Cooperative Diversity Systems Research Articles

On the Error and Outage Performance of Decode-and-Forward Cooperative Selection Diversity System With Correlated Links

A cooperative diversity system improves the communication reliability and throughput in a multipath fading environment with the help of relay nodes. We consider a cooperative diversity system with a source (S), a decode-and-forward relay (R), and a selection-combining-enabled destination (D). In this paper, we derive the exact end-to-end symbol error probability (SEP) for $M$ -ary phase-shift keying (MPSK) signaling using a paired error approach and differential binary phase-shift keying (DBPSK) signaling over correlated, nonidentical, slow, and flat Nakagami- $m$ fading channels by assuming the correlation between SD–RD, SR–SD, and SR–RD fading channels. In addition, we perform the exact outage probability analysis for the same scenario. Furthermore, we provide the asymptotic expressions for SEP and outage probability by removing the infinite-series terms to investigate the diversity order. In a nutshell, the numerical results reveal that the SR–RD correlated channel scenario outperforms the uncorrelated channel scenario in terms of SEP. In addition, SEP performance degradation is observed in the case of other correlated channel scenarios compared with the uncorrelated channel scenario. Moreover, marginal performance improvement in outage probability is observed in the low-signal-to-noise-ratio (SNR) regime of the SR–RD correlated channel scenario compared with the uncorrelated channel scenario. Finally, Monte Carlo simulations are performed to validate the theoretical results.

Symbol Error Rate Performance Analysis of Decode and Forward Cooperative Communication System

In this paper, we investigate the performance of Decode and Forward (DF) in multiple relay networks. We consider a cooperative diversity system where a source sends information to the destination with the aid of multi relay working in DF relaying protocol and investigate the Optimal Power Allocation (OPA) at both the source and the relay nodes. By taking advantage of the moment generating function (MGF), a closed form expression for the symbol error rate (SER) and signal to noise ratio (SNR) for both, M-Phase Shift Keying (MPSK) and M-Quadrature Amplitude Modulation (MQAM) signals has been derived to illustrate the asymptotic performance of the DF system where the approximation SER is tight at high SNR. Results show that the proposed system, based on SER lower bound is tight to the theoretical SER upper bound, and the suggested OPA outperforms the equal power allocation (EPA) and at different number of relays. DOI: http://dx.doi.org/10.11591/telkomnika.v15i1.8037

Performance of Hybrid Selection and Switch-and-Stay Combining With Decode-and-Forward Relaying

In this letter, an uncoded cooperative diversity system with a source, two decode-and-forward (DF) relays, and a destination (D) is considered. We propose a hybrid selection and switch-and-stay combining (HSSSC) scheme at D. Furthermore, we also derive the exact symbol error probability (SEP) of this scheme for DF relaying over slow and flat Rayleigh fading channels considering <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="TeX">$M$</tex-math></inline-formula> -ary phase-shift keying (MPSK) signaling using paired error approach. Numerical results reveal that full diversity order is achieved in the case of HSSSC scheme and improvement in the SEP performance is observed when compared to the distributed selection combining (SC), distributed scaled selection combining, and distributed switch-and-stay combining schemes proposed in the literature. In addition, the HSSSC scheme requires less channel state information (CSI) at D compared to the distributed full CSI SC scheme proposed in the literature.

A Buffer-Aided Successive Opportunistic Relay Selection Scheme With Power Adaptation and Inter-Relay Interference Cancellation for Cooperative Diversity Systems

In this paper we consider a simple cooperative network consisting of a source, a destination and a cluster of decode-and-forward half-duplex relays. At each time-slot, the source and (possibly) one of the relays transmit a packet to another relay and the destination, respectively, resulting in inter-relay interference (IRI). In this work, with the aid of buffers at the relays, we mitigate the detrimental effect of IRI through interference cancellation. More specifically, we propose the min-power scheme that minimizes the total energy expenditure per time slot under an IRI cancellation scheme. Apart from minimizing the energy expenditure, the min-power selection scheme, also provides better throughput and lower outage probability than existing works in the literature. It is the first time that interference cancellation is combined with buffer-aided relays and power adaptation to mitigate the IRI and minimize the energy expenditure. The new relay selection policy is analyzed in terms of outage probability and diversity, by modeling the evolution of the relay buffers as a Markov Chain (MC). We construct the state transition matrix of the MC, and hence obtain the steady state with which we can characterize the outage probability. The proposed scheme outperforms relevant state-of-the-art relay selection schemes in terms of throughput, diversity and energy efficiency, as demonstrated via examples.

