Data adapter for a radiotelephone

A data adapter (2) for a mobile telephone (1) of the type intended to have a subscriber identity module (SIM) inserted therein and capable of supporting a short message service (SMS). The adapter includes means for coupling to the telephone so that data can be transferred therebetween. The coupling means includes a connector configured as a standard SIM, i.e. designed to fit in the SIM interface (3) of the telephone (1). The adapter itself includes means (6,7) for receiving a SIM such that data can be read from or written to the SIM. Means are included in the adapter for converting received data into SMS format thereby enabling the mobile telephone to be used for receiving/transmitting data messages other than normal SMS messages. A data input/output (8) may be provided on the adapter for connection to an external data terminal, e.g. a PC.

FIELD OF THE INVENTION 
The present invention relates to a data adapter for coupling to a 
radiotelephone particularly, but not exclusively, a cellular telephone, 
the telephone having means for removably receiving a subscriber Identity 
Module (SIM) whereby information may be transferred between the telephone 
and a SIM present in the receiving means. 
BACKGROUND OF THE INVENTION 
As used in the present context, the term "SIM" includes a data card, such 
as a smart card (IC card or magnetic card), and other forms of package 
enclosing or carrying a memory device. In addition to subscriber identity 
information, such as the subscriber telephone number, and personal 
identification number (PIN), the smart card may store for example, call 
charge information (i.e. a charge meter), a telephone number index, or 
false PIN entries. As memory capacity expands in smaller chip sizes, more 
application can be implemented on one smart card. Accordingly, it is 
envisaged that in future multipurpose smart cards will cover an even wider 
range of applications than personal identification and data storage 
services. 
Indeed, in modern telecommunications systems, the applications for smart 
cards is expanding. One such application in this field is the SIM proposed 
for the pan-European digital cellular radio telephone system known as GSM 
(Groupe Speciale Mobile). For more information about the SIM proposed for 
GSM, reference is invited to the European Telecommunications Standards 
Institute (ETSI) Recommendations GSM 11.11 which describes the technical 
SIM specifications and Recommendation GSM 02.17 for the functional 
characteristics of the SIM. 
There are currently two different mechanical standards proposed for the GSM 
SIM card and it is probable that a third will evolve. The functionality of 
the SIM is the same for all sizes, it is essentially that the physical 
dimensions are different. At present the two standards are (a) a credit 
card size SIM, and (b) a plug-in SIM about 20 mm.times.25 mm. The proposed 
third standard is likely to be a mid-sized SIM about half the size of a 
regular credit card. The rationale behind the different sizes is that the 
credit card size is perceived as a convenient size for the user from a 
practical standpoint. However, the credit card size is relatively large, 
and smaller card sizes are needed as miniaturization continues to drive 
down the overall size of the terminal (i.e. the radio telephone unit 
itself). The plug-in SIM is intended to be semi-permanently installed in 
the cellular telephone. 
The implementation of data services specified by GSM has not generally been 
considered necessary by GSM operators in the initial stage of the service. 
In this situation those customers who wish to obtain some kind of data 
services must rely upon other, simpler services provided by GSM. 
SUMMARY OF THE INVENTION 
According to the present invention there is provided a data adapter for a 
radiotelephone having means for removably receiving a Subscriber Identity 
Module (SIM), wherein information may be transferred between the telephone 
and a SIM present in the receiving means, the adapter comprising, means 
for coupling the adapter to the telephone whereby data may be transferred 
between the telephone and the adapter, the coupling means including a 
connector adapted to fit the SIM receiving means of the telephone, means 
for removably receiving a SIM card enabling data to be transferred between 
a SIM present therein and the coupling means, and means for processing 
data transferred to the adapter. 
In principle, the data adapter could be connected to various parts of a 
mobile telephone (ME=Mobile Equipment). However, connecting the data 
adapter to the SIM-interface in accordance with the invention has the 
advantage that the data adapter can used with any type approved mobile 
telephone which supports an SMS-service (Short Message Service).

