DF Protocol Research Articles

Secrecy Performance Analysis of Cooperative NOMA with AF and DF Protocol over Rayleigh Channel

Secrecy Performance Analysis of Cooperative NOMA with AF and DF Protocol over Rayleigh Channel

An Empirical Comparison of Encoding Algorithms of the Low Density Parity Check Code for Decode and Forward Protocol Relay System

Decode and a forward (DF) protocol relay technique in cooperative communication is becoming a more attractive method to achieve a higher throughput requirement for wireless communication these days. But the high complexity operation is a major issue in the DF protocol relay processing system. The encoding operation which is a pre-processing stage of the decoding process consumes high complexity in the DF protocol relay system. Thus, it is important to tackle the encoding operation to ensure low complexity and good performance of the subsequent decoding operation in the DF protocol relay system. Thus far, very limited works have been reported on identifying a suitable encoding algorithm of encoding operation for the DF protocol relay system using the Low Density Parity Check (LDPC) code. In this paper, we present a suitable encoding algorithm for the DF protocol relay system using the LDPC code. To find out the most suitable encoding algorithm for the DF protocol relay system using LDPC code, we introduce the LDPC code encoding model. Eight different encoding algorithms based on Lower Upper and Orthogonal Upper algorithms presented in the LDPC code encoding model. The encoding execution time, the number of nonzero, and the pattern of nonzero was used to evaluate the computational complexity performance of the designed LDPC code encoding model. The most suitable encoding algorithm for the required criteria of the DF protocol relay system using the LDPC code is identified.

Performance Analysis of Cooperative and Non-Cooperative Relaying over VLC Channels.

The line-of-sight (LoS) channel is one of the requirements for efficient data transmission in visible-light communications (VLC), but this cannot always be guaranteed in indoor applications for a variety of reasons, such as moving objects and the layout of rooms. The relay-assisted VLC system is one of the techniques that can be used to address this issue and ensures seamless connectivity. This paper investigates the performance of half-duplex (HD) conventional DF relay system and cooperative systems (i.e., selective DF (SDF) and incremental DF (IDF)) over VLC channels in terms of outage probability and energy consumption. Analytical expressions for both outage probability and the minimum energy-per-bit performance of the aforementioned relaying systems are derived. Furthermore, Monte Carlo simulations are provided throughout the paper to validate the derived expressions. The results show that exploiting SDF and IDF relaying schemes can achieve approximately 25% and 15% outage probability enhancement compared to single-hop and DF protocols, respectively. The results also demonstrate that the performance of the single-hop VLC system deteriorates when the end-to-end distances become larger. For example, when the vertical distance is 3.5m, the single-hop approach consumes 20%, 40% and 45% more energy in comparison to the DF, SDF, and IDF approaches, respectively.

Optimal Cooperative Strategies for PHY Security Maximization Subject to SNR Constraints

The cooperative jamming (CJ) and decode–and–forward (DF) protocols for physical layer security are studied in this paper. We propose a design that aims at maximizing the security gap, which is defined as the signal–to–noise ratio (SNR) difference between the destination and an eavesdropper, subject to security and reliability constraints defining the thresholds on the received signals’ SNR values at the destination and the eavesdropper. A fractional quadratically constrained quadratic program (QCQP) is formulated, which is solved analytically and closed–form expressions are determined for both protocols. Numerical results demonstrate that the proposed designs achieve the same performance for the secrecy rate under both strategies compared with state–of–the–art approaches, for a proper choice of thresholds on SNR values. Additionally, for relaxed thresholds and at the cost of a slight decrease on the optimal secrecy rate value, the received SNR values at the eavesdropper are greatly decreased for the CJ protocol and even more for the DF protocol, while guaranteeing target SNR values at the destination, compared with previous state–of–the–art approaches.

Comparative throughput study of energy harvesting CR network with adaptive hybrid relay

In this paper, we have analyzed the throughput performance of spectrum sharing cognitive relay network incorporated with energy harvesting source and relay in presence of non-identical Rayleigh fading channel. In our model, multiple primary users are considered and their interference signal is used by source and relays to harvest energy. The relays follow Adaptive Hybrid (AHR) Protocol to forward source signal to destination. We use time switching relaying scheme to harvest secondary source as well as secondary relay. Throughput performance of the network is compared considering (a) delay-sensitive and (b) delay-tolerant transmission modes. It is observed that AHR protocol outperforms AF and DF protocols in both transmission modes. The effect of increasing the primary network operating power on system throughput is shown as a function of $$\alpha$$ . The impact of number of relays and number of primary users on secondary throughput performance is also studied. A comparison for various combinations of number of relays and number of primary users is also shown.

