# US 9,521,559 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 9,521,559 B2 - Document ID: US9521559B2 - Status: Granted - Kind: B2 - Application number: 14/873,117 - Filed: 2015-10-01 - Published: 2016-01-28 - 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/US9521559B2 ## 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 Methods and systems disclosed provide for clear channel assessment of first and second communication channels. In one aspect, a first primary channel has a first frequency spectrum bandwidth and a second primary channel has a second frequency spectrum bandwidth including the first frequency spectrum bandwidth. A method may include performing a first back-off procedure based on whether the first primary channel is idle if a transmission bandwidth for a wireless message is the first frequency spectrum bandwidth, performing a second back-off procedure based on whether the second primary channel is idle if the transmission bandwidth for the wireless message is greater than the first frequency spectrum bandwidth, and transmitting the wireless message based on a completion of the performed back off procedure. ## 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, and secondary channels are associated with the second primary channel but not with the first primary channel, comprising: determining whether to transmit a wireless message over the first primary channel based on a property of the wireless message; in response to determining the wireless message is to be transmitted over the first primary channel: determining whether the first primary channel is idle based, at least in part, on whether a preamble is detected on the second primary channel; performing a first back-off procedure based on the determination and transmitting the wireless message over the first primary channel when the first back-off procedure completes, wherein the transmission is restricted to the first frequency spectrum, and in response to determining the wireless message is to be transmitted over a channel different than the first primary channel; second determining whether the second primary channel is idle based, at least in part, on whether a preamble is detected on the first primary channel, performing a second back-off procedure based on the second determination, determining whether one or more of the secondary channels associated with the second primary channel are idle for a PCT Inter-frame Space (PIFS) time period before a transmission of the wireless message, and transmitting the wireless message over the second primary channel and the determined idle secondary channels based on a completion of the second back-off procedure. ### Claim 2 (depends on 1) The method of claim 1, wherein the determining of whether to transmit the wireless message over the first primary channel is based on whether an amount of data waiting for transmission is above a threshold. ### Claim 3 (depends on 1) The method of claim 1, wherein the one or more secondary channels associated with the second primary channel comprise a two megahertz secondary channel, a four megahertz secondary channel, and an eight megahertz secondary channel. ### Claim 4 (depends on 2) The method of claim 2, further comprising determining to transmit the wireless message on the second primary channel without use of the associated secondary channels if no secondary channels are idle for the PCF Inter-frame space (PIFS) time period when the second back-off procedure is complete. ### Claim 5 An apparatus 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, and secondary channels are associated with the second primary channel but not with the first primary channel comprising: a processor configured to: determine whether to transmit a wireless message over the first primary channel based on a property of the wireless message; in response to determining the wireless message is transmitted over the first primary channel: determine whether the first primary channel is idle based, at least in part, on whether a preamble is detected on the second primary channel, perform a first back-off procedure based on the determination; in response to determining the wireless message is transmitted over a channel different than the first primary channel; second determine whether the second primary channel is idle based, at least in part, on whether a preamble is detected on the first primary channel, perform a second back-off procedure based on the second determination, and determine whether one or more of the secondary channels associated with the second primary channel are idle for a PCT Inter-frame Space (PIFS) time period before a transmission of the wireless message; a transmitter configured to: transmit the wireless message over the first primary channel is response to completion of the first back-off procedure, wherein the transmission is restricted to the first frequency spectrum, and transmit the wireless message over the second primary channel and the determined idle secondary channels in response to completion of the second back-off procedure. ### Claim 6 (depends on 5) The apparatus of claim 5, wherein the processor is further configured to determine whether to transmit the wireless message over the first primary channel based on whether an amount of data waiting for transmission is above a threshold. ### Claim 7 (depends on 5) The apparatus of claim 5, wherein the one or more secondary channels comprise a two megahertz secondary channel, a four megahertz secondary channel, and an eight megahertz secondary channel. ### Claim 8 (depends on 