Decode‐and‐forward with partial relay selection

Exact expressions for outage probability and symbol error rate are presented for a decode‐and‐forward cooperative network with partial relay selection. An independent but not identically distributed Nakagami‐m fading environment is considered. Numerical and simulated results show the validity of the analytical results. Copyright © 2010 John Wiley & Sons, Ltd.     

A comparative study of full‐duplex relaying schemes for low latency applications

Various sectors are likely to carry a set of emerging applications while targeting a reliable communication with low latency transmission. To address this issue, upon a spectrally‐efficient transmission, this paper investigates the performance of a 1 full‐dulpex relay system and considers for that purpose, 2 basic relaying schemes, namely, the symbol‐by‐symbol transmission, i.e., amplify‐and‐forward and the block‐by‐block transmission, i.e., selective decode‐and‐forward. The conducted analysis presents an exhaustive comparison, covering both schemes, over 2 different transmission modes, i.e., the noncombining mode where the best link, direct, or relay link is decoded and the signals combining mode, where direct and relay links are combined at the receiver side. While targeting latency purpose as a necessity, simulations show a refined results of performed comparisons and reveal that amplify‐and‐forward relaying scheme is more adapted to combining mode, whereas the selective decode‐and‐forward relaying scheme is more suitable for noncombining mode.     

Opportunistic Decode‐and‐Forward Cooperation in Mixed Rayleigh and Rician Fading Channels

We consider a two‐hop multiple‐relay network implemented with opportunistic decode‐and‐forward cooperative strategy, where the first hop and second hop links experience different fading (Rayleigh and Rician). We derive the exact expressions of end‐to‐end outage probability and analyze the approximate results in high signal‐to‐noise ratio region. The analysis shows that the same diversity order can be achieved even in different mixed fading environments. Simulation results are provided to verify our analysis.     

Maximum harvested energy policy in full‐duplex relaying networks with SWIPT

It is considered that energy scavenging is a promising way for source node transfer energy to powered constraint relay in cooperative networks with advantage of cost‐effective maintenance and flexible deployment, which so‐called simultaneous wireless information and power transfer. In this paper, relay selection for optimal wireless energy is investigated. In terms of time switching–based relaying, this paper considers the performance comparison of 3 proposed relay selection schemes, namely, (1) optimal relay selection scheme , (2) maximum harvested energy relay selection scheme , and (3) minimum self‐interference relay selection . In particular, the system performance is studied intensively with regard to outage probability and throughput over Rayleigh fading channels. We also achieve the integral form for accurate expressions and closed form for approximate expressions. Finally, these analytical expressions are proved exactness according to Monte Carlo simulation.     

Error performance for relaying protocols with multiple decode‐and‐forward relays

This paper investigates the error performance of three relaying protocols with multiple decode‐and‐forward relays. In the first protocol, relays that can decode correctly will forward the signals from source. Nevertheless, selection cooperation (SC) and opportunistic relaying (OR) are adopted to select only a single relay to forward in the other two protocols, respectively. At sufficiently high signal‐to‐noise ratio, the upper bounds on bit error probability are derived for three protocols, where the developments apply for various channel fading models. Simulation results are provided to verify the tightness of the analytical bounds, and the performance comparisons among different relaying protocols are presented. Copyright © 2010 John Wiley & Sons, Ltd.     

Performance of Selective Decode‐and‐Forward Relay Networks with Partial Channel Information

In this letter, closed‐form approximations for outage probability and symbol error rate are presented for a selective decode‐and‐forward relay network with partial channel information. An independent but not identically distributed Rayleigh fading environment is considered. Numerical and simulated results demonstrate the validity of the analytical results.     

Outage performance of cognitive radio networks with multiple decode‐and‐forward relays

This paper considers the cognitive radio network with one primary user (PU), one secondary user (SU), and multiple decode‐and‐forward relays. We propose a relaying scheme to ensure the priority of primary transmission, where the relays are used to forward PU's message and sometimes also SU's message. First, SU is allowed to use the spectrum to transmit only when its transmission would not affect the decoding status of PU's message at all relays. Second, once the secondary transmission happens, the relays that successively decode SU's message are allowed to retransmit this message when it would not affect the decoding status of PU's message at primary receiver. The interference from PU to SU and the interference from SU to PU are both considered. By analyzing the decoding status of primary message and secondary message at different relays, we formulate the outage probabilities of both primary transmission and secondary transmission. When all channels follow Rayleigh distributions, we derive the analytical expressions for the general case of any number of relays, which are validated by means of Monte Carlo simulations. Copyright © 2016 John Wiley & Sons, Ltd.     

