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From both practical and theoretical viewpoints, performance analysis of communication systems using information-theoretic results is very important. In this study, first, we obtain a general achievable rate for a two-user wireless multiple access channel (MAC) with specially correlated sources as a more general version for continuous alphabet MACs, by extending the known discrete alphabet results to the wireless continuous alphabet version. Next, the impact of wireless channel coefficients correlation on the performance metrics using Copula theory, as the most convenient way for describing the dependence between several variables, is investigated. By applying the Farlie-Gumbel-Morgenstern (FGM) Copula function, we obtain closed-form expressions for the outage probability (OP) under positive/negative dependence conditions. It is shown that the fading correlation improves the OP for a negative dependence structure. Specifically, whenever the dependence structure tends to negative values, the OP decreases and the efficiency of the channel increases. Finally, the efficiency of the analytical results is illustrated numerically.

This letter investigates an over-the-air federated learning (OTA-FL) system that employs fluid antennas (FAs) at the access point (AP) to enhance learning performance by leveraging the additional degrees of freedom provided by antenna mobility. First, we analyze the convergence of the OTA-FL system and derive the optimality gap to illustrate the influence of FAs on learning performance. Then, we formulate a nonconvex optimization problem to minimize the optimality gap by jointly optimizing the positions of the FAs and the beamforming vector. To address the dynamic environment, we cast this optimization problem as a Markov decision process (MDP) and propose the recurrent deep deterministic policy gradient (RDPG) algorithm. Finally, extensive simulations show that the FA-assisted OTA-FL system outperforms systems with fixed-position antennas and that the RDPG algorithm surpasses the existing methods., Comment: 5 pages, 3 figures

Oscillator output generally has phase noise causing the output power spectral density (PSD) to disperse around a Dirac delta function. In this paper, the AWGN channel is considered, where the sent signal accompanying with phase noise is added to the channel Gaussian noise and received at the receiver. Conventional channel estimation algorithms such as least mean square (LMS) and mean MSE criterion are not suitable for this channel estimation. We (i) analyze this phase noise channel estimation with information theoretic learning (ITL) criterion, i.e., maximum correntropy criterion (MCC), leading to robustness in the channel estimator's steady state behavior; and (ii) improve the convergence rate by combining MSE and MCC as a novel mixed-LMS algorithm., Comment: We will upload a more concise version of the article at a later stage

We investigate the impact of fading correlation on the performance of the doubly dirty fading multiple access channel (MAC) with non-causally known side information at transmitters. Using Copula theory, we derive closed-form expressions for the outage probability and the coverage region under arbitrary dependence conditions. We show that a positive dependence structure between the fading channel coefficients is beneficial for the system performance, as it improves the outage probability and extends the coverage region compared to the case of independent fading. Conversely, a negative dependence structure has a detrimental effect on both performance metrics.

In this paper, we consider the massive non-orthogonal multiple access (NOMA) with hybrid automatic repeat request (HARQ) for short packet communications. To reduce the latency, each user can perform one re-transmission provided that the previous packet was not decoded successfully. The system performance is evaluated for both coordinated and uncoordinated transmissions. We first develop a Markov model (MM) to analyze the system dynamics and characterize the packet error rate (PER) and throughput of each user in the coordinated scenario. The power levels are then optimized for two scenarios, including the power constrained and reliability constrained scenarios. A simple yet efficient dynamic cell planning is also designed for the uncoordinated scenario. Numerical results show that both coordinated and uncoordinated NOMA-HARQ with a limited number of retransmissions can achieve the desired level of reliability with the guaranteed latency using a proper power control strategy. Results also show that NOMA-HARQ achieves a higher throughput compared to the orthogonal multiple access scheme with HARQ under the same average received power constraint at the base station.

It is known that, as opposed to point-to-point channel, separate source and channel coding is not optimal in general for sending correlated sources over multiuser channels. In some works joint source-channel coding has been investigated for some certain multiuser channels; i.g., multiple access channel (MAC) and broadcast channel (BC). In this paper, we obtain a sufficient condition for transmitting arbitrarily correlated sources over a discrete memoryless BC with cooperating receivers, where the receivers are allowed to exchange messages via a pair of noisy cooperative links. It is seen that our results is a general form of previous ones and includes them as its special cases., Comment: to appear in Proceedings of IEEE Information Theory Workshop - Fall (ITW'2015)

