Last Mile

Last Mile

The "last mile" or "last kilometer" is a phrase used by the telecommunications and cable television and internet industries to refer to the final leg of the telecommunications networks delivering communications connectivity to retail customers; the part that actually reaches the customer. Examples are the copper wire subscriber lines connecting telephones to the local telephone exchange, coaxial cable service drops carrying cable television signals from utility poles to subscriber's homes, and cell towers linking local cell phones to the cellular network. The word "mile" is used metaphorically, the length of the "last mile" link may be more or less than a mile. Because the last mile of a network to the user is also the first mile from the user to the world when he is sending data (such as uploading), the term "first mile" is sometimes used.

The last mile is typically the speed "bottleneck" in communication networks; its bandwidth limits the bandwidth of data that can be delivered to the customer. This is because retail telecommunication networks have the topology of "trees"; with relatively few high capacity "trunk" communication channels branching out to feed many final mile "leaves". The final mile links, as the most numerous and thus most expensive part of the system, are the most difficult to upgrade to new technology. For example, telephone trunklines that carry phone calls between switching centers are modern optical fiber, but the "last mile" twisted pair building telephone wiring can be up to 100 years old.

To solve the problem of providing enhanced services over the last mile, some firms have been mixing networks for decades. One example is Fixed Wireless Access, where a wireless network is used instead of wires to connect a stationary terminal to the wireline network. Various solutions are being developed which are seen as an alternative to the "last mile" of standard incumbent local exchange carriers: these include WiMAX and BPL (Broadband over Power Line) applications.