FR2941830A1 - Data sequence's sequential transfer method for global system for mobile communication data network, involves performing transfer of data and following data based on reception of acknowledgement of transferred data - Google Patents

Abstract

The method involves transferring data (D0-D5) based on a transfer request (Req) transmitted to a transmitting unit (E) by a receiving unit (R). The data is transferred based on the reception of acknowledgment (Ack0) of previously transferred data. The data is transmitted so that normal transfer delay of data is equal to a period (T). The transfer of the data and following data are performed based on the reception of acknowledgement of transferred data when the transfer of the following data is not caused by the reception of transfer acknowledgement (Ack1) of preceding data. An independent claim is also included for a device for implementing a method for sequential transfer of data sequence between a transmitting unit and a receiving unit.

Description

The present invention relates to a method for sequentially transferring a data stream between a transmitting unit and a receiving unit. It applies in particular, but not exclusively, to a method for transferring data included in a recording apparatus, via a network, to a computer server, the recording apparatus being connected to a measuring apparatus of type electric meter.

In general, it is known that there are counters whose recorded data can be recorded remotely, using in particular the GSM network ("Global System for Mobile Communications"). Generally, the protocols implemented to enable the transmission of data recorded in these "liftable" tele-meters are in particular: • proprietary protocols such as the "Trimaran" protocol of EDF ("Électricité de France"), which are related to older modems such as the V23HD, which results in slow data transmission. In addition, the acknowledgments required for each data exchange strongly penalize the adaptations to networks of GSM data type; Subsequent proprietary protocols such as Device Language Message Specification (DLMS) and Trimaran + protocols, which are related to modems such as V22bis, data transmission in These protocols, although faster than those based on previous protocols, remain slow; • generic protocols such as the "DLMS / COSEM" protocol ("Companion Specification for Energy Metering"), which allow the data to be transmitted more quickly than in the previous cases. Nevertheless, this type of protocol requires the transmission of a large quantity of data. data due to coding done almost exclusively in ASCII.

The invention is therefore more particularly intended to overcome these drawbacks by proposing a method that makes it possible to transfer data included in a recording device, via a network, to a computer server, the implementation of this method allowing fast data transmission even when traveling on slow "return-to-go" networks, such as networks of the GSM data type.

To this end, the invention proposes a method for the sequential transfer of a data sequence C 1 to D 2 between a transmitting unit E and a receiving unit R, in which: the transfer of the data C 1 to D 1, with m > i> 0. is performed following a transfer request Req, transmitted to the transmitting unit E by the receiver unit R, i being a constant; The transfer of a data item with m> j> i is effected following the reception of the acknowledgment ACKK _ i by the sending unit E from the receiving unit R, of a datum Di _ i previously transferred to the receiving unit R, j being a variable; characterized in that: • the data Do to Dm are transmitted so that the normal transfer delay of two successive data Dnt and Dnt +1, with m> nt 0, is substantially equal to a period T; Receiving the acknowledgment ACKK _ i by the sending unit E, of a transferred data Di _ i, generating the transfer of the data Di and the transfer of the next data Di + 1, in the case where the transfer of this next data item Di + has not been triggered by the reception by the sending unit E of the acknowledgment ACKU (j) + of the transfer of the previous data Da (j) + 1.

Thus, for example, when i = 2, the data sequence Do to Dm comprises two sets of interleaved data namely, a series of even rank and a series of odd rank. In this way, the reception of an acknowledgment ACKK _ 2 by the transmitting unit E, of a transferred data Di _ 2 of a series (for example of even rank), generating the transfer of the next data item Di of the same series, as well as the transfer of the next data Di + 1 of the other series (the latter being in this case of odd order) in the case where the transfer of this next data item Di + 1 has not been triggered by the reception by the transmitter unit E of the ACKK acknowledgment of the transfer of the previous data Di of this other series.

In this way, the implementation of the method according to the invention allows the transfer of at least i successive data of a sequence of data Do to Dm without waiting for the reception of the acknowledgment of these i successive data, which allows not to be penalized by the relatively long delays of exchanges "go back" returns networks of the type GSM data. In addition, the absence of receipt of an acknowledgment by the transmitting unit E does not necessarily interrupt the data transfer, the receipt of an acknowledgment that can be used to control the transfer of several data.

Advantageously, the method according to the invention may comprise an additional step for retransmitting data in the event that several consecutive acknowledgments have not been received by the transmitting unit E, after a predetermined delay.

