[Imported] SmartPath for Redundancy in J Series and K Series

[sbeadle]

>>Message imported from previous forum - Category:Trio Data Radios<<
User: joelw, originally posted: 2018-10-16 21:57:49 Id:41
This is a re-posting from the obsoleted (October 2018) "Schneider Electric Telemetry & SCADA" forum.

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**_jweder:
Introduction:_**

__________________________

The SmartPath feature in the Trio J Series and K Series unlicensed frequency hopping radios is a powerful tool designed to provide redundancy for highly reliable system design. In a traditional frequency hopping system, if the Master radio fails the whole system fails. This is because the Master (or Access Point) is constantly sending out synchronization packets which all the remotes must hear to ensure they stay on the correct hopping pattern.

When a Trio system is configured to make use of SmartPath, two or more Masters may be configured to act as sync sources, and paths upstream towards the SCADA Host, for Remote or Bridge radios. Likewise, a Remote downstream of Bridges may be configured to connect to any of two or more Bridges. (Bridges spend half their life acting as Remotes on the upstream sub-network, and the other half acting as Masters on their own downstream sub-network)

SmartPath can allow the system designer to create a Mesh-like environment in which the potential upstream paths are pre-defined. Under normal circumstances the path taken will be that preferred by the designer, but when a problem occurs a Remote or Bridge can quickly re-connect to an alternate path. Later when the preferred path is working again, the radio may re-orient itself to "self-heal" the network.

Below you'll find a discussion of typical configuration requirements in a couple of different possible configurations. Only configuration items which are unique to SmartPath will be discussed.

**Two (or more!) Access Points**:
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In ALL radios in the system the network name (in both the upstream and downstream sub-networks if Bridges are used) must be the same.

In all Remotes or Bridges which will communicate directly with the Access Points, you must enter the serial numbers of all (typically two) Access Points into the Trusted Access Points list on the Security Page. (Advanced Unit Setup in K Series)
If it is preferred to normally communicate to a specific Access Point, with the other as a backup, do the following:
Ensure the preferred AP's serial number comes first in the Trusted Access Points list.

Set Trusted Access Point Mode to "Preferred/Alternate" to ensure your preference is taken into account when the Remote goes looking for an Access Point.

If it is ok to communicate normally with either Access Point then leave the Trusted Access Point Mode set to "Any Access Point."

A Remote or Bridge will, upon starting to look for a new Access Point, sync with the first one it finds that has the same network name, as long as the serial number is in the list. However, if the Preferred/Alternate mode is selected and the Remote/Bridge is not currently sync'd to its preferred AP, it will wait a preset period of time then drop out of sync and look for the preferred AP. This is the Access Point Reacquisition Time. A longer setting causes fewer communication bumps, but a shorter setting allows the system to "heal" more quickly.

By default a Remote or Bridge will stay connected to an Access Point until total failure of that path. If a cleaner change-over is desired (eg on a slowly degrading path), in Remotes enable the RSSI Threshold feature. (bottom item on the Radio config page)

Enter a reasonable Threshold value below which the path is considered to be too weak for reliability, prompting the radio to switch to the alternate Access Point. (for the 256 kbps speed with its -102 dBm Rx sensitivity the default of -90 dBm is reasonable)

Other parameters such as hopping speed, radio data rate, serial port configuration etcetera must be set as in any Trio radio system.

Attached file: (editor/i6/71f1e6fg2jue.jpg), Preferred & Alternate Masters.JPG File size: 197684

[sbeadle]

>>Responses imported from previous forum

Reply From User: joelw, posted: 2018-10-16 21:57:59
**MultiMaster Sync for Co-Located Masters**:

In a situation where two or more Access Point or Master radios share the same location it is possible for them to cause interference to each other. (one may be transmitting while the other is receiving) Keeping the antennas well separated vertically (eg at least 12 feet at 900 MHz) may alleviate this issue. But the MultiMaster Sync feature of Trio unlicensed radios can eliminate the problem. It is even possible to share one antenna when using this feature!

The cover of each Access Point must be removed and the General Purpose I/O jumper moved to the MultiMaster Sync position.

On the Radio configuration page (Port B Advanced in K Series) the General Purpose I/O pin must also be software-configured. In one radio it must be set to "Multi-Master Primary - Output" and in the other to "Multi-master Secondary - Input."

Pin 9 on the DE9 serial port of both (or all if more than two) radios must be tied together with a cable. The Primary will send a signal to the other to tell it when to transmit and when to receive. This is not an RS-232 signal so the cable can connect to more than two radios.

The Hopping Interval must be set to the same value in both radio systems to ensure they can stay in sync with each other.
If it is desired to share one antenna, an RF power splitter/combiner may be used. One example product is the ZAPD-1-N+ which is made by Mini-Circuits.

**Two paths to one Access Point**:

This configuration could be used in a system where the path from one field site to the Access Point might occasionally be blocked, but where the blocked radio could see another field site. For example in a harbor where the movement of large ships occasionally blocks one path.

- In ALL radios in the system the network name in both the upstream and downstream sub-networks must be the same.
- The system will have one Access Point (or Master) but each field site's radio will be configured as a Bridge. In this way one field site can communicate via the other.
- Enable the "Preferred/Alternate" mode on the Security page. (Advanced Unit Setup in K Series)
- Enter the Access Point's serial number first in the Trusted Access Points list.
- Enter the serial number of the other Bridge radio second in the list.

A Remote or Bridge will, upon starting to look for its Master, sync with the first one it finds that has the same network name, as long as the serial number is in the list. However, if the radio is not currently sync'd to its preferred AP, it will wait a preset period of time then drop out of sync and look for the preferred AP. This period is set with the Access Point Reacquisition Time. A longer setting causes fewer communication bumps, but a shorter setting allows the system to "heal" more quickly once the obstruction has left the desired path. (default is 30 minutes)

- By default a Remote or Bridge will stay connected to an Access Point (or upstream Bridge) until total failure of that path. If a cleaner change-over is desired (eg on a slowly degrading path), in Remotes enable the RSSI Threshold feature. (bottom item on the Radio config page)
- Enter a reasonable Threshold value below which the path is considered to be too weak for reliability, prompting the radio to switch to the alternate Access Point. (for the 256 kbps speed with its -102 dBm Rx sensitivity the default of -90 dBm is reasonable)
- Other parameters such as hopping speed, radio data rate, serial port configuration etcetera must be set as in any Trio radio system.

-------------------------
Joel A. Weder
SCADA & Telemetry Solutions Specialist
Schneider Electric

Reply From User: joelw, posted: 2018-10-17 17:12:13
**Two Paths to ONE Access Point:** nn/mu75uhff4m2v.jpg "")

Attached file: (editor/nn/mu75uhff4m2v.jpg), SmartPath Blocked Path.JPG File size: 76155