Method and apparatus for fast pilot channel acquisition using a matched filter in a CDMA radiotelephone
First Claim
1. A radiotelephone configured to receive DS-CDMA signals in a communication system including a plurality of base stations, each base station being identified by a unique starting phase of a known pseudorandom noise (PN) sequence, the radiotelephone comprising:
- a rake receiver having a plurality of receiver fingers;
a receiver searcher for detecting pilot signals from the plurality of base stations,wherein the pilot signals are quadrature modulated, each of the pilot signals including in-phase (I) symbols and quadrature-phase (Q) symbols, wherein the I symbols are spread using an I PN sequence and the O symbols are spread using a Q PN sequence,the receiver searcher including a matched filter for comparing a detected PN sequence and a predetermined PN sequence and producing a response, wherein the matched filter includesan I filter for comparing a detected I PN sequence and a stored I PN sequence, anda Q filter for comparing a detected Q PN sequence and a stored Q PN sequence; and
a controller coupled to the receiver searcher and the rake receiver, the controller including a memory for storing the response as a stored response, the controller controlling the plurality of receiver fingers in response to the stored response.
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Accused Products
Abstract
Performance of a radiotelephone (104) in a CDMA communication system (100) is enhanced using a receiver searcher (114) that includes a matched filter (128) to capture the pilot energies of all receivable transmissions from a base station (102) and other nearby base stations. A detected PN sequence is compared with a predetermined PN sequence stored at the radiotelephone (104). The predetermined PN sequence includes, for example, the last 512 chips in the short PN sequence used for spreading the in-phase channel and the quadrature-phase channel.
232 Citations
26 Claims
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1. A radiotelephone configured to receive DS-CDMA signals in a communication system including a plurality of base stations, each base station being identified by a unique starting phase of a known pseudorandom noise (PN) sequence, the radiotelephone comprising:
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a rake receiver having a plurality of receiver fingers; a receiver searcher for detecting pilot signals from the plurality of base stations, wherein the pilot signals are quadrature modulated, each of the pilot signals including in-phase (I) symbols and quadrature-phase (Q) symbols, wherein the I symbols are spread using an I PN sequence and the O symbols are spread using a Q PN sequence, the receiver searcher including a matched filter for comparing a detected PN sequence and a predetermined PN sequence and producing a response, wherein the matched filter includes an I filter for comparing a detected I PN sequence and a stored I PN sequence, and a Q filter for comparing a detected Q PN sequence and a stored Q PN sequence; and a controller coupled to the receiver searcher and the rake receiver, the controller including a memory for storing the response as a stored response, the controller controlling the plurality of receiver fingers in response to the stored response. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A radiotelephone configured to receive DS-CDMA signals in a communication system including a plurality of base stations, each base station being identified by a unique starting phase of a known pseudorandom noise (PN) sequence, the radiotelephone comprising:
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a rake receiver having a plurality of receiver fingers; a receiver searcher for detecting pilot signals from the plurality of base stations, the receiver searcher including a matched filter for comparing a detected PN sequence and a predetermined PN sequence and producing a response, and wherein the matched filter comprises a comparator for suppressing the response when the response does not exceed a predetermined threshold; and a controller coupled to the receiver searcher and the rake receiver, the controller including a memory for storing the response as a stored response, the controller controlling the plurality of receiver fingers in response to the stored response.
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21. A radiotelephone configured to receive DS-CDMA signals in a communication system including a plurality of base stations, each base station being identified by a unique starting phase of a known pseudorandom noise (PN) sequence, the radiotelephone comprising:
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a rake receiver having a plurality of receiver fingers; a receiver searcher for detecting pilot signals from the plurality of base stations, the receiver searcher including a matched filter for comparing a detected PN sequence and a predetermined PN sequence and producing a response, and wherein the matched filter comprises multiple matched filters and a summing element, each matched filter comparing a portion of the detected PN sequence and a predetermined PN sequence and producing a filter response, the summing element combining respective filter responses to produce a total response, the controller controlling the plurality of receiver fingers in response to the total response; and a controller coupled to the receiver searcher and the rake receiver, the controller including a memory for storing the response as a stored response, the controller controlling the plurality of receiver fingers in response to the stored response, wherein the controller determines presence of DS-CDMA signals based on the response.
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22. A radiotelephone configured to receive DS-CDMA signals in a communication system including a plurality of base stations, each base station being identified by a unique starting phase of a known pseudorandom noise (PN) sequence, the radiotelephone comprising:
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a rake receiver having a plurality of receiver fingers; a receiver searcher for detecting pilot signals from the plurality of base stations, the receiver searcher including a matched filter for comparing a detected PN sequence and a predetermined PN sequence and producing a response, and wherein the receiver searcher is configured to detect a plurality of pilot signals from a like plurality of base stations, the controller identifying two or more strongest pilot signals based on the response, the controller assigning respective receiver fingers to the two or more strongest pilot signals for controlling soft handoff while receiving a traffic channel from the plurality of base stations; and a controller coupled to the receiver searcher and the rake receiver, the controller including a memory for storing the response as a stored response, the controller controlling the plurality of receiver fingers in response to the stored response.
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23. A method for detecting DS-CDMA signals in a communication system, the method comprising the steps of:
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exiting a low-power mode and entering an active mode; detecting pilot signals, each of the pilot signals being covered by a respective short pseudorandom noise (PN) sequence, wherein the pilot signals are quadrature modulated, each of the pilot signals including in-phase (I) symbols and quadrature-phase (Q) symbols, wherein the I symbols are spread using an I PN sequence and the Q symbols are spread using a Q PN sequence; using a matched filter, comparing each short PN sequence and a predetermined PN sequence comprising the substeps of comparing a detected I PN sequence and a stored I PN sequence, and comparing a detected Q PN sequence and a stored Q PN sequence; when a short PN sequence matches the predetermined PN sequence, producing a match signal; in response to the match signal, assigning rake receiver fingers to a strongest match set; and detecting a paging channel transmitted by a base station. - View Dependent Claims (24, 25, 26)
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Specification