GB2396777A

GB2396777A - Using alpha addresses in place of numeric addresses in gsm networks

Info

Publication number: GB2396777A
Application number: GB0229775A
Authority: GB
Inventors: Jeffrey Wilson; Robert S Harding
Original assignee: Telsis Holdings Ltd
Current assignee: Telsis Holdings Ltd
Priority date: 2002-12-23
Filing date: 2002-12-23
Publication date: 2004-06-30
Also published as: GB0229775D0

Abstract

A telephone communication, such as a text message transmission, has its alphanumeric address compressed, for example by a compression means in the telephone handset. The communication receiving means, such as a telecommunications services apparatus including an SMS router 2, includes a decompression means for decompressing the compressed alphanumeric address. Each telephone communication includes an indication of whether or not compression has been applied to the alphanumeric address, and the decompression means is only operative if the indication is that the received alphanumeric address has been compressed. For a reply communication, the telecommunications services apparatus may compress the alphanumeric address, and the telephone handset may decompress the received compressed alphanumeric address.

Description

TELECOMMUNICATIONS SERVICES APPARATUS

This invention relates to a telecommunications services apparatus for use with a mobile telephone system. such as a mobile telephone system.

5 Users of mobile telephones can have access to a wide variety of services. including network based services such as voicemail and information and entertainment services provided by the network and by third parties. These facilities may be accessible via voice calls. text messaging. multimedia messaging and the like. From hereon. the term text messaging is taken to included GSM Short Message Services (SMS). Enhanced 10 Messaging Service (EMS). Multimedia Messaging Service (MMS) and other similar techniques. Normally. users make voice calls by dialling a string of digits representative of a telephone number of the desired service. Most people have difficulty memorising more 15 than a few telephone numbers and therefore use one or more of various forms of directory to provide a translation from a meaningful alphanumeric name to a digit string. Similarly for text messaging. the messages are normally addresses by means of a 20 numeric string. which may be a short code or a full telephone number. representative of the desired service. Even where a short number is available it is still difficult for users to remember more than a few numbers without the aid of a directory.

Most mobile telephones have a built-in telephone directory or phone book. so that 25 frequently used names can be selected from the phone book and dialled or messaged directly without the user having to re-enter the number. However phone book size is typically limited to a few hundred numbers or less. and in any case most users only enter the names of frequently contacted people or services in their phone book. and less frequently used numbers will still not be available using this method. When a 30 service is required. obtaining the number from other sources may be difficult.

especially if the user is away from the home or office.

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e À..e e In another branch of communications. the same problem of using long digit strings to identify Internet web sites has been very effectively overcome by allowing users to enter alphanumeric addresses (domain names) of the form www.companyname.com.

5 Such addresses are translated within the Internet network to the required numeric strings. Furthermore. Internet search engines are available to assist in identifying the correct alphanumeric domain name if the user does not know it.

For the GSM system of mobile telecommunications. the specifications permit the use

10 of alphanumeric addresses in place of numeric addresses. For example. a text message may be sent to the address TAXI. and provided that the network has been configured to deal with this type of message format. it is possible for the user to be provided with an appropriate service to allow him to arrange a taxi. In practice very few networks are set up to deal with this situation but the use of alpha addressing is growing. SMS Hosts 15 are commonly capable of sending Host Originated messages that have an Alphanumeric CLI as the originating address. and this technology may be used to promote company branding.

It is envisaged that the ease of use of alpha addressing will eventually drive its usage 90 to the point where it becomes commonplace and fully supported in most networks and handsets. By this time some limitations of the way in which alphanumeric addressing in GSM has been specified will have become apparent. GSM allows the originating or destination address of a voice call or text message to be encoded either as a normal telephone number. or as an I l-character ASCII string from a defined 7- bit alphabet.

_5 This is clearly a limitation. since 11 characters restricts the usage of alphanumeric addressing to names of 11 characters of less. Though useful. this does not permit straightforward use of names such as Marks and Spencer or bus timetable as network addresses for accessing a service.

30 The network signalling transport standards will not change to support longer addresses. since the installed base is equipment is so vast that upgrade to support longer addresses per se would not be viable. However the present invention

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circumvents this problem for text messaging and allows users to send messages to longer alphanumeric addresses over existing networks.

