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Non-orthogonal multiple access (NOMA) with successive interference cancellation (SIC) detection, known as SIC NOMA, enjoys higher spectral efficiency (SE), but suffers increased processing complexity and additional error propagation compared to Non-SIC NOMA, in which the receivers directly detect their own signals from the superposed signal without SIC detection. We propose a joint Mode Selection and Power Allocation (MSPA) scheme that can flexibly realize different kinds of tradeoffs while guaranteeing minimum rate requirements (MRRs) for two-user MISO-NOMA downlink. Specifically, we first obtain rate region boundaries that guarantee two users’ MRRs for two candidate modes: maximum-ratio transmission (MRT)/SIC NOMA and minimum mean square error beamforming (MMSE-BF)/Non-SIC NOMA. We then construct an expression of power allocation factors (transmit power factors) that can satisfy the two users’ MRRs for MRT/SIC NOMA (MMSE-BF/Non-SIC NOMA) by introducing a parameter λ. Finally, we achieve outer boundary of the union of the two modes' rate regions by mode selection and derive expected users' rates on it. Numerical results demonstrate that the proposed MSPA can improve SE and flexibly achieve different kinds of tradeoffs by adjusting λ, while guaranteeing the two users’ MRRs simultaneously for high signal to noise ratio (SNR) scenario and alternately guaranteeing the two users’ MRRs for low SNR scenario.

We investigate the problem of the successive refinement for Wyner-Ziv coding with degraded side information and obtain a complete characterization of the rate region for the quadratic vector Gaussian case. The achievability part is based on the evaluation of the Tian-Diggavi inner bound that involves Gaussian auxiliary random vectors. For the converse part, a matching outer bound is obtained with the aid of a new extremal inequality. Herein, the proof of this extremal inequality depends on the integration of the monotone path argument and the doubling trick as well as information-estimation relations. [ABSTRACT FROM AUTHOR]

In this paper, we combine centralized dynamic-time division duplex (D-TDD) with interference alignment (IA) for a wireless network comprised of $N$ full duplex nodes. We maximize the performance of the proposed centralized D-TDD scheme utilizing IA in terms of rate region by optimizing the reception, transmission, simultaneous reception and transmission, and silence at each node in each time slot in addition to the choice of whether a node should treat the interference as noise or it should use IA. The problem of the rate region maximization of the wireless network is formulated as a non-convex optimization problem, whose optimal solution is found. The simulation results demonstrate that the proposed centralized D-TDD scheme utilizing IA achieves significant gains over the existing D-TDD schemes. [ABSTRACT FROM AUTHOR]

In this paper, we design a NOMA-based spectrum leasing scheme by considering the following three assumptions for the successive interference cancellation (SIC): (i) the primary network performs the SIC (PSIC), (ii) the secondary network performs the SIC (SSIC), (iii) either the primary or secondary network adaptively performs the SIC depending on the channel conditions (ASIC). We first analyze the achievable rate regions of these schemes. Then, we optimize the power allocation to different layers of the superimposed signal by maximizing the achievable rate of the secondary network under a QoS constraint for the primary network. Finally, we analyze these schemes in terms of the outage probability. The analysis shows that: (i) In terms of the primary network, the PSIC and ASIC schemes perform the same and these schemes outperform the SSIC scheme. (ii) In terms of the secondary network, the ASIC scheme outperforms the other two schemes. (iii) In terms of the primary network, the NOMA-based and OMA-based schemes perform the same, provided that the SIC is performed either adaptively or in a fixed manner at the primary network. (iv) In terms of the secondary network, the NOMA-based scheme outperforms the OMA-based scheme, provided that the SIC is performed adaptively. [ABSTRACT FROM AUTHOR]

In the two-user Gaussian interference channel (IFC) with Gaussian inputs and treating interference as noise (TIN), it depends on the assumptions about time-sharing whether improper signals (asymmetric complex signals) can bring benefits over proper signals. If no time-sharing is allowed (pure strategies) or the convex hull formulation is used (only data rates can be averaged), improper signaling can lead to a larger rate region than optimal proper signaling. However, when coded time-sharing is allowed, i.e., both the data rates and the transmit powers can be averaged, the whole rate region can be achieved by proper signaling. Here, we show that the same is true in the multiple-input/single-output (MISO) Z-interference channel (ZIFC). We provide an analytical proof for the optimality of proper signaling in the case of coded time-sharing, and we numerically demonstrate gains by improper signaling in the cases without coded time-sharing. [ABSTRACT FROM AUTHOR]

