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In wireless communication, radio access is a key and important technology. Cognitive Radio (CR) and non-orthogonal multiple access (NOMA) are two promising technologies for next generation networks. The combination of CR and NOMA can improve spectral efficiency and outage probability. In this paper, we introduce an underlay CR inspired NOMA system, in which we use a coordinate direct and relay transmission scheme for data transmission. A relay is used to reduce the effect of co-channel interference in CR inspired NOMA system. The relay in this article functions as decode and forward. In this article, different from other existing literature, we use a new scheme for decoding primary and secondary users symbols in a way that increases system performance, improves outage probability and energy efficiency. In this method, in the first phase, the primary transmitter broadcasts the symbol of the primary user and the secondary transmitter broadcast a superimposed symbol. In the second phase, the relay makes a decision based on the detection result based on the proposed plan and transmits the symbols. The primary and secondary users combine the first and second phase signals to improve the outage probability and increase system performance. Based on this, we introduce a signal-to- interference plus noise ratio combined, the use of this method improves the probability of outage compared to the other designs in this article. In this article, the closed form for the outage probabilities of the primary and secondary users has been extracted, as well as the outage probability at high signal-to-noise ratio (SNR)s and the asymptotic expressions for the outage probabilities of the primary and secondary users. Also, energy efficiency and throughput have been extracted for and it has been shown that choosing the optimal power allocation coefficient is important for increasing energy efficiency and throughput. Also, the simulation results show the high performance of the method proposed in this article compared to other designs. [ABSTRACT FROM AUTHOR]

In the multi hop communication of wireless sensor networks, relay stations are used to realize remote transmission. In order to avoid the air data repeating collision problem and multi-path retransmission problem of wireless signals sent by relay nodes, this paper proposes a relaying algorithm using dual buffer pool. The node buffer pool is added in the node to store the package source identifier and packet count pairs, the package buffer pool is added to the package to store paths in transmission. First, after the package is received from radio, the node compares the pairs of the SID and Count in the node buffer pool with the pairs of the package source identifier and package count in the package. If there are pairs, the package is discarded, otherwise the package source identifier and package count are added into the node buffer pool. Next step, if the node identifier is equal to the destination byte DID in package, the package will be processed in the node and terminated transmission, otherwise the package will be continued to process. Then the node compares the node identifier with the package buffer pool bytes. If there is the node identifier in the package pool, the package will be discarded, otherwise the relay node stores its own node identifier into the packet buffer pool to create a new package and transmit forwards. The algorithm is implemented on CC2530 chip and relaying experiments of wireless sensor network are carried out. The results show that the algorithm can achieve relay forwarding and avoid duplicating forwarding data collision and avoid multipaths duplicate forwarding. [ABSTRACT FROM AUTHOR]

Vehicle-to-vehicle (V2V) communication-based cooperative vehicular networks are a key technology for future smarter transportation systems as they provide various applications for addressing road safety and traffic congestion. To alleviate the performance limitations of existing dedicated short-range communication (DSRC) protocols, cellular-assisted V2V communications have been proposed recently, wherein cellular base stations (BSs) relay the transmission from one vehicle to another. Such cellular-assisted communications have shown promise for more reliable V2V communications with a wider capacity and longer transmission distances. In this study, we theoretically analyze the performance of cellular-relay (CR) V2V communications, in which a vehicle first transmits a message to its nearest BS via uplink, and then, the BS forwards the message to a destination vehicle via downlink. We model the road segments through a Poisson line process and the positions of vehicles through a Poisson point process on the roads; subsequently, we derive a theoretical expression for the probability of a successful CR transmission and the mean local delay in the CR transmission. Furthermore, we propose a performance metric to evaluate the difference between the performances of CR and direct V2V communications, and it can be applied to automatic transmission mode selection (i.e., CR or direct) for V2V communications. We evaluate the analytical results using numerical examples and demonstrate the impacts of various system parameters on the performances of CR and direct V2V communications. [ABSTRACT FROM AUTHOR]

