This paper proposes an efficient broadcasting system which combines cooperative non-orthogonal multiple access (CO-NOMA) and successive refinement (SR) coding. The objective is to construct uncorrelated descriptions of the same source information carried by different NOMA layers, such that each user can choose to decode only the basic description or both, depending on the quality-of-service (QoS) requirement. To enhance the performance of far NOMA users which demand a high QoS, user cooperation is invoked and two relaying schemes are proposed. Assuming all channels are suffered from block Rayleigh fading, the outage probabilities of the proposed system are mathematically derived in closed-form. The advantages over conventional NOMA and CO-NOMA are also demonstrated.

This paper investigates the physical layer security performance of an untrusted relay network in the finite blocklength regime. Lossy decode-and-forward (DF) relaying is considered at the untrusted relay. Different from conventional DF relaying, the relay always forwards information sequences to the destination even if error is detected at the relay, which can be utilized to enhance the security of the untrusted relay network. Based on the characteristics of short-packet communications, the reliable-and-secure probability is proposed and numerically derived for evaluating the security performance in the physical layer of the untrusted relay network. Reliable-and-secure probability represents the probability that the destination can recover the original message sent from the source, whereas the relays cannot. It is found that as long as the contribution of the transmit power of source and relays is balanced, a certain degree of reliable-and-secure probability can be held for short-packet communications in the untrusted relay network.

A two-untrusted-relay transmission scheme is proposed with lossy-forward (LF) relaying being utilized. Two untrusted relays are located between one source and one common destination and there is no direct link between the source and the destination, which referred to as diamond relaying network. Since LF relaying allows intra-link errors and always forwards the decoded information sequences from the relays to the destination, it realizes the reliable and secure transmission of decoder-and-forward based relay networks with untrusted relays. Reliable-and-secure probability is derived to evaluate the performance of the untrusted relay networks, which represents the probability that the destination can recover the original message sent from the source whereas the relays cannot. We find that as long as the contributions of the transmit power of source and relays are balanced, a certain degree of reliable-and-secure probability can be held, even without the support from a friendly jamming signal.

We consider correlated sources coding over a up-link non-orthogonal multiple access shadowed κ-µ fading channel. The sufficient condition for lossless coding is determined by the intersection of the Slepian-Wolf region and multiple access channel region, assuming source-channel separation holds. The exact expression for the outage probability upper bound is derived by dividing the sufficient conditions into three cases. The accuracy of the analytical results is verified by the Monte-Carlo simulations. The analytical results indicate that more than 2ndorder diversity gain can be achieved with a larger ratio of line-of-sight dominant component in single cluster or multiple clusters with non-line-of-sight component. It is also found that the shadowed κ-µ fading well represents one-sided Gaussian, Rayleigh, Rician, and Nakagami-m fading in calculating the outage probability. Furthermore, the ϵ-outage achievable rate is analyzed, which is found to be larger with higher source correlation and/or average signal-to-noise ratio.

Abstract The performance of correlated sources transmission over multiple access shadowed ‐ fading channels is investigated, in which one of the correlated sources needs to be recovered at the destination, whereas the other serves as a helper. The sufficient condition for lossless coding is determined by the intersection of the modified Slepian–Wolf region and the multiple access channel region. The outage probability upper bounds are derived based on the sufficient condition, with the Gaussian codebook capacity and the constellation constrained capacity, respectively. The difference between the outage probabilities derived with the two kinds of capacities is found to be very minor, when the spectrum efficiency or source rate is low; however, with high spectrum efficiency or high source rate, such difference becomes significant. A closed‐form outage approximation is also obtained at the high signal‐to‐noise ratio region. The accuracy of the analytical results is verified by the Monte‐Carlo simulations. It is found that shadowing significantly affects the outage performance, however, it has no effect on the diversity gain. Furthermore, the power allocation between the source and the helper is studied to minimize the outage probability and it is found that generally more power should be allocated to the helper in the case with higher source‐helper correlation.

This paper presents an in-depth performance analysis of lossy communications in a single-relay system, where the recovered information is not necessarily lossless in both the relay and the destination. In this system, the relay continues transmitting the sequence with source-relay (S-R) link errors to the destination even if errors are detected after decoding, i.e., so-called lossy-forward (LF) strategy. The problem can be decomposed into two parts as follows: a point-to-point coding problem in the S-R link and a lossy source coding problem with an LF relay in the source-destination (S-D) and a relay-destination (R-D) links. To begin with, we derive the admissible rate region of the lossy source coding problem with the LF relay for a specified distortion requirement. Then, we focus on the analysis of outage probability over block Rayleigh fading channels. Finally, a practical encoding/decoding scheme is proposed for the evaluation of system performance by computer simulations. Due to the suboptimal channel coding and incomplete utilization of joint typicality, the theoretical performance cannot be achieved in the simulation; however, the tendency of curves in simulations matches that in theoretical calculation.

Non-orthogonal transmission is considered to be one of the promising techniques for improving the throughput of the existing and future wireless communication networks. We concentrate on the transmission of both independent and correlated binary sources over a non-orthogonal multiple access relay channel (MARC), which consists of two sources, one relay, and one destination. The lossy decode-and-forward (DF), developed from the conventional DF, is adopted at the relay. Two time slots are required with non-orthogonal transmission over such network setup, while three time slots are required with the conventional orthogonal transmission. We analyze the outage probability of transmission of independent binary sources over the non-orthogonal MARC based on the theorem of multiple access channel (MAC) with a helper, which combines the Slepian-Wolf rate region and the MAC capacity region. For the performance verification, we implement a practical coding-decoding chain, which is applicable to the transmission of both independent and correlated binary sources. Exclusive-OR based multi-user complete decoding is introduced at the relay node, and iterative joint decoding is utilized at the destination by taking into consideration the estimated intra-link error probability and correlation information between the sources. The practical simulation results are well matched with the theoretical analyses.

Joint optimization of power allocation (PA) and relay position (RP) is investigated for a lossy-forwarding relaying in order to minimize the outage probability. We investigate adaptive PA with fixed relay position, adaptive RP with fixed PA ratio, and joint optimization of the PA and RP under total transmit power constraint. A closed-form expression of the outage probability is derived at the high signal-to-noise ratio regime. It is shown that the closed-form expression is sufficiently accurate compared to numerical calculation results. Then, the optimum PA and the optimum RP can be formulated as a convex optimization problem. It is found that the system performance with the adaptive optimum PA outperforms that with equal power allocation. The outage performance with the adaptive optimum RP outperforms that with midpoint RP. However, the joint optimization of the PA and RP is superior to the semi-adaptive optimization algorithms.

In this paper, the outage probability of a Slepian-Wolf transmission system is analysed theoretically. We consider two correlated binary information sequences where bit-flipping model is adopted, where the the information bits of the second source are the flipped version of the information bits of the first one, with a probability Pf. Here, we extend our previous work of the correlated sources transmission over block Rayleigh fading channels to such that the channel between one source and the destination is assumed to suffer from block Rayleigh fading, whereas the channel between the other source and the destination is assumed to suffer from block Rician fading. The outage probability is analysed theoretically. The results show that when Pf= 0, the outage curves versus signal-to-noise power ratio (SNR) exhibits sharper decay than that with the 2nd order diversity, as the line-of-sight (LOS) component power of Rician channel increases. It is also found that the outage curves asymptotically converge in to that with the 1st order diversity when Pf≠ 0. Furthermore, this paper also determines the optimal power allocation under the condition that total transmit power of the system is kept constant. It can be concluded that increasing the ratio of LOS component power of Rician channels can not always improve the outage performance, so far as Pf≠ 0.