268 results about "Amplify and forward" patented technology

A hybrid forwarding apparatus and method for cooperative relaying in an OFDM network are provided. In a hybrid forwarding apparatus in a relay terminal, a forwarding scheme selector selects a forwarding scheme for transmission. An amplify and forward (AF) block amplifies data received from the forwarding scheme selector, if an AF scheme is selected. A decode and forward (DF) block decodes and encodes data received from the forwarding scheme selector, if a DF scheme is selected. A multiplexer provides the output data of the AF block and the DF block to an OFDM modulator.

A combination of repeaters and relays is used to improve the data throughput for user equipment (“UE”) near the cell edge in a LTE network. Amplify-and-forward repeaters and decode-and-forward relays enhance the down-link and up-link, respectively. Relay assistance on the up-link occurs when the evolved Node B (“eNB”) requests a retransmission (HARQ) from the UE at which point the UE and relay transmit simultaneously in a cooperative fashion. The quality of the up-link signal received by the eNB is improved due to a favorable channel through the relay. An analysis shows that relay assistance improves the throughput for a cell-edge user when the average delay per data transport block is allowed to increase.

A wireless communication system includes an intermediate node, a first node and a second node. There is described a method for implementing MIMO based network coding, comprising the first node transmitting first data to the intermediate node, and the second node transmitting second data to the intermediate node. Both the first node and the second node may use spatial multiplexing or time division multiplexing or frequency division multiplexing on a common/different resource. The intermediate node receives the transmissions from the first node and second node, and performs network coding on the first data and second data using a predefined network coding scheme to produce network coded information. The intermediate node transmits the network coded information to the first node and second node using multi-user MIMO; and; each first or second node receives the MIMO transmissions from the intermediate node and applies network decoding procedures to recover the first data and second data. Network coding schemes include Decode and Forward (DF), Map and Forward (MF) and Amplify and Forward (AF). The first node and second node may be members of groups of nodes all within the same coverage area. A method for scheduling MIMO-based network coded transmissions is also described. Hybrid Automatic Repeat Request (HARQ) transmission may also be network encoded.

The invention discloses a broadband wireless sensor network transmission scheme based on amplify-and-forward single-node cooperation communication. The scheme is as follows: a source node is firstly used to make an orthogonal space-frequency coding to an original signal, two time slots are respectively used to transmit orthogonal signal frames, then a pilot frequency is inserted and coded signals are subject to IFFT operation to fight against the multi-path attenuation, the coded signals are converted onto a time domain, and the serial data flow is broadcast and sent after the insertion of a cyclic prefix and a training sequence. A first time slot relay node receives signals of the source node, makes frequency deviation and phase compensation, then adopts an amplify-and-forward protocol to synchronously send the processed signals to an information sink node at a second time slot and the source node; an information sink receiver receives a mixed signal from two independent channels, firstly detects a frame head of the signal of the second time slot, then synchronizes with the frame head, then carries out FFT operation to the signal part, converts the signal back to the frequency domain, and performs space-frequency decoding to obtain an original sending symbol. The scheme is simple and easy to operate, can effectively improve the error code rate performance of the system, has strong practicability, and is convenient for the realization of the hardware.

The invention discloses a physical layer security transmission method for resisting sniffing of unreliable relay nodes. The amplify-and-forward protocol is adopted by the method. The method comprises the following steps: firstly, estimating equivalent channels of all links between a source node and a destination node by the source node and the destination node, then, selectively combining a physical channel of a source node-relay node-destination node link and a random antenna at the source node, and designing random phase rotation for each transmitted symbol. As the relay nodes are independent and do not cooperate with each other, only the own local channel information can be known by each relay node; by utilizing the asymmetry of the existing channel information of the destination node and the relay nodes, the destination node is capable of smoothly decoding the information transmitted by the source node, and the relay nodes are incapable of performing correct coding due to the influence of random disturbance, and therefore the goal that the unreliable relay nodes are prevented from sniffing is achieved.

