FR2790163A1 - Radio alphanumeric transmission system having characters coding value coded and interspersed digital code switching word and block identification code. - Google Patents

Abstract

The alphanumeric transmission method produces two sets of 2c alphanumeric characters where c is the number of bits coded by coding values (VC) defining a group for message. A switching code digital word (DC) is set in the block of digital words, and each block has an identification code (I), so that the corresponding coding can be determined.

Description

Method for transmitting alphanumeric messages over a network of

  paging receivers, and corresponding receiver. The invention relates to paging and more particularly the transmission of alphanumeric messages under

compressed form.

  The invention is advantageously but not limited to paging networks operating according to the RDS standard (Radio Data System) or the MBS standard (Swedish Telecommunication Administration, Specification 76-1650-ZE (1976)),

well known to those skilled in the art.

  Among the paging networks, some, such as those operating under the MBS or RDS standards, use, in terms of data formatting, bit packets (hereinafter called data blocks) which consist of a data field properly say

  followed by a detection field and error corrections.

  An alphanumeric message in particular, consists of several blocks of data broadcast sequentially and which contain in a predefined order the address of the receiver for which the message is intended, then the message itself. The blocks containing the address and the message are interspersed with identification and synchronization blocks, also called "system blocks", so as to allow the receivers to check their good time synchronization on the carrier of the network in question. These system blocks are conventional and are

  described in the paging standards used.

  For the coding of the message proper, the blocks containing the characters of the alphanumeric message contain for example 16 bits making it possible to code 2 characters on 8 bits each. It is usual in radio transmissions for one of the transmitted blocks to miss on reception on the receiver in question. However, in this case, a lost block only results in the loss of the two characters it contains and allows,

  in most cases, to interpret the message anyway.

  However, to reduce the number of blocks necessary for the transmission of an alphanumeric message, one solution consists in using conventional compression techniques, in particular those used in computer science. Such methods, which are both very diverse and more or less effective, on the other hand have a major drawback, namely the propagation of errors. Indeed, if on reception, one of the blocks is missing, the following blocks can no longer be decoded. We speak then

propagation of errors.

  The invention aims to propose a transmission of alphanumeric messages allowing a compression rate of up to

  33% without presenting the problem of propagation of errors.

  The invention therefore provides a method of transmitting alphanumeric messages over a network of paging receivers within which the messages are transmitted over a

  carrier within successive blocks of data.

  According to a general characteristic of the invention, at least two different sets of at most 2c alphanumeric characters are developed each, all these characters being coded by coding values on c bits and together defining a group of at least 2 times 2c alphanumeric characters that can be used in a message. Thus, by way of example, coding values coded on 5 bits make it possible to define at most 32 characters per set. A predetermined switching data item also coded on c bits and representative of a change in the corresponding character set is also produced. to the coding values. The successive blocks of data are inserted the coding values of different characters of the message interspersed as many times as necessary of said coded switching data. Is inserted into each data block, and preferably at the beginning of each data block, an identification data item making it possible to identify the set of characters corresponding to the coding values inserted in said block after said identification data item and up to to the possible presence in

  said block of said switching data.

  Thus, by way of example, the invention allows the possible transmission of more than 60 characters, using values coded on 5 bits as well as an identification datum and a switching datum. In fact, the 5-bit coding values make it possible to define two 32-character games, and the identification and switching data make it possible to define which game is active in the current data block. More precisely, the logical value of the bit forming the identification data, in the case where the number of character sets developed is equal to 2, makes it possible to identify the character set corresponding to the coding values inserted in the block after this identification bit and up to the possible presence in the block of the switching data. When this switching data is detected, the coding values located after this switching data will be decoded according to the other

character set.

  The invention is therefore remarkable in that it makes it possible to use a reduced number of bits to transmit a relatively large number of characters. Furthermore, the insertion of the identification data in each block not only makes it possible to identify the character set to be used for the values following this identification data, but also allows, in the case where one of the blocks transmitted is not received, not to propagate an error in the decoding for the next block, in particular in the case where the block which was not received contained the switching data which indicated to change the set of

characters.

