Browse Prior Art Database

Method for Converting TDM Data into Packets for Transport in a Fast Packet Switch

IP.com Disclosure Number: IPCOM000109533D
Original Publication Date: 1992-Sep-01
Included in the Prior Art Database: 2005-Mar-24
Document File: 9 page(s) / 450K

Publishing Venue

IBM

Related People

Reeve, TL: AUTHOR [+3]

Abstract

In a Fast-Packet Switch, there is a requirement for separating and combining multiple subchannels contained in TDM (time-division multiplexed) format prior to packet assembly and disassembly. These subchannels can be of varying bandwidths and the data bits for each subchannel are not restricted to being in the same octet within a frame, in contiguous octets within a frame, or even within the same frame. The subchannel configuration will be different from system to system, requiring that the solution be flexible.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 19% of the total text.

Method for Converting TDM Data into Packets for Transport in a Fast Packet Switch

       In a Fast-Packet Switch, there is a requirement for
separating and combining multiple subchannels contained in TDM
(time-division multiplexed) format prior to packet assembly and
disassembly.  These subchannels can be of varying bandwidths and the
data bits for each subchannel are not restricted to being in the same
octet within a frame, in contiguous octets within a frame, or even
within the same frame.  The subchannel configuration will be
different from system to system, requiring that the solution be
flexible.

      This problem is solved by individually mapping each bit to its
correct subchannel.  The bit mapping is programmable and can be
changed during operations, allowing maximum configuration
flexibility.  Every bit in the frame can be configured as a separate
subchannel.  There is no requirement for all bits in a subchannel to
be contiguous in the TDM bit stream.  All unused bits can be mapped
into a single unused subchannel.

      This design is made up of six main modules which are shown in
Fig. 1.  A microprocessor, microcontroller, or other controlling
hardware is required for implementation but its design and
specification is not within the scope of this design.  It will be
referred to as micro in this article.  The six main modules of the
design are:
      TDM Media Interface
      TDM Media Interface module provides the electrical and
mechanical connection to the TDM facility provided by the public
carrier service. It must handle error recovery, statistics gathering,
and other requirements placed on users of the public carrier network.
The requirements vary based upon the type of TDM facility and the
country in which it is used.  The TDM media interface can operate in
full-duplex or half-duplex mode.  In full-duplex mode, shown in Fig.
1, it takes the serial bit stream it receives from the TDM link and
sends it to the receive data control module.  It also takes the
serial bit stream it receives from the transmit data control module
and sends it out on the TDM link.  In half-duplex mode, shown in Fig.
"DETAIL", it is necessary to have two SCAT/Arbiter modules.  One TDM
media interface-SCAT (Subchannel Configuration Address Table)/arbiter
pair runs in receive mode and the other in transmit mode.
      Arbiter/SCAT (Subchannel Configuration Address Table)
      The arbiter/SCAT module controls how the subchannels are
mapped.  The arbiter controls which module has access to the SCAT.
The SCAT contains the bit map of the subchannels and can be
reconfigured during operation with minimal loss of data.  When the
TDM media interface is operating in half-duplex mode, it is necessary
to have two SCAT/Arbiter modules, one for receive and one for
transmit.
      Receive Data Control
      The Receive Data Control module takes the serial bit stream
from the TDM media interface module and the...