# US 7,609,773 B2 · Method of determining the location of the FFT window and the delay spread for the platinum broadcast channel estimator > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,609,773 B2 - Document ID: US7609773B2 - Status: Granted - Kind: B2 - Application number: 11/174,108 - Filed: 2005-06-29 - Published: 2006-10-19 - Granted: 2009-10-27 - Earliest claimed: 2005-04-18 - Assignees: QUALCOMM Incorporated - Inventors: Naga Bhushan; June Namgoong; Peter J. Black - Web page: https://patentgrep.com/patent/US7609773B2 ## CPC - H04L 27/2662: {Symbol synchronisation} - H04L 25/022: {of frequency response} - H04L 27/2665: {Fine synchronisation, e.g. by positioning the FFT window} - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract In one embodiment, the invention comprises a channel estimation method, comprising determining a FFT window position, and calculating a delay spread. In another embodiment, the step of determining a FFT window position comprises setting an initial position of the FFT window, computing an energy for each tap, time averaging said energy for each tap, comparing an average energy of each tap with a first threshold multiplied by the average energy of all taps, comparing the average energy of each tap with a second threshold multiplied by a maximum average energy in alias components, updating the set of paths if the average energy of the tap is greater than said second threshold multiplied by the maximum average energy in alias components; and refining the FFT window position. ## Claims ### Claim 1 A channel estimation method, comprising: receiving an RF signal in an RF receiver; downconverting the received RF signal to obtain a received IF signal in an IF receiver; converting the received IF signal into a digital signal in an analog to digital converter; determining a FFT window position of the converted digital signal in a digital signal processor; and calculating a delay spread, wherein said step of determining a FFT window position comprises: setting an initial position of said FFT window; computing an energy for each tap; time averaging said energy for each said tap; comparing an average energy of each said tap with a first threshold; comparing said average energy of each said tap with a second threshold multiplied by a maximum average energy in alias components; updating said set of paths if said average energy of said tap is greater than said second threshold multiplied by said maximum average energy in alias components; and defining said FFT window position. ### Claim 2 (depends on 1) The method according to claim 1 ,wherein said step of comparing an average energy of each said tap with a first threshold comprises: comparing an average energy of each said tap with the first threshold multiplied by a mean average energy over all said taps. ### Claim 3 (depends on 1) The method according to claim 1, wherein said step of comparing an average energy of each said tap with a first threshold comprises: comparing said average energy of each said tap with the first threshold multiplied by a minimum average energy over all said taps. ### Claim 4 (depends on 1) The method according to claim 1, wherein said-step of comparing an average energy of each said tap with a first threshold comprises: comparing said average energy of each said tap with the first threshold multiplied by a maximum average energy over all said taps. ### Claim 5 (depends on 1) The method according to claim 1, wherein said step of setting an initial position of an FFT window comprises: backing off from an earliest arriving path; defining an index of a first component of an estimated channel response; defining an index of a last component of an estimated channel response; and calculating a channel response over said FFT window from said index of said first component of said estimated channel response to said index of said last component of said estimated channel response. ### Claim 6 (depends on 1) The method according to claim 1, wherein said step of defining said FFT window position comprises: defining an earliest path location; defining a latest path location; setting a starting point of said FFT window to said earliest path location minus a backoff if a difference between said earliest and said latest path locations plus twice said backoff is less than or equal to a cyclic prefix; and setting a starting point of said FFT window to said earliest path location minus one half of {(a sum of (a cyclic prefix and said earliest path location)) minus (said latest path location)} if said difference between said earliest and said latest path locations plus twice said backoff is greater than said a cyclic prefix. ### Claim 7 (depends on 1) The method according to claim 1, wherein said step of computing an energy for each tap comprises squaring absolute values of a channel response for each tap. ### Claim 8 A channel estimation method, comprising: receiving an RF signal in an RF receiver; downconverting the received RF signal to obtain a received IF signal in an IF receiver; converting the received IF signal into a digital signal in an analog to digital converter; determining a FFT window position of the converted digital signal in a digital signal processor; and calculating a delay spread, wherein said step of determining a FFT window position comprises: setting an initial position of said FFT window; computing an energy for each tap; time averaging said energy for each said tap; comparing an earliest path hypothesis for each said tap with a first threshold multiplied by a mean average energy over all said taps; comparing said average energy of each said tap with a second threshold multiplied by a maximum average energy in alias