Browse Prior Art Database

Digital Telephony Bit Shape Generator

IP.com Disclosure Number: IPCOM000012717D
Publication Date: 2003-May-21
Document File: 4 page(s) / 644K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method using a single set of logic (i.e. logic gates or software) to support receiving and transmitting bits using an infinite number of digital telephone encoding schemes. The disclosed method works without the need to change the core logic.

This text was extracted from a Microsoft Word document.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 42% of the total text.

 

Digital Telephony Bit Shape Generator

Disclosed is a method using a single set of logic (i.e. logic gates or software) to support receiving and transmitting bits using an infinite number of digital telephone encoding schemes. The disclosed method works without the need to change the core logic.

Background

Figure 1 shows a typical sequence of bits, and the associated signal used to generate the data representing those bits using AMI encoding. A pulse alternating between a positive level and a negative level is represented by the 1’s. A zero level is represented by the 0’s. A “1” pulse with the same polarity as the previous one represents a bipolar violation. Figure 2 shows the same bits, but encoded using a diphase encoding scheme. Here, a “0” is represented by a rising edge in the center of the bit period. A “1” is represented by a falling edge. A 3rd state (often an idle state) is represented by the lack of an edge at the center of the bit period, and represented by an “N” in the figure. Finally, Figure 3 shows an example of Coded Mark Inversion. In this scheme, 1’s are represented by an alternating high or low level (similar to AMI), and 0’s are represented by a rising edge in the center of the bit period. This scheme may also use a 3rd state for an idle or error condition.

As shown in these examples, the signals have three levels (High, Low, and Zero). To generate these signals, the physical hardware uses two outputs. Positive and negative signals, as shown in Figure 4 are controlled by the logic to generate the desired waveform.

Currently, only specific logic designed to generate fixed pulse shapes is used. The only configurability is altering the pulse width time and relative location (in the case of AMI). A different set of logic is used to generate data for each of the supported encoding schemes. Currently, only two encoding schemes are supported.

General Description

The disclosed method generates the positive and negative streams combined by the physical hardware to create a signal that can be used by any encoding scheme. It does this by configuring the logic based on the rules for an encoding scheme.

The general idea is that the pulse generator logic can build pulses based on assigned levels, during different intervals within a bit period. The times and the levels are configured by software, and the pulse generator logic creates the pulse based on these programmed rules. Figure 5 shows a complete set of rules that define all the bit shapes used in AMI encoding. In this case, there are 3 possible shapes: a “zero” time, followed by a “high” time, followed by a “zero” time (shape B), a “zero” – “low” – “zero” (shape C), and an all “zero” time (shape A). At configuration time, the software configures the Number of Shapes = 3 and the number of Time Divisions = 3 as shown in Figure 5. Some encoding schemes such as NRZ use a single level for the entire bit time; thus in this case, Time...