WO2008071600A1

WO2008071600A1 - Idle mode power saving for wireless terminals having multiple receivers in a wireless communications system

Info

Publication number: WO2008071600A1
Application number: PCT/EP2007/063292
Authority: WO
Inventors: Ulo Parts; Holger Wirz; Kim Kaltiokallio
Original assignee: Nokia Corporation
Priority date: 2006-12-11
Filing date: 2007-12-04
Publication date: 2008-06-19
Also published as: GB0624669D0; CN101558677A

Abstract

The present invention is related to reducing power usage by multiple receivers within a terminal, such as a mobile station, in a communication system, and more particularly, to reducing power usage by the receivers during idle mode in a wireless communications system. A terminal for a wireless communications system is described which includes a plurality of receivers arranged for receiving signals from a transmitter of the communications system; a power supply arranged for providing power to the receivers; and a processor arranged for controlling the provision of power to the receivers. When the state of the terminal is idle, power is provided between one or more of the receivers and, when the state of the terminal is active, power is provided to two or more of the receivers.

Description

IDLE MODE POWER SAVING FOR WIRELESS TERMINALS HAVING MULTIPLE RECEIVERS IN A WIRELESS COMMUNICATIONS SYSTEM

Field of the Invention

The present invention is related to reducing power usage by multiple receivers within a terminal in a communications system, and more particularly, to reducing power usage by the receivers during idle mode in a wireless communications system.

Background

A terminal is a communications device which includes an appropriate signal receiving and transmitting arrangement for enabling communication with a transmitter of a communications system. The communication may comprise, for example, communication of voice, electronic maii (email), data, multimedia, and so on. A mobile station is a portable terminal.

A communication system is a facility which facilitates the communication between two or more entities such as communication devices, network entities and other nodes. A communication system may be provided by one or more interconnected networks. One or more gateway nodes may be provided for interconnecting various networks of the system. For example, a gateway node is typically provided between an access network and other communication networks, for example a core network and/or a data network.

In multiple-input-multiple-output (MIMO) wireless communications systems the transmitting devices include at least two transmitting antennas and the receiving devices include two or more receiving antennas. MIMO utilises multi-path propagation to increase data throughput and range.

In an alternative communication system called single-input-multiple-output (SIMO) the transmitting devices utilises a single transmitting antenna to transmit communications to the receiving devices which utilise two or more receiving antennas to receive the communication.

Both MIMO and SIMO systems combine the signals received from the multiple receiving antennas (receivers) to formulate the communication transmitted from the transmitting device.

A drawback of both SIMO and MIMO systems is that the requirement for multiple receiving antennas taxes the power consumption and battery life of portable communications devices.

In cellular communications systems a network entity in the form of a base station provides a node for communication with mobile stations in one or more cells or sectors. It is noted that in certain systems a base station is called 'Node B'.

One cellular communication system is known as the Universal Mobile Telecommunications System (UMTS). Another system is known as Enhanced UMTS Terrestrial Radio Access Network (EUTRAN). EUTRAN is an example of a cellular communication system which uses SIMO or MIMO to transmit and receive communications between the base stations (EUTRAN Node Bs) and the mobile stations.

Mobile stations that are not receiving or transmitting communications are said to be in an idle state or mode.

The base station may inform a mobile station in idle mode that there is an incoming communication, such as an incoming call waiting, using a procedure called paging.

Paging messages may be transmitted over a common paging channel (PCH). One message may contain several paging records, each containing a paging request for a different mobile station. In principie the mobile station must monitor the PCH continuously to ensure that it does not miss any paging messages and therefore lose incoming communications. However, a continuous reception scheme would soon wear down the battery of the mobile station.

One method to alleviate this problem is the use of a discontinuous reception (DRX) scheme.

The DRX scheme is based on the fact that each mobile station has a unique IMSI (International Mobile Subscriber Identity) and using that IMSJ it is possible to compute paging occasions for this mobile station. Paging occasions are frame numbers, and the base station delivers paging messages for certain mobile stations on!y during their respective frame numbers.

Further power reduction is possible when a two-stage paging system is employed. The two-stage paging system utilises a paging indication channel

(PICH).

