Qualcomm Incorporated

Mark Roh

Raghu Narayan Challa

Farrokh Abrishamkar

Inyup Kang

Brendon Lewis Johnson

Avneesh Agrawal

Shimman Arvind Patel

Brian K Butler

Gilbert Christopher Sih

Serguei A Glazko

Ashok Bhatia

Abhay Arvind Joshi

Arthur James Neufeld

Borislav Ristic

Paul R Johnson

Glenn A Salaman

Arie Rahmat

In general, the invention facilitates searching for energy peaks in spread spectrum wireless communication systems with greater precision. More particularly, various embodiments of the invention may involve reporting not only an energy peak and its associated offset, but also the energy levels corresponding to one or more offsets occurring before and after the offset at which the energy peak occurs. Interpolation or extrapolation techniques may be used to predict the actual location of an energy peak based on the apparent location of the peak and the energy levels observed at surrounding offsets.

Interpolation of channel search results

A method and apparatus mitigating the effects of cross-correlation signals on received satellite signals in a Global Positioning System (GPS) receiver is described. MS-Assisted and MS-Based cross-correlation detection and mitigation methods and apparatus are described. A GPS search mode architecture is used to detect SV signals and identify potential cross-correlations. The GPS search modes have different coherent integration lengths and different degrees of sensitivity. After detection, measurements are logged into a database for further processing. Several cross-correlation tests are described. For example, a 'Mainlobe' cross-correlation test is described that identifies the most significant cross-correlations that occur when the Doppler difference between the interfering SV signal and the target SV signal is nonzero and a multiple of 1 kHz. Appropriate C/No and Doppler thresholds, or masks, are selected and used to identify the mainlobe cross-correlations. A wide Doppler mask is used to account for the effects on cross-correlations caused by BPSK data bit modulation. Appropriate MS-Assisted and MS-Based cross-correlation masks are described. Other cross-correlation tests include 'variable C/No', &#x201c;strong&#x201d;, &#x201c;wide Doppler&#x201d; and &#x201c;pre-emptive&#x201d; cross-correlation detection tests.

Cross-correlation mitigation method and apparatus for use in a global positioning system receiver

Systems and techniques are disclosed detecting an embedded signal which includes producing a plurality of first correlated values from a portion of the first signal and a second signal, transforming the first correlation values into a plurality of second correlation values related to a frequency content of the first correlation values, and searching for the embedded signal by evaluating the second correlation values. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or the meaning of the claims.

Acquisition of a gated pilot signal

A wireless remote unit performs SPS acquisition interleaved with receiving paging information over a wireless slotted paging channel and receiving data packets over a wireless data communication system. The remote unit tunes to a pilot channel, synchronizes to an internal clock of the wireless remote unit with a pilot signal transmitted over the pilot channel; and starts a search for SPS satellites after completing synchronization with the internal clock.

Method and apparatus for scheduling search for and acquisition of global positioning satellites

Techniques to acquire the frequency of a signal instance based on a window of data samples covering a time period shorter than the time needed to achieve frequency lock. The window of data samples is initially captured and stored to a sample buffer. A segment of data samples is then retrieved from the sample buffer for processing. The retrieved data samples are rotated by a current frequency error estimate to provide frequency-translated data samples, which are further processed to provide one or more pilot symbols. An updated frequency error estimate for the frequency-translated data samples is then derived based on the pilot symbols using a frequency control loop. The window of data samples is processed for a number of iterations until frequency acquisition is achieved for the signal instance or termination is reached. For each iteration, one segment is processed at a time and typically in sequential order.

Pilot frequency acquisition based on a window of data samples

A system determines if a primary paging channel should be received based on an examination of a quick paging channel. A first QPCH symbol is examined ( ) and the normalized pilot energy is determined ( ). If the normalized pilot energy is above a first threshold ( ), the symbol is demodulated and the QPCH-symbol-to-pilot-energy ratio is determined ( ) and compared against another threshold ( ). If the normalized pilot energy is below the first threshold, the system proceeds to the second QPCH symbol immediately. Depending on the resulting values, a second QPCH signal is examined ( ), the system sleeps ( ), or the system decides ( ) to process the primary paging channel directly ( ). If the second signal is demodulated, and if its normalized pilot energy is high enough, it also is demodulated and the ratio of the sum-of-the-combined-QPCH-symbols to the sum-of-the-combined-pilot-energies is determined ( ). If this ratio exceeds a threshold ( ), the primary paging channel is processed ( ); otherwise the system sleeps ( ).

Quick paging channel demodulation to facilitate offline processing

A system determines if a primary paging channel should be received based on an examination of a quick paging channel. A first QPCH symbol is examined ( ) and the normalized pilot energy is determined ( ). If the normalized pilot energy is above a first threshold ( ), the symbol is demodulated and the QPCH-symbol-to-pilot-energy ratio is determined ( ) and compared against another threshold ( ). If the normalized pilot energy is below the first threshold, the system proceeds to the second QPCH symbol immediately. Based on the two comparisons, a second QPCH signal is examined ( ) or the system sleeps ( ). If the second signal is examined, and if its normalized pilot energy is high enough, it also is demodulated and the ratio of the sum-of-the-combined-QPCH-symbols to the sum-of-the-combined-pilot-energies is determined ( ). If this ratio exceeds a threshold ( ), the primary paging channel is processed ( ); otherwise the system sleeps ( ).

Sequential combined QPCH demodulation

A method and apparatus for frequency tracking is described. The present invention provides a tracking mechanism for removing the effects of error due to frequency offset as well as compensation for frequency error due to doppler in a plurality of multipath signals. Each finger of a RAKE receiver utilizing the present invention will compute a frequency error for that finger. The weighted average of all of these frequency errors is calculated and filtered to provide a control signal for varying the frequency of IF and RF frequency synthesizers, accounting for the common frequency offset seen at each finger. Additionally, each finger is equipped with a rotator for providing frequency adjustment specific to that finger. The frequency of each finger is adjusted through feedback of the frequency error for that finger.

Multipath doppler adjusted frequency tracking loop

A system for facilitating the detection and successful decoding of a quick paging channel adapted for use with a wireless communications system supporting a primary paging channel and a quick paging channel. The system includes a first mechanism for detecting a pilot signal associated with the quick paging channel based on a received signal and includes a coherent integrator of a first length and a noncoherent integrator of a second length. The second mechanism determines receiver operating characteristics of the system based on the pilot signal and a quick paging channel signal associated with the quick paging channel. The third mechanism optimizes the first length and the second length based on the receiver operating characteristics. In a specific embodiment, the first mechanism includes a CDMA receive chain for receiving the received signal and providing a digital received signal in response thereto to a sample Random Access Memory (RAM). The sample RAM includes a mechanism for sampling the digital received signal at predetermined time slots and providing a sampled received signal in response thereto. An interpolator adjusts the rate of the sampled received signal and provides a rate-adjusted signal in response thereto. The first mechanism includes a searcher that includes the first coherent integrator, a second coherent integrator, and the noncoherent integrator. A complex despreader correlates the rate-adjusted received signal with a pseudo noise candidate code and providing a correlation result in response thereto.

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San Diego, CA, United States of America

Mark Roh