components; updating said set of paths if said average energy of said tap is greater than said second threshold multiplied by said maximum average energy in alias components; and defining said FFT window position. ### Claim 9 A receiver to estimate a channel, comprising: an RF receiver having an input and an output; an IF receiver having an input and an output, wherein said input is operably connected to an output of said RF receiver; an analog-to-digital converter having an input and an output, wherein said input is operably connected to said output of said IF receiver; a decoder having an input and an output; and a processor having an input and an output, wherein said input is operably connected to said output of said analog-to-digital converter and said output is operably connected to said input of said decoder and said processor comprises memory, and software comprising instructions stored in said memory, wherein said receiver is adapted to execute said instructions stored in said memory comprising determining a FFT window position; and calculating a delay spread, wherein said determining a FFT window position instruction comprises: setting an initial position of said FFT window; computing an energy for each tap; time averaging said energy for each said tap; comparing an average energy of each said tap with a first threshold; comparing said average energy of each said tap with a second threshold multiplied by a maximum average energy in alias components; updating said set of paths if said average energy of said tap is greater than said second threshold multiplied by said maximum average energy in alias components; and defining said FFT window position. ### Claim 10 (depends on 9) The receiver according to claim 9, wherein said comparing an average energy of each said tap with a first threshold comprises: comparing an average energy of each said tap with the first threshold multiplied by a mean average energy over all said taps. ### Claim 11 (depends on 9) The receiver according to claim 9, wherein said comparing an average energy of each said tap with a first threshold comprises: comparing said average energy of each said tap with the first threshold multiplied by a minimum average energy over all said taps. ### Claim 12 (depends on 9) The receiver according to claim 9, wherein said comparing an average energy of each said tap with a first threshold comprises: comparing said average energy of each said tap with the first threshold multiplied by a maximum average energy over all said taps. ### Claim 13 (depends on 9) The receiver according to claim 9, wherein said setting an initial position of an FFT window instruction comprises: backing off from an earliest arriving path; defining an index of a first component of an estimated channel response; defining an index of a last component of an estimated channel response; and calculating a channel response over said FFT window from said index of said first component of said estimated channel response to said index of said last component of said estimated channel response. ### Claim 14 (depends on 9) The receiver according to claim 9, wherein said defining said FFT window position instruction comprises: defining an earliest path location; defining a latest path location; setting a staffing point of the FFT window to said earliest path location minus a backoff if a difference between said earliest and said latest path locations plus twice said backoff is less than or equal to a cyclic prefix; and setting a staffing point of the FFT window to said earliest path location minus one half of {(a sum of (a cyclic prefix and said earliest path location)) minus (said latest path location)} if said difference between said earliest and said latest path locations plus twice said backoff is greater than said a cyclic prefix. ### Claim 15 (depends on 9) The receiver according to claim 9, wherein said computing an energy for each tap instruction comprises squaring absolute values of a channel response for each tap. ### Claim 16 A receiver to estimate a channel, comprising: an RF receiver having an input and an output; an IF receiver having an input and an output, wherein said input is operably connected to an output of said RF receiver; an analog-to-digital converter having an input and an output, wherein said input is operably connected to said output of said IF receiver; a decoder having an input and an output; and a processor having an input and an output, wherein said input is operably connected to said output of said analog-to-digital converter and said output is operably connected to said input of said decoder and said processor comprises memory, and software comprising instructions stored in said memory, wherein said receiver is adapted to execute said instructions stored in said memory comprising: determining a FFT window position; and calculating a delay spread, wherein said determining a FFT window position instruction comprises: setting an initial position of an FFT window; computing an energy for each tap; time averaging said energy for each said tap; comparing an earliest path hypothesis for each said tap with a first threshold multiplied by a mean average energy of all said taps; comparing said average energy of each said tap with a second threshold multiplied by a maximum average energy in alias components; updating said set of paths if said average energy of said tap is greater than said second threshold multiplied by said maximum average energy in alias components; and defining said FFT window position. ### Claim 17 A processor to estimate a channel, comprising: memory; and software comprising instructions stored in said memory, wherein said processor is adapted to execute