DESCRIPTION MOBILE RADIO COMMUNICATIONS NETWORK LIST STRUCTURE

Technical Field [0001]

The present invention relates to a mobile radio communications network list structure for use within a mobile radio communications device allowing for user selection or automatic selection of a mobile radio communications network from the said list and, in particular, to USIM PLMN list structures .

Background Art

[0002] A current arrangement for automatic PLMN selection, or for the construction of a PLMN menu for manual selection, relies on a number of standardised lists held in the USIM, so-called selector lists such as the Equivalent Home PLMN selector (EHPLMN) , the User Controlled PLMN selector, and the Operator Controlled PLMN selector. [0003]

These lists are in the form of a linear sequence of PLMNs and the position or rank of each PLMN in the list defines its priority in relation to the others. In use, User Equipment (UE) such as a mobile radio communications device

may discover PLMNs which are not found in the sequence. Such PLMNs have no priority ranking between themselves and so are ranked lower than any of the listed PLMNs.

[0004] Further, a PLMN operator may have an agreement with several others operating in a foreign country. Assuming further PLMNs exist in that country, the operator can consider it preferable to list some of the PLMNs of that country in the SIM cards it issues to its customers, in order to rank those PLMNs which are part of the agreement above any other PLMN. However, this also introduces a priority ranking between the PLMNs within the agreement which may be undesirable. For example, if A and B are two PLMNs with similar coverage, one of them has to have the highest priority, say A. Any UE in an area where the coverage by A is intermittent, while B offers stable coverage, is at a disadvantage since, with A having the highest priority, it must reselect a cell from A whenever it recognises a suitable cell irrespective of the relative coverage. If, for example, the UE could rank A and B with the same priority, in areas where the coverage by one PLMN is more stable than the other, the UE would remain with the most adequate PLMN all the time thereby saving battery life. Unfortunately, the operator does not have that option. Rather, it could randomize the arbitrary priority order between users to mitigate the issue,

or it could effective give equal priority to all PLMNs by listing neither A nor B in the USIM, in which case, UEs might try to select any other PLMN which is of course undesirable.

[0005] A desirable feature is the ability to at least specify that certain subsets of the PLMNs listed in the USIM selectors have equal priority and an example of this is seen from Fig.l. [0006] This drawing represents tables illustrating the first version of a selector list for networks H, A, B, F and K and their associated implied priority, i.e. the priority implied by there positioning by the listing, and the desired priority having regard to aspects such as level of availability. As will be appreciated, a linear list is indicated. [0007]

The alternative selector list of version B illustrates a non-linear listing in which networks A and B are paired of a common priority, and networks F, K. are paired for a lower common priority. [0008]

As will be appreciated, networks A and B have equal priority, but are both less preferable than network H and more preferable than either of networks F or K. That implies, for example, that if the UE locates PLMNs A and B while H is

not available, then the UE can choose randomly between A and B.

[0009]

Ideally, the operator can have even more control such that networks A and B are not necessarily selected on an equal probability basis. For example, at the 3GPP workshop on Network Selection, NTUK suggested (doc NSW-060007) it was suggested that the PLMNs be assigned a probabilistic weight, equal weights being equivalent to equal priority and higher weights favouring the selection of the associated PLMNs.

Disclosure of Invention

[0010]

Such solutions could of course be implemented with new Elementary File structures in the USIM as for example from

NSW-060007 mentioned above and also from Fig. 2. UEs aware of the new files would look for them on the USIM and use them if found. Otherwise they would revert to existing procedures. However, such an arrangement poses a maintenance problem, with information to be maintained in two files so as to allow portability of the USIM between different kinds of UEs, and the 3GPP has confirmed there will be no change to the structure of the USIM.

[0011] The present invention therefore seeks to provide for a

mobile radio communications network list structure having advantages over known such structures, yet compatible with the position of the 3GPP.

