scholarly journals Asymptotic Capacity of Large Fading Relay Networks with Random Node Failures

2011 ◽  
Vol 59 (8) ◽  
pp. 2306-2315 ◽  
Author(s):  
Chuan Huang ◽  
Jinhua Jiang ◽  
Shuguang Cui
Keyword(s):  
Large Scale ◽  
Signal To Noise Ratio ◽  
Relay Node ◽  
Relay Network ◽  
Amplify And Forward ◽  
Decode And Forward ◽  
Attack Model ◽  
Random Node ◽  
Rate Loss ◽  
Node Failures

To understand the network response to large-scale physical attacks, we investigate the asymptotic capacity of a half-duplex fading relay network with random node failures when the number of relays N gets infinitely large. In this paper, a simplified independent attack model is assumed where each relay node fails with a certain probability. The noncoherent relaying scheme is considered, which corresponds to the case of zero forward-link channel state information (CSI) at the relays. Accordingly, the whole relay network can be shown equivalent to a Rayleigh fading channel, where we derive the ε-outage capacity upper bound according to the multiple access (MAC) cut-set, and the ε-outage achievable rates for both the amplify-and-forward (AF) and decode-and-forward (DF) strategies. Furthermore, we show that the DF strategy is asymptotically optimal as the outage probability ε goes to zero, with the AF strategy strictly suboptimal over all signal to noise ratio (SNR) regimes. Regarding the rate loss due to random attacks, the AF strategy suffers a less portion of rate loss than the DF strategy in the high SNR regime, while the DF strategy demonstrates more robust performance in the low SNR regime.

scholarly journals A Comparative Study on the Performance of LLR- and SNR-Based Hybrid Relaying Schemes

2017 ◽  
Vol 2017 ◽  
pp. 1-7 ◽  
Author(s):  
Ahmed El-Mahdy ◽  
Wassim Alexan
Keyword(s):  
Comparative Study ◽  
Signal To Noise Ratio ◽  
Relay Node ◽  
Amplify And Forward ◽  
Decode And Forward ◽  
Probability Of Error ◽  
Hybrid Schemes ◽  
Relay Location ◽  
The Impact ◽  
Hybrid Relaying

A comparative study on the theoretical bit error rate (BER) is presented for hybrid relaying schemes that toggle between adaptive decode-and-forward (ADF) and amplify-and-forward (AF) protocols, for a typical three-node wireless network. Toggling between the two forwarding protocols is based on the log-likelihood ratio (LLR) or the signal-to-noise ratio (SNR) of the received signal at the relay node. Closed-form expressions for the probability of error are presented, as well as the expressions of the proposed schemes’ gains over classical ADF and AF protocols. Comparisons are carried out among the two schemes and other hybrid schemes found in the literature. Moreover, the impact of relay location on the probability of error is investigated.

On Performance of Combining Methods for Three-Node Relay Network

2012 ◽  
Vol 263-266 ◽  
pp. 1160-1164
Author(s):  
Wen Yuan Rao
Keyword(s):  
Relay Network ◽  
Estimation Accuracy ◽  
Diversity Order ◽  
Amplify And Forward ◽  
Decode And Forward ◽  
Channel Quality ◽  
Combining Methods ◽  
Better Than

We study the performance of the three-node relay network. Three combining methods for the Amplify-and-Forward (AF) protocol and the Decode-and-Forward (DF) protocol are compared. Simulations indicate that the AF protocol is better than DF under all these three combining methods. To combine the incoming signals the channel quality should be estimated as accuracy as possible, more estimation accuracy requires more resource. A very simple combining method can obtain the performance comparative with optimal combining methods approximately. At the same time, all three combining methods for both diversity protocols can achieve the maximum diversity order.

scholarly journals Evaluation of PLC Channel Capacity and ABER Performances for OFDM-Based Two-Hop Relaying Transmission