The techniques of the invention may also be applied to voice calls and other types of 5 mobile communication by implementation of the invention at appropriate points in the signalling network. The invention is now further described in the context of GSM text messaging. Similar techniques may be applied to other forms of text messaging.

GSM supports several different types of address that may be carried in the originating 10 and destination address fields of a text message. One of these is an alphanumeric

address format, that allows the sender to enter up to 11 alphanumeric characters each coded as a 7-bit value using the GSM character set. In GSM an alphanumeric originating address is supported for Mobile Terminated messages, and an alphanumeric destination address is supported for both Mobile Terminated (MT) and 15 Mobile Originated (MO) messages.

The GSM encoding normally uses 1 I x 7 = 77 bits to encode characters. however the transport has 80 bits available. The invention allows these 80 bits to be used to encode a larger number of characters than 11. so that longer alphanumeric addresses may be 20 specified by the sender. This may be achieved in a variety of ways, and some of these methods are outlined in this document. The intention is to encode as many characters as possible, using a restricted character or token set. while remaining within the available 80 bits. The maximum number of characters encoded may be fixed or variable, and may depend on content in some schemes.

In principle the compression may be achieved by an algorithmic encoding scheme. for example using look-up tables per character or group of characters, may use run length coding for example Huffman coding. or may use a dictionary technique. These techniques may also be combined in various ways.

One example of a dictionary technique could store a large vocabulary of words, strings and sub-strings that commonly occur in a language. Different dictionaries may be used

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for different languages. possibly selected automatically by the mobile country code of the user s IMSI. or selected manually. In encoding the alphanumeric input. the encoder would progressively search along the input string trying to find the longest match to a dictionary entry. When found. these characters in the input would be represented by the dictionary index in the output. and the encoder would move along to the next group of characters. Depending on the scope of the dictionary. this scheme can be extremely efficient. The dictionary is also arranged to carry examples of every allowable single character. so that in extremis it is still possible to encode any message.

10 The dictionary technique may be combined with other techniques by means of a control character (a bit pattern in the output) that indicates the desired decoding mode for the next part of the output. The encoder is then free to choose the most efficient encoding strategy for any input by using the dictionary where possible. and switching to an alternative algorithm where this is sufficiently better.

Compression may be used in the user to network direction or the network to user direction. The handset may contain and encoder or decoder respectively. with the corresponding function implemented in the network. for example using SMS Routers.

90 In overview. in the user to network direction the invention could be used in the following way. The processing involves stages: compression and de-compression.

The compression happens before the message is sent over the GSM transport. for example in the handset or an application running on the handset. Decompression happens before delivery to the recipient. Typically the decompression stage may 95 involve translating the address into a form suitable for the next stage of transmission.

which could be by email. fax. SMPP. or text message with a numeric address or a mapped alphanumeric address (limited to 11 characters.) Compression would be particularly useful for allowing longer email addresses to be entered into the GSM alphanumeric address field.

In a preferred embodiment. SMS Routers in a GSM network are adapted to determine messages that are encoded with an alphanumeric compressed address. and to de

:.e À e: es::.e:: ae :...... eee s compress and/or interpret the address according to pre-defined algorithm(s).

Subsequently the message may be onward transmitted. or responded to. according to the de-compression or interpretation. Other embodiments are possible. for example an SMSC may be used to perform the de-compression.

One envisaged use of the invention allows alphanumeric company names or Brands that may exceed 11 characters to be entered by users as addresses for text messages or to initiate voice calls. Another use allows users to specify the name of an information service by an alphanumeric. such as bus timetable. A further use allows the 10 originating address of a message sent to a user to be displayed as an alphanumeric that may exceed 11 characters. which is not possible today. In this case the handset or an application running on it would de-compress the address if necessary and display the uncompressed address to the recipient.

15 Examination of a large number of common Brand names in the UK revealed that the vast majority can be represented using 16 characters or less. and that selective capitalization is used extensively by Brand names.

