GB2392348A

GB2392348A - Estimating number of mobile terminals in a region to determine suitable means for downlinking

Info

Publication number: GB2392348A
Application number: GB0219515A
Authority: GB
Inventors: Alan Law; Christopher Pudney; Yannick Lepezennec
Original assignee: Vodafone Ltd
Current assignee: Vodafone Ltd
Priority date: 2002-08-21
Filing date: 2002-08-21
Publication date: 2004-02-25
Anticipated expiration: 2022-08-21
Also published as: GB2392348B; GB0219515D0

Abstract

Method of estimating the number of mobile terminals 5A-5J with a particular profile within a cell 1 or any other region. Also, a method of selecting on the basis of this estimate, a scheme of communication with those terminals. The selection may be between a simultaneous broadcast and selective downlinking to individual mobile terminals, the determining factor being a threshold of number of mobile terminals within the region. Method of estimating includes broadcasting a request for only mobiles with required profile to respond. Another criteria may be necessary for response e.g. a digit of the IMSI number or a random number generated in the terminal thereby getting only a sampled response. Other methods of estimation in CDMA systems include, measuring noise or interference levels after sending request for a response.

Description

TELECOMMUNICATIONS SYSTEMS

The present invention relates to a method and apparatus for obtaining an indication of the number of terminals in an area of coverage of a mobile telecommunications system, and also to a method and apparatus for selecting a scheme for communicating with the terminals in the area on the basis of such an indication of the number terminals in the area. In mobile telecommunications networks, such as GSM networks, it is known to transmit data individually to mobile terminals of the network by a short message service (SMS). An alternative method of data communication is a cell broadcast which simultaneously delivers a message to multiple mobile terminals in a specified area (usually a cell).

Transmitting data by cell broadcast is an efficient way of transmitting data to a large number of mobile terminals. However, if an identical message is only required to be transmitted to a relatively small number of terminals, for example, five, it may be more efficient to transmit this identical message individually to the terminals ("point-to-

point" transmission), for example, by means of SMS. If data is to be transmitted by cell broadcast, the signal must be transmitted at sufficient power such that the message can

2: be successfully received by a mobile terminal at the fringe of the cell, whereas the power required to successfully transmit the message by SMS will be set according to the particular circumstances of each of the mobile terminals which are to receive the SMS - allowing for the SMS to be transmitted with low power where, for example, a mobile terminal is located near to a transmitter.

The present invention seeks to provide a means by which an appropriate communication scheme may be selected to transmit data to a plurality of mobiles. For example, the method may allow selection between a cell broadcast and individual SMS communications such as to maximise efficient use of the capacity of a mobile telecommunications network.

It should be understood that the invention is not restricted to data transmission by SMS or cell broadcast. he invention seeks to allow an informed decision to be made as to whether to transmit data in an individual, point-to-point fashion or whether to transmit data simultaneously or substantially simultaneously to a plurality of terminals. The message could, for example, be a multimedia message (MMS) which could include text, animations, photographs, sounds and steaming audio and video.

According to a first aspect of the present invention, there is provided a method of obtaining an indication of a number of terminals in an area of coverage of a mobile

telecommunications system, the method including transmitting a special signal to tenninals within the area, which special signal is interpretable by each terminal to control the response of the terminal to the special signal; detecting a response from the terminals, and calculating, on the basis of the detection. the number of terminals in the area. According to a second aspect of the present invention, there is provided apparatus for obtaining an indication of a number of terminals in an area of coverage of a mobile telecommunications system, the apparatus including means for transmitting a special signal to terminals within the area, which special signal is interpretable by each terminal to control the response of the terminal to the special signal, and means for detecting the response from the terminals and calculating, on the basis of the detection, the number of terminals in the area.

According to a third aspect of the present invention, there is provided a method of selecting a scheme for communicating with terminals within an area of coverage of a mobile telecommunications system, including obtaining an indication of a number of terminals in the area in the manner defined above, and selecting a first communications scheme if the number of terminals is calculated to be below a predetermined threshold, and selecting a second communications scheme if the number of terminals is calculated to be equal to or greater than the predetermined threshold.