An embodiment of the invention will be described hereinafter, by way of non-limiting example, with reference to the accompanying drawings in which: FIG. 1 is a schematic representation of data exchanges and corresponding acknowledgments between an emitting unit and a receiving unit.

FIG. 2 is a schematic representation of data exchanges and corresponding acknowledgments between a transmitting unit and a receiving unit, in the case where an acknowledgment is not received by the transmitting unit.

FIG. 3 is a schematic representation of a flowchart of steps, the implementation of which allows initialization of transfer requests by the receiving unit.

FIG. 4 is a schematic representation of a flowchart of steps, the implementation of which allows the reception of the data and the sending of corresponding acknowledgments by the receiving unit.

FIG. 5 is a schematic representation of a flowchart of steps the implementation of which allows the sending unit to send data. Figure 6 is a schematic representation of the structure and format of the frames exchanged between the transmitting unit and the receiving unit.

Fig. 7 is a schematic representation of the octet-coded function field of a frame transmitted by the receiver unit to the transmitting unit. Fig. 8 is a schematic representation of the octet-coded function field. a frame transmitted by the transmitting unit towards the receiving unit. Fig. 9 is a schematic representation of the double-byte function field of a frame transmitted by the receiving unit towards the transmitting unit.

By way of nonlimiting example, as is illustrated in FIGS. 1 and 2, the implementation of the method according to the invention, which allows the sequential transfer of a data sequence Do to Dm between an emitting unit E and a receiver unit R, results in: • the transmission of a transfer request Req by the receiver unit R to the sending unit E; • the transfer of the data Do to Di _ 1, with m> i> 0, which is performed following the receipt of the transfer request Req by the sending unit E; in this case, i, which defines the size of a transmission window, is therefore 2, in this example the data D 1 to D 1 are transmitted following receipt of the transfer request Req ; The transfer of a data item with m> j> i, which takes place following the reception of the acknowledgment ACKi _ i by the sending unit E from the receiving unit R, of a piece of data Di _ i previously transferred to the receiving unit R; for example, if j is 3, the data D3 is transmitted on receipt of the acknowledgment ACK1 by the transmitting unit E; The reception of the acknowledgment ACKi _ i by the sending unit E, of a transferred data Di _ i, generating the transfer of the data Di as well as the transfer of the next data Di + 1, in the case where the Transfer of this next data item Di + 1 has not been triggered by the reception by the transmitter unit E of the acknowledgment ACK (1) + 1 of the transfer of the preceding data item C (j) + 1. ; thus, as shown in FIG. 2, by taking j equal to 3, the reception of the acknowledgment ACK1 by the sending unit E of the transferred data D1 generates the transfer of the data item D3 as well as the transfer of the next data item D4 even if the transfer of this next data item D4 has not been triggered by the reception by the sending unit E of the acknowledgment ACK2 of the transfer of the previous data item D2.

By way of example, the process of initializing transfer requests Req by the receiving unit R is shown schematically, in flowchart form, in FIG. 3. Thus, this initialization process may comprise the following steps: • 1) setting to o, in the idle state, the following parameters: o "nrq" which corresponds to the number of times that a same transfer request Req is sent by the receiver unit R; o "nt" which corresponds to the frame number of each data of the data sequence Do to Dm to be transmitted; o "tabort" which is a time counter; 2) the sending by the receiving unit R of the transfer request Req and the triggering of the time counter "trep" which was initially at 0, the system going from an inactive state to a state of transaction initialization; • 3) the determination of whether the duration defined by the counter "trep" is greater than a constant "TR" which corresponds to the time beyond which the transmission of the transfer request Req is repeated; • 4.a) if this "TR" delay is exceeded without any response being received by the receiving unit R, the parameter "nrq" is incremented by one unit; • 4.b) determining whether the value of the parameter "nrq" is greater than a constant "NRP" which corresponds to the maximum possible number of repetitions of the transmission of the transfer request Req in the event of absence Answer ; • 4.c.1) if the value of the parameter "nrq" is greater than the constant "NRP", the implementation of said initialization process is aborted; • 4.c.2) if the value of the parameter "nrq" is not greater than the constant "NRP", the initialization process resumes in step 2), the transfer request Req being retransmitted; • 5) following step 3), if the delay "TR" is not exceeded, determining whether the response received by the receiving unit R consists of a number frame "nt" namely, a frame of number 0; • 6) if this answer does not consist of a frame of the above type, the initialization process resumes in step 3); • 7) if this response consists of a frame of the above type, determining whether it is a FIN or NACK frame; • 8) if this frame is a frame of FIN or NACK, the finding that the requested data is not available; • 9) if this frame is not a frame of FIN or NACK, the determination of whether it is a frame of data; • 10) if this frame is not a data frame, the initialization process resumes in step 3); • 11) if this frame is a data frame, the finding that the data is received.

