e of the IR phenomenon. LA operates always on a first-sent block or a re-transmitted block, and upon receiving BEP measurements will change the MCS according to the condition of the network. IR is a specific re-transmission algorithm also known as 'hybrid ARQ II' (it includes puncturing, storage and soft combining at the receiving end) that if enabled together with LA will allow a change in MCS within the family. In order to change MCS during re-transmission, LA should be enabled. Note that ETSI specifications make IR mandatory only for the MS as receiving side, not for the BTS. Channel Allocation Channel allocation in EDGE networks is nearly the same as in GPRS networks. BCCH, PCH, RACH, AGCH are the signalling channels, while PACCH is the only associated channel when the physical resources are assigned. Channel allocation algorithms are responsible for assignment of the channels to mobile stations. The EDGE base station should be capable of being synchronised with the existing GSM base stations. This will maximise the efficiency as both the base stations can be configured as one sector instead of two, thereby making only one BCCH necessary for the operation. Moreover, an increase in data rates leads to an increased signalling requirement for a given traffic and applications. Smart Radio Concept Implementation of the smart radio concept enhances the performance of the radio link, both in the uplink and downlink directions, by the use of diversity methods described later in the chapter. EDGE NETWORK PLANNING 6.3.2 Radio Network Planning Process The basic process of radio network planning remains the same as in GPRS networks. However, because of the changes in the modulation and coding schemes, there are some changes in the coverage, capacity, and parameter planning of EDGE radio networks. Coverage Planning The link budget has a direct impact on coverage. As the EDGE network focuses more on PS data, the delay tolerance becomes a critical factor in defining system quality level. Some factors that affect link budget