IN THIS ISSUE
January 2009
Vol 9 Issue 1

Feature Article
Frequency Coordination Considerations for the Design Engineer

Case Corner
ONE STEP AT A TIME: Diagnosing Earth Station Interference

Regulatory Rap
Microwave &
Satellite News

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Frequency Coordination Considerations
for the Design Engineer

by Greg Macey
Manager Microwave, Comsearch

Designing microwave networks that blanket urban areas involves a whole series of processes that must be effectively implemented in order for the overall project to be a success. Everything from the high-level overall traffic data routing down to the low-level placement of antenna mounting clamps must be accounted for. Lack of attention to any one area can cause delays or worse yet…a redesign.

  Although thoughts of frequency choice and availability occur at some point, it usually occurs quite late in the design process.

  The focus of this article is to identify some basic frequency coordination rules of thumb for the early stages of path/network design to help ensure success.

Rule # 1 Reconcile your Site Data

As you start to design a path, you may have multiple, conflicting sets of site coordinate data. Sources typically include one or more of the following:

• Certified site survey (1a or IIc)
• Non-certified GPS site survey
• Existing Antenna Structure Registration (ASR)
• Existing FCC call sign information
• 7.5 minute map data
• Google Earth

  There is no magic bullet here, but the certified site survey should be your most accurate data source for design purposes. The most common problem occurs with conflicts between the site survey, call sign, and/or the ASR when it comes time to license a path. The good news is that for FCC licensing there is a small amount of acceptable wiggle room.

  The acceptable tolerances between data sources for licensing are:

• Location: ±1 second on latitude and longitude
• Elevation: +0.5 meters or -1.5 meters

  If your discrepancies are outside this tolerance, then one or more of the data sources needs to be corrected to fall within the acceptable tolerances.

Rule #2 Be Aware of FCC Regulatory Restrictions

Overlooked FCC restrictions can delay or even prevent a microwave path from being turned on. Some basic knowledge of 47 CFR, Parts 1 and 101 is helpful. Consult your Comsearch coordinator if you have any concerns. We can quickly check a path design for compliance against approximately 100 key FCC rules.

  Some of the more common rules to keep in mind are:

• 18 GHz restrictions in a broad radius around the Washington, DC, and Denver, CO, areas
• Radio Astronomy Quiet Zone restrictions in Greenbank, WV, and Puerto Rico which could affect your ability to activate the system at the time of FCC Filing (known as Conditional Authorization)
• Areas within 56.3 km (35 miles) of the border are not eligible for Conditional Authorization
• Any FCC waiver request also removes the ability to get Conditional Authorization
• Certain frequency bands such as 23 GHz have very limited frequencies along with power and EIRP restrictions that would be available for Conditional Authorization

Rule # 3 Consider Environmental Frequency Congestion

Tall buildings within cities or isolated mountain peaks surrounding major cities tend to be a magnet for microwave sites. Also, if your survey report identifies nearby antennas and other towers, this could be a warning flag.

  This is not to say that you can’t get your 6.1 GHz path implemented out of a potentially congested site, but be prepared for possible antenna upgrade costs at a minimum. If you have concerns early in your design, call your Comsearch coordinator and we will gladly do a quick search of the area for microwave congestion. Although a quick radius search around your sites will not give you a definitive answer, it can serve as a barometer to determine if contingency designs should be considered.

  Quick radius searches also serve the purpose of identifying High/Low conflicts or “bucking” situations. A “bucked” site is one in which the transmit and receive frequencies at or near a site are on the same side of an FCC frequency plan. This means that the required frequency separation at the site is being compromised. This is a very undesirable situation because at a minimum, it can limit future frequency expansion around the site. At worst, harmful system interference can occur to one or more party's paths.

Rule # 4 Consider Intra-system Frequency Congestion

With an industry focus on increased bandwidth for 3.5G and 4G systems, the need for multiple carrier frequencies is also increasing.

  Here are some pointers that will help achieve your goals:

• Avoid excessive use of any single frequency band out of a hub, especially if the available frequency pool is limited, especially when you have paths concentrated with similar azimuths.
• Avoid using the same frequency band exclusively in a loop network if you have an odd number of microwave paths; otherwise you create a bucking situation as described above.
• Be informed of manufacturer’s sub-band limitations. Just because the frequency exists in the FCC rules, it doesn’t mean the manufacturer makes all of the FCC designated pairs. Also, there are specific rules for stacking channels depending on the radio manufacturer and model. Comsearch can assist you in this area.

