GB2464942A

GB2464942A - A method for conserving battery power in a mobile communication device

Info

Publication number: GB2464942A
Application number: GB0819858A
Authority: GB
Inventors: Avishai Yacobi; Vitaliy Gurevich; Michael Levin
Original assignee: Motorola Inc
Current assignee: Motorola Solutions Inc
Priority date: 2008-10-29
Filing date: 2008-10-29
Publication date: 2010-05-05
Anticipated expiration: 2028-10-29
Also published as: GB2464942B; GB0819858D0

Abstract

A network manager operating in the wireless communications network transmits a periodic burst to the mobile communications device. The periodic burst includes a synchronization field having an unused data location. If the network manager determines that a message is to be sent to the mobile communications device, it is queued until a selected time and a message indicator is set in the unused data location. The mobile communications device switches to a high power listening mode from a low power dormant mode in time to receive the periodic burst. The mobile communication device verifies if the message indicator is set at the unused data location. The mobile communication device maintains the listening mode if the message indicator is set, otherwise reverts to the dormant mode until the reception time of the next periodic burst.

Description

METHOD FOR CONSERViNG BAUERY POWER

TECHNICAL FIELD

This disclosure relates generally to wireless communications devices and more particularly to a communication method for conserving battery life in a wireless communications device.

BACKGROUND

A substantial amount of research and development effort has gone into the design of modern-day communications devices. Bandwidth, power, and cost efficiency are some of the design considerations for a communication device, with the choice of which specific design parameter to be optimized depending on particular system requirements. For example, it is desirable for digital terrestrial microwave radios to have good bandwidth efficiency with low bit-error rate. It may be more desirable in hand-held cellular telephones, however, to save power, and enable extension of battery life.

Similar to cellular telephones, in digital mobile radio networks, such as the Professional Mobile Radio (PMR) networks used by public and government organizations like police, military, transportation, utilities, and firefighters, power efficiency is extremely desirable. Power efficiency describes the ability of a system to send information reliably at the lowest practical power level. Many present-day PMR networks operate on the Terrestrial Trunked Radio (TETRA) standard, promulgated by the European Telecommunications Standards Institute (ETSI). TETRA allows a device to combine the capabilities of a mobile radio, a digital cellular telephone, a mobile data terminal (MDT) and a pager into a single device. TETRA employs Time Division Multiple Access (TDMA), a technology that divides a single communications channel into a number of separate channels by dividing a fixed time period into time slots, allowing the transfer of multiple streams of voice and data over the same physical transmission medium.

Some TETRA devices are small battery-powered portable units, whose size restrictions limit the capacity of the associated battery. For such devices, battery life improvement has been sought continuously, through supply-oriented means such as employing more efficient battery materials, or alternate solutions aimed to conserve battery power in TETRA devices. Suggested solutions have included changing the hardware configuration to control the amount of power consumed by various components in a TETRA device. These solutions introduce additional elements and resources into the TETRA device, and hence, involve considerable effort and complexity. Thus, there exists a need for devising methods and systems directed towards conserving battery power more efficiently in communication devices such as TETRA devices.

BRIEF DESCRIPTION OF THE FIGURES

Embodiments of the claimed invention are described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to reference like features and components.

FIG. 1 illustrates an exemplary environment for implementing a communication method for conserving battery power in a communication device operating in a wireless communication network.

FIG. 2 illustrates a block diagram of exemplary components of a network manager, and other devices operating in a TETRA network for implementing the claimed communication method.

FIG. 3 illustrates a block diagram of exemplary components of a target mobile device operating in a TETRA network for implementing the claimed communication method.

FIG. 4 illustrates a structure of a multiframe and a frame including a periodic burst as used in some embodiments of the claimed communication method.

FIG. 5 illustrates an overview of an exemplary communication method for conserving battery power in a target mobile device operating in a wireless communications network.

FIG. 6 is a flow diagram of an alternative embodiment of a communication method for conserving battery power implemented at the network end in a TETRA network.

FIG. 7 is a flow diagram of a further embodiment of a communication method for conserving battery power implemented in a target mobile device operating in a TETRA network.

Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of various embodiments. In addition, the description and drawings do not necessarily require the order illustrated. Apparatus and method components have been represented, where appropriate, by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the various embodiments so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. Thus, it will be appreciated that for simplicity and clarity of illustration, common and well-understood elements that are useful or necessary in a commercially feasible embodiment may not be depicted in order to facilitate a less obstructed view of these various embodiments.

DETAILED DESCRIPTION

Generally, the disclosure set out below presents a communication method for efficient conservation of battery power in a communication device. The communication device is, in one embodiment, a short-range, portable electronic device used for mobile voice or data communication over a wireless communication network. In one embodiment, a manager of the wireless network

L

determines if a message is to be transmitted to the communication device, and if so, the network manager queues the message until a selected time. The network manager transmits a periodic burst to synchronize the communication device to one or more network parameters. The periodic burst includes a synchronization field having an unused data location. The network manager sets a message indicator at the unused location before transmitting the burst if a message addressed to the communication device is in queue.

In addition to the steps implemented by the network manager, the communication device operates in a higher power listening mode or a lower power dormant mode. In the dormant mode, fewer components of the communication device are active, reducing the power consumption of the communication device. In the listening mode, a larger number of the components are active, resulting in greater power consumption. The communication device switches from the dormant mode to the listening mode at a selected time, which in some embodiments corresponds to reception of the periodic burst by the communication device. Upon receiving the periodic burst, the communication device determines if the message indicator is set, and if so, remains in the listening mode for receiving messages transmitted by the network manager. If the message indicator is not set, the communication device reverts to the dormant mode until the expected time of reception of the next periodic burst. This enables the communication device to operate in the dormant mode for an extended period, saving a substantial amount of battery power. The method described above limits the number of conventional sleep and wakeup cycles, and their associated functions, in the communication device. The reduction in the RF activities of the communication device facilitates conservation of battery power without losing any information transmitted by the network manager.

Those skilled in the art will realize that the above-recognized advantages and other advantages described herein are merely illustrative and are not meant to be a complete rendering of all of the advantages of the various embodiments.

The disclosed communication method can be used in many different operating environments and systems. An exemplary environment that is suitable for practicing various implementations is discussed in the following section with respect to the accompanying figures. The terms communication device' and target mobile device' are used interchangeably in the description of the FIG. I through FIG. 7.

FIG. 1 illustrates an exemplary environment 100 for implementing the communication method for conserving battery power in a communication device.

The environment 100 includes a wireless communications network 102, a network manager 104, and one or more communication devices 106(A)-i 06(C) operating in the wireless communication network 102.

For discussion purposes, the description of the method for conserving battery power is with reference to a digital mobile radio network operating on the TETRA standard. Those skilled in the art, however, will recognize and appreciate that the specifics of this example are merely illustrative of some embodiments and that the teachings set forth herein are applicable in a variety of alternative settings.

For example, since the teachings described do not depend on the environment, they can be applied to any type of communication network. As such, other alternative implementations of using different types of communication networks using different standards are contemplated and are within the scope of the various teachings described.

The network manager 104 can be a single entity or a number of entities servicing one or more devices operating in the wireless communications network 102. In one embodiment, the network manager 104 serves as a base station that operates as the hub of a local wireless network, as well as a gateway between a wired network and the wireless communications network 102. The network manager 104 can further include components such as a low-power transmitter, storage area and a wireless router to implement the claimed communication method. In another embodiment, the network manager 104 includes all of the equipment and sub-systems that comprise a TETRA network.

The communication devices 106(A)-106(C) can include devices such as walkie-talkies, two-way radios, mobile phones, cellular phones, Personal Digital Assistants (PDAs), laptops, pagers, and so on. In one embodiment, the communication devices 106(A)-I 06(C) operate in a group calling mode in which a single button push connects the user to the network manager 104 and all the other users in a group. In other embodiments, the communication devices 106(A)- 106(C) operate as one-to-one walkie-talkies. For purposes of clarity, the environment 100 is shown with the three communication devices 106(A)-106(C), but additional or fewer devices may be deployed as understood by those of ordinary skill in the art.