This paper considers a Gaussian interference channel (IC), where two transmitters send two messages to two receivers respectively. By utilizing the in-band full-duplex (FD) amplify-and-forward (AF) scheme, transmitter cooperations are deployed to enhance the system performance. In particular, each transmitter is capable of listening to its counterpart and then simultaneously transmits both the source signals to achieve higher power gain. Based on the proposed scheme, the equivalent channel model as well as the statistics of the accumulated residual self-interference and noise (ARIN) introduced by the transmitter cooperations and imperfect self-interference (SI) cancellation is analyzed. With the joint and single-user decoding schemes, the corresponding achievable rate regions are derived and a two-stage iterative algorithm is proposed to characterize these regions: in each step, fix the covariance matrix of the interferences and noises, and then adopt a two-step iterative semidefinite relaxation (SDR) method to optimize the two transmitters' transmission parameters, respectively. Simulation results reveal that the proposed scheme can significantly improve the achievable rate under several channel conditions.

Abstract Space-division multiple access (SDMA) utilizes linear precoding to separate users in the spatial domain and relies on fully treating any residual multi-user interference as noise. Non-orthogonal multiple access (NOMA) uses linearly precoded superposition coding with successive interference cancellation (SIC) to superpose users in the power domain and relies on user grouping and ordering to enforce some users to fully decode and cancel interference created by other users. In this paper, we argue that to efficiently cope with the high throughput, heterogeneity of quality of service (QoS), and massive connectivity requirements of future multi-antenna wireless networks, multiple access design needs to depart from those two extreme interference management strategies, namely fully treat interference as noise (as in SDMA) and fully decode interference (as in NOMA). Considering a multiple-input single-output broadcast channel, we develop a novel multiple access framework, called rate-splitting multiple access (RSMA). RSMA is a more general and more powerful multiple access for downlink multi-antenna systems that contains SDMA and NOMA as special cases. RSMA relies on linearly precoded rate-splitting with SIC to decode part of the interference and treat the remaining part of the interference as noise. This capability of RSMA to partially decode interference and partially treat interference as noise enables to softly bridge the two extremes of fully decoding interference and treating interference as noise and provides room for rate and QoS enhancements and complexity reduction. The three multiple access schemes are compared, and extensive numerical results show that RSMA provides a smooth transition between SDMA and NOMA and outperforms them both in a wide range of network loads (underloaded and overloaded regimes) and user deployments (with a diversity of channel directions, channel strengths, and qualities of channel state information at the transmitter). Moreover, RSMA provides rate and QoS enhancements over NOMA at a lower computational complexity for the transmit scheduler and the receivers (number of SIC layers).

In this paper, we introduce an $n$ -channel multilevel imperfect secret sharing problem, which can be regarded as a generalization of secret sharing and a variation of multilevel diversity coding. In this model, a discrete memoryless source (DMS) is encoded into $n$ encoded messages. To measure the secrecy of the system, we introduce a security level for each subset of encoded messages. In the paper, we focus on the $n$ -channel symmetric multilevel imperfect secret sharing (SMISS) problem, i.e., the security levels of all the subsets with the same cardinality are identical. First, we explicitly characterize the coding rate regions for 2-channel and 3-channel SMISS problems. However, it is difficult to characterize the explicit rate region for a general $n$ , since the complexity of designing optimal coding schemes can grow with $n$ exponentially. Nevertheless, we put forward an inner bound and an outer bound on the rate region of the general $n$ -channel SMISS problem. Moreover, we consider two special cases, i.e., the Two-SMISS problem and the linear SMISS problem, and prove that the inner and outer bounds are tight for these two problems, respectively. [ABSTRACT FROM AUTHOR]

The study of optimal properties of centralized dynamic-time-division-duplex (D-TDD) employed at a wireless network consisting of multiple nodes is a highly challenging and partially understood problem in the literature. In this paper, we develop an optimal centralized D-TDD scheme for a wireless network comprised of K full-duplex nodes impaired by self-interference and additive white Gaussian noise. As a special case, we also propose the optimal centralized D-TDD scheme when part or all nodes in the wireless network are half-duplex. Thereby, we derive the optimal adaptive scheduling of the reception, transmission, simultaneous reception and transmission, and silence at every node in the network in each time slot such that the rate region of the network is maximized. The performance of the optimal centralized D-TDD can serve as an upper-bound to any other TDD scheme, which is useful in qualifying the relative performance of TDD schemes. The numerical results show that the proposed centralized D-TDD scheme achieves significant rate gains over existing centralized D-TDD schemes. [ABSTRACT FROM AUTHOR]