Effect of energy allocation in dual‐hop communication systems with DF protocol

Relay communication has been receiving considerable attention for its advantage of extension in communication coverage and enhancement of communication performance. In this Letter, the author studied the performance of dual-hop communication systems with a decode-and-forward protocol. The author first analyses the performance of dual-hop communication systems with various modulation schemes. Then, the author found the optimum energy allocation depending on the relay location for each modulation scheme. Finally, the performance of dual-hop communication systems with equal energy allocation and optimum energy allocation was compared.

Full-Duplex User Relaying for NOMA System With Self-Energy Recycling

This paper proposes a self-energy recycling full-duplex cooperative non-orthogonal multiple access (SRF-NOMA) system, where a nearby user can be employed as a decode-and-forward, amplify-and-forward, and quantize-map-forward relay with self-energy recycling protocol to assist a distant user. The relay harvests energy from dedicated energy signal sent by a base station, while it reuses energy from loop self-interference (LI) signal. To characterize the performance of the system proposed, new expressions of exact and asymptotic outage probabilities for two users are derived. Based on analytical results, the diversity orders achieved by the nearby and distant user are one and two, respectively. We confirm that the diversity orders of the distant user are obtained with direct link and relaying link, since the energy from LI is harvested for information transmission at the relay. Numerical results are presented to validate the accuracy of the derived results and demonstrate that: 1) when the DF or AF protocol is employed, the outage behavior of the SRF-NOMA system is superior to orthogonal multiple access; 2) in the high signal-to-noise ratio region, DF relay in the SRF-NOMA system is capable of enhancing the outage performance compared to AF relay; and 3) the distant user in the SRF-NOMA system with QMF relay is able to obtain a better performance than that of DF and AF relays.

Power Allocation in Two-Way Relay Networks with MABC DF Protocol and No Instantaneous Channel State Information

In this paper we examine a two way relay network with multiple access broadcast, decode and forward protocol. A new power allocation scheme is proposed which is based on minimizing the outage probability. The outage probability is defined as the event in which the data rate of the different nodes lie outside the achievable rate region. For the first time, a closed-form mathematical expression is derived for the outage probability of such system, in the more general case than previous attempts. The only limiting constraint that is enforced on the problem is that the relay power is less than the power of the end main nodes (terminals). The obtained expression is then considered as the cost function of an optimization problem, in order to be minimized by allocating appropriate power to the nodes. The proposed scheme for power allocation needs no instantaneous channel coefficient estimation, but rather needs only statistical Channel State Information. The correctness of the obtained expression for the outage probability is verified by Monte Carlo simulations and the performance of the proposed scheme for power allocation is analyzed numerically. We have demonstrated that this technique can provide up to 1 dB gain in outage probability for average SNR values.

Optimizing Energy in Relay Transmission Schemes in LTE-A Networks

Background/Objectives: In order to achieve high reliability and throughput, cooperative communication is being used in wireless networks. This technology is an efficient approach in reducing the energy consumption. Methods/Statistical Analysis: In this sense, the Decode andForward Relay protocol is analyzed where the Physical Network Coding (PNC) with Slepian-Wolf is incorporated in the Decode and Forward Relaying (DF) protocol. The PNC with Slepian-Wolf usage reduces the energy consumption in relay communication due to the compression and reduced time slots, when compared to the traditional relay transmission schemes and also increases the coverage of the cell. Findings: The spectral efficiency is varied, PNC with Slepian-Wolf assures higher energy efficiency than the traditional scheme when the spectral efficiency is higher and when the spectral efficiency is lower, both the schemes consumes nearly the same energy. Again when the downlink rate is higher than the uplink rate, that is, in case of asymmetric traffic conditions, both traditional scheme using DF protocol and the proposed PNC with DF protocol have similar relay deployment and PNC with Slepian-Wolf shows lower energy consumption. Conclusion/Improvements: Thus, the proposed scheme shows good performance when the spectral efficiency is higher and the downlink rate is higher than the downlink rate.

