Relay Broadcast Channel Research Articles

Uplink-Downlink Duality Between Multiple-Access and Broadcast Channels With Compressing Relays

Uplink-downlink duality refers to the fact that under a sum-power constraint, the capacity regions of a Gaussian multiple-access channel and a Gaussian broadcast channel with Hermitian transposed channel matrices are identical. This paper generalizes this result to a cooperative cellular network, in which remote access-points are deployed as relays in serving the users under the coordination of a central processor (CP). In this model, the users and the relays are connected over noisy wireless links, while the relays and the CP are connected over noiseless but rate-limited fronthaul links. Based on a Lagrangian technique, this paper establishes a duality relationship between such a multiple-access relay channel and broadcast relay channel, under the assumption that the relays use compression-based strategies. Specifically, we show that under the same total transmit power constraint and individual fronthaul rate constraints, the achievable rate regions of the Gaussian multiple-access and broadcast relay channels are identical, when either independent compression or Wyner-Ziv and multivariate compression strategies are used. The key observations are that if the beamforming vectors at the relays are fixed, the sum-power minimization problems under the achievable rate and fronthaul constraints in both the uplink and the downlink can be transformed into either a linear programming or a semidefinite programming problem depending on the compression technique, and that the uplink and downlink problems are Lagrangian duals of each other. Moreover, the dual variables corresponding to the downlink rate constraints become the uplink powers; the dual variables corresponding to the downlink fronthaul constraints become the uplink quantization noises. This duality relationship enables an efficient algorithm for optimizing the downlink transmission and relaying strategies based on the uplink.

Capacity Limits of Full-Duplex Cellular Network

This paper aims to characterize the capacity limits of a wireless cellular network with a full-duplex (FD) base-station (BS) and half-duplex user terminals, in which three independent messages are communicated: the uplink message $m_1$ from the uplink user to the BS, the downlink message $m_2$ from the BS to the downlink user, and the device-to-device (D2D) message $m_3$ from the uplink user to the downlink user. From an information theoretical perspective, the overall network can be viewed as a generalization of the FD relay broadcast channel with a side message transmitted from the relay to the destination. We begin with a simpler case that involves the uplink and downlink transmissions of $(m_1,m_2)$ only, and propose an achievable rate region based on a novel strategy that uses the BS as a FD relay to facilitate the interference cancellation at the downlink user. We also prove a new converse, which is strictly tighter than the cut-set bound, and characterize the capacity region of the scalar Gaussian FD network without a D2D message to within a constant gap. This paper further studies a general setup wherein $(m_1,m_2,m_3)$ are communicated simultaneously. To account for the D2D message, we incorporate Marton's broadcast coding into the previous scheme to obtain a larger achievable rate region than the existing ones in the literature. We also improve the cut-set bound by means of genie and show that by using one of the two simple rate-splitting schemes, the capacity region of the scalar Gaussian FD network with a D2D message can already be reached to within a constant gap. Finally, a generalization to the vector Gaussian channel case is discussed. Simulation results demonstrate the advantage of using the BS as relay in enhancing the throughput of the FD cellular network.

On the Capacity Regions of Degraded Relay Broadcast Channels with and without Feedback.

The four-node relay broadcast channel (RBC) is considered, in which a transmitter communicates with two receivers with the assistance of a relay node. We first investigate three types of physically degraded RBCs (PDRBCs) based on different degradation orders among the relay and the receivers’ observed signals. For the discrete memoryless (DM) case, only the capacity region of the second type of PDRBC is already known, while for the Gaussian case, only the capacity region of the first type of PDRBC is already known. In this paper, we step forward and make the following progress: (1) for the first type of DM-PDRBC, a new outer bound is established, which has the same rate expression as an existing inner bound, with only a slight difference on the input distributions; (2) for the second type of Gaussian PDRBC, the capacity region is established; (3) for the third type of PDRBC, the capacity regions are established both for DM and Gaussian cases. Besides, we also consider the RBC with relay feedback where the relay node can send the feedback signal to the transmitter. A new coding scheme based on a hybrid relay strategy and a layered Marton’s coding is proposed. It is shown that our scheme can strictly enlarge Behboodi and Piantanida’s rate region, which is tight for the second type of DM-PDRBC. Moreover, we show that capacity regions of the second and third types of PDRBCs are exactly the same as that without feedback, which means feedback cannot enlarge capacity regions for these types of RBCs.