Efficient Incremental Relaying for Packet Transmission Over Fading Channels

In this paper, we propose a novel relaying scheme for packet transmission over fading channels, which improves the spectral efficiency of cooperative diversity systems by utilizing limited feedback from the destination. Our scheme capitalizes on the fact that relaying is only required when direct transmission suffers deep fading. We calculate the packet error rate for the proposed efficient incremental relaying (EIR) scheme with both amplify and forward and decode and forward relaying. We compare the performance of the EIR scheme with the threshold-based incremental relaying (TIR) scheme. It is shown that the efficiency of the TIR scheme is better for lower values of the threshold. However, the efficiency of the TIR scheme for higher values of threshold is outperformed by the EIR. In addition, three new threshold-based adaptive EIR are devised to further improve the efficiency of the EIR scheme. We calculate the packet error rate and the efficiency of these new schemes to provide the analytical insight.

SLNC for Multi-Source Multi-Relay BICM-OFDM Systems

In this paper, we study the application of bit-interleaved coded modulation (BICM) and orthogonal frequency division multiplexing (OFDM) to reap the benefits of wireless multiuser network coding in practical frequency-selective fading channels. We propose a mapping based symbol level network coding (SLNC) scheme for a cooperative diversity system comprising multiple sources, multiple relays, and one common destination. A simple cooperative maximum-ratio combining scheme is used at the destination and is shown to successfully exploit both the full spatial and the full frequency diversity offered by the channel for arbitrary numbers of sources, arbitrary numbers of relays, and arbitrary linear modulation schemes. To gain analytical insight for system design, we derive a closed-form upper bound for the asymptotic worst-case pairwise error probability (PEP) and obtain the diversity gain of the considered SLNC scheme for BICM-OFDM systems. These analytical results reveal the influence of the various system parameters, such as the number of sources, the free distance of the code, and the frequency diversity of the involved links, on performance. Furthermore, we propose two different relay selection schemes for the considered system: a) bulk selection, i.e., a single best relay is selected to transmit on all sub-carriers, and b) per-subcarrier selection, where a best relay is selected on each sub-carrier. Last but not least, we exploit the derived PEP expression for selecting a subset of sources from the set of active sources when the number of active sources is larger than the number of available orthogonal relay channels. We study the achievable diversity gain for the proposed relay and source subset selection schemes. Numerical results corroborate the derived diversity gain expressions and confirm the performance gains.

Performance Analysis of DF Cooperative Diversity System With OSTBC Over Spatially Correlated Nakagami-$m$ Fading Channels

In this paper, we investigate the performance of a cooperative decode-and-forward (DF) multiple-input–multiple-output (MIMO) relaying system with orthogonal space–time block code (OSTBC) transmissions over spatially correlated Nakagami- <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$m$</tex></formula> fading channels for integer values of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$m$</tex></formula> . We consider both the opportunistic maximal-ratio combining (O-MRC) and <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\lambda$</tex></formula> -MRC receivers at the destination. For the former MRC, we give the closed-form expression for the cumulative distribution function (cdf) of the instantaneous end-to-end signal-to-noise ratio (SNR); relying on this, the exact analytical and asymptotic expressions are also derived for outage probability (OP) and symbol error rate (SER), whereas for the latter MRC, the closed-form expressions are derived for the exact and asymptotic bit error rate (BER) of binary phase-shift keying (BPSK) signals. The optimal value of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\lambda$</tex></formula> that minimizes the BER is also provided by using Newton's method. It is shown that O-MRC outperforms <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\lambda$</tex></formula> -MRC since the former MRC takes the relay decoding results into account. For <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\lambda$</tex></formula> -MRC, the optimal <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\lambda$</tex></formula> decreases with the increase in the SNR and spatial correlation since increasing the SNR and spatial correlation could increase the confidence of the source–destination link and decrease the confidence of the source–relay link, respectively.