The invention discloses a power allocation algorithm for a UAV (unmanned aerial vehicle) relay system based on an energy efficiency optimal criterion. Firstly, based on a double-hop amplification andrelay transmission model, an optimization model of power allocation is established, and a power allocation problem is converted into an optimization problem of the solution of maximum system energy efficiency. In the process of solving the optimal power allocation, firstly transmitted signal power is fixed to obtain a beamforming optimization scheme. Then, by a large signal-to-noise ratio intervalapproximation, an original non-convex optimization problem is converted into a convex optimization problem. Finally, a KKT condition is used, and a closed form solution of a power allocation scheme is calculated and obtained. A simulation experiment shows that the closed form solution obtained by the algorithm disclosed by the present invention is close to a loop iterative method, and thus the algorithm complexity is reduced.

This invention provides a relay precoder selection method for two-way amplify-and-forward multiple-input multiple-output (MIMO) relay systems and communication devices using the selection method or the selected relay precoder. According to the relationship between a relay precoder and the singular values of the effective MIMO channels, a set of candidate relay precoders are constructed based on the singular vector subspaces of cascaded MIMO channels, and one of them is selected for meeting a specific design criterion, such as the minimum sum of mean-squared errors, the maximum sum of channel capacities, and the minimum or maximum sum of condition numbers, where the condition number is defined as the ratio of the largest to the smallest singular value of a MIMO channel. As compared with the iterative design methods with the best performance, this invention achieves close performance while requiring much lower computational complexity.

Disclosed is a method for static power allocation to source and relay stations in a two-hop amplify-and-forward (AF) relay multi-input-multi-output (MIMO) network including of a source station (SS), a relay station (RS), and a destination station (DS) each transmitting signals using multiple antennas. The method performs power allocation to the SS and the RS according to the path loss, or equivalently, according to a distances, between the SS and the RS and the RS and DS. The transmit power of each transmit antenna at the SS and the power amplifying gain of the RS are determined from the power allocation outputs.

The invention relates to a combined multi-user sending method of an auxiliary multi-user access system of a wireless repeater, which can improve frequency spectrum utilization of uplink multi-user access in a cellular wireless communication system. The system consists of a plurality of user terminals, a wireless repeater and a receiving device. The sending method has the following requirements: firstly, a plurality of users send signals by respective channels and the wireless repeater and the receiving device are in receiving state; and the wireless repeater carries out signal processing to the signals of a plurality of users and then sends the processed signals to the receiving device. The combined multi-user sending method of the wireless repeater comprises two types: the first types is as follows: the received signals of a plurality of users carries out linear superposition and then is amplified and is forwarded to the receiving device; and the second type is as follows: the wireless repeater carries out detection to the information of a plurality users, and if the detection is successful, the information of a plurality of users carries out multi-user combined coding and modulation and then is sent to the receiving equipment.

The method includes steps: transmitting end (TE) determines length value of Chu sequence as training sequence; estimating out noise power at each relay end and receiving end, and determining maximal number of nonzero tap in time domain response of channel between nodes, and determining power distribution coefficient (PDC) of each node; after determining value of length and PDC, and selecting corresponding Chu sequence and adding circular prefix (CP), TE carries out transmission at first time slot (TS); after receiving signal, each relay end carries out linear processing on the received signal based on PDC and unitary matrix, and then adds CP, and transmits them in second TS; the receiving end receives signals at first TS and second TS, and unites the received signals with CP being removed, further, carries out channel estimation (CE) by minimum mean-square value. Thus, the invention realizes CE in high precision and low complexity in cooperation comm containing multiple relay nodes.

A method for cooperative relay beamforming based on limited feedback is applicable to a communication system. The communication system comprises a transmitter, a plurality of relays and a receiver. The transmitter is provided with a plurality of antennae, each relay is provided with a single antenna, the receiver is provided with a plurality of antennae, and the plurality of the relays cooperate and adopt an amplification and forwarding protocol; the whole communication process is finished in two time slots, wherein in the first time sot, after performing transmit beamforming on a data flow, the transmitter broadcasts the data flow to all relays; and in the second time slot, all relays determine distributed beamforming code words according to limited feedback information containing code word indicators and power amplification factors from the receiver and forward receipt signals subjected to respective code word component treatment to a information sink; and the design of a code book is completed by code book design and cord word updating algorithm, the relays select code words which can maximize the instant signal to noise ratio of the receiver from the code book according to each channel condition as a beamforming vector.

