Multiplex communications – Communication techniques for information carried in plural... – Adaptive
Reexamination Certificate
1997-11-10
2001-04-10
Zimmerman, Mark (Department: 2671)
Multiplex communications
Communication techniques for information carried in plural...
Adaptive
C370S464000, C375S225000
Reexamination Certificate
active
06215793
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an initialisation protocol to be executed by a first transceiver and a second transceiver to negotiate a data rate for future data transmission over a communication link which is coupled between the first transceiver and the second transceiver. It is also directed to a transceiver adapted to perform this initialisation protocol.
BACKGROUND OF THE INVENTION
Such an initialisation protocol is already known in the art, e.g. from the communication between two Asymmetric Digital Subscriber Line (ADSL) modems operating in accordance with the specifications of the ANSI (American National Standards Institute, Inc.) Standard on ADSL, the approved version of which has the reference T1E1.413 and title “
Network and Customer Installation Interfaces, Asymmetric Digital Subscriber Line
(
ADSL
)
Metallic Interface”.
In the draft version of this standard published in April 1994, the initialisation protocol to be executed by an ADSL transceiver pair interconnected via a communication link, e.g. a twisted pair copper telephone line, is described in chapter 12, from page 83 to page 104. In view of the present invention, only a part of this initialisation protocol is relevant. More particularly, the part wherein the two communicating ADSL transceivers negotiate the future upstream and downstream data rates is to be considered. In FIG. 29 on page 83 of the above cited draft Standard Specification, this part is indicated by “Channel Analysis” and “Exchange”; The “Channel Analysis” procedure contains a first phase wherein the first ADSL transceiver, named the central office modem, transmits four optional upstream and downstream data rate values to the second ADSL transceiver, named the remote terminal modem. The second ADSL transceiver replies upon receipt of the just mentioned proposal by transmitting four optional upstream data rate values to the central office modem. These optional data rate values sent from transceiver
1
to transceiver
2
and vice versa, from transmitter
2
to transmitter
1
, are encapsulated in the so called C-RATES
1
and R-RATES
1
messages described in paragraph 12.6.2 on pages 92-93 and 12.7.4 on page 96 of the above mentioned draft Standard Specification respectively. The “Exchange” procedure in addition contains a third phase wherein the central office modem and remote terminal modem communicate to each other which one of the optional data rates they prefer to use. In a fourth phase which also forms part of the “Exchange” procedure of the ADSL initialisation protocol, the remote terminal modem transmits a so called R-B&G message to the central office modem. This message contains the bits and gains information for the carriers which will carry the discrete multi tone (DMT) symbols that will constitute the future communication between the ADSL transceivers. This bits and gains information can be seen as a confirmation of the selected data rate in the previous phase, since the downstream and upstream data rates for future transmission are completely determined thereby. A disadvantage of the above known initialisation protocol is that the final selected and confirmed upstream and downstream data rates can not differ from the four data rate values proposed in the first phase. These proposed data rate values are chosen rather arbitrarily and may all differ significantly from the optimal upstream and downstream data rates which depend on the communication link characteristics. In other words, the known initialisation protocol does not support adaptive data rates, i.e. data rates which are adapted to the capacity of the communication link between the two transceivers. The only way to adapt data rates is to restart the complete identification and initialisation process.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an initialisation protocol of the above known type, but which overcomes the above described drawback, i.e. which supports adaptation of data rates without restarting, i.e. without executing all previous identification and initialisation steps again.
This object is realised by an initialisation protocol to be executed by a first transceiver and a second transceiver to negotiate a data rate for future data transmission over a communication link which is coupled between the first transceiver and the second transceiver, the initialisation protocol containing a first phase wherein at least the first transceiver proposes a limited amount of data rate values for the data rate; a third phase wherein it is communicated which one of the data rate values is selected for the data rate; and a fourth phase wherein it is confirmed that the selected one of the data rate values will become the data rate for future transmission, wherein before the fourth phase is executed, the first transceiver or the second transceiver announces a new data rate proposal, whereupon the first phase is re-executed.
This object is also achieved by a transceiver adapted to transmit data via a communication link to a second transceiver, the transceiver including a line interface whereto information is applied to be transmitted over the communication link, the line interface being provided with at least one input terminal whereto the information is applied and an output terminal coupled to the communication link; a proposal generating means adapted to generate a message including a limited amount of data rate values for a data rate for future transmission between the transceiver and the second transceiver and to apply the message to an input of the line interface; a selection generating means adapted to generate a message to indicate which one of the data rate values is selected and to apply the message to an input of the line interface; a confirmation generating means adapted to generate a message to confirm which one of the data rate values will become the data rate for future transmission, and to apply the message to an input of the line interface; a data generating means coupled to an input of the line interface and adapted to apply data thereto to be transmitted by the line interface at the data rate selected and confirmed; and an initialisation control means, outputs of which are coupled to inputs of the proposal generating means, the selection generating means and the configuration generating means; the initialisation control means being adapted to control which one of the means whereof outputs are coupled to inputs of the initialisation means is allowed to apply a message to an input of the line interface; wherein the transceiver further includes: a proposal announcement generating means adapted to generate a message to announce a new data rate proposal and to apply the message to an input of the line interface; and further in that the initialisation control means is provided with an additional output coupled to an input of the proposal announcement generating means.
In this way, by allowing the transceivers to announce a new data rate proposal, and by formulating adapted optional data rate values in an additional execution of the first phase, the final selected and confirmed data rate may be better adapted to the communication link capacity than was possible by accepting any of the previously proposed data rate values during the fist execution of the first phase. Obviously, one of the transceivers may announce once more a new data rate proposal if the adopted data rate values included in the second proposal still cannot approximate the optimal data rate satisfactory.
In a particular implementation of the present initialisation protocol, the data rates proposed in the re-execution of the first phase may be chosen optimally.
Indeed, when the initialisation protocol contains a second phase wherein the capacity of the communication link, i.e. the highest transmission rate of the link, is measured, the transceivers have a good criterion to decide to announce a new proposal and a good tool to select the adapted proposed data rate values. If none of the first proposed data rate values approximates the highest supportable da
Gultekin Neil
Spruyt Paul Marie Pierre
Van Der Putten Frank Octaaf
Alcatel
Santiago Enrique L
Ware Fressola Van der Sluys & Adolphson LLP
Zimmerman Mark
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