Conclusion

Getting a network up and running on time and within budget is difficult enough without being told that you can’t get your frequencies. The steps listed above will greatly increase the chances of success.

  For more on our philosophies of frequency coordination and path design be sure to visit our web site or attend our free technical seminar on path design on May 4^th and 5^th.

ONE STEP AT A TIME:
Diagnosing Earth Station Interference

by Jim Branin
Principle Electrical Engineer, Comsearch

The most challenging of the tasks performed by Comsearch’s Field Group are Earth Station Diagnostic requests. We usually don’t “get the call” until the client has exhausted all the other resources at their disposal. These jobs can run the gamut from the simple to the exasperating. The most challenging are the “firsts.” These are the jobs where the problem encountered has not been seen before.

  Over the years, some of these firsts for Comsearch have involved interference into earth stations from:

• Aircraft radio altimeters
• Commercial microwave ovens
• Radar detectors in vehicles
• Cellular Bag Phones
• Airborne Warning and Control System (AWAC) emissions
• L-Band radars
• Sodium or mercury vapor security lights
• Air conditioner relays
• Small engine ignition noise
• Various automotive alarms

  Now these are somewhat a commonplace and at times are easy to diagnose. But as a first, they were quite challenging and found only after careful observation and experimentation.

  By far the most challenging of the earth station diagnostic jobs are the situations where the problem at the site is the result of multiple sources of interference. In most cases, the problem is identified in one to three days on-site, but there is always the exception.

  One of the most challenging of these jobs took two weeks to resolve. After identifying five sources of interference, the problem was finally resolved. Here is our story.

  We got a call from a major client, one of the larger TV networks, about a situation at one of their owned and operated stations in a major market.

  They had two earth stations assigned for network at the studio. One was on the ground in a very small gated parking lot, and the other was five floors up on the roof.

  Both antennas had a problem with “dribbling errors” (excessive error seconds throughout the day). The one on the roof also experienced occasional major disruptions during the day and severe interference hits every 90–120 seconds during the night. The antenna on the ground did not have the same periodic problem all night, but had major disruptions during the day and especially during prime time in the evening.

  Standard procedure for these diagnostic jobs is to perform a visual inspection of the earth stations and the environment.

  Both antennas had band pass filters in place. These are essential because the most common cause of interference into C-Band earth stations is from aircraft radio altimeters. Both antennas had acceptable signal strength and signal/noise ratios.

  We discovered that there were non-network C-Band antennas on the ground and on the roof that did not have band pass filters installed. It is essential for ALL C-Band earth stations to be filtered because failure to do so leaves the opportunity for an unfiltered LNA to take an interference hit from radio altimeters. This tends to produce spurious in-band emissions. The needed filters were shipped overnight and installed the next day. This eliminated some of the major disruptions during the day and night to both antennas. This was Fix Number One.

  During the first evening at the station, we discovered that an adjacent multi-level parking garage had several of its security lights malfunctioning on the top floor. Facility management was contacted the next day and the light bulbs were replaced a day later. This eliminated the 90–120 second hits during the night. This was Fix Number Two.

  The second day of testing revealed that there were multiple air conditioning units on the ground and on a mezzanine roof level that were producing contactor/relay broadband noise. This was the probable source of the dribbling errors in both antennas. The air conditioning contractor was contacted, and the relays were scheduled to be replaced over the next several days. When testing was continued the following week after these repairs were completed, the dribbling errors were eliminated. This was Fix Number Three.

  These three fixes had eliminated the problems for the antenna on the roof. The ground-mounted antenna still was taking major hits during the day (with no pattern) and would take major disruptions several times during prime-time every night.

  Since the parking lot was equipped with an automated gate, and since the gate was adjacent to the earth station, we decided to evaluate the opening and closing of the gate as a source of interference. The gate was opened by the use of hand-held transmitters used in the vehicles when approaching up an alley. These were tested and were not producing any spurious signals that would cause interference. The exit for the gate was not automatic. One had to press a button at window level on a pole by the gate. The gate relays were also tested to no avail.