The process of receiving data by the receiving unit R which follows the process of initialization of transfer requests Req is shown schematically, in flow chart form, in FIG. 4. Thus, this data reception process can comprise the following: following steps: • 1) sending the acknowledgment ACK "nt" by the receiving unit R in the case where the latter has received the number data frame "nt"; • 2) the recording of this data frame of number "nt" by the receiver unit R, the incrementation of "nt", and the zeroing followed by the initialization of the "tabort" counter; • 3) determining whether the number data frame "nt" ("nt" having been incremented in the previous step) has been received by the receiver unit R; • 4.a) if this number frame "nt" has not been received by the receiving unit R, determining whether the duration defined by the value of the parameter "tabort" is greater than the constant " TAB "which corresponds to the maximum delay time before stopping the process in the case where the number data frame" nt "has not been received; • 4.b.1) if the value of the "tabort" parameter is greater than the "TAB" constant, the implementation of the said data reception process is aborted; • 4.b.2) if the value of the "tabort" parameter is not greater than the "TAB" constant, the data reception process resumes in step 3); • 5) following step 3), if this number frame "nt" has been received by the receiving unit R, determining whether it is a data frame; • 6) if this frame is a data frame, the initialization process resumes in step 1); • 7) if this frame is not a data frame, determining whether it is an END frame; • 8) if this frame is not an END frame, the data reception process resumes in step 3); • 9) if this frame is an END frame, the sending by the receiving unit R to the sending unit E of the acknowledgment ACK "nt"; • 10) following step 9), the passage of the receiving unit R in standby state.

The process of sending the data by the sending unit E is schematically shown in flowchart form in FIG. 5. Thus, this data sending process can comprise the following steps: 0, in the idle state, of the following parameters: o "nt" which corresponds to the frame number of each data element of the data sequence Do to Dm to be transmitted; O "nta" which corresponds to the number of the last frame accepted by the receiver unit R by means of an acknowledgment ACK; o "tabort" which is a time counter; o "trep" which is a time counter; • 2) determining whether the number request "nt" was received by the receiving unit R; • 3.a) if this request number "nt" was not received by the receiving unit R, the determination of the point of knowing: o if the duration defined by the value of the parameter "tabort" is equal to the constant "TAB" which corresponds to the maximum delay time before stopping the process in the case where the number request "nt" was not received; or o if a FIN frame has been received; • 3.b) if the value of the "tabort" parameter is equal to the "TAB" constant or if a FIN frame has been received, the implementation of said data sending process is aborted; • 3.c) if the value of the "tabort" parameter is not equal to the "TAB" constant or if a FIN frame has not been received, the data sending process resumes in step 2) ; 4) following step 2), if said request has been received, the analysis of the latter is carried out, at this step the system goes from an inactive state to a transaction state; 2941830 - 10- • 5) the preparation of the page number "nt"; • 6) sending the frame "nt" by the sending unit E; • 7) determining whether the ACK acknowledgment of number "x" was received by the sending unit E; 8.a) if this ACK acknowledgment of number "x" has been received by the sending unit E, determining whether: "nta" <"x" <"nt"; • 8.b) if "x" does not satisfy this double inequality, the implementation of the said data sending process is abandoned; • 8.c) if "x" satisfies this double inequality: o the variable "nta" is assigned the value "x", the last frame accepted by the receiving unit R being that of number "x"; o the "tabort" and "trep" counters are set to zero; • 9) following step 7), if the acknowledgment ACK of number "x" has not been received by the sending unit E, or following step 8.c), the determining the point of knowing: o whether the duration defined by the value of the "tabort" parameter is greater than the "TAB" constant; or o if a FIN frame has been received; • 10) if the value of the "tabort" parameter is greater than the "TAB" constant or if a FIN frame has been received, the implementation of the said data sending process is aborted; • 11) if the value of the "tabort" parameter is not greater than the "TAB" constant or if a FIN frame has not been received, the determination of whether the "nt" number page is the last page ; • 12.a) if it is the last page, determining whether "nt" = "nta" • 12.b) if "nt" = "nta", the process of sending the data is repeated in step 1); • 13.a) following step 1l, if it is not the last page, the determination of whether "nt" ≠ "nta" + "i", "i" being the dimension of the transmission window; 2941830 -11- • 13.b) if "nt" ≠ "nta" + "i", "nt" is incremented and the data reception process resumes in step 5); • 14) following step 12.a) if "nt" ≠ "nta" or following step 13.b) if "nt" = "nta" + "i", the determination of whether the duration defined by the counter "trep" is greater than a constant "TRP" which corresponds to the delay beyond which the transmission of the last unacknowledged frame is repeated; • 15) if the duration defined by the counter "trep" is not greater than the constant "TRP", the process of sending the data resumes in step 7); 10 • 16) if the duration defined by the counter "trep" is greater than the constant "TRP": o "nt" is assigned the value "nta"; o "trep" is set to zero; • 17) after step 16, the variable "nt" is incremented; 15 • 18) the data sending process resumes in step 5).

