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.

Index:

Step 1: Optimum positioning of DECT base stations

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.

1. Signal strength

   1. Distance between base stations
      1. Office space: Up to 40 meters
      2. Office areas with obstacles such as lift shafts, stairwells, metal walls: Up to 10 metres
      3. Sales areas:  Up to 60 meters
      4. Exhibition halls or production areas without obstacles: Up to 100 meters
      5. Underground garages: Up to 20 meters
      6. Outside without obstacles: Up to 200-300 meters (M700/M900 is for indoor use only)

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.

Step 2: Number of simultaneous calls

1. 1. Each base station has a maximum number of parallel calls.

      	narrowband	wideband
      Basisstation	8 calls	4 calls
      Repeater	5 calls	2 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.

      
      

Step 3: Type of installation / redundancy

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:

1. 1. You get an uninterruptible DECT network that continues to function even if a single component fails.

   2. 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.

Step 4: Using the handset to measure reception (Discovery Menu)

• Before starting the measurement, make sure that the handset is fully charged.
• Identify the MAC address of the base station you want to measure to. This information can be found on the back of the base station.
• If not already done, label the base station legibly with the last 4 characters of the MAC address (preferably frontal and very large in order to be able to read it from a great height and distance).
• Also label a handset (e.g. on the battery door) with the MAC address of the base station. So you always know later which handset was tested with which base station.

Step-by-step procedure

1. To connect your handset, press " Menu " followed by the keys: *47* to get the handset into the Discovery Menu.

   Note: Stay close to the base station (2-3m) to start the discovery.

   
   
   

2. Use the up/down cursor to select the base MAC address for the base station.
   
   
   
   

3. Select the desired base station.

4. The handset display will show the base level "RSSI" (Received signal strength indication).
   
   
   
   

5. 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.
   
   

Step 5: Documentation of DECT measurement

Building plan:

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.

DECT-Measurement list:

• 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.

Snom_DECT_Ausleuchtung_Liste.pdf

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.

General information

• When the muti-cell system is set-up, all the settings are automatically synchronised across all base stations. The way the sync mechanism works depends mainly on how the Data Sync in configured:
  
  
  • multicast: if you are using multicast you can change one or more settings on any base station of the system. All changes will be propagated automatically among all base stations. In this situation you should avoid to work on more than one base at the same time.
  • peer-to-peer: in case the system is set using peer-to-peer, you should always change the settings only on the Primary data sync DECT base station (Primary). Changing a setting on another base will not trigger a setting synchronisation.
    → Multi Cell
    
    
    
    
• Multi Primary should be avoided except for some very specific situation.
• In production the DECT tree should be calculated automatically by the system in order to offer the best coverage and redundancy.
  → Multi Cell
  
  
• Once the DECT network has been installed, check the optimum coverage using Survey Mode.

Download Guide:


Snom Multi-Cell Guide - M700 - 2018.pdf