The truth about 3 digit Mobile Network Codes (MNCs) E.212

Despite the title, I don't know the full truth about Mobile Network Codes and whether they can be 2 digit or 3 digits long. However, I'm getting an ever bigger suspicion no one really does. So after talking to experts from various telco's and standardisation organisations for more than a year and just before I head into a new world, I thought I write down everything I've learned about Mobile Network Codes as defined in ITU recommendation E.212. This is not all there is to know and I hope others will chime in. There is so much misinformation and Fear, Uncertainty and Doubt, that it is hurting the development of the industry as a whole. I do have the sincere feeling, I'm the first person in a decade to fundamentally look at these numbers and the impact they have on the telecommunications market. I haven't seen any studies by any other researcher looking at these numbers at all. (Please prove me wrong, I would so love to see some other nutcase who looks at this stuff in-depth, preferably one who is way better than me and teaches me something new).

You're a policy maker and you need to know what to do

Before dismissing the potentially billions of euros of unrealized potential in the market and not changing a damn thing to the way MNC's are assigned, please ask a very very good and honest researcher to look into this. As far as I know there is no reason to be against this plan. But I am one person. I'm often right, but I may not be. After a year of searching though nobody I met who has serious mobile network knowledge has said I'm seriously bonkers and it cannot be done. Here is what I know. Don't be afraid to be critical. Do know, no one is paying me for this position. 

A Mobile Network Code is digits 4 to 6 of a 15 digit IMSI. 
As you may know, your SIM-card carries a unique number, the 15 digit IMSI number. (there are more unique numbers for an IMSI, but this is the important one). This number is used in the network to identify the mobile subscriber. Based on the IMSI the network knows whether the SIM should be allowed access, the type of access it should be granted and where to route the bits too.

The pre-paid SIM-card from the Dutch supermarket MVNO Albert Heijn I bought yesterday as a temporary replacement has IMSI: 204122030140166. Decoding it leads to the following knowledge:

• 204 is the Mobile Country Code of the Netherlands. Why it is necessary for mobile networks to know countries, I don't know. But it is in the spec. There are some operators like Digicel, who use one MCC 338  for their whole network in many different countries, deeming it too hard to work with an MCC for every Caribean Island and technically speaking they are right. Vodafone could easily use on MCC for all nations it operates in. Nothing breaks if you use an Italian MCC in Vatican city. Though it somehow is against best practices and the ITU doesn't like you doing it and wants operators and regulators to report extra territorial use of MCC's and MNC's
• 12 is the Mobile Network Code of Telfort. This used to be an indepent MNO with its own mobile network. It was bought by KPN, who switched of Telforts network and now Telfort is an MVNO on KPN's network. MNC's are issued by national regulators. In Vatican City this may well be Radio Vatican or the pope himself. The combination of MCC and MNC uniquely identifies the network. The E.212 spec says that the number can be 2 or 3 digits long. In Europe it is two digits long. In the rest of the world Wikipedia seems to show 3 digits are used as well. For instance Honduras, Columbia and the United States. 
• 2030140166 is the Mobile Subscriber Identitification Number: In this case it is 10 digits long, per the standard it could also be 9 digits long. That gives every mobile operator at least a billion and up to 10 billion numbers. Though it could be issued completely at random, it does seem there is further logic in the number. For instance I heard that the first x digits are sometimes used to point at a specific Home Location Register, which keeps track of where SIM-cards are in the network. It seems HLR's can only accomodate x million devices per HLR. If you expect more than x million devices, using the first digits allows for easy internal routing of traffic.  Furthermore specific MVNO's, like my supermarket MVNO may get their own range, so maybe 2030 is unique to Albert Heijn. Again, if they grow, it becomes easier to shift them to different or dedicated HLR

MCC + MNC are also broadcasted by the network base stations.

