GB2411547A

GB2411547A - Dynamically determining a power class of a mobile radio communications device

Info

Publication number: GB2411547A
Application number: GB0404416A
Authority: GB
Inventors: David Bennett; Kenton Payne
Original assignee: NEC Technologies UK Ltd
Current assignee: NEC Technologies UK Ltd
Priority date: 2004-02-27
Filing date: 2004-02-27
Publication date: 2005-08-31
Also published as: GB0404416D0

Abstract

The invention allows a mobile radio communication device to dynamically change its power class according to the battery voltage of the device. A mobile radio communication device is operated in accordance with its default power class, which is one of a plurality of power classes defining maximum output power levels for mobile radio communication devices. However, operation in accordance with the default power class can unnecessarily shorten the talk time and stand-by time of the device by prematurely indicating the need for battery recharging when the battery voltage drops below the threshold voltage for the power amplifier for the default power class, even though the voltage is still sufficient to maintain a connection. The invention provides a mobile radio communications device arranged to operate in accordance with one of a plurality of power classes and including means to determine which of said plurality of power classes should be employed based on the battery voltage of the device. The battery voltage may be monitored continuously or periodically and the means to determine the power class may be a look-up table associating battery voltages with power classes (fig. 2). On detecting an increase or decrease in the battery voltage, the device determines the power class corresponding to the new voltage and can update its defined power class accordingly and notify the new power class to the network in a classmark change on the SACCH. In addition, when the device tries to camp on a base station subsystem and receives a MS_TXPWR_MAX_CCH from a base station indicating the maximum transmit power for the mobile's RACH burst, it can determine its transmit power by comparing the value sent by the base station with its new power class (fig. 1).

Description

241 1 547

MOBILE RADIO COMMUNICATIONS DEVICE AND RELATED

METHOD OF OPERATION

The present invention relates to a mobile radio communications device and related method of operation and, in particular, to such a device and method serving to extend the talk times and stand-by times as perceived by a user.

Considering as examples single mode devices such as a Global System for Mobile Communications (GSM), Enhanced Data rates for Global Evolution (EDGE) and Wideband COMA (WCDMA) devices, an important parameter, particularly from a marketing point of view, are the talk and/or stand-by times exhibited by such devices. These parameters comprise the length of time the device can remain in a talk or stand-by mode starting from a position of full battery charge. The greater these values, and thus the longer period of use that is available before the battery needs recharging, the more attractive the device will be as compared with competing devices offering shorter talk and stand-by times.

As noted, a principal parameter dictating the talk time of the device is the battery voltage. When fully charged, the battery of a mobile device such as a cellular phone will commonly supply a voltage of 4.2 V. During use of the device, the battery voltage will slowly decrease until the voltage, and thus the remaining charge, is no longer sufficient to drive the electronic circuitry of the device. For a typical GSM, EDGE or WCDMA device, such a situation usually occurs when the battery voltage/charge is no longer sufficient to allow the power amplifier within the device to effectively comply with its specification.

Such a condition can arise for a typical GSM power amplifier when the battery voltage reaches a level in the region of 3.4V. A particular application within the device monitors the battery voltage and is arranged to provide an audio and/or visual indication to the user that the battery of the device requires re charging when the output voltage of the battery falls to the 3.4V level. At this point it is determined that the power amplifier will no longer offer suitable functionality with this decreased battery voltage such that the device should not again be used to transmit until the battery voltage level has been restored, through recharging, to a level where the power amplifier can again function

correctly within its specification.

As will therefore be appreciated, the particular specification of the power amplifier within the device serves to effectively determine the talk and stand-by times of a particular device through determining the level to which the battery voltage can be allowed to fall before requiring recharging. Thus, once the battery voltage drops below the predetermined level required for the power amplifier to produce maximum power for a particular power class of device, the device serves to indicate that the battery requires recharging before it can again be operated.

It has however been identified that this maximum power value may in fact be higher than the actual power required to maintain a connection to the serving, or indeed a neighbouring, cell. If this is the case, it is noted that the user is then instructed, via the device, to recharge the phone prematurely The perceived talk and stand-by times may then be unnecessarily shortened and thus the effective operating characteristics of the device not fully realised.

