User equipment for detecting short codes
A receiver employing CDMA techniques estimates background noise based on a periodically updated code. The transmitted signal includes a periodically updated code of a predetermined type and wherein the received signal has CW interference in addition to the transmitted signal. The decision circuit determines if a value representing the likelihood of detection of the code exceeds a predetermined threshold. In the case of a pilot signal not being detected within a predetermined time period which corresponds to code update period, the background noise estimator obtains a new background estimation.
1. A receiver for receiving a transmitted signal in multiuser spread spectrum wireless telecommunication systems, in which the transmitted signal includes at least one periodically updated code of a predetermined type, the receiver comprising:
a RAKE despreader for despreading at least one sample of said transmitted signal to output at least one despread signal;
a background noise estimator for obtaining a background noise estimation by combining said at least one periodically updated code of the predetermined type with said transmitted signal; and
a decision unit, which receives said despread signal and said background noise estimate, and determines if a value representing the likelihood of detection of the code exceeds a predetermined threshold, wherein in the case of a pilot signal not detected within a predetermined time period corresponding to a period of the periodically updated code, the background noise estimator obtains a new background estimation; wherein obtaining the new background noise estimate results in performing the operations of detecting the code of the predetermined type upon a set of samples having a noise estimation using a same time slot for the code of the predetermined type as the samples.
2. A receiver for receiving a transmitted signal in multiuser spread spectrum wireless telecommunication systems, in which the transmitted signal includes at least one periodically updated code of a predetermined type and a plurality of time slots separated by a plurality of time slot boundaries wherein each time slot includes a time slot update period, the receiver comprising:
a RAKE despreader for despreading at least one sample of said transmitted signal to output at least one despread signal;
a background noise estimator for obtaining a background noise estimation during the timeslot update period by combining said at least one periodically updated code of the predetermined type with said transmitted signal; and
a decision unit, which receives said despread signal and said background noise estimate, and determines if a value representing the likelihood of detection of the code exceeds a predetermined threshold, wherein in the case of a pilot signal not detected within a predetermined time period corresponding to a period of the periodically updated code, the background noise estimator obtains a new background estimation.
3. The receiver of claim 2 , wherein the time slot update period occurs substantially immediately after the time slot boundary.
4. The receiver of claim 3 , wherein said decision unit calculates said value during a selected time slot in accordance with a background noise estimation obtained only during said update period.
5. The receiver of claim 1 , wherein the decision unit calculates a value representing the likelihood of detection of the code of the predetermined type and compares said value with a predetermined threshold; and the decision unit confirms the detection of the code of the predetermined type if said value exceeds said predetermined threshold.
6. The receiver of claim 1 , wherein periodically updating of the code provides an estimation of background noise that closely resembles the actual background noise, in the presence of continuous wave interference.
7. The receiver of claim 1 , wherein the decision unit provides a delay corresponding to the period of the periodically updated code.
8. The receiver of claim 1 , wherein the decision unit further compares said value with a plurality of predetermined thresholds, and at least one of said predetermined thresholds is an acceptance threshold and at least one of said predetermined thresholds is a rejection threshold.
9. The receiver of claim 8 , wherein the transmitted signal has a plurality of signal phases, and the decision unit compares a plurality of values, corresponding to the plurality of signal phases, with the plurality of predetermined thresholds.
10. The receiver of claim 9 , wherein the decision unit advances the signal phase if one of said plurality of values crosses one of said plurality of predetermined thresholds.
11. The receiver of claim 8 , wherein the decision unit advances the signal phase if one of said plurality of values crosses said rejection threshold.
12. The receiver of claim 1 , wherein the decision unit calculates said value in accordance with at least a sample of the output of said RAKE despreader.