In this paper, a new and general version of Gaussian channel in presence of two-sided state information correlated to the channel input and noise is considered. Determining a general achievable rate for the channel and obtaining the capacity in a non-limiting case, we try to analyze and solve the Gaussian version of the Cover-Chiang theorem -as an open problem- mathematically and information-theoretically. Our capacity theorem, while including all previous theorems as its special cases, explains situations that can not be analyzed by them; for example, the effect of the correlation between the side information and the channel input on the capacity of the channel that can not be analyzed with Costa's "writing on dirty paper" theorem. Meanwhile, we try to introduce our new idea, i.e., describing the concept of "cognition" of a communicating object (transmitter, receiver, relay and so on) on some variable (channel noise, interference and so on) with the information-theoretic concept of "side information" correlated to that variable and known by the object. According to our theorem, the channel capacity is an increasing function of the mutual information of the side information and the channel noise. Therefore our channel and its capacity theorem exemplify the "cognition" of the transmitter and receiver on the channel noise based on the new description. Our capacity theorem has interesting interpretations originated from this new idea., Comment: submitted to IEEE Transactions on Information Theory

In this paper we study and analyze coverage region for half-duplex multiple-input multiple-output (MIMO) relay channel with amplify-and-forward (AF) strategy at the relay station. By assuming mixed Rayleigh and Rician fading channels with two different relay station situations, we consider the objective of maximizing coverage region for a given transmission rate and find the optimal relay location in the sense of maximizing coverage region. using Monte Carlo simulations, the coverage region and capacity bounds are shown for different fading cases and different relay station locations. Finally, we compare our results with previous ones obtained for decode-and-forward (DF) MIMO relay channel., Comment: Accepted for publication in Seventh International Symposium on Telecommunications (IST'2014)

The fact that the results for 2-receiver broadcast channels (BCs) are not generalized to the 3-receiver ones is of information theoretical importance. In this paper we study two classes of discrete memoryless BCs with non-causal side information (SI), i.e. multilevel BC (MBC) and 3-receiver less noisy BC. First, we obtain an achievable rate region and a capacity outer bound for the MBC. Second, we prove a special capacity region for the 3-receiver less noisy BC. Third, the obtained special capacity region for the 3-receiver less noisy BC is extended to continuous alphabet fading Gaussian version. It is worth mentioning that the previous works are special cases of our works., Comment: 24 pages, 2 figures, Submitted to IET Communications Journal for possible publication

In this paper, we propose a generalized write channel model for bit-patterned media recording by considering all sources of errors causing some extra disturbances during write process, in addition to data dependent write synchronization errors. We investigate information-theoretic bounds for this new model according to various input distributions and also compare it numerically to the last proposed model., Comment: Accepted for publication in the IEEE International Symposium on Information Theory and its Applications (ISITA 2014), Melbourne, Australia, Oct. 2014

We study and analyze coverage region in MIMO communication systems for a multiple-relay network with decode-and-forward (DF) strategy at the relays. Assuming that there is a line-of-sight (LOS) propagation environment for source-relay channels and channel state information is available at receivers (CSIR), we consider the objective of maximizing coverage region for a given transmission rate and show numerically the significant effect of propagation environment on capacity bounds, optimal relay location and coverage region. Also, we study the situation in which two adjacent relays cooperate in transmission signals to the destination and show analytically that the coverage region is extended compared to noncooperative scenario., Comment: Accepted for publication in International Symposium on Wireless Communication Systems (ISWCS) 2014

In this paper, we study relay networks with orthogonal components in presence of noncausal channel state information (CSI) available at the source. We propose an upper bound on the capacity of the discrete memoryless model (DM)for the case in which just the source component intended for the destination is encoded against the CSI known non-causally at the source. Also, we derive capacity for two special classes of the Gaussian structure of the model. The first class is the one for which we have obtained the upper bound and the second class is the one in which all of the source components intended for the relays and destination are encoded against the noncausal CSI, however, no interference at the relays and destination exists in this case., Comment: This paper has been withdrawn by the author due to an error in derivation of a relation

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)., Comment: 13 pages, 4 figures, This paper is partially presented at 2012 IEEE International Symposium on Information Theory

The additive exponential noise channel with additive exponential interference (AENC-AEI) known non-causally at the transmitter is studied. This channel can be considered as an exponential version of the discrete memoryless channel with state known non-causally at the encoder considered by Gelfand and Pinsker. We make use of Gelfand-Pinsker classic capacity Theorem to derive inner and outer bounds on the capacity of this channel under a non-negative input constraint as well as a constraint on the mean value of the input. First we obtain an outer bound for AENC-AEI. Then by using the input distribution achieving the outer bound, we derive an inner bound which this inner bound coincides with the obtained outer bound at high signal to noise ratios (SNRs) and therefore, gives the capacity of the AENC-AEI at high SNRs., Comment: 7 pages, 2 figures