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The magnetic induction (MI) communication is an emerging undersea communication method, but its practical application is restricted by its limited communication distance. In this paper, an air-to-undersea magnetic induction communication scheme based on relay transmission is proposed, which can not only increase the penetrating depth but also expand the radial distance, so as to obtain a large submerged coverage of magnetic induction communication. What's more, the undersea magnetic field distribution is used to define the submerged communication range which is used as a measurement for evaluating the performance of the proposed scheme. The numerical results demonstrate that the relay transmission can multiply the submerged depth and radial distance of MI communication by deploying multiple relay nodes in predetermined positions, thus significantly increase underwater coverage of the air-to-undersea MI communication. [ABSTRACT FROM AUTHOR]

To address the problem of multiple access for a large number of devices in machine-type communication (MTC), we study the use of full-duplex relays. In-band-full-duplex (IBFD) allows devices to receive and transmit concurrently on the same frequency band, potentially doubling the spectral efficiency. On the downside, the use of IBFD raises mutual interference due to an increased density of concurrently transmitting nodes. This paper deals with the tradeoff between the increased spectral efficiency and increased interference in utilizing the IBFD uplink relays in a densely deployed MTC network. Using stochastic geometry, we develop a framework to evaluate the end-to-end outage probability and the uplink data transmission rate in a single-hop relay network for MTC. A fraction of MTC devices (MTCDs) can be scheduled to transmit in the same band as the relay nodes, with the rest transmitting on an orthogonal band. The relay nodes, therefore, operate either as IBFD or out-band-full-duplex (OBFD) depending on their associated MTCD and forward packets to base stations (BSs). The BSs employ linear zero-forcing filters to cancel the interference from their associated relays. We calculate the optimal fraction of in-band MTCDs and relative transmit powers of relay and MTCDs to maximize the area spectral efficiency. The appeal of in-band scheduling increases as more antennas are deployed at the BS. [ABSTRACT FROM AUTHOR]

The integration of wireless power transfer (WPT) with the low-power backscatter communications provides a promising way to sustain battery-less wireless networks. In this paper, we consider a backscatter communication network wirelessly powered by a power beacon station (PBS). Each backscatter radio uses the harvested energy to power its data transmissions, in which some other radios can help as the wireless relays with an aim to improve throughput performance by cooperative transmission. Under this setting, we formulate a throughput maximization problem to jointly optimize WPT and the relay strategy of the backscatter radios. An iterative algorithm with reduced complexity and communication overhead is proposed to decompose the original problem into two sub-problems distributed at the PBS and the backscatter receiver. Moreover, we take uncertain channel information into consideration and formulate robust counter-parts of the throughput maximization problem when either the backscatter or relay channel is subject to estimation errors. The difficulty of the robust counter-part lies in the coupling of the PBS’ power allocation and relay strategy in matrix inequalities, which is addressed by alternating optimization with guaranteed convergence. Numerical results reveal that the cooperative relay strategy of the backscatter radios significantly improves the throughput performance. [ABSTRACT FROM AUTHOR]

To accommodate massive access for machine-type communication (MTC) in cellular networks, we propose two single-hop relaying schemes exclusively designed for the MTC: signal-to-interference ratio-based relaying and location-based relaying. The relay nodes capture one or more MTC device (MTCD) transmissions and forward them to the base station (BS), thus reducing the signaling overhead in the cellular network. To efficiently use the spectrum, MTCDs make concurrent transmissions, and therefore create interference with each other. Unlike related work assuming known interference values for each link, we use stochastic geometry to characterize the received signal and interference powers. We derive the outage probability expressions and analytically calculate the maximum density of MTCDs that can be supported under an outage constraint. Moreover, the optimal partitioning of spectrum resources into the MTCD-to-relay, and relay-to-BS links, for maximum transmission capacity is presented. [ABSTRACT FROM PUBLISHER]

In order to reduce computation complexity and latency in cooperative communication system based on fountain code, a decomposed LT codes (DLT) based cooperative transmission scheme was proposed. The scheme comprises of two layers of random encoding but only a single layer of decoding. A general decomposition technique for the decomposed LT codes construction is developed. The transmission latency for the proposed scheme was analyzed. Simulation results show that the total time consumed under the proposed scheme can be significantly reduced compared to direct transmission and conventional cooperative transmission based on LT codes in the medium to high packet erasure rate regimes. Moreover, With the increase of packet erasure rate, the advantage of the proposed scheme is more evident. [ABSTRACT FROM AUTHOR]

