System and device for, and method of, detecting, characterizing, and mitigating deterministic distortion in a communications network

Claim 3

The method of claim 1 wherein the window of received signals has a length of twenty-four octets, and wherein the analyzing step determines whether the backbone network affects transmitted octets at a periodicity from the set of six, twelve, and twenty-four.

Claim 4

The method of claim 2 wherein the analyzing step determines whether the PSTN has forced to zero a least significant bit of an octet received by the line interface.

Claim 5

The method of claim 2 wherein the analyzing step determines whether the PSTN has forced to one a least significant bit of an octet received by the line interface.

Claim 6

The method of claim 2 wherein the analyzing step determines whether the PSTN has affected a least significant bit of an octet received by the line interface by setting the bit's value randomly from the set of zero and one.

Claim 7

The method of claim 1 wherein the PSTN has an octet signal constellation of 255 signal points and wherein the causing step uses no more than four octet signal points to form the transmitted sequence, the four signal points being chosen symmetrically around the octet signal constellation's origin, with two of the octets having a least significant bit equal to zero and two of the octets having a least significant bit equal to one.

Claim 8

The method of claim 6 wherein the window of baseband signals is twenty-four signals, corresponding to twenty-four octet intervals in an octet window, and wherein the causing step transmits a sufficient number of octets to allow the analyzing step to analyze multiple windows of baseband signals, and wherein the analyzing step uses an eight point constellation of baseband signal points, with a first set of four signal points being baseband signal analogies of the four octet signal points and with a second set of four signal points being baseband signal analogies to the four octet signal points, but with the least significant bit of each signal point inverted.

Claim 9

The method of claim 7 wherein the causing step transmits from the four point constellation an octet sequence to the PSTN in which the least significant bit of octets sent for each octet interval is known to vary within the time necessary to send the sufficient number of octets, and wherein the analyzing step determines for each octet interval in a window whether that interval is affected in a constant manner by finding that the received baseband signals points correspond to the line interface receiving octets with a constant least significant bit.

Claim 10

The method of claim 8 wherein, if the analyzing step fails to find that an octet interval in a window is affected in a constant manner, the analyzing step includes a step of distinguishing between the octet interval being not affected by the PSTN and the octet interval being affected by the PSTN altering a least significant bit of the octet in that interval by randomly setting the least significant bit to a value from the set of zero and one.

Claim 11

The method of claim 9 wherein the distinguishing step includes sending from the four point constellation an octet sequence to the PSTN in which the least significant bit of octets sent for each octet interval is known to remain constant, and wherein for each octet interval determining whether that interval is affected in a random manner by finding that the received baseband signals points correspond to the line interface receiving octets with a varying least significant bit.

Claim 12

The method of claim 8 wherein the causing step sends a known sequence of octets from the octet signal constellation, and wherein the analyzing step has knowledge of the known sequence and analyzes the received octets using a two state trellis in which one state corresponds to an RBS affected received octet and the other state corresponds to an unaffected received octet.

Claim 13

A digital adaptor and analog adaptor combination for communicating on a PSTN having a backbone network, a line interface for receiving octets from the backbone and for sending baseband signals representative of the received octets on a local loop and for receiving analog signals on the local loop and for sending octets representative of the analog signal on the backbone, wherein the PSTN is affected by robbed bit signaling, and wherein the digital adaptor is couplable to the backbone and the analog adaptor is couplable to the local loop, the analog adaptor comprising first logic for causing a time varying signal to be transmitted on the local loop; and second logic for causing a constant signal to be transmitted on the local loop; and wherein the digital adaptor comprises third logic, cooperating with the first logic, for analyzing octets received by the digital adaptor from the backbone to determine the distribution of octets having an LSB equal to zero and one; fourth logic, cooperating with the second logic, for analyzing octets received by the digital adaptor from the backbone to determine the distribution of octets having an LSB equal to zero and one; and fifth logic, cooperating with the third and the fourth logic, for characterizing an octet window, having octet intervals, in which each interval is characterized as being one of affected by no robbed bit signaling, affected by robbed bit signaling that forces a least significant bit of octets in that interval to a zero, affected by robbed bit signaling that forces a least significant bit of octets in that interval to a one, and affected by robbed bit signaling that forces a least significant bit of octets in that interval to a randomly selected value from one and zero.

