Monitoring and control point at each radio station with the host computer or PLC / RTU connection as shown below:
Point diagram
Radio and the host computer or PLC / RTU connection diagram
1、Point
This is the most basic means of communication, as shown below, is equivalent to a PC and the terminal cable between the two radio stations with an alternative.
2、Multipoint
This is the most commonly used to build the net, as shown below, if the data acquisition system to use Round Robin (Polling) method. If the alarm system to use the initiative to report (Report) method can also be reported using a combination of round robin and active way.
When using the Round Robin, Round Robin cycle T (s) or system capacity N () depends on the amount of data a single point of D (bit), the radio transmission rate S (b / s) and radio transceiver conversion time t (seconds) between them have the following relationship:
T ≈ N * (D / S + t)
Use initiative to report mode, you may encounter two fired police also reported the occurrence of conflict situations. The only way to avoid conflict is to use Carrier Sense DCD (issued before viewing the channel occupancy) matched with high-speed digital radio (ie, fast transfer).
3、Transfer (one or more levels)
Local shape or communication from the requirements of the less far, the selection of transit is the only way to solve the problem.
4、Multiple base stations
In Beijing, Shanghai, Guangzhou and other large cities, urban area, buildings and more, composed by a master-multipoint networks often can not effectively cover the entire service area. At this time the entire service area should be divided into several small areas in the district composed of points from the multi-point radio network, community and inter-cell connections through the wireless link. As shown below.
5、Line shape
In practice, there are many very narrow area of communications and central control room and in the narrow terrain of the endpoint, such as river hydrology testing, railway signal acquisition, power transmission lines, alarm, oil pipeline flow control and so on. This application must be line-shaped network form, as shown below:
Line shape of each sub-station network data are needed on a poor sub-station transfer. D data, such as sub-station to reach the terminal A needs to send to D through C, C sends to B, B sends to the terminal A. The point is this way or radio station requires the storage of RTU connection forwarding function.