Apart from being used on the SIM-card, the MCC+MNC is also broadcast by the networks base stations. Your mobile phone receives these announcements and will select these networks either based on a list of preferred networks that it has listed on the SIM or by just trying all these networks. The number broadcasted should always be 5 digits I heard. This has something to do with base stations, for instance those used for CDMA. It is hard to get good information on this, but it seems to be a hard restriction for some networks. It may be more than just legacy in the core network, it may be that this is hardcoded into end-user devices too. So it may be that your phone only expects to see a 5 digit number broadcast from a base station and will not respond to a 6 digit one. What this doesn't mean is that your device only logs on to a network that has the same MCC+MNC combination as the one broadcasted. Again, take my phone. The SIM uses 20412 as MCC+MNC, but it doesn't latch on to Telfort's network anymore. That network doesn't exist anymore instead it chooses to work on 20408 or 20410, which are KPN's. It shows this in the home screen. In a foreign country, a phone is very promiscuous and latches on to whatever network has the strongest signal, that is willing to give it access. 

Proposition to let large scale end-users manage own Mobile Network Codes. 

As said in previous posts, I propose to open up access to MNC's to anyone wanting to become an MVNO for instance for their smart metering project. The benefits are enormous. It would allow:

- easier switching of mobile operators, without having to physically switch the SIM-cards of one operator for another

- better coverage and less black spots through national roaming

- cheaper international roaming through more competition

- more innovation, because it is the end-user who is in charge. 

This is scary stuff.. or to quote a telco guy it is quite extreme, controversial and maybe can not or should not be implemented. The main reason why I think it could work is that no argument is ever made against the 4 points as being something a customer needs. Even better, the 3GPP is researching solutions for these problems, except it only looks at technical solutions and these technical solutions fail because of the administrative overhead they require and the fundamental breach of GSM security models. The proposition looks at changing the rules under which someone can get a number, instead of trying to change numbers post-hoc.  Every argument against it seems to focus on how hard it could be and how this is untested. 

The proposition isn't untested. All I'm proposing is roaming 

What everyone seems to forget is that mobile roaming is doing exactly what I'm proposing. Every telco has hundreds of roaming agreements. Every telco allows hundred of thousands if not millions of devices on its network every day, with whom it has absolutely no relationship what so ever. The only thing the network is interested in is; what network does this SIM belong to. Do we have a roaming agreement with it. If yes, grant access and start billing. If no, deny it access. 

The arguments agains doing this are mostly based on FUD. 

A well known tactic in the IT industry to discredit any product or idea is to use Fear, Uncertainty and Doubt. The proposition discussed here has seen its fair share. The work I did on it was mostly aimed at finding out if there was any basis for this FUD, so that it was valid criticism. The easiest to dispel are arguments about:

• Demand: Critics say customers don't want this, we never heard them ask for it. First of all, for a regulator this should be irrelevant. Limiting supplies to a resource shouldn't be about whether or not someone wants it or not, but about whether they could get it if they wanted it and whether or not that would be a problem. And yes there is demand in the market, quite a lot actually. The Dutch Defense department already has its own MNC and is very happy with it. (but they have guns, so its a different request)
• Operational difficulty: Critics say that running a telco is hard. Customers can't be trusted to run HLRs etc. This is true, operations are hard. That is why many telcos outsource their operations to companies like Ericsson. Yes you heard it right. Ericsson runs many networks totalling well over 750 million active customers. So why can't an end-user hire Ericsson, Huawei or a smaller company to do the same for it. 
• It is too expensive: Not what I heard. Seems you can be done with a figure in the low hundred thousands euro for a full set up. Some speculate it could become less if the market becomes bigger. 
• It will become too big and need too many numbers. I tried to find out the numbers and it seems most people I speak to intuitively think the amount of interested companies is too big for this to work. However, just looking at the statistics for the Netherlands, out of 844,000 companies in The Netherlands only 15,000 have over 50 employees, and only 7850 of those over a 100 employees. Most of these companies aren't interested in these new ideas. They are accountants, schools, NGO's etc. I guessed that for the Netherlands the upper limit would be 1500, but a realistic number for the next 15 years is closer to 200 or even lower. The Netherlands might run out of MNC's, but the whole of Europe, with dinky toy countries like Luxembourg, Andorra, Liechtensteyn, Jersey, Guernsey etc. could get very far. And really, if I could get 50,000 end-user MVNO's online in the next three decades, with this idea, I would be ecstatic. Just imagine the competition and the benefits. But to counter this and to not get into prolonged negotiations in the ITU for nations to reform the way MCC's are used, I propose to move to 3 digit MNC's and according to some, this will unleash network Armageddon, shatter the space-time fabric and as a result destroy the entire functioning of the mobile network. This last one is rather nasty and based on a GSM Europe letter from the year 2000, that I will delve a bit deeper into. 