Claim 14

A digital adaptor and analog adaptor combination for communicating on a PSTN having a backbone network, a line interface for receiving octets from the backbone and for sending baseband signals representative of the received octets on a local loop and for receiving analog signals on the local loop and for sending octets representative of the analog signal on the backbone, wherein the PSTN is affected by robbed bit signaling, and wherein the digital adaptor is couplable to the backbone and the analog adaptor is couplable to the local loop, the analog adaptor comprising first logic for causing a time varying signal to be transmitted on the local loop; and second logic for causing a constant signal to be transmitted on the local loop; and wherein the digital adaptor comprises third logic, cooperating with the first logic, for analyzing octets received by the digital adaptor from the backbone to determine the distribution of octets having an LSB equal to zero and one; fourth logic, cooperating with the second logic, for analyzing octets received by the digital adaptor from the backbone to determine the distribution of octets having an LSB equal to zero and one; and fifth logic, cooperating with the third and the fourth logic, for characterizing an octet window, having octet intervals, in which each interval is characterized as being one of affected by no robbed bit signaling, affected by robbed bit signaling that forces a least significant bit of octets in that interval to a zero, affected by robbed bit signaling that forces a least significant bit of octets in that interval to a one, and affected by robbed bit signaling that forces a least significant bit of octets in that interval to a randomly selected value from one and zero.

Claim 15

A digital adaptor and analog adaptor combination for communicating on a PSTN having a backbone network, a line interface for receiving octets from the backbone and for sending baseband signals representative of the received octets on a local loop and for receiving analog signals on the local loop and for sending octets representative of the analog signal on the backbone, wherein the PSTN is affected by robbed bit signaling, and wherein the digital adaptor is couplable to the backbone and the analog adaptor is couplable to the local loop, the digital adaptor comprising first logic for causing an octet sequence to be transmitted on the backbone wherein the sequence includes octets that have their least significant bits vary between a zero and a one; and second logic for causing an octet sequence to be transmitted on the backbone wherein the sequence includes octets having a constant value for their least significant bit; and wherein the analog adaptor comprises third logic, cooperating with the first logic, for analyzing baseband signals received by the analog adaptor from the local loop to determine the distribution of baseband signals caused by octets having an LSB equal to zero and one; fourth logic, cooperating with the second logic, for analyzing baseband signals received by the analog adaptor from the local loop to determine the distribution of baseband signals caused by octets having an LSB equal to zero and one; and fifth logic, cooperating with the third and the fourth logic, for characterizing an octet window, having octet intervals, in which each interval is characterized as being one of affected by no robbed bit signaling, affected by robbed bit signaling that forces a least significant bit of octets in that interval to a zero, affected by robbed bit signaling that forces a least significant bit of octets in that interval to a one, and affected by robbed bit signaling that forces a least significant bit of octets in that interval to a randomly selected value from one and zero.

Claim 16

A digital adaptor and analog adaptor combination for communicating on a PSTN having a backbone network, a line interface for receiving octets from the backbone and for sending baseband signals representative of the received octets on a local loop and for receiving analog signals on the local loop and for sending octets representative of the analog signal on the backbone, wherein the PSTN is affected by robbed bit signaling, and wherein the digital adaptor is couplable to the backbone and the analog adaptor is couplable to the local loop, the digital adaptor comprising first logic for causing an octet sequence to be transmitted on the backbone wherein the sequence includes octets that have their least significant bits vary between a zero and a one; and second logic for causing an octet sequence to be transmitted on the backbone wherein the sequence includes octets having a constant value for their least significant bit; and wherein the analog adaptor comprises third logic, cooperating with the first logic, for analyzing baseband signals received by the analog adaptor from the local loop to determine the distribution of baseband signals caused by octets having an LSB equal to zero and one; fourth logic, cooperating with the second logic, for analyzing baseband signals received by the analog adaptor from the local loop to determine the distribution of baseband signals caused by octets having an LSB equal to zero and one; and fifth logic, cooperating with the third and the fourth logic, for characterizing an octet window, having octet intervals, in which each interval is characterized as being one of affected by no robbed bit signaling, affected by robbed bit signaling that forces a least significant bit of octets in that interval to a zero, affected by robbed bit signaling that forces a least significant bit of octets in that interval to a one, and affected by robbed bit signaling that forces a least significant bit of octets in that interval to a randomly selected value from one and zero.