Cooperative Communication Using the DF Protocol in the Hierarchical Modulation

Cooperative Communication Using the DF Protocol in the Hierarchical Modulation

Distributed space‐time coding with decode‐and‐forward–amplify‐and‐forward selection relaying protocol in cooperative wireless sensor networks

Distributed space-time coding (DSTC) with an efficient relaying protocol, referred to as amplify-and-forward and decode-and-forward (DF-AF) selection relaying, has not received much attention yet. In the DF-AF selection relaying-aided DSTC transmissions, each relay could adaptively process the received signal according to its decoding state to improve the performance. In this study, the authors analyse the pairwise error probability (PEP) performance, the diversity order and the union bound on the error probability of the DSTC with DF-AF selection relaying in cooperative wireless sensor networks. More specifically, by introducing a random variable vector to denote the decoding state of the relays, the upper bounds of PEP are derived first for the DSTC with DF-AF selection relaying based on the Chernoff bound. Then, the diversity order and the union bound on the error probability are obtained based on the upper bounds of PEP. Finally, simulation results verify the theoretical analysis and demonstrate that the DSTC with DF-AF selection relaying has better error performance than the DSTC with DF protocol and the DSTC based on AF protocol.

Distributed space-time coded non-orthogonal DF protocols with source antenna switching

In this paper, a new distributed space-time coded (DS-TCed) non-orthogonal decode-and-forward (NDF) protocol with source antenna switching (SAS) is proposed, where two antennas associated with each radio frequency chain can be alternatively used in the first and second phases. Several DSTC schemes for the NDF with SAS (NDF-SAS) protocol are proposed and their average pairwise error probability for the error-free source-relay (SR) channel is also derived. The simulation results show that the NDF-SAS protocol achieves larger diversity order than the NDF protocol under the error-free and erroneous SR channels.

Approximate SEP Analysis for DF Cooperative Networks With Opportunistic Relaying

We analyze the symbol error probability (SEP) performance of cooperative diversity networks with opportunistic decode-and-forward (ODF) relaying. Assuming that channels suffer from independent nonidentical Rayleigh fading and symbols are M-PSK modulated, the approximate closed-form SEP expressions are derived for opportunistic relaying with adaptive and fixed DF protocols, respectively. Simulations are carried out to validate the theoretical analysis. Results show that the derived approximate SEP is tight particularly at medium and high SNR.

On the DMT-Optimality of Nondynamic DF Relaying in Asymmetric Nakagami Fading Channels

The optimality of nondynamic DF relaying over a general three-node Nakagami fading channel in terms of the diversity-multiplexing tradeoff (DMT) is established. In particular, when the fading of the relay-source link is less severe than that of the relay-destination link, both orthogonal and nonorthogonal DF protocols are shown to be DMT-optimal over certain ranges of the multiplexing gains. It is also shown that when the multiplexing gains are sufficiently high, the DMT of the DF protocols is completely independent of the statistical properties of the relay-destination link.

DF protocd plus radiotherapy in treatment of patients with advanced nasopharyngeal carcinoma

Objective This study is to evaluate the effect of chemotherapy combined with radiotherapy for the treatment of the patients with advanced nasopharyngeal carcinoma(NPC).Methods Fom march 1994 to October 1997,64 patients with stage Ⅲ, Ⅳa NPC ('92 stage system)at random received one course of chemotherapy of DF protocol (5\|FU and cisplatin) before radiotherapy (which started 3 days after the firstcycle of chemotherapy) and two to three cycles ofpost\|radiotherapy chemotherapy or radiotherapy alone (including 28 patients).Results The 5\|year survival rate was 61.1% in thechemotherapy/radiotherapy as compared with 35.7% in the radiotherapy group( P 0.05). The primary tumor controlratesat 5\|year were 66.7% and 39.3%.The distant metastatic rate at 5\|year was 25%(chemotherapy/radiotherapy)to 50%(radiotherapy group).Conclusion Radiotherapy combined with chemotherapycan improve the survival and local disease control,and may delay the distant metastasis in the patients with advanced NPC.