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Sana Ezzine ◽  
Fatma Abdelkefi ◽  
Jean Pierre Cances ◽  
Vahid Meghdadi ◽  
Ammar Bouallégue
Keyword(s):  
Channel Capacity ◽  
Orthogonal Frequency Division Multiplexing ◽  
Low Cost ◽  
Relay Node ◽  
Destination Node ◽  
Direct Link ◽  
Amplify And Forward ◽  
Decode And Forward ◽  
Maximum Ratio Combining ◽  
The Impact

Powerline network is recognized as a favorable infrastructure for Smart Grid to transmit information in the network thanks to its broad coverage and low cost deployment. The existing works are trying to improve and adapt transmission techniques to reduce Powerline Communication (PLC) channel attenuation and exploit the limited bandwidth to support high data rate over long distances. Two-hop relaying BroadBand PLC (BB-PLC) system, in which Orthogonal Frequency Division Multiplexing (OFDM) is used, is considered in this paper. We derive and compare the PLC channel capacity and the end-to-end Average BER (ABER) for OFDM-based direct link (DL) BB-PLC system and for OFDM-based two-hop relaying BB-PLC system for Amplify and Forward (AF) and Decode and Forward (DF) protocols. We analyze the improvements when we consider the direct link in a cooperative communication when the relay node only transmits the correctly decoded signal. Maximum ratio combining is employed at the destination node to detect the transmitted signal. In addition, in this paper, we highlight the impact of the relay location on the channel capacity and ABER for AF and DF transmission protocols. Moreover, an efficient use of the direct link was also investigated in this paper.

scholarly journals Outage Performance of Bidirectional Full-Duplex Amplify-and-Forward Relay Network with Transmit Antenna Selection and Maximal Ratio Combining

2018 ◽  
Vol 1 ◽  
pp. 62-69
Author(s):  
R. Rajesh ◽  
P. G. S. Velmurugan ◽  
S. J. Thiruvengadam ◽  
P. S. Mallick
Keyword(s):  
Antenna Selection ◽  
Relay Node ◽  
Maximal Ratio Combining ◽  
Full Duplex ◽  
Relay Network ◽  
Amplify And Forward ◽  
Transmit Antenna Selection ◽  
Outage Performance ◽  
Half Duplex ◽  
Af Relay

In this paper, a bidirectional full-duplex amplify- and-forward (AF) relay network with multiple antennas at source nodes is proposed. Assuming that the channel state information is known at the source nodes, transmit antenna selection and maximal ratio combining (MRC) are employed when source nodes transmit information to the relay node and receive information from the relay node respectively, in order to improve the overall signal-to-interference plus noise ratio (SINR). Analytical expressions are derived for tight upper bound SINR at the relay node and source nodes upon reception. Further, losed form expressions are also derived for end-to-end outage probability of the proposed bidirectional full-duplex AF relay network in the Nakagami-m fading channel environment. Although self-interference at the relay node limits the performance of the full-duplex network, the outage performance of the proposed network is better than that of conventional bidirectional full-duplex and half-duplex AF relay networks, due to the selection diversity gain in TAS and diversity and array gain in MRC.

scholarly journals Performance Analysis of Full-Duplex Amplify-and-Forward Relay System with Hardware Impairments and Imperfect Self-Interference Cancellation

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Ba Cao Nguyen ◽  
Xuan Nam Tran
Keyword(s):  
Interference Cancellation ◽  
Signal To Noise Ratio ◽  
Relay Node ◽  
Analytical Framework ◽  
Full Duplex ◽  
High Signal ◽  
Amplify And Forward ◽  
Relay System ◽  
Hardware Impairments ◽  
The Impact

In this paper, we analyze the performance of a full-duplex (FD) amplify-and-forward (AF) relay system with imperfect hardware. Besides the aggregate hardware impairments of the imperfect transceiver, we also consider the impact of residual self-interference (RSI) due to imperfect cancellation at the FD relay node. An analytical framework for analyzing the system performance including exact outage probability (OP), asymptotic OP, and approximate symbol error probability (SEP) is developed. In order to tackle these impacts, we propose an optimal power allocation scheme which can improve the outage performance of the FD relay node, especially at the high signal-to-noise ratio (SNR) regime. Numerical results are presented for various evaluation scenarios and verified using the Monte Carlo simulations.