The mobile station listens to the PICH periodically, and when a positive indication appears, then the mobile station knows to listen for the actual PCH as it may only now contain a message addressed to this mobile station.

Several mobile stations may listen for the same paging occasion. Thus, the mobile station checks whether any of the paging identities of the received paging records matches its own identity. If a match occurs the communication is intended for the mobile station.

Mobile stations that are receiving or transmitting communications, excluding paging messages, with the base station are said to be in an active state or mode.

There is a desire to reduce the power consumption of multiple receivers for a mobile station when the mobile station is in an idle mode. It is object of the present invention to provide a mobile station for a Communications system which reduces power consumption by its multiple receivers, or at least provides a useful alternative.

Summary of the Invention

According to a first aspect of the invention there is provided a terminal for a wireless communications system, including: a plurality of receivers arranged for receiving signals from a transmitter of the communications system; a power supply arranged for providing power to the receivers; and a processor arranged for controlling power to the receivers such that power is provided to between one and a plurality of the receivers when the terminal is in an idle state and power is provided to two or more of the receivers when the terminal is in an active state.

When the terminal is in an active state, the terminal may combine information from the signals received by the two or more powered receivers to formulate data transmitted by the communications system.

When the terminal is in an idle state, the terminal may receive paging messages transmitted by the communications system. When the paging messages are unsuccessfully received, power may be provided to two or more of the receivers. When the paging messages are unsuccessfully received, power may be alternately provided between two or more of the receivers. The paging messages may include messages transmitted by the communication system during one-stage or two-stage paging.

When the terminal is in an idle state and reception of a signal for the at least one powered receiver falls below a first predefined threshold, power may be alternately provided between two or more of the receivers. When the termina! is in an idle state and reception of a signal for the at least one powered receiver falls below a second predefined threshold, power may be provided to two or more of the receivers.

The terminal may include a processor arranged for generating data by processing the signals received by two or more of the receivers using a multiple-input-multiple-output (MIMO) method. Alternatively, the terminal may include a processor arranged for generating data by processing the signals received by two or more of the receivers using a single-input-multiple-output (SIMO) method.

When the terminal is in an idle state, power may be provided discontinuousiy to the one receiver. Power may be provided discontinuousiy to the one receiver in accordance with a discontinuous reception (DRX) protocol.

Preferably, the termina! is a mobile station.

According to another aspect of the invention there is provided a controller for use with a terminal, including: a processor arranged for controlling power from a power supply of the terminal to a plurality of receivers of the terminal such that power is provided to between one and a plurality of the receivers when the terminal is in an idle state and power is provided to two or more of the receivers when the terminal is in an active state; wherein the receivers are arranged for receiving signals from a transmitter of a communication system.

According to another aspect of the invention there is provided a method for reducing power consumption of a terminal with a plurality of receivers, including the steps of: i) determining the state of the terminal; ii) when the terminal is in an idle state, a processor of the terminal controlling providing of power to between one and a plurality of the receivers; and iii) when the terminal is in an active state, providing power to two or more of the receivers.

Brief Description of the Drawings

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 : shows a schematic diagram illustrating a cellular communication system;

Figure 2: shows a schematic partially sectioned view of a mobile station that can be used for accessing a cellular communication system;

Figure 3: shows a diagram illustrating a circuit suitable for use in a mobile station in accordance with an embodiment of the invention.

Figure 4: shows a flow diagram in accordance with an embodiment of the invention.

Detailed Description of Preferred Embodiments

The present invention relates to reduction of power consumption in a terminal with multiple receivers during idle mode in a wireless communication system.

Power is provided to one receiver in the terminal during idle mode to receive idle mode messages, such as paging messages, from a transmitter(s) of the communications system unless reception of the idle mode messages is unsuccessful or affected. If reception is unsuccessful or affected then power may be provided to multiple receivers.

During active mode of the terminal, power is provided to all receivers to enable full MIMO/SIMO communication between the multiple receivers of the terminal and the transmitter(s) of the communication system. The present invention wiil be described in relation to the terminal being a mobile station. However, it will be appreciated that the present invention may be used with minor modifications for other terminals such as fixed stations.

