Telecommunications – Transmitter and receiver at separate stations
Reexamination Certificate
1998-06-25
2001-07-03
Bost, Dwayne (Department: 2681)
Telecommunications
Transmitter and receiver at separate stations
C455S574000, C455S522000
Reexamination Certificate
active
06256476
ABSTRACT:
BACKGROUND
1. Field of the Invention
This invention relates to the field of wireless communication systems. More specifically, the present invention relates to power management by dynamically adjusting the transmission power of mobile stations based upon the quality of received signals by the base station.
2. Background
The use of wireless communication systems is growing with users now numbering well into the millions. One of the most popular wireless communications systems is the cordless telephone, consisting of a mobile unit (or handset) and a base station. Cordless telephones allow a user to talk over the telephone without having to remain in a fixed location. This allows users to, for example, move freely about a house while talking on the phone. However, one inconvenience associated with routine use of a cordless telephone is the constant need to recharge and replace depleted batteries in the handset.
As with any transmitted signal, the quality of the received signals varies based upon a number of factors, including atmospheric conditions, location of the mobile unit, or interference by walls or buildings. If a signal transmitted by the mobile unit has degraded, the base station may be unable to decode and process the signal. This may occur, for example, if the mobile unit is at the outer transmission boundary of the base station.
The power required by the mobile unit to transmit signals to the base station is one of the largest drains on battery power. In an attempt to extend battery life, mobile units are designed to vary the amount of transmission power based upon current needs. For example, a mobile unit located a long distance from the base station needs to transmit signals at a higher power level than a mobile unit near the base station. Current systems adjust the transmission power of the mobile unit based upon signal quality measurements taken over an extended period of time. Once the average signal quality diminishes below a set level, the mobile unit begins transmitting signals at a higher power level. After switching to the higher power level, the signal quality is again measured. If these signal quality measurements are above a threshold for an extended period of time, the base station instructs the mobile unit to switch to a lower power level to conserve battery power. While adjusting the transmission power levels of the mobile unit over extended periods of time has improved battery life, there is always a desire to further extend the useful life of the battery.
Improvements in battery technology, while helpful, have done little to avoid the seemingly ever-present need to recharge and replace mobile unit batteries. What is needed is a system to further conserve battery power by reducing the power consumed by the mobile unit.
SUMMARY
The present invention is directed to reducing power consumed by a mobile unit. The present invention recognizes the largest amount of battery power is consumed during the highest transmission power level of the mobile unit. Therefore, the present invention is directed to minimizing the amount of time the mobile unit transmits at the highest power level.
In one embodiment of the present invention, the base station detects the quality of the signals transmitted by the mobile unit. Based on this signal quality, the base station determines if the mobile unit should increase the transmission power level. If an increase in transmission power is indicated, the base station sends a signal to the mobile unit causing the mobile unit to increase transmission power. However, to save battery power, the mobile unit transmits at the increased power level for a limited amount of time, and then automatically returns to transmitting at the lower power level.
The present invention also recognizes that in certain circumstances, mobile units can transmit at a high power level for long periods of time. By transmitting at a high power level, the mobile unit can function at the outer transmission boundary of the base station. However, the mobile unit often transmits at a high power level without being at the outer transmission boundary. In these situations, where the mobile unit is located away from the base station, yet not near the outer transmission boundary, the highest power level is not necessary. Therefore, the present invention allows the mobile unit to operate at a reduced high power level during these periods.
One embodiment of the invention is a wireless communication system comprising a base station which transmits a first plurality of signals and receives a second plurality of signals. A signal strength detector in the base station determines the quality of at least some of the second plurality of signals received by the base station. When the quality of the signals is below a predetermined threshold, the base station inserts a low power indicator in at least one of the first plurality of signals transmitted by the base station. A mobile unit receives the first plurality of signals transmitted by the base station. The mobile unit is configured to operate at either a first power level or a second power level, where the first power level is higher than the second power level. When the mobile unit receives the low power indicator from the base station, the mobile unit operates at the first power level and after the transmission of a signal, the mobile unit resets to operate at the second power level.
Another embodiment of the invention is a wireless communication unit comprising a receiver configured to receive a first plurality of signals, at least one of the first plurality of signals having a power level command. A transmitter is configured to transmit a second plurality of signals over at least two power levels, where a first power level is greater than a second power level. A processor is connected to the receiver and the transmitter. The processor is configured to control the transmitter so as to vary the power levels of the second plurality of signals. The processor is further configured to select the first power level in response to the power level command and then select the second power level after the transmission of the second plurality of signals.
Another embodiment of the invention is a method of conserving power in a wireless communication system comprising the acts of determining the quality of a first signal received from the mobile unit and comparing the received signal quality to a predetermined value. A second signal is then transmitted from the mobile unit at a first power level when the received signal quality is below the predetermined value. The mobile unit automatically resets to transmit at a second power level following a transmission at a first power level, where the first power level is higher than the second power level.
Another embodiment of the invention is a wireless communication system comprising a signal strength indicator which determines the quality of a signal received from a mobile unit and a power level adjustor which increases the power level of a signal transmitted by the mobile unit for only a predetermined number of transmissions when the signal quality is below a set value.
Another embodiment of the invention is a method of saving power in a communications system which provides for the repeated exchange of signals between a first location and a second location. The method comprises the acts of determining the quality of a first signal transmitted by the first location and transmitting information instructing the first location to increase the transmission power for a second signal to a first power level if the quality of the first signal falls below a predetermined level. The method then resets the transmission power of the first location to a second power level after transmission of the second signal, where the first power level is higher than the second power level. The method then determines the quality of the second signal transmitted by the first location and transmits information instructing the first location to increase the transmission power for a third signal to a first power level if t
Beamish Norman J.
Walley John S.
Bost Dwayne
Conexant Systems Inc.
Gelin Jean A.
Knobbe Martens Olson & Bear LLP
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