Beamforming Amplify-and-Forward Relay Networks With Feedback Delay and Interference

In this paper, the effect of feedback delays on the performance of multiple-input multiple-output antenna amplify-and-forward relay networks with the best transmit/receive antenna pair selection over Rayleigh fading is studied. The cumulative distribution function and the moment generating function of the end-to-end signal-to-noise ratio (SNR) are derived. Closed-form expressions for the outage probability, average symbol error rate (SER), and the SNR moments are also derived. To gain further insights, the asymptotic outage probability, average SER, diversity order, and coding gain are presented. Numerical results and Monte-Carlo simulations are provided to illustrate the detrimental effects of feedback delays on the system performance and to verify the accuracy of our analysis.

This paper investigates the outage probability of the multiuser transmit antenna selection/maximal-ratio combining (TAS/MRC) system over Rayleigh fading channels with outdated feedback. The exact outage probability is first derived. Then the asymptotic outage probability is analyzed to gain more insights into the effect of feedback delay. The analytical results show that: 1) increasing the number of users has the same effect on the outage probability as increasing the number of transmit antennas at the base station; 2) with outdated feedback, the asymptotic diversity order of the multiuser TAS/MRC system reduces to the number of receive antennas at the users. Theoretical analysis is verified by simulation results.

In this paper, the outage performance of multiuser multiple-input single-output (MISO) systems exploiting joint spatial and multiuser diversities is investigated for Rayleigh fading channels with outdated feedback. First, we derive closed-form exact outage probabilities for the joint diversity schemes that combine user scheduling with different spatial diversity techniques, including: 1) transmit maximum-ratio combining (TMRC); 2) transmit antenna selection (TAS); and 3) orthogonal space-time block coding (OSTBC). Then the asymptotic outage probabilities are analyzed to gain more insights into the effect of feedback delay. It is observed that with outdated feedback, the asymptotic diversity order of the multiuser OSTBC (M-OSTBC) scheme is equal to the number of transmit antennas at the base station, while that of the multiuser TMRC (M-TMRC) and the multiuser TAS (M-TAS) schemes reduce to one. Further by comparing the asymptotic outage probabilities, it is found that the M-TMRC scheme outperforms the M-TAS scheme, and the M-OSTBC scheme can perform best in the outage regime of practical interest when the feedback delay is large. Theoretical analysis is verified by simulation results.

This paper advocates the performance of wireless multiuser relay networks (MRNs) equipped with a single amplify-and-forward (AaF) relay. For such networks, we focus on opportunistic scheduling, in which the destination with the highest instantaneous end-to-end signal-to-noise ratio (SNR) is scheduled for transmission. The scheduled destination can receive either directly from the source or indirectly through the relay, based on cooperative selection diversity (CSD). Assuming Rayleigh fading channels, we first derive a new expression for the cumulative distribution function (CDF) of the received instantaneous end-to-end SNR. Then, relying on this statistical result, we present new exact expressions for the outage probability and symbol error rate (SER), both of which are obtained in closed-form. Furthermore, we derive simple yet valuable closed-form asymptotic expressions for the outage probability and SER in the high SNR regime. Our results explicitly reveal the impacts of CSD and opportunistic scheduling on the diversity order and array gain. Numerical results are presented to validate the analysis.

In this paper, we analyze the energy efficiency and the symbol error rate (SER) in the cooperative multiple-input multiple-output (MIMO) relay networks. We employ an amplify-and-forward (AF) relay scheme, where a relay access point occupied with Q antennas cooperatively forwards packets to the destination. Under the assumption of Rayleigh fading channels and time division multiplexing (TDM), we derive new exact closed-form expressions for the the outage probability, SER and the energy efficiency valid for Q antennas. Further asymptotic analysis is done in high SNR regime to characterize the energy efficiency in terms of the diversity order and the array gain. Subsequently, our expressions are quantitatively compared with Monte Carlo simulations. Numerical results are provided to validate the exact and the asymptotic expressions. The results show that the energy efficiency decreases with the number of antennas at the relay according to Q+1. The behavior of the energy efficiency with the relay locations is also discussed in this paper.

In this paper, we give a closed form expression for the statistics of two independent exponential for two-hop links of vehicular networks. Then these statistics results help us to analyze the performance of two-hop vehicular communication networks with vehicle relay based on Amplify and Forward (AF) protocol over flat Rayleigh-fading channels. It is shown that the choice of gain of AF effects on bounds on the performance of these relay vehicular networks. And outage probability formula is obtained. Furthermore, we give out specifically a vehicle relay selection scheme. The best vehicle relay has been selected by satisfying specific criteria in respect of signal-to-noise ratio (SNR). Finally, simulation results display the difference between regeneration and non-regeneration vehicular systems. At low average SNR, AF relay vehicular networks have better performance. However, these two kinds of systems have similar outage probability at high average SNR.

In the context of two-wave with diffuse power (TWDP) fading scenarios, this paper analyzes the outage probability and symbol error rate (SER) of single relay cooperative networks using amplify-and-forward (AF) relaying. Each channel in the network is assumed to be independently and non-identically distributed. The statistical result of the upper bound on the received signal-to-noise ratio (SNR) is derived. We derive the closed-form asymptotic expressions to approximate the outage probability and SER in the high SNR regime, respectively. Based on the asymptotic results, the diversity order and coding gain of the cooperative network is analyzed. Simulation results show that these asymptotic results are tight particularly in the high SNR regime for cooperative networks in different fading scenarios.

