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Reply To: loss free preemtion



Once again, sorry for my delayed response.

When an MS is engaged in a downlink packet transfer, it’s data is kept in a buffer (or queue) on the PCU. Now if the MS reselects another cell, it sends a cell update message to the SGSN. When the SGSN notices that the mobile was already engaged in packet transfer, the SGSN sends a FLUSH message to the PCU of the old cell. The contents of this message can result in one of the following:
1. If the new cell belongs to the same RA as the old cell, then the PCU moves the contents of the buffer to a new buffer for the MS, and the counter FLUMOVE is incremented.
2. However, if the new cell is in a different RA, then the PCU discards the contents of the buffer, and FLUDISC is incremented.

I’ll say once again that I don’t believe implementing loss-free preemption will reduce the values of these counters.

Whenever you have an inter-RA cell reselection, the TBF is released, and a new one is setup in the new cell.

If you can get statistics on these counters on cell level, you should be able to identify the worst cells and see how you can redesign your RA.

Hope this helps.