According to a fourth aspect of the present invention, there is provided apparatus for selecting a scheme for communicating with terminals within an area of coverage of a mobile telecommunication system, including apparatus for obtaining an indication of a number of terminals in the area as defined above, and means for comparing the determined number of terminals in the area with a threshold, and means for selecting a first communication scheme if the number of terminals is calculated to be below a predetermined threshold and selecting a second communication scheme if the number of terminals is calculated to be equal to or greater than the predetermined threshold.

Methods and apparatus embodying the invention will now be described, by way of example only, with reference to the accompanying drawing which shows schematically a cell and other elements of a mobile telecommunications network.

A mobile telecommunications network such as a GSM or 3G (UMTS) network, comprises a plurality of cells 1 (only one of which is shown), each of which is provided with at least one base station transceiver 3 which allows transmission and reception of data to and from mobile terminals SA to 50 within the cell 1.

Each of the mobile terminals 5A to 50 is provided with a smart card or SIM (subscriber identification module) which are used to activate the mobile terminals 5A to 50. The

SIM cards are specific to the customers of the network and carry information particular to each customer such as the customer's IMSI (international mobile subscriber identifier) and other data relating to the subscriber and the network - such as the subscriber's "profile", which will be discussed in more detail below. The S1M card allows a customer to activate their mobile terminal or, in general, any other suitable mobile terminal.

Base station 3 and other base stations (not shown) will be connected to a base station controller (BSC) 7. The base station controller 7 is in turn connected to a mobile switching centre (MSC) 9. The mobile switching centre 9 is connected to the public switch telephone network (PSTN) 11 which provides service for fixed telephone handsets. The geographical extent of the cell I which is served by the base station 3 depends on local radio propagation characteristics.

In known fashion, each mobile terminal 5A to 50 when powered on becomes registered with the local base station 3 (that is, the base station providing coverage to the cell 1 in which the handset is currently located). This registration is achieved by exchange of signals between the base station 3 and the mobile terminal. Via the base station controller 7, each base station 3 advises the current locations of the mobile terminals

5A to 50 in its cell I to the mobile switching centre 9, this information being stored in a home location register and/or a visitor location register (not shown). If a call is to be made to a particular mobile terminal, such as from a fixed handset in the PSTN 11 for example, the call is directed by the PSTN 11 to the mobile switching centre 9, using the telephone number of the relevant mobile terminal. The mobile switching centre 9 can then locate the particular mobile terminal from information in its home location register or visitor location register, and direct the call via the base station controller 7 to the correct base station 3 and thence to the particular mobile terminal.

If a mobile terminal wishes to make a call to a fixed telephone in the PSTN 11, the call is directed via the base station 3 of the calling mobile terminal cell 1 and is then routed via the base station controller 7 to the mobile switching centre 9 and thence to the called telephone.

When a mobile terminal moves from one cell to another cell, a hand-over procedure takes place by means of which the mobile terminal becomes deregistered from the base station 3 of the previous cell I and is registered with the base station of a new cell (not shown).

Transmitting and receiving frequencies used within a particular cell differ from those in adjacent cells, to avoid interference.

The foregoing is merely an abbreviated description of a known process carried out in a

GSM network and will be well known to those skilled in the art.

SMS messages may be sent to or from mobiles within a mobile network. However, in addition, short messages may be sent from a short message entity (SME) 13.

The network has a short message service centre (SMSC) 15 associated with it. The short message entity 13 is connected to the short message service centre 15 by a fixed network 17, such as a PSTN network.

Cell broadcast messages are transmitted from the SMSC 15 to the base station controller 7 which controls the cells in which it is desired to broadcast the message.

Each user of the network may have a particular user profile, data relating to which is stored on the mobile terminal or, more preferably, the S1M. The user profile data might indicate, for example, particular interests that a user has, such as membership of the supporters' club of a football team. This user profile data allows SMS messages or cell broadcasts offering services related to a user's interests, to be targeted to particular network subscribers. The user profile of a subscriber can be used to activate particular

cell broadcast channels of a mobile terminal which will enable the mobile terminal to receive cell broadcasts on the relevant channel.