The transmitting unit E and the receiving unit R can each comprise, in particular but not exclusively,: • a central processing unit (UCT, not shown) which makes it possible, in particular, to carry out the processing necessary for the execution of said steps; Memory means (not shown) such as permanent memory (ROM) and / or volatile memory (RAM) notably making it possible to record the data received or to be transmitted; A management means (not shown) for transferring the data.

As shown in FIG. 6, a frame 1 exchanged between a transmitting unit E and a receiving unit R may comprise: • a field "L" which indicates the total number of bytes of the frame, the coding of this frame length preferably taking place on one byte; • a "Function" field; 2941830 - 12 - • at least one "Data" field that includes the data to be transferred; • at least one "CRC" ("Cyclic redundancy check" - "CRC h", "CRC 1") field which corresponds to a cyclic redundancy check.

As shown in FIG. 7, in the case of a frame transmitted by the receiver unit R towards the transmitting unit E, the "Function" field may be coded on a single byte and may correspond to: An ACK acknowledgment: the first four bits that can correspond to the number of the last frame of the window; o the next four bits can be equivalent to "0 0 0 0"; or • a no to NACK acknowledgment: o the first four bits may correspond to the number of the last frame of the window; O the next four bits may be equivalent to "1 1 1 1"; or • at the end of the session "END SESSION".

As shown in FIG. 8, in the case of a frame transmitted by the transmitting unit E towards the receiver unit R, the "Function" field 20 may be coded on a single byte and may correspond to: • the indication ("FIN DATA") that the data has been transmitted; or • the indication ("DATA") according to which the frame comprises data.

According to an alternative embodiment of the invention, as shown in FIG. 9, in the case of a frame transmitted by the receiver unit R towards the transmitting unit E, the "Function" field It may be double-byte and may indicate the date or, more precisely, the periodicity at which the data will be transferred from the transmitting unit E to the receiving unit R, which is particularly advantageous when the transmitting unit E is a meter-type measuring device and the receiver unit R a computer server. By way of nonlimiting example, the coding can be carried out in the following manner: the first five bits of the low byte can correspond to the day; • the sixth bit of this low byte is set to zero by default; The last two bits of this low byte may correspond to the interval (in minutes) for storing the data; in this case, for example: o "0 0" can be one minute; o "0 1" can be five minutes; o "1 0" can be ten minutes; 15 "1 1" may be thirty minutes; • the first four bits of the most significant byte may be the month; The fifth bit of the most significant byte corresponds to the value "Z" which is a variable making it possible to increase the coding possibilities; • The last three bits of this high byte are set to zero by default.

Claims (18)