It is evident from the Brand-name list examined that the majority of brands are 90 normally written in Title case: e.g. Land Rover. Old El Paso. Pall Mall Relatively few are all upper case: e.g. B&Q. UEFA. AMD Many are mixed case: 95 e.g. cKone. iMAC. BSkyB. PC World A few are lower case: e.g. brother.

However we also expect alpha addressing to be used for common nouns like: e.g. flowers. countries. tides etc. that may be used as alphanumeric service 30 addresses. and so we expect that lower case will be a common usage.

It was also noted that brand names that exceeded 11 characters rarely contained digits.

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. À. .. . À À.. À À..DTD: It would be advantageous if presentation to the user/ entry by the user could support any desired capitalization in the compression scheme. It was evident that efficient encoding of capitalization would be a key element of the proposed alphanumeric 5 compression scheme. More advanced terminals may also support font. size. or other characteristics of text to be modified.

A Mobile user composes a text message and specifies an alphanumeric address that is longer than 11 characters. Processing in the handset encodes this address into the 10 available address field and sets a signalling parameter to indicate that the address is

compressed. The message is sent via MSC ( 1). The message arrives at an SMS Router (2) which spots the compressed address mode and provides decompression. The de-

compressed address may be used as an address for an alternative transport (6) such as email. or may be mapped to a destination or service. or translated to a numeric address 15 in this or another network. A database (3) may be used in the decompression. and the database may contain a dictionary or other lookup function to assist with the decompression. The message is then forwarded to its destination. which may be by normal means (4.5) or by an alternative transport.

20 The proposed methods in this invention allow characters to be encoded in character groups (e.g. single characters. pairs. triplets etc.) using groups of bits taken from the 80 available. A restricted character set is also proposed. There is a trade-off between the character set size chosen and the number of bits required to encode each character group. 75 Referring to the list of common UK Brands. the following character set was derived as appropriate for encoding the vast majority of Brand names and nouns:

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26 letters space - hyphen 5 ' apostrophe 8: ampersand dot Total 3 1 10 Capitalisation may be handled in various ways. but the following algorithm is quite efficient: Capitalisation may be handled by a combination of a format field ( I bit) plus a special

character for coping with exceptions.

I Format Bit Meaning I O Title Case Each distinct word (following space. dot.

ampersand or hyphen) has its first letter capitalised I Lower Case l l The entire string is lower case by default This basic format is then modified by the special character. indicated here as and called Change Case. Change case inverts the case of all following letters up to the next end-of-word. unless it occurs at the start of a word in which case it changes the 20 meaning of format (lower means UPPER. Title means lower) for the remainder of the string. Word boundaries are determined by defining a subset of characters as delimiters. e.g. space. hyphen etc. Including the o character brings the character set so far defined to 32.

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.. . a. e.. À Note that the following examples are all 11 characters or less and so could be transmitted uncompressed by normal means. They are used here only to clearly demonstrate the capitalization algorithm...DTD: 5 Examples of encoding and the use of String to encode Format Encoding l Woolworths I Title woolworths l chemistry lower chemistry Land Rover Title land rover iMAC lower itmac AC-Delco Title aSc-delco I TETRA l lower ttetra TOP SHOP lower Stop shop Coffee-mate I Title co ffee- tmate cKone lower cktone BSkyB Title btskyb Fortunately the more idiosyncratic the case styling! the shorter the word is likely to be.

Another preferred option is to abandon the format specifier altogether and leave the 10 default as Title case. The S Change Case character can still be used to derive any arbitrary case combinations. but on average an extra will be needed for strings that are not in Title case.

at the start of a word redefines format to lower for the remainder of the string. S 15 anywhere else inverts the case up to the next end-of-word. Examples then change to:

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String to encode Encoding chemistry Schemistry Land Rover land rover iMAC tiSmac AC-Delco atc-delco TETRA ttetra TOP SHOP ttop sthop Coffee- mate coffee-$mate cKone Schick tone BSkyB btskyb The preferred character set now comprises 32 characters: 5 26 letters space - hyphen apostrophe & ampersand 10. dot S change case Total 32 Conveniently 32 characters can be encoded in exactly 5 bits with no wastage. The 80 15 available bits allow for up to 16 characters to be encoded in this way.

c ÀÀ À À cc c À À À c Àc. À cc c À c c c c À c arc ee- ace. ace For example Marks & Spencer can now be encoded as String to encode Encoding Marks & Spencer ma r ks & Spencer It is necessary for the SMS Router or other decompression apparatus to determine whether the received address is compressed or not. This may be achieved in various 5 ways. for example: À Using one of the bits in the address field as an indicator. This reduces the

number of bits available for character encoding À Using a flag in the body of the text message. This reduces the number of characters for the message available to the sender.

