Warehouses can be challenging for RF and cellular signal communication, as many have experienced trying to use mobile phones inside some of them.
The reason for bad RF and cellular distribution inside warehouses can be many. Below are list of things that attenuates RF and cellular signals:
- Metal frame buildings
- Metal storage shelf's
- Metal partition walls
- Stored goods (water rich, metal, etc.)
- Goods movie around
- Traffic of machinery (forklifts etc.)
Based on experience and signal measurements inside warehouses, following signal attenuation can apply:
Signal obstacles
Signal Obstacle | Signal Attenuation |
Laminated warehouse/cooler metal wall | 40% |
Storage shelf with mixed goods | 10% (can be higher, depending on the goods*) |
Reinforced concrete wall – 20cm | 5%-20% (depending on the steel mesh size) |
Free air between storage shelf's (10m distance) | 20% |
Free air between storage shelf's (20m distance) | 30% |
Free air between storage shelf's (50m distance) | 40% |
Storage cage (Wire gauge) | 0% to 100%, depending on the mesh size** |
| Moving traffic (people, machinery etc) | 3% to 20% (In some cases machinery can block the RF signal) |
*Water rich products such as watermelons and lemons are challenging for RF signal ** If the mesh size in the wire gauge is the same as the RF wavelength (1/1, ½, ¾, ¼,…) then the wire gauge can block the RF signal. (RF wavelength for CE version CO 01.01 is 34,538 cm, For US version CO 11.01 the wavelength is from 32,305 to 33,126cm) | |
Based on the above roles of thump, these guidelines must be followed:
Gateway locations
Location | Exhibits | Gateway |
Warehouse Storage aisles | Exh. 3
Exh. 4 Exh. 2
| a) Fasten the gateway upside down above the storage racks. Ideal location is on the load bearing beam in the ceiling. b) Use plastic cable ties to fasten the gateway c) Place one gateway in every six (6) storage aisles (one gateway to cover six storage aisles) d) If the warehouse stores water rich goods, the distance between gateways must be shorter
|
Walk in cooler | Exh. 5 | Gateway must be within 12m from the cooler |
Drive through freezer/cooler |
| a) Short/small storage room – Place the gateway outside of the freezer/cooler room wall b) Long/large storage room – Place the gateway outside of the freezer/cooler wall and extend the RF antennas inside the storage room Note: Never place a gateway in environment where the temperature is below 0°C |
Storage cage |
| Depending on the mesh size |
Warehouse docking |
| a) Fasten the gateway at high point on a column, facing the docking area. b) If there is no obstacle for the RF signal, one gateway can cover up to 50m in both directions |
Exhibits - Warehouse storage aisles
Exhibit 1. Drawing of a warehouse
Exhibit 2. Logger location selected
(1) logger distributed over the storage aisles, (2) loggers in the docking area, (3), loggers in the drive-in freezer and cooler, (4) logger in the walk-in cooler and (4) logger in the storage cage.
Exhibit 3. Gateway location selected
(1) Gateways in storage aisles, 5 to 6 aisles apart,
(2) Gateways for the docking area,
(3) gateway facing the walk-in cooler and the cage storage (12m from the cooler),
(4) Gateway for the freezer and the cooler with extended RF antenna into the storage room.
Gateways (1), (2) and (3) placed above the storage racks. Gateway (4) fasten outside of the coolers and the RF antenna extended inside the coolers.
Exhibit 4. Gateway above storage racks
To ensure sufficient signal quality for loggers in the storage aisles, one gateway must be located every fith to sixth storage aisles. This depends of what kind of goods is stored in the aisles.
Note, the gateway must be installed upside down i.e. with the RF antenna facing down.
Exhibit 5. Gateway fasten to the load bearing beam in the ceiling
Exhibit 6. The Gateway is fastened to the load bearing beam with cable ties
Exhibits - Walk-in cooler
Exhibit 7. Gateway distance from walk-in cooler
The gateway should be within 12m in abstructive view from the cooler
Exhibit 8. Gateway 12m from the walk-in cooler
Place the gateway within 12m from the walk in cooler and above moving traffic
Exhibit 9. Gateway fastened on wall
When a gateway is fastened to a wall, it hould be fastened with screws or using cable ties
Exhibits - Drive in freezer or cooler
In the case of large freezers or coolers, the RF antennas must be extended to the inside of the freezer/cooler. Note, a gateway must not be in a enviroment where the temperature can be below 0°C.
Exhibit 10 - Gateway RF antenna extended to inside of a freezer or cooler.
