Distributed Sigma-Delta Sensor Network

• US 20080211704A1
• Filed: 03/02/2007
• Published: 09/04/2008
• Est. Priority Date: 03/02/2007
• Status: Active Grant

• Current Assignee: Unwired Planet LLC (JP Morgan Chase & Co)
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Cairns, Douglas A.
• Granted Patent: US 7,456,770 B2
• Time in Patent Office: Days
• US Class Current: 341/157
• CPC Class Codes: H03M 3/462 Details relating to the decimation process decimation filters in general H03H17/0416, H03H17/0621
• CPC Class Codes: H03M 3/468 Interleaved, i.e. using multiple converters or converter parts for one channel, e.g. using Hadamard codes, pi-delta-sigma converters
• CPC Class Codes: H04Q 9/00 Arrangements in telecontrol or telemetry systems for selectively calling a substation from a main station, in which substation desired apparatus is selected for applying a control signal thereto or for obtaining measured values therefrom

Abstract

The sensor network described herein uses a distributed sigma-delta converter, where each of a plurality of sensor nodes includes a sigma-delta modulator communicatively coupled to a remotely located sigma-delta processor in a control hub. Each sensor node generates a serial bit stream representative of a sensor output signal. The control hub includes a plurality of signal processors, each of which receive and digitally process the serial bit stream wirelessly transmitted by a corresponding sensor node. A controller in the control hub analyzes the digital output from each signal processor to determine one or more characteristics of the sensor network.

Claims

1. A sensor node for a sensor network comprising:

a sampling circuit configured to oversample an input signal at a predetermined sample rate;

a sigma-delta modulator configured to generate a serial bit stream based on the oversampled input signal; and

a communication circuit to transmit said serial bit stream to a remote sigma-delta processor.

2. The sensor node of claim 1 wherein the sigma-delta modulator comprises:

a summing node to generate an error signal based on the input signal and a feedback signal;

an integrator to generate an integrated signal based on the error signal; and

a quantizer configured to quantize the integrated signal to generate the serial bit stream.

3. The sensor node or claim 2 further comprising a digital-to-analog converter to convert said serial bit stream into analog form to generate said feedback signal.

4. The sensor node of claim 1 wherein the sigma-delta modulator comprises a first order sigma-delta modulator.

5. The sensor node of claim 1 further comprising a sensor to generate the input signal.

6. The sensor node of claim 5 wherein the sensor comprises one of a motion sensor, audio sensor, temperature sensor, humidity sensor, wind sensor, pressure sensor, vibration sensor, chemical sensor, and light sensor.

7. A method of providing digital data from a sensor node to a control hub of a sensor network, the method comprising:

oversampling a sensor node input signal at a predetermined sample rate to generate an oversampled signal;

performing sigma-delta modulation on the oversampled input signal to generate a serial bit stream; and

transmitting said serial bit stream to a remote sigma-delta processor in the control hub.

8. The method of claim 7 wherein performing sigma-delta operations comprises:

generating an error signal based on the input signal and a feedback signal;

generating an integrated signal based on the error signal; and

quantizing the integrated signal to generate the serial bit stream.

9. A control hub communicatively coupled to a plurality of sensor nodes in a sensor network, said control hub comprising:

a plurality of sigma-delta processors, each of said sigma-delta processors corresponding to a sigma-delta modulator in one of the sensor nodes and configured to generate an output signal based on a serial bit stream received from a corresponding sensor node; and

a controller configured to analyze the output signals from each sigma-delta processor to determine one or more characteristics of the environment of said sensor network.

10. The control hub of claim 9 wherein each sigma-delta processor comprises a filter configured to:

lowpass filter the serial bit stream received from the corresponding sensor node; and

decimate the filtered bit stream to generate the output signal.

11. The control hub of claim 9 wherein each sigma-delta processor comprises:

a filter configured to lowpass filter the serial bit stream received from the corresponding sensor node; and

a decimator configured to decimate the filtered bit stream to generate the output signal.

12. The control hub of claim 9 wherein each sigma-delta processor further comprises a communication circuit to receive the serial bit stream from the corresponding sensor node.

13. The control hub of claim 9 further comprising one or more communication circuits configured to receive the serial bit streams from each sensor node and to provide each bit stream to the corresponding sigma-delta processor.

14. A method of digitally processing digital data provided by a plurality of sensor nodes in a sensor network, the method comprising:

receiving a plurality of serial bit streams from corresponding sensor nodes in the sensor network;

performing separate sigma-delta processing operations on each of said received serial bit streams to generate an output signal; and

analyzing the output signals to determine one or more characteristics of the environment of the sensor network.

15. The method of claim 14 wherein performing separate sigma-delta processing comprises:

filtering the serial bit stream received from a corresponding sensor node; and

decimating the filtered bit stream to generate the output signal.

16. A sensor network comprising:

a plurality of sensor nodes, wherein each sensor node comprises a sigma-delta modulator configured to generate a serial bit stream based on an oversampled sensor input signal; and

a control hub communicatively coupled to the plurality of sensor nodes and comprising a plurality of sigma-delta processors, wherein each sigma-delta processor is configured to generate an output signal based on the serial bit streams received from a corresponding sensor node.

17. The sensor network of claim 16 wherein each of said sensor nodes further comprises:

a sampling circuit configured to oversample the input signal at a predetermined sample rate to generate the oversampled input signal; and

a communication circuit to transmit said serial bit stream to the corresponding sigma-delta processor in the control hub.

18. The sensor network of claim 16 wherein the control hub further comprises a controller configured to analyze the output signals from each sigma-delta processor to determine one or more characteristics of the environment of said sensor network.

19. A method of processing signals in a sensor network comprising a plurality of sensor nodes communicatively coupled to a control hub, the method comprising:

performing sigma-delta modulation on oversampled input signals to generate a serial bit stream at each sensor node;

transmitting each serial bit stream to a remote sigma-delta processor in the control hub;

performing separate sigma-delta processing operations on each serial bit stream received at the control hub to generate an output signal corresponding to each sensor node; and

analyzing the output signals to determine one or more characteristics of the environment of the sensor network.

20. A distributed sigma-delta converter comprising:

a sigma-delta modulator configured to generate a serial bit stream based on an oversampled input signal; and

a sigma-delta processor remotely located from the sigma-delta modulator and communicatively coupled to the sigma-delta modulator via a wireless link, wherein the sigma-delta processor is configured to process the serial bit stream received from the sigma-delta modulator to generate an output signal representative of the input signal.