WO2002051171A2

WO2002051171A2 - Method for determining the designation of a paging message in umts

Info

Publication number: WO2002051171A2
Application number: PCT/IB2001/002586
Authority: WO
Inventors: Osmo Pulkkinen; Pekka Toppila
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 2000-12-21
Filing date: 2001-12-19
Publication date: 2002-06-27
Anticipated expiration: 2003-06-21
Also published as: AUPR218400A0; WO2002051171A3

Abstract

The present invention relates to paging in telecommunication systems. More particularly, the present invention relates to the determination of a paging reference in a telecommunication system. The present invention provides in a telecommunication system, a system of determining a reference for determining the designation of an incoming message, the telecommunication system including a network node and at least one user equipment device (UE) supporting a corresponding unique subscriber identity reference (SI), the network node and UE each calculating the reference to determine the designation of the incoming message, the system includes a method including the steps of: a) upon entering a registration area, forwarding the corresponding SI to the network node; b) at each of the UE and network node, extracting/determining at least four digits of SI; c) each of the UE and network node calculating the reference using the result of step b). Preferably for UMTS networks, step b) includes performing at least one of the following operations SI mod 10000 or SI div 10000, or SI Mod 100000 or SI div 1000000.

Description

A METHOD AND DEVICE FOR DETERMINING A PAGING REFERENCE FIELD OF INVENTION

The present invention relates to paging in telecommunication systems. More particularly, the present invention relates to the determination of a reference for determining the designation of an incoming paging message in a telecommunication system. In one form the invention relates to the calculation of a paging reference for Radio Network Control and Mobile Paging systems. It is to be appreciated, however, that the invention is most particularly suited to use in UMTS telecommunication systems. BACKGROUND OF INVENTION

The procedures for, inter alia, User Equipment (UE) in idle mode in a Radio Access network have recently been developed in the 3rd Generation Partnership Project Technical Specification for Group Radio Access Network, 3GPP TS 25.304 (Release 1999). Generally, in a mobile telecommunication system, when user equipment

(UE) is switched on, it searches and selects a public land mobile network (PLMN) using a certain radio access technology (RAT) such as UMTS Terrestrial Radio Access (UTRA). The UE searches for a suitable cell of the chosen PLMN and chooses that cell to provide available services, and tunes to its control channel. This choosing is known as "camping on the cell". The UE will then register its presence, by means of a Non-Access Stratum (NAS) registration procedure, in the registration area of the chosen cell, if necessary. If the UE finds a more suitable cell of the selected PLMN, it reselects onto that cell and camps on it. If the new cell is in a different registration area, location registration is performed. If necessary, the UE will look for more suitable cells on other PLMNs at regular time intervals, which is referred to as PLMN-reselection. If the UE loses coverage of the registered PLMN, either a new PLMN is selected automatically (automatic mode), or an indication of which PLMNs are available is given to the user, so that a manual selection can be made (manual mode). In the context of the present invention, the following scenario illustrates the purpose of camping on a cell in idle mode. If the PLMN receives a call for the registered UE, it knows (in most cases) the registration area of the cell in which the UE is camped. It can then send a paging message for the UE on control channels of all the cells in the registration area. The UE will then receive the paging message because it is tuned to the control channel of a cell in that registration area and the UE can respond on that control channel. In idle mode, the UE may use Discontinuous Reception (DRX) in order to reduce power consumption. When DRX is used, the UE needs only to monitor one Page Indicator, PI, in one Paging Occasion per DRX cycle, or more generally, page monitoring cycle. In Frequency Division Duplex (FDD) mode, the DRX cycle length is 2^k frames, where k is an integer. The UE may be attached to different Core Network (CN) domains with different CN domain specific DRX cycle lengths. The UE stores each CN domain specific DRX cycle length for each CN domain the UE is attached to and uses the shortest of those DRX cycle lengths.

In the existing standard, the UE uses the International Mobile Subscriber Identity (IMSI, a unique subscriber identity reference), the Cell System Frame Number (SFN), the number of page indicators within a frame in FDD mode (Np, given as part of system information), Frame offset (Frame offset = 0 for FDD), Page Block Periodicity (PBP =1 for FDD) and the DRX cycle length to determine the Paging Occasion.

The value of the Paging Occasion (i.e. the SFN of the first frame of the Paging Block) is determined as follows:

Paging Occasion = {IMSI mod (DRX cycle length)} + n x DRX cycle length

Where n = 0,1 ,2... as long as SFN is below its maximum value. The actual Page Indicator within a Paging Occasion that the UE reads is similarly determined based on IMSI. The Page Indicator to use is calculated by using the following formula:

PI = {IMSI div (DRX cycle length div PBP)} mod Np A telecommunication system ordinarily includes a network end, for example a network node, and a subscriber end, for example a UE. The PO and PI calculations are required at both ends. Both ends must have the same calculation function to work smoothly. In the above examples, the basic PO and PI functions have already been standardised. The method of calculation in these standards have practical disadvantages, particularly at the UE end. The above formulae use the entire IMSI number, which has a maximum of 15 digits. According to ITU/ETSI/3G... technical specifications, the IMSI is defined to have 6 to 15 digits, where the digit type is INTEGER (0...9). The modulo/div calculation for a 15 digit long IMSI number requires a lot of processing power. It takes a relatively long time to carry out the calculations and looses system capacity, placing a particularly high burden on the system, especially at the UE end.