A full-rate distributed space-time (ST) code design is provided for amplify-and-forward cooperative wireless channels. A signal space diversity technique is employed at the source node and a unique signature vector at each relay node. The distributed space-time (ST) codes can achieve full cooperative diversity and full rate. The achievable diversity gain is M+1, where M is the number of relay nodes. Optimal power allocation can be used to maximize the coding gain under a total power constraint.

The invention provides a multithread bidirectional relay transmission method based on amplification forwarding. The method comprises the following steps: (1) a relay antenna selection phase: two source nodes sends a training signal sequence to a relay node respectively, according to the received training signal sequence, the relay node estimates channel information between the relay node and the two source nodes respectively, two corresponding channel matrixes are obtained, according to the two channel matrixes, an antenna subset involving two users interaction communication is selected, complexity and forwarding energy consumption of a relay node processing signal is reduced, a diversity gain is obtained, and error code performance of a system is raised; (2) a bidirectional relay transmission phase: according to the selected antenna subset, the relay node carries out bidirectional relay transmission, and information interaction is completed. According to the invention, a high efficiency bidirectional communication strategy based on ANC (analog network coding) is employed, with regard to multithread transmission, an antenna selection scheme and a linear decoupling technique of a receiving signal are made, sending energy consumption and operation complexity are reduced, and a degree of freedom of a multiple-input-multiple-output bidirectional relay channel is effectively utilized.

A method and apparatus are described including receiving a first signal including first data in a first time slot of a first channel (705), receiving a second signal including second data in a second time slot of a second channel (710), determining a first pre-coding matrix (715), determining a second pre-coding matrix (720), applying the first pre-coding matrix to the first data to produce pre-coded first data (725), applying the second pre-coding matrix to the second data to produce pre-coded second data (730), generating a third signal by combining the pre-coded first data and the pre-coded second data (735) and transmitting the third signal on the first channel and on the second channel (740). Also described are a method and apparatus including transmitting a first signal (605), receiving a second signal including a first training sequence (610) and decoding the second signal by removing the first training sequence and removing the first signal (615).

The invention discloses a cooperative diversity scheme for wireless sensor networks based on the decoding and forwarding of distributed space-time codes, which comprises cluster head determination, cooperative establishment, time-slot planning and data transmission. The cooperative diversity scheme effectively solves the problems that a plurality of prior cooperative schemes such as amplify-and-forward, decode-and-forward, coded cooperation and so on have complicated design, difficult realization, low diversity efficiency, difficult cooperative synchronization and so on, effectively improves the frequency spectrum efficiency and the energy efficiency of the system, and greatly decreases the system energy consumption of the wireless sensor networks.

The invention discloses an energy harvesting relay safety transmission method adopting artificial noise precoding, which is applied to a system including four nodes that are a source, a relay, a sink and a wiretapper. The system requires two time slots to complete transmission. In the first time slot, the source broadcasts signals, the sink and the wiretapper receive the signals, and the relay adopts the maximal ratio to combine received signals, harvest energy and receives a secrecy signal. In the second time slot, the relay obtains state information of a channel from the relay to the sink, an artificial noise auxiliary precoding strategy is adopted to carry out precoding of secrecy information and artificial noise, then an amplification forwarding protocol is used for forwarding coding signals, the sink and the wiretapper receive the coding signals, and the received signals during the two time slots are combined at the maximal ratio. The relay safety transmission method applies artificial noise auxiliary precoding to an energy harvesting relay adopting power distribution, so that the remote transmission system limited in energy is enabled to have the great safety transmission performance.

