Telecommunications – Transmitter and receiver at separate stations – Plural transmitters or receivers
Reexamination Certificate
1998-09-30
2001-07-10
To, Doris H. (Department: 2682)
Telecommunications
Transmitter and receiver at separate stations
Plural transmitters or receivers
C455S069000
Reexamination Certificate
active
06259928
ABSTRACT:
BACKGROUND OF THE INVENTION
I. Field of the Invention
The present invention relates generally to wireless communication systems. More particularly, the present invention relates to a novel and improved system and method of power control for a wireless communication device.
II. Related Art
Wireless communication networks are enjoying notable popularity in all aspects of business, industry and personal life. As such, portable, hand-held wireless communication devices have experienced widespread growth in recent years. Portable devices such as cellular and Personal Communication Services (PCS) phones are now commonplace for business and personal users alike. Additionally, advanced systems, such as satellite communications systems using portable, hand held and mobile phones, are currently being designed.
One design goal of hand-held communication devices is that of low power consumption. Low power consumption provides extended battery life and lower heat generation which increases device usefulness. Often times, lower power consumption also allows for or leads to smaller device sizes.
In CDMA communication systems, the transmitted power of signals within the system is controlled so as to maintain the amount of power required for any given communication link at a minimum level. This serves to maximize overall communication system capacity and maintain acceptable levels of mutual interference and signal quality. By controlling the transmitted signal power at or near the minimum level, interference with other communication devices or units is reduced. Examples of techniques for power control in such communication systems are found in U. S. Pat. No. 5,383,219, entitled “Fast Forward Link Power Control In A Code Division Multiple Access System,” issued Jan. 17, 1995; U.S. Pat. No. 5,396,516, entitled “Method And System For The Dynamic Modification Of Control Parameters In A Transmitter Power Control System,” issued Mar. 7, 1995; and U.S. Pat. No. 5,267,262, entitled “Transmitter Power Control System,” issued Nov. 30, 1993, which are incorporated herein by reference.
One technique for decreasing the amount of power consumed by the device is to minimize the amount of power in the transmitted signal. Often times, this is accomplished by decreasing the amount of power in the transmitted signal as much as possible without adversely affecting the communication. One way in which this is accomplished is to decrease the amount of power as much as possible without allowing the signal-to-noise ratio (SNR) to fall below an acceptable level. When the SNR falls below the acceptable level, the power is increased to bring the SNR back up to an acceptable level.
This approach is advantageous because it allows a minimum amount of power to be used for communications under optimum conditions. When operating in less than optimum or ideal conditions, that is, inside a building, in bad weather, or such, transmission power is increased to maintain acceptable communications (for example, to maintain an acceptable SNR).
With some systems, such as cellular communications systems or other wireless communications systems for example, the wireless communication device, that is, a cellular phone, is controlled remotely. That is, part of the communication bandwidth between the device and a base station transceiver is dedicated to transferring command and status information. This command and status portion of the bandwidth is used to adjust the power of signals transmitted by the device. When the SNR of signals received by a base station falls below an acceptable level, the base station sends a command to the wireless device to increase its transmitted power. Similarly, if the SNR of received signals is well within acceptable limits, the base station commands the device to decrease transmitter power.
Most conventional systems, however, are limited in the manner in which they control the transmitter power for the wireless communication device. What is needed is a system and method for optimizing power control in a wireless communication system.
SUMMARY OF THE INVENTION
The present invention is a novel and improved system and method for optimizing the setting of a threshold level used to control power of a transmitter in a communication system. According to the invention, two parameters are used to determine whether or not the threshold level needs to be adjusted. These parameters are the operation of the system as compared to an established threshold and the performance of the system.
According to the invention, if the performance of the system is degraded and the system is operating at threshold, this is an indication that the threshold needs to be increased. As such, the invention increases the threshold. Accordingly, the power control portion of the communication system senses that the system is operating below threshold (i.e., the newly-increased threshold) and increases the system power according to a power control mode. As a result, the performance of the system is improved. If the performance is still degraded and the system is again operating at the new threshold, the threshold is increased further. This process continues until the system performance is once again returned to an acceptable level.
Note that if the performance of the system is degraded and the system is operating below threshold, this is an indication that the threshold does not need to be adjusted and that the power of the transmitter needs to be increased to bring the system up to threshold. In one embodiment, this is accomplished by increasing the power of the transmitter according to the power control mode of the communication system.
If system performance is better than required, this is an indication that the power of the transmitter may be greater than needed. Where the system performance is better than required, the invention determines if the system is operating above threshold. If so, the power of the transmitter is decreased according to the power control mode of the communication system. However, if the performance is better than required and the system is operating at or below threshold, this is an indication that the threshold can be lowered. As such, the invention lowers the threshold. Accordingly, the power control portion of the communication system senses that the system is operating above threshold and decreases the system power according to a power control mode. As a result, the power consumption of the transmitter is decreased. If the performance is still better than required and the system is still operating at or below the new threshold, the threshold is decreased further. This process continues until the system performance is once again returned to a normal level.
Note that if the performance of the system exceeds requirements and the system is operating above threshold, this is an indication that transmitter power should be lowered and that the threshold will likely not require adjustment.
In one embodiment, the threshold determinations are based on the signal-to-noise ratio (SNR) of the received signal at the receiver. A desired SNR level is established as the threshold level. The actual SNR of the received signal is compared to the threshold SNR to determine the operation of the system with respect to threshold.
In one embodiment, system performance is determined based on the error rate of the system. In alternative embodiments other metrics are used to determine system performance such as frame errors, bit error rate, or some other indication of system performance.
An advantage of the invention is that power consumption is reduced as a result of the dynamic adjustment of the threshold. Lowering the threshold where signal quality is high allows the system to reduce transmitter power thereby reducing power consumption. Increasing the threshold where the signal quality is degraded allows the system to maintain an acceptable level of performance.
The features, objects, and advantages of the present invention will become more apparent from the detailed description set forth below when taken in conjunction with the drawings
Ogrod Gregory D.
Qualcomm Inc.
To Doris H.
Wadsworth Phillip R.
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