It is an object of the present invention to provide a system and method of determining paging references in a telecommunication system, which ameliorates or overcomes at least one of the disadvantages of the prior art. It is also an object of the present invention to provide a system and method of determining paging references in a telecommunication system that allows for a large distribution of unique subscriber identity reference (SI) numbers within a given page monitoring cycle.

It is a further object of the present invention to provide a system and method of determining paging references in a telecommunication system with reduced consumption of processing capacity and therefore lower processor cost. SUMMARY OF INVENTION

In one aspect the present invention provides, in a telecommunication system, a method of determining a reference for determining the designation of an incoming message, the telecommunication system including a network node and at least one user equipment device (UE) supporting a corresponding unique subscriber identity reference (SI), the network node and UE each calculating the reference to determine the designation of the incoming paging message, the method including the steps of: a) upon entering a registration area, forwarding the corresponding SI to the network node; b) at each of the UE and network node, extracting/determining at least four digits of SI; c) each of the UE and network node calculating the reference using the result of step b).

Preferably, step b includes each of the UE and network node performing at least one of the following operations, SI mod x, or, SI div x, or simply removing a number of digits so that only at least four digits are left. Any digits can be removed, but preferably, the most significant digits are removed.

In another aspect the present invention provides a telecommunication device, including logic means for determining a reference, the reference being adapted to determine a designation of an incoming message, said logic means determining the reference in accordance with the following steps: a) determining a unique subscriber identity reference (SI); b) extracting/determining at least four digits of SI, such as by performing, SI mod x; or SI div x; c) calculating the reference using the result of step b).

In essence the invention stems from the realisation that choosing an operation that results in reducing the SI to at least 4 digits will suffice to allow distribution of unique Si's within a given DRX cycle. Previously, the use of an operation upon the unique subscriber identification number (SI) prior to calculating the paging reference will use a lot of calculation time and the processing power required to perform the determination of the reference. The main problem in the existing method is to use the max. 15 digits long IMSI number in the mod/div calculations. Further to this, in one embodiment of the invention as applied to a UMTS network, the maximum DRX cycle length (in which a UE monitors for paging) is given by 2¹² = 4096. More generally, in practice this means removal of at least digits 7-15 instead of a mod operation. In practice, the invention may use only the at least 4 least significant digits of the IMSI for the PO calculation and may use only the at least 6 least significant digits of the IMSI for the PI calculation. So for UMTS networks, the operation of step b) includes SI Mod X, where X may be 10000 for the PO calculation or X may be 1000000 for the PI calculation respectively. This is enough, because the max. DRX cycle length is 2¹² = 4096.

If two UE's have the same PO/PI, the present invention still has effect, but it means that both UE's are powered at the same time. The present invention allows a large distribution of differing or unique Si's or subscribers to be catered for in a given DRX cycle. At the same time, the invention allows for the reduction of overhead required for processing such a large distribution of differing subscribers.

Preferably, the unique subscriber identity reference, SI, is an IMSI.

Preferably, the reference is a Paging Occasion (PO). Preferably, the calculation in step c) is performed according to:

PO = {(IMSI mod 10000) mod (DRX cycle length)} + n*(DRX cycle length) where

DRX cycle length = the time interval length between monitoring a Paging Occasion frame for a given UE, and -1 = 0, 1 , 2 ... .

Preferably, the reference is a Paging Indicator (PI).

Preferably, the calculation in step c) is performed according to:

PI = {(IMSI mod 1000000) div (DRX cycle length)} mod Np where DRX cycle length = the time interval length between monitoring a Paging

Occasion frame for a given UE, and

Np = the number of Paging Indicators per message frame.

Preferably, the method of the present invention includes the step of: performing a checking operation to ensure that the UE and the network node calculation results are the same.

Preferably, the telecommunication device of the present invention is at least one of a mobile user equipment device (UE) or a network node. The network node may include, for example, a Base Station Controller BSC or a Mobile Switching Centre MSC. Preferably, the method or device of the present invention is included in a telecommunication system, a telecommunication network, or a telecommunication protocol. DESCRIPTION OF PREFERRED EMBODIMENTS

The following is a description of a preferred embodiment of the present invention as applied to a UMTS network. The IMSI includes a large number of bits (64), which is considered to include16 digits. In the prior art, the following steps are followed to perform a calculation of a reference in a paging system.

