112 results about "Decode and forward" patented technology

A system and method of relay code design and factor graph decoding using a forward and a backward decoding scheme. The backward decoding scheme exploits the idea of the analytical decode-and-forward coding protocol and hence has good performance when the relay node is located relatively close to the source node. The forward decoding scheme exploits the idea of the analytical estimate-and-forward protocol and hence has good performance when the relay node is located relatively far from the source node. The optimal decoding factor graph is first broken into partial factor graphs and then solved iteratively using either the forward or backward decoding schemes.

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.

Digital communication coding methods resulting in rate-compatible low density parity-check (LDPC) codes built from protographs. Described digital coding methods start with a desired code rate and a selection of the numbers of variable nodes and check nodes to be used in the protograph. Constraints may be set to satisfy a linear minimum distance growth property for the protograph. All possible edges in the graph are searched for the minimum iterative decoding threshold and the protograph with the lowest iterative decoding threshold is selected. Protographs designed in this manner may be used in decode and forward relay channels.

A method and apparatus for controlling power in a decode-and-forward (DF) relay system is provided. The method of controlling power in a DF relay system includes: acquiring first channel information of a first link between a source node and a destination node, second channel information of a second link between the source node and a relay node, and third channel information of a third link between the relay node and the destination node, by using a pilot signal; determining a power level of the source node from the acquired first through third channel information; and feeding back the determined power level to the source node and the relay node.

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.

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 an LDPC code constructing method based on coding cooperative communication; the method comprises the following steps: 1. choose a basis matrix W (1) based on finite field multiplicative inverse; the multiplicative inverse of a certain element in the basis matrix is multiplied with each row of the basis matrix, so as to generate a multiplicative identity in the basis matrix; 3.the basis matrix is expanded, so as to obtain an expansion matrix containing diagonal line; 4. the submatrix above the diagonal line is substituted by zero matrix, so as to obtain a quasi-cyclic matrix which is provided with a lower triangular type and has a nested structure; the invention can flexibly construct the quasi-cyclic matrix with the nested structure, which is suitable for CC proposal, while reducing the code construction complexity, the complexity of a coder of a trunk node and a destination node is reduced; in addition, the code in the invention does not have short link characteristic, and the performance of the code is promoted obviously compared with the traditional decode and forward, DF proposal.

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 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.

The invention relates to a method and system for transmitting signals in a wireless relay network. The method and system enable two potentials, which can be offered by wireless relay systems, i.e. diversity gains and attenuation savings, to be exploited simultaneously. The inventive method is characterized in that a relay mounted between the source and the destination decides, independently from information relating to other components of the networks, whether a signal received from the source or from at least one other relay is to be decoded and forwarded. The system is characterized in that the relay comprises a decision unit for the signal decoding and forwarding decision.

The invention relates to a visible light communication system and method based on probabilistic shaping coding, and application equipment, and relates to the field of light communication systems. Bitsof input data are grouped at a sending end, and mapped into new bits according to the set probability; then, forward error correction coding is carried out; the coded data forms an OFDM frame; then,a data flow is formed and sent; and a receiving end receives the data flow from the sending end, recovers the OFDM frame, performs inverse mapping on the decoded data after performing OFDM frame decoding and forward error correction decoding, and recovers the original data bits by using a probability mapping rule corresponding to the sending end. Due to addition of probability mapping, the net information rate of the system can be adjusted; the communication capability of the system can be increased; adjustment is carried out flexibly; and furthermore, the complexity is relatively low.

A method of performing coordinated communication by a relay station is provided. The method includes: receiving a signal from a terminal; measuring channel state information (CSI) indicating a state of a channel which receives the signal; comparing the CSI with a predetermined threshold to determine whether to decode the received signal; and if it is determined to decode the received signal, removing noise by decoding the received signal, and then performing decode and forward (DAF) in which the signal is re-encoded and transmitted to a base station, and if it is determined not to decode the received signal, performing amplify and forward (AAF) in which the received signal is amplified and forwarded to the base station. The CSI may be at least one of a frame error rate (FER), a bit error rate (BER), a signal to noise ratio (SNR), and a signal to interference plus noise ratio (SINR). Accordingly, a time delay consumed for channel decoding in hybrid DAF coordinated communication can be decreased, data transmission and resource usage can be more effectively achieved in coordinated communication using multiple terminals, and unnecessary power consumption can be decreased.

The invention discloses a wireless power supply relay network optimization method of non-orthogonal multiple access. The method comprises an energy collection stage and an information transmission stage. On the basis of a traditional double-hop wireless power supply relay network system, a user transmits information to relays in a time division multiple access mode, after the information is decoded and forwarded by the relays, all the relays send information to a base station in a non-orthogonal multiple access mode at the same time, the spectrum utilization rate is improved, and meanwhile thetotal transmission rate of the whole network is increased.