Outage Probability of Decode‐and‐Forward Relaying Systems with Efficient Partial Relay Selection in Nakagami Fading Channels

Recently, efficient partial relay selection (e‐PRS) was proposed as an enhanced version of PRS. In comparing e‐PRS, PRS, and the best relay selection (BRS), there is a tradeoff between complexity and performance; that is, the complexity for PRS, e‐PRS, and BRS is low to high, respectively, but vice versa for performance. In this paper, we study the outage probability for e‐PRS in decode‐and‐forward (DF) relaying systems over non‐identical Nakagami‐m fading channels, where the fading parameter m is an integer. In particular, we provide closed‐form expressions of the exact outage probability and asymptotic outage probability for e‐PRS in DF relaying systems. Numerical results show that e‐PRS achieves similar outage performance to that of BRS for a low or medium signal‐to‐noise ratio, a high fading parameter, a small number of relays, and a large difference between the average channel powers for the first and the second hops.     

Outage probability and error rate analysis of full duplex relay in asymmetric fading channels

Full duplex (FD) technique has evolved as a viable solution to address the spectrum scarce issue. It has gained research interest for its potential to double the wireless link capacity and enhance spectral efficiency (SE). In this paper, the end-to-end performance of an amplify-and-forward full duplex relay(FDR) in asymmetric Rayleigh–Rician fading channels is explored, unlike the other works that assume symmetric fading conditions in both the links. The asymmetric or mixed fading channels properly model the realistic communication scenarios like satellite/terrestrial wireless communication systems. In this work, we consider that the source-relay link experiences Rayleigh fading and the relay-destination link experiences Rician fading. The novel exact and lower bound closed form analytical expressions for outage probability (OP) and bit error rate (BER) for the considered FD system are derived. Moreover, the effect of severity of fading and the amount of residual self-interference (RSI) on the performance of FDR are also studied. In addition, MC simulations are carried out to validate the results. It is observed that the performance metrics, OP and BER, are highly dependent on the severity of fading and the amount of RSI. Furthermore, it is found that typically at the SNR of 10 dB, an improvement of approximately 27.6% in OP is obtained. Also, our work offers appreciable SNR gain, for example, for a BER of 10⁻², an SNR improvement of around 11 dB is achieved. These findings have been compared with the mixed Rayleigh–Rician fading channel conditions considering only half duplex(HD) mode. These parameter metrics are helpful in analyzing the performance of FD in various communication scenarios such as LoS/NLoS conditions and hence pave the way for more realistic FDR.     

Cognitive amplify‐and‐forward relay networks with beamforming under primary user power constraint over Nakagami‐m fading channels

In this paper, we analyze the performance of cognitive amplify‐and‐forward (AF) relay networks with beamforming under the peak interference power constraint of the primary user (PU). We focus on the scenario that beamforming is applied at the multi‐antenna secondary transmitter and receiver. Also, the secondary relay network operates in channel state information‐assisted AF mode, and the signals undergo independent Nakagami‐m fading. In particular, closed‐form expressions for the outage probability and symbol error rate (SER) of the considered network over Nakagami‐m fading are presented. More importantly, asymptotic closed‐form expressions for the outage probability and SER are derived. These tractable closed‐form expressions for the network performance readily enable us to evaluate and examine the impact of network parameters on the system performance. Specifically, the impact of the number of antennas, the fading severity parameters, the channel mean powers, and the peak interference power is addressed. The asymptotic analysis manifests that the peak interference power constraint imposed on the secondary relay network has no effect on the diversity gain. However, the coding gain is affected by the fading parameters of the links from the primary receiver to the secondary relay network. Copyright © 2012 John Wiley & Sons, Ltd.     