If we assume that it is desired to broadcast a message to all mobile terminals having a particular user profile (profile A) within cell l, this can be done either by performing a cell broadcast in which the message is transmitted simultaneously to each mobile terminal having profile A within Me cell 1. Alternatively, an SMS can be sent separately to each mobile terminal having profile A within cell l As mentioned above, a cell broadcast must be made at a relatively high transmission power in order that the radio signal can be successfully received by mobile terminals at the fringe of the cell. In contrast, the strength of the signal to successfully transmit an SMS to an individual mobile terminal will be set by the network following an initial communication exchange with the mobile terminal to determine the minimum transmission power which will successfully transmit the SMS This transmission power will depend on the distance between the mobile terminal and the base station, and on atmospheric conditions and the like.

According to a feature of the present invention, a method and apparatus is provided for obtaining at least an approximate determination of the number of mobile terminals having a particular user profile within a cell (or any other geographical area). This allows a decision to be made as to whether it will be most efficient to transmit a

q message to each mobile terminal having the relevant user profile within the cell or other geographical area by means of a cell broadcast or by means of one or more individual SMS messages.

By way of illustration, the cell I might include a football stadium at which a football match is being staged. Members of the supporters' club of one of the teams are offered the facility by the telecommunications network to register their interest in the team.

Those subscribers registering this interest will be given user profile A. The operator of the network may then wish to offer the subscribers within the cell 1 data that might be of interest - for example, statistics related to the performance of a player or a video clip of a goal scored by a player - possibly in exchange for a fee which could be debited from the subscriber's account with the network. While a football match is being staged at the stadium within cell 1, there will be a large number of members of the supporters' club of the relevant team in the cell 1. An offer of data to the subscribers having profile A is therefore likely to result in a large number of requests for that data, possibly thousands of requests. However, at another time, when the stadium might be open to visitors, but during which no football match is being staged, an offer of a similar service may yield a much smaller number of responses, possibly one or two.

In this example, the geographical area in which it is desired to calculate the number of mobile terminals having profile A in cell 1, in which telecommunications facilities are

provided by base station 3. Of course, it should be understood that the area in which a calculation of a number of mobile terminals having profile A can be made could comprise a plurality of cells or could be a portion of a single cell. Such an area could be served by one, or more than one, base station.

Conventional mobile terminals for use on GSM and other networks incorporate a random number generator which can generate a random number between O and 1 on demand. The random value is stored on the mobile terminal. The stored value is referred to as the "persistency value". The nature of the persistency values is such that a random sample of terminals (such as found in a network cell 1) will generally have persistency values evenly distributed between O and 1. The persistency value is conventionally used to assist in the efficient operation of the network, as will be known to those skilled in the art, and the generation of these values will not be discussed further here.

In the Figure mobile terminals 5A to 5J have profile A (as indicated by the hatching) and terminals 5K to 50 do not. When the telephone network, via base station 3, wishes to provide each of the mobile terminals having profile A within cell I with a message (for example, an SMS, a MMS video clip or the like), as discussed above, a determination should advantageously be made as to the number of mobile terminals having profile A within the cell 1, in order that a decision can be made to use the more

efficient of a cell broadcast or individual (point-to-point) messaging. This could be done by paging all mobile terminals within the cell I to request a response from those terminals having profile A and counting the number of responses. However, in the event thee there are a large number of mobile terminals within the cell 1, the high volume of responses will consume a considerable proportion of the available radio spectrum within the cell 1, of which there is already likely to be a high demand due to the large number of mobile terminals within the cell 1. Also, a large amount of processing power will be required to process all the responses.