  In a network operating according to the MBS standard, the messages are transmitted within successive groups of data blocks, each block being made up of an identical number of bits. Furthermore, the first block of each group contains a first fragment containing hexadecimal identifier data, typically greater than or equal to B, coded on 4 bits and representing at least part of an identifier of said network,

  for example B5, transmitted at most all the b blocks (b = 5 for example).

  In a variant of the invention particularly intended for use on an MBS network, the coded character sets and the coded identification data are developed so that the first 4 bits of each data block containing the bits of the identification data and at least some of the bits of an encoding value corresponding to a character, are different from the 4 bits of the hexadecimal identifier data. This avoids disturbing the good synchronization of

MBS receivers.

  The invention also relates to a paging receiver intended to operate on a paging network within which alphanumeric messages are transmitted on a carrier within successive blocks of data. The receiver comprising means for receiving said carrier, processing means capable of processing the different blocks received, and means for displaying the

  messages contained in the blocks received.

  According to a general characteristic of the invention, the receiver comprises a memory storing at least two different games of at most 2c alphanumeric characters each, all these characters being coded by coding values on c bits and together defining a group of at least 2 times 2c alphanumeric characters capable of being used in a message, as well as a predetermined switching data coded on c bits and representative of a change in the character set corresponding to the coding values. Furthermore, the processing means are capable of - detecting the value of an identification datum inserted in, and preferably at the start of, each data block and making it possible to identify the set of characters corresponding to the coding values inserted in said block after said identification data and until the possible presence in said block, of said switching data, so as to decode the decoding values from the corresponding character set, and - to detect at least one presence possible switching data in the block and to change the character set as a function of the value of said switching data, for decoding the values

  coding according to each switching data.

  In the case of an MBS receiver, the 4 bits of the hexadecimal identifier data belonging to the network identifier are different from the first 4 bits of the digital word constituted by the bit or bits of the identification data followed by some at least bits of a

  encoding value corresponding to a character.

  Other advantages and characteristics of the invention

  will appear on examination of the detailed description of embodiments

  and of implementation, in no way limiting, and of the appended drawings, in which: FIG. 1 very schematically represents the internal architecture of a paging receiver according to the invention; - Figure 2 schematically illustrates the architecture of a data block; - Figures 3 and 4 illustrate an example of coding a particular message; and - Figure 5 illustrates an alphanumeric message coding in

the case of an MBS network.

  In FIG. 1, the reference RC designates a paging receiver. This is structured around processing means MP, for example composed of a microprocessor, associated with a random access memory M 1 and a non-volatile memory M2. The address of the receiver is for example stored in the non-volatile memory M2. The messages are received at an antenna AT and transmitted to the microprocessor MP, after preprocessing in reception means MR. After decoding by the processing means MP, the messages are displayed on a display screen AFF. All of these means are supplied by the means

ALM power supply.

  The basic format used to transmit the messages is a BL data block (figure 2), comprising CDU data, on 16 bits,

  followed by 10 bits of a CRC error detection and correction field.

  We will now describe with particular reference to Figures 3 and 4, a compressed transmission of messages

  alphanumeric using two sets of characters.

  By way of example, a first set of characters JC1 and a second set of characters JC2 are defined, each character being coded by a binary coding value VC on 5 bits. Table 1 below details the two character sets JC1 and JC2, as well as their binary coding values. Also shown in this table 1 are the values of

  hexadecimal coding corresponding to the binary coding values VC.

  Finally, in this table, the character "cr" corresponds to a line change instruction (for example usable for receivers of

  paging with multi-line display screens).

TABLE 1

  Encoding value Encoding value 1st character set 2nd binary character set VC hexadecimal VC JC1 JC2 00000 00 space space 00001 01 A cr

02 B "

00011 03 C #

04 D:

00101 05 E%

06 F &

00111 07 G

01000 08 H (

01001 09 I)

01010 OA J *

01011 OB K +

01100 OC L!

01101 OD M

01110 0E N

01111 OF O /

10,000 10 P 0

10001 11 Q 1

10010 12 R 2

10011 13 S 3

10100 14 T 4

10101 15 U 5

10110 16 V 6

10111 17 W 7

11000 18 X 8

11001 19 Y 9

11010 1A Z <

11011 b; =

11100 1C? >

11101 1D

11110 1E,

  A coded DC switching data item is also defined, also coded on 5 bits, and having for example in the present case the

  binary value 11111, corresponding to the hexadecimal value IF.