The present invention seeks to provide for a mobile radio communications device, and a related method of operation, exhibiting advantages over known such devices and methods.

According to a first aspect of the present invention there is provided a mobile radio communications device arranged to operate in accordance with one of a plurality of power classes and including means arranged to determine which of said plurality of power classes is employed as based on the battery voltage of the device.

The invention is particularly advantageous in that, by allowing the power class to be determined on the basis of the remaining battery voltage, it is found that, for example, the power amplifier of the device can continue to be used even when the battery voltage has fallen below the threshold value identified for correct transmission at the device's default power class.

Thus, through selection of one of a plurality of power classes, the need to recharge that might otherwise be indicated at the device is overcome and the talk and stand-by times can therefore advantageously be extended.

Of course, it should be appreciated that, during an increase in the battery voltage perhaps, for example, by way of recharging the battery, the power class can be arranged to change to a different, but higher, power class.

In one arrangement, the means for determining which one of said plurality of power classes is employed includes means for monitoring continuously, or periodically, the battery voltage.

An important aspect of the present invention, is that in determining which of the plurality of power classes is to be employed, the power class of the device is effectively redesigned.

Further, the device advantageously employs a look-up table by means of which the battery voltage level is related to one of the plurality of power classes.

In particular, the look-up table comprises discrete levels representing different power classes and each such level is associated with a range of battery voltage values.

Preferably, the means arranged to determine which of a plurality of power classes is employed comprises means arranged to switch from one power class to another, but lower, one of the plurality of power classes responsive to a decrease in the battery voltage.

Thus, as will be appreciated, the switching to the lower power class effectively serves to redefine the power class within the device.

The redefined power class of the device is advantageously signalled to the network so as to allow the network to update its copy of the devices power class.

In a particular embodiment, the power class of the device is defined by a power amplifier within the device.

Of course, it will be appreciated that the device can comprise any appropriate mobile radio communications device but, in particular, the device comprises a cellular phone and, in particular, a GSM, EDGE or WCDMA cellular phone arranged for operation in accordance with 3GPP standards.

According to another aspect of the present invention, there is provided a method of controlling operation of a mobile radio communications device in accordance with one of a plurality of power classes and including the steps of determining which of said plurality of power classes is employed on the basis of the battery voltage of the device.

The method is further arranged so as to provide for additional advantages discussed above in relation to a mobile radio communications device embodying the present invention.

In particular, the method can include the step of determining which of a plurality of power classes includes the step of switching from one power class to another, but lower, one of the plurality of power classes in response to a decrease in the battery voltage.

As will be appreciated from the above, the method advantageously also includes the step of, once having redefined the power class of the device, signalling the network so as to allow the network to update its copy of the devices power class.

Thus, as will be appreciated, the invention can provide for a mobile radio communications device which can dynamically change its power class according to the battery voltage and so as to allow continued use of the power amplifier even when the battery voltage has fallen below the threshold required for correct transmission at the device default power class.

Advantageously, this provides the device with the ability to effectively choose whether or not it can continue to operate and will thereby extend the talk and stand-by times of the device by allowing for its use after the battery voltage has dropped below the level at which the device would normally signal to the user that the battery requires recharging.

The invention is described further hereinafter, by way of example only, with reference to the accompanying drawings in which: Fig. 1 is a schematic flow diagram illustrating the dynamic determination of a device's power class operating within the GSM 850/900 system; Fig. 2 is a schematic flow diagram illustrating the determination of the particular power class for the same system as in Fig. 1; Fig. As a schematic flow diagram illustrating the updating of a device's power class as with the system of Fig. 1; and Fig. 4 is a schematic flow diagram of the operation of the device in accordance with the system of Fig. 1 during the dedicated mode.

While this particular embodiment of the present invention is illustrated in relation to a GSM 850/900 system, it should be noted that the particular illustration could equally be applied to any of the GSM/EDGE bands described in 3GPP TS 45.005, or other mobile radio systems such as the GSM 1800/1900, the EDGE 850/900 1800/1900, and the WCDMA 800/1900/2100 bands.