scholarly journals Bandwidth Allocation of Cognitive Relay Networks with Energy Harvesting for Smart Grid

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Yupeng Li ◽  
Zihao Wang ◽  
Ling Luo ◽  
Zhiyong Chen ◽  
Bin Xia ◽  
...  
Keyword(s):  
Energy Harvesting ◽  
Smart Grid ◽  
Bandwidth Allocation ◽  
Relay Node ◽  
Amplify And Forward ◽  
Decode And Forward ◽  
Secondary Users ◽  
Optimal Bandwidth Allocation ◽  
Outage Probabilities ◽  
Primary Transmission

In this paper, we investigate an energy harvesting scheme in a smart grid based on the cognitive relay protocol, where a primary transmitter scavenges energy from the nature sources and then employs the harvested energy to forward the primary signal. Depending on the intensity of the energy harvesting from nature, a secondary user dynamically acts as a relay node to assist the primary transmission or does not. When the energy is not enough powerful to support the direct transmission between two primary users, the secondary users share the spectrum by assisting the primary transmission. For the relaying scheme, both amplify-and-forward (AF) and decode-and-forward (DF) protocols are investigated. We analytically obtain the exact transmission rates for both primary and secondary networks and derive the exact expressions of the system outage probabilities for both primary and secondary users in the smart grid. Moreover, we develop the analytically optimal bandwidth allocation strategy to maximize the total sum rate of the proposed scheme. Numerical results are presented to demonstrate the performance gain of the proposed scheme over the nonoptimal scheme.

scholarly journals Individual Channel Estimation in a Diamond Relay Network Using Relay-Assisted Training

2017 ◽  
Vol 2017 ◽  
pp. 1-8
Author(s):  
Xianwen He ◽  
Gaoqi Dou ◽  
Jun Gao
Keyword(s):  
Channel Estimation ◽  
Relay Node ◽  
Spatial Diversity ◽  
Relay Network ◽  
Destination Node ◽  
Training Design ◽  
Amplify And Forward ◽  
Relay Nodes ◽  
Training Scheme ◽  
Data Signal

We consider the training design and channel estimation in the amplify-and-forward (AF) diamond relay network. Our strategy is to transmit the source training in time-multiplexing (TM) mode while each relay node superimposes its own relay training over the amplified received data signal without bandwidth expansion. The principal challenge is to obtain accurate channel state information (CSI) of second-hop link due to the multiaccess interference (MAI) and cooperative data interference (CDI). To maintain the orthogonality between data and training, a modified relay-assisted training scheme is proposed to migrate the CDI, where some of the cooperative data at the relay are discarded to accommodate relay training. Meanwhile, a couple of optimal zero-correlation zone (ZCZ) relay-assisted sequences are designed to avoid MAI. At the destination node, the received signals from the two relay nodes are combined to achieve spatial diversity and enhanced data reliability. The simulation results are presented to validate the performance of the proposed schemes.

scholarly journals Hybrid AF/DF Cooperative Relaying Technique with Phase Steering for Industrial IoT Networks

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 937
Author(s):  
Sangku Lee ◽  
Janghyuk Youn ◽  
Bang Chul Jung
Keyword(s):  
Spectrum Sharing ◽  
Low Cost ◽  
Relay Node ◽  
Access Point ◽  
Radio Spectrum ◽  
Cooperative Relaying ◽  
Amplify And Forward ◽  
Relay Nodes ◽  
Decode And Forward ◽  
Industrial Iot