In some embodiments, various components of the environment 100 communicate using time division multiple access (TDMA) channel access method. The network manager 104 transmits information to the communication devices 106(A)-i 06(C) in TDMA time slots, frames, and multiframes, each TDMA multiframe including 18 TDMA frames. Each communication device is associated with a particular physical channel in the network 102, and each physical channel is associated with a particular slot in each TDMA frame. The particular physical channel can be selected from a set of M physical channels. The number of physical channels available may depend upon a number of factors including, but not limited to: the specific network configuration, the protocols being used, and the access technology being deployed. The network manager 104 allocates a particular time slot on a particular physical channel to one of the communication devices or, to a number of communication devices operating in a group mode and identified by a group identifier. This allows a number of communication devices to share a common transmission medium (e.g., radio frequency channel) while using only the part of the bandwidth.

FIG. 2 illustrates a diagram of exemplary components of a network manager 202, and other devices operating in a TETRA network for implementing the claimed communication method.

In an embodiment, the network manager 202 is communicatively coupled with a target mobile device 204. The communication between the network manager 202 and the target mobile device 204 is managed by a switching and management infrastructure (SwMI) 206 of the TETRA network.

Only a single target mobile device 204 has been illustrated in FIG. 2 for purposes of clarity. Those of ordinary skill in the art, however, will understand that additional devices can be deployed in the TETRA network. In one embodiment, a number of target mobile devices operate in the TETRA network over the same physical channel in a group-calling mode. For example, the target mobile devices can be a group of passive TETRA pagers, identified by a unique Group Short Subscriber Identity (GSSI), having only downlink capability and operating on a Main Control Channel (MCCII). The MCCH is a principal common control single-slot channel transmitted by the SwMI 206 and is located on time slot I of a main carrier.

The SwMI 206 is used to classif' all of the equipment and sub-systems comprising a TETRA network. In one embodiment, the SwMI 206 includes one or more base stations 212(A) -212(C), an inter-system interface 214, and a gateway 216, in addition to the network manager 202. The base stations 2 12(A) -2 12(C) serve as hubs of the TETRA network, coupled to the gateway 216. The gateway 216 provides an interface between the TETRA network and a wired network such as a PSTN network 218, while the inter-system interface 214 aids interoperability between two or more TETRA networks. The inter-system interface 214 is a standardized interface for allowing interoperability between the infrastructures supplied by different TETRA manufacturers. To allow the different TETRA manufacturers to configure their networks for optimum performance and design flexibility, standardization of equipment such as base stations has not been implemented in the TETRA standard. Thus, one or more components may be added or removed from the components illustrated in the FIG. 2 in order to implement the claimed communication method. For example, the network manager 202 can be configured to perform one or more functions of the base stations 2 12(A) -2 12(C) in some embodiments.

Further, in order to service the target mobile device 204, the network manager 202 schedules a particular time slot on the physical channel on which the target mobile device 204 operates. The network manager 202 transmits information addressed to the target mobile device 204 in a particular TDMA multiframe and frame in the particular time slot. To this effect, the network manager 202 includes a transmitter 208 and a processor 210. The transmitter 208 transmits a periodic burst over the MCCH to the target mobile device 204, in a predefined multiframe and frame, once per N multiframes. The periodic burst, the multiframe, and the frame are described in greater detail in connection with the

description of FIG. 4.

The periodic burst transmitted by the transmitter 208 includes a synchronization field, generally aimed at enabling the target mobile device 204 to synchronize to one more network parameters such as frequency. The TETRA standard specifies the contents of the bits in this field, except for the last bit of the periodic burst, which is a reserved bit and represents an unused data location. This unused data location is used by the processor 210 to set a message indicator to indicate that a message addressed to the target mobile device 204 has been queued and will shortly be transmitted. The processor 210 determines whether a message requires transmission and if so, the processor 210 queues the message until a selected time. The processor 210 determines an expected time of the next time slot scheduled by the network manager 202 to service the target mobile device 204 when the queued message is to be sent. The processor 210 further determines the number of multiframes and frames transmitted to the target mobile device 204 since the transmission of the last periodic burst. Since the periodic burst is transmitted to the target mobile device 204 once per N multiframes, the processor 210 determines whether the periodic burst can be transmitted to the target mobile device 204 in the next time slot. If the periodic burst can be sent in the next time slot, the processor 210 sets a message indicator in the unused data location along with a flag at a predefined location. The message indicator can be a bit set at the unused data location in the frame carrying the periodic burst, whereas the flag can be a session-specific variable internal to the processor 210. Subsequently, the periodic burst is transmitted to the target mobile device 204. Additionally, the message is transmitted in the following time slots scheduled by the network manager 202 to service the target mobile device 204.