  Then one evening while monitoring the system for disruptions, one of the ENG vans stopped in front of the antenna (to open the gate). The system took a major hit. It was discovered that the five ENG vans were all from the same manufacturer. This is significant because this manufacturer uses a buzzer (as in a relay/contact) to warn that the ignition key is in the vehicle when the door is opened. Since the window in the vans sits too high to allow one to push the button to open the gate, the operator has to open the door to push the button to open the gate. When the door opened in front of the antenna, the broadband noise from the buzzer caused interference into the system. All five ENG vans were retrofitted with electronic alarms to solve this problem. This was Fix Number Four.

  However, this was not the end of the problems. Every night during prime-time, the antenna on the ground would take several major interference hits. They were completely random in nature, being as close as fifteen minutes apart to more than an hour apart. Tracking the source of these events took another three nights. The event was very brief (less that a second or two) and very random. When captured on the test set, we identified it as broadband noise. Finally, the source was discovered to be a commercial dishwasher in the kitchen of a private club just to the south of the earth station. The unit was vented to the roof of the kitchen some 50' in front of the antenna to the south. When it was loaded with dishes and the door was closed, the operator would press the start button. The electronic board in the unit would then momentarily emit broadband noise. It would travel up the vent pipe to the roof and then be sensed by the earth station. The unit was replaced and the interference ceased. This was Fix Number Five.

  This multiple-source interference situation was one of the worst, but is a good reference point when addressing interference problems—each one has to be resolved one at a time.

  Luckily the vast majority of these diagnostic cases are resolved in less than three days on site.

  Each time a call comes in for an Earth Station Diagnostic Measurement, and we have listened to a description of the problem, the tendency may be to fit it into one of the scenarios we have seen before. But as experience has taught us, “you never know for sure until you get there.”

  Then there is the situation that involved the two ducks and the cat.

  But that's another story.

MICROWAVE

3650–3700 MHz Radio Service—Update—As of December 31, 2008, there were 596 Nationwide Licenses granted for this service. From this group of licensees, 112 companies have filed deployment details for a total of 817 sites. The FCC information site for this service can be found here 3650–3700 Radio Service Details.

  The Comsearch White Paper on the impact of this service to adjacent channel Earth Station Operators can be found here 3650–3700_MHz_Interference_into_CBand_ES.pdf.

Call Center Established for DTV Issues—DOC-288049A1.pdf

DTV Transition—The FCC Adopted Analog Nightlight Program for Emergency and Digital Transition Information after the DTV Transition – (Dkt No 08-255, FCC No. 09-2) FCC-09-2A1.pdf FCC-09-2A2.pdf FCC-09-2A3.pdf FCC-09-2A4.pdf FCC-09-2A5.pdf FCC-09-2A6.pdf

698–746, 747–762 and 777–792 MHz Bands Service Rules—FCC defines service rules to establish a nationwide, broadband, interoperable public safety network. (Dkt No 06-150, 06-229, FCC No. 08-230) FCC-08-230A1.pdf FCC-08-230A2.pdf FCC-08-230A3.pdf FCC-08-230A4.pdf FCC-08-230A5.pdf FCC-08-230A6.pdf

700 MHz Band (Auction 73)—FCC Grants Licenses (DA No 09-8) DA-09-8A1.pdf DA-09-8A2.pdf DA-09-8A3.pdf DA-09-8A4.pdf DA-09-8A5.pdf DA-09-8A6.pdf

809–809.5/854–854.5 MHz Band Licensing Procedures—(DA No 08-2810, Dkt No 02-55) DA-08-2810A1.pdf

896–901 MHz and 935–940 MHz Band Rule Changes—FCC amends Rule Part 90 to provide for flexible use. Retained site-based licensing for the 900 MHz B/ILT band. (Dkt No 02-55, 05-62, FCC No 08-244) FCC-08-244A1.pdf

Unlicensed Devices Below 900 MHz and in the 3 GHz Band—FCC Adopts Rules For Unlicensed Use of Television White Spaces (Dkt No 02-380, 04-186, FCC No 08-260) FCC-08-260A1.pdf FCC-08-260A2.pdf FCC-08-260A3.pdf FCC-08-260A4.pdf FCC-08-260A5.pdf DOC-286566A1.pdf DOC-286566A2.pdf DOC-286566A3.pdf DOC-286566A4.pdf DOC-286566A5.pdf DOC-286566A6.pdf

