Filter Filter (PSTN/ ISDN) Max length 0.3-1.5 km 13-52 Mbit/s Internet 1.6-19 Mbit/s (data) Figure 13.33 Very high bit rate digital subscriber line (VDSL). Example SHDSL is also known under its standard name G.SHDSL or ITU-T standard G.991.2. SHDSL delivers greater bandwidth over longer distances than current 2B1Q-based SDSL and traditional HDSL systems and enables operators to provide symmetric, high- speed data transmission over existing copper pairs. The standard is a multi-rate DSL technology that allows data rates from 192 kbit/s to 2312 kbit/s and can transport T1 (1544 kbit/s, E1 (2048 kbit/s), ISDN, ATM and IP signals. Symmetric solutions fit small and medium enterprises with roughly the same traffic volume in and out. 13.12.4 VDSL An even faster technique is the very high bit rate digital subscriber line (VDSL). See Figure 13.33. Here the standard defines the full bit rate to 26 Mbit/s in each direction for symmetric traffic, or different speeds downstream and upstream for asymmetric traffic. 13.13 FIBRE-BASED SYSTEMS There was a lot of talk of fibre to the home (FTTH) during the 1980s. However, fibre was fairly expensive and the pressure from the subscribers was modest. Figure 13.34 shows the dramatic cost reduction during the last few years. Since then many competing solutions have been developed, as seen from Figure 13.34. An increasingly popular fibre-based solution uses Ethernet in layer 2. It can also offer home access. X in FTTx may be basement, curb, home, office, radio base station and SO on. What is called fibre Ethernet systems benefit as well. 13.14 ETHERNET 95 % of all IP traffic utilizes Ethernet. All business offices use Ethernet. Virtually all home PCs have Ethernet. Public Ethernet is being built all over the world. Well-proven, mature and robust technology. Access Network Fibre is real Metropolitan fibre price erosion Estimated Metro annual Figure 13.34 The fibre cost development makes FTTx systems competitive Table 13.1 Cost comparison for equipment only Equipment Bandwidth Annual Band