GB2435154A

GB2435154A - Power-saving mode in a communication network

Info

Publication number: GB2435154A
Application number: GB0602569A
Authority: GB
Inventors: Michael Roberts
Original assignee: NEC Technologies UK Ltd
Current assignee: NEC Technologies UK Ltd
Priority date: 2006-02-08
Filing date: 2006-02-08
Publication date: 2007-08-15
Anticipated expiration: 2026-02-08
Also published as: GB2435154B; GB0602569D0

Abstract

The present invention provides for a mobile radio communications device for communication by way of a mobile radio communications network and having a power-saving mode employing discontinuous reception, the discontinuous reception being available in at least two discrete modes, and the device being arranged to receive a control signal from the network which signal includes timing data for controlling switching of the discontinuous reception between the two set modes.

Description

MOBILE RADIO COMMUNICATIONS DEVICE

AND RELATED METHOD OF OPERATION

The present invention relates to a mobile radio communications device, and method of controlling the operation thereof and, in particular, to such a device and method arranged to provide for discontinuous reception so as to allow for power saving within the device.

While the provision of networks supporting packet switched services is becoming evermore prevalent, limitations exhibited by such services nevertheless remain. One particular problem is that it is not possible to tell within any certainty at which point in time packets are likely to arrive at the mobile radio communications device handset from the Serving GPRS Support Node (SGSN).

The protocols can be structured such that after expiry of a time specific period that is determined by a timer, the network generally maintains radio resources, such as the provision of a dedicated channel (in CELL DCH state), even though there may be no downlink traffic for the mobile radio communications device. This represents a Alternatively, the network can release the Dedicated Channel (DCH) resources immediately and place the mobile radio communications device into a Forward Access Channel (in CELL FACH) or power saving states such as CELL PCH and IJRA PCH.

When operating in the CELL FACH state, and only when the network can be certain that there are no further packets to send, can the mobile radio communications device be switched into a power saving state such as, for example, CELL PCH or LTRA PCH.

Whilst in the aforementioned power saving modes the discontinuous reception (DRX) cycle-length is fixed by the network. Any change then required for the cycle-length requires a specific signalling context from the network in order to initiate a change in the discontinuous reception cycle-length.

It can prove desirable to configure the mobile radio communications device to start with relatively short DRX cycle lengths and then pursue progressively longer DRX cycle lengths. Such a progressive increase in the DRX cycle length serves to limit the problem associated with the uncertainty in the arrival of the next packet from an application at the mobile radio communications device since it is considered advantageous to start with shorter DR.X periods assuming that no packets are received in the meantime.

However, the signalling overhead required to change the DRX cycle lengths, for example, in an ever-increasing manner noted above, places a relatively high demand on Radio Network Controller (RNC) processing load since the signalling overhead required to switch the mobile radio communications device into and out of, each DRX operating mode, is significant particularly when one considers the expected proliferation of IP Multimedia Subsystem (IMS) services.

Such high demands on the RNC processing load prove particularly disadvantageous.

Such relatively high resource control signalling in any case generally represents a heavy load for the network and also leads to a disadvantageous loss of power within the mobile radio communications device. This is due in particular to the need to perform explicit signalling procedures with the network.

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

According to a first aspect of the present invention there is provided a mobile radio communications device for communication by way of a mobile radio communications network and having a power-saving mode employing discontinuous reception, the discontinuous reception being available in at least two discrete modes, and the device being arranged to receive a control signal from the network which signal includes timing data for controlling switching of the discontinuous reception between the two modes.

Thus the present invention allows for the network to control the discontinuous reception pattern applied by the mobile radio communications device in a power-saving state.

The invention can therefore advantageously provide for the downloading from the network of predefined periods and related discontinuous reception timers to the mobile radio communications device where such control information can advantageously be arranged to apply a progressive increase in the discontinuous reception period so as to meet operational requirements. However, the disadvantageously high signallingload between the network and the mobile radio communications device as is experienced in the current art does not arise.

Preferably, each of the two said modes is advantageously arranged to offer a different period of DRX.

Further, the timing data can include identification of time periods for which each of the at least two modes is to operate.

In particular, the timing data can serve to provide for a sequence of time periods of increasing periods of DRX.

Advantageously, at least one of the time periods comprises a finite time period.

Then, during such a finite time period the mobile radio communications device is advantageously arranged to maintain cell reselection performance requirements.

Also, during such finite periods, the mobile radio communications device can be arranged to perform only intra frequency measurements, or only inter frequency measurements or, alternatively, a combination of such intra and inter frequency measurements, and inter-RAT measurements.

Preferably, the network comprises a IJTRAN and the power saving mode can comprise a CELL PCH or URA PCH mode.

The initial operation of the discontinuous reception can be initiated by a transition from a CELL DCH to either of the aforementioned CELL PCH or [IRA PCH.

Advantageously, the mobile radio communications device is arranged to read system requirements prior to the arrival of a paging signal.