The invention provides an iteration-enhanced amplifying and forwarding cooperated communication method which is mainly used for solving the problems of low frequency spectrum efficiency and high interruption probability of the existing cooperation method. The method comprises: according to the quality of service (QoS) requirement of a destination node, setting the receiving signal to noise ratio gammath of the destination node; during communication, comparing the signal to noise ratio of a received source signal with the gammath by the destination node; if the signal to noise ratio is larger than the gammath, feeding back to notify all relays to stop forwarding; otherwise, firstly selecting the front N relays with higher signal to noise ratios from the total M relays to perform forwarding, wherein each relay occupies one time slot; combining source nodes and the signals of all the forwarding relays by the destination node; comparing the total signal to noise ratio of the received signals with the gammath; if the total signal to noise ratio is larger than the gammth, feeding back to notify all the relays to stop forwarding; and otherwise, after the N relays finish forwarding, notifying the left M-N relays to forward together if the signal to noise ratio received by the destination node is still less than the gammath. By utilizing the method, the interruption probability of an audio frequency (AF) cooperation system can be lowered, and the frequency spectrum efficiency is improved.

The invention discloses a relay transmission-based cognitive network spectrum sensing method. The method comprises the steps that: (1) a relay node is set between a secondary user source node and a target node; (2) the secondary user source node sends a data signal to the relay node; and (3) the relay node receives the signal in a first stage and amplifies and forwards the signal in a second stage; and (4) the secondary user source node receives the signal in the second stage, wherein the signal sent by the secondary user source node is known, the signal of the secondary user source node is removed from the forwarded signals received by the secondary user source node, the rest signal is processed by an energy detection method, and thus, whether an authorized user signal exists can be judged. In the method, the cooperation characteristics of the secondary users are used, a relay node transmission detection method is adopted, and due to a two-stage time division transmission protocol which is regularly used in the relay transmission, the secondary user source node does not require occupy extra time for the spectrum detection, so that the performance of the system is improved.

This invention concerns distributed turbo coding and relaying protocols wireless relay networks. In particular, the invention concerns a method for relaying signals at a relay node, a method for processing signals at a destination node, a relay system and software to perform the methods. The wireless relay networks comprise a source node, a destination node and one or more relay nodes. At a relay node, the invention comprises the steps of receiving a signal from a first node; decoding the received signal; and if the received signal is decoded incorrectly, employing an Amplify-And-Forward (AAF) relaying protocol comprising the steps of amplifying the received signal and then transmitting the amplified signal to a second node; but otherwise, employing a Decode-And-Forward (DAF) relaying protocol comprising the steps of re-encoding the decoded signal and then transmitting the coded signal to the second node. At a destination node, data transmitted by the source node is recovered by combining all signals received from the source and relay nodes and then decoding the combined signal.

The invention discloses a transfer strategy realization method based on interruption performance improvement in a cellular D2D communication system. According to the method, a base station is taken as a bidirectional amplify-forward (AF) relay in the D2D system, and the base station performs normal communication with other cellular users. The concrete steps comprise that in a first time slot, a D2D user 1 sends signals to a D2D user 2 and the relay (base station) via a direct link and a relay link respectively, and the base station also receives uplink signals from the other cellular users; in a second time slot, the D2D user 2 sends signals to the D2D user 1 and the relay (base station) via the direct link and the relay link respectively, and the base station sends downlink signals to the other cellular users; and in a third time slot, the relay (base station) amplifies mixed signals received in the previous time slots and forwards the processed signals to the two D2D users. Compared with the traditional D2D communication, D2D communication provided by the invention is advantaged in that interference from the cellular users is inhibited, and the interruption performance of the system is greatly improved.

The invention relates to a relay selection method based on a threshold and maximum safe capacity criterion. According to the relay selection method, a signal source node S transmits signals to relay nodes, and the signals are forwarded to a target node D; then a set of relay nodes corresponding to the target node D with received signal-to-noise ratios which are more than a fixed signal-to-noise ratio threshold value when the signals are transmitted through a main link (S to Rk to D) is selected; an eavesdropper E also can receive the signals which are amplified and forwarded by the relay nodes; the corresponding received signal-to-noise ratio of the eavesdropper E is obtained in the candidate relay node set; the safe capacity of a whole communication system is obtained by using the received signal-to-noise ratios of the target node D and the eavesdropper E; and the relay with the maximum safe capacity is selected from the candidate relay node set. The relay selection method overcomes respective defects of two previous methods. According to the relay selection method, the communication reliability of the main link and the safety of the whole communication system are ensured, the optimum performance of the multi-relay system is played, and both the safety and reliability of the channel are covered.

