Multiplex communications – Channel assignment techniques – Combining or distributing information via time channels...
Reexamination Certificate
1999-07-19
2004-10-19
Ton, Dang (Department: 2666)
Multiplex communications
Channel assignment techniques
Combining or distributing information via time channels...
C370S478000
Reexamination Certificate
active
06807188
ABSTRACT:
TECHNICAL FIELD
This invention is related to Time Division Multiple Access (TDMA) communications and, more particularly, to ranging in the transmission of TDMA signals.
BACKGROUND OF THE INVENTION
In TDMA transmission of signals it is required that all the individual signal components of the TDMA transmission have equal transmission delay. Consequently, a delay interval must be determined for each signal included in the TDMA transmission which when added to the individual signal yields a common loop delay for that signal equal to individual loop delay of the other TDMA signal components. To determine the particular delay to be added to each of the TDMA signal components, a so-called “ranging” procedure is effected when an equipment unit which will transmit the signal is installed, relocated, or otherwise has a disruption in service. A popular prior known ranging procedure is so-called “in-band ranging”, where in-band ranging messages are employed to effect the ranging procedure. Unfortunately, the use of the in-band ranging messages requires that the transmission bandwidth be temporarily interrupted and used for transmitting the in-band ranging messages. Thus, in-band ranging is an intrusive procedure that interferes with normal bandwidth use. Additionally, it is necessary to schedule when the in-band ranging is to be done. Indeed, as the rate at which in-band ranging is scheduled is increased, more and more transmission bandwidth is lost. This is extremely undesirable because the bandwidth cannot be used for other purposes, for example, constant bit rate transmission.
SUMMARY OF THE INVENTION
These and other problems and limitations of the prior known in-band ranging procedure are addressed by employing a non-intrusive out-of-band ranging technique. Ranging is automatically initiated at a customer premises equipment unit when the equipment is installed, when power is restored after a power failure or interruption, upon verification of the equipment, upon reconnection after a disconnection of the equipment or the like. To this end, an out-of-band tone is employed that is automatically transmitted when the customer premises equipment that transmits the TDMA signal is powered ON, or transmitted in response to a specific command generated locally or remotely.
Specifically, when ranging is being effected the customer premises equipment generates and transmits the out-of-band ranging tone until a message is received from a remote terminal indicating that the transmission of the ranging tone be terminated. The loop delay being determined is the delay interval between transmission of the termination message and detection that transmission of the ranging tone has terminated. Then, a message is transmitted to the customer premises equipment that contains the ranging delay interval that is to be used in all future transmissions to the remote terminal.
In one embodiment of the invention, the customer premises equipment automatically switches to an idle standby state when the remote terminal removes its upstream transmission slot. In the standby state, the customer premises equipment is still capable of receiving data and is periodically polled by the remote terminal assigning it an upstream transmission slot. If a customer premises equipment in the standby state is not polled during a predetermined interval, it automatically switches to a verification state.
Additionally, if the customer premises equipment does not respond when polled, the remote terminal transmits it a message putting it in the verification state. If a polled customer premises equipment responds with an out-of-band tone, which indicates that it is in the verification state, the remote terminal treats it as though it is verifying ranging. If the out-of-band tone is properly aligned, the customer premises equipment is switched to an active state.
An advantage of polling customer premises equipment in the idle standby state is that it enables system operations to distinguish between an idle customer premises equipment, power outages, disconnected or otherwise removed customer premises equipment.
REFERENCES:
patent: 6307868 (2001-10-01), Rakib et al.
patent: 6356555 (2002-03-01), Rakib et al.
patent: 6507592 (2003-01-01), Hurvig et al.
patent: 6665308 (2003-12-01), Rakib et al.
Blahut Donal E.
Magill Peter D.
Ton Dang
Tran Phuc
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