FIG. 3 illustrates a block diagram of exemplary components of a target mobile device 300 operating in a TETRA network for implementing the claimed communication method.

The target mobile device 300 includes a receiver 302 including an antenna 308, coupled to a device 304, and a battery 306.

In some embodiments, one or more functions of the device 304 can be implemented through hard-wired logic capable of performing equivalent operations. In some embodiments, the device 304 includes a processor 312 coupled, via an input/output (110) bus 310, to a slot scheduler 314, a timer 316, an oscillator 318 for providing a reference clock for the timer 316, and a memory 320.

As in conventional radio communication devices, the battery 306 supplies power to circuitry within the target mobile device 300. The battery 306 is depleted when current is consumed by the circuitry or the components within the target mobile device 300. In particular, the receiver 302 consumes a relatively large amount of current when receiving the RF signal.

In order to conserve battery power, the target mobile device 300 operates in a higher power listening mode or a lower power dormant mode. In some embodiments, the target mobile device 300 switches to the listening mode at a selected time which can correspond to the scheduled reception of a periodic burst.

The periodic burst is received by the target mobile device 300 once per N multiframes, in a predefined multiframe and frame. For rest of the time, if no signal is to be received by the target mobile device 300, the target mobile device 300 operates in the dormant mode.

In the dormant mode, fewer elements within the target mobile device 300 are active and thus supplied with power from the battery 306 (e.g., fewer transistors in the device 304 are active, resulting in lower power drain from the battery). For example, in some embodiments, the timer 316 and the oscillator 318 are active in the dormant mode, along with minimal other components. The timer 316 generates timing signals to determine a time for enabling the processor 312 to switch the target mobile device 300 to the listening mode. The time for switching the target mobile device 300 to the listening mode is based on the computations performed by the slot scheduler 314. In one embodiment, the slot scheduler 314 receives information from the network regarding the next time slot expected to be scheduled for servicing the target mobile device 300 (next time slot). Further, the slot scheduler 314 receives information from the processor 312 or the memory 320 regarding the number of multiframes and frames received since the last periodic burst. The slot scheduler 314 uses this information to direct the timer 316 to generate appropriate timing signals to switch the target mobile device 300 to the listening mode to receive the next periodic burst in the next time slot. In some embodiments, the slot scheduler 314 can be implemented as a software object activated by the timer 316 in a particular time-zone of each time slot. The slot scheduler 314 provides scheduling information for all software and hardware components of the target mobile device 300. This scheduling information is used to activate one or more components during the subsequently scheduled time slots.

In addition to switching the target mobile device 300 to the listening mode, the processor 312 processes the particular multiframe and frame carrying the periodic burst received from the network. The periodic burst includes synchronization information for aligning the target mobile device 300 to one or more network parameters. The synchronization information can be stored in the memory 320 along with other operational information. The processor 312 uses the synchronization information for effecting functions such as frequency correction, time adjustment, and measurement of the received signal strength. The periodic burst further includes an unused data location where a message indicator is set by a network manager operating in the TETRA network if any message addressed to the target mobile device 300 is awaiting transmission. On receiving the periodic burst, the processor 312 checks the unused data location. If a message indicator is present in the unused data location, the processor 312 maintains the target mobile device 300 in the listening mode. In one embodiment, this time period extends to the expected time of reception of the next periodic burst. Subsequently, the target mobile device 300 receives the message transmitted by the network manager in the next time slot.

The target mobile device 300 is switched from the dormant mode to the listening mode and vice versa under the control of the processor 312. The processor 312 issues relevant signals via the 110 bus 310 serving as a serial communication interface, to configure the target mobile device 300 to switch between the different modes. On receiving the relevant timing signals from the timer 316, the processor 312 facilitates a connection between the receiver 302 and the battery 306 via I/O bus 310, thereby providing power to the receiver 302 and switching the target mobile device to the listening mode. After receiving the periodic burst, if a message indicator is not present at the unused data location, the processor 312 issues relevant signals for disconnecting the receiver 302 from the battery 306. The target mobile device 300 then operates in the dormant mode using very little battery power.