said instructions stored in said memory comprising determining a FFT window position; and calculating a delay spread, wherein said determining a FFT window position instruction comprises: setting an initial position of said FFT window; computing an energy for each tap; time averaging said energy for each said tap; comparing an average energy of each said tap with a first threshold; comparing said average energy of each said tap with a second threshold multiplied by a maximum average energy in alias components; updating said set of paths if said average energy of said tap is greater than said second threshold multiplied by said maximum average energy in alias components; and defining said FFT window position. ### Claim 18 (depends on 17) The processor according to claim 17, wherein said comparing an average energy of each said tap with a first threshold comprises: comparing an average energy of each said tap with the first threshold multiplied by a mean average energy over all said taps. ### Claim 19 (depends on 17) The processor according to claim 17, wherein said comparing an average energy of each said tap with a first threshold comprises: comparing said average energy of each said tap with the first threshold multiplied by a minimum average energy over all said taps. ### Claim 20 (depends on 17) The processor according to claim 17, wherein said comparing an average energy of each said tap with a first threshold comprises: comparing said average energy of each said tap with the first threshold multiplied by a maximum average energy over all said taps. ### Claim 21 (depends on 17) The processor according to claim 17, wherein said setting an initial position of an FFT window instruction comprises: backing off from an earliest arriving path; defining an index of a first component of an estimated channel response; defining an index of a last component of an estimated channel response; and calculating a channel response over said FFT window from said index of said first component of said estimated channel response to said index of said last component of said estimated channel response. ### Claim 22 (depends on 17) The processor according to claim 17, wherein said defining said FFT window position instruction comprises: defining an earliest path location; defining a latest path location; setting a staffing point of the FFT window to said earliest path location minus a backoff if a difference between said earliest and said latest path locations plus twice said backoff is less than or equal to a cyclic prefix; and setting a staffing point of the FFT window to said earliest path location minus one half of {(a sum of (a cyclic prefix and said earliest path location)) minus (said latest path location)} if said difference between said earliest and said latest path locations plus twice said backoff is greater than said a cyclic prefix. ### Claim 23 (depends on 17) The processor according to claim 17, wherein said computing an energy for each tap instruction comprises squaring absolute values of a channel response for each tap. ### Claim 24 A processor to estimate a channel, comprising: memory; and software comprising instructions stored in said memory, wherein said processor is adapted to execute said instructions stored in said memory comprising determining a FFT window position; and calculating a delay spread, wherein said determining a FFT window position instruction comprises: setting an initial position of said FFT window; computing an energy for each tap; time averaging said energy for each said tap; comparing an earliest path hypothesis for each said tap with a first threshold multiplied by a mean average energy over all said taps; comparing said average energy of each said tap with a second threshold multiplied by a maximum average energy in alias components; updating said set of paths if said average energy of said tap is greater than said second threshold multiplied by said maximum average energy in alias components; and defining said FFT window position. ### Claim 25 A receiver means to estimate a channel, comprising: an RF receiver means having an input and an output; an IF receiver means having an input and an output, wherein said input is operably connected to an output of said RF receiver means; an analog-to-digital converter means having an input and an output, wherein said input is operably connected to said output of said IF receiver means; a decoder means having an input and an output; and a processor means having an input and an output, wherein said input is operably connected to said output of said analog-to-digital converter means and said output is operably connected to said input of said decoder means and said processor means comprises memory means, and software comprising instructions stored in said memory means, wherein said receiver means is adapted to execute said instructions stored in said memory means comprising determining a FFT window position; and calculating a delay spread, wherein said determining a FFT window position instruction comprises: setting an initial position of said FFT window; computing an energy for each tap; time averaging said energy for each said tap; comparing an average energy of each said tap with a first threshold comparing said average energy of each said tap with a second threshold multiplied by a maximum average energy in alias components; updating said set of paths if said average energy of said tap is greater than said second threshold multiplied by said maximum average energy in alias components; and defining said FFT window position. ### Claim 26 (depends on 25) The receiver means according to claim 25, wherein said comparing an average energy of each said tap with a first