While microwave communications systems have been around for some 50
years--serving as the backbone of the nationwide telephone network for
much of that time, and as the medium for satellite transmission and
private networks from some 20 years--in many ways its capabilities are
only beginning to be tapped.

Satellite systems are pushing into higher regions, with the Ku-band
(14/12 GHz) and experiments looking at the still higher Ka-band of 30/20
GHz (see NASA story, page 88). Another offspring of telecommunications
competition that's making heavy use of microwave is bypass.

The name of the game is intercity transmission, a market
that's expected to reach about $65 billion by 1990, approximately
double what it was in 1980.

Earlier this year, Chicago-based Arthur Anderson & Company
released the results of an extensive study, "New Directions in
Telecommunications." Among its many subject areas was the hot
intercity market. According to its findings, bypass networks will grow
significantly. The number of US organizations using private or shared
bypass networks in 1980 was put at two percent, but it will grow to
nearly 11 percent by 1990. Microwave, copper cable and fiber optics will constitute the largest portion of intercity communications
capacity, with 29, 23 and 21 percent market shares, respectively, says
the study.

Two of the engineer panels participating in the study, however,
disagreed as to which medium will lead intercity capacity during the
1980s. The transmission engineer panel thinks it will be microwave
transmission with 34 percent of capacity in 1990, followed by fiber
optics with 25 percent and copper cable with 21 percent. The
manufacturer engineer panel projects copper cable (25 percent) and
microwave (24 percent) will lead, followed by fiber optics and
satellites, both with 18 percent of capacity.

While on the subject of bypass, a recent study from International
Resource Development of Norwalk, Connecticut sees bypass costing
telephone companies perhaps five percent of their revenues. According to
IRD, large corporations with communications expenditures exceeding $50
million annually are the most likely candidates to implement a bypass
system. "Likewise, the interexchange carriers such as AT&T,
MCI, GTE, SBS and others are also planning bypass technologies to avoid
using the local exchange plant for access to their long-distance
networks. But the most intriguing part of the bypass issue is that some
of the divested BOCs are also considering or implementing bypass systems
and are bypassing themselves." The Key to Bypass

According to the report, entitled "Telecom Bypass
Markets," satellite communications, through the widespread
deployment of domestic satellites and the development of satellite
technology to increase the use of satellite capacity and develop new
services, will be the key to bypass techniques used by large
corporations and other telcos for bypass. Private business satellite
networks provided by SBS, American Satellite, RCA and Western Union are
enhancing their local distribution capabilities, and private satellite
networks such as the OlympiaNet project open up the market for shared
tenant services."

The study adds, "Private microwave represents the other
steadfast threat to the local telephone company, having been used for
some 20 years already. Private microwave in the relatively lightly used
18 and 23-GHz frequency ranges will be a most attractive alternate for
companies seeking to lower communications costs, because the private
microwave suppliers have the years of experience behind them that other
bypass suppliers lack."

Some of the private microwave users have more than a little to
think about, thanks to the direct-broadcast satellite service. Although
most of the major proposed participants pulled out at the eleventh hour
when it came time to ante up for their expensive plans, the die had
already been cast with the allocation of spectrum for DBS.

This past August, the FCC affirmed its earlier decision to make
available spectrum at 13 and 6 GHz to accommodate the 12-GHz licensees
being displaced by DBS. In the same action, the commission clarified
actions with respect to the 18-GHz channeling plan. In an order
released in September 1983, the FCC established an allocation in a
segment of the 18-GHz band (18.36 to 19.04 GHz) for use by private and
common carrier Digital Termination Systems (DTS) and by private, common
carrier and broadcast auxiliary point-to-point operations. It also
allocated 10.55 to 10.68 GHz, previously allocated exclusively for
common carrier DTS, for use by private DTS and by the private
operational-fixed service for point-to-point operations.

