Cutting Edge Instructional Television broadcast technology from 1970.
Courtesy Belleview College, Belleview, Washington.

The Broadband Radio Service (BRS), formerly known as the Multipoint Distribution Service (MDS), and the Educational Broadband Service (EBS), formerly known as the Instructional Television Fixed Service (ITFS), are located in the 2.5 Gigahertz band. This spectrum band was initially configured with interleaved (arranged in alternate layers) channels (6 MHz each) to be used for high-power transmission of analog television signals from fixed (as opposed to mobile) locations. The ITFS channels are at the top end of the Ultra High Frequency (UHF) band that is used for commercial television.

In 1963, when this band was established by the Federal Communications Commission (FCC), all of the 30 channels were allocated for “instructional television” stations operated by educational institutions and nonprofit organizations, including religious broadcasting stations. ITFS channels were utilized primarily to broadcast “distance learning” programming. However, the spectrum was not widely used, since most educational institutions and nonprofit organizations did not have the financial resources to construct and operate a closed circuit television station.

In the 1980s, the FCC reallocated some of the ITFS channels to commercial wireless operators that needed spectrum to compete with conventional cable television systems. ITFS spectrum was the reorganized into five channel groups. Each “channel group” has 4 microwave channels, for a total of 20 channels. To create the MDS band for commercial operators, the FCC reassigned and combined 10 former ITFS channels (the E and F Groups) with 3 other microwave channels, for a total of 13 channels.

At that time, the FCC instituted new regulations allowing the educational licensees to lease a portion of their broadcast spectrum to wireless operators. Under a typical lease agreement, the wireless operator agreed to construct and operate distance learning channels for the educational licensees, in exchange for the right to use the “excess” (unused) capacity on the ITFS channels in the commercial wireless cable system. This new regulatory paradigm dramatically increased the number of applications for ITFS spectrum, but “wireless cable” could not overcome its lack of channel capacity as compared to other subscription television services. The rural and low population density areas that wireless cable was intended to serve were eventually captured by satellite-delivered television services. Wireless cable could not compete with conventional cable in urban areas.

The ITFS/MDS band plan was initially devised to transmit either one-way video service to students, in the case of an educational institution, and subscription television service, in the case of a wireless cable operator. The authorized use for the channels was limited to one-way analog high power transmissions from a single high power omni-directional antenna, like regular commercial television broadcasts. The reason that the channels were arranged in “interleaved” (arranged in alternate layers) groups was to minimize harmful electronic interference from the transmissions of other ITFS or MDS licensees. The alternating assignments for each channel group (such as A1, B1, A2, B2, A3, B3, A4, B4) resulted in licensed frequencies that were not contiguous spectrum. This band plan was not suitable for other later developed technologies, such as data transmission or broadband access services used in low power two-way digital cellular networks.