threshold comprises: comparing an average energy of each said tap with the first threshold multiplied by a mean average energy over all said taps. ### Claim 27 (depends on 25) The receiver means according to claim 25, wherein said comparing an average energy of each said tap with a first threshold comprises: comparing said average energy of each said tap with the first threshold multiplied by a minimum average energy over all said taps. ### Claim 28 (depends on 25) The receiver means according to claim 25, wherein said comparing an average energy of each said tap with a first threshold comprises: comparing said average energy of each said tap with the first threshold multiplied by a maximum average energy over all said taps. ### Claim 29 (depends on 25) The receiver means according to claim 25, wherein said setting an initial position of an FFT window instruction comprises: backing off from an earliest arriving path; defining an index of a first component of an estimated channel response; defining an index of a last component of an estimated channel response; and calculating a channel response over said FFT window from said index of said first component of said estimated channel response to said index of said last component of said estimated channel response. ### Claim 30 The receiver means according to claim, wherein said defining said FFT window position instruction comprises: defining an earliest path location; defining a latest path location; setting a starting point of said FFT window to said earliest path location minus a backoff if a difference between said earliest and said latest path locations plus twice said backoff is less than or equal to a cyclic prefix; and setting a starting point of said FFT window to said earliest path location minus one half of {(a sum of (a cyclic prefix and said earliest path location)) minus (said latest path location)} if said difference between said earliest and said latest path locations plus twice said backoff is greater than said a cyclic prefix. ### Claim 31 (depends on 25) The receiver means according to claim 25, wherein said computing an energy for each tap instruction comprises squaring absolute values of a channel response for each tap. ### Claim 32 A receiver means to estimate a channel, comprising: an RF receiver means having an input and an output; an IF receiver means having an input and an output, wherein said input is operably connected to an output of said RF receiver means; an analog-to-digital converter means having an input and an output, wherein said input is operably connected to said output of said IF receiver means; a decoder means having an input and an output; and a processor means having an input and an output, wherein said input is operably connected to said output of said analog-to-digital converter means and said output is operably connected to said input of said decoder means and said processor means comprises memory means, and software comprising instructions stored in said memory means, wherein said receiver means is adapted to execute said instructions stored in said memory means comprising determining a FFT window position; and calculating a delay spread, wherein said determining a FFT window position instruction comprises: setting an initial position of said FFT window; computing an energy for each tap; time averaging said energy for each said tap; comparing an earliest path hypothesis for each said tap with a first threshold multiplied by a mean average energy over all said taps; comparing said average energy of each said tap with a second threshold multiplied by a maximum average energy in alias components; updating said set of paths if said average energy of said tap is greater than said second threshold multiplied by said maximum average energy in alias components; and defining said FFT window position. ### Claim 33 A processor means to estimate a channel, comprising: memory means; and software comprising instructions stored in said memory means, wherein said processor means is adapted to execute said instructions stored in said memory means comprising determining a FFT window position; and calculating a delay spread, wherein said determining a FFT window position instruction comprises: setting an initial position of said FFT window; computing an energy for each tap; time averaging said energy for each said tap; comparing an average energy of each said tap with a first threshold; comparing said average energy of each said tap with a second threshold multiplied by a maximum average energy in alias components; updating said set of paths if said average energy of said tap is greater than said second threshold multiplied by said maximum average energy in alias components; and defining said FFT window position. ### Claim 34 (depends on 33) The processor means according to claim 33, wherein said comparing an average energy of each said tap with a first threshold comprises: comparing an average energy of each said tap with the first threshold multiplied by a mean average energy over all said taps. ### Claim 35 (depends on 33) The processor means according to claim 33, wherein said comparing an average energy of each said tap with a first threshold comprises: comparing said average energy of each said tap with the first threshold multiplied by a minimum average energy over all said taps. ### Claim 36 (depends on 33) The processor means according to claim 33, wherein said comparing an average energy of each said tap with a first threshold comprises: comparing said average energy of each said tap with the first threshold multiplied by a maximum average energy over all said taps. ### Claim 37 A processor means to estimate a channel, comprising: memory