Moving to three digits will not lead to mobile network Armageddon

In the past Europe and the USA have discussed moving to three digit mobile network codes. This was always faced with heavy opposition from the GSM Association and its predecessor. Though the people at the GSMAs central office are very nice, I do have some misgivings about its perspectives on public policy and the functioning of the mobile market. Mobile roaming or Mobile termination access anyone? ;-)

The argument is outlined in a letter from 2004 which is available on the ATIS-website. The nice thing is that it is a letter which has enabled track changes.  Running it through Google docs and looking at the HTML, the entire text is below the fold. It turns out the original letter is one sent to CEPT/ECTRA in 2000. And yes the letter is still seen by some as valid as I've seen these points pop up in discussions and even saw some points quoted verbatim in mails. There is also a message from the 3GPP on the topic, which provides a bit of background. However it was written after the letter to CEPT/ECTRA and it quotes those points directly, so I'm not thinking it was written indepently. 

The argument is:

1. Call back of the released 2-digit SIM card – this could affect all current GSM users (around 500 million in Europe). 
2. The handset display may not be ready for such a change – this could cause severe confusion with all existing GSM handsets. 
3. Change of all existing roaming agreements with the need to re-run all the performed tests. 
4. Enormous efforts in terms of investment and manpower in order to change network elements and billing systems, thereby reducing the innovation power of mobile operators. 
5. Inability for many operators to roam with the second operator where 3-digit MNCs have been issued in a country with no ability to identify an operator by the first 2 digits.

None of these arguments is true. They can be debunked I think. (If you feel otherwise, please tell me so)

1. Callback of all SIM-cards isn't necessary. The proposal isn't to split all existing two digit MNC's in 10 3 digit MNC's and hand these out to different organisations. So the plan isn't to split 20412 into 20412X and to let Telfort only keep 204120 and give 204121 to a smart metering project. Nope, what has been issued has been issued. So none of the SIM-cards have to be revoked.
2. The handset display has developed massively in the last 10 years. But even then. We aren't talking about changing existing networks. It might even be necessary for backwards compatibility to let those that run networks still use 2 digit MNC's by effectively giving them a block of 10 consecutive 3 digit MNC's. Nothing says this can't be done. 
3. Roaming agreements only need to be tested for new networks using the three digit MNC, as all existing networks will remain doing the same thing they did before. So no changes there. Furthermore roaming agreements are tested regularly. Things always change in networks. Testing is essential to this. 
4. An enormous effort in network elements and billing systems. This may be true, but only for those networks that didn't comply with the standard. According to my sources, some networks assumed standards compliance in their networks and needed to identify more digits then 6 to find MVNO's and HLR's anyways, so they are ready for any length of an MNC. Furthermore, that is business. Things change. Windows versions get upgraded and loose backwards compatibility. If this was a real argument, cars still wouldn't have safety belts. 
5. Inability to roam seems rather unlikely. The 15 digit IMSI is what is used. That doesn't change by looking at either the 5th or the 6th digit. And as said, it isn't necessary to change the base stations. If they need 5 digits, that can still be accomodated. 

Loose end: Global Title Translation 

Realizing I don't know everything. Do know I see Global Title Translation as a loose end. I don't know precisely how it works, but it feels from the descriptions that there shouldn't be a fundamental difficulty there either. It may however require some work.

Update Loose end: How it is processed "on the air"
Good point by my friend TT. A serious question is how an MNC is sent over the air. Is it that it is sent as part of an IMSI string and indistinguishable from the rest of the IMSI, if so the network wouldn't care about the length of the MCC+MNC bit. If not, the length may be of interest. He found in some ETSI documentation that the IMSI is broken down into separate parts of MCC+MNC+MSIN. The MNC is sent separately over the air as 3 digits. That is nice, because this means that three digits should be understood by the network as it gets a 3 digit field that it needs to deal with. Will investigate further. 

