# US 9,521,557 B2 · Methods and apparatus for clear channel assessment > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,521,557 B2 - Document ID: US9521557B2 - Status: Granted - Kind: B2 - Application number: 14/290,899 - Filed: 2014-05-29 - Published: 2014-12-04 - Granted: 2016-12-13 - Earliest claimed: 2013-06-03 - Assignees: QUALCOMM Incorporated - Applicants: QUALCOMM Incorporated - Inventors: Sameer Vermani; Simone Merlin; Eugene Jong-Hyon Baik; Bin Tian; Tevfik Yucek - Web page: https://patentgrep.com/patent/US9521557B2 ## CPC - H04W 16/14: Spectrum sharing arrangements {between different networks} - H04L 27/0006: {Assessment of spectral gaps suitable for allocating digitally modulated signals, e.g. for carrier allocation in cognitive radio (for spectrum sharing between different networks H04W16/14)} - H04L 27/2601: {Multicarrier modulation systems} - H04W 72/0446: Resources in time domain, e.g. slots or frames - H04W 72/0453: Resources in frequency domain, e.g. a carrier in FDMA - H04W 74/0816: with collision avoidance - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract One aspect disclosed is a method in a wireless communications system including a first primary channel having a first frequency spectrum bandwidth and a second primary channel having a second frequency spectrum bandwidth, wherein the second frequency spectrum bandwidth includes the first frequency spectrum bandwidth. The method includes performing a first and a second back-off procedure at least partially in parallel, the first back-off procedure based on whether the first primary channel is idle, and the second back-off procedure based on whether the second primary channel is idle, and transmitting a wireless message based on whether the first or the second back-off procedure completes first. ## Claims ### Claim 1 A method in a wireless communications system including a first primary channel having a first frequency spectrum and a second primary channel having a second frequency spectrum, wherein the second frequency spectrum includes the first frequency spectrum, comprising: performing, by a wireless device, a first and a second back-off procedure at least partially in parallel, each of the first and second back-off procedures conditionally update separate counters over individual periods of time when the first or second primary channels are idle respectively, conditionally reset the separate counters over the individual periods of time when the first or second primary channels are busy respectively, wherein the first and second back-off procedures are each complete when their respective counters reach a respective predetermined threshold value, wherein the second primary channel is not idle when the first primary channel is not idle; transmitting a wireless message over the first primary channel in response to the first back-off procedure completing before the second back-off procedure; and transmitting the wireless message over the second primary channel in response to the second back-off procedure completing before the first back-off procedure. ### Claim 2 (depends on 1) The method of claim 1, further comprising determining whether one or more secondary channels with frequency spectrums within the second frequency spectrum are idle for a PCF Inter-frame Space (PIFS) time period before the transmission of the wireless message, wherein the transmitting of the wireless message is further based on the determining. ### Claim 3 (depends on 2) The method of claim 2, wherein the one or more secondary channels comprise a two megahertz channel, a four megahertz channel, and an eight megahertz channel. ### Claim 4 (depends on 3) The method of claim 3, further comprising transmitting the wireless message without utilizing the secondary channels if an amount of data waiting for transmission is below a data size threshold. ### Claim 5 (depends on 3) The method of claim 3, further comprising transmitting the wireless message on one of the secondary channels if the secondary channel is idle PCF Inter-frame Space (PIFS) time before the transmission and the amount of data waiting for transmission is above the data size threshold. ### Claim 6 (depends on 1) The method of claim 1, further comprising determining whether the first primary channel is idle, wherein the determining comprises: determining whether a preamble has been detected on the first primary channel during a first period of time; and determining whether a guard interval has been detected on the first primary channel during a second period of time. ### Claim 7 (depends on 1) The method of claim 1, further comprising transmitting the wireless message on the first primary channel if the first back-off procedure completes before the second back-off procedure. ### Claim 8 (depends on 7) The method of claim 7, further comprising transmitting the wireless message on the second primary channel if the second back-off procedure completes first. ### Claim 9 (depends on 1) The method of claim 1, wherein determining whether the second primary channel is idle comprises: determining whether a first preamble has been detected on the second primary channel during a first threshold period of time; determining whether a second preamble has been detected on the first primary channel during a second threshold period of time; determining whether a guard interval has been detected on the second primary channel during a third threshold period of time; and determining whether the second primary channel is idle based at least in part on detection of the first preamble, the second preamble and the guard interval. ### Claim 10 (depends on 1) The method of claim 1, wherein the second back-off procedure determines the second primary channel is not idle if a preamble is detected on the first primary channel. ### Claim 11 A device in a wireless communications system including a first primary channel having a first frequency spectrum and a second primary channel having a second frequency spectrum, wherein the second frequency spectrum includes the first frequency spectrum, comprising: a hardware processor configured to: perform a first and a second back-off procedure at least partially in parallel, each of the first and second back-off procedures conditionally update separate counters over individual periods of time when the first or second primary channels are idle respectively, conditionally reset the separate counters over the individual periods of time when the first or second primary channels are busy respectively, wherein the first and second back-off procedures are each complete when their respective counters reach a respective predetermined threshold value, wherein the second primary channel is not idle when the first primary channel is not idle; and a transmitter configured to transmit a wireless message over the first primary channel in response to the first back-off procedure completing before the second back-off procedure; and transmit the wireless message over the second primary channel in response to the second back-off procedure completing before the first back-off procedure. ### Claim 12 (depends on 11) The device of claim 11, wherein the hardware processor is further configured to determine whether one or more secondary channels with frequency spectrums within the second frequency spectrum are idle for a PCF Inter-frame Space (PIFS) time period before the transmission of the wireless message, and wherein the transmitter is further configured to transmit the wireless message is further based on the determining. ### Claim 13 (depends on 12) The device of claim 12, wherein the one or more secondary channels comprise a two megahertz channel, a four megahertz channel, and an eight