means; and software comprising instructions stored in said memory means, wherein said processor means is adapted to execute said instructions stored in said memory means comprising determining a FFT window position; and calculating a delay spread, wherein said determining a FFT window position instruction comprises: setting an initial position of said FFT window; computing an energy for each tap; time averaging said energy for each said tap; comparing an earliest path hypothesis for each said tap with a first threshold multiplied by a mean average energy over all said taps; comparing said average energy of each said tap with a second threshold multiplied by a maximum average energy in alias components; updating said set of paths if said average energy of said tap is greater than said second threshold multiplied by said maximum average energy in alias components; and defining said FFT window position. ### Claim 38 (depends on 33) The processor means according to claim 33, wherein said setting an initial position of an FFT window instruction comprises: backing off from an earliest arriving path; defining an index of a first component of an estimated channel response; defining an index of a last component of an estimated channel response; and calculating a channel response over said FFT window from said index of said first component of said estimated channel response to said index of said last component of said estimated channel response. ### Claim 39 (depends on 33) The processor means according to claim 33, wherein said defining said FFT window position instruction comprises: defining an earliest path location; defining a latest path location; setting a starting point of the FFT window to said earliest path location minus a backoff if a difference between said earliest and said latest path locations plus twice said backoff is less than or equal to a cyclic prefix; and setting a starting point of the FFT window to said earliest path location minus one half of {(a sum of (a cyclic prefix and said earliest path location)) minus (said latest path location)} if said difference between said earliest and said latest path locations plus twice said backoff is greater than said a cyclic prefix. ### Claim 40 (depends on 33) The processor means according to claim 33, wherein said computing an energy for each tap instruction comprises squaring absolute values of a channel response for each tap. ### Claim 41 A storage medium having stored thereon processor-executable software instructions configured to cause a processor to perform steps comprising: determining a FFT window position; and calculating a delay spread, wherein said step of determining a FFT window position comprises: setting an initial position of said FFT window; computing an energy for each tap; time averaging said energy for each said tap; comparing an average energy of each said tap with a first threshold; comparing said average energy of each said tap with a second threshold multiplied by a maximum average energy in alias components; updating said set of paths if said average energy of said tap is greater than said second threshold multiplied by said maximum average energy in alias components; and defining said FFT window position. ### Claim 42 (depends on 41) The storage medium of claim 41, wherein comparing an average energy of each said tap with a first threshold comprises comparing an average energy of each said tap with the first threshold multiplied by a minimum average energy over all said taps. ### Claim 43 (depends on 41) The storage medium of claim 41, wherein comparing an average energy of each said tap with a first threshold comprises comparing an average energy of each said tap with the first threshold multiplied by a maximum average energy over all said taps. ### Claim 44 (depends on 41) The storage medium of claim 41, wherein comparing an average energy of each said tap with a first threshold comprises comparing an average energy of each said tap with the first threshold multiplied by a mean average energy over all said taps. ### Claim 45 (depends on 41) The storage medium of claim 41, wherein the stored processor-executable software instructions are configured to cause a processor to perform further steps comprising: backing off from an earliest arriving path; defining an index of a first component of an estimated channel response; defining an index of a last component of an estimated channel response; and calculating a channel response over said FFT window from said index of said first component of said estimated channel response to said index of said last component of said estimated channel response. ### Claim 46 (depends on 41) The storage medium of claim 41, wherein the stored processor-executable software instructions are configured to cause a processor to perform further steps comprising: defining an earliest path location; defining a latest path location; setting a starting point of said FFT window to said earliest path location minus a backoff if a difference between said earliest and said latest path locations plus twice said backoff is less than or equal to a cyclic prefix; and setting a starting point of said FFT window to said earliest path location minus one half of {(a sum of (a cyclic prefix and said earliest path location)) minus (said latest path location)} if said difference between said earliest and said latest path locations plus twice said backoff is greater than said a cyclic prefix. ### Claim 47 (depends on 41) The storage medium of claim 41, wherein the stored processor-executable software instructions are configured to cause a processor to perform further steps comprising: squaring absolute values of a channel response for each tap.