Take IMSI number (max. length 15 digits)

Translate the IMSI number to a 64 bit long IMSI variable Calculate the Paging Occasion using the given formula and the 64 bit long IMSI variable

Calculate the Paging Indication using the given formula and the 64 bit long IMSI variable.

According to the methodology of the present invention, however: Take IMSI number (max. length 15 digits)

Take at least 4 least significant digits from the IMSI number. This corresponds to the various operations, for example, such as modulo 10 000, or modulo 1000000,

SI div x or selecting at least four digits operation, all of which result in only at least four digits being selected. There is no need to make the modulo calculation for the long IMSI number. It is considered that 4 digits are enough for calculating the

PO and 6 digits are enough for calculating the PI, because the max. DRX cycle length is 2¹² = 4096

Translate the at least 4 digit long part of IMSI number to an at least 16 bit long part of IMSI variable Calculate the Paging Occasion for example using a 16 bit long part of IMSI variable

Calculate the Paging Indication for example using a 24 bit long part of IMSI variable

Furthermore, in another preferred form of the invention, the mod-operation is replaced by an operation to remove at least the digits 7-15 from the IMSI number. The invention results in the saving of processing capacity, because now calculations can be made using, for example, at least 4 digit (16 bit) variables or 6 digit (24 bit) variables instead of 16 digit (64 bit) variables required by the existing standard.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. In a telecommunication system, a method of determining a reference for determining the designation of an incoming message, the telecommunication system including a network node and at least one user equipment device (UE) supporting a corresponding unique subscriber identity reference (SI), the network node and UE each calculating the reference to determine the designation of the incoming message, the method including the steps of: a. upon entering a registration area, forwarding the corresponding SI to the network node; b. at each of the UE and network node, extracting or determining at least four digits of SI, c. each of the UE and network node calculating the reference using the result of step b).

2. A method as claimed in claim 1 , wherein determining the at least four digits in step b includes at least one of: performing an operation, SI mod x; wherein x = at least 10000; or performing an operation SI div x, and ignoring any remainder, or selecting at least four digits from the SI.

3. A method as claimed in claim 1 or 2, wherein the unique subscriber identity reference, SI, is an IMSI.

4. A method as claimed in claim 1 , 2 or 3, wherein the reference is a Paging Occasion (PO).

5. A method as claimed in claim 4, wherein the calculation in step c) is performed according to:

PO = {(IMSI mod 10000) mod (DRX cycle length)} + n*(DRX cycle length) where DRX cycle length = the time interval length between monitoring a Paging Occasion frame for a given UE, and n = 0, 1 , 2 ... .

6. A method as claimed in claim 1 , 2, or 3, wherein the reference is a Paging Indicator (PI).

7. A method as claimed in claim 6, wherein the calculation in step c) is performed according to:

PI = {(IMSI mod 1000000) div (DRX cycle length)} mod Np where

DRX cycle length = the time interval length between monitoring a Paging Occasion frame for a given UE, and

Np = the number of Paging Indicators per message frame.

8. A method as claimed in any one of the previous claims, including the step of: performing a checking operation to ensure that the UE and the network node calculation results are the same.

9. A telecommunication device, including: logic means for determining a reference, the reference being adapted to determine a designation of an incoming message, said logic means determining the reference in accordance with the following steps: a. determining a unique subscriber identity reference (SI); b. at each of the UE and network node, extracting or determining at least four digits of SI; c. calculating the reference using the result of step b).

10. A telecommunication device as claimed in claim 9, wherein determining the at least four digits in step b includes at least one of: performing an operation, SI mod x; wherein x = at least 10000; or performing an operation SI div x, and ignoring any remainder, or selecting four digits from the SI.

11. A telecommunication device as claimed in claim 9 or 10, wherein the unique subscriber identity reference, SI, is an IMSI.

12. A telecommunication device as claimed in claim 9, 10 or 11, wherein the device is at least one of a mobile user equipment device (UE) or a network node.

13. A telecommunication device as claimed in any one of claims 9 to 12, wherein the reference is a Paging Occasion (PO).

14. A telecommunication device as claimed in claim 13, wherein the calculation in step c) is performed according to:

PO = {(IMSI mod 10000) mod (DRX cycle length)} + n*(DRX cycle length) where

DRX cycle length = the time interval length between monitoring a Paging Occasion frame for a given UE, and n = 0, 1 , 2 ... .

15. A telecommunication device as claimed in any one of claims 9 to 12, wherein the reference is a Paging Indicator (PI).

16. A telecommunication device as claimed in claim 15, wherein the calculation in step c) is performed according to:

PI = {(IMSI mod 1000000) div (DRX cycle length)} mod Np where

DRX cycle length = the time interval length between monitoring a Paging Occasion frame for a given UE, and Np = the number of Paging Indicators per message frame.

17. A UMTS telecommunication system including a method as claimed in any one of claims 1 to 8.

18. A UMTS telecommunication system including a device as claimed in any one of claims 9 to 16.

19. A method or protocol as herein described.

20. A network, system or device as herein described.