  Table 1 and the switching data DC are for example stored in the memory M2. We will now describe with particular reference to Figure 3 and Figure 4, the example of message transmission

"NUMBER A2C".

  This message is coded using the coding values VC1-VC10 which are shown in FIG. 3, for simplification purposes, only the hexadecimal values. Of course, the binary values (on 5 bits) of these coding values VC 1-VC 10, as well as the binary value (on 5 bits) of the switching data DC, are inserted in the different data blocks used to transmit the message designated above, in this case

BLA-BLD blocks.

  At the start of each block BLA-BLD, an identification datum I, in this case 1 bit, is inserted which designates the character set JC1 or JC2 valid for the coding values of the current block. As an indication, the logical value "0" of the identification datum I designates the set of characters JC1, essentially alphabetical, while the logical value "1" designates the set of characters JC2 essentially numeric. Therefore, in the BLA block, the data I takes the value O and the binary data VC1 equal to "01110" is interpreted as representative of the character N. In the BLB and BLC blocks, the identification data I is always equal to 0. However, the block BLC comprises, in the last 5 bits, the value of the switching data item DC indicating for the following coding values (in this case the coding value VC9) a change of the character set. More precisely, the value VC9, the binary representation of which is "10010", will therefore be interpreted as corresponding to character 2. The value VC9 is again followed by the switching data DC, indicating that the following coding value whose representation binary is equal to "00011", is representative of the character C. In addition, the identification data item I present in the block

  BLD has the binary value "1".

  Those skilled in the art therefore note that if the BLC block is not received at the receiver, the coding value VC9 will still be correctly interpreted by the processing means MP, due to the

  presence of the identification data item I at the start of the BLD block.

  The basic format used by the MBS standard for transmitting messages is also a BL data block comprising 16-bit CDU data followed by 10 bits of a CRC error detection and correction field. The "data" part of a block can be broken down into

four 4-bit fragments.

  As illustrated more precisely in FIG. 5, the transmission of an alphanumeric message while waiting for a receiver comprises

  several groups of blocks. The first group is made up of BL 1 blocks -

  BL4. The first two fragments FI1 and F21 of the first BLI block of the group contain a network identifier. This network identifier comprises a hexadecimal identifier datum, in this case datum B, inserted in the first fragment F 11, followed by another identifier datum inserted in the second fragment F21, in this case the datum 5. The penultimate fragment F31 of the first block has the value 9 indicating the presence of an alphanumeric message, while the last fragment F41 of the first block indicates, for example, by the value

  0, the beginning of the message, i.e. the first portion of this message.

  Address data A5-AO is located on the second block

  BL2 and the third block BL3 of the group, in the respective fragments F 12-

  F23. The last two fragments F33 and F43 of the third block BL3 indicate the number of blocks or characters of the alphanumeric message. The first portion of the message is then inserted into the data block BL4. The next block BL5 again includes in its first two fragments the network identifier B5, then in the third fragment F35 the value 9 and in the fourth fragment F45 the value 1, indicating that the following blocks will contain the second portion of the

alphanumeric message.

  Those skilled in the art therefore note that the first 4 bits of each data block of the message proper, in this case the first 4 bits of the block BL4, comprising the bit of the identification data item I as well as the first 3 bits of an encoding value, must not interfere with the binary value of the hexadecimal identifier data, in this case data B. In other words, in general, the 4 bits of the data hexadecimal identifier must not correspond to a combination of identification data and an encoding value. More precisely, in the present case, the hexadecimal identifier data, equal to B, is binary coded by the value "1011". The problem therefore arises here for the character set designated by the value "1" of the identification bit I. And therefore it is not necessary that a coding value actually corresponding to a character of the set designated by the value

  "1" of data I, begins with bits "011".

