marposs WRP45 - WRS System Distance Rules; Automatic Channel Selection (ACS)

WRS – Installation Manual
49
Communications are practically continuous in the channels used by the Andon
™
system, therefore they may
represent a source of interference for the WRS system. In order to co-exist correctly with this system it is
necessary to observe the following precautions when selecting the WRS frequency:
• Fc (WRS) ≥Fc (Andon
™
) + 2.5 [Mhz]
Or:
• Fc (WRS) ≥Fc (Andon
™
) - 2.5 [Mhz]
Where:
• Fc (WRS) is the main WRS system frequency;
• Fc (Andon™) is the main Andon™ system frequency.
D. IEEE 802.15.4 systems
These transceivers are sometimes used in customised protocols for industrial environments and give rise to
moderate levels of interference.
4.10.10 Distance between WRS systems
Table 4-8. Rules defining the distance between WRS systems.
Distance
Example
a) Minimum distance between any WRI receiver and/or WRP
transmitter (using different channels)
0.5m 27A  0.5m 43A
b) Minimum distance before re-allocating any given frequency channel
100m 27A 100m 27A
c) Minimum distance when using the same channel with a different
sub-channel
30m 27A  30m  27B
[
N.B.:
Rule c) does not apply in the case of Multi Probe Management (see para 4.12.5
) where the
transmitters are operated one at a time, and not simultaneously.
Example: WRP + WRTS and WRI. When WRP is ON, WRTS is OFF and vice versa, this means
that the only limit on the distance between WRP and WRTS is given by rule a).
Rule c) is applied only when two systems may be operated simultaneously.
4.10.11 Using automatic channel selection (ACS)
During the pairing procedure between a WRP transmitter and a WRI receiver it is always necessary to select
an operating channel; after that it will be possible to allow the ACS system to change channels, if necessary.
Please note that the default ACS setting is deactivated. In fact, in order to avoid potential interference issues
with other radio systems, the user may first decide to determine the exact location of every other wireless
system in use within the company. It is important to check this condition before activating the ACS system.
1. Best channel selection algorithm
Immediately after enabling ACS, the WRI receiver samples all the channels in order to create an RF noise
map. A complete analysis of the entire band takes about 10 min.; this is the minimum time the ACS system
needs in order to guarantee that the “automatic channel change” function is effective and ready. During
normal operation, the WRI receiver does not scan the local environment continuously, but only when the
START command is not active, which means that the analysis is suspended during the measurement
operation.
This function is important because it enables the WRS to adapt automatically to changes, such as the
introduction or removal of other wireless systems. Nevertheless, it is important to bear in mind that any signal
at 2.4 GHz could affect how the ACS system behaves; in particular, it has been demonstrated that the
personal Wi-Fi
®
routers used in the factory and other “non certified” type devices can cause the system to
switch channel unexpectedly.