[0012] As will be appreciated a range of solutions of increasing complexity to the problem and limitation of the current art are provided. The invention can serve to add structure to the existing linear sequence of PLMNs by inserting notional brackets into the list. This is done without any change to the USIM as the notional brackets can materialise by at most two reserved PLMN IDs. PLMNs within a pair of such notional brackets would have the same priority. [0013]

According to a first aspect of the present invention there is provided a mobile radio communications network list structure for use in a mobile radio communications device arranged for user-selection from entries in the said list and comprising a linear list of network identifiers for the said user selection, the said linear list including markers serving to delineate at least one subset of entries in said list, the said delineated entries having selection priorities defined by way of the said list. [0014]

It will be appreciated therefore that the present invention can provide for an arrangement for specifying

network selection priorities within, for example a mobile phone handset, and in an advantageous and more flexible manner than is currently achieved, for example with USIM PLMN preference lists. As a particular feature, such selection priorities can be specified without requiring any structural change to the memory element and its associated files and, in one particular aspect, the arrangement can employ existing USIM features in an advantageously backwards-compatible manner, to provide additional priority information as required.

[0015]

Through employing existing features of, for example, the USIM, a mobile radio communications device such as a mobile phone handset arranged for use in accordance with the invention can derive a non-linear classification of the list entries having, for example, equal priority as the sub-set of network identifier, whereas legacy devices will still readily interpret the preference list as a linear ordering of network identifiers . [0016]

Preferably the said marker can comprise a specifically reserved network identifier such as, for example, a PLMN identifier. [0017] In this manner the said identifier can comprise an

identity from within an international shared codes range.

[0018]

As a further option, said marker can be provided from a class of identifiers. Then, the said class of identifiers can be derived by way of a common Mobile Country Code.

[0019]

As an alternative, the said marker can comprise an identifier including a specific attribute distinct from an access-technology attribute. Here the said specific attribute can be provided with one of a variety of possible values for delineating the said subset.

[0020]

As a further aspect of the invention, the said selection priorities can be defined by way of probability scaling factors.

[0021]

As one particularly advantageous feature, the said markers can also provide for the said priority scaling factors . [0022]

In this regard, the mere presence of the said markers can be arranged to identify the entries within the said sub- list as having equal priority.

[0023] As an alternative the said relative selection

priorities of entries in the subset can be derived from the Mobile Network Code.

[0024]

As another option, the said relative selection priorities in the subset can be defined by values of an access-technology attribute associated with a said marker.

[0025]

As a further option, the relative selection priorities of entries within the subset can be defined by way of an additional specific attribute distinguished from the access- technology of the attribute.

[0026]

As such, the said specific additional attribute can be derived from meta data relating to a file structure. [0027]

Advantageously, the said specific value can be employed within the said further attribute to provide for relative probability profiling of the entries in the said subset.

[0028] In one embodiment of the invention, a common marker can be employed for indicating the start and end of the said subset .

[0029]

Alternatively, different respective markers can be employed for identifying the start, and end, of the said

subset .

[0030]

It should also be appreciated that the invention memory element including a network list structure as defined above. As an example, the said memory element can comprise a Subscriber Identity Module.

[0031]

Yet further, the invention can provide for radio communications device including such a memory element.

Brief Description of Drawings

[0032]

The invention is described further hereinafter, by way of example only, with reference to the accompanying drawings in which:

Fig. 1 comprises a tabular illustration of a network structure according to current art;

Fig. 2 comprises a tabular illustration of an example of a network structure as proposed to the 3GPP; Fig. 3 comprises a tabular illustration of a list structure according to an embodiment of the present invention;

Figs. 4-6, comprise list structures similar to that of Fig. 3 demonstrating the backwards compatibility of the invention, showing on the right-hand side that, no matter how

legacy UEs interpret duplicate entries (such as the markers might be) , the linear priority order for real PLMNs they eventually derive is the same as without the markers; and

Figs. 7-9 comprise tabular representations of list structures according to yet further embodiments of the present invention with different probability profile arrangements .

Explanation of Reference [0033]

18, 20, 26, 28, 34, 36 Entry

Best: Mode for Carrying Out the Invention

[0034] As noted above, in one aspect of the invention one or two PLMN IDs are assigned a specific purpose within the invention. UEs arranged to operate in accordance with the invention can interpret these specific markers as "opening bracket" and/or "closing bracket" within the lists. Any PLMNs listed within such notional brackets form a subset having, in a basic format, equal priority. This is illustrated in Fig. 3. [0035]

Here, a linear list selector representation 10 is provided along with its associated interpretation by way of a UE according to the present invention. As will be appreciated,

the interpretation provides for the grouping of respective pairs of networks A and B; and F and K with common priorities but by means of a linear list representation 10.

