System and method for a robust preamble and transmission delimiting in a switched-carrier transceiver

Abstract

A method and system for robust delimiting of messages in switched-carrier operation in which a preamble precedes each message. The preamble comprises symbols transmitted at a rate lower than that of the following data. The lower rate significantly increases the probability that decoding of the preamble symbols will be error-free. Communication line control information can be included in the preamble, thereby ensuring that line control information is reliably transferred over the channel. The preamble's first symbol can be transmitted at the lower symbol rate and at an increased power level, thereby reliably delimiting the beginning of a transmission. The end of the message can be reliably delimited by sending the first symbol which contains only bits from a next cell of information at a lower symbol rate, and including an extra bit in that symbol. The extra bfit can indicate to a receiver when the last cell of information begins.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation of Application Ser. No. 09 / 637,185, filed Aug. 11, 2000, which claims the benefit of U.S. Provisional Application No. 60 / 150,436 filed Aug. 24, 1999. These applications are entirely incorporated herein by reference.TECHNICAL FIELD [0002] The present invention relates generally to communications systems, and more particularly, to a system and method for a robust preamble and transmission delimiting in a switched-carrier transceiver. BACKGROUND OF THE INVENTION [0003] Data communication typically occurs as the transfer of information from one communication device to another. This is typically accomplished by the use of a modem located at each communication endpoint. In the past, the term modem denoted a piece of communication apparatus that performed a modulation and demodulation function, hence the term “modem”. Today, the term modem is typically used to denote any piece of communication apparatus that ...

AI Technical Summary

Benefits of technology

[0009] The present invention provides an improved system and method for robustly delimiting a message transmission in switched-carrier communication systems. The invention provides a method and system for transmission of a message preamble in which transmission of the preamble is more robust than the data. In this manner, the beginning and end of a transmission can be robustly delimited and channel control information can be reliably conveyed to a receiving transceiver.

[0010] The system of the present invention uses a novel header application, which enables the transport of ATM, or any other data, efficiently and economically over a communications channel, such as a DSL communications channel.

Problems solved by technology

However, even the slowest DSL communications devices achieve data rates far in excess of conventional point-to-point modems.

Because the most efficient signal constellation encoding cannot allocate signal space to silence, it is impractical to reliably discriminate silence from a signal when analyzing only a single symbol encoding an arbitrary data value.

Unfortunately, discrimination of special symbols has the same error threshold as does decoding of data.

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