According to a feature of the invention, only a proportion of all Me mobile terminals with profile A respond to the page. For example, all the mobile terminals having profile A and with a persistency value of 0.1 or less could respond to the page. This is achieved by setting a persistency value threshold, which is transmitted with the page signal. the threshold can be varied between 0 and 1. The page signal instructs the terminal only to respond if it has a persistency value below the threshold (and of course only if it has profile A). In this example, the threshold is 0.1. On receipt of the page signal the threshold value will be determined, and only mobile terminals with a persistency value below 0.1 will respond.

In the cell 1 shown in the Figure, if we assume that the persistency values attributed to the mobile terminals SA to 5J are 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 and 0.9,

respectively, this will result in only mobile terminal 5A responding to the page (the persistency values of the other terminals are not relevant because they do not have profile A, and will not respond to the page for that reason). The threshold value is selected such that 10% of the mobile terminals within the cell I having profile A will I respond. A processor associated with base station 3 will therefore be able to calculate that the single response received indicates that there are ten (or approximately ten) mobile terminals having profile A within the cell 1. If, for example, the characteristics of the network are such that it is more efficient to use a cell broadcast to transmit a i message where there are more than five mobile terminals within the cell 1 that require the message, the information derived will allow a decision to be made that the message is transmitted to each of the mobile terminals 5A to 5J within the cell 1 by means of a cell broadcast. Alternatively, if the characteristics of the network are such that it would only be efficient to transmit a message by cell broadcast if the total number of mobile terminals in the cell I that require the message exceeds 20, the infonnation derived will allow a decision to be made that individual messages should be sent to each of the mobile terminals within the cell 1.

In a further example, there are 50,000 mobile terminals within a cell I, of which 30,000 have profile A. In this network a decision is made to page all mobile terminals within the cell l by transmitting a threshold of 0.01. This will result in 1% (or approximately l %) of the mobile terminals having profile A within the cell 1 responding. Therefore, in

)3 response to the page, approximately 300 responses will be received. A calculation (number of responses/persistency threshold value) can then be performed to estimate that there are 30,000 mobile terminals having profile A within the cell 1.

Therefore, advantageously, the determination that there are 30,000 mobile terminals having profile A within the cell 1 has been made, but requiring only 300 responses from the mobile terminals, thereby making efficient use of the available radio spectrum and signal processing power.

The threshold transmitted by the base station 1 to each of the mobile terminals within the cell 1 may be changed. The value could be set so that a statistically useful number of responses is likely to be obtained. The best threshold value may vary from cell to cell. For example, a network operator could set a low threshold value for cells in highly populated areas or areas that are periodically heavily congested such as railway stations or sports stadiums According to another feature of the invention, the threshold could be set initially to a relatively low value. This will prevent wasting available radio spectrum in the event that there are an unexpectedly large number of mobile terminals having the relevant user profile within Me cell. However, when the number of mobile terminals in the cell is low, the number of responses may not be statistically useful (and may be zero). In

ILi, such an instance, the processor controlling the base station 3 will increase the threshold value so that a greater proportion of the terminals will respond. If the number of responses is statistically useful, then an accurate estimate of the number of mobile terminals within the cell 1 having profile A can be made. However, if the number of responses is still not statistically useful, the threshold value can be increased again, and this process can be reiterated until a statistically useful number of responses is obtained.

According to a second embodiment of the invention, the mobile terminals within a cell 1 (or other area) are paged by sending a paging signal requesting a response to the base station 3 only from mobile terminals with profile A and having a particular value of some identification code associated with the terminal. For example, this identification code could be a digit of the IMSI stored on the terminal's SIM card. The last digit of the IMSI on the SIM card of each terminal will be between O and 9 (and will generally be evenly distributed between any random sample of mobile terminals). According to this embodiment, the base station 3 can obtain a response from 10% of the terminals by sending a paging signal requesting a response only from terminals having an IMSI with the last digit below 1, or can, for example, obtain a response from 20% of the terminals by asking for a response only from terminals having a last digit of their IMSI below 2, etc.

Of course, a code other than the lMSI, and a digit other than the last digit, could be used. Also, a code stored on the terminal itself, rather than the SIM, could also be used.