In this paper, we characterize the capacity region for the two-user linear Gaussian compound Multiple Access Channel with common message (MACC) and with intersymbol interference (ISI) under an input power constraint. The region is obtained by converting the channel to its equivalent memoryless one by defining an n-block memoryless circular Gaussian compound MACC model and applying the discrete Fourier transform (DFT) to decompose the n-block channel into a set of independent parallel channels whose capacities can be found easily. Indeed, the capacity region of the original Gaussian compound MACC equals that of the n-block circular Gaussian compound MACC in the limit of infinite block length. Then by using the obtained capacity region, we derive the capacity region of the strong interference channel with common message and ISI., Comment: 5 pages, 2 figures, This paper is presented at the International Symposium on Telecommunications (IST)

In this paper, we examine discrete memoryless Multiple Access Channels (MACs) with two-sided feedback in the presence of two correlated channel states that are correlated in the sense of Slepian-Wolf (SW). We find achievable rate region for this channel when the states are provided non-causally to the transmitters and show that our achievable rate region subsumes Cover-Leung achievable rate for the discrete memoryless MAC with two-sided feedback as its special case. We also find the capacity region of discrete memoryless MAC with two-sided feedback and with SW-type correlated states available causally or strictly causally to the transmitters. We also study discrete memoryless MAC with partial feedback in the presence of two SW-type correlated channel states that are provided non-causally, causally, or strictly causally to the transmitters. An achievable rate region is found when channel states are non-causally provided to the transmitters whereas capacity regions are characterized when channel states are causally, or strictly causally available at the transmitters., Comment: 10 pages, 4 figures

In this paper we investigate the optimal relay location in the sense of maximizing suitably defined coverage region for MIMO relay channel. We consider the general Rayleigh fading case and assume that the channel state information is only available at the receivers (CSIR), which is an important practical case in applications such as cooperative vehicular communications. In order to overcome the mathematical difficulty regarding determination of the optimal relay location, we provide two analytical solutions, and show that it is possible to determine the optimal relay location (for a desired transmission rate) at which the coverage region is maximum. Monte Carlo simulations confirm the validity of the analytical results. Numerical results indicate that using multiple antennas increases coverage region for a fixed transmission rate, and also increases the transmission rate linearly for a fixed coverage., Comment: To appear in 9th IEEE International Symposium on Wireless Communication Systems (ISWCS'2012)

In this paper, we establish achievable rate regions for the multiple access channel (MAC) with side information partially known (estimated or sensed version) at the transmitters. Actually, we extend the lattice strategies used by Philosof-Zamir for the MAC with full side information at the transmitters to the partially known case. We show that the sensed or estimated side information reduces the rate regions, the same as that occurs for Costa Gaussian channel., Comment: 5 pages, 3 figures, This paper was accepted at IEEE-ISIT2012

In this paper, we study, information theoretically, the impact of transmitter and or receiver cognition on the channel capacity. The cognition can be described by state information, dependent on the channel noise and or input. Specifically, as a new idea, we consider the receiver cognition as a state information dependent on the noise and we derive a capacity theorem based on the Gaussian version of the Cover-Chiang capacity theorem for two-sided state information channel. As intuitively expected, the receiver cognition increases the channel capacity and our theorem shows this increase quantitatively. Also, our capacity theorem includes the famous Costa theorem as its special cases., Comment: submitted to IEEE Communications Letters

In this paper, we derive UWB version of (i) general best achievable rate for the relay channel with decode-andforward strategy and (ii) max-flow min-cut upper bound, such that the UWB relay channel can be studied considering the obtained lower and upper bounds. Then, we show that by appropriately choosing the noise correlation coefficients, our new upper bound coincides with the lower bound in special cases of degraded and reversely degraded UWB relay channels. Finally, some numerical results are illustrated., Comment: 5 pages, 3 figures, accepted for publication and presentation at ISWCS 2011, Aachen, Germany, 6th-9th November