Claim 17

An analog adaptor for communicating on a PSTN having a backbone network, a line interface for receiving octets from the backbone and for sending baseband signals representative of the received octets on a local loop and for receiving analog signals on the local loop and for sending octets representative of the analog signal on the backbone, wherein the PSTN is affected by robbed bit signaling which alters the least significant bits of octets transmitted on the backbone, and wherein the analog adaptor is couplable to the local loop, the analog adaptor comprising first logic for analyzing baseband signals received by the analog adaptor from the local loop to determine the distribution of baseband signals caused by octets having an LSB equal to zero and one; second logic for causing the PSTN to send an octet sequence into the backbone in which least significant bits of the octets vary; third logic for causing the PSTN to send an octet sequence into the backbone in which least significant bits of the octets remain constant; fourth logic, cooperating with the first, second, and third logic, for analyzing the received baseband signals and characterizing an octet window, having octet intervals, in which each interval is characterized as being one of affected by no robbed bit signaling, affected by robbed bit signaling that forces a least significant bit of octets in that interval to a zero, affected by robbed bit signaling that forces a least significant bit of octets in that interval to a one, and affected by robbed bit signaling that forces a least significant bit of octets in that interval to a randomly selected value from one and zero.

Claim 18

An analog adaptor for communicating on a PSTN having a backbone network, a line interface for receiving octets from the backbone and for sending baseband signals representative of the received octets on a local loop and for receiving analog signals on the local loop and for sending octets representative of the analog signal on the backbone, wherein the PSTN is affected by robbed bit signaling which alters the least significant bits of octets transmitted on the backbone, and wherein the analog adaptor is couplable to the local loop, the analog adaptor comprising first logic for analyzing baseband signals received by the analog adaptor from the local loop to determine the distribution of baseband signals caused by octets having an LSB equal to zero and one; second logic for causing the PSTN to send an octet sequence into the backbone in which least significant bits of the octets vary; third logic for causing the PSTN to send an octet sequence into the backbone in which least significant bits of the octets remain constant; fourth logic, cooperating with the first, second, and third logic, for analyzing the received baseband signals and characterizing an octet window, having octet intervals, in which each interval is characterized as being one of affected by no robbed bit signaling, affected by robbed bit signaling that forces a least significant bit of octets in that interval to a zero, affected by robbed bit signaling that forces a least significant bit of octets in that interval to a one, and affected by robbed bit signaling that forces a least significant bit of octets in that interval to a randomly selected value from one and zero.

Claim 21

The method of claim 15 wherein the step of examining the octets in an octet interval to determine whether the octet interval is affected by the constant form of deterministic distortion comprises: determining whether a least significant bit of each of the examined octets is equal to zero.

Claim 22

The method of claim 15 wherein the step of examining the octets in an octet interval to determine whether the octet interval is affected by the constant form of deterministic distortion comprises: determining whether a least significant bit of each of the examined octets is equal to one.

Claim 23

The method of claim 15 further comprising the steps of: causing a substantially non-time-varying analog test signal to be transmitted on the local loop; and examining the octets in the octet interval to determine whether the octet interval is affected by a random form of deterministic distortion.

Claim 24

The method of claim 18 wherein the step of examining the octets in the octet interval to determine whether the octet interval is affected by the random form of deterministic distortion comprises: determining whether a substantial number of the examined octets have a least significant bit equal to zero and a substantial number of the examined octets have a least significant bit equal to one.