October 15, 2014

Centralized vs Distributed Industrial Communications

To assess the role of distributed systems in modern industrial telecom, first of all, it is necessary to start out from the key requirements imposed to these systems in general.

The first one is a high level of reliability of the system. It means that its service life shall be decades. In this case, the system can be in the standby mode (preset readiness) if there are no emergency or out-of-schedule circumstances. But, in case of the emergency situation, the system shall be immediately activated. The reliability of industrial communication system guarantees that it will help saving human lives at the proper moment.

The second requirement is the speed of the system response – the possibility of the call initiator to contact immediately one or a group of subscribers. The connection time is the most vital in case of emergency situations when every second counts.

Differences between Distributed and Centralized Systems

1. Centralized industrial communication system as the standard telephony system is based on the central exchange equipment where configuration data are kept. Actually, it is the single point of failure. In case of its failure, the whole system will be broken down and won’t be able to provide functioning of separate sectors.

The distributed system is based on autonomous terminal devices. In other words, the network configuration is stored at each terminal device and there is no single point of failure. That is why in case of one device breaking down, all other devices continue working which increases the system survivability.

2. As for redundancy, it is provided in the centralized as well as in distributed communication system. But in case of the first type, the central exchange equipment is redundant; in the second case, usually the terminal equipment is redundant. It is worth noting that the distributed communication system architecture imposes high requirements to terminal devices performance as they are directly involved in the provided services procedure (this factor eventually increases their cost). However, taking into account the exchange equipment price, the expenses on the centralized system redundancy are usually higher than the terminal devices cost (even with regard to their increased price).



3. One more difference is the speed of response. The protocols, which are, as a rule, used in centralized communication systems, establish the p2p session connection (SIP). In other words, there is no preinstalled communication channel and it is necessary to initiate running of the session with the terminal subscriber immediately before data packets transmission that is why it causes a delay. In the distributed system, in particular, in Armtel system, simple protocols are used: multicast addressing of IP-packets which allows increasing the speed of the network response and of the subscriber call (or a group of subscribers).

Choosing Industrial Communication System

Today there is no decisive answer to the question which network architecture is better. Everything depends on the enterprise requirements and conditions of the system use. For example, the central exchange equipment shall be installed in comfortable conditions for the ease of its maintenance. At the same time, the distributed communication system is based on the system of independent clusters and doesn’t require much space for the exchange equipment storage.

In general, it is more reasonable to use the distributed communication system in transportation industry which has extensive sites. Combining Wi-Fi, optic and DSL technologies, it is possible to find flexible technical solutions while building industrial communication system, in one case or another. But the net result is that the system choosing depends on particular conditions; moreover, there can be integrated solutions where the distributed and centralized architectures are combined in the single network.

Development Outlook

As for the industrial communication systems evolution, the both variants have their own perspectives. Rapid development of centralized SIP-systems in industrial telecom is the next step forward for centralized solutions but at the IP level.

In reference to the decentralized systems, their future development is connected with cloud distributed technologies, from our point of view. There is such a term as distribution of computational power to separate devices. The result of such approach is a cloud service the computational power for which can be distributed within the network; it helps avoid concentrating of the whole configuration data in one place. These technologies have been already used in non-industrial sectors, so, sooner or later, they will be applied to industrial communication as well. However, the rate of development in this direction is highly dependent on the development of protecting data methods in the global informatization.

See also:
Armtel distributed IPN system
Armtel centralized DCN system
Speech Intelligibility In Industrial Communication