Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Control Technique for Time-Multiplexed Crossbar Networks

IP.com Disclosure Number: IPCOM000034746D
Original Publication Date: 1989-Apr-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 4 page(s) / 43K

Publishing Venue

IBM

Related People

Dias, DM: AUTHOR [+5]

Abstract

This article describes a simple routing technique for crossbar matrices which are used to switch circuits between several high bandwidth trunks. The trunks are slotted in time and a group of successive slots constitutes a frame. The number of circuits that can be multiplexed on the trunk is equal to the number of slots in a frame. The crossbar- matrix is time multiplexed (at the same rate as the input trunks). In each slot, it transfers information from the incoming trunks to the outgoing trunks. (Image Omitted) Slot interchangers are provided between the crossbar-matrix and each incoming trunk. Thus, if two or more calls which use the same slot on a different incoming trunk are to be switched to the same outgoing trunk, they can use different slots in the crossbar-matrix and on the desired outgoing trunk.

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 39% of the total text.

Page 1 of 4

Control Technique for Time-Multiplexed Crossbar Networks

This article describes a simple routing technique for crossbar matrices which are used to switch circuits between several high bandwidth trunks. The trunks are slotted in time and a group of successive slots constitutes a frame. The number of circuits that can be multiplexed on the trunk is equal to the number of slots in a frame. The crossbar- matrix is time multiplexed (at the same rate as the input trunks). In each slot, it transfers information from the incoming trunks to the outgoing trunks.

(Image Omitted)

Slot interchangers are provided between the crossbar-matrix and each incoming trunk. Thus, if two or more calls which use the same slot on a different incoming trunk are to be switched to the same outgoing trunk, they can use different slots in the crossbar-matrix and on the desired outgoing trunk. Slot interchangers are also provided between the crossbar-matrix and each outgoing trunk so that an incoming call can be switched to a desired unused slot on the requested outgoing trunk. The slot interchangers essentially permute the slots within a frame in time and can be viewed as a crossbar-switch in time. Then the switch-matrix, together with the slot interchangers, can be viewed as a three-stage Benes network, as shown in Fig. 1. The slot interchangers form the first and the third stage, and the crossbar-matrix forms the middle (second) stage (multiple copies shown since it is multiplexed in time). The above analogy helps one to understand some properties of the crossbar-matrices which are otherwise not obvious. Since it is known that the Benes network is rearrangeable and non-blocking, the crossbar must share the same property (i.e., to establish a new call, some existing calls must be rerouted). Furthermore, from the previous knowledge of strictly non-blocking Clos networks, one can infer that the cross-matrices can be made strictly non-blocking if they are multiplexed in time at twice the rate of multiplexing on input/output trunks. Furthermore, this analogy between Benes networks and crossbar- matrices will enable us to use the various control algorithms developed for Benes network in crossbar-matrices. In the state of the art, all cross-points are set by the central controller.

Therefore, the number of trunks allowed and the number of slots per trunk is limited by the performance of the controller. Furthermore, to establish a new call/circuit the central controller has to first search for the appropriate time slot. If the switching speed of the crossbar-matrix is equal to the switching speed of the trunks (i.e., the network resembles a Benes-type network), then some existing calls have to be rerouted by the central controller. The latter effort is far more time consuming than the former. However, in both cases, the speed of the central controller also limits the number of calls that can be handled by the crossbar. To overcome the above mentioned problems, the sl...