Exact Error Analysis of MPAM Signaling for a Cooperative Diversity System with Correlated Links Using Paired Error Approach

In this letter, we consider an uncoded cooperative diversity system consisting of a source (S), a decode and forward (DF) relay (R), and a destination (D). We assume slow, flat, and correlated Nakagami-m fading environment and employ selection combining (SC) at D. Furthermore, we derive the exact end-to-end symbol error probability (SEP) of this system with M-ary pulse-amplitude modulation (MPAM) signaling using paired error approach. It is found from the numerical results that the SR-RD correlated-channel system performs better than the SD-RD correlated, SD-SR-RD correlated, and uncorrelated-channel systems.

Performance analysis of Switched Selection Combining with MPSK signaling for cooperative diversity systems

Cooperative diversity has been proved to be a technique which achieves higher data rate and throughput. We consider a single-relay cooperative diversity system employing decode and forward (DF) protocol. In this work, we present a new diversity combining technique which we call it as “Switched Selection Combining”, in which we combine the ideas of switched diversity and selection combining. In this technique, first, destination compares the instantaneous signal to noise ratio (SNR) of source-to-destination link with a threshold, if it is above threshold, the destination selects source-to-destination link else the destination compares the instantaneous SNR of source-to-destination link with relay-to-destination link and chooses whichever is higher. We derive the exact end-to-end symbol error probability of Switched Selection Combining with M-ary phase-shift keying (MPSK) for a flat Rayleigh fading. Results show that the Switched Selection Combining outperforms the conventional selection combining and the direct communication between the source and destination.

Performance analysis of selective decode and forward protocol with partner selection

Cooperative diversity is a technique that mitigates fading without additional cost, hardware and complexity. A cooperative diversity system having a source, multiple relays and a destination is considered. The end-to-end symbol error probability (SEP) of a full channel state information (CSI) selection combining scheme for cooperative communication, with selective decode and forward (S-DF) relaying for binary phase-shift keying (BPSK) symbol in a flat Rayleigh fading environment, is derived. Here, the effect of source-to-relay channel is included in the error analysis of cooperative diversity systems with selection combining. The threshold for S-DF is set with ratio factor α. On the basis of the optimised α value, the partner selection is performed. This scheme offers better SEP when compared with conventional selection combining scheme.

Colocated and Distributed Switch-and-Stay Combining: Optimality Under Switching Rate Constraints

Switch-and-stay combining (SSC) is a low-complexity alternative to selection combining (SC) in dual diversity systems. These diversity systems can either be the conventional colocated diversity setups, where two antennas are available at the receiver, or the cooperative diversity systems, where two relays assist one transmitter-receiver pair. In SSC, a single diversity branch (i.e., a single antenna or a single relay) is activated and remains active as long as the corresponding channel is sufficiently strong, regardless of the quality of the other branch. Thereby, the switching threshold determines both the bit error rate (BER) and the switching rate, which are defined as the number of times per second a branch switching occurs. Since high switching rates are not preferred in practice, in this paper, we optimize the switching threshold of SSC to minimize the BER under a constraint on the switching rate. To this end, we derive approximate closed-form solutions for the optimization problem for both the colocated and the distributed antenna case. These solutions are shown to achieve close-to-optimal performance through computer simulations.

Outage performance of multi-hop cooperative diversity system

An approximate outage probability formulation and diversity order were derived for multi-hop diversity system employing Decode-and-Forward(DF) relaying in high Signal-to-Noise Ratio(SNR).And a modified multi-hop Selective Decode-and-Forward(SDF) protocol was proposed to overcome the limitation of space full diversity system unemploying DF relaying,the source node resended the information when the relay could not decode information correctly.An approximate outage probability formulation and diversity order were deduced for SDF protocol in high SNR.The theoretical analysis and simulation results show that the SDF protocol can improve transmission performance and achieve the full space diversity contrasted with DF protocol.

