# US 8,787,428 B2 · Soft forwarding for cooperative wireless communication > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,787,428 B2 - Document ID: US8787428B2 - Status: Granted - Kind: B2 - Application number: 13/107,603 - Filed: 2011-05-13 - Published: 2012-06-07 - Granted: 2014-07-22 - Earliest claimed: 2010-12-01 - Assignees: Dynamic Invention LLC - Applicants: Gao Yang Dai; Wai Ho Mow - Inventors: Gao Yang Dai; Wai Ho Mow - Web page: https://patentgrep.com/patent/US8787428B2 ## CPC - H04L 1/0077: {Cooperative coding} - H04B 7/15592: {Adapting at the relay station communication parameters for supporting cooperative relaying, i.e. transmission of the same data via direct - and relayed path (cooperative diversity H04B7/024)} - H04B 7/15521: {combining by calculations packets received from different stations before transmitting the combined packets as part of network coding (network coding aspects for detection or prevention of errors in the information received H04L1/0076; network traffic management with optimizing of information sizing, e.g. header compression, by using assembly and disassembly of packets H04W28/065)} - H04L 2001/0097: {Relays} - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H04B: TRANSMISSION ## Abstract Providing for soft error decoding for wireless relay networks is described herein. By way of example, a wireless node in a wireless relay network can receive a direct signal from a source node, and can receive a forwarded version of the source signal from a relay node. An information flag included with the forwarded version is referenced to determine whether the relay node properly received the source signal. If the relay node received the source signal with an error and a destination node received the source signal with an error, soft decision information can be generated from the forwarded version of the source signal and employed to assist with decoding of the source signal at the destination node. The soft-decision information improves end-to-end performance of the wireless relay system, while mitigating complexity and bandwidth requirements for the relay node as compared with conventional signal decoding techniques. ## Claims ### Claim 1 A system, comprising: a memory to store software components of a destination node; and a processor, coupled to the memory, that executes the software components, the software components comprising: an analysis component configured to determine that a source signal is received with an error at a relay node, the source signal being forwarded by the relay node as a relay signal to a destination node; and a correction component configured to generate soft decision information from the relay signal and employ the soft decision information in decoding of the source signal, in response to reception of the source signal with the error by the destination node, and reception of the source signal with the error by at least the relay node. ### Claim 2 (depends on 1) The system of claim 1, wherein the analysis component is further configured to reference an information flag transmitted with the relay signal. ### Claim 3 (depends on 2) The system of claim 2, wherein the information flag is one bit and indicates the relay node received the source signal either correctly or with the error. ### Claim 4 (depends on 1) The system of claim 1, the software components further comprising a reference component configured to execute a cyclic redundancy check to determine whether the destination node has received the source signal with the error or the relay signal with the error. ### Claim 5 (depends on 4) The system of claim 4, wherein the reference component is further configured to output a destination error status indicating whether the source signal is received with the error and whether the relay signal is received with the error. ### Claim 6 (depends on 5) The system of claim 5, wherein the cyclic redundancy check fails for the source signal or the relay signal in response to detection of another error related to the error associated with the source signal or the relay signal in a cyclic redundancy coding of the source signal or the relay signal, respectively. ### Claim 7 (depends on 1) The system of claim 1, the software components further comprising an initialization component configured to trigger the correction component to generate the soft decision information from the relay signal in response to reception of the source signal with the error by the destination node and reception of the source signal with the error by the relay node. ### Claim 8 (depends on 1) The system of claim 1, wherein the correction component is further configured to execute a maximum ratio combining algorithm, in response to reception of the source signal with the error by the destination node, reception of the source signal correctly by the relay node, and reception of the relay signal with the error by the destination node. ### Claim 9 (depends on 1) The system of claim 1, wherein the correction component is configured to combine the source signal with the soft decision information to mitigate error in decoding of the source signal. ### Claim 10 (depends on 1) The system of claim 1, wherein the correction component is configured to generate the soft decision information from a sign function of the relay signal and a reliability function of the source signal received at the relay node. ### Claim 11 (depends on 10) The system of claim 10, wherein the sign function is generated as a function of a symbol decoded from the relay signal being re-encoded and modulated. ### Claim 12 (depends on 10) The system of claim 10, wherein the reliability function is generated from an error probability function pertaining to a bit of the source signal based on channel state information pertaining at least to a source-to-relay channel. ### Claim 13 (depends on 12) The system of claim 12, wherein the reliability function is a bit-specific reliability calculated for the bit individually. ### Claim 14 (depends on 12) The system of claim 12, wherein the reliability function is a packet-specific reliability calculated as an average of all bits of a packet in which the symbol is transmitted. ### Claim 15 (depends on 12) The system of claim 12, wherein the reliability function is a channel-specific reliability calculated as an average of all bits of packets received by the relay node from the source node in error. ### Claim 16 (depends on 12) The system of claim 12, wherein the error probability function is based on a fading coefficient and an average signal-to-noise ratio of the source-to-relay channel, and based on a fading coefficient and an average signal to noise ratio of relay-to-destination channel. ### Claim 17 (depends on 1) The system of claim 1, wherein the correction component is configured to combine the source signal with the soft decision information with an algorithm comprising a form of: L(xS|ySD,yRD)=4ySDhSD γSD+Sign{yRD}·Rel{ySR} where xs is a symbol transmitted by the source node, ySD is the symbol received at the destination node from the source node, yRD is the symbol received at the destination node from the relay node, ySR is the symbol received at the relay node from the source node, hSD is the fading coefficient of a source-to-destination channel, γSD is average signal-to-noise ratio of the source to destination channel, Sign{yRD} is defined as a modulated and coded hard-decision bit decoded from yRD, and Rel{ySR} is defined as a reliability