Browse Prior Art Database

Dynamic Slot Assignment in TDM Frames

IP.com Disclosure Number: IPCOM000039218D
Original Publication Date: 1987-May-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 4 page(s) / 55K

Publishing Venue

IBM

Related People

Baratz, AE: AUTHOR [+4]

Abstract

In this article mechanisms for the dynamic control of slots in a TDM frame are presented. All proposed hybrid switching schemes have a single TDM frame with some slots in the TDM frame assigned to voice circuits, and other slots to data. The assignments will change when voice calls begin and end and, in systems where silence periods in (Image Omitted) voice are exploited to send data or to permit additional voice calls, these changes will be much more frequent. Thus, a mechanism that permits dynamic assignment of TDM slots is a fundamental building block in any hybrid switching system. Only when such a mechanism is in place can additional controls on the portion of the frame allocated to voice (e.g., the infamous "movable boundary" scheme) be implemented. The model that we assume is the following.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 45% of the total text.

Page 1 of 4

Dynamic Slot Assignment in TDM Frames

In this article mechanisms for the dynamic control of slots in a TDM frame are presented. All proposed hybrid switching schemes have a single TDM frame with some slots in the TDM frame assigned to voice circuits, and other slots to data. The assignments will change when voice calls begin and end and, in systems where silence periods in

(Image Omitted)

voice are exploited to send data or to permit additional voice calls, these changes will be much more frequent. Thus, a mechanism that permits dynamic assignment of TDM slots is a fundamental building block in any hybrid switching system.

Only when such a mechanism is in place can additional controls on the portion of the frame allocated to voice (e.g., the infamous "movable boundary" scheme) be implemented. The model that we assume is the following. Transmissions over a link occur in the form of TDM frames. Each frame is divided into several slot, each of several bits (typically 1 byte) in duration. We shall assign the slots addresses according to their position in the frame. Voice is transmitted over the frame in the form of circuits, i.e., each connection (identified by a unique logical connection number) has a fixed slot assigned to it in each frame. Data is transmitted in the form of packets and does not have such a fixed assignment. A link connects together a transmitter and a receiver. The transmitter is assumed to know the assignment of slots and the objective of our slot assignment mechanism is to enable the transmitter to inform the receiver of the assignment, thereby ensuring that the two end points of a link are in synchronization. In addition to knowing which slots are being used for data and which for voice, for the voice slots the receiver must know the mapping from the physical slots to the logical connection numbers. We now present some mechanisms for dynamic control of voice and data slots in a TDM frame. In the most basic mechanism, we reserve, in each TDM frame, one slot for link control. This slot is used in the following way. Each slot in the frame is assigned an address. Whenever a slot changes its type (from voice to data, data to voice, or from one voice call to another) the address of the slot is placed in the control slot, together with an extra bit (the V/D bit) indicating if the slot is now voice or data. The frame structure is depicted in Fig. 1. If the slot is being assigned to voice, the logical connection number of the voice call is placed in the slot that is being changed. The use of the frame structure to assign a slot to voice is shown in Fig. 3. This link-signalling system provides a mechanism for controlling the boundary between voice and data. In addition, it provides a mechanism for performing multi-hop TASI. There are some drawbacks with the basic mechanism. For example, the mechanism only permits a single change in any frame. This is not regarded as a significant problem as typical frames are about a hund...