Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Patent
1995-09-05
1997-08-12
Cumming, William
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
379357, 455551, 455558, H04Q 738
Patent
active
056573731
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a digital mobile communication system comprising a switching centre, a subscriber register connected thereto, mobile terminals, such as mobile telephones, and subscriber-linked subscriber's cards, such as smart cards, insertable in the mobile terminals.
DESCRIPTION OF THE PRIOR ART
With mobile communication systems, it is always possible to reach the subscribers within the coverage area of the system, regardless of where they are, which is a considerable advantage. It may also be advantageous, e.g. when travelling, to have a telephone ready to hand at all times and thus not have to depend on pay phones and small change when making important telephone calls.
In prior-art mobile communication systems, the subscriber's number has always been linked to the mobile telephone itself, so that a subscriber possessing two mobile telephones, e.g. one mounted in a vehicle and one to be carried along, has had at that two different subscriber's numbers and, consequently, two different subscriptions. However, this inconvenience of the subscriber having different subscriber's numbers and different subscriptions when possessing several mobile telephones was initially not inherent in a new digital mobile communication system called GSM (Global System for Mobile Communications).
This system, which has a large coverage area as a result of far-reaching international cooperation, is distinguished by communication taking place by means of digital signal transmission and by the subscription being linked to a subscriber's card that can be inserted by the subscriber in different mobile terminals in order to activate these. A mobile terminal holding such a subscriber's card can be reached at the subscriber's number linked to the subscriber's card, and outgoing traffic from this mobile terminal, such as telephone calls, telefax transmissions and data communication, is as a rule debited the subscription linked to the subscriber's card, i.e. the mobile terminal as such is of minor importance in this system and the subscription is embodied by the subscriber's card.
The subscriber's card is a so-called smart card which in GSM contexts is referred to as SIM (Suscriber Identity Module) and contains at least one microchip which holds information on the subscription and which, when the SIM card is inserted in a mobile terminal, is connected thereto.
The original SIM card had the size of an ordinary credit card and was intended to be insertable in any GSM mobile terminal. However, the "credit-card" size soon proved to be inconvenient in small pocket phones, and a smaller "stamp-size" SIM card, containing the same type of microchip and thus compatible with the large SIM card, was introduced as a complement to the large card. Generally, the small SIM card fits all existing mobile terminals but is not, owing to its small size, as easy to handle as the large card and therefore is best suited to be more or less permanently installed in a mobile terminal.
When subscribing to GSM, the customer has to choose between a large SIM card, which is easy to handle and store owing to its "credit-card" size but which is too large for small pocket phones, and a small SIM card, which certainly fits into small pocket phones but which is difficult to handle and easily lost owing to its small size.
The only possibility up to now has been to recommend the customer to have two GSM subscriptions, one for each card. This solution not only has the inconvenience of entailing a double set of bills, giving both the GSM net-work operator and the subscriber extra trouble, but also involves uncertainty as to the subscriber's number at which the subscriber can be reached at the moment, two subscriptions requiring by necessity two different subscriber's numbers.
OBJECT OF THE INVENTION
The object of this invention is to remedy the above inconveniences.
SUMMARY OF THE INVENTION
According to the invention, this object is achieved by a digital mobile communication system of the type mentioned by way of introduction, which
Hermansson Jan
Jacobsson Anders
Karlsson Bo
Leuhusan Goran
Mansson Christer
Cumming William
Europolitan AB
Wyche Myron
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