Routing Methodology for Secure Transmission of data in Physical Layer

The difficulties of privacy and security in WANETs have taken on a step by step more vital responsibility as those networks persist to increase their role globally. Historically, physical layer is regarded as biased function addressed below the security, and all broadly used cryptographic protocols like Rivest-Shamir–adlemen, Advanced encryption standard and Data Encryption standard are developed and applied assuming an error-free physical layer already exists . Contrasting the traditional cryptography hwhich neglects distinction among the communication channels, the current physical layer safety accomplish data protection using well designing channel code consistent with the channel capacities assuming that the authentic data can never be recovered. The standard system protection makes use of encryption and deciphering activities inside the application layer. Under any circumstances, this won't just construct the computational overhead of system. There's no actual way to avoid eavesdropper listening in and assault from the physical layer. Addressing this problem, this paper proposes a basic system model in which the cooperative relay broadcast channel with the user cooperation is introduced and the overall performance metrics based on the physical layer safety can viably enhance the system protection limit.

Downlink Cooperative Broadcast Transmission Based on Superposition Coding in a Relaying System for Future Wireless Sensor Networks.

This study investigates the superiority of cooperative broadcast transmission over traditional orthogonal schemes when applied in a downlink relaying broadcast channel (RBC). Two proposed cooperative broadcast transmission protocols, one with an amplify-and-forward (AF) relay, and the other with a repetition-based decode-and-forward (DF) relay, are investigated. By utilizing superposition coding (SupC), the source and the relay transmit the private user messages simultaneously instead of sequentially as in traditional orthogonal schemes, which means the channel resources are reused and an increased channel degree of freedom is available to each user, hence the half-duplex penalty of relaying is alleviated. To facilitate a performance evaluation, theoretical outage probability expressions of the two broadcast transmission schemes are developed, based on which, we investigate the minimum total power consumption of each scheme for a given traffic requirement by numerical simulation. The results provide details on the overall system performance and fruitful insights on the essential characteristics of cooperative broadcast transmission in RBCs. It is observed that better overall outage performances and considerable power gains can be obtained by utilizing cooperative broadcast transmissions compared to traditional orthogonal schemes.

MIMO relaying networks for cooperative spectrum sensing: False alarm and detection probabilities

In this paper, we investigate spectrum sensing in cooperative networks. Hence, in order to enhance cooperative sensing, we propose a novel model based on multiple-input multiple-output (MIMO) relaying broadcast channels with direct link and cognitive radio technology. Despite their efficiency in increasing transmission rates and networks capacities, MIMO relays have not yet been exploited for enhancing spectrum sensing. In this case, each relay is equipped with many antennas and the primary signal samples are collected by both MIMO relays and secondary user. Furthermore, we derive new expressions for the false alarm and detection probabilities as well as the detection threshold. Performance analysis are made for both soft and hard cooperative spectrum sensing schemes. Considering Gaussian and impulsive noise environments, simulations show that the proposed model allows a significant detection performance gain compared to non-cooperative cognitive MIMO models.

Research on capacity region of Gaussian degraded relay broadcast channel

Research on capacity region of Gaussian degraded relay broadcast channel

Joint Source and Relay Beamformer Design for General MIMO Relaying Broadcast Channel with Imperfect Channel State Information

Joint Source and Relay Beamformer Design for General MIMO Relaying Broadcast Channel with Imperfect Channel State Information

Improving Non-Orthogonal Multiple Access by Forming Relaying Broadcast Channels

In this letter, the performance of non-orthogonal multiple access (NOMA) with full-duplex relaying is investigated in multi-user single-input single-output downlink systems. Contrary to the original NOMA, in the proposed NOMA scheme, the base station (BS) and two served receivers within a resource block form a relaying broadcast channel (RBC), where one of the two receivers serves as a relay as well as a receiver. To analyze the performance of the proposed scheme, a simple achievable rate region of an RBC with compress-and-forward (CF) relaying is newly derived based on the noisy network coding (NNC). Furthermore, based on this, an achievable rate region of an RBC with NNC relaying when dirty-paper coding (DPC) is applied at the BS is derived. Numerical results show that the NOMA equipped with the proposed combined coding scheme comprised of DPC and NNC relaying yields significant gain over the originally proposed NOMA.