FIG. 4 illustrates structures of a time slot, a frame, and a multiframe carrying a periodic burst, including synchronization information, transmitted in a TETRA network as in some embodiments.

In a TETRA network, a network manager (such as network manager 202, FiG. 2) transmits the periodic burst including synchronization information to a target mobile device operating over a particular physical channel. The periodic burst includes a synchronization field having information to enable the target mobile device to synchronize to one or more network parameters, such as frequency.

The periodic burst is transmitted in scheduled time slots to the target mobile device in a particular TETRA multiframe and frame. In a TETRA TDMA network, information is transmitted using TDMA multiframes, frames, and time slots. The basic unit of the TDMA frame is a time slot 402, which in the TETRA standard is 14.167 milliseconds long and includes 510 modulating bits. Four time slots form a TDMA frame 404 of duration 56.67 milliseconds, and 18 such TDMA frames form a multiframe 406 of duration 1.02 seconds. In some embodiments, a network manager operating in the TETRA network transmits a periodic burst including synchronization information once per four multiframes.

The synchronization information is sent in the periodic burst in frame 18 of multiframe 4 as shown in FIG. 4, frame 18 being used for control signaling. The last bit of the periodic burst is a reserved bit 408 and represents an unused data location, and at present, no restrictions exist in any regulating documents on how to fill the reserved bit. In one embodiment, the network manager sets the reserved bit 408 in frame 18 for providing an indication to the target mobile device that a message will be transmitted shortly. In other embodiments, a flag can be set in addition to setting a message indicator at predefined location in the frame 18 for indicating the presence of the message queued at the network end.

An exemplary communication method for conserving battery power in a target mobile device operating in a wireless communications network is described with reference to FIGS. 5 through 7. Processes 500, 600 and 700 are illustrated as a collection of blocks in a logical flow diagram, which represents a sequence of operations that can be implemented in hardware, software, or a combination thereof. In the context of software, the blocks represent computer instructions that, when executed by one or more processors, perform the recited operations. The order in which the process is described is not intended to be construed as a limitation, and any number of the described blocks can be combined in any order to implement the process, or an alternate process. Additionally, individual blocks may be deleted from the process without departing from the spirit and scope of the subject matter described herein. For discussion purposes, the processes 500, 600 and 700 are described with reference to the implementations of FIG. 2 through FIG. 4.

FIG. 5 illustrates an overview of an embodiment of a communication method for conserving battery power in a target mobile device 504 serviced by a wireless network manager 502. As noted in the figure, steps 506 -510 are performed by network manager 502, while steps 512 -516 are executed at target mobile device 504.

At step 506, the network manager 502 determines whether to transmit a message to the target mobile device 504 to accomplish a predefined function. The message can be, for example, an SDS acknowledgement message that is to be sent to the target mobile device 504. Upon determining that the message is to be sent to the target mobile device 504, the network manager 502 queues the message at the network end until at least a next time slot scheduled for servicing the target mobile device 504.

Step 508 determines whether an opportunity for transmitting a periodic burst in the next scheduled time slot exists, the opportunity occurring once every N multiframes transmitted to the target mobile device 504. When the opportunity occurs, prior to transmitting the periodic burst to the target mobile device 504, the network manager 502 verifies if any message addressed to the target mobile device 504 is in queue awaiting transmission. In case one or more of such messages are in queue, the network manager 502 sets a flag at a predefined location and a message indicator at an unused data location in the periodic burst before transmitting the periodic burst.

The network manager 502 transmits the periodic burst to the target mobile device 504 at a selected time in predefined time slots at step 510. In one embodiment, the network manager 502 transmits the periodic burst in the last frame of each multiframe-MFN (Frame 18 in a TETRA system) in the time slot-SN that is predefined by a relation, for instance, (MFN + SN) mod 4 = 3. Since each target mobile device processes a particular time slot in a frame, the target mobile device would receive the periodic burst every fourth multiframe.

Generally, for any similar protocol frame consisting of N slots, the following relation can be applied: (MFN + Slot N) mod N P Where: MFN is the multiframe number Slot N is the radio used slot number, and P is a constant value.

