# US 11,906,648 B2 · Compressing and decompressing data about radio signals > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,906,648 B2 - Document ID: US11906648B2 - Status: Granted - Kind: B2 - Application number: 17/571,219 - Filed: 2022-01-07 - Published: 2022-04-28 - Granted: 2024-02-20 - Earliest claimed: 2019-12-06 - Assignees: HERE Global B.V. - Applicants: Here Global B.V. - Inventors: Lauri Wirola; Pavel Ivanov; Muhammad Irshan Khan; Jari Syrjärinne; Jukka Talvitie; Elena-Simona Lohan - Web page: https://patentgrep.com/patent/US11906648B2 ## CPC - G01S 5/0278: {involving statistical or probabilistic considerations (G01S5/0252, G01S5/0294 take precedence)} - G01S 5/0242: {Determining the position of transmitters to be subsequently used in positioning (G01S5/0289 takes precedence)} - G01S 5/0247: {Determining attitude} - G01S 5/02523: {Details of interaction of receiver with radio-map} - G01S 5/0284: {Relative positioning} - H04L 69/04: Protocols for data compression, e.g. ROHC - 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)} - G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES - 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 An apparatus obtains a set of radio data comprising signal strength related values for radio signals transmitted by a transmitter with an association of each signal strength related value with a representation of a geographical location. The apparatus applies a frequency transform to the obtained set of radio data to obtain transform coefficients, each transform coefficient comprising a transform index and an associated transform value. The apparatus selects a subset of transform indices having more significant transform values than the remaining transform indices and compresses the transform indices by encoding each transform index exploiting a probability of occurrence of an index value of a respective transform index. The same or another apparatus decodes the compressed transform indices again for use in position operations. ## Claims ### Claim 1 A method comprising: applying a frequency transform to a set of radio data to obtain transform coefficients, the set of radio data comprising signal strength related values that are associated with a representation of a geographical location, each transform coefficient comprising a transform index and an associated transform value; based upon energy of frequency transformed radio data, selecting at least a minimum number of transform indices having more significant transform values than the remaining transform indices; and encoding selected transform indices exploiting a probability of occurrence of an index value of a respective transform index, wherein selecting at least the minimum number of transform indices comprises excluding the transform coefficient corresponding to a direct current (DC) component. ### Claim 2 (depends on 1) The method according to claim 1, wherein selecting at least the minimum number of transform indices comprises selecting the transform indices such that the associated transform values include a predetermined percentage of total energy in the transform values of the transform coefficients obtained from the set of radio data. ### Claim 3 (depends on 1) The method according to claim 1, wherein selecting at least the minimum number of transform indices comprises selecting the transform indices such that a radio image reconstructed from the transform indices has a predetermined minimum quality. ### Claim 4 (depends on 1) The method according to claim 1, wherein selecting at least the minimum number of transform indices comprises selecting the transform indices for which the associated transform values exceed a predetermined threshold. ### Claim 5 (depends on 1) The method according to claim 1, wherein the set of radio data comprises a plurality of radio image matrices, wherein each radio image matrix corresponds to a different transmitter, and wherein each radio image matrix is separately processed by separately applying the frequency transform to a respective radio image matrix, selecting at least the minimum number of transform indices and encoding the selected transform indices. ### Claim 6 An apparatus comprising at least one processor and at least one memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to: apply a frequency transform to a set of radio data to obtain transform coefficients, the set of radio data comprising signal strength related values that are associated with a representation of a geographical location, each transform coefficient comprising a transform index and an associated transform value; based upon energy of frequency transformed radio data, select at least a minimum number of transform indices having more significant transform values than the remaining transform indices; and encode selected transform indices exploiting a probability of occurrence of an index value of a respective transform index, wherein the apparatus is caused to select at least the minimum number of transform indices by excluding the transform coefficient corresponding to a direct current (DC) component. ### Claim 7 (depends on 6) The apparatus according to claim 6, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to select at least the minimum number of transform indices by selecting the transform indices such that the associated transform values include a predetermined percentage of total energy in the transform values of the transform coefficients obtained from the set of radio data. ### Claim 8 (depends on 6) The apparatus according to claim 6, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to select at least the minimum number of transform indices by selecting the transform indices such that a radio image reconstructed from the transform indices has a predetermined minimum quality. ### Claim 9 (depends on 6) The apparatus according to claim 6, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to select at least the minimum number of transform indices by selecting the transform indices for which the associated transform values exceed a predetermined threshold. ### Claim 10 (depends on 6) The apparatus according to claim 6, wherein the set of radio data comprises a plurality of radio image matrices, wherein each radio image matrix corresponds to a different transmitter, and wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus to separately process each radio image matrix by separately applying the frequency transform to a respective radio image matrix, selecting at least the minimum number of transform indices and encoding the selected transform indices. ### Claim 11 A method comprising: for each of a plurality of radio image matrices, applying a frequency transform to obtain transform coefficients from a set of radio data comprising the plurality of radio image matrices corresponding to different transmitters, each transform coefficient comprising a transform index and an associated transform value; for each of the plurality of radio image matrices and based upon energy of frequency transformed radio data as represented by the transform coefficients, selecting a subset of transform indices; and for each of the plurality of radio image matrices, compressing the subset of transform indices by encoding the transform indices exploiting a probability of occurrence of an index value of a respective transform index, wherein selecting at least the minimum number of transform indices comprises excluding the transform coefficient corresponding to a direct current (DC) component. ### Claim 12 (depends on 11) The method according to claim 11, wherein selecting the subset of transform indices comprises selecting at least a minimum number of transform indices having more significant transform values than the remaining transform indices. ### Claim 13 (depends on 12) The method according to claim 12, wherein selecting at least the minimum number of transform indices comprises selecting the transform indices such that the associated transform values include a predetermined percentage of total energy in the transform values of the transform coefficients obtained from the set of radio data. ### Claim 14 (depends on 12) The method according to claim 12, wherein selecting at least the minimum number of transform indices comprises selecting the transform indices such that a radio image reconstructed from the transform indices has a predetermined minimum quality. ### Claim 15 An apparatus comprising at least one processor and at least one memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to: for each of a plurality of radio image matrices, apply a frequency transform to obtain transform coefficients from a set of radio data comprising the plurality of radio image matrices corresponding to different transmitters, each transform coefficient comprising a transform index and an associated transform value; for each of the plurality of radio image matrices and based upon energy of frequency transformed radio data as represented by the transform coefficients, select a subset of transform indices; and for each of the plurality of radio image matrices, compress the subset of transform indices by encoding the transform indices exploiting a probability of occurrence of an index value of a respective transform index, wherein the apparatus is caused to select at least the minimum number of transform indices by excluding the transform coefficient corresponding to a direct current (DC) component. ### Claim 16 (depends on 15) The apparatus according to claim 15, wherein the at least one memory and the computer program code are configured to with the at least one processor, cause the apparatus to select the subset of transform indices by selecting at least a minimum number of transform indices having more significant transform values than the remaining transform indices. ### Claim 17 (depends on 16) The apparatus according to claim 16, wherein the at least one memory and the computer program code are configured to with the at least one processor, cause the apparatus to select at least the minimum number of transform indices by selecting the transform indices such that the associated transform values include a predetermined percentage of total energy in the transform values of the transform coefficients obtained from the set of radio data. ### Claim 18 (depends on 16) The apparatus according to claim 16, wherein the at least one memory and the computer program code are configured to with the at least one processor, cause the apparatus to select at least the minimum number of transform indices by selecting the transform indices such that a radio image reconstructed from the transform indices has a predetermined minimum quality.