Howto:Debugging tools for DECT deployment

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For DECT trouble shooting 3 helpful instruments exist: the statistics page,the Dect Radio page and the handset in deployment mode.

Here is how to use it.

Applies To This information applies to

  • IP 1200

build V6 and later.

Contents

More Information

The Statistics Screen

The Administration / DECT / statistic screen provides some important information regarding the operation of your IP1200 system.

Here is an explanation of the Master values.

  • Calls in: All incoming calls on the DECT master.This number will not include calls which are destined to a DECT handset but then are connected to an external phone (this will happen e.g. for users with a twin-phone setup when accepting the call on the fixed phone).
  • Calls in Delivered: All incoming calls that were put through on the DECT master.If a call comes in and the corresponding handset could not be reached (out of coverage or switched off or no channel available), then this call will not be considered “delivered”
  • Calls Out: All outgoing calls on the DECT master.
  • Handover: All handovers that took place on the DECT master. If a mobile phone is located in the transmitting range of the DECT master and switches to a different transmitting range (DECT radio), a handover to the next transmitting range must take place, so that the DECT master knows how the voice data is to be routed.
  • Handover Failed: All failed handovers in the DECT master range.Note that these numbers do not include attempted bearer handovers. In a healthy installation, the handover failed number should be 20% or less of the handovers.
  • Abnormal Call Release: All other failed calls. An example of such an Abnormal Call Release is a mobile phone battery that has become empty.This is the most important number in the statistic screen. It should normally be zero. The only 2 situations where this counter should increase is when a handset is switched off or runs out of battery and when a user walks out of the coverage area during a call.Otherwise, when this number increases, users have suffered a dropped call.

Radio section:

  • Calls in : All incoming calls on the DECT radio.This counter is incremented whenever a handset in the radios cell answers the call (i.e. alerts)
  • Calls Out: All outgoing calls on the DECT radio.
  • Handover: All handovers initiated on the DECT radios that took place. If a mobile phone is located in the transmitting range of a DECT radio and leaves it, a handover to the next transmitting range (radio or master) must take place, so that the DECT master knows where the voice data is to be transmitted to.
  • Handover Failed: All handovers initiated on the DECT radios that failed.Note that these numbers do not include attempted bearer handovers. In a healthy installation, the handover failed number should be 20% or less of the handovers.

Finally, the total operating time of the DECT subsystem is displayed.


You should look at the statistics page in the master first.

This cumulates all calls.

You may look at the statistics page on the individual radios if you have isolated a radio creating problems.

The signal strength table

In each radio (not only the master), you can see the relative signal strengths of all surrounding radios which are in sync.

In any IP1200, use this view to verify the signal strength of the sync sources for this IP1200.

This will output the next best bases along with their ID and RSSI value.

image:Howto-Rules_for_successful_IP1200_deployment_Dect1.PNG

In this table, the values in brackets are decimal (although they start with 0).

RPN is the Radio-ID, RSSI the relative signal strength.

Unfortunately, the RSSI value is coded differently from the RSSI shown in the handset in deployment mode (see below).

A value of 25 is equivalent to a value of approx. 80 on a handset.

For a sync source, the RSSI must be at least 25 or 80 on the handset. Higher is better. For call handover, the RSSI must be 28 or higher.

Handset in deployment mode

Any innovaphone DECT handest (IP50, 52, 54, 64) can be used for deployment to determine the quality and signal stength of existing radios.

For this, you need to enable the “best bases” screen.

  • use feature code *99989* followed by OK to show RPN in hexadecimal
  • use feature code *99981* followed by OK to show RPN in decimal

Then place a call (you will not see the call on the display as it only shows the deployment screen).

All values shown are meaningless if the phone is on-hook! The screen will show 3 lines as follows:

RPN:<id1> <id2> <id3>
RSS: <ss1> <ss2> <ss3>
<cid> <q52> <css> <freq><slot><handover>

<cid> is the id of the radio the handset currently is using.

<q52> is the Q value of the current connection.

<css> is the signal strength of the radio currently in use

<freq> is the frequency used (the frequency actually used is 1897.334MHz - <freq> * 1.728MHz)

<slot> is the time slot used

<handover> is the type of the last handover (B bearer handover, C connection handover, 0/C none)

All radio ids are in hex, anything else in decimal.

So if your last line shows “0A 64 97 520”, then the handset is using radio 0A (which is 10).

The connection is perfect (as 64 is the maximum) and the signal strength is also very good (97 is the typical value you would see next to the radio, but see below).

The first two lines indicate the next best bases, sorted by signal strength.

If these lines show

RPN: 05 0F
RSS: 95 80

then the next best radio is number 5 with signal strength 95, the second best is 0F (which is 15) with signal strength 80.

You can force the handset to perform a handover immediately by pressing menu / #. However, if you don’t the handset will follow its normal handover strategy (as described in a separate article).

To test sound quality you can make a call to ECHO interface by dialing *9999*. This feature is in V6 SR2 hotfix3 available and IP1200 not need to be factory resetet to actate the deployment mode. Best practice is to use a headset in this mode, so you able to see RSS values on the phones display and talk to ECHO interface in the same time.

Handset Calibration

Please note that standard handsets are not fully calibrated.

So precisely spoken, the highest RSSI value (the value you would observe when directly next to a base) is not always 97 (as said above).

It may differ quite a bit so in principle you would have to determine the reference value and then calculate offsets to that reference value.

However, in real life, RSSI values are not that important.

For good deployment, as a rule of thumb, an RSSI with less than 80 is a good reason to look for better alternatives.

But there is no strict rule here (such as “81 is good and 80 is not”).

Instead, you have to observe Q value and voice performance carefully. This is much more important.

Hex / Decimal Conversion chart

Radio IDs are shown in hexadecimal in the “best bases” screen.

However, in the IP1200 configuration they are entered in decimal.

So here is a conversion chart.

image:Howto-Debugging_tools_for_DECT_deployment_Hex_chart1.PNG

Related Articles

Howto:Rules for successful IP1200 deployment

Howto:How to configure IP1200

Howto:How to program repeaters for DECT systems

Howto:Understanding DECT handover with IP1200

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