In a telecommunications context, the last mile typically refers to the final infrastructure used to deliver various services to a customer. A number of different industries use the term to refer to items such as telephone service, cable, and the Internet. This last leg can consist of hard wired systems like telephone wires, cable, or fiber optics, or it may include some wireless components. It is not uncommon for the last mile to actually be a much longer than one mile in rural areas, as the term refers to a concept and not a physical distance. Areas that use the metric system may tend to use the term last kilometer, and the term first mile or kilometer can refer to essentially the same thing.
The last mile is often the most vulnerable component of the service infrastructure, and may limit the type of services available in a particular location. In the case of large businesses, the last mile for telephone service will often include a special trunk line that is capable of carrying multiple phone conversations at once. These are often vulnerable to damage from rising groundwater or from being dug up.
Many telecommunications companies use optical fiber in their infrastructures, though the last mile may still be comprised of copper twisted pairs. Internet speeds in particular may be impaired if fiber optics are not present in the last mile. The increased bandwidth offered by optical fiber may also allow for other services such as digital television that twisted pairs cannot be used for.
When the last leg of a service infrastructure includes a wireless component, it may be referred to as a mobile mile. Systems like this may be useful in rural areas, where the last mile sometimes requires a significant infrastructure investment to service a relatively limited amount of potential customers. Wireless components can suffer from poor signal to noise ratios, potentially reducing their effectiveness. Various technologies may be involved in systems like these, including Wi-Fi™, cellular networks, and radio waves.
Other alternatives to fixed and wireless infrastructures also exist. Worldwide Interoperability for Microwave Access (WiMAX™) is a technology that can take the place of traditional last mile systems, delivering broadband Internet connectivity over limited areas. Broadband over Power Lines (BPL) is another alternative. BPL uses existing infrastructure in the form of power lines to deliver broadband service. While this has the benefit of not requiring additional costly infrastructure to be built, it may interfere with certain other broadcast spectrum devices, such as those used by amateur radio operators.