At step 512, the target mobile device 504, operating in the dormant mode, switches to the listening mode at a time corresponding to the reception of the periodic burst. In some embodiments, the target mobile device 504 includes relevant components and modules for determining the expected time of reception of the periodic burst in a subsequent time slot.

The target mobile device 504 receives the periodic burst at step 514 and checks a selected location in a particular multiframe and frame including the periodic burst. In one embodiment, the selected location is the unused data location in the periodic burst.

The target mobile device 504 continues in the listening mode if the message indicator is present in the unused data location at step 516. The target mobile device 504 can subsequently receive the messages transmitted by the network manager 502. If the message indicator is not set at the unused data location, the target mobile device 504 reverts to the dormant mode until an expected time of reception of the next periodic burst. The power savings achieved by implementing the claimed communication method at the network end are described in connection with the description of FIG. 7.

FIG. 6 illustrates an embodiment of a communication method for conserving battery power implemented at the network end in a wireless network.

For discussion purposes, the method is described with reference to the TETRA network as described in connection with FIG. 2. Those skilled in the art, however, will recognize and appreciate that the specifics of this example are merely illustrative of some embodiments and that the teachings set forth herein are applicable in a variety of alternative settings.

Preliminary to the operations set out in FIG. 6, a network manager operating in the TETRA network queues one or more messages to be transmitted to a target mobile device until a selected time. Each target mobile device is associated with a particular physical channel. The network manager divides the physical channel into a number of time slots. The network manager is configured to allocate a particular time slot to a particular target mobile device or a particular group of target mobile devices. At step 602, the network manager uses one or more conventional techniques to schedule the time slots for servicing the target mobile device operating over the particular physical channel. The message addressed to the target mobile device is queued until at least a subsequent time slot scheduled by the network manager to service the target mobile device. In one embodiment, the network manager can transmit a relevant control signal to the target mobile device to provide notification of the scheduled time slots.

At step 604, the network manager determines whether a periodic burst is scheduled to be sent to the target mobile device. The periodic burst is transmitted in a predefined time slots. In one embodiment, the network manager can apply a predefined relation such as the relation described with reference to step 510 for transmitting the periodic burst. Since the target mobile device processes a particular time slot in a frame, it can be determined when each target mobile device would receive the periodic burst. As per the relation, (MFN + SN) mod 4 3, the target mobile device operating on timeslot 1 would receive the periodic burst in multiframes 2, 6, 10 and so on, while a target mobile device operating on time slot 2 would receive the periodic burst in multiframes 1, 5, 9 and so on.

At step 606, if the network manager determines that a periodic burst is scheduled to be transmitted to the target mobile device, the network manager determines whether any messages addressed to the target mobile device are in queue awaiting transmission. In other words, the network manager determines whether the message queue associated with the particular target mobile device is empty or whether the queue contains one or more messages.

At step 608, if the message queue is not empty, the network manager sets a flag at a predefined location to true. In addition, the network manager sets a message indicator at an unused data location of the periodic burst to 1.

At step 610, if the message queue is empty, the network manager sets a flag at the predefined location to false. In addition, the network manager also sets the message indicator at the unused data location of the periodic burst to 0.

At step 612, the periodic burst is transmitted to the target mobile device in the next scheduled time slot. In some embodiments, the periodic burst is directed to all target mobile devices operating on the particular physical channel on which the periodic burst is transmitted. In other embodiments, the periodic burst is directed to only those target mobile devices operating on the particular physical channel on which the periodic burst is transmitted and that are members of a predefined group.

Returning to step 604, if the periodic burst is not scheduled, the network manager determines at step 614 whether there is an opportunity to transmit one or more messages addressed to the target mobile device. The messages can include short data service (SDS) messages, control messages, or status messages. The message transmission opportunity occurs only after a message indicator is received by the target mobile device in the last periodic burst. If there is no such opportunity, the method reverts to the step 602 for scheduling time slots for one or more of the target mobile devices operating over the physical channel.

