While doing some research on how capacity will grow in fixed line and wireless networks in the future I stumbled over the following thing right in my neighborhood: Future bandwidth increases on the last
mile to the subscriber come with an additional cost in comparison with today’s
standard ADSL or ADSL2+ deployments because of extra hardware that has to be installed close the the subscriber.
For ADSL2+ the DSLAM is usually installed
in the telephone exchange and the cable length to the subscriber can be up to 8
km for a 1 MBit/s service. For VDSL, which offers data rates of 50 MBit/s
in downlink, the cable length must not exceed 500m. Thus, DSLAMs can no longer
be only installed in central telephone exchanges but equipment has to be
installed in cabinets on the street. The cabinets themselves are quite large (about half the size of a GSM or UMTS base station),
require power, active cooling, and create noise. For the installation
of the cabinets earthworks are necessary to lay the additional fiber
cables required to backhaul the data traffic. The picture on the left shows a VDSL DSLAM cabinet that
has been installed alongside a ‘legacy’ small telecom cabinet as part of the current VDSL build out in my region.
To connect a
new subscriber a technician is required to manually rewire the customer’s line
to one of the ports. Different sources currently
specify the maximum capacity of such cabinets from about 50 to 120 VDSL
ports. To support 500 VDSL connections per km², several cabinets are thus
required. I wonder what happens when 5 different companies put such DSL ‘base stations’ in place!?