How does DSL Internet work on Chebeague?
We receive bandwidth via a microwave transmission link between a high building in Portland (One City Center) and a receiver on the West End of Chebeague Island. From there, the bandwidth is transmitted by fiber optic cable to a central Feeder-Distribution Interface (FDI) mounted on two poles near Calder's Clam Shack, which provides the origin for DSL service on the Island.
Digital subscriber line (DSL) is a family of technologies that provide internet access by transmitting digital data over the wires of a local telephone network. In telecommunications marketing, the term DSL is widely understood to mean Asymmetric Digital Subscriber Line (ADSL), the most commonly installed DSL technology. Chebeague.net employs ADSL2+ technology, which is the most recent commonly deployed DSL implementation.
The data bit rate of consumer DSL services typically ranges from 256 kbit/s to 40 Mbit/s in the direction to the customer (downstream), depending on DSL technology, line conditions, and service-level implementation. In ADSL, the data throughput in the upstream direction, (the direction to the service provider) is lower, hence the designation of asymmetric service.
How did wireless Internet work on Chebeague?
We began with wireless Internet service in 2006 and have almost completely phased out this service in favor of the faster, more reliable DSL service described above. But for the sake of history, here's how wireless works. Or worked.
chebeague.net installed high-speed T1 lines to the Chebeague Inn, the Chebeague Recreation Center, the Chebeague Boat Yard and to the CTC Parking Lot on Cousins Island. Previously, the Library and the school were the only locations that had T1 lines and it literally took an act of the Legislature to install those lines, which are dedicated to library and school use only.
Once bandwidth became available, the challenge was to distribute it across the Island. This was accomplished through antennas at our four T1 locations. We also "chained" the signal to more remote parts of the Island.
From these vantage points we hoped to make service available to all homes on the Island using 900 MHz non-line-of-sight (NLOS) "last mile technology." This meant that the signal would be successfully transmitted through Chebeague's dense foliage and deliver between 600 and 800 kbps, both upload and download, with speeds as high as 1.5 mbps. However, neither of these goals were met with wireless service due to a combination of demand for more and more bandwidth and the difficult topography of the Island.
Homes close to a transmitter or repeater were equipped with indoor antennas to receive the signal and modems to pass it through to home computer(s). More distant areas used an outdoor antenna to bring in the signal. chebeague.net made every effort to make broadband Internet service available to every home and business on the Island.
With the availability of DSL service, we first linked to our wireless antennas to provide more bandwidth to the wireless service, replacing the old T1 lines. As we complete the deployment of DSL, we will phase out the wireless service entirely.