The invention provides an operating method of an FSO (Free Space Optical) communication system based on an IHDAF (Incremental Hybrid Decode-Amplify-Forward) protocol, and belongs to the technical field of wireless optical communication. The FSO communication system includes a source node, a relay node and a target node and utilizes a half-duplex operating mode. The operating method of an FSO communication system based on an IHDAF protocol includes three steps: performing M-order pulse amplitude modulation on the source information; transmitting the modulated information to the relay node and the target node through a gauss laser beam, comparing the link instantaneous signal to noise ratio gamma sd from the source node to the target node and the link instantaneous signal to noise ratio gamma sr from the source node to the relay node with the signal to noise ratio threshold SNRsd and SNRsr set by the corresponding link so as to determine selecting the corresponding transmission scheme, that is, direct transmission, Decode and Forward, and Amplify and Forward; and at last, performing recovery and demodulation on the reception signal by means of the target node. The operating method of an FSO communication system based on an IHDAF protocol integrates the relay technology with the free space optical communication technology in the protocol so as to effectively restrain reduction of system performance, caused by path loss, atmospheric disturbance and aiming error and improve the transmission reliability of system.

The invention provides a relay selection and power distribution method for an amplifying-and-forwarding collaborative network. The amplifying-and-forwarding collaborative communication network is built and comprises a source node S, a destination node D and N backup relays from R1 to RN. A transmission process is divided into two phases, wherein in the first phase, signals x are broadcast to all the backup relays through the source node S; in the second phase, best relay selection and power distribution are carried out, and information is forwarded to the destination node through the selected best relay. According to the method, the source node does not need to know instant channel state information of all channels; only after the backup relays feed back instant channel state information of one hop of two hops of links where each backup relay is located, can the backup relays be selected, feedback cost is little and the method is easy to achieve.

The invention discloses a full duplex scrambling transmission method in an untrusted relay network, which is applied to a wireless communication system including three nodes of an information source, a relay and a destination node, and the relay is an untrusted relay. The method comprises the following steps: in a first time slot, transmitting information to the relay and the destination node by the information source, and receiving information source information by the destination node and transmitting an interference signal to the relay; in a second time slot, amplifying the signal received in the first time slot by the relay by adopting an amplify-and-forward protocol, after that, forwarding the signal to the destination node; performing self-interference cancellation by the destination node according to estimated channel information, and performing maximal-ratio combining on information received in the first time slot and the second time slot; and calculating the instantaneous security capacity of the system according to the received signal to noise of the relay in the first time slot and the received signal to noise of the destination node in the two time slots. The method of the invention can not only make the information source send the information to the destination node efficiently, but also make the destination node effectively interfere with the relay node to receive useful information, so as to maximize the security capacity of the system.

The invention discloses a secure transmission method based on relay strategy selection and resource allocation in a relay OFDM (Orthogonal Frequency Division Multiplexing) network. A communication system model employed by the method comprises a sending node S, N destination receiving nodes (D <1>...D <N >), an eavesdropping node Eve and K relay nodes. The method comprises the steps of for data transmission of each time, in a second time slot, after relay strategy selection and resource allocation, sending data to the relay nodes by the sending node S; and in a second time slot, selecting one of the K relay nodes as a forwarding node to forward the data received in the first time slot to the destination node D, and moreover, eavesdropping information sent to N users by the eavesdropping node Eve. Compared with traditional modes of merely employing AF (Amplify-and-Forward) or DF (Decode-and-Forward), the method has the advantages that a lower private interruption probability is obtained in a relay strategy selection mode, and the performance difference between the method and the two traditional modes is more remarkable under a high signal to noise ratio.