Spread-spectrum receiver with progressive fourier transform

• US 8,594,153 B2
• Filed: 04/24/2007
• Issued: 11/26/2013
• Est. Priority Date: 02/28/2000
• Status: Active Grant

• Current Assignee: Comtech Mobile Datacom Corporation (Comtech Telecommunications Corporation)
• Original Assignee: Comtech Mobile Datacom Corporation (Comtech Telecommunications Corporation)
• Inventors: McDermott, Scott A.
• Primary Examiner(s): PHU, PHUONG M
• Application Number:
  US11/739,377
• Publication Number:
  US 20120069870A1
• Time in Patent Office: 2,408 Days
• Field of Search: 375140-153, 375/343, 370/342, 370/320, 370/335, 370/441
• US Class Current: 375/146
• CPC Class Codes: H04B 1/7075 with code phase acquisition
• CPC Class Codes: H04B 1/7087 Carrier synchronisation aspects
• CPC Class Codes: H04L 5/0023 Time-frequency-space

Abstract

A receiving system dynamically searches the communications band for transmissions of messages having the same nominal communications parameters, including the use of the same spreading code, but having potentially different specific frequencies and code-phases. The receiver, which is independent of the transmitters, samples the communications band at each code-phase of the spreading code over a span of downconverted transmission frequencies. When a message element is detected at a particular code-phase and frequency, it is forwarded to a demodulator that demodulates the message and sends it to its intended destination. In a preferred embodiment, a progressive Fourier Transform is used to incrementally determine the power level at each successive code-phase at a given frequency, thereby substantially reducing the time required to search for transmissions at each discrete code-phase.

Claims

1. A communications system comprising:

a plurality of reporting devices,

each reporting device including;

a data collection device that is configured to determine a state of one or more sensors, and

a transmitter that is configured to transmit the state of the one or more sensors about a nominal frequency that is common to the plurality of reporting devices using a spreading code that is common to the plurality of reporting devices;

wherein

a code-phase of the spreading code used at each transmitter is independent of the code-phase used at other transmitters of the plurality of devices,

actual transmission frequencies used by the transmitters of the plurality of reporting devices differ pseudo-randomly about the nominal frequency, and

each transmitter is configured to transmit the state of the one or more sensors at a rate and duration that are selected to, provide a low likelihood of collision with transmissions from the other transmitters, thereby facilitating discrimination of receptions of the state of the one or more sensors of the plurality of reporting devices at a receiving system that operates asynchronous to any of the transmitters, based on energy detected at each reception frequency and code-phase corresponding to each non-colliding transmission.

2. The communication system of claim 1, including

the receiving system, which is configured to distinguish the receptions by determining energy content at each of a plurality of reception frequencies and each of a plurality of code-phases.

3. The communication system of claim 2, wherein

the transmissions from the transmitters are configured to be received by a satellite system and relayed to the receiving system.

4. The communication system of claim 3, including

the satellite system.

5. The communication system of claim 2, wherein

the receiving system is configured to report an alarm condition based on the state of the at least one sensor.

6. The communication system of claim 1, wherein

the reporting devices are configured to be attached to a cargo container, and at least one of the sensors is configured to provide information that facilitates determination of a location of the cargo container.

7. The communication system of claim 6, wherein

another of the sensors is configured to provide information that facilitates determination of intrusion into the cargo container.

8. The communication system of claim 1, wherein

the reporting devices are configured to be attached to an item of property, and at least one of the sensors is configured to provide information that facilitates determination of a location of the item.

9. The communication system of claim 1, wherein

the reporting devices are configured to be attached to a portal, and at least one of the sensors is configured to provide information that is indicative of trespass via the portal.

10. The communication system of claim 1, wherein

at least one of the sensors is configured to detect location parameters.

11. The communication system of claim 1, wherein

at least one of the sensors is configured to detect an amount of flow.

12. The communication system of claim 11, wherein

the flow corresponds to at least one of:

a flow of electricity,

a flow of liquid,

a flow of gas,

a flow of objects, and

a flow of traffic.

13. The communication system of claim 1, wherein

at least one of the sensors is configured to detect pressure.

14. The communication system of claim 1, wherein

at least one of the sensors is configured to detect anomalous conditions.

15. The communication system of claim 1, wherein

the rate of transmission of the state is selected based on an intended use of the sensor, such that occurrences of collisions that prevent each state of the sensor from being determined at the receiving system are substantially inconsequential.