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The design of a cooperative protocol relying on both cooperative relaying and jamming in order to provide security at the physical layer of wireless communications is considered in this paper. We suppose that pair of nodes is assisted by a number of helpers in their communication, which either relay information or cause harmful interference to an eavesdropper, at both stages of the relaying protocol...
In this paper, we investigate the outage performance of a traffic-aware two-way relay system with active direct link by employing three-phase (3P) analog network coding (ANC) under Nakagami-m fading. We derive a tight expression for overall outage probability (OOP) that jointly takes into account the asymmetric traffic requirements at the two end users. We also derive an asymptotic outage behavior...
In this paper, we present a novel guard-band (GB)-aware channel assignment mechanism that attempts at maximization the achieved network throughput by improving spectrum utilization. Unlike most of previously proposed GB-aware channel assignment algorithms that perform the assignment sequentially, the proposed mechanism performs the channel and power assignment for multiple cognitive radio (CR) transmissions...
In this paper, the optimal power allocation (OPA) problem for Chase combining (CC)-based cooperative hybrid automatic repeat request (HARQ) protocol over block Rayleigh fading channels is addressed. With the constraints of the targeted outage probability and the maximum number of transmission rounds, we aim at determining the optimal power sequences of the source and the relay to minimize the average...
Most previous researches on the rate analysis of the power allocation (PA) schemes in two-way decode-and- forward (DF) relay systems typically focus on maximizing the instantaneous objective rates. However, the ergodic rate analysis of the optimized rates is not well considered. In this paper, we investigate the ergodic rates of the PA schemes in a two-way DF relay system, where the physical-layer...
Differential amplify-and-forward (DAF) cooperative relaying appears to be an attractive strategy for wireless networks where channel estimation is not feasible or it is rather avoided. In this work, we intend to determine the optimum relay location in order to minimize the outage probability of the DAF cooperative relaying in case that the system is allowed to deploy the relay. We consider two scenarios...
Previous works in spectrum leasing for centralized cognitive radio networks (CRNs) are based on selecting a secondary user as a relay to cooperatively transmit the primary data and then leasing the released spectrum due to the cooperation to the selected user. In this paper, we propose a new spectrum leasing scheme to improve the throughput and thus the spectrum efficiency of the secondary system...
This paper investigates linear precoding designs for a cooperative amplify-and-forward (AF) network with a multi-antenna relay having complete channel state information (CSI). The focus is on both orthogonal AF (OAF) and non-orthogonal AF (NAF) protocols. The precoders at the relay are derived based on the maximum ratio combining (MRC) scheme, followed by an optimal power amplification factor to maximize...
This paper addresses the problem of optimal power allocation among relaying nodes for a non-orthogonal amplify-and-forward (NAF) half-duplex relay network where multiple relays exploit channel state information (CSI) to cooperate with a pair of source and destination to maximize the source-destination mutual information (MI). In particular, assuming that the relays have complete CSI of all source-relay,...
In this paper, we develop a cross-layer design incorporating adaptive modulation coding (AMC) and truncated hybrid automatic repeat request (HARQ). We define different packet error rate (PER) constraints for each (re)transmission, thus adopting dynamic switching thresholds correspondingly to fully exploit the combining gain in HARQ protocols. Analytical expressions for performance metrics are derived,...
In this paper, a spectrum sharing protocol is proposed for device-to-device (D2D) communication overlaying cellular networks. Specifically, the protocol allows the D2D users to communicate bi-directionally with each other while assisting the two-way communication between the cellular base station (BS) and the cellular user (CU) over the same time and frequency resources. The achievable rate region...
In this paper, a full duplex relay using a Dynamic Decode and Forward (DDF) protocol is considered for improving the performance of multiple source-destination pairs interfering one on each other. A relay precoder is optimized as a function of the symbols correctly decoded by the relay in order to improve the channel capacity. Furthermore, a DDF-Patching technique allows for increasing the number...
This paper addresses the medium access control (MAC) and physical (PHY) cross-layer design of a time-division multiple access protocol (TDMA) where users with good channels are allowed to relay the packets of other users with less favorable conditions. All signals are combined at the central node using signal processing tools in order to achieve diversity. The work is focused on an asymmetrical scenario...
In this paper, we investigate a joint resource allocation for a multiuser two-way OFDMA relay network. To reduce the computational complexity, we separate the joint resource allocation into two stages, subcarrier allocation and power allocation, and propose resource allocation schemes. In the proposed schemes, resources are allocated to the user-pairs and relays to maximize the achievable sum-rate...
This article develops a unified mathematical framework for maximization of the user throughput over generalized wireless channels using the symbol rate, packet length and constellation size of two distinct classes of digital modulation schemes (M-PSK and M-QAM) as optimization variables. First, we show that the throughput optimization problem for truncated selective-repeat automatic repeat request...
This paper investigates the achievable rate region of two-way amplify-and-forward (AF) relaying systems with multiple relays, where all nodes are equipped with multiple antennas. First, we find linear processing filters to optimize the weighted sum-rate for the two-way channels with sum power constraints. The proposed algorithm achieves the maximum weighted sum-rate by deriving the gradient expressions...
We analyze the throughput achievable by a truncated Hybrid ARQ protocol (HARQ) using incremental redundancy (IR) when transmitting over a block-fading channel whose state is unknown at the transmit end. We allow the transmission rates to vary, optimize them, and show that such a variable-rate HARQ-IR provides gains with respect to a fixed-rate transmission in terms of increased throughput and decreased...
Owing to its spectral efficiency, bidirectional relaying is a promising candidate for information exchange in multiple-user cooperative networks. When the network is limited by resource constraints, amplify-and-forward (AaF) relay protocol is often the choice due to its simplicity and ease of use. Power allocation for AaF protocol has being extensively studied in unidirectional relay networks but...
Power saving is an important issue in wireless networks. This paper proposed an energy-efficient cooperative relay selection scheme that utilized the transmission power more efficiently in cooperative relaying systems. The nodes in the network were deployed with multiple antennas and the decode-and-forward relaying protocol was used. The optimization problem of energy efficiency in cooperative relaying...
In this paper, we propose an improvement of truncated ARQ protocol throughput through the optimization of the distribution of the average energy cost per packet (or, equivalently, per symbol) among all packet transmission attempts. We consider exclusively BPSK-modulated ARQ transmission over an AWGN channel, with and without packet combining using the selective repeat as a transmission protocol. Our...
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