Patent EA-003472-B1 (EA)
Title: Method of cancellation of pilot and unwanted traffic signals in a cdma system
Inventor: OZLUTURK FATIH M
IPC: H04B1/7107
Filed: 1999-01-27
Abstract: 1. A cancellation system for use in a receiver that receives communication signals from a transmitter (19) over a CDMA air interface that removes selected signals from a desired traffic signal prior to decoding, the system comprising: an input (147) for receiving the communication signals; said system input (147) is introduced as an input (103) to a cancellation system of a traffic signal (101) having an output (0) equal to the difference between the desired traffic signal and an unwanted traffic signal; said input (147) for receiving signals is also introduced as an input (63) to a selected signal canceler (61) which processes the input (63) for cancelling a global pilot signal and which has an output (0add), equal to the difference the desired traffic signal and the global pilot signal; whereby the output (0add) of said selected signal canceler (61) is subtracted from the output (0) of said desired traffic signal (101) to provide the cancellation system output (151). 2. The cancellation system according to claim 1, wherein the cancellation system of a traffic signal (101) comprises a desired traffic signal despreader (91) coupled to a sum and dump processor (97) for providing an output 0sd3 and an unwanted traffic signal canceler (1151-n) which includes: an unwanted traffic signal despreader (1391-n) having a signal input (103) coupled to said system input (63) and a summed output; the unwanted traffic signal despreader (1391-n) comprises an unwanted traffic signal code generator (1191-n) and a mixer (1171-n) for mixing the generator (1191-n) output and the input (103) for outputting of the unwanted traffic signal canceler; the summed output of the unwanted traffic signal despreader is coupled to a hard decision processor (1251-n) having a phase output (phi) and a data output (d); said hard decision processor phase output (phi) coupled to a low pass filter (1271-n), said low pass filter having an output (01pfn); said low pass filter (1271-n) output (0lpfn) coupled to an input of a processor (1291-n) that filters and removes the product of the unwanted traffic signal to desired traffic signal cross-correlation outputting the unwanted traffic signal strength; said processor (1291-n) output multiplied with said hard decision data output (d) with a first multiplier (1311-n) having an output to an adjustable amplifier (1371-n); said unwanted traffic code generator (119) output coupled to an input of a complex conjugate processor (1351-n) having an output; said complex conjugate output mixed with a complex conjugate of the desired traffic signal code by a first mixer (1331-n) having an output; said first mixer (1331-n) output coupled to an input of a first sum and dump processor (1231-n) having an output; said first sum and dump processor (1231-n) coupled to an input of an amplifier (1371-n) having an adjustable gain controlled by said multiplier (1311-n) output; and and said output of said amplifier (1371-n) coupled to an adder (143) which substracts the output (1411-n) of each adjustable amplifier (1371-n) from the output (0sd3) of the desired traffic signal despreader (91) to provide the output (0) of the cancellation system of a traffic signal (101). 3. The cancellation system according to claim 1 wherein said global pilot signal canceler (61) comprises: a global pilot despreader (65) coupled to said input (63) having a summed output (0sd1); a desired traffic signal and global pilot cross-correlation means having an output (0sd2) said global pilot despreader (65) output (0sd1) coupled to a pilot strength determining means, said determining means having an output (0pm); said pilot strength determining means output (0pm) multiplied with said cross-correlation means (85) output; and said multiplied product is the output (0add). 4. The cancellation system according to claim 3 wherein said cross-correlation means comprises: a global pilot signal code generator (69); a desired traffic signal complex conjugate code generator (79); a second mixer (81) for cross-correlating said global pilot signal code and said desired traffic signal complex conjugate code; and a second sum and dump processor (85) for summing over time said cross-correlation product. 5. The cancellation system according to claim 4 wherein said means to derive said global pilot signal strength further comprises: a low-pass filter (75) having an output (01pf); and a processor (77) coupled to said low-pass filter (75) deriving and outputting the global pilot signal strength. 6. A global pilot signal cancellation system (61) for use in a receiver that receives communication signals from a transmitter over a CDMA air interface that removes the global pilot signal from a desired traffic signal prior to decoding, the system comprising: an input (63) for receiving the communication signals and a system output (0add); said input coupled to a global pilot despreader (65) and a desired traffic signal despreader (91) each having a summed output; a desired traffic signal and global pilot cross-correlation means; said global pilot despreader (65) output (0sd1) coupled to a pilot strength determining means, said determining means having an output (0pm); said pilot strength determining means output (0pm) multiplied with said cross-correlation means output (0sd2); and said multiplied product subtracted from said desired traffic signal despreader (91) output (0sd3) outputting (0add) the desired traffic signal free from the global pilot signal. 7. The cancellation system according to claim 6 wherein said means to derive said global pilot signal strength further comprises: a low-pass filter (75) having an output (0pf); and a processor (77) coupled to said low-pass filter (75) deriving and outputting the global pilot signal strength. 8. A cancellation traffic signal system (101) for use in a receiver that receives communication signals from transmitter (19) over a CDMA air interface that removes at least one unwanted traffic signal from a desired traffic signal prior to decoding, the system comprising: an input (103) for receiving the communication signals and a system output (0); said input (103) coupled to a desired traffic signal despreader (91) each having a first summed output (0sd3); at least one unwanted traffic signal canceler (1151-n) comprises: an unwanted traffic signal despreader (1391-n) having an input coupled to said first summed output and a second summed output; said unwanted traffic signal despreader (1391-n) comprises an unwanted traffic signal code generator (1191-n) and a mixer (1171-n) for mixing the generator (1191-n) output and the input (103) for outputting of the unwanted traffic signal canceler; the summed output of the unwanted traffic signal despreader (1391-n) is coupled to a hard decision processor (1251-n) having a phase output (phi) and a data output (d); said hard decision processor (1251-n) phase output (phi) coupled to a low pass filter (1271-n), said low pass filter having an output (01pfn); said low pass filter (1271-n) output (0lpfn) coupled to an input of a processor (1291-n) that filters and removes the product of the unwanted traffic signal to desired traffic signal cross-correlation outputting the unwanted traffic signal strength; said processor (1291-n) output multiplied with said hard decision data output (d) with a first multiplier (1311-n) having an output to an adjustable amplifier (1371-n); said unwanted traffic code generator (1191-n) output coupled to an input of a complex conjugate processor (1351-n) having an output; said complex conjugate output mixed with a complex conjugate of the desired traffic signal code by a (1331-n) having an output; said mixer (1331-n) output coupled to an input of a second sum and dump processor (1231-n) having an output; said second sum and dump processor (1231-n) coupled to an input of an amplifier (1371-n) having an adjustable gain controlled by said multiplier (1311-n) output; and and said output of said amplifier (1371-n) coupled to an adder (143) which substracts the output (1411-n) of each adjustable amplifier (1371-n) from the output (0sd3) of the desired traffic signal despreader (91) for outputting the output (0) of the cancellation system of a traffic signal (101).