DETAILED DESCRIPTION OF THE INVENTION 
As shown in FIG. 1, the data adapter 2 is coupled via a cable 5 to the SIM 
interface 3 of a mobile telephone 1 using a connector 4. More 
specifically, the SIM interface 3 comprises a SIM holder into which a SIM 
can be removably inserted. When a SIM is inserted into the holder 
information stored therein can be transferred between the mobile telephone 
processing circuitry and the SIM in known manner. The connector 4 attached 
to the cable 5 has the shape and configuration of a standard SIM. For 
example, in the case of a GSM telephone the connector 4 may have the same 
shape as a standard credit card sized SIM or as a smaller "plug-in" type 
SIM, as discussed above. Hence, the data adapter 2 can be coupled directly 
into the SIM interface without the telephone needing to have any other 
data output facility. SIM-ME interface 3 is a standard sized interface so 
the traffic in all type-approved mobile telephones 1 must comply with the 
same protocol. 
The data adapter to also has the facility for receiving a SIM and for 
reading information stored thereon. In the present case two SIM interfaces 
6,7 are included in the data adapter to, wherein the SIM interface 6 is 
for receiving a semi-permanent plug-in type SIM as specified in GSM, and 
the SIM interface 7 is for receiving a removable credit card type SIM, 
also as specified in GSM. 
The data adapter 2 also has a data connector (input/output) 8 for an 
external data terminal, such as a personal computer (PC) as discussed in 
more detail below. 
Data received by the adapter 2 at input/output connector 8 from an external 
source is converted into a short message format within the adapter and 
then buffered, i.e. stored temporarily in a memory in the adapter. 
Similarly, short messages received by the adapter from the mobile 
telephone 1 may be processed within the adapter and then buffered for 
onward transfer as data to an external data terminal coupled to the 
input/output 8. On the other hand, short messages may be transferred 
directly between the SIM interface 3 of the telephone 1 and a SIM present 
in the adapter without the data being processed in the adapter 2, and 
without intermediate buffering. 
In order to distinguish between a `normal` short message (SMS) and a data 
message a special protocol may be adopted. For example, a data message may 
include a preamble including certain characters indicating that the 
following information relates to a data message, those certain characters 
being characters which would not ordinarily be used in a normal SMS. 
An example of a `normal` SMS could be the following message entered on the 
keyboard of the mobile telephone 1; 
PLANE 4 HOURS LATE. PLEASE DELAY MEETING UNTIL THEN. MATTI 
An example of a data message could be any data from a PC such as a binary 
file generated by a utility programme. A data adapter in accordance with 
the present invention may be used in conjunction with a radiotelephone to 
transfer the file from the PC, for example to a central computer or vice 
versa. The data would be encoded by the adapter according to the allowed 
SMS characters supported by the system. It will be evident to a person 
skilled in the art that the encoding/decoding may be performed in many 
different ways, but it is noted here that a data file may not fit into one 
pre-defined SMS message, in which case it would have to be split over 
several messages. 
Data adapter 2 is bidirectional but it can also be used unidirectionally in 
mobile telephones 1 which support only the use of either Mobile 
Originating SMS services or Mobile Terminating SMS services. 
Alternatively, the data adapter can be realized in such a way that it is 
able to either only to transmit or only receive data messages. 
When the connector 4 is coupled to the SIM interface 3 of the mobile 
telephone a SIM module can no longer be connected directly to the SIM-ME 
interface 3. Thus a separate coupling for the SIM module has to be 
implemented in the data adapter 2 in order that the mobile telephone 1 and 
data adapter 2 combination can function as a mobile station in the normal 
way when the presence of a SIM is required. 
As mentioned above, the adapter 2 has two SIM interfaces 6,7 for accepting 
two different SIM types, the smaller plug-in type and the larger credit 
card size, as specified in GSM. 
A 7-bit character code is used as the character combination of the SMS 
services. A transparent bit transfer is achieved by, for instance, coding 
the bits in such a way that one byte is represented by two characters in 
hexadecimal code. On the other hand, depending on the application, more 
efficient coding methods can be used, being selected in some other way, 
especially if the transfer does not have to be transparent. 
External data interface 8 of data adapter 2 may be, for instance, a TTL 
level output comprising a provision to transfer an 8-bit byte in a 
parallel form. Alternatively, the external data interface 8 may be, for 
instance, a serial interface in accordance with the RS232 standard with 
adjustable data rates. 
The air interface of mobile telephone 1 is also standardized. If it is 
required to transmit data messages, mobile telephone 1 that adheres to the 
standard must be able to transmit Short Messages stored in the SIM module. 
Correspondingly, if one wants to receive data messages, mobile telephone 1 
that adheres to the standard must be able to receive Short Messages that 
can be stored in the SIM module. Mechanical limitations and the length of 
the cable must not cause problems. 
The realization of the SMS is an optional function so it is not necessarily 
included in all mobile telephones 1. Nevertheless, any type approved 
mobile telephone 1 can be coupled to data adapter 2 in accordance with the 
invention, thus providing a data service facility. 
In view of the foregoing description it will be evident to a person skilled 
in the art that various modifications may be made within the scope of the 
invention. In particular the invention is not restricted to the GSM 
system, but is equally applicable in systems in which the telephone 
operates with a removable SIM.