[0036] This scheme requires only one special PLMN ID for implementation as nested sets are not required and so advantageously the two kinds of brackets could be implemented with a single common marker. Of course such specific PLMN IDs should never be assigned to any real PLMN. They will then not interfere with the processing by legacy UEs which will in any case simply not recognise such entries as having any special characteristics, such legacy UEs will find no physical information in the USIM relating to these apparent PLMNs and so will not identify them when scanning for PLMNs. One potential issue is that selector lists normally do not contain duplicate entries, which is likely to happen with the brackets seen as PLMN IDs. However, having regard to the manner in which legacy UEs might handle duplicates when reading selector lists (i.e. whether they delete the first instance of a duplicate, or the last, or do not delete duplicates at all) , it can be shown that, although the implicit priorities of the real PLMNs may differ (different ranks in the derived lists) , the relative order of real PLMN entries remains the same in all cases, as illustrated in Figs.4, 5 and 6.

[ 0037 ]

Each of Figs. 4, 5 and 6 illustrate the same linear list representations 14, 22, 30, and their related respective interpretations by UE that are not capable of operating in accordance with the present invention. [0038]

In Fig. 4, the first instance of a duplicate marker is removed and although entries 18, 20 in the interpretation list have the appearance of a PLMN, no match is in fact ever achieved. With regard to the version of Fig. 5, the second instance of a duplicate is removed from the interpretation list and, in this example, entries 26, 28, although having an appearance of a PLMN, likewise remain unmatched.

[0039] The embodiment of Fig. 6 is such that no duplicates are removed from the interpretation list 32 and, again, although entries 34 and 36 have the appearance of a PLMN, they remain unmatched.

[0040] The present invention proves advantageous since it can achieve the benefits of equal relative priorities which improve on pure linear priority schemes whilst also providing backwards-compatibility for legacy UEs, which simply derive a priority order within the subsets in the same way as without the invention.

[ 0041 ]

Further advantageous features can readily be incorporated. For example, insofar as dummy entries in the PLMN selector lists will be ignored, they can be made more elaborate, at no detriment to the operation of legacy UEs.

Part of the marker entry could include a code which serves to index into a standardized table of probability profiles. For example, the code can be provided in the "open bracket" marker entry and applies to all the PLMNs found in the following sub list. Such profiles can define selection probabilities in the following way. For example each profile can comprise a list of numbers, e.g. 50, 25, 15, 7, 3. If that list is shorter than, or has equal length with, the corresponding PLMN sub list, the numbers represent PLMN selection probabilities to apply. That is:

- l ^st PLMN in sub list: 50%

- 2 ^nd PLMN in sub list: 25%

- 3 ^rd PLMN in sub list: 15%

- 4 ^th PLMN in sub list: 7% - 5 ^th PLMN in sub list: 3%

- Further PLMNs in sub list: 0% (effectively pointless to have more than 5 PLMNs with this profile)

[0042]

If however there are fewer PLMNs in the sub list than there are numbers in the profile, a scaling factor could be

applied such that the probability of selecting any PLMN is indeed 100%. [0043]

Through providing a table of profiles to choose from, it becomes possible to vary the steepness of probability decline through the sub list. With a rapid decline, it is pointless to have more PLMNs than the point where the selection probability would be almost zero. If more PLMNs must be included, then a slower declining profile should be chosen. The requirement is to define probability decline curves and they need not be approximated by a set of values. Any definition that is agreed as standard will suffice, such as using mathematical formulae. The notional bracket marker entry only includes a code, not a list of probability values. One of the profile codes can be employed to denote the equal probability case, which should be defined as such, rather than a list of numbers, since it is a limit case where the list length is not really relevant.

[0044] The invention then advantageously allows for existing USIM selector lists that can support a priority structure having far richer information content than a simple linear ranking.

[0045] In a further arrangement, a reserved PLMN identity, or

an identity within the International Shared Codes range, is reserved to act as a marker in USIM selector lists. For example: MCC = 901, MNC = 98. When this is found as the index of an entry in a selector list, UEs arranged to operate in accordance with the invention will take its first occurrence (and any subsequent odd occurrence) to indicate the start of a sub list, starting with the next entry following the natural list succession. Also, the second occurrence (and any subsequent even occurrence) of this identity is taken as a marker of the end of the current sub list. PLMN identities within a sub list are given equal priority, lower than any identity preceding the sub list (in natural list succession) and higher than any identity following the sub list. [0046] A similar convention can be employed in a further embodiment but wherein two PLMN identities are specially reserved, one to indicate the start of a sub list (i.e. opening bracket), one to indicate its end (i.e. closing bracket) . [0047]