Revendications1. A method for the sequential transfer of a data sequence Dm to Dm between a sending unit E and a receiving unit R, in which: • the transfer of the data D 1 to D 1 with m> i> 0 takes place following a transfer request Req, transmitted to the transmitting unit E by the receiving unit R; • the transfer of a data with m> j> i, is carried out after receiving the acknowledgment ACKi _; by the transmitting unit E from the receiver unit R, a datum Di _; previously transferred to the receiver unit R; characterized in that: • the data Do to Dm are transmitted so that the normal transfer delay of two successive data Dm and Dm +1, with m> n> 0, is substantially equal to a period T; • receipt of ACKK acquittal _; by the sending unit E, a transferred datum Di _ ;, generating the transfer of the data Di as well as the transfer of the next data Di + 1, in the case where the transfer of this next data Di + 1 n ' was not triggered by the reception by the transmitting unit E of the acknowledgment ACKa (j) + of the transfer of the previous data D (j) +1. 2. Method according to claim 1, characterized in that it comprises an additional step for retransmitting data in the event that several consecutive acknowledgments have not been received by the transmitting unit E, after a delay predetermined. 3. Method according to one of claims 1 and 2, characterized in that the process of initialization of transfer requests Req by the receiving unit R comprises the following steps: • 1) setting o. in the idle state, the following parameters: o "nrq" which corresponds to the number of times that the same transfer request Req is sent by the receiver unit R; o "nt" which corresponds to the frame number of each data of the sequence of data Do to Dm to be transmitted; o "tabort" which is a time counter; 2) the sending by the receiving unit R of the transfer request Req and the triggering of the time counter "trep" which was initially at 0, the system going from an inactive state to a state of transaction initialization; • 3) determining whether the duration defined by the counter "trep" is greater than a constant "TR" which corresponds to the delay beyond which the transmission of the transfer request Req is repeated; • 4.a) if this "TR" delay is exceeded without any response being received by the receiving unit R, the parameter "nrq" is incremented by one; • 4.b) the determination of whether the value of the parameter "nrq" is greater than a constant "NRP" which corresponds to the maximum possible number of repetitions of the transmission of the transfer request 20 Req in case of lack of response; • 4.c.1) if the value of the parameter "nrq" is greater than the constant "NRP", the implementation of said initialization process is aborted; • 4.c.2) if the value of the parameter "nrq" is not greater than the constant 25 "NRP", the initialization process resumes in step 2), the transfer request Req being retransmitted; • 5) following step 3), if the delay "TR" is not exceeded, determining whether the response received by the receiving unit R consists of a frame of number "nt", namely a frame 30 of number 0; 2941830 - 16- • 6) if this answer does not consist of a frame of the above type, the initialization process resumes in step 3); • 7) if this response consists of a frame of the aforesaid type, determining whether it is a FIN or NACK (non-acknowledgment) frame; • 8) if this frame is a frame of FIN or NACK, the finding that the requested data is not available; • 9) if this frame is not a frame of FIN or NACK, determining whether it is a frame of data; 10 • 10) if this frame is not a data frame, the initialization process resumes in step 3); • 11) If this frame is a data frame, the finding that the data is received. 4. A method according to claim 3, characterized in that the process of receiving data by the receiving unit R, which follows the process of initializing Req transfer requests, comprises the following steps: • 1) sending the acknowledgment ACK "nt" by the receiving unit R in the case where the latter has received the number data frame "nt"; • 2) the recording of this data frame of number "nt" by the receiver unit R, the incrementation of "nt", and the zeroing followed by the initialization of the "tabort" counter; • 3) determining whether the number 25 "nt" data frame ("nt" having been incremented in the previous step) has been received by the receiver unit R; • 4.a) if this number frame "nt" has not been received by the receiving unit R, determining whether the duration defined by the value of the parameter "tabort" is greater than the constant " TAB "which corresponds to the maximum delay time before the process is stopped in the case where the number data frame" nt "has not been received; • 4.b.1) if the value of the "tabort" parameter is greater than the "TAB" constant, the implementation of said data reception process is aborted; • 4.b.2) if the value of the "tabort" parameter is not greater than the "TAB" constant, the data reception process resumes in step 3); 5) following step 3), if this number frame "nt" has been received by the receiver unit R, determining whether it is a data frame ; • 6) if this frame is a data frame, the initialization process resumes in step 1); • 7) if this frame is not a data frame, determining whether it is an END frame; • 8) if this frame is not an END frame, the data reception process resumes in step 3); • 9) if this frame is an END frame, the sending by the receiving unit R to the sending unit E of the acknowledgment ACK "nt"; 20 • 10) following step 9), the passage of the receiving unit R in the standby state. 