Research on Power Allocation Scheme Based on Water-filling Algorithm in Cooperative Diversity System

为了提高协作分集系统的信道容量，该文在多中继节点协作背景下提出了基于注水算法的中继节点功率分配方案。首先，对空时矩阵的列序号提出了一种新的映射方案，该方案能够提升中继节点发射信号间的正交性。对于采用线性正交解码算法的GABBA码，列序号重新排布后能够降低误码率。然后，通过对接收信噪比与中继节点发射功率的分析，针对信道容量最大化问题提出了一种应用注水算法的两步求解方案。该文对瑞利平坦慢衰落信道下采用GABBA码的协作分集系统进行仿真，仿真结果表明，与中继节点发射功率均分方案相比，该文提出的功率分配方案能够提升系统抗误码性能，达到满分集增益NtNr。该文提出的方案在不同的仿真条件下对信道容量均有提升，并且信道容量与min{NtNr}log2M成正比。

Performance analysis of ARQ cooperative diversity system with multiple two-hop relays over Rayleigh fading channels

Cooperative communication systems can exploit spatial diversity by opportunistically choosing relays to forward information to the destination. In this paper, we investigate the statistical performance analysis of a general cross-layer automatic repeat request cooperative diversity (ACD) system by focusing on the scenario in which decode-and-forward relaying protocol and multiple two-hop relays are employed over Rayleigh fading channel environments. To obtain the theoretical closed-form formulas for end-to-end performance parameters, we develop a time division multiple access (TDMA)-based absorbing Markov model to help find all possible transition probabilities of each transmission process. Based on this proposed model and statistical analysis, we derive two tight closed-form expressions in terms of end-to-end packet delivery failure probability and end-to-end packet delivery delay distribution. In addition, an optimal power allocation scheme under a tight power constraint for the ACD system is proposed for further enhancing the symbol error rate (SER) performance, which outperforms the equal power allocation scheme obviously. Simulation results by Monte Carlo simulations demonstrate the correctness of our analysis eventually.

Performance and Optimization of Network-Coded Cooperative Diversity Systems

In this paper, we study network-coded cooperative diversity (NCCD) systems comprising multiple sources, one relay, and one destination, where the relay detects the packets received from all sources and performs Galois field (GF) network coding over rm GF(2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sup> ) before forwarding a single packet to the destination. Assuming independent Rayleigh fading for all links of the network, we derive simple and accurate closed-form approximations for the asymptotic symbol and bit error rates of NCCD systems. The derived error rate expressions are valid for arbitrary numbers of sources, arbitrary modulation schemes, and arbitrary constellation mappings and provide significant insight into the impact of various system and channel parameters on performance. Moreover, these expressions can be exploited for optimization of the constellation mapping as well as for formulation of various NCCD system optimization problems including optimal power allocation, relay selection, and relay placement.

Performance of MIMO Relay DCSK-CD Systems Over Nakagami Fading Channels

A multi-access multiple-input multiple-output (MIMO) relay differential chaos shift keying cooperative diversity (DCSK-CD) system is proposed in this paper as a comprehensive cooperation scheme, in which the relay and destination both employ multiple antennas to strengthen the robustness against signal fading in a wireless network. It is shown that, with spatial diversity gains, the bit error rate (BER) performance of the proposed system is remarkably better than the conventional DCSK non-cooperation (DCSK-NC) and DCSK cooperative communication (DCSK-CC) systems. Moreover, the exact BER and close-form expressions of the proposed system are derived over Nakagami fading channels through the moment generating function (MGF), which is shown to be highly consistent with the simulation results. Meanwhile, this paper illustrates a trade-off between the performance and the complexity, and provides a threshold for the number of relay antennas keeping the user consumed energy constant. Due to the above-mentioned advantages, the proposed system stands out as a good candidate or alternative for energy-constrained wireless communications based on chaotic modulation, especially for low-power and low-cost wireless personal area networks (WPANs).