value of ySR. ### Claim 18 (depends on 17) The system of claim 17, wherein the reliability value is derived from at least one of a bit-specific reliability function, a channel-specific reliability function or a packet-specific reliability function. ### Claim 19 (depends on 1) The system of claim 1, wherein the relay node, a source node and the destination node employ a coded cooperation mode, and further wherein: the analysis component is configured to receive a direct transmission from the relay node and a forwarded copy of the direct transmission from the source node and determine that the source node decoded the direct transmission from the relay node with the error or without the error; and the correction component is configured to generate the soft decision information from the forwarded copy of the direct transmission to mitigate error in decoding of the direct transmission. ### Claim 20 (depends on 1) The system of claim 1, wherein the correction component is configured to derive the soft decision information from the relay signal and the source signal. ### Claim 21 (depends on 20) The system of claim 20, wherein the correction component is configured to derive a reliability portion of the soft decision information from combined error probabilities of a source-to-relay channel and a relay-to-destination channel, in response to reception of the relay signal in error by the destination node. ### Claim 22 (depends on 1) The system of claim 1, wherein the relay node, a source node and the destination node form a network coded cooperation mode, and the software components further comprising: a logic component configured to separate a first set of data from a second set of data in the relay signal, the first set of data being transmitted for the destination node by the source node and received at the relay node and forwarded with the relay signal, wherein: the analysis component is configured to read an information flag bit included in the relay signal pertaining to the first set of data and determine that the first set of data had been received without error at the relay node, and the correction component is configured to use the first set of data to generate the soft decision information for the decoding of the source signal. ### Claim 23 A method, comprising: receiving, by a system comprising at least a processor, a wireless symbol from a source node and receiving a forwarded version of the wireless symbol from a relay node; determining, by the system, whether the wireless symbol is received from the source node with a first error; determining, by the system, whether the wireless symbol is received at the relay node from the source node with a second error; and generating, by the system, soft decision information from the forwarded version of the wireless symbol to mitigate decoding errors of the wireless symbol in response to determining the wireless symbol was received with the first error or the second error from the source node. ### Claim 24 (depends on 23) The method of claim 23, further comprising employing, by the system, a maximum ratio combining mechanism to decode the wireless symbol in response to determining the wireless symbol was received with the first error from by the destination node; determining, by the system, the forwarded version of the wireless symbol was received with a third error from the relay node at the destination node, and in response determining, by the system, the wireless symbol was received without error from the source node by the relay node. ### Claim 25 (depends on 23) The method of claim 23, further comprising generating, by the system, the soft decision information from a sign function and a reliability function of the forwarded version of the wireless symbol received at a destination node. ### Claim 26 (depends on 25) The method of claim 25, further comprising deriving, by the system, the sign function by decoding the forwarded version of the wireless symbol received at the destination node and re-encoding and modulating the forwarded version of the wireless symbol received at the destination node. ### Claim 27 (depends on 26) The method of claim 26, further comprising deriving, by the system, the reliability function for the forwarded version of the wireless symbol from a bit-specific, a packet-specific or a channel-specific error probability function. ### Claim 28 (depends on 27) The method of claim 27, further comprising multiplying, by the system, the sign function and the reliability function and summing a result of the multiplying with a log likelihood ratio value of the wireless symbol received from the source node. ### Claim 29 (depends on 28) The method of claim 28, further comprising determining, by the system, a value of a bit associated with the wireless symbol received from the source node from a result of the summing. ### Claim 30 A system for wireless communication, comprising: a receiver configured to receive respective wireless transmissions from a source transmitter and from a relay transmitter over a direct link and a relay link, respectively; a signal decoder configured to decode a source symbol from a first transmission received over the direct link and a relay symbol from a second transmission over the relay link; an analysis component configured to analyze the first transmission and the second transmission to identify a receive error in at least one of the respective wireless transmissions; and a correction component configured to employ the relay symbol for generating soft information for a determination of a correct value of the source symbol in response to the analysis component identifying the receive error associated with reception of the source symbol by the relay transmitter. ### Claim 31 (depends on 30) The system of claim 30, further comprising an initialization component configured to trigger the correction component to generate the soft decision information in response to the analysis component additionally identifying the receive error associated with reception of the source symbol by the system. ### Claim 32 (depends on 30) The system of claim 30, further comprising a reference component configured to execute a cyclic redundancy check to determine whether the receive error is identified with the first transmission or is identified with the second transmission. ### Claim 33 A system for wireless communication, comprising: means for receiving a wireless symbol from a source node and a forwarded version of the wireless symbol from a relay node; means for determining that the system receives the wireless symbol with a first error; means for determining that the relay node receives the wireless symbol with a second error; and means for generating soft decision information from the forwarded version of the wireless symbol in response to the system receiving the wireless symbol with the first error and the relay node receiving the wireless symbol with the second error. ### Claim 34 (depends on 33) The system of claim 33, wherein a cyclic redundancy check is employed at least in part for determining that the system receives the wireless symbol with the first error or for determining that the relay node receives the wireless symbol with the second error. ### Claim 35 (depends on 33) The system of claim 33, wherein a destination error status is output indicating whether the system receives the wireless symbol with the first error and whether the relay node receives the wireless symbol with the second error.