5. Method according to one of claims 3 and 4, characterized in that the process of sending data by the emitting unit E 25 comprises the following steps: 1) the setting to 0, in the inactive state, the following parameters: o "nt" which corresponds to the frame number of each data item of the data sequence Do to Dm to be transmitted; o "nta" which corresponds to the number of the last frame accepted by the receiver unit R by means of an acknowledgment ACK; o "tabort" which is a time counter; 2941830 -18- o "trep" which is a time counter; • 2) determining whether the number request "nt" was received by the receiving unit R; • 3.a) if this number request "nt" has not been received by the receiving unit R, determining the point of knowing: o if the duration defined by the value of the parameter "tabort" is equal to the constant "TAB" which corresponds to the maximum delay time before stopping the process in the case where the number request "nt" was not received; or o if a FIN frame has been received; • 3.b) if the value of the "tabort" parameter is equal to the "TAB" constant or if a FIN frame has been received, the implementation of the said data sending process is aborted; • 3.c) if the value of the "tabort" parameter is not equal to the constant "15 TAB" or if a FIN frame has not been received, the data sending process resumes in step 2 ); 4) following step 2), if said request has been received, the analysis of the latter is carried out, at this step the system goes from an inactive state to a transaction state; 20 • 5) the preparation of the page number "nt"; • 6) sending the frame "nt" by the sending unit E; • 7) determining whether the ACK acknowledgment of number "x" was received by the sending unit E; 8.a) if this ACK acknowledgment of number "x" has been received by the transmitting unit E, determining whether: "nta" <"x" <"nt"; • 8.b) if "x" does not satisfy this double inequality, the implementation of the said data sending process is abandoned; • 8.c) if "x" satisfies this double inequality: o the variable "nta" is assigned the value "x", the last frame 30 accepted by the receiving unit R being that of number "x"; o the "tabort" and "trep" counters are set to zero; 2941830 - 19- • 9) following step 7), if the acknowledgment ACK of number "x" has not been received by the sending unit E, or following step 8. c), determining the point of: o whether the duration defined by the value of the parameter "tabort" is greater than the constant "TAB"; or o if a FIN frame has been received; • 10) if the value of the "tabort" parameter is greater than the "TAB" constant or if a FIN frame has been received, the implementation of the said data sending process is aborted; 10 • 11) if the value of the "tabort" parameter is not greater than the "TAB" constant or if a FIN frame has not been received, the determination of whether the "nt" number page is the last page; • 12.a) if it is the last page, the determination of whether "nt" = "nta" 15 • 12.b) if "nt" = "nta", the process of sending the data is repeated in step 1); • 13.a) following step 11, if it is not the last page, the determination of whether "nt" ≠ "nta" + "i", "i" being the dimension of the transmission window; 20 • 13.b) if "nt" ≠ "nta" + "i", "nt" is incremented and the data reception process resumes in step 5); • 14) following step 12.a) if "nt" ≠ "nta" or following step 13.b) if "nt" = "nta" + "i", determining the point whether the duration defined by the counter "trep" is greater than a constant "TRP" which corresponds to the delay beyond which the transmission of the last unacknowledged frame is repeated; • 15) if the duration defined by the counter "trep" is not greater than the constant "TRP", the process of sending the data resumes in step 7); • 16) if the duration defined by the counter "trep" is greater than the constant "TRP": o "nt" is assigned the value "nta"; 2941830 - 20 - o "trep" is set to zero; • 17) following step 16, the variable "nt" is incremented; • 18) the data sending process resumes in step 5). 6. Method according to one of the preceding claims, characterized in that a frame (1) exchanged between a transmitting unit E and a receiving unit R comprises: • a field "L" which indicates the total number of bytes of the frame • a "Function" field; At least one "Data" field which includes the data to be transferred; • at least one "CRC" field that corresponds to a cyclic redundancy check. 7. Method according to claim 6, characterized in that in the case of a frame transmitted by the receiver unit R towards the transmitting unit E, the "Function" field is coded on a single byte and corresponds to: • an ACK acknowledgment; or • a no to NACK acknowledgment; or 20 • at the end of the session "END SESSION". 8. Method according to one of claims 6 and 7, characterized in that in the case of a frame transmitted by the transmitting unit E towards the receiving unit R, the "Function" field is coded on a single byte 25 and corresponds to: • the indication ("FIN DATA") according to which the data has been transmitted; or • the indication ("DATA") according to which the frame comprises data. 9. A method according to claim 6, characterized in that in the case of a frame transmitted by the receiver unit R towards the transmitting unit E, the "Function" field is coded on two bytes. in order to indicate the date or more precisely the periodicity at which the data 5 will be transferred from the transmitting unit E to the receiving unit R. 10. The method according to claim 9, characterized in that the coding takes place from the as follows: • the first five bits of the least significant byte correspond to the day; The sixth bit of this low byte is set to zero by default; • the last two bits of this low-order byte correspond to the interval (in minutes) for storing the data; • the first four bits of the most significant byte correspond to the month; The fifth bit of the most significant byte corresponds to the value "Z" which is a variable making it possible to increase the coding possibilities; • The last three bits of this high byte are set to zero by default. Apparatus for carrying out the method according to claim 1, characterized in that the transmitter unit E and the receiver unit R each comprise: a central processing unit (CPU); Memory means such as permanent memory (ROM) and / or volatile memory (RAM); A data transfer management means.