This paper examines the effect on Outage probability and Detection probability by using Maximal Ratio Combining (MRC), Square Law Combining (SLC) along with the addition of two relay transmission protocols Amplify and Forward (AF) and Decode and Forward (DF) over Rayleigh Fading Channel. In MRC the co-phased signals with highest Signal to Noise Ratio (SNR) are taken where SLC does not rely on phase estimation. The AF protocol works on the principle that the relay receives the signal and amplifies it along with the noise. In DF, the received signal at relay is decoded and again it is re-encoded before sending it to the destination. Single and multiple relays are taken in different scenarios and the diversity techniques (MRC and SLC) along with the relay transmission protocols (AF and DF) are analyzed. The performance of receiver's parameters, i.e. detection probability (P d ) and Outage probability (P out ) are examined. The simulation results clearly show the performance of the efficient combining scheme with the appropriate relay transmission protocol.

In this paper, the effect of feedback delay and channel gain difference (CGD) on the performance of distributed transmit diversity (DTD) systems are analyzed over Rayleigh fading channels. We derive new expressions for the average error rate of DTD in the absence of receiver phase compensation (RPC), which is useful for a large number of modulation schemes. Furthermore, we analyze the effect of feedback delay and CGD on DTD compared to spatially correlated co-located transmit diversity (CTD) systems. Analytical results enable us to verify the fact that in DTD without RPC as CGD between antennas increases the performance degrades. Via extensive performance evaluations for various cases, we quantitatively analyze the sensitivity of the performance gap between CTD and DTD in absence of RPC according to feedback delay. The results show that, in without RPC case DTD is robust to feedback delay compared to correlated CTD. We also present Monte Carlo simulation results as verification of our analytical results.

In this paper, we analyze the performance of a dual-hop system with partial relay selection and feedback delay over Nakagami-m fading channels in the presence of multiple identical interferers at the destination. Based on the new closed-form expressions for the cumulative distribution function of the effective signal-to-interference plus noise ratio, we present closed-form expressions for the outage probability and average symbol error rate (SER) for both fixed and CSI-assisted gain relaying systems. To gain further insights, the asymptotic outage probability and average symbol error rates at the high signal to noise ratio regimes are examined. Our results reveal that increasing the number of relays does not provide any extra diversity gain due to the presence of the feedback delay. Specifically, we show that feedback delay as well as CCI only affect the coding gain of the system. The accuracy of the analytical results are supported Monte-Carlo simulations.

Using Moment Generating Function for Performance Analysis in Non-Regenerative Cooperative Relay Networks with Max-Min Relay Selection

A comprehensive performance analysis of dual-hop multiple-input multiple-output amplify-forward relay networks with hop-by-hop beamforming is presented. The impact of practical transmission impairments; (i) feedback delays, (ii) channel estimation errors and (iii) spatially-correlated fading on the system performance is studied. Specifically, the amount of performance degradation due to these impairments are quantified analytically and illustrated through numerical results. Numerical results show that these impairments degrade the system performance significantly. The cumulative distribution function of the end-to-end signal-to-noise ratio is derived and used to obtain the moment generating function, the outage probability, and the average symbol error rate (SER) in closed-form. The asymptotic outage probability and average SER are derived to obtain valuable system-design insights such as the diversity order and array gain. Further, our analyses are validated through Monte-Carlo simulations.

Outage performance of cognitive DF relay networks with nonidentical Rayleigh fading channels and maximal ratio combining

This paper analyzes the performance of a power line carrier communication (PLCC) system under the effect of complex channel gain and additive background noise utilizing quadrature phase shift keying (QPSK) transmission scheme. The background noise considered here is complex in nature whose envelope is Nakagami-m distributed while phase follows uniform distribution. The magnitude and phase of complex channel gain coefficients are assumed to have Rayleigh and uniform distribution, respectively. Utilizing the sub-optimal decision rule for the real and imaginary parts of the complex data, and after deriving the expressions for the conditional probability density function (PDF) of the decision variables, we obtain a closed from expression for the conditional symbol error rate (SER) of the QPSK data for the considered system. Further, we analyze the outage performance of the considered PLCC system and derive the expression for conditional outage probability. The derived expressions of SER and outage probability are conditioned on the phase of the complex channel gain and the noise, which has been numerically averaged to get the analytical values for average SER and average outage probability. The analytical results presented in this paper have been verified by the simulations.

A performance analysis is presented for amplify-and-forward (AF) cooperative relay networks employing transmit antenna diversity with orthogonal space-time block codes (OSTBCs), where multiple antennas are equipped at the transmitter. We develop a symbol-error-rate (SER) and outage performance analysis for OSTBC transmissions with and without cooperative diversity over flat Rayleigh fading channels. We first derive exact probability density functions (pdf's) and cumulative distribution functions (cdf's) for the system SNR without direct transmission with an arbitrary number of transmit antennas and then present the exact closed-form SER and outage probability expressions. Next, we derive the moment-generating function (MGF) for the overall system SNR with direct transmission and present the exact SER and outage probability with joint transmit antenna diversity and cooperative diversity. The theoretical analysis is validated by simulations, which indicate an exact match between them. The results also show how the transmit antenna diversity and the cooperative diversity affect the overall system performance.