic vector broadcast channel (BC-V) can be reduced to an equivalent scalar broadcast channel (BC-S). It is well known from [2]http://www.pimrc2008.org/ that BC-S is degraded in the same order as the channel magnitude. This implies that the optimal strategy that maximizes the sum capacity for BC-S and BCV consists on allocating the whole power to the strongest user. Based on these results, we derive in this paper the diversity multiplexing tradeoff (DMT) of the isotropic fading BC-S and BC-V, and we propose optimal schemes that achieve these DMT.

Stability has become an important performance measure for wireless communication systems. In this paper general conditions for stability in broadcast channels are derived. It is shown that for any mean arrival rate inside the ergodic capacity region the system is stable when the applied scheduling policy complies with the conditions presented in the main results. In this case the policy is so-called throughput-optimal and the results in the paper provide a convenient way either to design or to verify the throughput-optimal policies. The applicability of the results is shown along with some examples.

Many mobile ad hoc network protocols use simple flooding, in order to adapt to changes in time varying network topology. Most of the times, a network-wide flood results in redundant packets and increases network congestion, probability of packet collision, low utilization of available bandwidth, and most important, higher power consumption. In this paper, we propose a new cross-layer broadcast scheme to minimize broadcast traffic in mobile ad hoc networks. Our scheme is based on use of received signal strength indicator, RSSI, value to reduce the number of broadcast packets. The effectiveness of the proposed technique is verified using simulations., This paper has been withdrawn as it's available as part of IEEE WICOM 2007 proceedings from IEEExplore

The problem of collaborative spectrum sensing by a group of unlicensed devices is considered in this paper. The problem is placed in the specific setting of identifying available TV channels for use by the unlicensed devices. The system model and analysis developed in the paper is applicable to a number of more general dynamic spectrum sharing scenarios. Through analysis and simulations, it is shown in the paper that collaboration among nodes leads to more efficient spectrum utilization from a system-level point of view, while decreasing computational complexity of detection algorithms at the individual sensing nodes

This paper summarizes, with a tutorial flavor, the "quest" for the capacity region of a Gaussian broadcast channel with vector input and scalar outputs, where the channel is linear time-invariant and perfectly known to all terminals. Determining the capacity region of this channel is a challenge, since this model belongs to the class of non-degraded broadcast channels, for which a complete information-theoretic characterization is still open. Nevertheless, a series of previous results shed light on several aspects: a coding strategy and its achievable region were given, and it was shown that, as far as the throughput (rate sum) is concerned, this coding strategy is optimal. In this paper we review these results and add our original point of view. Moreover, we point out some new observations and directions for future study on the subject.

In Multimedia Broadcast Multicast Service (MBMS)-dedicated cell, multipath aliasing is an inevitable challenge for CAS reception in long delay spread channels. Meanwhile, traditional Channel Estimation (CHE) algorithms may not work well in such scenarios. For overcoming this problem, an Aliasing-Elimination CHE (AE-CHE) algorithm was proposed. This novel algorithm utilizes the pre-decoded Physical Broadcast Channel (PBCH) to generate a full-symbol length multipath distribution. By using the multipath distribution, aliasing errors could be eliminated effectively. However, previous researches are mainly based on ideal factors such as perfect PBCH decoding, static channel without Doppler spread, which does not match the actual situation in practical receivers. This paper studies the effects of actual PBCH decoding ability and Doppler spread of time-variant channels on the performance of the AE-CHE algorithm. Analysis and simulation results show that the AE-CHE algorithm could also outperform the traditional algorithms even in the presence of non-ideal factors.

In this paper, the sum secure degrees of freedom (SDoF) of the K-user Multiple Input/Single Output (MISO) Broadcast Channel with Confidential Messages (BCCM) and alternating Channel State Information at the Transmitter (CSIT) is investigated. In the MISO BCCM, a K-antenna transmitter (TX) communicates toward K single-antenna receivers (RXs), so that message for RX k is kept secret from RX j with j sum = (2K − 1)/2. Interestingly, this SDoF sum is attained by a rather simple achievability in which the TX uses artificial noise to prevent the decoding of the message of the unintended receivers at RX 1. The proof for the case K = 3 is discussed in detail.

In this paper, we consider the K-receiver discrete memoryless (DM) broadcast channel (BC) with non-distinct message demands; in particular, the K-receivers demand N ≤ K messages of the same rate R with each message demanded by a (disjoint) subset of receivers. Moreover, each message consists of 2K independent sub-messages, with each sub-message available at a distinct subset of receivers as side information. We assume symmetric side-information in that the sub-messages that are available at the same number of receivers as side information have the same rate. This model is akin to coded caching with non-distinct demands over the general BC (rather than a shared noiseless link) and also extends our recent work in which message demands were distinct. We propose a coding scheme that consists of (a) a new form of network coding in which the non-distinctness of the message demands and the side information are used to create 2K−2K−N groupcast messages —and these are not in general the same as for decentralized caching over a shared noiseless link in recent work by Yu et al. —(b) message merging where certain sets of those groupcast messages are bijectively mapped into a single message each (c) superposition coding to generate the codebooks for the merged messages and (d) successive decoding at each receiver to find its intended message with the aid of the side information. In particular, while each receiver decodes the codebooks of certain merged messages, some of the receivers must in addition also locally generate 2K−N−1 groupcast messages to find their respective intended messages. Although we do not provide proofs of converses, the proposed scheme is optimal for two stated categories herein of BCs and message demands.