6) The apparatus of claim 6, wherein the transmitter is configured to transmit the wireless message on the second primary channel without use of the associated secondary channels if no secondary channels are idle for the PCF Inter-frame space (PIFS) time period when the second back-off procedure is complete. ### Claim 9 An apparatus 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 bandwidth includes the first frequency spectrum and secondary channels are associated with the second primary channel but not with the first primary channel, comprising: means for determining whether to transmit a wireless message over the first primary channel based on a property of the wireless message; means for determining whether the first primary channel is idle based, at least in part, on whether a preamble is detected on the second primary channel; means for performing a first back-off procedure based on whether the first primary channel is idle in response to the means for determining the wireless message is to be transmitted over the first primary channel; means for determining whether the second primary channel is idle based, at least in part, on whether a preamble is detected on the first primary channel; means for performing a second back-off procedure based on whether the second primary channel is idle in response to the means for determining the wireless message is to be transmitted over a channel different than the first primary channel; means for determining whether one or more of the secondary channels associated with the second primary channel are idle for a PCT Inter-frame Space (PIFS) time period before a transmission of the wireless message over the second primary channel; means for transmitting the wireless message over the first primary channel based on a completion of the first back-off procedure, wherein the transmission is restricted to the first frequency spectrum; and means for transmitting the wireless message over the second primary channel and the determined idle secondary channels based on a completion of the second back-off procedure in response to the means for determining that the wireless message is to be transmitted over at least the second primary channel. ### Claim 10 (depends on 9) The apparatus of claim 9, wherein the means for determining is configured to determine whether to transmit the wireless message on the first primary channel based on whether an amount of data waiting for transmission is above a threshold. ### Claim 11 (depends on 9) The apparatus of claim 9, wherein the one or more secondary channels comprise a two megahertz secondary channel, a four megahertz secondary channel, and an eight megahertz secondary channel. ### Claim 12 (depends on 10) The apparatus of claim 10, wherein the means for transmitting is configured to the wireless message on the second primary channel without use of the associated secondary channels if no secondary channels are idle for the PCF Inter-frame space (PIFS) time period when the second back-off procedure is complete. ### Claim 13 A non-transitory computer readable storage medium comprising instructions that when executed cause a processor 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 bandwidth, and secondary channels are associated with the second primary channel but not with the first primary channel, the method comprising: determining whether to transmit a wireless message over the first primary channel based on a property of the wireless message; in response to determining the wireless message is to be transmitted over the first primary channel: determining whether the first primary channel is idle based, at least in part, on whether a preamble is detected on the second primary channel, performing a first back-off procedure based on whether the determination, and transmitting the wireless message over the first primary channel based on a completion of the first back-off procedure, wherein the transmission is restricted to the first frequency spectrum, and in response to determining the wireless message is to be transmitted over a channel different than the first primary channel; second determining whether the second primary channel is idle based, at least in part, on whether a preamble is detected on the first primary channel; performing a second back-off procedure based on the second determination, determining whether one or more of the secondary channels associated with the second primary channel are idle for a PCT Inter-frame Space (PIFS) time period before a transmission of the wireless message, and transmitting the wireless message over the second primary channel and the determined idle secondary channels based on a completion of the second back-off procedure. ### Claim 14 (depends on 13) The computer readable storage medium of claim 13, wherein the determination of whether to transmit the wireless message on the first primary channel is based on whether an amount of data waiting for transmission is above a threshold. ### Claim 15 (depends on 13) The computer readable storage medium of claim 13, wherein the one or more secondary channels comprise a two megahertz secondary channel, a four megahertz secondary channel, and an eight megahertz secondary channel. ### Claim 16 (depends on 14) The computer readable storage medium of claim 14, the method further comprising determining to transmit the wireless message on the second primary channel without use of the associated secondary channels if no secondary channels are idle for the PCF Inter-frame space (PIFS) time period when the second back-off procedure is complete.