Before referring to the accompanying figures, reference is now made to particular aspects of the standard 3GPP TS 45.008 which suggests that radio frequency power control can be employed to minimize the transmission power required by a mobile station, or by a basestation subsystem, whilst nevertheless maintaining the required quality of the radio links. Such minimization of the transmitted power levels advantageously serves to reduce interference to co-channel users. To meet this requirement, a mobile station will then attempt to camp onto the basestation subsystem that exhibits the lowest power requirement. Such initial cell selection, and cell-reselection during an idle-mode, is dictated by the C1 and C2 algorithms as described in the TS 45.008 standard. One of the parameters used in these algorithms is a Broadcast Channel Control (BCCH) parameter identified as MS_TXPWR_MAX_CCH which is employed to inform a mobile station accessing the cell for the first time what power level to use for its Random Access Channel (RACH) burst.

It is assumed that an operator will set this parameter based upon the identified power that a mobile located at the edge of the cell will require in order to transmit such that the RACH is successfully received at the basestation subsystem. As such, it is appreciated that this parameter will depend on the nature of the cell, i.e. whether it comprises a macro, micro or pico cell, and also the coverage afforded by the overall cell planning.

However, within the standard 45.008, it is noted that if a mobile is not able to meet the MS_TXPWR_MAX_CCH value defined by the cell, it should nevertheless transmit its RACH at the power level it is capable of producing that is closest to the MS_DXPWR_MAX_CCH value. That is, if the particular power class of the mobile station is lower than the MS_DXPWR_MAX_CCH value set by the basestation subsystem, the mobile station should nevertheless send the RACH at its default power class.

This arrangement advantageously allows for, for example, a mobile having power class 4 (i.e. transmitting at +33dBm) whose battery voltage is no longer sufficient to support this power class, to dynamically lower its power class to a level that can be supported by the battery voltage, for example to a power Class 5 (transmitting at +29dBm).

Turning now to Fig. 1, there is shown a schematic flow diagram of a GSM 850/900 system arranged to dynamically determine its power class according to the current battery voltage and as embodying the present invention.

It should be appreciated that the mobile device can be arranged to either continuously, or periodically, measure the battery voltage and then adjust the power class accordingly.

Thus, referring to Fig. 1, there is illustrated the continual and periodic, monitoring at block 10 of the current handset battery voltage 12 and the subsequent establishment at block 14 of the appropriate power class by means of, for example, a look-up table has to be described later, at step 14.

Once the power class has been determined, it is delivered to comparison block 16 at which the power class is compared with MS_DXPWR_MAX_CCH value allotted by the basestation subsystem of the particular cell with which the device handset is to communicate. If, at 16, it is determined that the indicated power class is greater than the selected power class, then, at block 18, it is determined that the RACH be sent at the power class of the handset as a default value. However, if the power class as indicated by the cell, is less than or equal to that determined by the handset, then the process continues via block 20 at which the RACH is to be sent at the MS_TXPWR_MAX_CCH power level.

The processing then continues via step 22 at which it is determined whether the Paging Access Grant Channel (PAGCH) is available. If not, the process returns to block 24 at which the power value MS_TXPWR_MAX_CCH of the selected cell is identified for repeated comparison with the power class selected within the device handset on the basis of the battery voltage within block 10.

However, if the PAGCH is determined to be available at block 22, then an initial message is sent by the handset at block 26, which includes an updated class mark identifying the modified power class of the device handset.

It is important to note that it is necessary to actually redefine the power class within the device, rather than just attempting to transmit at the lower power level.

Information relating to the defined power class is required to be used by the network to manage the device handset power control and hand-over.

Thus, any inaccurate information provided concerning the power that the device handset can generate is likely to lead to hand-over failure and the subsequent dropping of the device handset from the network. Full redefinition of the power-class, and confirmation of the redefined valued network, prevents such problems arising.

Turning now to Fig. 2 there is illustrated an example of the manner in which the power class or power level can be derived from the battery voltage reading. Again the example is provided in relation to a GSM850/900 system.