In this paper, we consider a multi-cell multi-band downlink where the base station (BS) in each cell has multiple transmit antennas. Each cell has one active mobile station (MS) with a single receive antenna and treats interference from the other cells as noise. There is a sum transmit power constraint for each BS over all the bands. An alternating maximization (AM) algorithm is proposed to determine the optimal power allocation among the bands and the optimal beamforming vectors for each BS in each band. This algorithm can be implemented in a distributed manner with limited exchange of interference constraints between the BSs, and only local channel state information at each BS. The proposed algorithm alternates between: (1) weighted sum-rate (WSR) optimization for the beamformers in each band for a given power allocation, and (2) optimal power allocation across bands for a given set of beamformers. For the 2-cell and 3-cell settings the WSR optimization in each band is significantly simplified using analytical solutions for the sub-problems. The power allocation across bands for a given set of beamformers is obtained analytically in all cases. Numerical results show good convergence properties and significant performance gain using the proposed AM algorithm compared to: (i) equal power allocation across bands and weighted sum-rate optimization in each band, (ii) zero-forcing (ZF) beamforming, and (iii) maximal ratio transmission (MRT) beamforming. [ABSTRACT FROM AUTHOR]

We consider interactive computation of randomized functions between two users with the following privacy requirement: the interaction should not reveal to either user any extra information about the other user’s input and output other than what can be inferred from the user’s own input and output. We also consider the case where privacy is required against only one of the users. For both cases, we give single-letter expressions for feasibility and optimal rates of communication. Then we discuss the role of common randomness and interaction in both privacy settings. We also study perfectly secure non-interactive computation when only one of the users computes a randomized function based on a single transmission from the other user. We characterize randomized functions which can be perfectly securely computed in this model and obtain tight bounds on the optimal message lengths in all the privacy settings. [ABSTRACT FROM AUTHOR]

This paper studies coordinated multipoint (CoMP) transmission with non-orthogonal multiple access (NOMA) for a simultaneous wireless information and power transfer (SWIPT) network. We investigate two different CoMP-NOMA schemes, namely joint transmission-NOMA (JT-NOMA) and Alamouti NOMA (A-NOMA). Also, as the benchmark, joint transmission orthogonal multiple access (JT-OMA) is considered. Expressions are derived for the outage probabilities achieved by JT-NOMA, A-NOMA, and JT-OMA for cell edge users with quality of service (QoS) requirements. To compare these schemes in terms of spectral efficiency, we use the $\epsilon $ -outage rate region that is defined to be the set of all achievable rate pairs at which the outage probabilities are equal to $\epsilon $. It is shown that A-NOMA is superior to both JT-NOMA and JT-OMA in high SNR. Also, it is analytically proved that JT-NOMA outperforms JT-OMA, when the circuit energy consumption is negligible. A particularly interesting observation is that when the circuit energy consumption is non-negligible, JT-NOMA is not always better than JT-OMA. It is shown that when the difference between the expectations of effective channel power gains is not sufficiently large, JT-OMA is superior to JT-NOMA for the same circuit energy consumption. [ABSTRACT FROM AUTHOR]

So-called improper complex signals have been shown to be beneficial in the single-antenna two-user Gaussian interference channel under the assumptions that all input signals are Gaussian and that we treat interference as noise (TIN). This result has been obtained under a restriction to pure strategies without time-sharing, and it was extended to the case where the rates, but not the transmit powers, may be averaged over several transmit strategies. In this paper, we drop such restrictions and discuss the most general case of coded time-sharing, where both the rates and the powers may be averaged. Since coded time-sharing can in general not be expressed by means of a convex hull of the rate region, we have to account for the possibility of time-sharing already during the optimization of the transmit strategy. By means of a novel channel enhancement argument, we prove a surprising result: proper signals are optimal if coded time-sharing is allowed. In addition to establishing this result, we present an algorithm to compute the corresponding achievable rate region. [ABSTRACT FROM AUTHOR]

This article investigates a full-duplex base station using a generalized frequency division multiplexing (GFDM) transceiver with the radio frequency (RF) impairments including phase noise, carrier frequency offset (CFO) and in-phase (I) and quadrature (Q) imbalance. To fully focus on the RF impairment issue, we study the simple configuration of single uplink user and single downlink user. They both are half-duplex wireless. In the uplink, we study analog and digital self-interference (SI) cancellation and propose a complementary SI suppression method. Desired signal and residual SI powers and signal-to-interference ratio (SIR) are derived in closed form. Similarly, in the downlink, we derive desired signal power, co-channel interference signal power caused by the uplink user and SIR. The RF impairments degrade the efficiency of SI cancellation and affect GFDM more negatively than full-duplex orthogonal frequency division multiplexing (OFDM). Hence, we propose full-duplex GFDM receiver filters for maximizing the SIR for both uplink and downlink transmissions. Finally, the uplink and downlink rates and the uplink-downlink rate region are derived. Significantly, the optimal-filter based GFDM outperforms full-duplex OFDM by 25 dB higher SIR and an uplink rate increase of 500%. [ABSTRACT FROM AUTHOR]