Optimal incremental relaying in cooperative diversity systems

One of the main drawbacks of cooperative communication systems with half-duplex relaying is inefficient use of spectrum. Incremental relaying is an effective technique that overcomes this limitation. In this study, for a single-relay regenerative system, the authors propose a spectrally-efficient incremental relaying scheme that eliminates redundant relay transmissions such that the error propagation from the relay to the destination is effectively mitigated and the full diversity is achieved. The authors examine the impact of the error propagation on the performance of the system and derive closed-form expressions for the end-to-end symbol error probability (SEP) for different modulation schemes. They also derive an approximate closed-form expression for the optimal threshold that minimises the end-to-end SEP. The high-signal-to-noise ratio (SNR) analysis demonstrates that this threshold achieves full diversity whereas neither the bandwidth-consuming cyclic redundancy check code nor the availability of the instantaneous source–relay channel state information at the destination is required in the system. Furthermore, the authors purpose a class of thresholds that are independent of the network geometry and achieve full diversity. The asymptotic behaviour of the system shows that the spectral efficiency for both the optimal and geometry-independent thresholds in the high-SNR regime tends to the maximum achievable value.

A Cooperative Diversity Analysis of Two User Mobile Communication System with Maximal Ratio Combining

Cooperative communication is going to play a vital role in the next generation wireless networks. In this paper we derive the expression for symbol error probability (SEP) of a two-user cooperative diversity system, where two users cooperate through the decode-and-forward (DF) relaying with binary phase-shift keying (BPSK) modulation in a flat Rayleigh fading environment. We compare the computational results obtained by the SEP expression with the simulation results using maximal-ratio combining (MRC), equal-gain combining (EGC) and selection combining (SC) techniques. Numerical results show the performance of a cooperative diversity system with maximal-ratio combining is giving better results compared to SC and EGC techniques.

General Decode-and-Forward Cooperative Relaying with Co-Channel Interference in Shadowed Nakagami Fading Channels

General multi-branch multi-hop (MBMH) cooperative diversity systems with selection decode-and-forward (DF) relays are investigated on non-identical shadowed Nakagami-m fading channels in the presence of an arbitrary number of non-identical co-channel interferers. This paper presents closed-form expressions for the outage probability, the average symbol error probability, and the probability density function of signal-to-interference-plus-noise ratio of the selection DF MBMH cooperative relaying system. The results of the paper show that outage and error performance improvements against shadowing stem from the number of branches rather than the number of hops for a fixed number of relays. The results also show that the performance of the selection DF MBMH cooperative relaying system is more vulnerable when co-channel interferers are closer to the destination than when they are closer to the relays. This analysis is verified by Monte Carlo simulations.

레일레이 페이딩 채널에서 MRC/GSC 수신하는 DOT 릴레이 시스템의 성능

Opportunistic transmit cooperative relaying (OTR) system has been interested for its ability to mitigate the fading in wireless channel without multiple antennas in a small terminal. In OTR system, only the relays that the received Signal-to-noise ratio (SNR) from a source is greater than the threshold transmit to the destination. However, the receiving branches of a destination in a realistic system is fixed, the excess number of signals from the transmit relays does not improve the system performance and consequently increases power consumption. In this paper, we adopt Double Opportunistic Transmit (DOT) cooperative diversity system which controls the average number of transmit relays. Although the average number of the transmit relays can be controlled by adjusting the two thresholds in DOT system, the instantaneous number of transmit relays is varying in fading channel. Thus we propose Maximal Ratio Combining (MRC) or Generalized Selection Combining (GSC) according to the number of the signals from relays at the destination. The outage probability of the proposed system is derived in closed form. The analytical results show that the system performance is improved with the number of the branches. Also it is noticed that when the number of the branches is fixed, the outage probability decreases with the increase of the average SNR of S-R path and R-D path.