ance Temporary block flow (TBF) performance provides essential insight into the connection quality of data sessions and helps identify areas to focus on during EGPRS optimisation. The following TBF key performance indicators are useful for optimising EGPRS radio performance: 1. TBF setup success measures the rate at which TBFs are correctly established. The higher the TBF setup success rate the better the user experience is for reliably connecting to the network and minimising application latency. 2. TBF drops quantify the number of TBFs that have not completed. As a direct result of the cell reselection during the packet transfer mode, TBFs will timeout due to LLC flush (where the network continues to keep the original TBF open with no response from the mobile until it receives notification that the data session has been continued on another cell). 3. TBF blocking indicates when the packet data channel is unable to allocate radio resources due to maximum allocation of simultaneous TBFs. The limitation of simultaneous uplink and downlink TBFs is restricted to seven on the uplink (due to a 3-bit uplink state flag for identifying the unique UL TBF) and at least nine to a maximum of 31 on the downlink (due to either a vendor dependent restriction or a 5-bit temporary flow indicator for identifying the unique DL TBF). The following sections provide additional details and examples of each of these three types of TBF performance indicators. TBF Setup Success Figure 2.90 identifies the downlink TBF setup/establishment success rate across several networks. Note that the range of the downlink TBF performance was originally from around 89-95 % and then suddenly improved for all networks near the end of the time period. This improvement was the result of modifying the link adaptation parameters to bias the initial MCS to 3, resulting in more robust forward error correction and taking advantage of GMSK modulation. What is actually occurring as a result of this change is that the TBF setups succeed more often when operating a