According to another aspect of the present invention, there is provided a mobile radio communications network device arranged to deliver a control signal to a mobile radio communications device connected to the network and having a power-saving mode employing discontinuous reception, and said control signal including timing data for controlling switching of the discontinuous reception between two discrete modes of operation.

In particular, the network device is arranged to deliver timing data serving to identify time periods for which the respective discontinuous reception modes are required to operate.

Preferably, the timing data can serve to define a sequence of periods of increasing DRX.

In particular, at least one of the time periods can comprise a finite time period.

The network device is also advantageously arranged to identify cell re-selection requirements for each period.

Further, the network device can be arranged to initiate only intra frequency measurements, or inter frequency measurements, or combination of the same, within the mobile radio communications device.

Of course, as above, the network device can comprise part of a UTRAN.

Also, the power saving mode can comprise either a CELL PCH or IJRA PCI-I.

According to a further aspect of the present invention there is provided a method of controlling discontinuous reception in a power saving mode of a mobile radio communications device connected to a mobile radio communications network, including the steps of delivering from the network a control signal including timing data for controlling switching of the discontinuous reception between two discrete modes of operation.

Preferably the two modes of operation offer different periods of disconnectivity.

Further, the control signal delivered from the network can include timing data which serves to identify time periods for which the respective modes of operation are employed.

in particular, the method can include the step of providing a sequence of time periods of increasing disconnectivity.

Preferably the method includes delivering a control signal from the network having timing data representing at least one finite time period.

Preferably for the finite time period cell re-selection performances are maintained.

Also, during any such finite period, the network can be arranged to require the mobile radio communications device to perform only intra frequency measurements, only inter frequency measurements or alternatively both intra and inter frequency measurements.

In particular, the method is arranged for controlling discontinuous reception in a power saving mode for a mobile radio communications device connected to a UTRAN.

As above, the power saving mode can comprise either CELL PCH or URA PCH.

Further, the transition from a CELL PCH state to either one of the CELL PCH or URA PCH states can serve to initiate the discontinuous reception.

Thus, as will be appreciated, the present invention can provide for the programming of discontinuous reception modes for a mobile radio communications device when in a RRC connected state such as CELL PCH or URA PCH.

The invention is described further hereinafter, by way of example only, with reference to the accompanying drawings in which: Fig. 1 is a schematic representation of a mobile radio communications device receiving a control signal including timing data according to an embodiment of the present invention; Figs. 2A-2C illustrate schematically the device of Fig. I but when operating in discontinuous reception mode and in accordance with three respective disconnection cycles; and Fig. 3 is a timing diagram related to the disconnection cycles arising in devices illustrated in Figs. 2A-2C.

Turning first to Fig. 1, there is illustrated in schematic form a mobile radio communications device 10 including transceiver circuitry 12, processing circuitry 14, and associated memory 16 and, functionality 18 serving to provide for power saving mode employing discontinuous reception DRX.

As illustrated, the device 10 is arranged to receive a control signal A issued by the UTRAN and which includes timing data ijk which serves to indicate the respective time periods for which different modes where DRX modes should operate. It should be appreciated that in the illustrated example, each of the DRX modes offers a different period of disconnectivity as discussed later in relation to Figs. 2A and Fig. 3.

With regard to Figs. 2A-2C, there is illustrated in schematic form the manner of operation of the mobile radio communications device 10 of Fig. I in accordance with the three timing periods i, j, k contained within the control signal A delivered from the LJTRAN to the mobile radio communications device 10 in Fig. 1. That is, Fig. 2A relates to discontinuous reception for a period i and in accordance with the first mode; Fig. 2B illustrates the operation for a second time periodj in accordance with the second mode; and Fig. 2C illustrates operation in accordance with a third time period k in accordance with a third mode.

As discussed further, the time periods i,, j, k can comprise a sequence of time periods of ever increasing periods of disconnectivity so as to advantageously meet operational requirements wherein initially short periods of disconnectivity are employed for a time during which reception of further packets might be considered most likely.

In the illustrated example, the UTRAN serve to control the DRX pattern applied by way of the mobile radio communications device 10 in the power saving CELL PCH and URA PCH states.

In particular, the UTRAN can download a pattern of DRX which includes the time period(s) for which each mode of DRX should apply. In this manner, on an initial transitioning of states from CELL DCH to CELL PCH, the DRX might be applied for an initial period of seven seconds at a particular disconnection cycle which is different from, and generally less than, the disconnection cycle employed during the periods subsequent to that seven second period.

Of course, it should be appreciated that the UTRAN can be arranged to program as many separate periods as might be required so that a progressive power saving strategy can then be readily applied.

Turning now to Fig. 3, the operation of the mobile radio communications device of Fig. 1, and as illustrated in relation to Figs. 2A-2C is further illustrated.

The timing diagram illustrates the three modes of DRX that are controlled by way of the control signal A illustrated in relation to Fig. 1.

As will be appreciated, Fig. 3 illustrates how the UTRAJ'J can apply URA PCH states for a DRX period i followed by periodj which is, in turn, followed by a period k.

Each of the periods i, j, k, represent a sequence of ever increasing periods of di sconnectivity.

