ACM has the capability to poll many devices on a single radio network. However, there are physical limitations on the number of devices that can successfully coexist on a single radio network.
Serial Radio networks are limited because of bandwidth. Limiting factors include:
| Limiting Factor | Notes |
|---|---|
| Number of devices | As you increase the number of devices, you increase the amount of traffic on the network. |
| Frequency to poll real time items | Determining the required poll rates will help design your network. For instance, a network with 200 devices may only be able to poll twice an hour for live data, while a network with 20 devices may be able to handle a poll every 2 minutes. |
| Number of real-time items advised per device | The amount of time to poll each device once will increase as more data is requested of each device |
| Types of history to be collected | History collection may take a substantial amount of time/bandwidth. |
| Protocol personality | All protocols are different and some protocols are more efficient than others at transmitting both real-time and historical data. |
| Radio network quality | Poor radio network may greatly reduce the amount of data you can retrieve from devices. Multiple retries to collect real-time and historical data can possibly bring networks down to a crawl. |
| Radio network speed | A balance must be found between network speed and network quality since higher speeds increase bandwidth but reduce communication quality. |
Network Examples Table
| Network Type | Retrieving History | Speed | Comm Quality | Number of Devices | Number of Items per Device | Number of Poll Cycles per Hour |
|---|---|---|---|---|---|---|
| Serial | Yes | 9600 | Good | 200 | 40 | 1 |
| Serial | No | 9600 | Good | 200 | 40 | 3 |
| Serial | Yes | 9600 | Poor | 100 | 40 | 1 |
| Serial | Yes | 19200 | Good | 50 | 40 | 4 |
| Ethernet | Yes | 512,000 | Good | 20 | 40 | 30 |
| Ethernet | No | 512,000 | Good | 20 | 10 | 240 |
| Ethernet | No | 1,500,000 | Good | 5 | 10 | 960 |