On the utility of MIMO multi-relay networks for modulation identification over spatially-correlated channels

The necessity to perfectly monitor the intercepted signals for spatially-correlated multiple-input multiple-output (MIMO) systems, involves modulation identification algorithms. In this paper, we present an algorithm dedicated to the modulation identification for correlated MIMO relaying broadcast channels with direct link using multi-relay nodes. By modeling spatially-correlated MIMO channels as Kronecker-structured and the imperfect channel state information of both the source-to-destination and the relay-to-destination errors as independent complex Gaussian random variables, we firstly derive the ergodic capacity of the proposed transmission system. It turns out that the ergodic capacities improve with the number of relay nodes. Based on a pattern recognition approach using the higher order statistics features and the Bagging classifier, we show that the probability to distinguish among M-ary shift keying linear modulation types without any priori modulation information is enhanced compared to the decision tree (J48), the tree augmented naive Bayes, the naive Bayes using discretization and the multilayer perceptron classifiers. We also study the effect of increasing the number of relay nodes. Numerical simulations show that the proposed algorithm using the cooperation of multi-relay nodes with the source node can avoid the performance deterioration in modulation identification caused by both spatial correlation and imperfect CSI.

On the Gaussian Fading Broadcast Relay Channel With Causal State Feedback

We investigate a typical setup of a heterogeneous network that can be modeled as a fast Rayleigh fading broadcast relay channel with one source (macrocell Base Station), one full-duplex relay (smallcell BS), and two destinations (mobile users). It is assumed that instantaneous channel state information (CSI) is available at the receivers’ side, while only a noiseless causal state feedback from the destinations about the source-to-destination channels is available at the relay. We propose a relaying scheme based on a two-stage decode-compress-forward strategy. The essential idea is to let the relay decode the source messages and then forward to the destinations a function of both the decoded messages and the CSI feedback. By characterizing and evaluating the achievable rate region of the proposed relaying scheme, we reveal that non-negligible performance gains over conventional cooperative strategies can be obtained by exploiting CSI feedback at the relay.

Relay Broadcast Channel With Confidential Messages

In this paper, we investigate the effects of a trusted relay node on the secrecy of the broadcast channel by considering the model of relay broadcast channel with confidential messages (RBC-CM). Inner and outer bounds on the capacity-equivocation region of the RBC-CM are provided, and the capacity results are further explained via a degraded Gaussian example, which we call the degraded Gaussian relay broadcast channel with one common and one confidential messages. Numerical results show that this trusted relay node helps to enhance the security of the Gaussian broadcast channel with one common and one confidential messages.

Robust MMSE Beamforming for Multiantenna Relay Networks

In this paper, we propose a robust minimum mean square error (MMSE)-based beamforming technique for multiantenna relay broadcast channels, where a multiantenna base station transmits signal to single antenna users with the help of a multiantenna relay. The signal transmission from the base station to the single antenna users is completed in two time slots, where the relay receives the signal from the base station in the first time slot, and it then forwards the received signal to different users based on amplify and forward (AF) protocol. We propose a robust beamforming technique for a sum-power minimization problem with an imperfect channel state information (CSI) between the relay and the users. This robust scheme is developed based on the worst-case optimization framework and the Nemirovski Lemma by incorporating uncertainties in the CSI. The original optimization problem is divided into three subproblems due to joint nonconvexity in terms of beamforming vectors at the base station, the relay amplification matrix, and receiver coefficients. These subproblems are formulated into a convex optimization framework by exploiting the Nemirovski Lemma, and an iterative algorithm is developed by alternatively optimizing each of them with channel uncertainties. In addition, we provide an optimization framework to evaluate the achievable worst-case mean square error (MSE) of each user for a given set of design parameters. Simulation results are provided to validate the convergence of the proposed algorithm.

Compress-and-Forward for Relay Broadcast Channels without Common Messages

Abstract This paper is connected with compress-and-forward strategy for two-user relay broadcast channels without common messages, where the relay node has private messages from the source, in addition to aiding traditional communication from the source to the destination. For this channel we derive two achievable rate regions based on the compress-and-forward strategy in cases of discrete memoryless channels and Gaussian channels, respectively. The numerical results for Gaussian relay broadcast channel show that the inner bound based on the compress-and-forward strategy improves when all the messages without peeling off any components are compressed and sent to the receiver. It also verifies that the inner bound based on compress-and-forward strategy is better than that based on decode-and-forward strategy, when the relay node is near to the sink node. Moreover, the rate region of the broadcast channel improves considerably when the collaboration between the two receivers is allowed. So the relay node can provide residual resources to help the communication between the source and the sink after its communication rate is satisfied, which gives some insights to select an available relay node in a practical communication system.