So what to do

Before dismissing the potentially billions of euros of unrealized potential in the market and not changing a damn thing to the way MNC's are assigned, please ask a very very good and honest researcher to look into this. As far as I know there is no reason to be against this plan. But I am one person. I'm often right, but I may not be. After a year of searching though nobody I met who has serious mobile network knowledge has said I'm seriously bonkers and it cannot be done. 

GSM Association

                            Mr. Alain Doisneau

                                                                                                  Chairman Project Team Numbering

                                                                                   

Subject: Mobile Network Codes (MNCs) – Change from 2digits to 3 digits

Dear Mr. Doisneau,

GSM Europe has recently been following the developments concerning CEPT/ECTRA’s intention to formally adopt a Decision on the expansion of Mobile Network Codes from 2 to 3 digits (draft Decision attached). 

GSM Europe is the European regional interest group of the worldwide GSM Association, the premier global body behind the world’s leading wireless communications standard. GSM Europe represents around 159 mobileoperators in 50 regions in Europe with around 200 million subscribers.

I understand that the adoption of ECTRA’s Decision, which was originally scheduled for the CEPT/ECTRA meeting on 21st June 2000, was postponed further to concerns raised by industry. Further to its preliminary analysis, GSM Europe shares such concerns and believes a change in MNC from 2 to 3 digits is most likely to have severe implications for almost the entire GSM system (See Annex). The main consequences from our point of view would be:

¨ Call back of the released 2-digit SIM card – this could affect all current GSM users (around 200 million in Europe)

¨ The handset display may not be ready for such a change – this could cause severe confusion with all existing GSM handset

¨ Change of all existing roaming agreements with the need to re-run all the performed tests

¨  Enormous efforts in terms of investment and manpower for the changes in the network elements and the billing system, thereby reducing the innovation power of mobile operators

GSM is not convinced of the urgend need to initiate those changes. It does not feel that the costs and risks to be incorporated by the operators only are in any way justified by potential advantages. Especially new operators, operators which a dense infrastructure to provide special home services and operators building up a UMTS network could face more problems for migration than others.

In light of the abovementioned issues, GSM Europe strongly supports the idea of having a workshop open to all parties concerned in order to identify the technical difficulties and assess if and when these problems can be overcome. Such discussions, it is felt, would bring some clarifications to CEPT/ECTRA and other parties concerned on the real implications of an alteration in the MNC digits number. With regards to the timeframe, it would seem appropriate to hold a workshop organized by ETO in September 2000, so that adequate measures can be taken in a timely manner.

You will find attached in annex an analysis paper drafted by our experts expressing the views of GSM operators. The paper seeks to outline the technical issues relating to the introduction of 3-digit Mobile NetworkCodes and the possible consequences associated to this change.

I hope the attached document will be of interest to you.

Yours sincerely,

……..

Copie: Marco Bernardi

              Alisdair McLead

              Leo Koolen

Annex

 

Technical Issues Relating to the introduction of Three Digit Mobile Network Codes (MNCs).

Introduction / Background

The MNC is a component of the IMSI (International Mobile Subscriber Identity), the other components been the Mobile Country Code (MCC) and the Mobile Station Identification Number (MSIN).

Figure 1 IMSI Structure

The MNC is an inner element in the IMSI with a defined length of 15 digits. The whole IMSI is marked on the SIM-card. To this extend, the IMSI must not be mismatched with the subscriber's number which is e.g. in GSM an E.164 number.

Various GSM entities will interpret the extra MNC digit as part of another field (MSIN), which will consequently lead to inconsistencies within the interaction between various parts of the whole GSM System.

The IMSI is used to:

·       Identify a (roaming) customer, for

·       Network internal purposes used in all signalling in the PLMN, in

·       Interaction with the Mobile Terminal and for

·       BackOffice applications like charging, billing and accounting

As the National Regulatory Authorities (NRAs) are responsible for the establishment and publication of conventions for IMSIs (IMSI = MCC + MNC + MSIN), the change of the current MNC allocations (e.g. 03 may become 030 or 003) may lead to severe problems as the length of the IMSI is fixed and the structure / usage of the MSIN is subject to each individual operator.

It should be noted that for the time being, out of a total of 300 MNCs actually in use, 14 are 3 digit MNCs. Furthermore, there are no assignments for 3 digit MNCs outside the US, where 5 US Operators where assigned such MNCs. In terms of operators this corresponds to 1.7 % of the GSM Operators.