In another example, the start of sub list marker is not defined by a single PLMN identity, but rather by a class of identities based on the same Mobile Country Code (MCC) , currently unassigned, such as MCC = 899. The Mobile Network Code (MNC) can then be used as an index into a table of

probability profiles. It should be appreciated that a profile is any definition of a function {natural number} -> [0, 1], providing a probability value for each PLMN within a sub list, and considered as numbered sequentially from zero. This is illustrated in Fig. 7. The number of PLMNs in the sub list may be smaller than the number of probabilities defined in the profile, so a scaling factor would then be applied to compute actual selection probabilities. Of course the UE implementation may skip that as long as the relative selection frequencies it applies match the profile. Of course such probabilities should be agreed by a standardization body. [0048]

Then, any entry with an MCC equal to the start of sub list marker (opening bracket) is treated as in the earlier embodiments, thus delimiting a sub list. In addition to the above, instead of equal relative priority between the members of the sub list, relative priorities are weighted by the function indexed by the MNC of the PLMN identity marking the start of sub list, according to their position in the sub list. Such an aspect is illustrated in Fig. 8. [0049]

A further embodiment, and one that shares similarities to the above, is that the probability function index is no longer coded by the MNC, but by values of the access technology attribute associated with the dummy entries

marking the start of a sub list marker. A particular further advantage of this aspect is that, only one or two PLMN identities need to be reserved for the sub list markers. Although the meaning of the access technology attribute is violated, this is of course only within the special (dummy) entries and the attributes of which can only be ignored by legacy UEs, since no real PLMN will ever be found as a match. [0050]

Any likely limitation of the above could be avoided by creating a new type of attribute to be used instead of the access technology attribute for the coding of the probability profile selector. This further alternative embodiment would rely on the meta data relating to a SIM file. It would also indicate a longer record length, allowing legacy UE ' s to still read the selector lists properly. [0051]

Further, and using such a new attribute which would be ignored by any UE that did not know of it, it becomes possible to avoid special entries (i.e. reserved PLMN identities) altogether. PLMN entries in a selector list which had the new attribute can then double-up as normal entries and start or end of sub list markers. Of course, UEs which ignore that attribute will see a linear selector list as before. For UEs arranged to operate in accordance with this embodiment the attribute and its value could have the

following meaning:

- A special value (e.g. all bits set) indicates that the attribute is unset.

- A value other than any of the special reserved values indicates the start of a sub list including the current entry.

The actual value selects the probability profile to apply to the sub list, which could be the equal probabilities profile.

- A special value (e.g. zero) indicates the last entry in the sub list. [0052]

Such features and possibilities are illustrated in Fig. 9. A selector list representation 46 is provided along with a list interpretation 48 by way of UE arranged in accordance with the present invention. [0053]

The new attribute within the linear list 46 serves to confirm that profile 3 should be applied to the group 50 of PLMNs and profile 5 should be applied to the group 52 of PLMNs in the UE interpretation. [0054]

A variant of this embodiment would of course allow a scenario of a single element sub list: the end of sub list marker is in the entry following the last entry in the sub list (i.e. ends the sub list but excluding the current entry) . This requires a few more conventions: The end of a list would

be implicit in the cases that: a start of sub list appears while still, apparently, within a sub list; and at the end of the selector list itself (in case it ends with a sub list) .

[0055] As will therefore be appreciated, the invention relates to a logical structure added to the list by way of special list entries and a particular feature of the invention is that the physical structure in the memory device supporting any such list remains the same in most embodiments or is only altered by the meta data already standardized. [0056]

The present invention can therefore provide for a list structure which can be readily employed within, as above, SIM of a mobile radio handset, or other mobile terminal device, which can offer features perceived to be particularly advantageous by both network operators and users insofar as more appropriate network selection can be made and thereby more efficient use of remaining battery charge.

[0057] While the invention has been particularly shown and described with reference to exemplary embodiments thereof, the invention is not limited to these embodiments. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention

as defined by the claims. [0058]

This application is based upon and claims the benefit of priority from British patent application No.0721744.1, filed on November 6, 2007, the disclosure of which is incorporated herein in its entirety by reference.

Industrial Applicability

[0059] The present invention provides a mobile radio communications network list structure for use within a mobile radio communications device allowing for user selection or automatic selection of a mobile radio communications network.