The handset battery voltage reading at block 12 is then mapped to a device power class at block 28 by means of a look-up table 30 which relates particular discrete battery voltage levels to associated power class and power level values.

Through the adoption of a variety of discrete voltage battery levels, it will be appreciated that each power class is associated with a range of battery voltage readings so as to prevent reclassification of the power class for each slight change in the battery voltage.

Once the appropriate power class has been determined by means of the lookup table at block 30, the newly determined power class is delivered to the device handset's class mark at step 32.

It is noted that the aforementioned look-up table method is a particular appropriate manner of relating the analogue variable battery voltage to the discrete levels that make up the GSM power levels, which generally vary in 2dB increments/decrements. Of course, it should be noted that the exact mapping of the battery voltage level to the power level depends upon a particular power amplifier selected for the device. As such, the look-up table then results from testing the maximum power that the power amplifier can generate, while still meeting the GSM specification, and at different battery voltage levels. It should have been noted that the look- up table may also depend upon operating frequency and temperature and the resulting of look- up tables can form part of the device handset's calibration data.

The illustration of the invention provided by Figs. 1 and 2 above relates particular to the initial connection to a network.

Referring now to Figs. 3 and 4, there is illustrated a particular manner in which power class selection can be made once connected to the network but as a result of a decreasing battery voltage level, for example during idle and/or dedicated modes.

The GSM specification is particular advantageous in that it can allow for a mobile station to update its class mark as often as is required. In order to achieve such an update, the mobile station is arranged to send a message identified as RIL3-RR CLASSMARKCHANGE on the Slow Associated Control Channel (SACCH) and the network then updates its copy of the mobile station class mark.

In order to avoid continuous class mark change messages due to a continuous decrease in battery voltage, the new battery reading is arranged to be compared with the look-up table to determine if it is in fact necessary to change the power class mark since it is only worth updating the network if the change in battery voltage is sufficient to require a power class change and, as noted above in relation to Fig. 2, not all minor changes in battery voltage level will require a change in power class.

Reference is now made to Fig. 3, which illustrates such processing. An old, or previous, battery reading 36 is compared with a new battery reading 38 at comparison block 40 and if it is determined that they are the same, the process merely returns to repeat the comparison for a yet further new battery reading. This initial loop remains until it is determined at block 40 that the new battery reading is different from the old battery reading at which time the old battery reading is updated at block 42 and it is then required to be determined at block 44 as to whether a new class mark is necessary on the basis of the updated battery reading. Such determination is made on the basis of the look- up table illustrated in Fig. 2. If it is determined that no new class mark is necessary, then the process returns to step 40 at which the new battery is again compared with the old battery reading.

If, however, the look-up table indicates that, in view of the magnitude and change of battery voltage, the class mark should be updated, the new class mark is identified at block 46 and the new power class of the mobile station identified is updated and delivered to the network by means of the 1 0 SACCH.

The processing illustrated in accordance with Fig. 3 should also be viewed in conjunction with Fig. 4, which shows how the mobile station handset Is arranged to behave during operation within a dedicated mode.

Again, the handset battery voltage level 12 leads to a set power class 14 which, at block 50 is compared with the MS_TXPWR_MAX_CCH power level selected by the cell.

If the respective power class values are the same or the selected power class in the handset is greater, then the TCH/Dedicated Control Channel (DCCH) power level is set at the MS TXPWR_MAX_CCH value and the process returns to step 56 at which the selected cell power level is determined by the comparison with the power class selected within the mobile station device.

If, however, at step 50, the power class selected within the device handset is less than that of the cell selected power level MS_TXPWR_MAX_CCH, then it is determined that the connection to the network should be dropped and the user notified the battery now requires recharging.

Of course, it should be appreciated that, for an idle mode, the mobile station device must first employ a RACH in order to establish a DCCH/SACCH to notify the network of the class mark change. The procedure for this is generally the same as identified in Fig. 1.