This paper considers the two-user Gaussian arbitrarily-varying broadcast channel, wherein a power-limited transmitter wishes to send a message to each of two receivers. Each receiver sees a superposition of the transmitter's sequence, Gaussian noise, and a signal from a power-limited malicious jammer. The jammer is assumed to know the code, but is oblivious to real-time transmissions. The exact capacity region of this setting is determined to be the capacity region of the standard Gaussian broadcast channel, but with the noise variance increased by the power of the jammer, as long as the received power of the jammer at each receiver is less than that of the legitimate transmitter. A key aspect of the achievable scheme involves sharing randomness from the transmitter to the receivers by breaking the transmitted sequence into segments, and either transmitting at full power in a segment, or sending zero. By coding over the on/off signal, a small shared randomness can be established without corruption by the jammer, and without interfering with the standard superposition coding strategy for the Gaussian broadcast channel.

In this paper, we study the communication problem of multiuser multiple-input single-output (MISO) broadcast channels with imperfect channel state information (CSI) at the transmitter. Zero-forcing precoding based on the imperfect CSI is adopted so that the channel can be transformed into a Gaussian interference channel. We consider a practical setting where only discrete input signalings are employed and all the receivers adopt single-user treating-interference-as-noise (TIN) decoding, as opposed to rate-splitting and successive interference cancellation. Under this setting, we first use the deterministic model to approximate the original channel model and develop communication schemes to achieve the entire capacity region. By translating the results of the deterministic model back to the MISO model, we develop a systematic way to design discrete input signalings for the original problem. Our simulation results show that our scheme is capable of approaching the (outer bound of) capacity region of the Gaussian interference channel.

This paper proposes a DNN-based distributed algorithm by deploying one DNN in each base station controller (BSC) to approximate the weighted minimum mean-square error (WMMSE) algorithm, which can allocate power in parallel. Maximizing the weighted sum-rate is a common problem setup for power allocation in a single-input single-output (SISO) interfering broadcast channel (IBC). The WMMSE algorithm is a suboptimal and classical solution but has high computational complexity. Recently, a DNN-based algorithm is proposed to speed up the power allocation by approximating the WMMSE algorithm. Motivated by these, a DNN-based distributed algorithm is proposed and the system with 7 cells and 56 users is setup. The experimental results show that centralized DNN with at least 7 layers can achieve the sum-rate performance of 95.02%, but distributed DNN with only 5 layers can achieve the sum-rate performance of 97.40%.

This paper proposes a virtual full-duplex relaying protocol with the aid of multiple half-duplex relay nodes equipped with buffers and multiple antenna elements. The protocol increases the spectral efficiency, in comparison to the conventional half-duplex counterpart. More specifically, multiple relay nodes simultaneously receive a source packet, while a single relay node retransmits a buffered packet to the destination node at the same time slot. In order to eliminate the detrimental effects of inter-relay interference, multiple antenna elements are used at relay nodes. Our performance results show that the proposed virtual full-duplex protocol is capable of achieving a lower delay profile than that of the conventional virtual full-duplex max- max relay selection, while combating limitations imposed by inter-relay interference.

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.

In this paper, we consider the K-receiver discrete memoryless (DM) broadcast channel (BC) with K private messages of the same rate. Inspired by the decentralized caching problem which has received much interest of late, we consider the case where each message consists of 2K independent sub-messages, with each sub-message available at a distinct subset of receivers as side information. We assume that the rates of all the sub-messages available at the same number of receivers are the same. Hence, each receiver has exactly the same amount of information about each message, including its intended message, as side information. For this symmetric side information structure, we establish the symmetric capacity for the interleavable DM BC, a class of channels which subsumes the K-receiver degraded DM BC and the less noisy BC in the three-receiver case. Our coding scheme involves (a) network coding in the form of a bit-wise XOR of two or more messages (b) message merging where multiple messages are bijectively mapped into a single message with a rate that is the sum of the rates of the merged messages (c) superposition coding where the codebooks are generated for the merged messages and (d) successive decoding at each receiver to find its intended message with the aid of the side information.

The current feedback coding strategy for the physical layer security (PLS) mainly focuses on generating secret key used for protecting the transmitted message, and this strategy has been proved only optimal for several degraded cases. Our previous work has proposed a new hybrid feedback strategy for the classical PLS model-the wiretap channel (WTC), where the feedback is not only used to generate key, but also used to produce cooperative information helping the legitimate parties to improve the communication between them. It has been shown that for the general WTC, this hybrid feedback strategy performs better than the already existing secret key based feedback scheme. In this paper, we extend the previous proposed feedback strategy for the WTC to a multi-terminal case, and apply this generalized feedback strategy to the broadcast channel with mutual secrecy requirement (BC-MSR), which constitutes the essence of physical layer security (PLS) in the down-link of the wireless communication systems. From a non-degraded example (Dueck-type broadcast channel), we show that for the BC-MSR, this generalized feedback strategy may perform better than the already existing one.