Due to its promising performance in a wide range of practical scenarios, Rate-Splitting (RS) has recently received significant attention in academia for the downlink of communication systems. In this letter, we propose and analyse a Cooperative Rate-Splitting (CRS) strategy based on the three-node relay channel where the transmitter is equipped with multiple antennas. By splitting user messages and linearly precoding common and private streams at the transmitter, and opportunistically asking the relaying user to forward its decoded common message, CRS can efficiently cope with a wide range of propagation conditions (disparity of user channel strengths and directions) and compensate for the performance degradation due to deep fading. The precoder design and the resource allocation are optimized by solving the Weighted Sum Rate (WSR) maximization problem. Numerical results demonstrate that our proposed CRS scheme can achieve an explicit rate region improvement compared to its non-cooperative counterpart and other cooperative strategies (such as cooperative NOMA). [ABSTRACT FROM AUTHOR]

We derive an achievable rate region (ARR) of the zero-forcing precoder in a 2 $\times $ 2 multi-user multiple-input single-output broadcast intensity-modulation/direct-detection channel. A per-light emitting diode (LED) peak optical power constraint along with a per-LED average optical power constraint with inequality (Type-I constraint) generally considered in optical wireless communication systems is imposed for which we analytically characterize the boundary of the proposed ARR. Then, we compare this ARR with that under a per-LED peak optical power constraint along with a per-LED average power constraint with equality (Type-II constraint), which is considered in visible light communication systems for constant illumination requirement. Our analysis reveals that when the ratio ($\beta $) of the maximum allowed per-LED average optical transmit power to the per-LED peak power is less than or equal to half ($\beta \leq 1/2$), the ARR under both the constraints is the same. However, Type-I constrained system is analytically shown to be more power efficient in terms of the required total average transmit optical power. When $\beta > 1/2$ , the ARR under the Type-I constraint remains constant with increasing $\beta $ , whereas the ARR under the Type-II constraint shrinks. [ABSTRACT FROM AUTHOR]

Non-orthogonal multiple access (NOMA) with successive interference cancellation (SIC) detection, known as SIC NOMA, enjoys higher spectral efficiency (SE), but suffers increased processing complexity and additional error propagation compared to Non-SIC NOMA, in which the receivers directly detect their own signals from the superposed signal without SIC detection. We propose a joint Mode Selection and Power Allocation (MSPA) scheme that can flexibly realize different kinds of tradeoffs while guaranteeing minimum rate requirements (MRRs) for two-user MISO-NOMA downlink. Specifically, we first obtain rate region boundaries that guarantee two users' MRRs for two candidate modes: maximum-ratio transmission (MRT)/SIC NOMA and minimum mean square error beamforming (MMSE-BF)/Non-SIC NOMA. We then construct an expression of power allocation factors (transmit power factors) that can satisfy the two users' MRRs for MRT/SIC NOMA (MMSE-BF/Non-SIC NOMA) by introducing a parameter λ. Finally, we achieve outer boundary of the union of the two modes' rate regions by mode selection and derive expected users' rates on it. Numerical results demonstrate that the proposed MSPA can improve SE and flexibly achieve different kinds of tradeoffs by adjusting λ , while guaranteeing the two users' MRRs simultaneously for high signal to noise ratio (SNR) scenario and alternately guaranteeing the two users' MRRs for low SNR scenario. [ABSTRACT FROM AUTHOR]

Nonorthogonal multiple access (NOMA) with successive interference cancellation is considered as one of the most promising schemes in multi-user access wireless networks. Based on the principles of NOMA and full-duplex (FD) communications, this paper proposes a novel FD-aided cooperative NOMA (FD-NOMA) scheme to optimize the maximum achievable rate region. Since selfinterference often exists in FD communications, a self-interference canceller is employed in this system. Specifically, three schemes that aim to maximize the achievable rate region are provided. The first one is investigated under the assumption that the transmitted power is fixed, while the other two schemes are achieved with the aid of two developed algorithms. For the purpose of studying the rate region in the nonideality condition, the error vector magnitudelevel is introduced in the analysis of the third scheme. Finally, analytical results demonstrate that the proposed FD-NOMA scheme outperforms the conventional schemes based on NOMA in terms of the rate region, and the maximum rate region of the FD-NOMA scheme is compared with different coefficients.

