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ENHANCED DLAN FAULT MONITOR WITH FULL REAL TIME DIAGNOSTICS

IP.com Disclosure Number: IPCOM000006469D
Original Publication Date: 1992-May-01
Included in the Prior Art Database: 2002-Jan-07
Document File: 3 page(s) / 150K

Publishing Venue

Motorola

Related People

Vijay Nadkarni: AUTHOR

Abstract

This invention offers a vastly improved protocol to monitor and diagnose faults, in a real time fashion, within the local area network that supports Smart Repeater trunked systems. By having all repeaters take turns in broadcasting their status, between adjacent Word Frame Interrupt synchronization pulses, every repeater in the network is kept abreast of problems as they occur. The protocol can handle broken cables as well as malfunc- tioning repeaters. With this invention, whenever a net- work fault occurs, all active. repeaters know instantly (within 23.3 m ) h s t e nature of the fault, its location, and the IDS of other repeaters that can be communicated to.

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MOTOROLA INC. Technical Developments Volume 15 May 1992

ENHANCED DLAN FAULT MONITOR WITH FULL REAL TIME DIAGNOSTICS

by Vijay Nadkarni

  This invention offers a vastly improved protocol to monitor and diagnose faults, in a real time fashion, within the local area network that supports Smart Repeater trunked systems. By having all repeaters take turns in broadcasting their status, between adjacent Word Frame Interrupt synchronization pulses, every repeater in the network is kept abreast of problems as they occur. The protocol can handle broken cables as well as malfunc- tioning repeaters. With this invention, whenever a net- work fault occurs, all active. repeaters know instantly (within 23.3 m ) h
s t e nature of the fault, its location, and the IDS of other repeaters that can be communicated to.

  The local area network in a Smart Repeater system, shown in Figure 1, consists of two primary sets of multi- drop links, the data bearing network (DLAN, for Data Local Area Network) and the synchronization network (carrying WFI, or word frame interrupt synchroniza- tion pulses). A Smart Repeater site needs to be able to handle faults on the local area network occurring due to inactive repeaters or to cable breaks.

With this protocol (Figure 2), the control channel repeater transmits WFI synchronization pulses at futed
23.3 ms interval on the WFI line. Immediately after it has delivered a pulse, it tristates its driver, and allows the other repeaters on the network to sequentially com- mence transmitting their status messages. Whenever it is a repeater's turn to transmit a message, that repeater enables its driver and transmits the 96 bit HDLC frame (the frame may have some additional bits for zero bit stuffing). After it has completed transmitting its status, it tristates its driver and allows the next repeater in the

sequence to transmit.

  The frames are short enough that even with all 39 repeaters transmitting status messages, the end of the last message will not run into the pending WFI pulse from the control channel. Moreover, all the repeaters have internal timers that allow them to know, with some accuracy, when to expect the next WFI pulse-this per- mits them to ready their WFI receivers for the next pulse, within a window of tolerance.

  When a fault does occur on the network, each repeater will either see or not see WFI. Also, each repeater will not see messages from one or more repeat- ers. Based on these occurrences, the repeaters will out- put appropriate status messages to all other repeaters. The collection of status messages received by each repeater will provide that repeater with sufficient information to diagnose the fault with a very high degree of accuracy. The repeater will then be able to reconfigure itselfwith the other repeaters that can still be communi- cated to, in a manner that will minim& down time.

  Figure 3 presents an example of the occurrence of a fault. Here,...