Transmission strategies and resource allocation for fading broadcast relay channels

In this paper the broadcast relay channel, where the source communicates with multiple destinations with the help of a single relay is studied. Five different transmission protocols, direct transmission, multihop (MH), multihop with link combination (MHLC), path selection (PS) and path selection with link combination (PSLC) are investigated. In MH and MHLC, the relay decodes the source message and assists both destinations. In PS and PSLC, the relay can perform partial decoding and has the option to help only one of the destinations. Under long-term power constraint, power allocation for delay-limited transmission is performed to minimize common outage probability and individual outage probability region. For comparison, lower bounds on both common and individual outage probabilities are found. Numerical results suggest that path selection significantly lowers outage probabilities, while enforcing the relay to help both destinations simultaneously is limiting the system performance.

Joint Beamforming and Power Allocation for MIMO Relay Broadcast Channel With Individual SINR Constraints

In this paper, system design for the multi-input multi-output (MIMO) relay broadcast channel with individual signal-to-interference-plus-noise ratio (SINR) constraints at the mobile stations (MS) is considered. By exploring the structure of downlink (DL) uplink (UL) duality at either the base station (BS) or the relay station (RS), we propose two schemes of joint power allocation and beamforming design at the BS and the RS. The problem of existence of feasible solutions under practical power constraints at the BS and the RS with given SINR targets is considered first. Then the problem of sum power minimization is considered. Each design problem can be solved efficiently using optimal joint power allocation and beamforming under the framework of convex optimization. We also show that with subchannel pairing at the RS, the transmission power can be reduced by channel compensation at either hop. Finally, an extension to more general multi-hop applications is provided to further improve the power efficiency.

Modulation Recognition for MIMO Relaying Broadcast Channels with Direct Link

In this letter, we investigate the performance of modulation identification based on pattern recognition approach using the decision tree (J48) classifier, for multiple-input multiple-output (MIMO) relaying broadcast channels with direct link (source-to-destination). The proposed system identifies the modulation type and order among different M-ary shift-keying linear modulations used by broadband technologies such as long term evolution-advanced (LTE-A) and worldwide interoperability for microwave access (WiMAX). The system under study employs features extraction based on higher order statistics (HOS) of the received signal. Based on receiver operating characteristic (ROC) curves, our study shows that J48 classifier is more efficient than the multilayer perceptron (MLP) classifier trained with resilient backpropagation training algorithm (RPROP) where it achieves close to perfect detection rate (over 99%) with reasonable training time in acceptable signal-to-noise ratio (SNR) range. We also show that the performance of the MIMO relaying broadcast network is remarkably better than the traditional MIMO one.

Survey on cooperative strategies for wireless relay channels

ABSTRACTCooperative communication has the potential of providing better throughput and reliability to wireless systems when compared with direct communication. To realise the potential gain, it is important to design cooperative strategies for some representative scenarios. This survey deals with three basic wireless relay channels, namely, the parallel relay channel, the multiple‐access relay channel and the broadcast relay channel. For the first channel, which models a single unicast connection, various forwarding strategies are studied. For the second and third channels, which model, respectively, the uplink and downlink scenarios with multiple unicast connections; network codes that exploit the possibility of coding among the connections are studied. The common aim pertaining to the studies of all these three channels is to use the limited radio resource in the most efficient way. Beside the aforementioned conventional works, studies that have state‐of‐the‐art assumptions for relay networks, including outdated channel state information at the transmitter, full duplex relay and practical rateless‐coded cooperation, are also extensively reviewed. Copyright © 2014 John Wiley & Sons, Ltd.

Optimal Power Allocation for MIMO Fully Cooperative Relay Broadcast Channels

We investigate a multiple input multiple output (MIMO) relay broadcast channel (RBC) with fully cooperation between users. A beamforming and combining design is proposed based on singular value decomposition (SVD) of the channel matrix between users. Then, users can simultaneously relay each other's information on the same frequency band with zero interference from each antenna's transmit signal on its received signal. Also, two optimal closed-form solutions are derived for power allocation (PA) under both total power and individual power constraints.

MMSE-Based Beamforming Techniques for Relay Broadcast Channels

We propose minimum mean square error (MMSE)-based beamforming techniques for a multiantenna relay network, where a base station (BS) equipped with multiple antennas communicates with a number of single-antenna users through a multiantenna relay. We specifically solve three optimization problems, namely, 1) the sum-power minimization problem, 2) the mean-square-error (MSE) balancing problem, and 3) the mixed quality-of-service (QoS) problem. Unfortunately, these problems are not jointly convex in terms of beamforming vectors at the BS and the relay amplification matrix. To circumvent this nonconvexity issue, the original problems are divided into two subproblems, where the beamforming vectors and the relay amplification matrix are alternately optimized, whereas the other is fixed. Three iterative algorithms are developed based on convex optimization techniques and general MSE duality. Simulation results are provided to validate the convergence of the proposed algorithms.