If there is an opportunity to transmit one or more messages to the target mobile device, at step 616, the network manager verifies whether there is a message in the message queue and if the flag at the predefined location is set to true. In a first situation, where the network manager is to send a message to the target mobile device, the message is queued until the time of reception of the periodic burst by the target mobile device. However, if the target mobile device is not scheduled to receive the periodic burst in the next scheduled time slot, a message indicator is not set at the unused data location. In this situation the queue is not empty, and the flag is set to false. In a second situation, if the network manager succeeds in transmitting all messages in queue to the target mobile device before the scheduled time slot has expired, the flag remains in the true state even though the queue is empty. In both the first and second situations, the method loops back to scheduling slots at step 602.

At step 618, if there are one or more messages in the queue and if the flag is set to true, the network manager transmits one or more of the messages in the queue to the target mobile device, As illustrated in FIG. 6, the transmission of messages occurs only if the message indicator was present in the latest periodic burst transmitted by the network manager to the target mobile device. Finally, the method reverts to the step of scheduling slots at step 602.

FIG. 7 presents an embodiment of a communication method for conserving battery power implemented in a target mobile device operating in a TETRA network. For purposes of clarity, this method is described with reference toFIG. 3and FIG. 6.

A target mobile device operating in a wireless communications network consumes a substantial amount of battery power while listening for signals transmitted by the wireless communications network or other devices operating in the network. The target mobile device can alternate between the listening mode and the dormant mode, in which the target mobile device consumes substantially less power than in the listening mode. At step 702, the target mobile device switches to a listening mode at a selected time. In one embodiment, the active components of the target mobile device switch relevant components including a processor in the target mobile device to the listening mode in time to receive a periodic burst transmitted by the network At step 704, the target mobile device prepares for a downlink event.

Downlinking of information can occur only on a time slot allocated by the network manager to the target mobile device over a physical channel on which the target mobile device operates. The target mobile device performs relevant functions to prepare for reception of information. The information can be contained within a periodic burst, as an SDS message, or a status message.

Step 706, determines whether the periodic burst is received at the target mobile device. If the target mobile device has not received the periodic burst, the target mobile device performs normal downlink processing functions at step 708.

The processing functions can be associated with reception of other information such as SDS messages or status messages.

In the event that the periodic burst is received at step 706, the target mobile device verifies whether a message indicator is set at an unused data location in the periodic burst at step 710. In one embodiment, the target mobile device verifies whether the last bit at the unused data location is set, and if set, the method proceeds to the downlink processing event at the step 704. In case the message indicator is not set at the unused data, the target mobile device reverts to the dormant mode for N multiframes at step 712. Subsequently, after N multiframes, the target mobile device switches back to the listening mode and continues as described in the above section.

In the described embodiments, the target mobile device maintains the higher power listening mode only on receiving an indication of expected downlink activity from the network. Otherwise, the target mobile device operates in the dormant mode. For a portable device such as a TETRA radio or a TETRA pager, exemplified by the device marketed by Motorola, Inc. as model XiR P8260, implementation of the claimed communication method resulted in a 98% reduction in the RF activities. In the dormant mode, the TETRA pager drew only about 6mA to 7mA. As a result, the battery life of a TETRA pager using an embodiment of the claimed method and employing an 1850 milliampere-hour battery was 250 hours, compared to 40 hours for a conventional TETRA pager.

Implementation of the communication method substantially increased battery lifetime and facilitated substantial power savings in the TERA pager.

In the foregoing specification, specific embodiments have been described.

However, one of ordinary skill in the art will appreciate that various modifications and changes can be made without departing from the scope of the invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of present teachings.

The benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential features or elements of any or all the claims. The invention is defined solely by the appended claims including any amendments made during the pendency of this application and all equivalents of those claims as issued.

Moreover in this document, relational terms such as first and second, top and bottom, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms "comprises," "comprising," "has", "having," "includes", "including," "contains", "containing" or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises, has, includes, contains a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises.. . a", "has.. a", "includes. . . a", "contains. . . a" does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises, has, includes, contains the element. The terms "a" and "an" are defined as one or more unless explicitly stated otherwise herein. The terms "substantially," "essentially," "approximately," "about" or any other version thereof, are defined as being close to as understood by one of ordinary skill in the art, and in one non-limiting embodiment the term is defined to be within 10%, in another embodiment within 5%, in another embodiment within I % and in another embodiment within 0.5%. The term "coupled" as used herein is defined as connected, although not necessarily directly and not necessarily mechanically. A device or structure that is "configured" in a certain way is configured in at least that way, but may also be configured in ways that are not listed.

