# US 6,724,845 B1 · Modified filtering for asynchronous inputs > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 6,724,845 B1 - Document ID: US6724845B1 - Status: Granted - Kind: B1 - Application number: 09/640,128 - Filed: 2000-08-16 - Granted: 2004-04-20 - Earliest claimed: 2000-08-16 - Assignees: Koninklijke Philips Electronics N.V. - Inventors: Debarag Narayan Banerjee - Web page: https://patentgrep.com/patent/US6724845B1 ## CPC - H04B 1/7075: with code phase acquisition - H04B 1/0003: {Software-defined radio [SDR] systems, i.e. systems wherein components typically implemented in hardware, e.g. filters or modulators/demodulators, are implented using software, e.g. by involving an AD or DA conversion stage such that at least part of the signal processing is performed in the digital domain (digital baseband systems H04L25/00; digital modulation/demodulation H04L27/00; CDMA H04B1/707; TDMA H04B7/2643; image transmission H04N5/00)} - H04B 1/7097: Interference-related aspects - H04B: TRANSMISSION ## Abstract For use in a digital signal processing system, a filter implementation factors in the time difference between consecutive searches for the same signal and modifies the filter depending on the time-arrival differences of consecutive search results. An example application to which the invention is particularly well adapted is in a mobile receiver for a cellular radiotelephone communications system. In accordance with the present invention, after determining a relative arrival time of data sample sets in the stream of data samples, the mobile station includes a receiver arrangement configured to filter a stream of data samples arriving at irregular intervals, to provide a relative arrival time of data sample sets in the stream of data samples, and in response to determining the relative arrival time, to filter the data sample sets using value assignments that are exponentially weighted for the data sample sets. The data sample sets are weighted more than data sample sets arriving early. In a more specific implementation, the receiver arrangement searches the data sample sets for a signal strength signal, and filters the data sample sets based on time-arrival differences of consecutive search results. ## Claims ### Claim 1 For use in a communication system, a method of filtering a stream of data samples arriving at irregular intervals, comprising: providing a relative arrival time of data sample sets in the stream of data samples; in response to providing the relative arrival time, filtering the data sample sets using value assignments that are exponentially weighted for the data sample sets, the data sample sets being weighted more than data sample sets arriving late. ### Claim 2 (depends on 1) The method of claim 1, wherein each of the data sample sets is composed of a single data sample. ### Claim 3 (depends on 2) The method of claim 2, wherein the filtering includes modifications of IIR filtering with the value assignments being weighted as a function of one or more filter coefficients. ### Claim 4 (depends on 2) The method of claim 2, wherein the filtering includes IIR filtering with the value assignments being weighted by a first weighting factor in response to determining that the data sample arrived not after a unit sample interval for the IIR filtering. ### Claim 5 (depends on 4) The method of claim 4, wherein the filtering includes IIR filtering with the value assignments being weighted by a second weighting factor in response to determining that the data sample arrived after a unit sample interval for the IIR filtering. ### Claim 6 (depends on 1) The method of claim 1, wherein providing a relative arrival time of data sample sets includes determining the relative arrival time as an approximate integral multiple of unit sample intervals for the filtering, and wherein the data sample sets correspond to a pilot signal. ### Claim 7 (depends on 6) The method of claim 6, wherein the value assignments of a data sample set is exponentially weighted by a factor that is a function of the approximate number of integral multiple of unit sample intervals corresponding to the relative arrival time of the corresponding data sample set. ### Claim 8 (depends on 1) The method of claim 1, wherein filtering the data sample sets includes filtering data samples corresponding to signal strength estimates having irregularly timed estimations, the irregularly timed estimations being performed by a station responding to signals received from each of a plurality of fixed-location radio stations. ### Claim 9 (depends on 1) The method of claim 1, wherein providing a relative arrival time of data sample sets includes determining the relative arrival time of the data sample sets. ### Claim 10 For use in a mobile-service radio system having a plurality of base stations and mobile stations, a method of filtering a stream of data samples arriving at irregular intervals, comprising: at one of the mobile receivers, receiving an analog signal including data carried in a CDMA format, converting the analog signal to digital codes, and evaluating the digital codes to provide filter coefficients while searching for a selected signal, the filter coefficients defined as a function of time-arrival differences of consecutive search results for the selected signal using exponential weighting criteria including weighting the data sample sets arriving late more than data sample sets arriving early. ### Claim 11 (depends on 10) The method of claim 10, wherein the selected signal is a signal strength indicator. ### Claim 12 (depends on 10) The method of claim 10, further including providing the filter coefficients by accessing a table. ### Claim 13 (depends on 10) The method of claim 10, further including computing the filter coefficients. ### Claim 14 For use in a communication system, an arrangement for filtering a stream of data samples arriving at irregular intervals, comprising: means for providing a relative arrival time of data sample sets in the stream of data samples; means, responsive to providing the relative arrival time, for filtering the data sample sets using value assignments that are exponentially weighted for the data sample sets, the data sample sets being weighted more than data sample sets arriving early. ### Claim 15 (depends on 14) The arrangement of claim 14, wherein each of the data sample sets is composed of a single data sample. ### Claim 16 (depends on 14) The arrangement of claim 14, wherein the filtering includes modifications of IIR filtering with the value assignments being weighted as a function of one or more filter coefficients. ### Claim 17 (depends on 14) The arrangement of claim 14, wherein the filtering includes IIR filtering with the value assignments being weighted by a first weighting factor in response to determining that the data sample arrived not after a unit sample interval for the IIR filtering. ### Claim 18 (depends on 17) The arrangement of claim 17, wherein the filtering includes IIR filtering with the value assignments being weighted by a second weighting factor in response to determining that the data sample arrived after a unit sample interval for the IIR filtering. ### Claim 19 For use in a communication system, an arrangement for filtering a stream of data samples arriving at irregular intervals, comprising: a receiver including a digital signal processing arrangement configured and arranged to provide a relative arrival time of data sample sets in the stream of data samples, and, responsive to providing the relative arrival time, to filter the data sample sets using value assignments that are exponentially weighted for the data sample sets, the data sample sets being weighted more than data sample sets arriving early. ### Claim 20 A communication system, comprising: a mobile station including a receiver arrangement configured to filter a stream of data samples arriving at irregular intervals, to provide a relative arrival time of data sample sets in the stream of data samples, and in response to providing the relative arrival time, to filter the data sample sets using value assignments that are exponentially weighted for the data sample sets, the data sample sets being weighted more than data sample sets arriving early; and a plurality of base stations configured and arranged to communicate with the mobile station using CDMA. ### Claim 21 (depends on 20) The communication system of claim 20, wherein the receiver arrangement is further configured to search the data sample sets for a pilot signal and to filter the data sample sets based on time-arrival differences of consecutive starch results ensuing from the searching. ### Claim 22 (depends on 20) The communication system of claim 20, wherein the receiver arrangement further includes at least one digital signal processor programmed and arranged to perform despreading and integration and filtering on data samples for a plurality of different PN sequences. ### Claim 23 In a communication system having a plurality of base stations configured and arranged to communicate with mobile stations using CDMA, a mobile station comprising: a receiver front end; a receiver arrangement responsive to the receiver front end and configured to filter a stream of data samples arriving at irregular intervals, to provide a relative arrival time of data sample sets in the stream of data samples, and in response to providing the relative arrival time, to filter the data sample sets using value assignments that are exponentially weighted for the data sample sets, the data sample sets being weighted more than data sample sets arriving early.