In this paper, we study the secrecy rate and outage probability in Multiple-Input-Single-Output (MISO) Gaussian broadcast channel at the limit of a large number of legitimate users and eavesdroppers. In particular, we analyze the asymptotic achievable secrecy rates and outage of a secondary user that is superposed on the transmission, when only statistical knowledge on the wiretap channels is available to the transmitter. Doing this, we improve on a previous result which handled the same setting, yet assumed the transmitter serves only a primary user. Herein, we show that a secondary user can be added without affecting the scaling law of the first.

This paper studies the problem of secure communcation over the two-receiver discrete memoryless broadcast channel with one-sided receiver side information and with a passive eavesdropper. We proposed a coding scheme which is based upon the superposition-Marton framework. Secrecy techniques such as the one-time pad, Carleial-Hellman secrecy coding and Wyner serecy coding are applied to ensure individual secrecy. This scheme is shown to be capacity achieving for some cases of the degraded broadcast channel. We also notice that one-sided receiver side information provides the advantage of rate region improvement, in particular when it is available at the weaker legitimate receiver., Comment: Change to results in Theorem 1; improved presentation

In this work, we investigate the performance of Rate-Splitting (RS) based on Tomlinson-Harashima Precoding (THP) in a multiple-antenna broadcast channel with perfect and imperfect Channel State Information at the Transmitter (CSIT). In particular, we consider RS using centralized and decentralized THP structures, where only one user splits its message into a common and private part, and develop expressions to describe the signal-to-interference-plus-noise (SINR) ratio and the sum rates associated with these schemes. Furthermore, we also assess the performance achieved by RS combined with Dirty-Paper Coding (DPC). Simulations show that RS with THP outperforms existing standard THP and RS with linear precoding schemes.

This paper addresses a two-user intensity-modulation direct-detection discrete memoryless free space optical broadcast channel (DM-FSOBC) with nonnegativity, peak and average intensity constraints at the transmitter. It is shown that superposition coding along with generating the codebooks of both users according to discrete distributions with a finite number of mass points, achieve the capacity region of the DM-FSOBC. Although the capacity-achieving distributions are not necessarily unique, it is established that only discrete distributions with a finite number of mass points can achieve the points on the boundary of the capacity region.

In this paper, we address the symbol level precoding (SLP) design problem under max-min SINR criterion in the downlink of multiuser multiple-input single-output (MISO) channels. First, we show that the distance preserving constructive interference regions (DPCIR) are always polyhedral angles (shifted pointed cones) for any given constellation point with unbounded decision region. Then we prove that any signal in a given unbounded DPCIR has a norm larger than the norm of the corresponding vertex if and only if the convex hull of the constellation contains the origin. Using these properties, we show that the power of the noiseless received signal lying on an unbounded DPCIR is an strictly increasing function of two parameters. This allows us to reformulate the originally non-convex SLP max-min SINR as a convex optimization problem. We discuss the loss due to our proposed convex reformulation and provide some simulation results., Submitted to SPAWC 2018, 7 pages, 2 figures

In this paper we classify what arbitrary sources can be transmitted over a discrete memoryless broadcast channel with confidential communications (DM-BCC). Despite allowing completely arbitrary sources and finite error, we show that necessary and sufficient conditions can be expressed in terms of traditional channel capacity regions. As a by-product we also determine the $(\epsilon, \delta)$ -capacity region, and show that even in this more general setting source-channel separation is optimal for the DM-BCC as originally defined.

The capacity region of the three-receiver discrete memoryless less noisy broadcast channel with message cognition is established in the case where the weakest receiver knows the message required by the strongest receiver prior to transmission. This problem was previously studied for the scalar Gaussian broadcast channel by Asadi et al but only inner and outer bounds were obtained. The capacity result of this paper can also be seen to augment the theory of the three-receiver discrete memoryless less noisy broadcast channel for which the capacity region was found previously by Nair and Wang but without message cognition.

In this paper, we find the optimal index coding scheme with transmission time allocation that minimizes overall outage probability in a single-input single-output broadcast channel. In our system model, a transmitter has a set of files (i.e., a file library), and each user requests a single file in the library. Meanwhile, each user has a memory so that may already know some files. When the transmitter can only use limited transmission time to serve the users, the overall outage probability varies according to the index code and transmission time allocation. To find the optimal index code and time allocation, we first derive the optimal time allocation for a given index code. Then, we propose the optimal index code searching algorithm. We also propose a pruning algorithm, which reduces the searching complexity while maintaining the optimality. Our simulation results show that our proposed scheme well minimizes the overall outage probability, and our proposed pruning algorithm significantly reduces the complexity of our proposed scheme.