It should be noted that this paper does not claim to be exhaustive and further in depth analysis is required.

Technical implications for the introduction of 3-digit MCNs:

SIM Cards:

The IMSI is an inherent part of all SIM cards,. This would hence require a replacement of all existing SIM cards with new ones. Taking into account the number of mobile users and prepaid cards, such exercise is practically not feasible (e.g. in Germany about 35 Millions of SIM Cards are produced, or are submitted to the customers, with a rapidly increasing proportion of prepaid cards). The costs of this procedure are expected to be quite high due to production of new SIM cards, SIM card distribution and logistics, customer service, activation of the new SIM cards, and customer handling. The activation/provisioning part raises questions about the capacity of the IT and networks systems. It would be quite likely that most operators would be forced to build up additional capacity to be able to manage the migration. Some customers would experience problems and would temporarily unable to use their mobile, which means loss of revenue from the operator's point of view. In addition to this it is doubtful, that SIM card chips can be produced to serve all carriers in due time.

As a result the co-existence of 2 and 3 digit MNCs can only be the subject of further analysis.

Handsets:

The introduction of a 3 digit MNC will certainly result in a number of compatibility problems between existing mobile equipment and the SIM, and also very likely between MS and the network. With respect to compatibility problems in the interface between SIM and the software of ME, two cases can easily be identified:

1              SIM with a new IMSI structure built up by three digit MNC combined with an ME running old software that isn't prepared for the new IMSI structure. The ME will in this case attempt to read the extra MNC digit as part of another field. This case will be difficult to solve as there are about 250 Million legacy mobiles in operation throughout Europe.

2              SIM with an old IMSI structure build up by two digits MNC combined with a ME running new software, expecting the new IMSI structure. Here it is much easier to find a solution, but the problem has to be addressed in order to find some kind of IMSI type identification on the SIM.

In other words, either a large number of terminals would have to be replaced, a very long lead time (longer than the typical life span of a mobile terminal) would have to be allowed, or the problems in the transition phase would have to be accepted by users and operators.(Further Input is welcome by other GSMA groups !!!!)

Network:

The IMSI analysis would need to be redefined .

All subscriber records would need to be modified to change the MNC from 0X to 0X0 or 00X. In the case of multiple HLRs, as is the case with nearly all operators, the level of planning and coordination would be substantial.

IN the case of redundant HLRs redundancy the data would need to be changed on both the live and backup locations.

In addition to this, many of the operators would have to reconfigure their Base Station Subsystem so that it transmits a LAI which contains the new 3 digit MNC. This causes operational costs. In addition it would demand additional operational capacities, which especially operators, who are still in the phase of 2G network rollout or who have (some additionally) plans to built up a 3G network may not be manage in a sufficient way, so that customers will not be frustrated. 

If FNR was in service it would also need updating.

Billing & Customer Care Systems:

The billing systems of most networks use the IMSI for the generation and gathering of billing information. A change in the MNC would require severe modification to billing systems and protocols. All effected subscriber records would need to be modified TAP-Files (TAP-Incollect/Outcollect) TAP 2 / TAP 2+.

Roaming:

Regarding Roaming, the IMSI analysis for all European operators (e.g. approximately 100 in Eircell’s case) will have to be changed in every MSC.

All roaming testing would have to be redone and would be more complex.

Finally, operators would have to change their roaming contracts with each of their roaming partners. This will have an effect on almost countries using GSM.

Hence, if the roamed-to network cannot scrutinise 3-digit MNCs , roaming would stop overnight

Fraud Prevention / Management:

Historical searches for IMSIs spanning the transition will have to be split into two reports, one before and one after search. Usage variation alarms for all the numbers that change will effectively start from scratch.

The impact from a Fraud & Security point of view would be the cost of modifying Fraud Management Systems and the length of time it would take to run the additional reports required.

(Further Input is welcome by other GSMA groups on specific issues relevant to their groups!!!!)

The GSM Association (GSMA) has recently been following the developments on the expansion of Mobile Network Codes (MNCs) from 2 to 3.