megahertz channel. ### Claim 14 (depends on 13) The device of claim 13, wherein the transmitter is further configured to not utilize the secondary channels for transmission of the wireless message if an amount of data waiting for transmission is below a data size threshold. ### Claim 15 (depends on 13) The device of claim 13, wherein the transmitter is configured to transmit the wireless message on one of the secondary channels if the secondary channel is idle PCF Inter-frame Space (PIFS) time before the transmission and the amount of data waiting for transmission is above the data size threshold. ### Claim 16 (depends on 11) The device of claim 11, wherein the hardware processor is configured to determine whether the first primary channel is idle by: determining whether a preamble has been detected on the first primary channel during a first period of time; determining whether a guard interval has been detected on the first primary channel during a second period of time; and determining whether the first primary channel is idle based at least in part on detection of the preamble and the guard interval. ### Claim 17 (depends on 11) The device of claim 11, wherein the transmitter is configured to transmit the wireless message on the first primary channel when the first back-off procedure completes before the second back-off procedure. ### Claim 18 (depends on 17) The device of claim 17, wherein the transmitter is configured to transmit the wireless message on the second primary channel when the second back-off procedure completes before the first back-off procedure. ### Claim 19 (depends on 11) The device of claim 11, wherein the hardware processor is configured to determine whether the second primary channel is idle by: determining whether a first preamble has been detected on the second primary channel during a first threshold period of time; determining whether a second preamble has been detected on the first primary channel during a second threshold period of time; determining whether a guard interval has been detected on the second primary channel during a third threshold period of time; and determining whether the second primary channel is idle based at least in part on detection of the first preamble, the second preamble and the guard interval. ### Claim 20 A device in a wireless communications system including a first primary channel having a first frequency spectrum and a second primary channel having a second frequency spectrum, wherein the second frequency spectrum includes the first frequency spectrum, comprising: means for performing a first and a second back-off procedure at least partially in parallel, each of the first and second back-off procedures conditionally update separate counters over individual periods of time when the first or second primary channels are idle respectively, conditionally reset the separate counters over the individual periods of time when the first or second primary channels are busy respectively, wherein the first and second back-off procedures are each complete when their respective counters reach a respective predetermined threshold value, wherein the second primary channel is not idle when the first primary channel is not idle; means for transmitting a wireless message over the first primary channel in response to the first back-off procedure completing before the second back-off procedure; and means for transmitting the wireless message over the second primary channel in response to the second back-off procedure completing before the first back-off procedure. ### Claim 21 (depends on 20) The device of claim 20, further comprising means for determining whether one or more secondary channels with frequency spectrums within the second frequency spectrum are idle for a PCF Inter-frame Space (PIFS) time period before the means for transmitting transmits the wireless message, wherein the means for transmitting the wireless message is configured to transmit the message based on whether the one or more secondary channels are idle for a PCF Inter-frame Space (PIFS) time period before transmission of the wireless message. ### Claim 22 (depends on 21) The device of claim 21, wherein the one or more secondary channels comprise a two megahertz channel, a four megahertz channel, and an eight megahertz channel. ### Claim 23 (depends on 22) The device of claim 22, wherein the means for transmitting is configured to utilize one of the secondary channels if an amount of data waiting for transmission is below a data size threshold. ### Claim 24 (depends on 20) The device of claim 20, wherein the means for determining is configured to determine whether the first primary channel is idle by: determining whether a preamble has been detected on the first primary channel during a first period of time; determining whether a guard interval has been detected on the first primary channel during a second period of time; and determining whether the first primary channel is idle based at least in part on detection of the preamble and the guard interval. ### Claim 25 (depends on 20) The device of claim 20, wherein the means for transmitting the wireless message is configured to transmit the wireless message on the first primary channel if the first back-off procedure completes before the second back-off procedure. ### Claim 26 (depends on 25) The device of claim 25, wherein means for transmitting the wireless message is configured to transmit the message on the second primary channel when the second back-off procedure completes before the first back-off procedure. ### Claim 27 (depends on 20) The device of claim 20, wherein the means for performing the first and second back-off procedure is configured to determine whether the second primary channel is idle by: determining whether a first preamble has been detected on the second primary channel during a first threshold period of time; determining whether a second preamble has been detected on the first primary channel during a second threshold period of time; determining whether a guard interval has been detected on the second primary channel during a third threshold period of time; and determining whether the second primary channel is idle based at least in part on detection of the first preamble, the second preamble and the guard interval. ### Claim 28 A non-transitory computer readable storage medium comprising instructions that when executed cause one or more hardware processors to perform a method in a wireless communications system including a first primary channel having a first frequency spectrum and a second primary channel having a second frequency spectrum, wherein the second frequency spectrum includes the first frequency spectrum, the method comprising: performing, by a wireless device, a first and a second back-off procedure at least partially in parallel, each of the first and second back-off procedures conditionally update separate counters over individual periods of time when the first or second primary channels are idle respectively, conditionally reset the separate counters over the individual periods of time when the first or second primary channels are busy respectively, wherein the first and second back-off procedures are each complete when their respective counters reach a respective predetermined threshold value, wherein the second primary channel is not idle when the first primary channel is not idle; transmitting a wireless message over the first primary channel in response to the first back-off procedure completing before the second back-off procedure; and transmitting the wireless message over the second primary channel in response to the second back-off procedure completing before the first back-off procedure.