METHOD AND APPARATUS FOR SYMBOL SYNCHRONIZATION FOR AN 802.15.4 RADIO PLATFORM

• US 20090168849A1
• Filed: 03/31/2008
• Published: 07/02/2009
• Est. Priority Date: 12/31/2007
• Status: Active Grant

• Current Assignee: Silicon Laboratories Incorporated
• Original Assignee: Silicon Laboratories Incorporated
• Inventors: ROUXEL, ALEXANDRE
• Granted Patent: US 8,223,820 B2
• Time in Patent Office: Days
• US Class Current: 375/140
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 2201/70709 with discontinuous detection
• CPC Class Codes: H04J 13/00 Code division multiplex systems for frequency hopping H04B1/713
• CPC Class Codes: H04L 27/2278 using correlation techniques, e.g. for spread spectrum signals

Abstract

A single chip radio platform is disclosed for communicating with an RF channel. An RF front end is provided having a receive/transmit capability to receive an RF carrier modulated with digital data and convert the data to analog baseband data, and modulate an RF carrier with baseband data. A digital signal processor (DSP) engine is provided for interfacing with the RF front end to form in conjunction therewith the PHY layer, and interfacing with the MAC layer to demodulate the baseband data and in the transmit mode to generate the baseband data for modulation and transmission by the RF front end. A microcontroller unit (MCU) is provided for performing the functionality of the MAC, network and application layers and interfacing with the DSP. Clock circuitry is provided including a stable reference clock for generating a first fixed clock for providing MCU clocks for the operation of the MCU, and for providing a reference for a local oscillator at substantially the channel frequency for use by the RF front end and a DSP clock for use by the DSP, both the MCU clocks, the local oscillator and the DSP clock having the stability of the first fixed clock. Periodic power management circuitry is provided for controlling the operation of the radio platform to operate in a sleep.

Claims

1. A method for receiving a data stream including a spreading sequence packet of information containing a data payload and, in addition to the data payload, packet overhead including at least periodic information and at least one unique section of known coded information that defines a unique position within the packet, comprising:

performing a plurality of processing steps to detect the position of the unique section within the packet of information including the steps of;

detecting the periodicity of the periodic information in a first processing step,

in a second processing step after periodicity in the received data stream has been determined, estimating the position of the unique section within the packet of information, and

in a third processing step, correlating the information in the packet of information about the estimated position with the known coded information.

2. The method of claim 1, and further comprising the step of indicating to a data processing step the position of unique section within the packet of information.

3. The method of claim 2, wherein the position of the unique section precedes the data payload.

4. The method of claim 2, wherein the data processing step comprises a demodulation operation.

5. The method of claim 1, further comprising the step of serially storing the data in a plurality of buffers arranged in a circular buffer configuration such that while data is being loaded into one of the buffers, data in the remaining buffers can be processed in at least one of the plurality of processing steps.

6. The method of claim 5, wherein each of the processing steps is carried out in a processing engine.

7. The method of claim 6, wherein the processing engine is normally in an idle mode such that is does not absorb a significant amount of power and the step of storing is operable to activate the processing engine after each buffer is full to initiate a select one of the processing steps in accordance with a predetermined sequence thereof, wherein each of the processing steps comprises a task that is executed by the processing engine and the processing engine terminates operation prior to the time it takes to fill a buffer.

8. The method of claim 6, wherein each of the processing steps is comprised of one or more of a plurality of separate tasks and the processing steps occur in a predetermined sequence.

9. The method of claim 8, wherein the processing engine is switched to an idle mode of operation prior to or at the end of the operation of filling a buffer and wherein initiation of storing data in the next buffer will operate the processing engine in a processing mode to execute the then current task within the then current processing task.

10. The method of claim 9, wherein a task can extend across a buffer boundary such that the task is only partially complete when the processing engine is switched to the idle mode of operation such that processing of the task is terminated at a known point therein and the task is commenced at the known point therein when the processing engine is again activated when storing of data in the next buffer is initiated.

11. A method for receiving a data stream a single packet of data modulated with a spreading sequence of chips that includes a data payload and, in addition to the data payload, packet overhead including at least periodic information and at least one unique section of known coded information that defines a unique position within the packet of data the data stream, comprising the steps of:

sampling the data stream at a sampling rate;

storing the samples in a plurality of buffers arranged in a circular buffer such that data is continually stored in one buffer in a substantially continuous manner;

processing data stored in the buffers with the exception of the one thereof having data stored therein;

determining when at least a portion of the periodic information is received;

predicting based on information contained within the periodic information the position of the unique section within the buffer or, if not already in the buffer to a future position within the buffer;

correlating the stored data to the time when the unique section is expected.