For the next generation of manufacturing, the industrial internet of things (IoT) has been considered as a key technology that enables smart factories, in which sensors transfer measured data, actuators are controlled, and systems are connected wirelessly. In particular, the wireless sensor network (WSN) needs to operate with low cost, low power (energy), and narrow spectrum, which are the most technical challenges for industrial IoT networks. In general, a relay-assisted communication network has been known to overcome scarce energy problems, and a spectrum-sharing technique has been considered as a promising technique for the radio spectrum shortage problem. In this paper, we propose a phase steering based hybrid cooperative relaying (PSHCR) technique for the generic relay-assisted spectrum-shared WSN, which consists of a secondary transmitter, multiple secondary relays (SRs), a secondary access point, and multiple primary access points. Basically, SRs in the proposed PSHCR technique operate with decode-and-forward (DF) relaying protocol, but it does not abandon the SRs that failed in decoding at the first hop. Instead, the SRs operate with amplify-and-forward (AF) protocol when they failed in decoding at the first hop. Furthermore, the SRs (regardless of operating with AF or DF protocol) that satisfy interference constraints to the primary network are allowed to transmit a signal to the secondary access point at the second hop. Note that phase distortion is compensated through phase steering operation at each relay node before second-hop transmission, and thus all relay nodes can operate in a fully distributed manner. Finally, we validate that the proposed PSHCR technique significantly outperforms the existing best single relay selection (BSR) technique and cooperative phase steering (CPS) technique in terms of outage performance via extensive computer simulations.

scholarly journals The Optimal Power Allocation with Hybrid Relaying Based on Channel Condition

2018 ◽  
Author(s):  
Junpyo Jeon ◽  
Yeonggyu Shim ◽  
Hyuncheol Park
Keyword(s):  
Power Allocation ◽  
Relay Network ◽  
Achievable Rate ◽  
Optimal Power Allocation ◽  
Allocation Scheme ◽  
Amplify And Forward ◽  
Decode And Forward ◽  
Transmit Power ◽  
Optimal Power ◽  
Af Relay

This paper considers a hybrid relay network consisting of the source, the amplify-and-forward (AF) relay, the decode-and-forward (DF) relay, and the destination. We propose the optimal power allocation schemes between two different relays which maximize the achievable rate under a sum relay power constraint for given channel gains and transmit power from source. By solving the optimization problem to maximize the achievable rate for each relay network, the transmit power values in closed-form are derived. When the channel gains are the same, the optimal power allocation scheme for AF-DF relay network proves that a more power should be allocated at the first relay to maximize the achievable rate. In case of the DF-AF relay network, we derive the optimal power allocation scheme for the possible four cases. Under the same SNR condition at the first hop, we show that the achievable rate of AF-DF relay network is greater than that of DF-AF relay network when the channel gain between two relays is higher than that between the second relay and destination. Simulation results show that the proposed power allocation schemes provide a higher achievable rate than the equal power allocation schemes.

scholarly journals PERFORMANCE EVALUATION OF RELAYING SCHEMES FOR WIRELESS COMMUNICATION SYSTEMS

2013 ◽  
pp. 157-161
Author(s):  
MANISHA CRASTO BRAGANC ◽  
HASANALI G. VIRANI ◽  
SHAILESH KHANOLKAR
Keyword(s):  
Communication Systems ◽  
Signal To Noise Ratio ◽  
Additive White Gaussian Noise ◽  
Multiple Input Multiple Output ◽  
Amplify And Forward ◽  
Decode And Forward ◽  
Wireless System ◽  
Single Input Single Output ◽  
Single Output ◽  
Alamouti Coding

The evaluation of MIMO (multiple-input multiple-output) Relay wireless system is carried out and compared against the performance of a SISO (single-input single-output) Relay wireless system. The encoding scheme used in MIMO is Alamouti coding and decoding is done by the Maximum Likelihood (ML) detector. A comparison is made between the SISO non-regenerative amplify-and-forward (AF) and regenerative decode-and-forward (DF) relaying schemes. The plots of bit error rate (BER) versus signal to noise ratio (SNR) are simulated by incorporating Rayleigh fading condition in the presence of additive white Gaussian noise(AWGN) using MATLAB.

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