In this paper (a) after detailed investigation of the previous equivalent rate regions for general interference channel, i.e., the Han-Kobayashi (HK) and the Chong-Motani-Garg (CMG) regions, we define modified CMG region the equivalency of which with the HK region is readily seen; (b) we make two novel changes in the HK coding. First, we allow the input auxiliary random variables to be correlated and, second, exploit the powerful technique of random binning instead of the HK -CMG superposition coding, thereby establishing a new rate region for general interference channel, as an improved version of the HK region; (c) we make a novel change in the CMG coding by allowing the message variables to be correlated and obtain an equivalent form for our new region in (b), as an improved version of the CMG region. Then, (d) in order to exactly demarcate the regions, by considering their different easily comparable versions, we compare our region to the HK and CMG regions. Specifically, using a simple dependency structure for the correlated auxiliary random variables, based on the Wyner and Gacs-Korner common information between dependent variables, we show that the HK and the CMG regions are special cases of our new region. Keywords. Interference channel, Correlated auxiliary random variables, Common information, Superposition coding, Binning scheme, Comment: 23 pages, new and revised version, sumitted to IEEE Trans. on Information Thory, Sept.2011

In this paper, we obtain a general achievable rate region and some certain capacity theorems for multiple-access relay channel (MARC), using decode and forward (DAF) strategy at the relay, superposition coding at the transmitters. Our general rate region (i) generalizes the achievability part of Slepian-Wolf multiple-access capacity theorem to the MARC, (ii) extends the Cover-El Gamal best achievable rate for the relay channel with DAF strategy to the MARC, (iii) gives the Kramer-Wijengaarden rate region for the MARC, (iv) meets max-flow min-cut upper bound and leads to the capacity regions of some important classes of the MARC., Comment: 5 pages, 1 figure

The cognitive radio channel with common message (CRCC) is considered. In this channel, similar to the cognitive radio channel (CRC), we have a cognitive user which has full non-causal knowledge of the primary message, and like the interference channel with common message (ICC), the information sources at the two transmitters are statistically dependent and the senders need to transmit not only the private message but also certain common message to their corresponding receivers. By using a specific combination of superposition coding, binning scheme and simultaneous decoding, we propose a unified achievable rate region for the CRCC which subsumes the several existing results for the CRC, ICC, interference channel without common message (IC), strong interference channel and compound multiple access channel with common information (SICC and CMACC)., Comment: 5 pages, 2 figures, accepted for publication and presentation at ISWCS 2011, Aachen, Germany, 6th - 9th November, 2011

Allowing the input auxiliary random variables to be correlated and using the binning scheme, the Han-Kobayashi (HK) rate region for general interference channel is partially improved. The obtained partially new achievable rate region (i) is compared to the HK region and its simplified description, i.e., Chong-Motani-Garg (CMG) region, in a detailed and favorable manner, by considering different versions of the regions, and (ii) has an interesting and easy interpretation: as expected, any rate in our region has generally two additional terms in comparison with the HK region (one due to the input correlation and the other as a result of the binning scheme). Keywords. Interference channel, Input correlation, Binning scheme, Comment: Submitted to IEEE Trans. on Information Theory as version 2, on 28 Dec.2010,presented in part at ICT 2010,April,Doha,Qatar and at IT workshop,June 2010,Sharif Univ. of Tech

Considering a general input distribution, using Gel'fand-Pinsker full binning scheme and the Han- Kobayashi (HK) jointly decoding strategy, we obtain a new achievable rate region for the cognitive radio channel (CRC) and then derive a simplified description for the region, by a combination of Cover superposition coding, binning scheme and the HK decoding technique. Our rate region (i) has an interesting interpretation, i.e., any rate in the region, as expected, has generally three additional terms in comparison with the KH region for the interference channel (IC): one term due to the input correlation, the other term due to binning scheme and the third term due to the interference dependent on the inputs, (ii) is really a generalization of the HK region for the IC to the CRC by the use of binning scheme, and as a result of this generalization we see that different versions of our region for the CRC are reduced to different versions of the previous results for the IC, and (iii) is a generalized and improved version of previous results ,i.g., the Devroye-Mitran-Tarokh (DMT) region., Comment: Submitted to IEEE Trans. on Information Theory, on July 2010

Allowing the input auxiliary random variables to be correlated and using the binning scheme, the Han- Kobayashi (HK) rate region for general interference channel is improved. The obtained new achievable rate region (i) is shown to encompass the HK region and its simplified description, i.e., Chong-Motani-Garg (CMG) region,considering a detailed and favorable comparison between different versions of the regions, and (ii) has an interesting and easy interpretation: as expected, any rate in our region has generally two additional terms in comparison with the HK region (one due to the input correlation and the other as a result of the binning scheme)., Comment: submitted to IEEE Trans.on Information theory, on June 27