The invention discloses a power allocation method of a cognitive decode-and-forward relay system, and belongs to the technical field of wireless communication. The actual situation that channel state information between a secondary user and a primary user is difficult to accurately acquire is considered, and the interference power constraint conditions of a secondary user transmitter on the primary user determined according to statistical information between the secondary user and the primary user under the condition that the channel state is unknown and the interference power constraint conditions of a relay on the primary user determined according to statistical information between the relay and the primary user are introduced in the process of optimizing the power allocation scheme in the cognitive decode-and-forward relay system. Firstly equivalent transformation of statistics of the interference constraint conditions is performed and then an original optimization problem is converted into an equivalent convex optimization problem by introducing variables. With application of the method, relatively high system energy efficiency can be acquired under the condition of guaranteeing communication quality of the primary user.

The invention provides a decode-and-forward strategy based multi-antenna relay beam forming method which includes the steps: in the first time slot, obtaining a beam forming vector of a signal source node S, enabling the signal source node S to send signals s1 to a relay node R and a destination node D simultaneously, and enabling the relay node R and the destination node D to receive the signals s1 simultaneously; and in the second time slot, enabling the relay node R to receive and decode the signals s1, recoding information to signals s2 and sending the signals s2 to the destination node D. By the decode-and-forward strategy based multi-antenna relay beam forming method, the design that the beam forming vector of the signal source node S is obtained in the first time slot is provided, so that transmission efficiency is maximized, and channel interrupt probability is minimized; and the relay technology and the multi-antenna beam forming technology are combined together, the optimal beam forming vector is designed, and accordingly transmission efficiency and reliability can be improved, and transmitting power is saved.

The invention provides a full-duplex and half-duplex mixed relay implementing method based on diversity gain. The method comprises steps as follows: step 1, estimating channel state information; step 2, selecting a transceiving mode of an antenna; step 3, calculating signal-to-interference and noise ratios of different links according to obtained parameters; step 4, calculating a signal-to-interference and noise ratio under an amplify-and-forward protocol and a decode-and-forward protocol in a full-duplex mode; step 5, calculating system capacity in the full-duplex mode; step 6, calculating link signal-to-interference and noise ratios in a half-duplex mode according to the channel state information obtained through estimation; step 7, calculating system signal-to-interference and noise ratio under the amplify-and-forward protocol and the decode-and-forward protocol in the half-duplex mode; step 8, calculating reachable capacity in the half-duplex mode; step 9, selecting an optimal working mode according to instantaneous spectrum effectiveness. According to the method, all hardware resources can be utilized, and performance is improved, that is, maximization of a transmission rate from a source node to a target node is realized.

User cooperation is an emerging transmission framework where users act as relays of each other to provide extra diversity paths for better overall performance. In various embodiments, systems and methods for transmitting data from a basestation to a mobile device in an adaptive communications network including user cooperation are provided. Among various embodiments, relaying is performed according to a time division duplex (TDD) system according to either a downlink-assisted relaying (DAR) which performs a relaying operation in a defined supplemental downlink timeslot or according to an uplink-assisted relaying (UAR) which performs a relaying operation in a defined supplemental uplink timeslot. Among other embodiments, relay transmissions according to a max-throughput scheduling algorithm which achieves a maximum system throughput without imposing any fairness constraints on users or according to a round-robin scheduling algorithm which achieves absolute fairness in terms of delays among the considered users. The downlink throughput is optimized from the basestation to the mobile device utilizing either amplify-and-forward (AF) or decode-and-forward (DF) cooperation protocols.

The bandwidth efficient cooperative two-way amplify-and-forward relaying method allows users in a secondary network to utilize a relay node in the primary users' network while minimizing co-channel interference. In the method, two primary user network sources communicate through a primary user network relay node. A secondary user network source and a secondary user destination agree to act as relays for the primary network sources, all of the above using amplify-and-forward protocol. In return, the primary network relay node allows the secondary user source to communicate through the primary network relay node with the secondary user destination using decode-and-forward protocol. Five symbols, including four primary user symbols and one secondary user symbol, are transmitted in four time slots for a bandwidth efficiency of 1.25. The primary network relay and the secondary users relay transmissions have their power allocated to minimize symbol error rate and maximize sum rate.

A method of communication comprising: at time=t: a first multiple antenna relay node decoding and forwarding a first STBC coded signal from a source node, and a first decoded and forwarded STBC signal from a second multiple antenna relay node, and a destination DSTTD receiver decoding the first STBC coded signal from the source node, and the first decoded and forwarded STBC signal from the second multiple antenna relay node; at time=t+1: the second multiple antenna relay node receiving a second STBC coded signal from the source node, and a second decoded and forwarded signal from the first multiple antenna relay node, and the destination DSTTD receiver decoding the second STBC coded signal from the source node, and the second decoded and forwarded signal from the first multiple antenna relay node.

The present invention discloses a network code (NC) centralized control method in a software-defined FiWi network. On the basis of providing a novel software-defined FiWi network architecture having the network coding function, the network coding function of a flow table is expanded, and the coding of the network is centralized in a controller. Therefore, the controller is capable of controlling the screening of source code packets and the queue length of an encoding pack. Based on the openflow protocol, the deployment of a network encoding strategy is realized. In this way, the number of control messages in the network is reduced and data packets can be quickly coded, decoded and forwarded. Therefore, the utilization rate of network bandwidth is improved and the network coding efficiency is increased. The network transmission delay is lowered.