The GSMA, as the premier global body behind the world’s leading wireless communications standard, protects and enhances the interests of 678 GSM mobile operators from 209 countries and territories with more than 1 billion customers throughout the world today.

The GSMA has concerns related to the allocation of MNCs and its change in some cases from 2 digits to 3 digits and would like governments and regulatory authorities to take these concerns into account when allocating numbers to operators.

European operators have been issued 2-digit MNCs by their regulators for many years, therefore they have built their systems/infrastructure to support 2-digit MNCs.

In the past only North America and a few other countries have used 3-digit MNCs.  These 3-digit MNCs always ended in '0' (zero) and therefore could be treated as 2-digit MNCs.  The '0' (zero) is dropped/ignored and operators are able to uniquely identify their roaming partner based on the first two digits of the MNC.

The GSMA is now aware of countries where multiple 3-digit MNCs have been issued by regulators where the first two digits are exactly the same.  Although according to the specifications this is acceptable it is a problem for many operators whose systems are only set up to accept 2-digit MNCs. 

Enlarging the length of the MNC to accommodate 3-digit MNCs (filename length, field and record length) is a major change to the entire systems such as the rating engine, the TAP engine, the billing system and the data warehouse.

Further to its preliminary analysis, the GSMA shares such concerns and believes a change in MNC from 2 to 3 digits is most likely to have severe implications for almost the entire GSM system (please see Annex). The main consequences from our point of view would be:

Ø       Call back of the released 2-digit SIM card – this could affect all current GSM users (around 500 million in Europe).

Ø       The handset display may not be ready for such a change – this could cause severe confusion with all existing GSM handsets.

Ø       Change of all existing roaming agreements with the need to re-run all the performed tests.

Ø       Enormous efforts in terms of investment and manpower in order to change network elements and billing systems, thereby reducing the innovation power of mobile operators.

Ø       Inability for many operators to roam with the second operator where 3-digit MNCs have been issued in a country with no ability to identify an operator by the first 2 digits.

Therefore we strongly encourage governments and regulators to undertake a cost/benefit analysis when allocating MNCs.  We would suggest allocating either 2-digit MNCs or alternatively 3-digit MNCs where the operator can be uniquely identified by the first 2 digits.

You will find attached an analysis paper expressing the views of the GSMA operators. The paper seeks to outline the technical issues relating to the introduction of 3-digit MNCs and the possible consequences associated to this change.

I hope the attached document will be of interest to you.

Yours sincerely,

Tom Phillips

Government & Regulatory Affairs Officer

GSM Association

For any questions, please feel free to contact Isabelle Mauro, Programme Director, GSM Association: Tel: +44 207 518 0548; Fax: +44 207 518 0531; E-mail: imauro@gsm.org

Annex

Technical Issues Relating to the Introduction of

Three Digit Mobile Network Codes (MNCs).

1              Introduction / Background

According to IMSI structure defined in ITU E.212 an MNC can have two or three digits.

The IMSI structure and format are as shown in Figure 1.

(Figure 1              IMSI Structure)

The MNC is an inner element in the IMSI with a defined length of 15 digits. The whole IMSI is marked on the SIM-card. To this extend, the IMSI must not be mismatched with the subscriber's number which is e.g. in GSM an E.164 number.

Various GSM entities will interpret the extra MNC digit as part of another field (MSIN), which will consequently lead to inconsistencies within the interaction between various parts of the whole GSM System.

The IMSI is used to identify a (roaming) customer, for network internal purposes used in all signalling in the PLMN, in interaction with the Mobile Terminal and for BackOffice applications like charging, billing and accounting.

As the National Regulatory Authorities (NRAs) are responsible for the establishment and publication of conventions for IMSIs (IMSI = MCC + MNC + MSIN), the change of the current MNC allocations (e.g. 03 may become 030 or 003) may lead to severe problems given that the length of the IMSI is fixed and the structure / usage of the MSIN is subject to each individual operator.

It should be noted that for the time being, out of a total of 300 MNCs actually in use, 14 are 3-digit MNCs. Furthermore, there are no assignments for 3-digit MNCs outside the US, where 5 US Operators where assigned such MNCs. In terms of operators this corresponds to 1.7 % of the GSM Operators.

