Slow hopping data transmitter

Details Slow hopping data transmitter Slow hopping data transmitter

1999-06-21

2004-09-21

Nguyen, Chau (Department: 2663)

Multiplex communications

Communication over free space

Having a plurality of contiguous regions served by...

C370S341000

Reexamination Certificate

active

06795410

ABSTRACT:

TECHNICAL FIELD
This invention relates to communication systems. Specifically, the present invention relates to an apparatus and method for coupling data between communication devices.
BACKGROUND ART
Radio communication is widely used for coupling data between electronic devices. Typically, coupling of data between electronic devices includes transmission of “packets” of digital data. Examples of devices that communicate via radio for coupling data include surveying applications, precision farming applications, etc.
In recent years, the number of persons using licensed and unlicensed frequency bands for voice communications has increased dramatically, making these frequency bands crowded, congested and unavailable for use by users that transmit digital data. Also, persons using licensed and unlicensed frequency bands for voice communications tend to communicate during business hours and during certain times of the day. At these times, desirable frequency bands become highly congested, particularly in densely populated areas, making usage for transmission of digital data difficult if not impossible.
There are many distinct radio bands available to users that transmit digital data, starting at 30-50 MHz and extending into the VHF range (220 MHz to 450-470 MHz, and 900 MHz). All available frequency bands with the exception of the 900 MHz band require a license from the Federal Communications Commission (FCC) for permission to operate, and such operation is covered by Part 90 of the FCC rules and regulations. The 450-470 MHz band is authorized for primary use by occasional voice service, on a shared use basis with others in a particular service area. Typical users include taxi dispatch, maintenance and repair dispatch, and other business or government services that need occasional voice service and do not need access to a nationwide telecommunications service.
Most users of available communication channels are required to share the channel with other users. However, users that transmit data such as surveyors typically set up on a work site and start transmitting data packets, that are typically broadcast once per second, with a duration of approximately 0.25-0.4 seconds, until the project is complete. Thus, a particular channel is virtually occupied by the transient user until the project is complete. This can create problems for other users, particularly when a radio channel is used for which there is a local area repeater system. If the data packets are picked up by the repeater system, they are rebroadcast over a much larger area. This renders the particular channel completely useless over a large area. Even if the user's signal is not repeated, the user's strong signal may “capture” the repeater's receiver and thereby prevent voice users from using the repeater.
For the above reasons, a channel formerly used by local voice users can become unusable for the entire time period in which data is transmitted. When an established user, at his base of operations, cannot access the user's mobile fleet in a few seconds, his options are few: wait until the channel clears, or reassign each radio in the fleet to a new channel. This is inconvenient and time consuming for the established user. This also can lead to complaints by the local established users to the FCC for failure to abide by the rules of operation established by the FCC that call for “sharing” the channel.
The FCC requires that voice users listen before they speak to assure that the channel is available. However, in many instances users do not listen for a sufficient amount of time. This often results in voice users talking over a digital data transmitter's transmission. This can result in loss of data. If the voice usage is significant, this may force the user of the digital data transmitter to change to a less congested frequency band.
What is needed is a method and apparatus that will allow for more efficient use of available frequency bands. Also, a method and apparatus is needed that meets the above needs and that does not interfere with voice communication. In addition, a method and apparatus is needed that meets the above needs and that is inexpensive and easy to operate.
DISCLOSURE OF THE INVENTION
The present invention provides an apparatus and method that allows for more efficient use of available frequency bands. The method and apparatus of the present invention provide for coupling data from a first communication device to a second communication device that transmits over unoccupied radio channels. More particularly, the present invention provides a method and apparatus that is inexpensive and easy to operate and that minimizes interference with voice communication.
A first communication device and a second communication device are disclosed that couple data via radio. In one embodiment, the radio is adapted to transmit over unlicensed frequency bands. However, alternatively, licensed bands could be used also.
In operation, the communication device that is sending data, designated as a first communication device, monitors multiple radio channels and generates a channel occupancy map that indicates the occupancy of the monitored channels. A channel selection algorithm is then used for determining available channel(s) and assigning one channel, or a sequence of channels for subsequent communications. In one embodiment, user defined channel preference factors are used in the channel selection algorithm for determining assigned channel(s).
A message is then generated that includes data to be transmitted and that indicates the assigned radio channel(s). The message is transmitted to the second communication device. The first communication device then changes the radio channel to the assigned radio channel or the next radio channel in the assigned sequence of radio channels. The first communication device continues to monitor channel occupancy using subsequently generated channel occupancy maps and updates the assigned radio channel or sequence of radio channels. Each time the assigned radio channel or sequence of radio channels is updated, the updated assigned radio channel or sequence of radio channels is indicated in a message transmitted by the first communication device.
The second communication device receives each message indicating an assigned channel or sequence of assigned channels and moves to the assigned channel or the next assigned channel in the sequence of assigned channels for receiving the next transmission. Thus, the first communication device and the second communication device move from channel to channel, communicating over unoccupied channels.
The method and apparatus of the present invention allows for communication over multiple channels sequentially by moving from channel to channel. By communicating over unoccupied channels, more efficient use of available frequency bands is obtained. In addition, by communicating over unoccupied channels, the method and apparatus of the present invention does not interfere with voice communication. In addition, the method and apparatus of the present invention is inexpensive and easy to operate.
These and other objects and advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiments that are illustrated in the various drawing figures.


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