10 À Using an indicator in the signalling for example a different type of address.

possibly even a reserved value. This is the preferred solution.

Alternative coding schemes are possible. For example using 5.5 bits. 45 characters can be encoded i.e. using 11 bits. two characters from a character set of size 45 may be 15 encoded. This works as follows.

2" is 2048 whereas 45 is only 2025. Therefore every permutation of 2 characters from a 45-character set may be encoded in 2025 unique values, which may be represented by 11 bits. Of the possible 2048 bit patterns representable by 11 bits. only 20 2025 of them will be used for this purpose. The remaining 23 patterns may be used for an extension to the algorithm described later.

Therefore using 77 of the available 80 bits. 7 character-pairs may be encoded from a 45-character set. This allows 14 characters to be encoded in total. The remaining 3 25 bits. that are not normally used by GSM. may be used to contain a format indicator for capitalization as described earlier. as a compression indicator as described earlier or for other purposes.

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Other combinations of bit allocations and character set sizes are possible. An extreme case is where a table of size 28 is used to represent all possible combinations of N characters from a character set of size M. Unfortunately this approach. although highly flexible in practice. represents an impractical solution since the amount of memory 5 required is intractable. In practice. single character. pair or triplet encoding offer the most attractive solutions. though other schemes are possible.

As alluded to earlier. it is possible to make use of the 23 patterns that are not used for character pairs in the previous example with the character set of size 45.

10 If we encode characters in pairs using a 45 by 45 array this uses 2025 discrete values.

For example the array might be encoded as follows: 0 aa I ab 7 ac 3 ad .. 2023 _ (A

yielding all possible combinations of pairs of the 45 characters. and where the remaining 23 indexes are reserved.

The first thing to note is that if you use one of these reserved values this takes the place of encoding TWO characters.

Several schemes give a benefit. and these schemes can be used independently or 20 together.

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..........DTD: 1. Define groups of useful characters such as-

they limited Itd. &8,C Old and8,8 company each of which can be encoded as a character pair' using the 23 reserved values. These can be usefully encoded whenever they occur on a pair boundary. yielding longer source strings that can be encoded in the 80 available bits. 2. Drop the number of characters in the set to 44. and expand the reserved set from 23 up to 1 12. Define groups of useful characters such as-

are eau Ing ent 10 according to common usage in English. Common run lengths of 3 and 4 characters could be derived automatically from text processing. These substrings could occur either on or off a character pair boundary. When on a boundary. the encoder can simply use the reserved encoding. yielding a benefit for substrings of 3 or more characters.

15 When off a boundary. the encoder can either ignore the special encoding and encode normally. or we could include single characters in the reserved set. This would then only give a benefit for substrings of 4 or more characters in the reserved set.

20 For example to encode BARE. where both B' and ARE' are present in the reserved set still takes 22 bits whether encoded as BA' REP or as B' ARE'.

So there is no benefit for the three letter group.

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However SHARE can be encoded as SH ARE in 22 bits. giving a benefit of encoding 5 characters instead of 4. because the 3 letter group fell on a pair-

encoding boundary.

5 3. Gain an extra character in the character set by removing q and replacing it with a new character. extending the character set by 1. Restore the q by encoding q.

qu. and qS in the reserved set. This works because anything other than a u following a q is very rare.

10 Unfortunately this scheme suffers when the q is the second character of a pair to be encoded as the first character would have to be encoded singly. so the reserved set needs to include each of the 45 characters paired with a following q (aq. bq etc). In the very rare case where q appears as the first character of a pair without a following u. the scheme is less efficient. but in the vast majority of cases (i.e. qu or 15 ?q) these characters can be encoded with the same number of bits as before. but an extra character in the character set has been gained.