The first and second embodiments are suitable for mobile telephone networks of any type, such as a GSM or 3G network.

A third embodiment will now be described which is particularly suitable for 3G-type networks using COMA technology.

In the third embodiment each mobile terminal within the cell (or other pre-defined area) is paged and is requested to respond with a particular power value (Prepay)' if it has profile A, and otherwise not to respond. As will be understood by those skilled in the art, when a plurality of mobile terminals operating according to CDMA technology simultaneously respond, the response signals will interfere and generate noise within the cell. According to the third embodiment, a processor associated with the base station 3 detects the change in the noise level within the cell, and this is used to estimate the number of mobile terminals responding to the page signal (which is the number of terminals within the cell 1 having profile A as each terminal within the cell I is paged and requested to respond if it has profile A) The level of noise caused by the

16? responses of the mobile terminals will depend on the number of terminals within the cell having profile A and the power of their response signals. As the power of the response signals is known, the number of terminals responding can be estimated.

An increase in noise level below a certain value may not provide an accurate indication of the number of mobile terminals within a cell that have profile A and are responding to the page. In the event that an increase in noise level below a certain value appears, a second page signal is transmitted requesting a response higher power value Prep'',, from each terminal having profile A. This process can be repeated until a sufficiently high increase in the noise level occurs such that an accurate determination of the number of mobile terminals having profile A within the cell can be made.

In the third embodiment, the content of the response from the terminals is irrelevant. It is simply the power of the responses that provides an indication of the number of terminals within the cell having profile A. In the third embodiment, because a signal transmitted between the base station and a terminal, and likewise between a terminal and the base station, is attenuated in proportion to the distance that the signal travels, mobile terminals at the fringe of the cell will contribute less to the noise generated by the response signals than mobile terminals close to the base station. To avoid this influencing the estimation made of the

number of terminals responding, when each terminal receives the page signal from the base station, including the value Prepay a calculation is made at the mobile terminal such that the actual power of the response signal (Prespond) should compensate for the distance between the mobile terminal and the base station.

The page signal is transmitted by the base station with a transmission power P,ransm,,.

The power of the signal when it is received by the mobile terminal is Preserved The path loss Ppl = P''ansmt Preceded Because the paging signal includes data indicating the value P',,,nsm',, the mobile terminal can determine the path loss, Pp'. The mobile terminal also has data including the noise floor (Nr) within the cell.

So that the distance between the mobile terminal and the base station does not affect the estimation of the number of terminals within the cell, the power of the response message of the mobile terminal is set thus: Prespond Ppl Nr + Prep',.

The techniques of the first to third embodiments can be combined.

Claims

in CLAIMS

1. A method of obtaining an indication of a number of terminals in an area of coverage of a mobile telecommunications system, the method including transmitting a special signal to terminals within the area, which special signal is interpretable by each terminal to control the response of the terminal to the special signal; detecting a response from the terminals; and calculating, on the basis of the detection, the number of terminals in the area.

2. A method according to claim 1, wherein the special signal causes only a proportion of the terminals within the area to transmit a predetermined response.

3. A method according to claim 2, wherein the special signal causes only terminals having a predetermined user profile to transmit the predetermined response.

4. A method according to claim 2 or 3, wherein each of the terminals has a value associated therewith within a predetermined range of values, and the special signal causes only terminals within the area to respond where the value stored on a terminal is within a predetermined sub-range of said range.

5. A method according to claim 4, wherein the values associated with each of the terminals within the area are substantially evenly distributed within said range.

6. A method according to claim 4 or 5, wherein the value is a random number generated by the terminal.

7. A method according to claim 4 or 5, wherein the value is derived from identification data relating to the terminal.

8. A method according to claim 7, wherein the value is the IMS1 associated with the terminal.

9. A method according to any one of claims I to 8, wherein the special signal controls a characteristic of the response 10. A method according to claim 9, wherein the characteristic is the power of the response signal A method according to claim 1O, wherein the power of response signal is adjusted to compensate for the distance between each terminal and the receiver of the signal.