Decode‐and‐forward two‐way relaying protocol with one retransmission

This paper investigates the decode‐and‐forward two‐way relaying channel without direct link and proposes a protocol based on the physical‐layer network coding (PNC) protocol. The proposed protocol (termed ORT) introduces one retransmission into PNC, aiming at enhancing its outage performance. To manifest the merits of ORT, we compare it with PNC and the time‐division broadcast (TDBC) protocol, in terms of outage performance, expected rate, and diversity‐multiplexing tradeoff (DMT). Firstly, we derive the outage probability of the three protocols and then the expected rate. Secondly, asymptotic analysis is conducted to shed light on the diversity and coding gains. Finally, the DMT is obtained for the three protocols. The numerical results reveal the following: (i) that ORT performs better than PNC in both outage and expected rate performance when the nodes transmit with different powers. However, it has the same DMT performance with PNC; (ii) that ORT possesses improved DMT performance over TDBC whereas its expected rate is only better than the latter at medium to high signal‐to‐noise ratio. Copyright © 2012 John Wiley & Sons, Ltd.     

Novel noncoherent detection for multi‐hop amplify‐and‐forward relaying systems

Because of the multiplication of fading gains and noise, the actual distributions of the received signals in multi‐hop amplify‐and‐forward relaying systems are no longer Gaussian. In this work, they are fitted with the t location‐scale distribution and the logistic distribution. Using these distributions, two novel noncoherent detectors are proposed based on the maximum likelihood method. Numerical results show that both new detectors outperform the conventional energy detector. The performance gain increases when the signal‐to‐noise ratio increases or when the hop number decreases. Importantly, the bit error rate of the conventional energy detector reaches an error floor while the bit error rates of the new detectors do not. Copyright © 2015 John Wiley & Sons, Ltd.     

Performance analysis and power allocation for decode‐and‐forward cooperative communications over Rician fading channel

This paper derives the asymptotic symbol error rate (SER) and outage probability of decode‐and‐forward (DF) cooperative communications over Rician fading channels. How to optimally allocate the total power is also addressed when the performance metric in terms of SER or outage probability is taken into consideration. Analysis reveals the insights that Rician factor has a great impact on the system performance as compared with the channel variance, and the relay–destination channel quality is of importance. In addition, the source–relay channel condition is irrelevant to the optimal power allocation design. Simulation and numerical evaluation substantiate the tightness of the asymptotic expressions in the high‐SNR regions and demonstrate the accuracy of our theoretical analysis. Copyright © 2011 John Wiley & Sons, Ltd.     

Performance analysis of selective combining decode‐and‐forward relay networks over Nakagami‐n and Nakagami‐q fading channels

In this paper, we present the performance of selective combining decode‐and‐forward relay networks in independent and non‐identically distributed Nakagami‐n and Nakagami‐q fading channels by using the best–worse and the decoding‐set approaches. The outage probability, moment generation function, symbol error probability and average channel capacity are derived in closed‐form using the signal to noise ratio (SNR) statistical characteristics. After that, we analyze the outage probability at high SNRs, and then, we optimize it. Beside the optimum method, we have proposed a sub‐optimum adaptive method. Also, we derive the outage probability for the selection‐combining case with the direct link between the source and the destination. Finally, for comparison with analytical formulas, we perform some Monte‐Carlo simulations. Copyright © 2012 John Wiley & Sons, Ltd.     

Serial relaying communications over generalized‐gamma fading channels

In this paper, a study on the end‐to‐end performance of multi‐hop non‐regenerative relaying networks over independent generalized‐gamma (GG) fading channels is presented. Using an upper bound for the end‐to‐end signal‐to‐noise ratio (SNR), novel closed‐form expressions for the probability density function, the moments, and the moments‐generating function of the end‐to‐end SNR are presented. Based on these derived formulas, lower bounds for the outage and the average bit error probability (ABEP) are derived in closed form. Special attention is given to the low‐ and high‐SNR regions having practical interest as well as to the Nakagami fading scenario. Moreover, the performance of the considered system when employing adaptive square‐quadrature amplitude modulation is further analyzed in terms of the average spectral efficiency, the bit error outage, and the ABEP. Computer simulation results verify the tightness and the accuracy of the proposed bounds. Copyright © 2011 John Wiley & Sons, Ltd.     

An amplify‐and‐forward and decode‐and‐forward mixed relay communication system and its performance analysis

A kind of amplify‐and‐forward (AF) and decode‐and‐forward (DF) mixed relay communication system is proposed in this letter. The source broadcasts the signal to all the relays. Relays that can decode the signal adopt DF scheme to retransmit the signal, while the rest adopt AF scheme for retransmission. The destination employs maximum ratio combining technique to maximize the received signal‐to‐noise ratio. Another situation concerned in this letter is that when the relay cannot decode the source signal, it may retransmit the interference signal with AF scheme. Closed‐form expressions of outage probability are derived. Simulation results show that the analytical curves agree with the simulated ones very well, and the AF‐DF mixed relay system can improve the availability of the relays. Copyright © 2013 John Wiley & Sons, Ltd.     

