In this guide we explain what to consider when planning a DECT multi-cell installation with the Snom M700/M900.
In particular, we explain the measuring procedure with the help of a measuring case provided by Snom or partner companies.
We offer a DECT measuring case:
DECT Radio measuring Kits are equipped with two M700 base stations with battery pack (and charger), as well as 4 x M65 handsets including charging cradles. The "Snom DECT Radio Measuring Kit" comes with two tripods for the base stations.
The DECT measuring cases can be purchased or borrowed. For inquiries about a suitcase please contact: email@example.com .
For an optimum illumination of the DECT multi-cell, i.e. area-wide and uninterrupted coverage of the DECT signal, a number of factors need be taken into account.
Obstacles, such as walls, doors, metal or concrete of all kinds, as well as damp wood disturb the reception.
→ Read more details about the positioning of your base stations here.
The reception value between two base stations should always stay within the range of -70 dBm to -75 dBm. Handheld devices should not have a reception value of less than -80 dBm to prevent dropouts or even call interruptions.
At values of -90dBm or less, spontaneous signal interruptions are likely to occur.
Each base station has a maximum number of parallel calls.
In addition, two additional call slots for handover and roaming are available for each base station.
(In single cell mode, the total capacity of an M700/M900 is therefore 8+2 = 10 calls.)
ATTENTION: Please note that each handset occupies one channel as long as it is ringing. If, for example, you have 5 handsets in a "call group" ringing at the same time, 5 channels are temporarily blocked until one answers the call.
In order to avoid a single point of failure, i.e. a malfunction due to the failure of a single base station, you should ensure that redundancies are created when positioning the base stations. You should place two or more base stations, overlapping each other.
This has two advantages at once:
You get an uninterruptible DECT network that continues to function even if a single component fails.
The number of simultaneous calls increases. Of course, this also applies to Roaming , and Handover . If someone roams with his DECT telephone through the different DECT zones, the call is transferred from one cell to the next and occupies at this moment at different base stations a caller slot.
As the M700/M900 keeps all information completely redundant as soon as it is connected to the partner base stations (comparable to the domain controller in Windows servers). There is always one "DECT Primary" base station per forma, which changes every 10 minutes, so it does not matter if one or even two base stations fail for a short time or even longer during optimal meshing.
To connect your handset, press " Menu " followed by the keys: *47* to get the handset into the Discovery Menu.
Use the up/down cursor to select the base MAC address for the base station.
Select the desired base station.
The handset display will show the base level "RSSI" (Received signal strength indication).
Optional: Press the "off hook" key (green key) to establish an audio loopback connection with the base station. Now press the central key between the arrows and a continuous tone will be sent to inform you if the speech signal can be sent without interruption. In addition to the measured value of the frequency spacing, this gives you further indications as to whether your base stations are optimally positioned.
Snom recommends using a building plan and checking the base station coverage using the RSSI signal strength indicator from each base station. It is best to record the planned base stations directly in the building plan, as well as the measurement results for the various base stations in a separate list (e.g. our Dect lighting list, see below). Assign a unique name to the locations of future M700/M900 base stations, followed by the last 4 characters of the MAC address you used for the measurement.
|Step 1: Position first base
|Step 2: Measure the cover and place the next base at -75dbm distance.
|Step 3: Measure the cover and place the next base at -75dbm distance.
|Step 4: Measure the cover and place the next base at -75dbm distance.
|Step 5: Now all areas are covered and further bases can be positioned for redundancy reasons.
For the measurement we offer a list in which you can enter the last four characters of the MAC address of up to four bases.
Enter the position number in the lines, which you have entered on the floor plan and possibly also note down the Mac address (2-4 characters) of the base station which you have set up at this location. So you can keep the overview better.
Now enter the values for the other bases you have set up.
The measured values are of course received from the handsets registered on the respective base stations. In this example we have 4 base stations and 4 handsets in use.
If the area you want to measure is larger and the 2 or 4 test base stations used are not sufficient to optimally supply the desired area with DECT, then we recommend dismounting the most distant test base station and moving it forward in the measuring direction for further measurements. Place it at a position where the next base station is intended to be positioned, always under the condition < -75dBm.
Physical installation : Find here some Details to the DECT - 2. Physical installation.
Multicell setup : Find here some Details to the DECT - 3.0 Multicell setup.
Site Survey : Find here some Details to the DECT - 4. Site Survey Mode.
Discovery Menu : Find here some Details to the DECT - 5. Measuring with DECT Discovery Mode.
Snom Multi-Cell Guide - M700 - 2018.pdf