Search

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]

The huge increase in the communication network rate has made the application fields and scenarios for vehicular ad hoc networks more abundant and diversified and proposed more requirements for the efficiency and quality of data transmission. To improve the limited communication distance and poor communication quality of the Internet of Vehicles (IoV), an optimal intelligent routing algorithm is proposed in this paper. Combined multi-weight decision algorithm with the greedy perimeter stateless routing protocol, designed and evaluated standardized function for link stability. Linear additive weighting is used to optimize link stability and distance to improve the packet delivery rate of the IoV. The blockchain system is used as the storage structure for relay data, and the smart contract incentive algorithm based on machine learning is used to encourage relay vehicles to provide more communication bandwidth for data packet transmission. The proposed scheme is simulated and analyzed under different scenarios and different parameters. The experimental results demonstrate that the proposed scheme can effectively reduce the packet loss rate and improve system performance.

With the analysis of the main factors aff ecting the image acquisition of land remote sensing satellite, the satellite image data transmission application mode based on space-based relay was proposed to solve the bottleneck problem of satellite-ground receiving.Through simulation analysis and quantitative calculation, the application eff ect of relay transmission was calculated.The results showed that relay transmission could improved the visible time of satellite data receiving, thus greatly improved the total amount of image acquisition, and eff ectived perform the satellite operation effi ciency.

The unmanned aerial vehicle (UAV) relay system has become a hot topic as an effective method for the remote transmission in wireless communications.By taking path loss into account,a relay cooperative transmission system model based on multiple UAVs was established firstly,and the maximum output signal-to-noise ratio (SNR) of the system with threshold-based decode-and-forward (DF) protocol was obtained.Then,by assuming that both the uplink and downlink experience Rician distribution,the closed-form expression for outage probability (OP) of the considered system with multiple UAVs was derived.Furthermore,the asymptotic OP formula at high SNR was also derived to show the diversity order and array gain of the considered system,which were convenient to reveal the effects of system parameters on the outage performance.Finally,the computer simulations verify the correctness of the theoretical analysis,and reveal the effect of the relay number,antenna number and the threshold on the system outage performance,thus the proposed scheme can provide guidance for the system design and application.

In this paper, we investigate the resource optimization algorithm design in a multicarrier relay system with simultaneous wireless information and power transfer (SWIPT). The relay is capable of harvesting energy from the source's signals by using the power splitting method. The non-ideal energy consumption including both the non-ideal power amplifier and non-ideal circuit power consumption is considered. First, we study the transmission rate maximization problem (TRMP) in an asymmetric decode-and-forward (DF) relay transmission, where the transmission power at the source, the transmission power at the relay, the power splitting ratio, and the transmission time are jointly optimized. The formulated problem is a non-convex problem, and it is generally quite difficult to solve it. By exploiting the structure of the problem, we propose two methods (logarithmic operation on constraints and logarithmic change of variables) to transform it into the corresponding difference of convex (DC) optimization problems. Then, we extend the TRMP to an amplify-and-forward (AF) relay transmission. Furthermore, we propose an effective algorithm to solve the DC optimization problem and prove that the algorithm can converge to a stationary point. Finally, extensive simulations are conducted to verify the performance of the proposed algorithm. The simulation results show that the asymmetric DF relay transmission achieves the highest sum rate and the AF relay transmission achieves a much lower sum rate than both the asymmetric and symmetric DF relay transmissions under different conditions.

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]

Copyright of Telecommunications Science is the property of Beijing Xintong Media Co., Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

An innovative EE-oriented cooperative sensing and transmission scheme in relay-assisted cognitive radio networks,called energy-efficient best-relay cooperative transmission (BCT) was proposed.Based on the BCT scheme,mean energy efficiency (MEE) maximization problem with sensing duration and transmitting power as optimization variables was modeled for fading channels under constraint of minimal secondary outage probability.By virtue of Jensen’s inequality,the original optimization problem was decomposed into two relatively independent subproblems which solved sensing duration and power allocation respectively.And for the two subproblems,an efficient cross iteration based algorithm was proposed to obtain the suboptimal solutions.Both analytical and simulation results demonstrate that the proposals can achieve significantly higher EE while enhancing reliability of secondary transmission remarkably compared to non-cooperation single cognitive transmission schemesin high QoS requirement.

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]

The Internet of Things (IoT) depicts a bright future, where any devices having sensorial and computing capabilities can interact with each other. Among all existing technologies, the techniques for the fifth generation (5G) systems are the main driving force for the actualization of IoT concept. However, due to the heterogeneous environment in 5G networks and the broadcast nature of radio propagation, the security assurance against eavesdropping is a vital yet challenging task. In this paper, we focus on the transmission design for secure relay communications in IoT networks, where the communication is exposed to eavesdroppers with unknown number and locations. The randomize-and-forward relay strategy specially designed for secure multi-hop communications is employed in our transmission protocol. First, we consider a single-antenna scenario, where all the devices in the network are equipped with the single antenna. We derive the expression for the secrecy outage probability of the two-hop transmission. Following this, a secrecy-rate-maximization problem subject to a secrecy-outage-probability constraint is formulated. The optimal power allocation and codeword rate design are obtained. Furthermore, we generalize the above analyses to a more generic scenario, where the relay and eavesdroppers are equipped with multiple antennas. Numerical results show that the proper use of relay transmission can enhance the secrecy throughput and extend the secure coverage range.

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]

Unmanned Aerial Vehicles (UAVs) can assist Internet of Things (IoT) systems in collecting data from sensor nodes due to their high flexibility and ease of deployment. However, in existing UAV-assisted IoTs, there is neither mission overlap nor mission collaboration between UAVs, which requires all UAVs to return to the base station to offload the collected data. This results in significant latency in data transmission. Therefore, we propose a proximity-remote region collaborative data collection scheme to overcome this problem. In this scheme, we first divide the mission region into the proximity region and the remote region, and deploy an appropriate ratio of UAVs in each region for data collection. Second, we balance the flight paths of UAVs in different regions by updating the partition. Finally, we achieve seamless relay transmission between UAVs by selecting relay points, modifying UAV flight paths, and adjusting flight speed and take-off points. Through the above process, data collected from the remote region can rapidly reach the base station through seamless collaborative relays between UAVs. Extensive experimental results have shown that the proposed scheme can effectively reduce the data transmission latency of the system compared to existing data collection schemes. [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]

In this paper two miltihop decode-and-forward relaying architectures are examined - one-way relaying and shared relaying. A hexagonal cellular architecture with 12 base stations is simulated to take into account realistic system interference. Each base station is further partitioned into 6 sectors. Considering channel effects such as path loss, shadowing and fast fading, the achievable downlink sum-rate of the system is evaluated. The results show that shared relay architecture is more cost-efficient and profitable than the one-relay model. [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]