s problematic when cable bundles are shared between telecommunication companies and imply a need for some form of spectral policing that in turn implies a need to measure power spectral density across all utilised frequencies. So in many respects copper is similar to wireless. As data rates have increased power spectral density has increased and this is increasingly causing user-to-user interference that has to be actively managed. The use of OFDM allows an individual user's bandwidth to be subdivided down into frequency subcarriers that are orthogonal to each other, or in other words theoretically at least do not interfere with each other. Each individual subcarrier has a relatively low symbol rate that minimises problems with intersymbol interference. Different users are, however, not orthogonal to one another and the result is an increasing amount of crosstalk. This complicates access economics. Supplying a high data rate service to an individual user, for example a VDSL2 connection has a direct cost, for example a VDSL line card and modem. This cost can be easily accounted. However, implementing the service will have a direct impact on all other users' cosharing the delivery medium. This cost is not easily accountable and the users who suffer service degradation may be supported by another service provider. 22 A T1 circuit in North America, Japan or Korea is a full duplex 1.544 Mbit/s circuit typically carrying 24 64-kbit channels. E1 is the equivalent used in the rest of the world with a line data rate of 2.048 Mbit/s downstream and 2.048 Mbit/s upstream split into 32 time slots. Making Telecoms Work The Copper Conundrum - the Disconnect between Competition Policy and Technical Reality Thus, we have a conundrum. The copper access network has been progressively unbundled on the basis that allowing competing providers to share access bandwidth encourages market effi- ciency. Unfortunately, this has coincided with technology innovation that makes this cosharing less rather than more efficient unless firm spectr