Telecommunications – Transmitter and receiver at separate stations – Plural transmitters or receivers
Reexamination Certificate
1998-09-30
2001-02-06
To, Doris H. (Department: 2682)
Telecommunications
Transmitter and receiver at separate stations
Plural transmitters or receivers
C455S069000
Reexamination Certificate
active
06185432
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. Field of the Invention
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 on the horizon.
One design goal of hand-held communication devices is that of low power consumption. Low power consumption provides lower heat generation and extended battery life 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. Nos. 5,383,219, entitled “
Fast Forward Link Power Control In A Code Division Multiple Access System,”
issued Jan. 17, 1995; 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 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 the signal-to-noise ratio (SNR) falling 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 SNR and communications quality.
With some systems, such as cellular 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 communication 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 the received communication signals is well within acceptable limits, the base station commands the device to decrease transmitter power.
SUMMARY OF THE INVENTION
The present invention is a novel and improved system and method for dynamically selecting a mode of power control for a communication device. According to the invention, two modes are provided for controlling power of the transmitter as well as a technique for selecting the appropriate mode depending on the operating conditions.
The two modes of controlling power are termed “tracking mode” and “burst mode.” In tracking mode, power is incrementally increased when the SNR is below an acceptable level. In burst mode, power is also increased when the SNR is below an acceptable level. However, in the burst mode, the power increase is greater than the increase applied in the tracking mode. Thus, tracking mode is best suited for handling minor perturbations in SNR as it varies above and below the threshold level. In contrast, burst mode is best suited for handling situations where the SNR falls significantly below the acceptable level, such as when the transmission path is obstructed, such as by a building, for example.
Selection between the two modes is accomplished based on system performance. If the system is operating nominally, the preferred mode of power control is the tracking mode. If, however, the system performance is degraded below a nominal range, the power control mode is switched to the burst mode.
In one embodiment, system performance is based on the SNR of a transmitted signal. Specifically, in one mode of this embodiment, the SNR of a signal received at a transceiver is compared with a predetermined threshold level. When the SNR is at or near the threshold, the system is performing nominally. However, when the SNR falls below a certain level, performance is below nominal.
In another embodiment, a determination of system performance is based on a number errors in the data being received. This can be determined based on a number of frames received with errors, the bit error rate (BER) of the received signal, or other error tracking techniques.
One advantage of the invention is that the amount of time between the occurrence of a signal dropout and a subsequent recovery is reduced. Because system performance is monitored and the amount by which power is increased is determined accordingly, power increases are greater where conditions warrant. As a result, system performance can be returned to within nominal bounds or desired limits in a much shorter period of time than would otherwise be the case if the amount of power increase were to remain constant.
Further features and advantages of the present invention, as well as the structure and operation of various embodiments of the present invention, are described in detail below with reference to the accompanying drawings.
REFERENCES:
patent: 5333175 (1994-07-01), Ariyavisitakul et al.
patent: 5383219 (1995-01-01), Wheatley, III et al.
patent: 0330166 (1989-02-01), None
patent: 0548939 (1992-12-01), None
patent: 0709973 (1996-05-01), None
patent: 2301737 (1996-12-01), None
Ogrod Gregory D.
Qualcomm Incorporated
To Doris H.
Wadsworth Phillip T.
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