For example, period i can last for seven seconds and employ disconnectivity cycles each lasting 2Oms; after that, periodj is applied for a period often seconds and offers a disconnection cycle lasting SOOms.

While, both of the periods i andj are finite, i.e. seven seconds and ten seconds in length respectively, period k is open-ended and infinite and so remains in place until a packet is next received and offers disconnection cycles lasting two seconds.

In this manner, the delay required in order to contact the mobile radio communications device is progressively diminished without any signalling exchange being required between the mobile radio communications device and the UTRAN, This, of course, in turn reduces processing requirement within the UTRAN and power requirements within the mobile radio communications device 10.

It can be seen that employment of the invention can therefore advantageously remove the requirement for a CELL FACH state.

During the application of the initial series of close-ended DRX schemes, that is those periods having a predetermined duration such as periods i and j in Fig. 3, a mobile radio communications device can maintain cell re-selection performance, and measurement performance, which is equal to that specified for the CELL FACH state. This advantageously ensures that, if a subsequent packet arrives, the mobile will always be in the correct cell in order to allow the radio resources to be allocated correctly in the cell.

It should readily prove possible for the network to control performance required for cell re-selection during such close-ended DRX periods. During such periods, the network can ask the mobile to perform either only intra frequency measurements, only inter frequency measurements, or a combination of both intra and inter frequency measurements and inter-RAT measurements.

IS In order that the mobile radio communications device can achieve access by way of the Physical Random Access Channel (PRACH) as soon as it receives a paging signal in the paging channel, it is arranged to read the system information concerning the occurrence of the information just prior to arrival of the paging signalling.

In providing the mobile radio communications device with a DRX pattern to be applied, and which consists of the DRX cycle period in addition to the time period for which it can be applied, the use of the IJTRAN in this manner not only advantageously improves the processing resources relating to, for example, CELL PCH and LTRA PCH states, but also leads to improved call setup times in those states and, if appropriate, removal of the requirement for a CELL FACH state.

Of course, it will be appreciated that similar radio states exist in other techniques such as Local Terminal Emulator techniques (LTE) and so the concept is equally applicable to LTE and IJTRAN access techniques.

Claims

CLAIMS

1. A mobile radio communications device for communication by way of a mobile radio communications network and having a power-saving mode employing discontinuous reception, the discontinuous reception being available in at least two discrete modes, and the device being arranged to receive a control signal from the network which signal includes timing data for controlling switching of the discontinuous reception between the two modes.

2. A device as claimed in Claim 1, wherein each of the two modes is arranged to offer a different period of disconnectivity.

3. A device as claimed in Claim I or 2, wherein the timing data includes identification of time periods for which each of the at least two modes is to operate.

4. A device as claimed in Claim 3, wherein the timing data serves to provide for a sequence of time periods of increasing periods of disconnectivity.

5. A device as claimed in Claim 3 or 4, wherein at least one of the time periods comprises an infinite time period during which the mobile radio communications device is advantageously arranged to maintain cell reselection performance requirements.

6. A mobile radio communications network device arranged to deliver a control signal to a mobile radio communications device connected to the network and having a power-saving mode employing discontinuous reception, and said control signal including timing data for controlling switching of the discontinuous reception between two discrete modes of operation.

7. A device as claimed in Claim 6 and arranged to deliver timing data serving to identify time periods for which the respective discontinuous reception modes are required to operate.

8. A device as claimed in Claim 7, wherein the timing data serves to define a sequence of periods of increasing disconnectivity.

9. A device as claimed in Claim 7 or 8, and arranged to identify cell re-selection requirements for each period.

10. A device as claimed in Claim 6, 7, 8 or 9, and arranged to initiate one of intra frequency measurements and inter frequency measurements, and inter-RAT measurements within the mobile radio communications device.

11. A method of controlling discontinuous reception in a power saving mode of a mobile radio communications device connected to a mobile radio communications network, including the steps of delivering from the network a control signal including timing data for controlling switching of the discontinuous reception between two discrete modes of operation.

12. A method as claimed in Claim II, wherein the two modes of operation offer different periods of disconnectivity.

13. A method as claimed in Claim 12, and including the step of including timing data within the control signal which serves to identify time periods for which the respective modes of operation are employed.

14. A method as claimed in Claim 13 and including the step of providing a sequence of time periods of increasing disconnectivity.

15. A method as claimed in Claim 12, 13 or 14, and including the step of delivering a control signal from the network having timing data representing at least one finite time period.

16. A method as claimed in Claim 11, 12, 13, 14 or 15, and arranged for controlling discontinuous reception in a power saving mode for a mobile radio communications device connected to a UTRAN.

17. A mobile radio communication device substantially as hereinbefore described with reference to, and as illustrated in, Fig. I and Figs. 2A-2C of the accompanying drawings.

18. A mobile radio communications network device substantially as hereinbefore described with reference to the accompanying drawings.

19. A method of controlling discontinuous reception in a mobile radio communications device substantially as hereinbefore described with reference to the accompanying drawings.