Operating instructions

TD 92579GB
2009-04-15/ Ver. B
Installation and Operation Manual
IP-DECT Base Station & IP-DECT Gateway (software version 3.0.x)
77
Select Synchronization Source for IPBS in Slave Mode
An automatic selection mode is available allowing the IPBS to automatically select another
IPBS as a host base. The IPBS automatically creates and updates a list of IPBSs, within the
coverage area.
A general criterion in the automatic selection mode is that an evaluation must be done on
the bearer. The numbers of incorrect A-fields are accumulated during 100 frames. This
value is called the Frame Error Rate (FER). If the FER value is above 90 the bearer can not
be used to start retrieve sync information from. However due to the nature of radio
environment the FER value may later increase above 90.
Startup of Master IPBS
When a Master starts up it searches for other IPBSs within the same system during 30
seconds. If any IPBS is found the values for slot, frame, multiframe and PSCN is received
and applied to the Master. After receiving all these values or after the timeout of 30
seconds the Master enters the Master state.
In Master state the values are updated locally during all further operation of the Master
IPBS and no synchronization to other IPBSs in the same system is done.
With this method it will be possible to restart only the Master in the system. The remaining
slaves will be able to maintain synchronization for a few minutes during restart of the
Master. The Master will adjust itself to the other IPBSs at startup. The slaves will notice the
Master is back and the sync will be received from the Master.
If no IPBS within the same system is detected during the first 30 seconds at startup initial
values will be selected and the IPBS will enter Master state with these values.
Sync Backup Master
Only one Sync Master IPBS needs to be configured for a system. But if this single IPBS fails
the entire system will fail. It is therefore possible to configure a Sync Backup Master IPBS in
the system.
If a Backup Master IPBS is configured this IPBS must be positioned next to the ordinary
Sync Master. A good value for RSSI is between -30 and -50 dBm.
A Sync Backup Master IPBS will start to search for an active Sync Master within the
coverage for 1 minute. If a Sync Master is found during this first minute it will start up in
FER value Description
< 90 In this case the active sync bearer is only replaced if:
Alternative sync bearer with lower HOP value is found. Even if an alternative
bearer with better FER and RSSI is found this is only selected if the HOP value
is lower.
> 90 In this case the active sync bearer is only replaced if:
Another bearer with lower HOP value is found.
OR
Another bearer with same HOP value is found and with BER < 90.
= 100 Assume the slave has locked to a RFP with hop value n. When the RFP have
had FER = 100 on the active sync bearer for 80 seconds it is allowed to sync
to a RFP with hop value n+1. After another 40 seconds it is allowed to sync to
a RFP with hop value n+2, etc.
After 9 minutes with FER = 100 the "Sync lost counter" is increased and a
restart of the air sync procedure is done. ("Sync lost counter" may increase
for a number of other reasons also)