Multiplex communications – Duplex – Communication over free space
Reexamination Certificate
1999-09-01
2003-12-02
Nguyen, Chau (Department: 2663)
Multiplex communications
Duplex
Communication over free space
C455S522000
Reexamination Certificate
active
06657976
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention is directed, in general, to wireless communication systems and methods of operating the same and, in particular, to systems and methods for controlling the transmitter power of an advance wireless messaging device in a narrowband wireless messaging network.
BACKGROUND OF THE INVENTION
The demand for better and cheaper wireless communication services and equipment continues to grow at a rapid pace. Much of this growth is spurred by the Federal Communication Commission's (“FCC”) approval of certain frequency bands for the next generation of Personal Communication Service (“PCS”) devices that provide advanced voice and/or data messaging services, as well as voice telephone services. A relatively small portion of the available frequency bands was set aside for narrowband PCS (“NPCS”) to encourage efficient use of the available spectrum. There are a number of well-known wireless communication techniques that attempt to maximize the efficiency with which the available spectrum is used. These methods include frequency division multiple access (“FDMA”), time division multiple access (“TDMA”), code division multiple access (“CDMA”), and the like. The term “multiple access” means that multiple subscribers (or users) are able to communicate simultaneously with each of these systems.
In general, the infrastructure of a messaging system is somewhat different than cellular telephone systems. For instance, in a NPCS messaging system, all of the base station transmitters throughout a wide coverage area are synchronized and simultaneously broadcast (i.e., simulcast) a message in a forward-channel to a wireless subscriber communication unit (e.g., portable message pagers, fixed messaging or telemetry devices, etc.). This simulcast increases the likelihood that the transmitted message will reach the device even through obstacles, such as buildings, trees, overpasses, and the like. Likewise, the subscriber communication units are capable of transmitting messages in a reverse-channel to numerous receivers associated with the base stations. However, the messaging system does not assign the subscriber to a particular cell and does not transmit to the subscriber only in one cell, as in the case of a cellular telephone system.
Telemetry systems, broadly stated, are communication systems that transmit “status” information from a remote process, function, or device (collectively, “telemetry application”) to a central control facility. Telemetry systems may be used in lieu of maintenance workers to remotely monitor a given telemetry application, such as a utility meter, security system, vehicle locator, environmental monitor, vending machine, medical equipment, oil drilling equipment, and the like.
In many wireless messaging systems, particularly telemetry systems, it is crucial that data be transmitted to and received from the subscriber wireless messaging device in a reliable manner. However, a wireless messaging device often fails to receive an incoming message the first time it is transmitted to the wireless messaging device. Similarly, a base station often fails to receive an incoming message from a wireless messaging device the first time the wireless messaging device transmits it. When the transmitting device does not receive an acknowledgment (ACK BACK) message, the solution is to retransmit the message from the base station (or the subscriber wireless messaging device) until it is finally received at the destination.
Unfortunately, the retransmission process is time consuming. This is detrimental to data systems, particularly telemetry devices, that rely on wireless messaging to transmit and/or receive, for example, alarms, warning messages, critical measurements or operating. parameters, and the like. Frequently, transmitted messages are missed because of a high level of data traffic “noise” in the operating frequencies of the base station and/or the wireless. messaging device. For example, during certain busy times of day, there may be so much data traffic transmitted to a base station that an ACK BACK message from a subscriber wireless messaging device may not be received. Similarly, if the subscriber wireless messaging device initiates a transmission, such as in a two-way messaging. system, the base station may not receive the message if the level of data traffic from other subscriber wireless messaging devices is high. This is particularly true if the subscriber wireless messaging device is remote from the base station.
Therefore, there exists a need in the art for improved wireless messaging networks that can deliver wireless messages during periods of high data traffic. More particularly, there is a need in the art for wireless messaging systems that can transmit messages to a base station from a subscriber wireless messaging device with a high degree of reliability and with a minimum number of message re-transmissions.
SUMMARY OF THE INVENTION
To address the above-discussed deficiencies of the prior art, it is a primary object of the present invention to provide a reverse channel power controller for use in a narrowband. wireless messaging network comprising a plurality of base stations capable of communicating with a plurality of subscriber communication devices. The reverse channel power controller controls a transmission power of a selected one of the plurality of subscriber communication devices. In an advantageous embodiment of the present invention, the reverse channel power controller comprises: 1) a reverse channel traffic determination circuit for determining a level of reverse channel traffic received by a selected one of the plurality of base stations; and 2) a communication controller for transmitting to the selected subscriber communication device a power control command capable of causing the selected subscriber communication device to adjust a power level of a reverse channel signal transmitted by the selected subscriber communication device.
In one embodiment of the present invention, the reverse channel power controller further comprises detection means for detecting a status signal intermittently transmitted by the selected subscriber communication device.
In another embodiment of the present invention, the communication controller transmits the power control command to the selected subscriber communication device if the status signal is not detected by the detection means.
In still another embodiment of the present invention, the communication controller transmits the power control command to the selected subscriber communication device if a power level of the status signal detected by the detection means is low.
In yet another embodiment of the present invention, the reverse channel traffic determination circuit determines the level of reverse channel traffic received by the selected base station by monitoring at least one received signal strength indicator (RSSI) data associated with the selected base station.
In a further embodiment of the present invention, the reverse channel traffic determination circuit determines the level of reverse channel traffic received by the selected base station by using reverse channel traffic pattern data stored in a memory associated with the reverse channel power controller.
In a still further embodiment of the present invention, at least one of the reverse channel traffic pattern data is associated with a selected time of day.
The foregoing has outlined rather broadly the features and technical advantages of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features and advantages of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they may readily use the conception and the specific embodiment disclosed as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent c
Kwoh Jasper
Nguyen Chau
WebLink Wireless, Inc.
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