In cognitive networks, the cooperative transmission between primary user and secondary user has been regarded as an effective method to promote harmonious coexistence between themselves where how to balance user's benefits and improve the system throughput is a key issue. In this paper, we study the joint pricing and power allocation strategy for the cognitive relay transmission by using the Stackelberg model which is a classical dynamic game model. We first give presentations of a cognitive relay model over Rayleigh fading channels and then investigate the primary benefits in power saving during this cooperation. According to the profits of primary user (as a game leader) and secondary user (as a follower), corresponding utility functions which describe their overall profits in the cognitive relay transmission are derived one by one. Then, optimal strategies for interference pricing and power allocation are fixed by resolving the objective functions. The existence of the Nash equilibrium and the sufficient conditions for the positive equilibrium are further discussed. Numerical results are presented to show that the algorithm can achieve encouraging outcomes with low-complexity. [ABSTRACT FROM AUTHOR]

Energy accumulation and information accumulation are two approaches to exploit multiple transmissions in wireless relay systems. There is a tradeoff between energy accumulation and information accumulation from an outage perspective, in which a packet is successfully received if the channel capacity exceeds the transmission rate. However, how to strike a balance between these two approaches is still unknown. In this paper, we propose a new rateless-coding-based transmission scheme in wireless relay systems, where the relay superposes two rateless-coded packets generated from different codebooks to strike a balance between energy accumulation and information accumulation. We analyze the average end-to-end throughput of the proposed scheme and formulate an optimization problem to find the optimal power allocation ratio. Simulation results will validate our analysis and show that, compared with pure energy accumulation and pure information accumulation, our proposed scheme can achieve substantial throughput gain. [ABSTRACT FROM PUBLISHER]

Herein, we present a novel approach for decode-forward relay transmissions using multiple antennas. In this approach, multiple independent spatial data streams are sent to the destination directly and/or through different relays simultaneously, where the relays are selected in an opportunistic way. We show the efficiency of the proposed approach through simulations. [ABSTRACT FROM AUTHOR]

In this paper, the performance of the network coded amplify-forward cooperative protocol is studied. The use of network coding can suppress the bandwidth resource consumed by relay transmission, and hence increase the spectral efficiency of cooperative diversity. A distributed strategy of relay selection is applied to the cooperative scheme, which can reduce system overhead and also facilitate the development of the explicit expressions of information metrics, such as outage probability and ergodic capacity. Both analytical and numerical results demonstrate that the proposed protocol can achieve large ergodic capacity and full diversity gain simultaneously. [ABSTRACT FROM PUBLISHER]

Relay links are expected to play a critical role in the design of wireless networks. This paper investigates the energy efficiency of relay communications in the low-power regime under two different scenarios: when the relay has unlimited power supply and when it has limited power supply. A system with a source node, a destination node, and a single relay operating in the time division duplex (TDD) mode was considered. Analysis and simulations are used to compare the energy required for transmitting one information bit in three different relay schemes: amplify and forward (AnF), decode and forward (DnF), and block Markov coding (BMC). Relative merits of these relay schemes in comparison with direct transmissions (direct Tx) are discussed. The optimal allocation of power and transmission time between source and relay is also studied. [ABSTRACT FROM PUBLISHER]

Two-way wireless communication has regained significant attention recently over relay channels and network coding techniques have been adopted to improve the spectral efficiency. In the literature, most works assumed knowledge of the channel state information at the transmitter (CSIT) and focused mainly on the three-step network coding (NetC) and two-step superposition coding (SupC) schemes. This work instead targets systems without CSIT and explores in detail the features and limitations of SupC and NetC under both the two-step and three-step frameworks. Equal-rate bi-directional traffic is considered and a comparative study of the schemes is provided. The maximum goodput and robustness to channel knowledge discrepancies are evaluated. Key results include theoretically derived outage regions and performance, and the analysis of the complementary role of NetC and SupC. Special features of the three-step framework and a simple yet efficient protocol, adaptive relay-assisted and direct transmission (ARDT), which smartly exploits the direct link in the absence of CSIT, will also be presented. Optimal power allocation at the relay is also derived for the three-step SupC scheme by exploiting the channel reciprocity (no CSIT required). A significant advantage of ARDT is demonstrated over the recently developed two-step SupC scheme. Numerical results together with extensive discussions are provided. [ABSTRACT FROM PUBLISHER]