1. Overview

The communication base stations of the telecommunications sector often undertake very important communication tasks. In order to ensure the normal and uninterrupted operation of various communication equipment, the requirements for the power supply system and environment are very high. With the development of the postal and telecommunications sector towards unmanned machine rooms, it has become an inevitable trend to realize automatic monitoring of power and environment. Compared with general buildings, the communication base stations of the telecommunications sector have many types of equipment, and the equipment is more specialized and complex, which brings greater difficulty to the implementation of the monitoring system. How to choose a reasonable system mode and monitoring technology according to the characteristics of the communication base station is a problem that users and system developers in the industry are very concerned about.

As we all know, automatic monitoring systems (or measurement and control systems) are developing in the direction of distribution and networking. The key to distributed monitoring systems lies in their networking technology, which is commonly known as fieldbus technology. At present, there are many fieldbus technologies coexisting and they have been applied to different degrees in different application fields. For example, in the field of building automation, the LonWorks bus technology launched by Echelon in the United States has been widely used and gradually became a de facto standard in the industry. In view of the fact that the power environment monitoring of communication base stations is a special kind of building monitoring, and the many characteristics and advantages of LonWorks technology itself, after many aspects of argumentation, we finally selected LonWorks as the field network technology of our company's power environment monitoring system. Let's take a look at how to use this new technology to build a power environment monitoring system for communication base stations through a system example.

2. System composition

Based on LonWorks technology, we successfully completed the Qibao Satellite Ground Communication Station Power and Environment Monitoring System Project for Shanghai Long Distance Telecommunications Bureau. The project requires real-time signal acquisition and partial operation control of high-voltage secondary circuits, capacitor compensation cabinets, low-voltage distribution cabinets, UPS, battery packs, special air conditioners, diesel generators and other objects in the communication station. Once abnormal data or status is found, an alarm will be issued immediately (screen prompts and sound alarms), and various events and operation information will be stored, queried at any time, and various reports will be generated according to user requirements.

The monitoring system consists of three parts: signal conversion subsystem, LonWorks acquisition control network, and upper monitoring PC subsystem. The relationship between each part is as follows:

The LonWorks field network in the system consists of three types of nodes:

1) Analog quantity acquisition node

It is mainly composed of NEURON chip, TP/FT-10 free topology transceiver, program memory, serial A/D chip, etc. It can complete the digital-to-analog conversion of 24 analog signals with a sampling resolution of 10 bits.

2) Switching quantity acquisition node

It is mainly composed of NEURON chip, TP/FT-10 free topology transceiver, program memory, shift register, etc. It can connect 24 switch inputs, and all signals are photoelectrically isolated.

3) Communication protocol conversion node

Secondary development was carried out based on ECHELON's programmable serial gateway PSG/2, converting the serial communication protocols of Sampsion diesel generators, Liebert special air conditioners, and battery monitors into LonTalk network protocols. In this way, various different intelligent devices can be connected to the LonWorks network to achieve the purpose of system integration.

All nodes in the system are connected by a pair of twisted-pair cables, using a free topology structure. The maximum distance between nodes can reach 500 meters, which can fully adapt to the situation in general communication base stations. If a longer distance connection is required, a bus topology structure (up to 2700 meters) can be used, or a repeater can be added.

In the upper PC part, the programmable serial gateway PSG/2 is used as the LonWorks network interface to convert the LonTalk protocol into serial communication and connect to the upper monitoring machine. In this way, the LonWorks network is integrated into the computer local area network (LAN) through the monitoring machine, and the TCP/IP network protocol is used on the LAN for higher-level system integration.

3. Conclusion

The implementation of the power and environment computer monitoring project of Qibao Satellite Communication Station proves that LonWorks technology is fully applicable in such applications and demonstrates a series of advantages:

1. Advanced network communication breaks through many limitations of traditional fieldbus

LonWorks introduces advanced computer LAN technology into the monitoring field, so that each acquisition control node on site has powerful network communication functions, which not only realizes peer-to-peer communication between nodes and two-way communication between upper and lower computers, but also enables each field node to spontaneously transmit alarm signals and acquisition results, realizing real-time acquisition in the true sense. The traditional field bus adopts the master/slave mode, that is, each node can only transmit information to the upper computer when the upper computer queries the node. When the number of nodes increases or some nodes fail or occupy the bus for a long time, the alarm signals and acquisition data of other nodes may be delayed or even lost, and the real-time and reliability cannot be guaranteed. The LonTalk network protocol adopted by LonWorks fundamentally solves the above problems, and through the improved CSMA (a collision and conflict detection method), it will not cause network paralysis when the network load is heavy.

At the same time, the use of LonWorks technology makes it easy to achieve on-site communication rates above 78 Kbps.

2. Flexible connection method and convenient system expansion

LonWorks technology can support various network topologies. In the project, we adopted a free connection method, that is, each node is connected to the nearest node without considering the relationship between them. As a result, it greatly facilitates the structural design and wiring construction of the system, and avoids the inevitable wiring waste in traditional bus wiring.

Another benefit of free topology is that system expansion becomes very convenient. When you need to add collection points, you only need to install the collection node in a nearby place, and then connect the node to another nearby node with two twisted pair cables. There is no need to worry about the changes that the addition of nodes will bring to the original system structure.

3. More conducive to modular system design

Because each LonWorks core chip integrates network communication, I/O functions and programmability, each node has complete processing capabilities and can work completely independently without relying on other nodes or devices.

4. Convenient programming and debugging, improved development efficiency,

LonWorks node programming uses the most common high-level language - C language, which completely frees hardware developers from cumbersome assembly language and allows them to program faster in a more structured way. On the other hand, LonWorks development is backed by perfect development tools and simulation debugging environment, which are not currently available in other control bus technologies.

The core of LonWorks technology - the embedded LonTalk network protocol allows developers to completely avoid complex communication control programming and focus on writing better I/O applications. It also provides ready-made library function support for various commonly used I/O methods, greatly simplifying the programming work and is very popular among developers.

It can be seen that due to the use of advanced LonWorks technology, the communication base station power environment monitoring system we developed has better openness, flexibility and scalability, and also protects the user's investment to the greatest extent.