radio conditions (high signal strength and low C/I). The following considerations help to ensure reliable test results during field optimisation: 1. Ensure your mobile and test equipment are loaded with the proper software levels and support the applications desired to be tested. 2. Make sure your mobile measurement and application 'bus' can support the processing demand you are driving it SO you are able to set up your repeated application driver plus take reliable measurements while the phone is still able to fulfil the EGPRS/GSM processing duties (e.g. reliable adjacent cell measurement). 3. Considering the above, always keep in mind that the actual device portfolio that your network sup- ports will very likely have behaviours that differ (sometimes significantly) compared with your measurement/optimisation tool. This makes it important to try to make some device comparisons using 'engineering mode' flashed software on as many live deployed devices as possible. 4. While you are conducting your ideal radio condition test, you should benchmark the speed and latency of your reference APN to set an expected behaviour. After the test equipment and ideal test have been benchmarked, mobile testing can proceed. Dur- ing drive testing and analysis, it is recommended to focus on the following key layer 3 messaging information: Radio Network Planning and Optimisation UL TBF Hardblocking 20-Aug 3-Sep 17-Sep 1-Oct 15-Oct 29-Oct 12-Nov DL TBF Hardblocking 20-Aug 3-Sep 17-Sep 1-Oct 15-Oct 29-Oct 12-Nov Figure 2.93 Sample uplink and downlink TBF blocking During sustained packet data transfer: 1. Packet Downlink/Uplink Ack/Nack (PDAN, PUAN). These messages contain the essential information for flow control and measuring channel conditions. Two important contents include the Receive Block Bitmap (RBB) for identifying specific RLC block errors and final acknowledge indicator (FAI) to highlight the final RLC block in a TBF. During cell reselections: System information messages 1 to 4 and 13. As indicated previously, the mobile mu