Furthermore, the present invention will be described in relation to the mobile station use the MIMO or SIMO protocol to receive communications from the transmitter(s) of the communications system. It will be appreciated that other protocols which require the use of two or more powered receivers at the receiving terminal may also be used.

Before explaining in detail certain exemplifying embodiments, certain general principles of a wireless communication system and mobile station are briefly explained with reference to Figures 1 and 2.

A communication device can be used for accessing various services and/or applications provided via a communications system. In wireless or mobile systems the access is provided via an access interface between a mobile station 1 and an appropriate wireless access system 2.

A mobile station can typically access wirelessly a communication system via at least one base station 3 and or similar wireless transmitter and/or receiver node. Non-limiting examples of appropriate access nodes are a base station of a cellular system and a base station of a wireless local area network (such as WLAN). Each mobile station may have one or more radio channels open at the same time and may be connected to more than one base station.

A base station 3 is typically controlled by at least one appropriate controller entity 4 so as to enable operation thereof and management of mobile stations in communication with the base station. The controller entity 4 is typically provided with memory capacity and at least one data processor.

A mobile station 1 may be used for accessing various applications. For example, a mobile station 1 may access applications provided in a data network 5. For example, various applications may be offered in a data network that is based on the Internet Protocol (IP) or any other appropriate protocol.

In Figure 1 the base station node 3 is connected to the data network 5 via appropriate gateway 6. A gateway function between a base station node and another network may be provided by means of any appropriate gateway node, for example a packet data gateway and/or an access gateway.

Each base station 3 may have two or more transmitters. The transmitters may be arranged for performing MIMO functionality such as spatial multiplexing for enhancing the peak data transmission rate and/or beamforming.

Figure 2 shows a schematic partially sectioned view of a mobile station 1 that can be used for accessing a communication system via a wireless interface. The mobile station 1 of Figure 1 can be used for various tasks such as making and receiving phone calls, for receiving and sending data from and to a data network and for experiencing, for example, multimedia or other content.

The mobile station 1 may communicate with the communication system using radio signals 10 via an appropriate radio interface arrangement of the mobile station. In Figure 2 the radio interface arrangement is designated schematically by block 11. The interface arrangement may be provided for example by means of a radio part and associated antenna arrangement. The antenna arrangement may be arranged internally or externally to the mobile device.

The antenna arrangement may include two or more receivers. The receivers may be arranged for receiving signals from MIMO or SIMO transmissions. For example, the receivers can be arranged for beamforming to increase the gain in the direction of wanted signals and decrease the gain in the direction of interference and noise. Alternatively, or in addition, the receivers can be arranged for receiving spatially multiplexed signals from two or more transmitters. A mobile station 1 is typically provided with at least one data processing entity 12, at least one memory 13, and other possible components 14 for use in tasks it is designed to perform. The data processing 12 and storage entities 13 can be provided on an appropriate circuit board and/or in chipsets. This feature is denoted by reference 15.

The user may control the operation of the mobile station by means of a suitable user interface such as key pad 16, voice commands, touch sensitive screen or pad, combinations thereof or the like. A display 17, a speaker and a microphone are also typically provided. Furthermore, a mobile station may comprise appropriate connectors (either wired or wireless) to other devices and/or for connecting external accessories, for example hands-free equipment, thereto.

The mobile station may receive periodic status messages from a transmitter of the communications system when the mobile station is not transmitting or receiving communications. The status messages may include paging messages which indicate to the mobile station if a communication, such as an incoming call or multimedia message, is to be transmitted to the mobile station.

A mobile station not receiving or transmitting signals communications is in an idle state/mode.

When the mobile station is in an idle state, it has been determined by the inventors that not all the receivers may be necessary for receiving status messages. Therefore, in accordance with an embodiment of the invention, power to the receivers can be controlled so that, if necessary, power is provided only to one receiver.

it will be appreciated that the mobile station and the communication system may be using DRX in which case power may not be provided continuously to the one receiver. Power may be controlled to be initially provided to the one receiver which has better characteristics (for example, for previous received transmissions the receiver estimated better signal to interference ratio). Alternatively, based on previous received transmissions, power may be controlled to be initially provided to two or more receivers (for example, if in regard to previous transmissions the receiver estimated a low signal to interference ratio).