A commission order provided spectrum in the 12.7 to 13.15-GHz and
6.525 to 6.875-GHz bands for the existing 12-GHz (12.2 to 12.7-GHz)
private fixed service users who must vacate for DBS. It also completed
the allocation of the remaining segments of the 18-GHz band (17.7 to
19.7 GHz) for private, common carrier, broadcast auxiliary and cable
operations.

Reconsideration petitions for the two proceedings were seen as
interrelated, so the FCC addressed all in a single order this past
August--DTS, 18-GHz band allocation, 18-GHz technical standards and
12-GHz reaccommodation procedure.

The FCC affirmed its previous action to allow private DTS
operations on the four 10.6-GHz channels previously allocated to common
carrier systems. The channeling plan for the 18-GHz band is to be used
to support terrestrial fixed point-to-point and point-to-multipoint
operations; the band is also co-equally shared with the fixed-satellite
service. The FCC modified the channeling to support contiguous spectrum
for cable television operation and to have a uniform transmit/receive
separation for the narrowband channels. However, a requested 120-MHz
transmit/receive separation is not provided for in the revised
channeling plan. The currest waiver to market equipment not complying
with the channeling plan is extended for two years from the release of
the order.

Concerning the technical standards adopted for the 18-GHz band, the
commission postponed the implementation of the 1.0 b/s per Hertz spectrum efficiency standard until December 1, 1988, so manufacturers
will not be required to redesign existing equipment in order to meet the
0.6-b/s per Hertz interim efficiency standard.

Those 12-GHz band users being displaced by DBS have a variety of
choices, but there is no "best choice" that applies in every
case, according to Comsearch, a Reston, Virginia-based firm that
provides path design, frequency coordination, system integration and
other engineering services. It points out that these users have until
September 1988 to relocate their service to the 6, 13 or 18-GHz bands.
"In effect, the FCC gives 12-GHz users a choice of fitting
themselves into relatively crowded bands (6 and 13 GHz) or moving to a
new band with significantly different transmission characteristics (18
GHz)." Good News/Bad News

According to Comsearch, the 13-GHz band (12.7 to 13.25 GHz) appears
to offer a "no-problem" alternative from a technical
standpoint. "In fact, some existing 12-GHz radio equipment can be
made to work in 13-GHz frequencies with minor modifications. Some
waveguides and antennas may work with no modification at all. The bad
news is that there are already over 83,000 links licensed on the 13-GHz
band for the Cable Antenna Relay Service (CARS)."

Looking at the 6-GHz band, Comsearch says it's less-desirable
than 13 GHz because it requires new investment in transmission
equipment, and because 10-MHz bandwidths are the maximum allowed without
a waiver. In addition, the narrow bandwidth limits 6 GHz to non-video
applications. It says that a major potential problem with 6 GHz is its
larger path clearance needs, which may demand complete re-engineering of
the path.

As for 18 GHz, Comsearch says that if rapid or substantial growth
is expected for the system, the 18-GHz band (17.7 to 19.7 GHz) may be
the best choice for a move. "In some cases, it may be the only
choice, if suitable 13-GHz or 6-GHz channels are not found. The
drawbacks of 18 GHz seem substantial: shorter transmission paths, higher
construction costs and less-developed technology. The advantages are an
essentially open band (under 200 licensees) and the opportunity to use
any of several bandwidths (up to 80 MHz)."

Well, no one ever said it would be easy. As in virtually all other
areas of telecommunications today, you make the best choices with the
best information available--then take your chances.

Comsearch points out that timing is all-important, noting that
"The FCC has given no special priority to displaced 12-GHz users
moving to 13 GHz or 6 GHz. After September 1988, all rights to move
these bands expire. As a result, it is important to begin evaluating
the alternatives as soon as possible."

One of the bright spots is that there is an abundance of microwave
equipment and services available today. Following the feature articles
in this section describing some current uses of microwave technology is
a roundup of presently available vendor offerings.

COPYRIGHT 1984 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.