12. A method according to any one of claims 1 to 11, wherein the telecommunication system is a CDMA system.

1 3. A method according to any one of claims 9 to 11, wherein the telecommunication system is a GSM system.

14. A method of selecting a scheme for communicating with terminals within an area of coverage of a mobile telecommunications system, including obtaining an indication of the number of terminals in the area according to any one of claims I to 13, and selecting a first communications scheme if the number of terminals is calculated to be below a predetermined threshold, and selecting a second communications scheme if the number of terminals is calculated to be equal to or greater than the predetermined threshold. 15. A method according to claim 14, wherein the first scheme communicates separately to terminals in the area.

16. A method according to claim 15, wherein said first communications scheme comprises transmitting an SMS or MMS to the terminals.

ÀzI 17. A method according to claim 14, wherein the second communication scheme communicates simultaneously to the terminals.

18 A method according to claim 17, wherein the second scheme comprises transmitting data to the terminals by means of a cell broadcast.

19. A method according to any one of claims 14 to 18, wherein the threshold is set at a level at which the second communication scheme becomes more efficient than the first communication scheme.

20. Apparatus for obtaining an indication of a number of terminals in an area of coverage of a mobile telecommunications system, the apparatus including means for transmitting a special signal to terminals within the area, which special signal is interpretable by each terminal to control the response of the terminal to the special signal, and means for detecting the response from the terminals and calculating, on the basis of the detection, the number of terminals in the area.

21. Apparatus according to claim 20, wherein the special signal causes only a proportion of the terminals within the area to transmit a predetermined response.

zz 22. Apparatus according to claim 2 l, wherein the special signal causes only terminals having a predetermined user profile to transmit the pre-predeteTmined response. 23 Apparatus according to claim 21 or 22, wherein each of the terminals comprises means for storing a value within a predetermined range, and wherein the special signal causes only terminals where the stored value is in a predetermined sub-range of said range to respond.

24 Apparatus according to claim 23, wherein said stored values of the terminals within the area are substantially evenly distributed within said range.

25. Apparatus according to claim 23 or 24, wherein each terminal includes means for generating random numbers, for generating said value.

26 Apparatus accordingly to claim 23 or 24, wherein each terminal stores identification data identifying a terminal to the telecommunication system, and wherein said value is derived from this identification data. e 27 Apparatus according to claim 26, wherein said value is derived from the IMSI.

28. Apparatus according to any one of claims 20 to 27, wherein the special signal controls a characteristic of the response.

29. Apparatus according to claim 28, wherein the characteristic is the power of the response signal.

30. Apparatus according to claim 29, wherein the power of response signal is adjusted to compensate for the distance between each terminal and the receiver of the signal. 31. Apparatus according to any one of claims 20 to 30, wherein the telecommunication system is a CDMA system.

32. Apparatus according to any one of claims 28 to 31, wherein the telecommunication system is a GSM system.

33. Apparatus for selecting a scheme for communicating with terminals within an area of coverage of a mobile telecommunication system, including apparatus for obtaining an indication of a number of terminals in the area according to any one of claims 20 to 32, and means for comparing the determined number of terminals in the area with a threshold, and means for selecting a first communication scheme if the

czar number of terminals is calculated to be below a predetermined threshold and selecting a second communication scheme if the number of terminals is calculated to be equal to or greater than the predetermined threshold.

34. Apparatus according to claim 33, wherein the first scheme communicates separately to terminals in the area.

35. Apparatus according to claim 34, wherein said first communication scheme comprises transmitting an SMS or MMS to the terminals.

36. Apparatus according to claim 33, wherein the second communication scheme communicates simultaneously to the terminals.

37. Apparatus according to claim 36, wherein the second communication scheme comprises transmitting data to the terminals by means of a cell broadcast.

38. Apparatus according to any one of claims 33 to 37, comprising means for setting a threshold at a level at which the second communication scheme becomes more efficient than the first communication scheme.

39. A method or apparatus substantially as hereinbefore described with reference to and/or as illustrated in the accompanying drawing.