In this paper, we consider an asynchronous two-way relay network where two single-antenna transceivers are using a single carrier communication scheme to exchange information and incur different delays. It is assumed that the relay nodes can harvest energy from their surrounding environment and utilize this harvested energy to forward their received messages using harvest-then-forward protocol. Since the transceiver-relay paths are subject to different propagation delays, the end-to-end channel can be viewed as a multi-path channel, which can cause inter-block-interference (IBI) in the signal blocks received by the two transceivers. In order to avoid such an IBI, we deploy a relay selection scheme where only those relay nodes are selected that contribute to a single tap end-to-end channel. Our goal is to maximize the sum rate of such a network subject to individual and total power constraints as well as energy harvesting profiles of the relays in order to obtain the maximum achievable rate region. Numerical results show that for a relay selection scheme and considering specific energy harvesting profiles for the relay nodes and under the condition that the total transmit budget of the transceivers are limited, the so obtained achievable rate region is the union of the rate region for each individual tap of the end-to-end channel.

In this paper, we investigate nonorthogonal multiple access (NOMA) for a simultaneous wireless information and power transfer (SWIPT) system consisting of a battery powered access point and two energy harvesting users. In SWIPT, there exists an information-energy tradeoff. Since the adoption of NOMA may cause more energy consumption than the orthogonal multiple access (OMA), it is not known whether NOMA can always enhance the spectral efficiency in SWIPT systems compared to OMA. We prove that NOMA performs better than OMA when the decoding energy consumption is negligible. However, for the nonnegligible decoding energy consumption, we show that NOMA is not always superior to OMA. Interestingly enough, for the nonnegligible decoding energy consumption, OMA can outperform NOMA when the channel power gains of the two users are not sufficiently different. Moreover, we study the performance of cognitive radio inspired NOMA (CR-NOMA), in which the power is allocated to the user with poor channel condition such that its quality of service (QoS) requirement is met. Different from the battery powered CR-NOMA, the analytical results show that CR-NOMA can outperform OMA in SWIPT systems only if the channel power gains of users are sufficiently different and the QoS of the weak user is above a threshold. [ABSTRACT FROM AUTHOR]

We study the achievable rate regions of full-duplex links in the single- and multi-channel cases (in the latter case, the channels are assumed to be orthogonal, e.g., OFDM). We present analytical results that characterize the uplink and downlink rate region and efficient algorithms for computing rate pairs at the region’s boundary. We also provide near-optimal and heuristic algorithms that “convexify” the rate region when it is not convex. The convexified region corresponds to a combination of a few full-duplex rates (i.e., to time sharing between different operation modes). The algorithms can be used for theoretical characterization of the rate region as well as for resource (time, power, and channel) allocation with the objective of maximizing the sum of the rates when one of them (uplink or downlink) must be guaranteed (e.g., due to QoS considerations). We numerically illustrate the rate regions and the rate gains (compared with time division duplex) for various channel and cancellation scenarios. The analytical results provide insights into the properties of the full-duplex rate region and are essential for future development of scheduling, channel allocation, and power control algorithms. [ABSTRACT FROM PUBLISHER]

Recent algorithmic developments have enabled computers to automatically determine and prove the capacity regions of small hypergraph networks under network coding. A structural theory relating network coding problems of different sizes is developed to make the best use of this newfound computational capability. A formal notion of network minimality is developed, which removes components of a network coding problem that are inessential to its core complexity. Equivalence between different network coding problems under relabeling is formalized via group actions, an algorithm which can directly list single representatives from each equivalence class of minimal networks up to a prescribed network size is presented. This algorithm, together with rate region software, is leveraged to create a database containing the rate regions for all minimal network coding problems with five or fewer sources and edges, a collection of 744119 equivalence classes representing more than 9 million networks. In order to best learn from this database, and to leverage it to infer rate regions and their characteristics of networks at scale, a hierarchy between different network coding problems is created with a new theory of combinations and embedding operators. [ABSTRACT FROM PUBLISHER]

It has recently been shown that improper signaling enlarges the rate region of the Gaussian single-antenna one-sided interference channel (Z-interference channel, ZIFC) under the assumptions that all input signals are Gaussian and that interference is treated as noise. It was pointed out that this result also holds if time-sharing between different operation points is allowed. However, the existing literature has considered the problem only for time-sharing under short-term average power constraints, i.e., if the average transmit powers are limited individually in each time slot. We consider the same problem under long-term average power constraints, where the transmit powers are limited only after averaging over all time slots. Interestingly, this modification changes the outcome of the study significantly: we can show that improper signaling can no longer bring any gains in this case. [ABSTRACT FROM PUBLISHER]

