Multiplex communications – Communication over free space – Combining or distributing information via code word channels...
Reexamination Certificate
2000-04-27
2001-12-11
Patel, Ajit (Department: 2662)
Multiplex communications
Communication over free space
Combining or distributing information via code word channels...
C370S441000, C370S515000, C455S574000
Reexamination Certificate
active
06330234
ABSTRACT:
TECHNICAL FIELD
The present invention is directed to communication systems and, more particularly, to a method and apparatus for reducing current consumption in a communication system mobile unit.
BACKGROUND ART
Communication systems, such as cellular systems (both time division multiple access (TDMA) and code division multiple access (CDMA) cellular systems) and personal communication systems (PCS), typically include mobile units and infrastructure, such as base stations, with which the mobile units communicate. The infrastructure links the mobile units to a land line telephone system such as, for example, a point switched telephone network (PSTN) to enable mobile unit users to communicate with land line users. For example, when a mobile unit user places a call to a person at a land line telephone, the infrastructure connects the mobile unit to the land line.
Typically, mobile units are compact and battery powered so that they are easily transportable. For example, a user may carry a mobile unit in her purse, pocket, briefcase or car. While mobile units may have access to external power sources in some situations (e.g., in a car through the use of a lighter adapter), mobile units do not always have access to power other than their own self contained batteries. In a typical use, a user may charge the battery of her mobile unit over the weekend and, on Monday morning, may turn the mobile unit on and put it in her purse. Thereafter, the user may not recharge the battery until the mobile unit gives her a low battery indication. When the mobile unit is turned on and the user is not using the mobile unit for a call, the mobile unit is in standby. While in standby, a mobile unit cycles through a number of operating modes. For example, while in standby, a mobile unit may cycle through or between a sleep mode that draws very little current, various setup and power up modes that draw more current than the sleep mode and a full receive mode, wherein the mobile unit's receiver is fully powered up and is looking for communications, such as pages, from the infrastructure. In standby, the mobile unit occasionally looks for communication signals from the infrastructure, which would alert the mobile unit that the infrastructure is passing a call to the mobile unit. Standby is one of the most common operating modes for a mobile unit and commonly mobile unit manufacturers specify the standby battery life of their mobile units for a particular battery size.
Because standby is one of the most common modes of mobile unit operation, it will be readily appreciated that battery life in standby is a critical mobile unit feature. Battery life in standby mode is inversely proportional to the current that a mobile unit draws from its battery during standby operation. With the goal of extending standby times as far as possible, various semiconductor and mobile unit manufacturers have developed electrical components (e.g., chip sets or semiconductors) having various sections of circuitry that may be independently powered down. Such components allow, for example, transmitter circuitry, which is not needed in standby, to be powered down, thereby reducing the current consumption of the mobile unit by the amount of current saved by powering down the transmitter circuitry.
SUMMARY OF THE INVENTION
The invention disclosed herein reduces current consumption of a mobile communication unit, such as a cellular or mobile telephone that communicates with a base station, by disabling a temperature controlled crystal oscillator and code generators of the mobile unit while the mobile communication unit is in a sleep mode of operation, thereby reducing the sleep mode current consumed by the mobile communication unit. Prior to entering sleep mode, the mobile communications unit stores the state of the code generators and disables the temperature controlled crystal oscillator. Upon waking from sleep mode, the mobile communication unit calculates what the states of its code generators would have been if its temperature controlled crystal oscillator had not been disabled, and uses these calculated states to achieve synchronization with a code generator or code generators in the base station. Additionally, when a mobile unit designed in accordance with the teachings disclosed herein attempts to synchronize to a base station, the PN space that the mobile unit must search is reduced, thereby reducing the amount of current needed to awaken the mobile unit from sleep mode. Furthermore, a mobile unit designed in accordance with the teachings disclosed herein need not listen to an entire paging slot to determine whether the mobile unit is being paged by a base station.
In one embodiment, the present invention is a method of reducing current consumption in a mobile communication unit having an oscillator driving a first code generator, wherein the mobile communication unit is adapted to communicate with a base station having a second code generator. The method may include the steps of storing a first state of the first code generator that is substantially synchronized to the second code generator at a first time, entering a sleep mode for a predetermined period of time during which the oscillator and the first code generator are stopped, entering an awake mode wherein the oscillator and the first code generator are started and calculating a second state of the first code generator that is substantially synchronized to the second code generator at a second time, wherein the second state of the first code generator is calculated based on the first state of the first code generator.
The method may also include the step of updating the first code generator to the second state, thereby substantially synchronizing the first code generator with the second code generator at the second time.
In some embodiments, the step of calculating the second state of the first code generator includes multiplying the first state by a transformation matrix. Additionally, the method may also include the step of determining an estimated error between the second state of the first code generator and a state of the second code generator at the second time.
In some embodiments, the method may include the step of searching a range of PN states dependent on the estimated error between the second state of the first code generator and the state of the second code generator at the second time to synchronize the first code generator to the second code generator.
In some embodiments, the step of entering the sleep mode for the predetermined period of time may include entering the sleep mode for approximately 1.28 seconds or approximately 2.56 seconds.
The step of searching a range of PN states depending on the estimated error may include searching a range two times the estimated error. Further, the step of entering the awake mode may include entering the awake mode for approximately 20 milliseconds to determine if a page is received from the base station. Additionally, the method may include the step of returning to the sleep mode if no page is received from the base station at the mobile unit.
In a second embodiment, the present invention may be a current consumption reduction system for use in a mobile communication unit having a processor and an oscillator driving a first code generator, wherein the mobile communication unit is adapted to communicate with a base station having a second code generator. The current consumption reduction system may include a memory, instructions stored by the memory and adapted for execution by the processor, wherein the execution of the instructions causes the processor to perform various steps. The steps may include storing a first state of the first code generator that is substantially synchronized to the second code generator at a first time, entering a sleep mode for a predetermined period of time during which the oscillator and the first code generator are stopped, entering an awake mode wherein the oscillator and the first code generator are started and calculating a second state of the first code generator that is substa
Bradley Wayne H.
Nguyen Dien N.
Schellinger Michael J.
St. Angel Lindo
Tomasi Peter A.
Marshall Gerstein & Borun
Nguyen Hanh
Patel Ajit
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