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Hi,
Radio Link Timeout is somehow related with drop call rate. In some literal example, we may experience long duration of bad quality call but still the call doesn’t drop also in reverse we can also experience not so bad quality calls but suddenly it drops. RLT may be related with this scenario(but still consider some other factors and parameters).
The value decremented by 2 every non decoded SACCH (corresponds to poor c/i) and incremented by 1 every decoded SACCH(good c/i). When this value reaches zero, drop call may be experienced. Thus setting the RLT too high means prolonging the calls eventhough bad quality is experienced.is max RLT responsible for increase in call drop in cities having more number of bts’s at a less than 500m placed?
RLT should be long enough to give a chance to MS to recover radio link.
RLT greater than 15 SACCH, that’s plenty enough.
If the value is too high, the TCH is kept for too long after the drop –> TCH congestion.
The drop is still counted though 🙂When you are changing the RLT u must also consider the Channel release parameter t3109 in the BSC, they must be close to each other, otherwise it can cause cross talk.
sir,
i’m fresher to drive test.i want to know more about drive test,practically and theoritically,define & explain RLT Counter
Why Radio Link Timeout(RLT) Value is having max. value of 64 only..??
hi,
how much time do you need to detect a call drop ?
how long do you want to keep a resource allocated to a MS which is lost ?
32 seconds seem like a hige value already 🙂regards
pixDear Pix
my doubt is why its designed to have Max value of RLT to be “64” only not “32” or “128”. Is there any reason to have this value at 64??hi,
32 is a useful value, for AMR calls (but 3GPP could not have known that 20 yrs ago), so if that was the max limit, it would have been a bit restrictivie, in some special situations.
128 is super huge.cheers,
pixI am just a fresher in dt i wana get knowledge abt it n want to download e books related to it..
If possible 4 u plz mail me the notes of dt..what is the use of DR(direct retry) in GSM network?
DR is used when a MS is performing a call setup in a cell which has no more available TCH (= congestion case).
During the call setup, since the cell cannot grant a TCH to this MS, the MS is put in a queue. The MS is still connected, on a SDCCH.During this queueing time (T11):
– if a TCH is made available in the serving cell, then the MS will get it and resume the call setup.
– if the BSC sees that the MS is experiencing “handover” needs (“emergency” or “better conditions”), and if DR is enabled in the cell, then it will attempt a “normal directed retry” : the MS will do a “SDCCH to TCH” handover, from the serving cell to the target cell.
– if the BSC detects the HO cause “forced directed retry” is fulfilled and the “FDR” is enabled in the cell, then the MS performs a HO from SDCCH to TCH, from serving cell to target cell.So there you are… that’s the whole explanation 🙂
Hi Pix,
HRU, Can we decrease the RLT drop without changing RLT parameters,Mechanical Tilt,& without reducing BTS power
Hi to everyone…
Can You please post the whole theory related to RLT, because every put his own answer in part and to read tis i am get confused…….
so please do needful to me………..
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