Pulse or digital communications – Transceivers – Modems
Reexamination Certificate
1999-12-10
2003-09-23
Le, Amanda T. (Department: 2634)
Pulse or digital communications
Transceivers
Modems
C370S236000, C379S229000
Reexamination Certificate
active
06625210
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims priority of European Patent Application No. 98460058.5, which was filed on Dec. 15, 1998.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The field of the invention is that of methods for the transmission of telephone calls in multiple bit-rate transmission channels.
The invention can be applied especially to the case of multiple bit-rate links set up between a central station and the remote peripheral stations of a network in a star or hub-and-spoke configuration.
2. Description of the Related Art
A network of this kind corresponds for example to <<rural>> telephony infrastructures, typical in regions that are under-equipped in wire or cabled networks and/or have a low density of potential subscribers.
It can be applied especially when a terminal involved in a communication using a network of this kind may require resources with different bit-rates depending on whether it is seeking, for example, to set up either a simple voice call or a transfer of data of the type requiring action by a modem (for example for a connection on an <<internet>> type open network. In this case, indeed, a voice call will require a lower transmission bit rate than a data transfer.
A first known approach consists in routinely providing a bit rate that is capable of coping with the highest resource requirement. However, this approach means under-utilization of the transmission channel since, in the case of simple voice calls for example, the allocated transmission bit rate will be far greater than needed.
A second approach consists of the use of a multiple bit-rate channel to transmit this type of call. However, those skilled in the art are dissuaded from using this technique because of the complexity of the procedures for allocating existing bit rates, which are not compatible with the constraints of communications involving modems, especially in the vital initial stages of setting up calls and of inter-modem negotiation.
Indeed, a change in the bit rate of the line allocated as a function of need implies the implementation of bit-rate switching procedures, to increase or reduce the bit rate allocated to the demand. However, a classic switching of the transmission channel entails the risk that the bit-rate switching is not exactly simultaneous and synchronized in both directions of transmission. The disturbance resulting therefrom is indeed likely to abort the procedure for setting up communications between the modems, and this risk cannot be tolerated in the context of a switching service which is expected to show reasonable reliability and efficiency with a success rate close to 100% when the communications are set up.
The call procedure between two modems, one of them being with a multiple bit-rate telephone subscriber (calling or called subscriber), can be subdivided into four phases:
making the 32 kbit/s call;
connecting the two modems;
procedure for negotiating the speed of transmission between the two modems;
transfer of the data elements.
In accordance with recommendation V25, the modem connection phase can be subdivided as follows:
the calling modem, after getting linked up and dialling the number, sends an uninterrupted call tone to the called modem;
the called modem takes the call, gets connected to the line and, after a silence, sends the response tone constituted by a continuous signal at 2100 Hz;
as the case may be, the modems can deactivate network echo cancellers and/or suppressors devices, by making or not making phase reversals at regular intervals (typically every 450±25 ms), as specified in the G164 and G165 recommendations.
the calling modem, after recognizing the answering tone, waits for reception of a silence of 75±25 ms coming from the called modem, and then goes into the negotiation phase. To accelerate the procedure, this calling modem can inform the called modem that it has recognized its reponse by sending it a response tone of the calling modem: in recognizing this signal, the called modem stops sending the response tone and then, after 75±20 ms of silence, goes into the negotiation phase.
In the absence of response signal of the calling modem, the called modem sends the response tone for 3,3 s±0,7 s, then after 75±20 ms of silence goes into the negociation phase.
To enable the modems to work with an optimum bit rate, the switching of the bit rate (namely the changing of the transmission channel) must be ended before the beginning of the procedure of negotiation between the modems.
This means that the following conditions should be met, in assuming the most unfavorable case, namely the setting up of a call with a minimum-duration response signal of the called modem:
i—the response of the called modem should not be interrupted for a duration of more than 55 ms, otherwise the calling modem could go into the negotiation phase;
ii—no action (such as a bit-rate switching operation) on the response half-channel of the called modem should take place after the lapse a certain period of time starting from the response tone on the line, beyond which the phase of negotiation is automatically started (655 ms in the case of an operation of neutralization of the echo suppressors only, 1 255 ms in the case of a neutralization of the echo cancellors and suppressors);
iii—any action must also take place after approximately 950 ms, i.e. for the duration of at least two phase reversals, should the modems seek to neutralize both the echo cancellors and the suppressors.
SUMMARY OF THE INVENTION
The invention forms part, especially, of this context of constraints that could be contradictory.
Thus, it is a first goal of the invention to put forward the novel problem of the default allocation, at each request for setting up a call, of a minimum transmission bit rate, although this bit rate is paradoxically insufficient for certain types of communication available to the subscriber.
A complementary goal is to provide a call setting-up procedure that makes it possible to optimize resource allocation by the authorizing, at request, of the allocation of a bit rate higher than the bit rate allocated by default.
Another goal of the invention is to provide a bit-rate allocation procedure of this kind that is compatible with the severe constraints dictated by the procedures for setting up calls between two modems.
It is also a goal of the invention to provide a bit-rate allocation procedure that does not require the addition of a piece of information or the processing of a piece of information supplementary to the items of information presently available in standard call-making procedures and that is activated in particular without any advance knowledge of the nature of the transmission requested by the user or any advance knowledge of the transmission bit rate required by his call.
It is a goal of the invention therefore to provide a solution that meets at least the case where the modems seek to neutralize both the echo cancellers and the echo suppressors during the connection phase when the bit-range switching according to the invention comes into play.
These different goals as well as others that shall appear hereinafter are achieved according to the invention by means of a call setting-up procedure with bit-rate allocation in a multiple bit-rate transmission channel enabling the routing of a call between a central module and a remote module, of the type comprising at least one first transmission channel at a primary bit rate and at least one second transmission channel at a secondary bit rate, a procedure in which said first and second transmission channels are two-way channels, namely channels constituted by a first transmission half-channel in a first direction of communication and a second transmission half-channel in a second direction of communication, a procedure wherein said call setting-up procedure comprises the following successive phases:
a phase for setting up a call, by default, on a primary bit-rate transmission channel,
a phase of listening and searching f
Boissel Guy
Connan Christophe
Pasche Marie-Joelle
Savona Jacques
Le Amanda T.
Lucent Technologies - Inc.
LandOfFree
Method for making a call in a multiple bit-rate channel... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for making a call in a multiple bit-rate channel..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for making a call in a multiple bit-rate channel... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3052867