US 5,644,573 A · Methods for coordinating upstream discrete multi-tone data transmissions

Abstract

A variety of methods of coordinating communications between a plurality of remote units and a central unit to facilitate communications using a frame based discrete multi-tone (DMT) transmission scheme am disclosed. In one aspect of the invention, synchronized quiet times are periodically provided in the upstream communication stream. The synchronized quiet times are used to handle a variety of control type functions such as synchronization of new remote units, transmission channel quality checking and handling data transfer requests. The information received is used to facilitate the dynamic allocation of bandwidth during use. In another aspect, a data request signal may be used to indicate either a desire to transmit at a particular data rate or a desire to transmit a particular amount of information. In the former case, the central unit allocates sufficient sub-channels to the remote unit to facilitate transmission at a requested data rate that is specified in the data request information. In the latter case, the central unit allocates one or more sub-channels for an amount of time sufficient to transmit an amount information that is specified in the data request information.

Claims24

Dependent claims

In a bi-directional data transmission system that facilitates communications between a plurality of remote units and a central unit on a common bi-directional transmission medium and using a frame based discrete multi-tone transmission scheme that has a multiplicity of discrete sub-channels for facilitating upstream communications between the plurality of remote units and the central unit, a method of synchronizing frames transmitted from a selected first remote unit to the central unit with frames transmitted from other remote units to the central unit, such that frame boundaries of the flames transmitted from the first remote unit arrive at the central unit substantially in synchrony with frame boundaries of frames transmitted from the other remote units, the method comprising the steps of:

periodically providing synchronized quiet times on the multiplicity of discrete sub-channels provided for facilitating upstream communications in accordance with the discrete multi-tone transmission scheme on the common bi-directional transmission medium;
and
transmitting an unprompted broad band initialization signal on the common bi-directional transmission medium from the first remote unit to the central unit during a first selected synchronized quiet time, the broad band initialization signal including a plurality of initialization signals transmitted over distinct sub-channels, each of the sub-channels carrying data independently of other sub-channels on the common hi-directional transmission medium and independently of the other remote units, the broad band initialization signal having a frame boundary.

Digital Subscriber Line data transmissions system that facilitates communications to and from a plurality of remote units and a central unit using a frame based discrete multi-tone transmission scheme on a common bi-directional transmission medium, the discrete multi-tone transmission scheme having a first multiplicity of discrete sub-channels for facilitating upstream communications from the plurality of remote units to the central unit and a second multiplicity of discrete sub-channels for facilitating downstream communications from the central unit to the plurality of remote units, a method of synchronizing frames transmitted from a selected first remote unit to the central unit with frames transmitted from other remote units to the central unit on different ones of the first multiplicity of discrete sub-channels such that frame boundaries of the frames transmitted from the first remote unit arrive at the central unit substantially in synchrony with frame boundaries of frames transmitted from the other remote units, the method comprising the steps of:

periodically providing synchronized quiet limes on the first multiplicity of discrete sub-channels provided for facilitating upstream communications;
and
when the first remote unit desires to establish communications with the central unit, said first remote unit monitors downstream communication broadcast by the central unit and substantially synchronizes a frame boundary of an unprompted broad band initalization signal with a frame timing marker carried in downstream signals received by remmote unit;
transmitting the unprompted broad band initialization signal on the common bi-directional transmission medium from the first remote unit to the central unit during a first selected synchronized quiet time;
and
receiving the initialization at the central unit and sending a synchronization signal from the central unit to the first remote unit, the synchronization signal having information indicative of a frame boundary shift required to better synchronize frame boundaries of signals sent by the first remote unit with frame boundaries of signals sent by other remote units that are communicating with the central unit;
and
shifting the boundary of the frames outputted by the first remote unit in response to the synchronization signal to better synchronize the frame boundaries of the frames outputted by the first remote unit with the frame boundaries of frames output by the other remote units that are currently communicating with the central unit, and
whereby the synchronization is arranged such that when fully synchronized, the frame boundaries from the various remotes will substantially coincide when they are received at the central unit.

6 more elements

Dependencies are inferred from the claim text.

Methods for coordinating upstream discrete multi-tone data transmissions

Life of this patent

Methods for coordinating upstream discrete multi-tone data transmissions

Life of this patent

Abstract

Claims24