230 results about "Code tracking" patented technology

A CDMA modem includes a modem transmitter having: a code generator which provides an associated pilot code signal and which generates a plurality of message code signals: a spreading circuit which produces a spread-spectrum message signal by combining each of the information signals with a respective one of the message code signals; and a global pilot code generator that provides a global pilot code signal to which the message code signals are synchronized. The CDMA modem also includes a modem receiver having an associated pilot code generator and a group of associated pilot code correlators for correlating code-phase delayed versions of the associated pilot signal with a receive CDM signal to produce a despread associated pilot signal. The code phase of the associated pilot signal is changed responsive to an acquisition signal value until a pilot signal is received. The associated pilot code tracking logic adjusts the associated pilot code signal in phase responsive to the acquisition signal so that the signal power level of the despread associated pilot code signal is maximized. Finally, the CDMA modem receiver includes a group of message signal acquisition circuits, each including a plurality of receive message signal correlators which correlate respective local received message code signal to the CDM signal to produce a respective despread received message signal.

A CDMA modem includes a modem transmitter having: a code generator which provides an associated pilot code signal and which generates a plurality of message code signals; a spreading circuit which produces a spread-spectrum message signal by combining each of the information signals with a respective one of the message code signals; and a global pilot code generator that provides a global pilot code signal to which the message code signals are synchronized. The CDMA modem also includes a modem receiver having an associated pilot code generator and a group of associated pilot code correlators for correlating code-phase delayed versions of the associated pilot signal with a receive CDM signal to produce a despread associated pilot signal. The code phase of the associated pilot signal is changed responsive to an acquisition signal value until a pilot signal is received. The associated pilot code tracking logic adjusts the associated pilot code signal in phase responsive to the acquisition signal so that the signal power level of the despread associated pilot code signal is maximized. Finally, the CDMA modem receiver includes a group of message signal acquisition circuits, each including a plurality of receive message signal correlators which correlate respective local received message code signal to the CDM signal to produce a respective despread received message signal.

An M code envelope detector receives an incoming binary offset carrier (BOC) signal, such as the M code signal, and generates inphase BOC and quadraphase BOC signals, separated by an offset, that have respective ambiguous correlation envelopes, that when combined, provide a near unimodal correlation function with respect to code phase error of the BOC signal having an inherent multimodal autocorrelation function, with the near unimodal correlation envelope being tracked by early and late code replicas at broad one chip phases for providing unambiguous but nonlinear code phase error tracking, which detector is then further improved with the use of code replicas having narrow partial chip phases, such as ⅛ chip phases, for providing near linear code phase error tracking for unambiguous and accurate code tracking of the BOC signal.

Disclosed is a code tracking apparatus and method under a multi-path environment in a DS-CDMA communication system. Through the steps of calculating fast path energy on a first path signal by removing an interference signal component from the first path signal, the first path signal being faster than an allocated multi-path signal, calculating slow path energy on a second path signal by removing an interference signal component from the second path signal, the second path signal being slower than the allocated multi-path signal, obtaining information regarding timing of the allocated multi-path signal by using the fast path energy and the slow path energy, and receiving the allocated multi-path signal based on the obtained timing information, it is possible to prevent an occurrence of a fat finger phenomenon in which fingers de-modulating multi-path signals having mutually different time delays track the same path, so that it is possible to obtain a time diversity effect, thereby enhancing the reception of a rake receiver.

The invention is directed to a method for signal processing in a rake receiver for spread spectrum signals and is directed to a rake receiver for spread spectrum signals including a plurality of rake fingers (9, 10, 11) each rake finger being adapted to receive a signal (7, 8) being part of a multipath signal (2) and associated with a path of the multipath, the signal (7, 8) having a delay (τ) relative to an other signal associated with an other path of the multipath (7, 8), the receiver comprises a summation unit (37) for generating an output signal from the signals received from of at least some of the rake fingers (9, 10, 11), the output signal being a summation signal having and improved signal to noise ratio (SNR) if compared with the signal to noise ratio (SNR) of at least, one of the rake fingers (9, 10, 11), a timing error detector (12) for detecting a delay (τ) between signals of at least two rake fingers (9, 10, 11) and for generating a timing error signal which is sent to a unit (6) for compensating the error of the respective delay (τ); to provide a code-tracking unit for a direct-sequence code division multiple access (DS-CDMA) receiver having an improved tracking performance, especially in cases where delay times of multipath signals are in the order of the chip duration the timing error detector (12) generates a timing error signal (x, 13) based on the signals (7, 8) associated with paths of the multipath of more than one rake finger (9, 10, 11).