More than 63 TA in Drive Test tools

In TEMS and even new Infovista DT tools you cannot see more than 63 TA even when reaches 219 TA’s in reality.


Can someone please explain the reason?

Normal cell max TA is 63. If extended range cell, TA can be higher.

In some GSM protocol layers the granularity of the Timing Advance (TA) is 6 bits (0-63), in other areas it is 8 bits (0-255). So lets say your UE is 30km away from the BTS - at max timing advance (disregarding ext range) - then some protocols will say TA 63, other fields will indicate TA 255.

You need to know the granularity of the specific field you are looking at.

Timing Advance for RAR = 0,1,2…,3846
Timing Advance for MAC-CE = 0,1,2…,63
So, need to check what are we actually measuring in TEMS.

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extend cell range is BSS feature; ms no idea about true distnace from antennas thus tems/infovista will never show more than 63 TA’s-8bit
this is because ERC feature uses the true TS+ next consecutive TS bit (actually 156 bits), so it doesn’t matter if the burst arrive late to MS at the end we got (63+156)=219 bits at BSS not at MS