Other options for using compression include the following: À Use a dictionary technique. For example 100,000 words. letter combinations 20 and phrases can be encoded in 17 bits. forming a powerful way to encode long words in few bits. When combined with other techniques and a character to signal transition between encoding modes mid-string. a very flexible and powerful encoding scheme can be created. at the expense of additional complexity. 25 À Overflow into the text body. This allows alphanumeric addresses of arbitrary length to be encoded by using both the address field and a portion of the

message body.

À Use the message body only. with compression.

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r e. 4 À Use the message body only. and send the message to a short code or directory service number. This requires no handset changes but isn t really compression.

A compression scheme has been described that allows a sender to enter an 5 alphanumeric destination address that may be longer that 11 characters. and for this to be encoded by the handset and transmitted. The message is intercepted in the network.

and the address is translated to its full form.

Claims

1. A method of transmitting a telephone communication from a communication sending means to a communication receiving means, the telephone 5 communication being capable of including an alphanumeric address of up to a maximum number of alphanumeric characters, the method comprising: providing the communication sending means with a compression means for compressing a received alphanumeric address; providing the communication receiving means with a decompression means for 10 decompressing a compressed alphanumeric address; sending with each telephone communication an indication of whether or not the respective alphanumeric address has been compressed; receiving a telephone communication at the communication receiving means so as to determine from the respective compression indication whether or not the 15 respective alphanumeric address has been compressed; and in the event of determination of compression, decompressing the respective alphanumeric address.

2. A method according to claim 1, wherein the compression means 20 compresses a received alphanumeric address with more than the maximum number of characters. 3. A method according to claim 1 or claim 2, wherein the compression means and the decompression means are operable according to an algorithmic 25 encoding scheme.

4. A method according to claim 3, wherein the compression means and the decompression means utilise respective look-up tables per character or group of characters.

/ 5. A method according to any one of the preceding claims, wherein the compression means and the decompression means utilise run length coding/decoding.

6. A method according to claim 5, wherein the run length coding/decoding 5 is Huffman coding/decoding.

7. A method according to any one of the preceding claims, wherein the compression means and the decompression means utilise a dictionary technique storing a vocabulary of words and strings each representable by a reduced number of 10 characters.

8. A method according to claim 7, wherein the compression means progressively searches along the received address to find the longest match to a word or string of the stored vocabulary.

9. A method according to any one of the preceding claims, wherein the compression means and the decompression means may utilise a plurality of compression/decompression techniques, the compression indication including a control character indicative of the compression technique that has been used in the 20 respective communication.

10. A method according to claim 9, wherein a single telephone communication may involve more than one compression technique, the compression indication including a control character indicating the appropriate decoding mode for 25 the subsequent part of the alphanumeric address.

11. A method according to any one of the preceding claims, wherein the indication of compression is included in the address field of the telephone

communication.

12. A method according to any one of the preceding claims, wherein the telephone communication is a text message transmission, and the indication of compression is included in the body of the text message.

5 13. A method according to any one of the preceding claims, wherein the indication of compression is included in the signalling of the telephone communication. 14. A method according to claim 13, wherein a telephone communication 10 with compression is sent to a different address than one without compression.

15. A method according to any one of claims 1 to 14, wherein the communication sending means is a telephone terminal and the communication receiving means is a telecommunications services apparatus.

16. A method according to any one of claims 1 to 14, wherein the communication sending means is a telecommunications services apparatus and the communication receiving means is a telephone terminal.

20 17. A telecommunications system for compressing/decompressing an alphanumeric address in a telephone communication which is capable of including an alphanumeric address having up to a maximum number of alphanumeric characters, the telephone communication being sent between a telephone terminal and a telecommunications services apparatus, the system being operable according to a 25 method as set out in claim 15 or claim 16.

18. In a telecommunications system, a telephone terminal as set out in claim 17.

30 19. In a telecommunications system, a telecommunications services apparatus as set out in claim 17.

20. A method of transmitting a telephone communication, the method being substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.

5 21. A telecommunications system substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.