Polling means check the status of (a device), especially as part of a repeated cycle.
Significance of these variables/timers/counters
BYTE_WITHOUT_POLL is to tell the other AMD-RLC peer when to trigger the STATUS report.
Initially the values for these counters will be set to 0 and Upon assembly of a new AMD PDU, the transmitting side of an AM RLC entity will increase the counter to 1.
PDU_WITHOUT_POLL= will count the PDU's that how many PDU's it can allow without asking for the status report.
BYTE_WITHOUT_POLL: will count the number of bytes it can allow without asking the status report.