This invention relates to the area of data transmission between two remote pieces of equipment, and particularly the transmission of binary data using pulse width modulation.

Pulse width modulation consists in encoding the logical status 0 by a pulse with a first width (or duration) Tl and encoding the logical status 1 by a pulse with a second width (or duration) T2 as described in figure 1.

However, in order to properly differentiate between the two logical statuses and do away with noise problems that can occur during transmission, the difference between the two widths (or durations) must be significant, e.g. Tl is a duration T and T2 is a duration 2T.

But large pulse widths lead to longer transmission times and thus reduce the transmission speed.

There is thus a need to offer a method that minimises data transmission time in order to improve the overall data transmission speed.

Thus, this invention relates to a method for transmitting a binary data frame comprising two logical statuses between a first and at least a second piece of communication equipment in which the two logical statuses are encoded by a first and a second distinct pulse widths where:

- the number of occurrences of each logical status within the frame is determined, and

- the frame is pulse- width modulated so that the smaller pulse width is given to the logical status with the larger number of occurrences within the frame.

According to another aspect of this invention, data transmission is carried out via a high-speed single- line protocol.

According to a supplementary aspect of this invention, transmission is bidirectional and alternating.

According to an additional aspect of this invention, the information relating to the convention selected for encoding the logical statuses is encoded in a dedicated location of the transmitted frame.

According to another aspect of this invention, the frame includes a start-of-frame pattern and the dedicated location is a bit located just after the start-of-frame pattern. According to a supplementary aspect of this invention, the binary data of the frame go through a buffer memory before they are transmitted, and the number of occurrences of at least one logical status is counted in the buffer memory.

According to an additional aspect of this invention, counting is carried out in parallel in different distinct areas of the memory frame so as to reduce the counting time.

The embodiment of this invention also relates to a transmission device comprising the following:

- means to determine the number of occurrences of each logical status in a data frame to transmit,

- pulse-width modulation means to associate, with a first and a second logical status respectively of the binary data of the frame to transmit, at least a first and a second distinct pulse width, the logical status with the larger number of occurrences in the frame being associated with the smaller pulse width,

- means to encode, in a dedicated location of the frame, the selected convention indicating the correspondence between a logical status and a pulse width,

- means to transmit a signal that is a data frame to at least one reception device. The embodiment of this invention also relates to a reception device comprising the following

- means to receive a signal that is a data frame transmitted by a transmission device,

- information decoding means that indicate the convention selected for the correspondence between a logical status and a pulse width, located in a dedicated location of the frame,

- frame data demodulation means depending on the selected convention.

The embodiments of this invention also relate to communication equipment comprising a transmission device and a reception device as described above. Other characteristics and advantages of the invention will appear in the description below, by reference to the attached drawings, which illustrate a possible embodiment, for information and in a non-limitative manner.

In these drawings:

- figure 1 represents an example of pulse-width modulation for a sequence of binary data;

- figure 2 represents a synoptic chart of the different stages of an embodiment of this invention;

- figure 3 represents a diagram of the buffer memory and the encapsulation of the data to transmit and their encapsulation in a frame comprising structural fields;

In the description below, the following are generally designated: The embodiments of this invention relate to a method of transmission of a binary data frame based on pulse-width modulation where the convention for the modulation of the logical statuses is adapted on the basis of the data in the frame to transmit.

Thus, out of two distinct pulse widths, the smaller pulse width is allocated to the logical status where the number of occurrences in the data frame is larger. As a result, the larger pulse width is allocated to the logical status with a smaller number of occurrences.

Besides, if the number of occurrences of the two logical statuses is the same within a frame, the convention can then be selected randomly since the transmission time will be the same regardless of the convention selected.

Such a method is particularly well suited to the transmission of data between a first and at least a second piece of communication equipment comprising, for example, a transceiver, that is to say the combination of transmission equipment and reception equipment.

For the purpose of simplification, in the description below, the embodiments described will be limited to communication between a first and a second piece of communication equipment.

Further, the embodiments of this invention can adapt perfectly to transmission managed by a high-speed single-line protocol that allows virtually simultaneous bidirectional transmission (full duplex transmission) in which a single transmission channel is used to transmit in both directions.

In these transmissions, multiplexing may be time-division multiplexing, that is to say that the data are sent alternately from a first to a second piece of communication equipment and from the second to the first piece of communication equipment, alternating, for example, with each bit or each frame.

The different stages of the method will now be described in detail by reference to figure 2.