  We will therefore choose, for example, table 2 below, in which the second, essentially numeric character set, JC2, (designated by the value "1" of the identification datum I) does not include any character corresponding to a VC encoding value starting with

3 bits "011".

TABLE 2

  Encoding value Encoding value 1st character set 2nd binary character set VC hexadecimal VC JC1 JC2 00000 00 space space

00001 01 A @

02 B!

00011 03 C #

04 D%

00101 05 E &

06 F

00111 07 G (

01000 08 H)

01001 09 I +

01010 OA J -

01011 OB K /

  01100 OC L prohibited 01101 OD M prohibited 01110 0E N prohibited 01111 OF O prohibited

10,000 10 P 0

10001 11 Q 1

10010 12 R 2

10011 13 S 3

10100 14 T 4

10101 15 U 5

10110 16 V 6

10111 17 W 7

11000 18 X 8

11001 19 Y 9

11010 1A Z <

11011 lB: =

11100 1C? >

11101 1D

11110 lE ,;

Claims (6)

  1. Method for transmitting alphanumeric messages on a network of paging receivers within which messages are transmitted on a carrier within successive blocks of data, characterized in that at least two different sets are developed (JC1, JC2 ) at most 2c alphanumeric characters each, all these characters being coded by coding values (VC) on c bits and together defining a group of at least 2 times 2c alphanumeric characters capable of being used in a message, thus that a predetermined switching data (DC) coded on c bits and representative of a change of the character set corresponding to the coding values, by the fact that the coding values (VC are inserted into the successive blocks of data ) different characters of the message interspersed as many times as necessary with said coded switching data (DC), and by the fact that it is inserted in, and preferably at d purpose, each data block an identification data (I) identifying the character set corresponding to the coding of values inserted in said block after said identification data and to the possible presence   in said block of said switching data.   2. Method according to claim 1, characterized in that the number of character sets developed is equal to 2 and in that said identification data (I) is coded on a single bit whose logical value   denotes either of the two character sets.   3. Method according to claim 1 or 2, for a network within which the messages are transmitted within successive groups of data blocks, each block consisting of an identical number of bits, the first block of each group comprising a first fragment containing hexadecimal identifier data (B) coded on 4 bits and representing at least part of an identifier of said network transmitted at most all b blocks, characterized in that the coded character sets are developed ( JC1, JC2) and the coded identification data (II) so that the first four bits of each data block containing the bits of the identification data and at least some of the bits of a corresponding coding value to a character, are different from the four bits of the   hexadecimal identifier data (B).   4. Paging receiver intended to operate on a paging network within which alphanumeric messages are transmitted on a carrier within successive blocks of data, comprising means of reception (MR) of said carrier, processing means (MP ) capable of processing the different blocks received, and display means (AFF) of the messages contained in the blocks received, characterized in that the receiver comprises a memory (M2) storing at least two different sets (JC1, JC2) at most 2c alphanumeric characters each, all these characters being coded by coding values on c bits and defining together a group of at least 2 times 2c alphanumeric characters capable of being used in a message, as well as a datum switching predetermined (DC) coded on c bits and representative of a change in the character set corresponding to the coding values, by the fact that the means of processing are capable of detecting the value of an identification data item (I) inserted in each data block and making it possible to identify the character set corresponding to the coding values inserted in said block after said identification data and up to to the possible presence in said block of said switching data, so as to decode the coding values from the corresponding character set, and to detect at least one possible presence of the switching data (DC) in the block and to changing the character set according to the value of said switching data, for decoding   coding values according to each switching data.   5. Receiver according to claim 4, characterized in that the number of character sets is equal to 2 and in that said identification data (I) is coded on a single bit whose logical value designates   either of the two character sets.   6. Receiver according to claim 4 or 5, for a network in which the messages are transmitted within successive groups of data blocks, each block consisting of an identical number of bits, the first block of each group comprising a first fragment containing a hexadecimal identifier data (B) coded on 4 bits and representing at least part of an identifier of said network transmitted at most all the b blocks, characterized in that the four bits of the hexadecimal data of identifier (B) are different from the first four bits of the digital word constituted by the bit or bits of the identification data (I) followed by at least some of the bits of an encoding value corresponding to a character.