# US 9,438,382 B2 · Variable response interframe space in communication systems > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,438,382 B2 - Document ID: US9438382B2 - Status: Granted - Kind: B2 - Application number: 14/085,583 - Filed: 2013-11-20 - Published: 2015-05-21 - Granted: 2016-09-06 - Earliest claimed: 2013-11-20 - Assignees: QUALCOMM Incorporated - Applicants: QUALCOMM Incorporated - Inventors: Srinivas Katar; Lawrence Winston Yonge, III - Web page: https://patentgrep.com/patent/US9438382B2 ## CPC - H04L 1/1607: Details of the supervisory signal - H04L 1/0042: {Encoding specially adapted to other signal generation operation, e.g. in order to reduce transmit distortions, jitter, or to improve signal shape (H04L1/0067 takes precedence)} - H04L 1/1628: {List acknowledgements, i.e. the acknowledgement message consisting of a list of identifiers, e.g. of sequence numbers (H04L1/1614 takes precedence)} - H04L 1/1854: {Scheduling and prioritising arrangements} - H04L 5/0053: {Allocation of signalling, i.e. of overhead other than pilot signals} - H04L 5/0091: {Signalling for the administration of the divided path, e.g. signalling of configuration information} - H04L 12/413: with random access, e.g. carrier-sense multiple-access with collision detection [CSMA-CD] - H04W 28/06: Optimizing {the usage of the radio link}, e.g. header compression, information sizing {, discarding information (system modifying transmission characteristic according to link quality by modifying frame length H04L1/0007; dynamic adaptation of the packet size for flow control or congestion control H04L47/365)} - H04W 84/12: WLAN [Wireless Local Area Networks] - H04L 1/0003: {by switching between different modulation schemes} - H04L 5/0007: {the frequencies being orthogonal, e.g. OFDM(A) or DMT} - H04L 25/0202: {Channel estimation} - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) ## Abstract A Response Interframe Space (RIFS) time period may be adapted in a communication system. The RIFS time period may be based, at least in part, on channel conditions (e.g., data rate) between a first device and a second device. The RIFS may be optimized in consideration of channel conditions for a particular communications channel and/or characteristics of a particular physical layer transmission. In one embodiment, the RIFS may be dependent on characteristics of a final modulation symbol in a physical layer transmission. The final modulation symbol may include more than one PHY blocks (PBs) or portions of PBs. The RIFS may depend on a number of PBs that end in the final modulation symbol. ## Claims ### Claim 1 A method comprising: sending a first configuration message via a communications medium, the first configuration message indicating a maximum quantity of physical layer (PHY) blocks that can be included in a final modulation symbol associated with a PHY protocol data unit (PPDU); receiving, via the communications medium, the PPDU that includes multiple PHY blocks, the PPDU received as a series of modulation symbols; determining a response interframe space (RIFS) time period based, at least in part, on a quantity of PHY blocks that end in the final modulation symbol of the PPDU; and sending, via the communications medium, an acknowledgment message responsive to receiving the PPDU after the RIFS time period following the final modulation symbol. ### Claim 2 (depends on 1) The method of claim 1, wherein the RIFS time period is based, at least in part, on a processing time associated with decoding the quantity of PHY blocks that end in the final modulation symbol. ### Claim 3 (depends on 1) The method of claim 1, wherein the quantity of PHY blocks that end in the final modulation symbol is based at least in part on channel conditions of the communications medium. ### Claim 4 (depends on 3) The method of claim 3, wherein the PPDU is received from a first device, and wherein the channel conditions comprise at least one of a data rate, an error rate, or a signal quality associated with prior transmissions received from the first device. ### Claim 5 (depends on 3) The method of claim 3, further comprising: estimating the quantity of PHY blocks that will end in the final modulation symbol based at least in part on the channel conditions of the communications medium. ### Claim 6 (depends on 5) The method of claim 5, wherein the RIFS time period is determined prior to receiving the PPDU. ### Claim 7 (depends on 1) The method of claim 1, further comprising: determining a plurality of RIFS time periods including a first RIFS time period for use when one PHY block ends in the final modulation symbol and at least one other RIFS time period for use when more than one PHY block ends in the final modulation symbol. ### Claim 8 (depends on 7) The method of claim 7, further comprising: sending a second configuration message to a transmitting device, wherein the second configuration message indicates the plurality of RIFS time periods. ### Claim 9 (depends on 8) The method of claim 8, wherein the second configuration message comprises a management message or a tone map message. ### Claim 10 (depends on 1) The method of claim 1, wherein the RIFS time period is further based, at least in part, on a size of the PPDU and a quantity of modulation symbols associated with the size of the PPDU. ### Claim 11 (depends on 1) The method of claim 1, wherein the acknowledgment message is a selective acknowledgment (SACK) message that indicates whether one or more PHY blocks of the PPDU were properly decoded. ### Claim 12 (depends on 1) The method of claim 1, wherein the communications medium is one of a wireless communications channel, a power line communications medium, or a mobile telecommunications wireless medium. ### Claim 13 (depends on 1) The method of claim 1, wherein the series of modulation symbols comprises orthogonal frequency division multiplexing (OFDM) symbols. ### Claim 14 An apparatus comprising: a receiver for coupling to a communications medium, the receiver configured to: send a first configuration message via the communications medium, the first configuration