Low -cost two-stage receiver system for DS-CDMA
AssigneeMotorola, Inc.
InventorsQicai Shi, Stephen R. Korfhage
Life of this patent
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Abstract
A method and apparatus for receiving and processing a DS-CDMA signal in accordance with a two-stage process. The first stage comprises signal detection and employs a correlation between the sampled incoming waveform and a pseudo-noise code sequence. This stage is performed in real-time. Once a signal has been detected, a burst of the sampled incoming waveform is collected and then post-processed to recover the incoming information. The method may be implemented at low-cost on a general-purpose digital signal processor. The invention is especially suitable for DS CDMA location systems, where low-cost and low power consumption are desirable.
Claims26
A method for receiving a DS-CDMA signal having in-phase and quadrature component waveforms each modulated by a pseudo-noise code of length M chips so that M chips, with each chip of the M chips having one or more data samples that are each comprised of one or more quantized bits, represent one information bit, said method comprising:
- converting said in-phase component waveform into a first sequence of data samples;
- converting said quadrature component waveform into a second sequence data samples;
- selecting one or more data samples of each of the M chips and one or more quantized bits from each selected data sample from the first or second sequence of data samples to obtain a data sequence;
- processing said data sequence to determine if a signal is present in the DS-CDMA signal;
- and if a signal is present:
- collecting a predetermined number of samples from said first and second sequences of data samples;
- and
- decoding a predetermined number of samples from said first and second sequences of data samples to recover information from the DS-CDMA signal.
A computer readable medium containing instructions which, when executed on a computer, carry out a process of receiving a sampled DS-CDMA signal, said process comprising:
- causing one or more data samples of each of M chips and one or more quantized bits from each selected data sample of the sampled DS-CDMA signal to be stored in a first memory as a data sequence, said data sequence being representative of an in-phase or quadrature component of the sampled DS-CDMA signal;
- retrieving said data sequence from said first memory;
- processing said data sequence to determine if a signal is present in the DS-CDMA signal;
- and if a signal is present:
- causing a predetermined number of samples of the DS-CDMA signal to be stored in a second memory;
- retrieving said predetermined number of samples of the sampled DS-CDMA signal from said second memory;
- and
- decoding said predetermined number of samples of the sampled DS-CDMA signal to recover information from the sampled DS-CDMA signal.
A device for processing a sampled DS-CDMA signal, wherein the device is directed by a computer program that is embedded in at least one of:
- (a) a memory;
- (b) an application specific integrated circuit;
- (c) a digital signal processor;
- and
- (d) a field programmable gate array, and the computer program, when executed, carries out the process of:
- causing a plurality of data samples of each of M chips and a plurality of quantized bits from each selected data sample of the sampled DS-CDMA signal to be stored in a first memory as a data sequence, said data sequence being representative of an in-phase or quadrature component of the sampled DS-CDMA signal;
- retrieving said data sequence from said first memory;
- processing said data sequence to determine if a signal is present in the sampled DS-CDMA signal;
- and if a signal is present:
- causing a predetermined number of samples of the sampled DS-CDMA signal to be stored in a second memory;
- retrieving said predetermined number of samples of the sampled DS-CDMA signal from said second memory;
- and
- decoding a predetermined number of samples of the sampled DS-CDMA signal to recover information from the sampled DS-CDMA signal.
Dependencies are inferred from the claim text.