ansmission technique (to be used for mobile accesses) that is standardized by ETSI as an enhancement of present GSM. By using a more advanced modulation technique, a threefold increase in bitrates compared with standard GSM modulation is expected. EDGE is presently introduced both in GSM and TDMA/ 136 systems. WCDMA, Wideband CDMA, is a new type of mobile radio access, based on a completely dif- ferent radio interface (a single 5-MHz carrier instead of the 200- kHz GSM carrier) and tech- nique for data encoding than in GSM and TDMA/136. WCDMA accesses will provide data rates up to 2 Mbps (enough for, e.g. video conferences between mobile users). WCDMA is presently standardized by ETSI project 3GPP. 3.5 Logical Network Structures standards apply the interface refinement principle that was defined in Sect. 2.3.3. Figure 3.92 gives an example of how this principle can be used to describe proto- cols for network service interfaces. Vertical integration: Physical node Logical network A Abstract protocol Logical network B Horizontal integration: Physical node Logical network A in network X Message protocol Logical network B Physical node in network Y Fig. 3.92 Horizontal integration by interface refinement The physical nodes in vertically integrated networks must handle protocols that belong to different logical networks, as shown at the top of Fig. 3.92. On the other hand, network service interfaces can normally be implemented by local means, i.e. simpler means than by standardized protocol. These interfaces, when they are described at all, are described as abstract protocols. Only OSI RM developed some initial notations for that; however, they are seldom used in standards in the telecom industry. The physical nodes in horizontally integrated networks comprise protocols that belong to one or a few logical networks. Since the physical nodes that handle different logical networks may also belong to different operator networks, it is necessary to develop and standardize message protocol solutions to network service inter