message indicating a maximum quantity of physical layer (PHY) blocks that can be included in a final modulation symbol associated with a PHY protocol data unit (PPDU), and receive, via the communications medium, the PPDU that includes multiple PHY blocks, the PPDU received as a series of modulation symbols; a response interframe space (RIFS) determination module configured to determine a RIFS time period based, at least in part, on a quantity of PHY blocks that end in the final modulation symbol of the PPDU; and a transmitter configured to send an acknowledgment message responsive to receiving the PPDU after the RIFS time period following the final modulation symbol. ### Claim 15 (depends on 14) The apparatus of claim 14, wherein the RIFS time period is based, at least in part, on a processing time associated with decoding the quantity of PHY blocks that end in the final modulation symbol. ### Claim 16 (depends on 14) The apparatus of claim 14, further comprising: a PHY controller configured to estimate the quantity of PHY blocks that will end in the final modulation symbol based at least in part on channel conditions of the communications medium. ### Claim 17 (depends on 14) The apparatus of claim 14, further comprising: the RIFS determination module further configured to determine a plurality of RIFS time periods including a first RIFS time period for use when one PHY block ends in the final modulation symbol and at least one other RIFS time period for use when more than one PHY block ends in the final modulation symbol. ### Claim 18 (depends on 17) The apparatus of claim 17, further comprising: a PHY controller configured to send a second configuration message via the transmitter, wherein the second configuration message indicates the plurality of RIFS time periods. ### Claim 19 (depends on 14) The apparatus of claim 14, wherein the RIFS time period is further based, at least in part, on a size of the PPDU and a quantity of modulation symbols associated with the size of the PPDU. ### Claim 20 A non-transitory computer readable medium storing instructions which, when executed by one or more processors of a device, cause the device to: send a first configuration message via a communications medium, the first configuration message indicating a maximum quantity of physical layer (PHY) blocks that can be included in a final modulation symbol associated with a PHY protocol data unit (PPDU); receive, via the communications medium, the PPDU that includes multiple PHY blocks, the PPDU received as a series of modulation symbols; determine a response interframe space (RIFS) time period based, at least in part, on a quantity of PHY blocks that end in the final modulation symbol of the PPDU; and send, via the communications medium, an acknowledgment message responsive to receiving the PPDU after the RIFS time period following the final modulation symbol. ### Claim 21 (depends on 20) The non-transitory computer readable medium of claim 20, storing further instructions which, when executed by the one or more processors of the device, cause the device to: determine the RIFS time period based, at least in part, on a processing time associated with decoding the quantity of PHY blocks that end in the final modulation symbol. ### Claim 22 (depends on 20) The non-transitory computer readable medium of claim 20, storing further instructions which, when executed by the one or more processors of the device, cause the device to: estimate the quantity of PHY blocks that will end in the final modulation symbol based at least in part on channel conditions of the communications medium. ### Claim 23 (depends on 20) The non-transitory computer readable medium of claim 20, storing further instructions which, when executed by the one or more processors of the device, cause the device to: determine a plurality of RIFS time periods including a first RIFS time period for use when one PHY block ends in the final modulation symbol and at least one other RIFS time period for use when more than one PHY block ends in the final modulation symbol. ### Claim 24 (depends on 23) The non-transitory computer readable medium of claim 23, storing further instructions which, when executed by the one or more processors of the device, cause the device to: send a second configuration message via the communications medium, wherein the second configuration message indicates the plurality of RIFS time periods. ### Claim 25 A communication device comprising: means for sending a first configuration message via a communications medium, the first configuration message indicating a maximum quantity of physical layer (PHY) blocks that can be included in a final modulation symbol associated with a PHY protocol data unit (PPDU); means for receiving, via the communications medium, the PPDU that includes multiple PHY blocks, the PPDU received as a series of modulation symbols; means for determining a response interframe space (RIFS) time period based, at least in part, on a quantity of PHY blocks that end in the final modulation symbol of the PPDU; and means for sending, via the communications medium, an acknowledgment message responsive to receiving the PPDU after the RIFS time period following the final modulation symbol. ### Claim 26 (depends on 25) The communication device of claim 25, further comprising: means for determining the RIFS time period based, at least in part, on a processing time associated with decoding the quantity of PHY blocks that end in the final modulation symbol. ### Claim 27 (depends on 25) The communication device of claim 25, further comprising: means for determining a plurality of RIFS time periods including a first RIFS time period for use when one PHY block ends in the final modulation symbol and at least one other RIFS time period for use when more than one PHY block ends in the final modulation symbol. ### Claim 28 (depends on 27) The communication device of claim 27, further comprising: means for sending a second configuration message via the communications medium, wherein the second configuration message indicates the plurality of RIFS time periods.