In this paper, we consider the $2\times 2$ multiuser multiple-input-single-output (MU-MISO) broadcast visible light communication (VLC) channel with two light emitting diodes (LEDs) at the transmitter and a single photodiode (PD) at each of the two users. We propose an achievable rate region of the zero-forcing precoder in this 2\times 2$ MU-MISO VLC channel under a per-LED peak and average power constraint, where the average optical power emitted from each LED is fixed for constant lighting, but is controllable (referred to as dimming control in IEEE 802.15.7 standard on VLC). We analytically characterize the proposed rate region boundary and show that it is Pareto-optimal. Further analysis reveals that the largest rate region is achieved when the fixed per-LED average optical power is half of the allowed per-LED peak optical power. We also propose a novel transceiver architecture where the channel encoder and dimming control are separated, which greatly simplifies the complexity of the transceiver. A case study of an indoor VLC channel with the proposed transceiver reveals that the achievable information rates are sensitive to the placement of the LEDs and the PDs. An interesting observation is that for a given placement of LEDs in a \text{5}\ \text{m}\times \text{5}\ \text{m}\times \text{3}\ \text{m} room, even with a substantial displacement of the users from their optimum placement, reduction in the achievable rates is not significant. This observation could therefore be used to define “coverage zones” within a room where the reduction in the information rates to the two users is within an acceptable tolerance limit. [ABSTRACT FROM PUBLISHER]

In full-duplex (FD) radios, phase noise leads to random phase mismatch between the self-interference (SI) and the reconstructed cancellation signal, resulting in possible performance degradation during SI cancellation. To explicitly analyze its impacts on the digital SI cancellation, an orthogonal frequency division multiplexing (OFDM)-modulated FD radio is considered with phase noises at both the transmitter and receiver. The closed-form expressions for both the digital cancellation capability and its limit for the large interference-to-noise ratio (INR) case are derived in terms of the power of the common phase error, INR, desired signal-to-noise ratio (SNR), channel estimation error and transmission delay. Based on the obtained digital cancellation capability, the achievable rate region of a two-way FD OFDM system with phase noise is characterized. Then, with a limited SI cancellation capability, the maximum outer bound of the rate region is proved to exist for sufficiently large transmission power. Furthermore, a minimum transmission power is obtained to achieve $\beta$ -portion of the cancellation capability limit and to ensure that the outer bound of the rate region is close to its maximum. [ABSTRACT FROM PUBLISHER]

While full-duplex (FD) transmission has the potential to double system capacity, its substantial benefit can be offset by the self-interference and nonideality of practical transceivers. In this paper, we investigate the achievable sum rates (ASRs) of half-duplex (HD) and FD transmissions with orthogonal frequency-division multiplexing, where nonideality is taken into consideration. Four transmission strategies are considered, namely, HD with uniform power allocation (UPA), HD with non-UPA (NUPA), FD with UPA, and FD with NUPA. For each of the four transmission strategies, an optimization problem is formulated to maximize its ASR, and a (suboptimal/optimal) solution with low complexity is accordingly derived. Performance evaluations and comparisons are conducted for three typical channels, namely, symmetric frequency-flat/selective and asymmetric frequency-selective channels. Results show that the proposed solutions for both HD and FD transmissions can achieve near-optimal performances. For FD transmissions, the optimal solution can be obtained under typical conditions. In addition, several observations are made on the ASR performances of HD and FD transmissions. [ABSTRACT FROM PUBLISHER]

The rate regions of multilevel diversity coding systems (MDCSs), a sub-class of the broader family of multi-source multi-sink networks with special structure, are investigated in a systematic way. We enumerate all non-isomorphic MDCS instances with at most three sources and four encoders. Then, the exact rate region of every one of these more than 7000 instances is proven via computations showing that the Shannon outer bound matches with a custom constructed linear code-based inner bound. Results gained from these computations are summarized in key statistics involving aspects, such as the sufficiency of scalar binary codes, the necessary size of vector binary codes, and so on. Also, it is shown how to construct the codes for an achievability proof. Based on this large repository of rate regions, a series of results about general MDCS cases of arbitrary size that they inspired is introduced and proved. In particular, a series of embedding operations that preserve the property of sufficiency of scalar or vector codes is presented. The utility of these operations is demonstrated by boiling the thousands of MDCS instances for which scalar binary (superposition) codes are insufficient down to 12 (26) forbidden the smallest embedded MDCS instances. [ABSTRACT FROM PUBLISHER]

In this paper, we study the performance of different decoding schemes for multilevel flash memories where each page in every block is encoded independently. We focus on multi-level cell flash memory, which is modeled as a two-user multiple-access channel suffering from asymmetric noise. The uniform rate regions and sum rates of treating interference as noise decoding and successive cancelation decoding are investigated for a program/erase cycling model and a data retention model. We examine the effect of different binary labelings of the cell levels, as well as the impact of further quantization of the memory output (i.e., additional read thresholds). Finally, we extend our analysis to the three-level cell flash memory. [ABSTRACT FROM PUBLISHER]

