• PS Network Optimization Parameters

The TBF drop rate involves the uplink and downlink of the GPRS and EGPRS services. At the same time, the drop rate can be classified into the N3101, N3103, and N3105 overflow drops according to the timer.

Majority of the TBF drops is generated because the CS service preempts the dynamic channels.

1. When the TBF drop rate is degrading, check the GPRS or the EGPRS service according to the service type. If a service is faulty, the setting or the related parameter is incorrect.
2. If the problem occurs in certain cells, check whether the cell is configured with the dynamic PDCH. To solve the problem, disable the dynamic PDCH temporarily (or change the dynamic PDCH into the static PDCH).
3. If the problem is not caused by the incorrect setting, check whether the accessibility of each cell is of the same level. Then, determine whether the radio quality is affected according to the drop rate in the CS domain.

For how to check and process the TBF drop rate, refer to the GSM BSS Network KPI (TBF Drop Rate) Optimization Manual.
Owing to the unbalanced development of the GPRS service, the KPI in the PS domain of certain cells in the network cannot reach the standard, especially when the handover is not enabled in the PS service.As a result, the drop rate is high in certain cells and the problem cannot be processed.In this case, provides the carrier with a written report according to the actual condition. You need not process the problem.

Maximum Value of N3101
Value Range: 8-30
Unit: None
Default Value: 20
Description: Maximum value of N3101.

In uplink dynamic assignment mode, multiple MSs can share one uplink channel if the downlink data blocks carry the USF value.
After the network starts to assign a USF value to the uplink TBF (uplink TBF is established), N3101 is started.
The network waits for the uplink data sent by the MS on the reserved uplink RLC block corresponding to the USF.
If the MS sends a valid uplink RLC block, N3101 is reset.
Otherwise, N3101 is added on the network side.
When this counter overflows, the current uplink TBF is released abnormally.
Remarks

If this parameter is set to a lower value, the tolerance of the network to uplink errors decreases and the probability of abnormal TBF releases increases.
If this parameter is set to a higher value, the network still assigns uplink resources to an MS even though it does not receive correct MS data blocks because of MS activities. Therefore, network resources are wasted.
Maximum Value of N3103
Value Range: 2-5
Unit: None
Default Value: 3
Description: Maximum value of N3103.

If the network receives the last RLC data block when the uplink transmission is complete, it sends the MS a Packet Uplink Ack/Nack message with FAI=1 and starts N3103.
If the network does not receive a packet control acknowledgment message within scheduled time, N3103 is added on the network side and the network resends the Packet Uplink Ack/Nack message.
When this counter overflows, the network starts T3169.
When T3169 expires, the current TBF is released abnormally.
Remarks

If this parameter is set to a modest value, the tolerance of the network to uplink errors decreases and the probability of abnormal uplink TBF releases increases.
If this parameter is set to a higher value, the network still assigns radio resources to an MS even though it does not receive a correct packet control acknowledgment message because of MS activities.
Therefore, network resources are wasted.

Maximum Value of N3105
Value Range: 3-10
Unit: None
Default Value: 10
Description: Maximum value of N3105.

After the a downlink TBF is established, the network starts N3105.
After the network set the RRBP on the downlink RLC data block, it resets N3105 when receiving a valid packet acknowledgment message on the uplink RLC data block corresponding to the RRBP.
Otherwise, N3105 is added on the network side and the network resends the downlink RLC data block where the RRBP is set.
When N3105 overflows, the network starts T3195.
When T3195 expires, the current TBF is released abnormally.
Remarks

If this parameter is set to a lower value, the tolerance of the network to downlink errors decreases and the probability of abnormal downlink TBF releases increases.
If this parameter is set to a higher value, the network still assigns radio resources to an MS even though it does not receive a correct packet control acknowledgment message because of MS activities. Therefore, network resources are wasted.