2              Technical implications derived from the introduction of 3-digit MCNs

Below we find some of the technical applications derived from the introduction of 3-digit MCNs. However this paper does not in any case try to be exhaustive and further in depth analysis is required. 

2.1              SIM Cards

The IMSI is an inherent part of all SIM cards. This would hence require a replacement of all existing SIM cards with new ones. Taking into account the number of mobile users and prepaid cards, such exercise is practically not feasible (e.g. in Germany about 35 million of SIM Cards are produced, or submitted to the customers, with a rapidly increasing proportion of prepaid cards). The costs of this procedure are expected to be quite high due to necessary production of new SIM cards, SIM card distribution and logistics, customer service, activation of the new SIM cards, and customer handling. The activation/provisioning part raises questions about the capacity of the IT and networks systems. It would be quite likely that most operators would be forced to build up additional capacity to be able to manage the migration. Some customers would experience problems and would temporarily be unable to use their mobile, which means loss of revenue from the operator's point of view. In addition to this, it is doubtful that SIM card chips, which are already due to the strong demand in short supply, can be produced to serve all carriers in due time.

As a result of this, the co-existence of 2 and 3-digit MNCs can only be the subject of further analysis.

2.2              Handsets

The introduction of a 3-digit MNC will certainly result in a number of compatibility problems between existing mobile equipment and the SIM, and also very likely between the mobile station (MS) and the network. With respect to compatibility problems in the interface between SIM and the software of mobile equipment (ME), two cases can easily be identified:

1)   SIM with a new IMSI structure built up by three digits MNC combined with an ME running old software that isn't prepared for the new IMSI structure. The ME will in this case attempt to read the extra MNC digit as part of another field. This case will be difficult to solve, as there are about 250 Million legacy mobiles in operation throughout Europe.

2)              SIM with an old IMSI structure build up by two digits MNC combined with a ME running new software, expecting the new IMSI structure. Here it is much easier to find a solution, but the problem has to be addressed in order to find some kind of IMSI type identification on the SIM.

In any case a large number of terminals would have to be replaced and very long lead time (longer than the typical life span of a mobile terminal) would have to be allowed.

2.3              Network

The IMSI analysis would need to be redefined. All subscriber records would need to be modified to change the MNC from 0X to 0X0 or 00X. In the case of multiple Home Location Registers (HLRs), as is the case with nearly all operators, the level of planning and coordination would be substantial.

In the case of redundant HLRs, the data would need to be changed on both the live and backup locations.

In addition to this, many of the operators would have to reconfigure their base station subsystem so that it transmits a Location Area Identity (LAI) which contains the new 3-digit MNC.

2.4              Billing & Customer Care Systems

The billing systems of most networks use the IMSI for the generation and gathering of billing information. A change in the MNC would require severe modifications to billing systems and protocols. All effected subscriber records would need to be modified TAP-Files (TAP-Incollect/Outcollect) TAP 2 / TAP 2+/TAP3.

2.5              Roaming

Regarding roaming, the IMSI analysis for all European operators will have to be changed in every MSC. All roaming testing would have to be redone and would be more complex.

Finally, operators would have to change their roaming contracts with each of their roaming partners. This will have an effect on nearly every country using GSM. Hence, if the roamed-to network cannot scrutinise 3-digit MNCs, roaming would stop overnight.

2.6              Fraud Prevention / Management

The IMSI is a data element commonly used by the operator community to detect fraud. To change the format of the IMSI would render most detection and prevention useless thereby exposing networks to increased financial loss.   

Historical searches for IMSIs spanning the transition will have to be split into two reports, one before and one after search. Usage variation alarms for all the numbers that change will effectively start from scratch. Similarly, any IMSIs that had previously been hot-listed for the purposes of fraud monitoring would need to be replaced. 

One impact, from a fraud and security point of view, would be the cost of modifying fraud management systems that are currently used by home networks to monitor for fraudulent calling patterns based on individual IMSIs. It also likely that the length of time it would take to run the additional reports required would increase.

GSM operators currently have mechanisms in place that allow for the exchange of IMSIs, and other data, which may identify fraud. Such exchanges can be transacted electronically through the use of near real time data exchange systems across the SS7 signalling network. Such systems would need to be upgraded to accommodate changed MNCs.