We establish a new extremal inequality, which is further leveraged to give a complete characterization of the rate region of the vector Gaussian CEO problem with the trace distortion constraint. The proof of this extremal inequality hinges on a careful analysis of the Karush–Kuhn–Tucker necessary conditions for the non-convex optimization problem associated with the Berger–Tung scheme, which enables us to integrate the perturbation argument by Wang and Chen and the distortion projection method by Rahman and Wagner. [ABSTRACT FROM AUTHOR]

This paper studies the symmetric two-user Gaussian interference channel where the transmitters harvest randomly arrived energies and share the harvested energy with each other for energy cooperation. We characterize the achievable average rate region of the interference channel with time-varying available power when the simplified Han-Kobayashi scheme, known as a near-optimal transmission strategy for the conventional two-user Gaussian interference channel, is employed. We prove that each corner point on the average rate region is on a sum rate bound with appropriate power allocation. Based on the proof, we find the optimal strategy of energy cooperation and power allocation between the two transmitters to achieve the boundary points on the average rate region. It is shown that the energy cooperation can enlarge the average rate region compared to that of the conventional interference channel. We also show that the energy cooperation yields almost the same average rate region regardless of the interference channel condition because it enables to effectively change the given interference channel condition into a more favorable one by flexibly controlling the transmit powers. [ABSTRACT FROM AUTHOR]

In distributed multilevel diversity coding, $K$ correlated sources (each with $K$ components) are encoded in a distributed manner such that, given the outputs from any $\alpha $ encoders, the decoder can reconstruct the first $\alpha $ components of each of the corresponding $\alpha $ sources. For this problem, the optimality of a multilayer Slepian-Wolf coding scheme based on binning and superposition is established when $K\leq 3$ . The same conclusion is shown to hold for general $K$ under a certain symmetry condition, which generalizes a celebrated result by Yeung and Zhang. [ABSTRACT FROM PUBLISHER]

We investigate the spectral efficiency gain of an uplink cognitive radio (CR) multi-input-multi-output system in which the secondary user (SU) is allowed to share the spectrum with the primary user (PU) using a specific precoding scheme to communicate with a common receiver. The proposed scheme exploits, at the same time, the free eigenmodes of the primary channel after a space alignment procedure and the interference threshold tolerated by the PU. At the common receiver, we adopt a successive interference cancellation (SIC) technique to eliminate the effect of the detected primary signal transmitted through the exploited eigenmodes. Furthermore, we analyze the SIC operation inaccuracy as well as the CSI estimation imperfection on the PU and SU throughputs. Numerical results show that our proposed scheme enhances considerably the cognitive achievable rate. For instance, in case of a perfect detection of the PU signal, the CR rate remains non-zero for high signal to noise ratio, which is usually impossible when we only employ a space alignment technique. We show that a modified water-filling power allocation policy at the PU can increase the secondary rate with a marginal degradation of the primary rate. Finally, we investigate the behavior of the PU and SU rates through the study of the rate achievable region. [ABSTRACT FROM PUBLISHER]

A polar coding scheme is proposed for the multiple description coding (MDC) problem and is shown to be able to achieve a certain rate pair on the dominant line of the achievable rate region determined by El Gamal and Cover. This scheme is an adaptation of the one developed by Şaşoğlu et al. for the multiple access channel (MAC) to the MDC setting. The analysis of the proposed scheme contains two new ingredients: 1) a certain MDC-MAC duality and 2) an auxiliary random process that involves both the mutual information and the Bhattacharyya parameter. The decorrelation effect of the polar transform is also investigated. [ABSTRACT FROM PUBLISHER]

We consider the classical two-encoder multiterminal source coding problem where distortion is measured under logarithmic loss. We provide a single-letter description of the achievable rate distortion region for all discrete memoryless sources with finite alphabets. By doing so, we also give the rate distortion region for the m-encoder CEO problem (also under logarithmic loss). Several applications and examples are given. [ABSTRACT FROM PUBLISHER]

In this paper, we provide an information-theoretic analysis of a Gaussian multiple-input multiple-output multiple access channel (MIMO MAC) with imperfect channel knowledge at the receiver. In particular, we derive inner and outer bounds for the MIMO MAC rate region when the inputs are Gaussian. We then apply these bounds to a Gaussian interference network with receiver cooperation, in which a central processor with incomplete channel state information must jointly decode all the received signals. Then, in the case where the channel knowledge at the receiver is obtained through training signals, we derive the structure of the optimum training signals for all users under a definite and semidefinite rank constraint. Numerical results show that the bounds we derive can be quite tight, confirming the asymptotic analysis conducted for the finite case. Finally, we also investigate the low-SNR and high-SNR regimes, specifically analyzing the minimum required energy per information bit and the wideband slope region in the first case, and the high-SNR slope in the second. [ABSTRACT FROM AUTHOR]