It should be appreciated that although the GSM channel names are used to illustrate the proposal, it could also be applied to WCDMA if the standards are change to include some lower UE power classes (i.e. less than +21dBm). Furthermore, if the GSM standards could also be changed to include lower power classes. The invention could be further exploited to improve talk & standby times. In both cases, the limiting factor is the number of bits used to convey the power class information. The more power classes that are required, the more bits will be needed to describe all the power classes. Hence, an increase in the number of bits used in the MS class-mark should also be pursued in the standards to exploit this proposal.

Claims

Claims 1. A mobile radio communications device arranged to operate in

accordance with one of a plurality of power classes and including means arranged to determine which of said plurality of power classes is employed and based on the battery voltage of the device.
2. A device as claimed in Claim 1, wherein the means arranged to determine which of the plurality of power classes is employed is arranged to monitor the battery voltage on a continuous basis.
3. A device as claimed in Claim 1, wherein the means arranged to determine which of the plurality of power classes is employed is arranged to monitor the battery on a periodic basis.
4. A device as claimed in Claim 1, 2 or 3, wherein the means arranged to determine which one of the said plurality of power classes is employed includes look-up table means arranged for associating the battery voltage value with a power class.
5. A device as claimed in Claim 4, wherein the look-up table means comprises discrete levels representing different power classes.
6. A device as claimed in Claim 4 or 5, wherein each discrete level represents a different range of battery voltage values.
7. A device as claimed in any one or more of Claims 1-6, wherein the means arranged to determine which of the plurality of power classes is employed comprises means to switch from one power class to another, but lower, one of the plurality of power classes responsive to a decrease in the battery voltage.
8. A device as claimed in any one or more of Claims 1-7, wherein the means arranged to determine which of the plurality of power classes is employed comprises means to switch from one power class to another, but higher, one of the plurality of power classes responsive to an increase in the battery voltage.
9. A device as claimed in any one or more of the preceding claims, and including means to define, or redefine the power class of the device.
10. A device as claimed in Claim 9, and including the means arranged to signal the defined, or redefined, power class to the network so as to allow for update of the network copy of the device power class.
11. A device as claimed in any one or more of the preceding claims, wherein the power class is defined by a power amplifier within the device.
12. A device as claimed in any one or more of the preceding claims, and comprising a cellular phone.
13. A method of controlling operation of a mobile radio communications device in accordance with one of a plurality of power classes and including the steps of determining which of said plurality of power classes is employed and on the basis of the battery voltage of the device.
14. A method as claimed in Claim 13, wherein the determination of which of the plurality of power classes is employed includes monitoring the battery voltage on a continuous basis.
15. A method as claimed in Claim 13, wherein the determination of which of the plurality of power classes is employed includes monitoring the battery voltage on a periodic basis.
16. A method as claimed in Claim 13, 14 or 15, and including determining which one of the said plurality of power classes employed by reference to a look-up table means arranged for associating the battery voltage value with a power class.
17. A method as claimed in Claim 16, wherein the look-up table means comprises discrete levels representing different power classes.
18. A method as claimed in Claim 16 or 17, wherein each discrete level represents a different range of battery voltage values.
19. A method as claimed in any one or more of Claims 13-18, wherein the determination of which the plurality of power classes is employed comprises the step of switching from one power class to another, but higher, one of the plurality of power classes responsive to an increase in the battery voltage.
20. A method as claimed in any one or more of Claims 13-19, wherein the determination of which of the plurality of power classes is employed comprises the step of switching from one power class to another, but lower, one of the plurality of power classes responsive to a decrease in the battery voltage.
21. A method as claimed in any one or more of the preceding claims and including the step of defining, or redefining, the power class of the device.
22. A method as claimed in Claim 21, and including the step of signalling the defined, or redefined, power class to the network so as to allow for updating of the network copy of the device power class.
23. A method as claimed in any one or more of the preceding claims, wherein the power class is defined by a power amplifier within the device.
24. A method as claimed in any one or more of the preceding claims, and comprising a cellular phone.
25. A mobile radio communications device arranged for operation in accordance with one of the plurality of power classes and substantially as hereinbefore described with reference to the accompanying drawings.
26. A method of controlling operation of a mobile radio communications device substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.