Multiplex communications – Communication techniques for information carried in plural... – Combining or distributing information via time channels
Patent
1996-08-21
1998-01-06
Kizou, Hassan
Multiplex communications
Communication techniques for information carried in plural...
Combining or distributing information via time channels
370508, 375356, H04J 306, H04L 1246
Patent
active
057062919
DESCRIPTION:
BRIEF SUMMARY
This application claims benefit of international application PCT/FI95/00096, filed Feb. 23, 1995.
BACKGROUND OF THE INVENTION
The present invention relates to a method for connecting a system utilizing message-based synchronization with an external system, and a network arrangement according to the preamble of the appended claim 8.
An external system typically uses a synchronization method different from that of a system utilizing message-based synchronization, but in principle, an external system can also use message-based synchronization, as will be described later.
As used in the text below, the term node refers to a junction point between transmission lines in a system. A node may be any device or equipment capable of affecting clock synchronization, such as a branching or cross-connection means.
Nodes in a system utilizing message-based synchronization are interconnected by transmission lines which the nodes use for data transmission. These lines also forward the clock frequency of the transmitting party to the receiving party. Each node selects the frequency of a signal from a neighbouring node, the frequency of its own internal clock source or a frequency applied to the node via a separate synchronization input from an external clock source as the source of its own clock frequency. In order that all nodes in the system will operate at the same clock frequency, one usually attempts to make the system to synchronize itself with a single clock source called a master source. All system nodes connected directly to the selected master source are thus synchronized with the master source, while nodes connected to the nodes adjacent to the master source but not directly connected to the master source are synchronized with these adjacent nodes. Accordingly, each node at a greater distance from the master source synchronizes itself with a node one node spacing closer to the master source.
In order that the above-described synchronization hierarchy can be established within the system, the system nodes interchange synchronization messages. These messages contain information by means of which individual nodes are able to select a timing source. The system nodes are prioritised and the system tends to synchronize itself with the clock frequency of a node having the highest level of priority. Normally each priority level is assigned to a single system node. Synchronization messages normally contain information about the origin of the clock frequency of the node transmitting the message and the priority of the node as well as a value describing the quality of the clock signal. Accordingly, a neighbouring node clock frequency which originates from a desired node and which is of the highest quality can be selected by an individual node as the source of its own clock frequency. At the system start-up each node selects its own internal clock source as the source of its clock frequency as it has not yet processed any incoming synchronization messages. After the node has processed the first incoming synchronization messages, it selects the clock frequency of a neighbouring node having the highest level of priority as the source of its clock frequency. After all messages have been distributed over the system and the system has achieved a stable state as far as synchronization is concerned, the system has been synchronized hierarchically with the clock frequency of the master source.
FIG. 1 shows a system MS utilizing message-based synchronization in a stable situation. Priorities assigned to the nodes are indicated by numbers within the circles representing the nodes. The smaller the number, the higher the priority of the node. Synchronization messages transmitted by a node n (n=1 . . . 6) are indicated by the reference MSGn. Synchronization messages transmitted by different nodes usually differ from each other and depend on the applied message-based synchronization method. The distribution of the clock frequency from the master clock (node 1) to the other system nodes is illustrated by solid lines. Internodal connecti
REFERENCES:
patent: 2986723 (1961-05-01), Darwin et al.
patent: 4709347 (1987-11-01), Kirk
patent: 4737850 (1988-04-01), Maisel et al.
patent: 4837850 (1989-06-01), Maisel et al.
patent: 4860287 (1989-08-01), Kelly
patent: 4939753 (1990-07-01), Olson
patent: 5184347 (1993-02-01), Farwell et al.
patent: 5384563 (1995-01-01), Massey
patent: 5550873 (1996-08-01), Dolev et al.
patent: 5594739 (1997-01-01), Lemieux
IBM Technical Disclosure Bulletin, vol. 25, No. 11B, Apr. 1983, LS. Rogers, "Clock Source Selection Method in Distributed Communication System Networks", pp. 6293-6298.
CCITT G.703, 1991.
CCITT G.704, 1991.
ITU-T Recommunication G.708, 1993.
ITU-T Recommunication G.709, 1993.
Kainulainen Jukka
Peltomaki Arto
Bnimoussa A.
Kizou Hassan
Nokia Telecommunications Oy
LandOfFree
Method and apparatus for connecting two messaging systems having does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for connecting two messaging systems having, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for connecting two messaging systems having will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2335763