In this paper, we consider a two-hop interference network, which consists of two source-destination pairs and two relay nodes connected with signal-to-noise ratio (SNR) limited out-of-band conferencing links. Assuming that the amplify-and-forward (AF) relaying scheme is adopted, this network is shown to be equivalent to a two-user interference channel (IC). By deploying two IC decoding schemes, i.e., single-user decoding and joint decoding, respectively, we characterize the achievable rate regions with a two-stage iterative optimization method: First, we fix the source power pair and maximize the sum rate over the relay combining vector; second, we fix the relay combining vector and optimize the source power pair. Specifically, for single-user decoding, we design a new routine to compute the optimal solution for the first subproblem, which is more efficient than the existing scheme; and for the second subproblem, we develop an iterative algorithm, with the closed-form solution for each iteration. Furthermore, it is revealed that the AF scheme with relay conferencing achieves the full degree-of-freedom (DoF), which outperforms the case without relay conferencing. Finally, simulation results show that relay conferencing can significantly improve the system performance under certain channel conditions. [ABSTRACT FROM PUBLISHER]

We characterize the (nonconvex) rate region and its maximal convex subsets for carrier-sense multiple-access with collision-avoidance (CSMA/CA) wireless local-area networks (WLANs), and in particular for 802.11 WLANs. In addition to being of intrinsic interest as fundamental properties of CSMA/CA WLANs, this characterization can be exploited to allow the wealth of convex optimization approaches to be applied to CSMA/CA WLANs, especially to utility fair resource allocation problems. [ABSTRACT FROM PUBLISHER]

We derive a lower bound on each supporting line of the rate region of the vector Gaussian two-terminal CEO problem, which is a special case of the indirect vector Gaussian two-terminal source coding problem. The key technical ingredient is a new extremal inequality. It is shown that the lower bound coincides with the Berger–Tung upper bound in the high-resolution regime. Similar results are derived for the direct vector Gaussian two-terminal source coding problem. [ABSTRACT FROM PUBLISHER]

Symmetrical multilevel diversity coding (SMDC) is a network compression problem introduced by Roche (1992) and Yeung (1995). In this setting, a simple separate encoding strategy known as superposition coding was shown to be optimal in terms of achieving the minimum sum rate (Roche–Yeung–Hau 1997) and the entire admissible rate region (Yeung–Zhang 1999) of the general problem. This paper considers a natural generalization of SMDC to the secure communication setting with an additional eavesdropper. It is required that all sources need to be kept perfectly secret from the eavesdropper as long as the number of encoder outputs available at the eavesdropper is no more than a given threshold. First, the problem of encoding individual sources is studied. A precise characterization of the entire admissible rate region is established via a connection to the problem of ramp-type secret sharing (Yamamoto 1985 and Blakley–Meadows 1985) and utilizing some basic polyhedral structure of the admissible rate region. Building on this result, it is then shown that superposition coding remains optimal in terms of achieving the minimum sum rate for the general secure SMDC problem. [ABSTRACT FROM PUBLISHER]

We present a new proof of a celebrated result of Gács and Körner that the common information is far less than the mutual information. Consider two sequences \alpha1,\ldots\alphan and \beta1,\ldots,\betan of random variables, where pairs (\alpha1,\beta1),\ldots, (\alphan,\betan) are independent and identically distributed. Gács and Körner proved that it is not possible to extract “common information” from these two sequences unless the joint distribution matrix of random variables (\alphai,\betai) is a block matrix. [ABSTRACT FROM PUBLISHER]

This paper considers a distributed source coding (DSC) problem where L encoders observe noisy linear combinations of K correlated remote Gaussian sources, and separately transmit the compressed observations to the decoder to reconstruct the remote sources subject to a sum-distortion constraint. This DSC problem is referred to as the generalized Gaussian CEO problem since it can be viewed as a generalization of the quadratic Gaussian CEO problem where the number of remote source K=1. First, we provide a new outer region obtained using the entropy power inequality and an equivalent argument (in the sense of having the same rate-distortion region and Berger–Tung inner region) among a certain class of generalized Gaussian CEO problems. We then give two sufficient conditions for our new outer region to match the inner region achieved by Berger–Tung schemes, where the second matching condition implies that in the low-distortion regime, the Berger–Tung inner rate region is always tight, while in the high-distortion regime, the same region is tight if a certain condition holds. The sum-rate part of the outer region is also studied and shown to meet the Berger–Tung sum-rate upper bound under a certain condition, which is obtained using the Karush–Kuhn–Tucker conditions of the underlying convex semidefinite optimization problem, and is in general weaker than the aforesaid two for rate region tightness. [ABSTRACT FROM PUBLISHER]