The first stage 101 is that of the buffering of the data in the frame to transmit in a first piece of communication equipment, comprising for example a transceiver. Indeed, in order to be able to count the number of occurrences of at least one logical status (the number of occurrences of the second logical status can be deducted if the size of a frame is known) within the frame, the frame must necessarily be buffered entirely.

Figure 3 represents an example of a buffer memory 1 comprising one input 3 at which the data frames 5 are received.

Stage 102 is that of the counting of the number of occurrences of the logical status (0 or 1) in a binary data frame by counting means, such as for example a counter that scans the data in the buffer memory and determines the number of occurrences of the logical statuses.

Such counting is carried out in the buffer memory 1. However, the time required for counting is not negligible, and can slow down the transmission of data. In order to reduce that latency time, in one embodiment of this invention, the capacity of the buffer memory 1 is at least two frames, represented here by frames 5' and 5". This may also be referred to as a sequence of buffer memories. Thus, counting on one of the frames 5" is carried out while previous frame 5' is being encoded and sent, which makes it possible to use the latency time due to counting.

Further, in order to reduce the time required for counting, counting may be carried out in parallel, simultaneously in several distinct sectors of the frame, the sum of the different sectors forming the complete frame, for example by using several counters that carry out counting in a given sector. A sector may for example be a group of 8 bits. Thus, the numbers of occurrences of each sector only need to be added together to identify the total number of occurrences of one of the logical statuses.

Once counting is completed, the next stage 103 is that of the selection of the convention for modulation and the encoding of the convention in a dedicated field.

The choice of the convention depends on the result of counting. Thus, if the number of occurrences of a logical status, for example 0, is greater than that of the other status, that is 1, then the selected convention will be that of modulating (or encoding) 0s by the smaller pulse width Tl and modulating Is by the larger pulse width T2.

Once the choice of the convention is made, that choice of convention is encoded in a dedicated field by encoding means so as to inform the receiver of the logical status represented by each pulse width Tl and T2.

Thus, at the output 7 of the buffer memory, structural fields of the frame are added to the data from the buffer memory 1. These structural fields comprise for example a preamble 9, a start-of- frame indicator 11 and an end-of- frame indicator 15. In order to indicate the selected convention to the receiver, a field dedicated to the selected modulation convention 13 is added, comprising an indicator of the convention selected. That dedicated field 13 may be located just after the start-of- frame indicator 11 and just before the data of the frame 5'.

Thus, the indicator of the selected convention may for example be a bit and indicate the convention selected for pulse-width modulation. In practice, the encoding of the convention may for example be to encode 0s by pulses with the smaller width Tl if the bit of the indicator of the selected convention is 0 and encoding Is by pulses with the smaller width Tl if the bit of the indicator of the selected convention is 1.

Besides, if a transmitter does not comprise means to count the number of occurrences of logical statuses, it may select a modulation convention randomly and indicate the selected convention in the dedicated field so that the signal can be demodulated by the receiver even if the transmitter does not have the means to count the number of occurrences of the logical statuses in a frame.

The next stage 104 is that of modulating the signal in pulse widths according to the selected convention by means for pulse- width modulation such as a modulator.

Stage 105 is that of sending the pulse- width modulated signal using transmission means from a first piece of communication equipment to a second piece of communication equipment. As described above, the signal may be sent in a single block of data or in several blocks so as to allow the virtually simultaneous transmission, on an alternating basis in the opposite direction, in the case of single-line time-division multiplexing.

Stage 106 is the reception of the pulse- width modulated signal by the second piece of communication equipment, using reception means.

Stage 107 is that of decoding, using decoding means, the field dedicated to the selected modulation convention. Thus, depending on the selected convention, the receiver can configure demodulation means so as to retrieve the logical statuses encoded by the first piece of communication equipment depending on the pulse widths.

In practice, depending on the value of the indicator of the selected convention, the position of a selector with two positions is adjusted, one indicating decoding where the smaller pulse widths represent 0s and the other indicating decoding where the larger pulse widths represents Is.

The last stage 108 is that of demodulating the signal received, using demodulation means such as for example a demodulator, on the basis of the value of the indicator of the selected convention, in order to retrieve the binary data transmitted.

Thus, the determination of the number of occurrences of logical statuses in a binary data frame and the adaptation of the pulse-width modulation convention depending on the number of occurrences of the logical statuses so as to encode the logical status with the larger number of occurrences by the smaller pulse width makes it possible to minimise the duration of the frame to transmit so as to improve the transmission speed. Further, such speed improvement is achieved by simple modifications of the transmission and reception equipment and thus requires low investment for implementation.