If the status messages transmitted by the communication system are unsuccessfully received by the mobile station, or if their reception is affected {for example, by interference), power may be provided to more than one receiver to boost the ability of the mobile station to successfully receive the status messages. Alternatively or prior to providing power to more than one receiver, power may be alternated amongst the receivers (for example, in an attempt to avoid the interference caused to the initial receiver).

In one embodiment if the signal-to-interference ratio (SIR) falls below a set threshold power may be alternated to another receiver and, if the SIR falls lower, below a second threshold, power may be provided to two or more of the receivers.

When it has been determined by the communication system that a communication is destined for the mobile station, and the mobile station has received a status message, such as a paging message, notifying the mobile station of the impending transmission by a base station of the communication, the mobile station may provide power to all of the receivers, or at least, to more than one of the receivers.

When receiving a communication from the base station the mobile station may combine information within the signals received by the powered receivers to generate the communication. For example, the mobile station may use the MiMO or SIMO protocol. The above method can be embodied in any access system providing wireless access by means of a wireless transceiver node where multiple receivers at the receiving node are necessary for full data throughput and range. For example, the access system architecture may be based on that known from EUTRAN and based on use of the EUTRAN Node Bs (eNBs) and mobile stations. Alternatively the architecture may be based on UMTS HSPDA (High- Speed Packet Download Access) which utilises MIMO transmissions.

A specific example for a circuit for a mobile station to reduce power usage by multiple receivers during idle mode is now described in more detail with reference to the circuit diagram of Figure 3.

Figure 3 shows a circuit suitable for a mobile station which receives MIMO or SIMO signals within a wireless communication system.

There is shown a power supply, such as a battery 30, connected to multiple receivers 31 and 32 via switches 33 and 34. Control lines 35 and 36 connect a processor 37 to the switches 33 and 34.

The receivers 31 and 32 may be digital receivers such as RF+ digital BB

(baseband).

The processor 37 is thus able to control whether power is provided to either of the receivers 31 and 32 by the power supply 30.

The processor 37 is connected 38 and 39 to the signal path 40 and 41 from both receivers 31 and 32.

The signal paths from both receivers are provided to an appropriate component 42 for processing the signals. The signals may be processed into data. Both signals may be used to generate the subsequent data. The data may be provided to a further appropriate component 43 which may utiϋse the data. For example, outputting the data to a user of the mobile station via a display or speaker.

The processor may also be connected 44 to the output from the multiple signal processing component 42 and a control line 45 may connect the processor to the multiple signal processing component 42.

An embodiment of the invention in use will now be described.

Power may be provided to one of the receivers 31. The processor 37 may determine from the output of the multiple signal processing component 42 for previous transmissions that the low signal to interference ratio (or high noise ratio) means that, to be able to successfully receive idle mode messages, power should be provided to both of the receivers 31 and 32.

When power is provided to only one of the receivers the processor 37 can control the multiple signal processing component 42 so that the signals from both signal paths are not combined.

The powered receiver 31 receives a transmission containing an idle mode message, such as a paging message, from the communications network.

If the reception of the signal from the receiver 31 is determined by the processor 37 to be of a low quality (low signal to interference ratio or high noise ratio), then the processor 37 controls the switch 34 to provide power to the second receiver 32.

When the mobile station is determined to be in an active state - the mobile station is to receive communications bearing signals - the processor 37 controls the switches 33 and 34 to provide power to both receivers 31 and 32.

An embodiment of the invention will now be described with reference to

Figure 4. A determination as to the state of the terminal is made in step 40. The determination may be made by processor 37 above.

If the state of the terminal is in idle mode then power is provided to one receiver in step 41. The provision of the power may be made by processor 37 by switching on either of switches 33 and 34.

