f the incoming CSW call requests. When the number of free timeslots in the CSW territory falls below that required to be free, then a GPRS downgrade is initiated to correct the situation. The (predefined) number of free slots allocated is based on the probability of 95 % that a further downgrade will not be required while there is already a downgrade in progress. If the GPRS territory has been enlarged beyond the default boundary and the GPRS traffic requirements are decreasing, a downgrade will occur to re-allocate the freed timeslot(s) back to the circuit switched territory. GPRS Upgrade There are two corresponding scenarios that result in GPRS upgrade: Where the CSW territory has moved into the default GPRS territory and the CSW traffic is decreasing, the CS RRM will initiate a GPRS upgrade to re-allocated timeslots back to the GPRS. Again, the number of free slots required to trigger the upgrade is dependent on the number of carriers per cell. In the upgrade case, however, the number is that which would result in there being no need (at 95 % probability) for a downgrade within four seconds of an upgrade having occurred, thus allowing for a degree of hysteresis. Where the GPRS service requirements are not being met by the number of timeslots in the GPRS territory (which is already at the boundary of, or into, the default circuit switched territory), and where the traffic level in the CSW territory permits, a GPRS upgrade is performed to increase the size of the GPRS territory. The rules governing this are based on the number of temporary block flows (TBFs) per timeslot; once the average number of users sharing the GPRS timeslots becomes too great (as defined by a nonconfigurable system parameter), the upgrade will be attempted. Preliminary values for the number of free timeslots in the CSW territory are given in Table 2.16. The mean number of free timeslots in the CSW territory is also given, on the assumption that there are, on average, equal numbers of upgrades and downgrades. Data Throughput The overall EGP