Multiplex communications – Communication over free space – Using atm as a wireles protocol
Patent
1995-11-13
1998-06-30
Safourek, Benedict V.
Multiplex communications
Communication over free space
Using atm as a wireles protocol
370447, 370462, 455528, H04B 700
Patent
active
057744599
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to methods that enable the management of the transmission of messages coming from a set of transmitters to a single receiver that is common to them, when the transmission channel is formed by a single channel through which all these messages have to travel.
In a system of transmission comprising several transmitters and a single receiver connected together by a single channel, it is essential to manage the transmission of the messages so as not to bring about any confusion between them. In a radiotelephony network for example, an essentially oral procedure is used, relying basically on the operators' intelligence. In a data transmission system that generally works automatically, a more set procedure is used, applied by logic devices located both in the transmitters and in the receiver. These methods are known, for example, by the names of ALOHA, CSMA, CSMA/CD, etc.
Most of these methods use a system for the dispatch of acknowledgment messages carried out by the transmission of data elements from the single main receiver to the transmitters. These transmitters therefore must comprise a data reception system that necessarily has a certain degree of complexity.
This is also the case in CSMA type anti-collision methods where the transmission channel is listened to in order to detect a possible collision or else an indication of collision is sent from the receiver when such a collision has taken place. Here too, the receivers must have a data reception system of non-negligible complexity.
Systems are currently being developed, comprising transmitters connected to a single receiver by a single channel. For example, reference may be made to microwave badges which are designed for many uses, for example checking access and highway tollgate payment. It is being attempted to make these badges in the form of a card, preferably having the size and weight of a credit card, possibly integrating a cell that must last several years. It can easily be seen that, in this case, the addition of a data receiver and the complexity of the management of transmission could be prohibitive in every respect.
Since, furthermore, these cards necessarily work at only one frequency as they have to be made in several copies and have to capable of functioning in a large number of distinct places spread out over a territory, it is absolutely imperative to manage the collision of the messages that they transmit almost simultaneously towards one and the same receiver. It is important that the data reception system as well as the management procedures should be extremely simplified, for these transmitters must be small and must cost little.
This problem has not been resolved satisfactorily up till now.
OBJECTS AND SUMMARY OF THE INVENTION
To resolve this problem, the invention proposes a method for managing the transmission of the messages from a set of transmitters to a single receiver on a single channel, chiefly characterized in that as soon as the receiver receives the transmission from one of the transmitters, it sends all the receivers, at least throughout the period of transmission by the active transmitter, a binary information element indicating that the channel is busy, and in that the reception of this binary information element inhibits any attempted transmission by the other transmitters.
BRIEF DESCRIPTION OF THE DRAWINGS
Other particular features and advantages of the invention shall appear more clearly in the following description, given by way of a non-restricted example with reference to the appended figures of which:
FIG. 1 shows a drawing of a set of transmitters connected to a single receiver;
FIG. 2 shows a first timing diagram;
FIG. 3 shows a simplified drawing of a transmitter; and
FIG. 4 shows a second timing diagram;
FIG. 5 shows a timing diagram in the case of a full-duplex transmission.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In the following description, to simplify matters, the term "receiver" shall be used for the unit responsible for receiving dat
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Gemplus Card International
Rao Seema S.
Safourek Benedict V.
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