If the state of the terminal is in active mode then power is provided to two or more receivers in step 42. The provision of the power may be made by processor 37 by switching on both of switches 33 and 34.

if the state of the terminal is in idle mode and idle mode messages are not being successfully received, then power may be provided to more than one receiver or alternately between the receivers. The processor 37 may determine unsuccessful reception by using feedback 44. The processor 37 may then control switches 33 and 34 by switching both on or by alternating which switch is on.

Embodiments of the present invention provide the advantage of reducing power consumption by a mobile station with multiple receivers during the reception of idie mode messages from a transmitter(s) of a communications network.

While the present invention has been illustrated by the description of the embodiments thereof, and while the embodiments have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details representative apparatus and method, and illustrative examples shown and described. Accordingly, departures may be made from such details without departure from the spirit or scope of applicant's general inventive concept.

Claims

1. A terminal for a wireless communications system, comprising: a plurality of receivers configured to receive signals from a transmitter of the communications system; a power supply configured to provide power to the receivers; and a processor configured to control power to the receivers such that power is provided to between one and a plurality of the receivers when the terminal is in an idle state and power is provided to two or more of the receivers when the terminal is in an active state.

2. A terminal as claimed in claim 1 wherein, when the terminal is in an active state, the terminal is configured to combine information from the signals received by the two or more powered receivers to formulate data transmitted by the communications system.

3. A terminal as claimed in any one of the preceding claims wherein, when the terminal is in an idle state, the terminal is configured to receive paging messages transmitted by the communications system.

4. A terminal as claimed in claim 3 wherein, when the paging messages are unsuccessfully received, power is provided to two or more of the receivers.

5. A terminal as claimed in claim 3 wherein, when the paging messages are unsuccessfully received, power is alternately provided between two or more of the receivers.

6. A terminal as claimed in any one of the preceding claims, when dependent on claim 3, wherein the paging messages include messages transmitted by the communication system during one- stage or two-stage paging.

7. A terminal as claimed in any one of the preceding claims wherein, when the termina! is in an idle state and reception of a signal for the at least one powered receiver falls below a first predefined threshold, power is alternately provided between two or more of the receivers.

8. A terminal as claimed in any one of the preceding claims wherein, when the terminal is in an idle state and reception of a signal for the at least one powered receiver falls below a second predefined threshold, power is provided to two or more of the receivers.

9. A terminal as claimed in any one of the preceding claims further comprising a processor configured to generate data by processing the signals received by two or more of the receivers using a multiple-input-multiple-output (MIMO) method.

10. A terminal as claimed in any one of claims 1 to 8 further comprising a processor configured to generate data by processing the signals received by two or more of the receivers using a single-input- multiple-output (SIMO) method.

11. A terminal as claimed in any one of the preceding claims wherein, when the terminal is in an idle state, power is provided discontinuously to the one receiver.

12. A terminal as claimed in claim 11 wherein, when the terminal is in an idle state, power is provided discontinuously to the one receiver in accordance with a discontinuous reception (DRX) protocol.

13. A terminal as claimed in any one of the preceding claims wherein the terminal is a mobile station.

14. A controller for use with a terminal, including: a processor configured to control power from a power supply of the terminal to a plurality of receivers of the terminal such that power is provided to between one and a plurality of the receivers when the terminal is in an idle state and power is provided to two or more of the receivers when the terminal is in an active state; wherein the receivers are configured to receive signals from a transmitter of a communication system.

15. A communication system including: one or more transmitters; and a plurality of terminals as claimed in claim 1.

16. A method for reducing power consumption of a terminal with a plurality of receivers, comprising: i) determining the state of the terminal; ii) when the terminal is in an idle state, a processor of the terminal controlling providing of power to between one and a plurality of the receivers; and iii) when the terminal is in an active state, providing power to two or more of the receivers.

17. A method as claimed in claim 16 wherein, when the terminal is in an idle state and signals are unsuccessfully received, providing power to more than one receiver.

18. A method as claimed in claim 16 wherein, when the terminal is in an idle state and signals are unsuccessfully received, providing power alternately between the receivers.

19. A computer program configured to effect the method of any one of claims 16 to 18.

20. Storage media configured to store a computer program as claimed in claim 19.