Spectrally‐Efficient Decode‐and‐Forward Scheme Based on Constellation Rotation

A spectrally‐efficient scheme is proposed for orthogonal decode‐and‐forward relaying. By utilizing constellation rotation, the scheme can achieve twice the spectral efficiency as that of the conventional one, with low implementation complexity. It can offer a full diversity order as well, whereas the loss in coding gain is less than 1 dB for practical environments.     

Outage analysis of opportunistic‐based hybrid decode‐amplify‐forward relaying in polar code environment

Outage analysis plays a vital role in wireless systems to determine reliable transmission and effective communication. Incremental hybrid decode‐amplify‐forward (IHDAF) relay offers a way of meeting the challenges of capacity and coverage improvement with great potential in cooperative communication networks. Therefore, opportunistic incremental hybrid relaying must be integrated with coding schemes to achieve full diversity. In this paper, the outage behavior of polar coded and distributed coded cooperative relaying schemes is analyzed. Simulation results show that opportunistic incremental HDAF using polar code offers an outage capacity of 17 b/s/Hz for 4 × 4 multiantenna and 45 b/s/Hz in 8 × 8 multiantenna systems with an outage of 10^?8 and 10^?13, respectively. Moreover, the polar coded opportunistic IHDAF system in 8 × 8 MIMO achieves 2 and 6 dB higher gains compared with amplify‐and‐forward (AF) and decode‐and‐forward (DF) relaying schemes. The closed‐form expression for outage probability has been derived through Marcum‐Q approximations and processed through Monte Carlo simulations.     

Secrecy performance analysis of AF relaying with relay selection scheme over Nakagami‐m fading channels

This paper investigates the secrecy outage probability (SOP) and intercept behavior for the amplify‐and‐forward network over Nakagami‐m fading channels. Relay selection schemes are evaluated. The optimal and suboptimal criterions require the instantaneous and statistical channel state information of the eavesdroppers' channels, respectively. The enhanced 2‐hop criterion needs the additional information of the target secrecy rate for relay selection. Theoretical analysis reveals that the diversity order of the SOP is dominated by the minimum fading figures of the source‐relay and relay‐destination channels, while that of the intercept probability depends on the fading figure of the relay‐destination channel. In the multirelay scenario, the optimal, suboptimal, and enhanced 2‐hop scheme achieve the same diversity orders of the SOP. For the intercept probability, the optimal and second‐hop relay selection schemes provide the same diversity order, while the diversity orders of the suboptimal and enhanced 2‐hop schemes are the same. Simulation results finally substantiate the accuracy of the theoretical analysis.     

Comparison of average symbol error rate and optimal power allocation for two‐way opportunistic relaying with amplify‐and‐forward protocol

In this paper, we investigate the statistical characteristics of the equivalent end‐to‐end signal‐to‐noise ratios (SNRs), the average symbol error ratios (SERs), and the optimal power allocation (OPA) for two‐way amplify‐and‐forward opportunistic relaying (TWOR‐AF) systems. First, with strict mathematic manipulation, we obtain the closed‐form solutions to the PDF, CDF, and moment generating function of the end‐to‐end SNRs. Then, based on the obtained statistical results, we present the total average SER of the Non‐OPA TWOR‐AF systems by using the appropriate approximation, in which only the greater segment of the two terminal SERs is considered. Finally, by aiming at minimizing the total average SER and using the SNRs balancing condition at both transceivers, we study the OPA problem subject to a total transmission power constraint. The comparison analysis shows that, for the Non‐OPA TWOR‐AF systems, we can only evaluate exactly the greater segment of the two SERs of the received signals at two transceivers by using the derivations. However, for the OPA TWOR‐AF systems, with our derivations we can evaluate exactly not only each segment of the two terminal SERs but also the sum SER (exact total SER). Moreover, the simulations show the OPA TWOR‐AF systems outperform the Non‐OPA TWOR‐AF systems. Copyright © 2012 John Wiley & Sons, Ltd.