The Abstract of the Disclosure is provided to allow the reader to ascertain the nature of the technical disclosure quickly. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, it can be seen that various features are grouped together in various embodiments for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separately claimed subject matter.

Claims

CLAIMSWhat is claimed is: 1. A communication method comprising: at a network manager in a wireless communication network: transmitting a periodic burst from the network manager to a target mobile device serviced by the network manager, the periodic burst including a synchronization field having an unused data location; determining whether a message is to be transmitted to the target mobile device; setting a message indicator at the unused data location if the message is to be transmitted; at the target mobile device: receiving the periodic burst at a reception time; switching from a dormant mode to a listening mode at a time corresponding to the reception time; determining whether the message indicator is set while in the listening mode; and maintaining the listening mode if the target mobile device determines that the message indicator is set, otherwise reverting to the dormant mode until the reception time of the next periodic burst.
2. The method of claim 1, wherein the periodic burst is transmitted using time division multiple access (TDMA) with M physical channels per carrier, where N is number of slots per frame, each physical channel is associated with a particular slot number in each frame, and the target mobile device is associated with a particular physical channel and processes only one slot per frame.
3. The method of claim 1 or 2, wherein the periodic burst is directed to all mobile devices serviced by the network manager and operating on a physical channel on which the periodic burst is transmitted.
4. The method of claim 3, wherein each of the mobile devices receives the periodic burst, switches from the dormant mode to the listening mode, determines whether the message indicator is set, and maintains the listening mode if it is determined that the message indicator is set or otherwise reverts to the dormant mode until the reception time of the next periodic burst.
5. The method of any one of the preceding claims, further comprising queuing all messages addressed to the target mobile device at the network manager.
6. The method of any one of the preceding claims, wherein no restrictions exist in any regulating documents on how the unused data location of thesynchronization field is to be filled.
7. The method of any one of the preceding claims, wherein on each physical channel the periodic burst is sent in a predefined multiframe and frame once per N multiframes in a Time Division Multiple Access (TDMA) multiframe transmission.
8. The method of claim 7, wherein the periodic burst occurs in one of the slots in the last frame of the particular multiframe in which the periodic burst is transmitted.
9. A network manager in a terrestrial trunk radio (TETRA) network, the network manager comprising: a transmitter configured to transmit a periodic burst in a multiframe TDMA transmission to the target mobile device on a physical channel that the mobile device operates on and in a multiframe and frame that is predefined for this physical channel, the periodic burst including a synchronization field having an unused data location in which no restrictions exist in any regulating documents on how the unused data location is to be filled; and a processor configured to determine whether a message is to be transmitted to a target mobile device serviced by the network manager and to set a message indicator in the unused data location if the message is to be transmitted.
10. The network manager of claim 9, wherein the periodic burst is directed to all mobile devices serviced by the network manager and operating on the physical channel that the periodic burst is transmitted on.
11. The network manager of claim 9 or 10, further comprising queuing all messages addressed to the target mobile device at the network manager.
12. A mobile device in a terrestrial trunk radio (TETRA) network, the device comprising: a receiver configured to receive a periodic burst in a multiframe TDMA transmission on a physical channel that the mobile device operates on and in a multiframe and frame that is preclefined for this physical channel from a network manager at a reception time, the periodic burst including a synchronization field having an unused data location; and a processor configured to determine whether the message indicator is set in the unused data location; wherein the mobile device is configured to switch from a dormant mode to a listening mode at a time corresponding to the reception time of the periodic burst, and wherein the mobile device is configured to maintain the listening mode if the processor determines that the message indicator is set, otherwise the mobile device is configured to revert to the dormant mode until the reception time of the next periodic burst.
13. The mobile device of claim 12, wherein the periodic burst is also directed to mobile devices other than the mobile device but operating on the same physical channel.
14. The mobile device of claim 12 or 13, wherein no restrictions exist in any regulating documents on how the unused data location is to be filled.
15. A mobile device according to any one of the preceding claims and substantially as herein described with reference to the accompanying drawings.
16. A network manager incorporating a mobile device according to any one of the preceding claims.