Prototype TV White Space Devices—The FCC’s Office of Engineering and Technology (OET) released a report entitled Evaluation of the Performance of Prototype TV-Band White Space Devices. (DA No 08-2243, Dkt No 04-186) DA-08-2243A1.pdf DA-08-2243A1.pdf DA-08-2243A10.pdf DA-08-2243A11.pdf DA-08-2243A2.pdf DA-08-2243A3.pdf DA-08-2243A4.pdf DA-08-2243A5.pdf DA-08-2243A6.pdf DA-08-2243A7.pdf DA-08-2243A8.pdf DA-08-2243A9.pdf

AWS-3 Interference Tests—OET releases analysis (DA No 08-2245. Dkt No 04-356, 07-195) DA-08-2245A1.pdf DA-08-2245A2.pdf

Application Fees Adjusted—The FCC modified the Part 1 rules to adjust its fees for processing applications and other filings. (Dkt No 86-285, FCC No. 08-209) FCC-08-209A1.pdf

SATELLITE

FCC Approves Globalstar Licensee LLC Application for Modification of License for Operation of Ancillary Terrestrial Component Facilities
The FCC granted in part a request by Globalstar LLC to modify its authority for an ancillary terrestrial component (ATC) to be operated in conjunction with the Globalstar Mobile Satellite Service (MSS) system. Specifically the FCC modified Globalstar's license to permit use of the WiMAX air interface protocol. In doing so, the FCC found that an interim waiver of certain ATC “gating criteria” and technical rules will serve the public interest by permitting Globalstar and its spectrum lessee, Open Range Communications, Inc. (“Open Range”), to commence deployment of a broadband service consistent with a $267 million loan commitment from the Department of Agriculture’s Rural Development Utilities Program.

Globalstar requests that its license be modified to authorize ATC operation with air interface protocols other than the previously authorized cdma2000. Specifically, Globalstar requests authority to use four additional protocols: Wideband CDMA (“WCDMA”), Time Division CDMA (“TD-CDMA”), Long Term Evolution with Frequency Division Duplex (“LTE-FDD”), and WiMAX with Time Division Duplex (“WiMAX-TDD”).

Globalstar plans to collaborate with one or more “terrestrial partners” to offer MSS bundled together with ATC broadband service. To that end, Globalstar has entered into a spectrum lease agreement with Open Range. Under the terms of the agreement, Open Range would construct and operate an ATC network using S-band spectrum leased from Globalstar. The two companies would provide MSS/ATC service to customers equipped with dual-mode handheld terminals, Open Range providing the ATC service and Globalstar providing the MSS component.
http://hraunfoss.fcc.gov/edocs_public/attachmatch/FCC-08-254A1.doc

Inmarsat Request to Streamline Licensing of L-band Licensing of L-band Mobile-Satellite Service Terminals Using Inmarsat Satellites as Points of Communication
The FCC issues order, to make a change in the way in which to specify points of communications in licenses permitting mobile-satellite service (MSS) and fixed-satellite service (FSS) earth stations communicating with Inmarsat satellites in the L-band in the United States. Specifically, they establish a list of Inmarsat satellites approved to serve the United States in the L-band. The list (the “ISAT List”) will include Inmarsat satellites that have been found to meet the Commission’s legal, technical, and policy requirements to access the U.S. market. The ISAT List will allow earth station licensees and applicants to seek authority to communicate in the L-band with satellites based upon the satellite listing on the ISAT List, rather than having to seek authorization to communicate with Inmarsat satellites on a satellite-by-satellite and orbital-location-by-orbital-location basis. The FCC hopes this will serve the public interest by eliminating duplicative and repetitive filings and by facilitating the more rapid deployment of satellite services to U.S. consumers. http://hraunfoss.fcc.gov/edocs_public/attachmatch/DA-08-2323A1.doc

Streamlining and Other Revisions of Part 25 of the FCC Rules
In the Eighth Report and Order, the FCC further streamlines the Commission’s non-routine earth station processing rules, by adopting a new earth station procedure that will enable the Commission to treat more applications routinely than is possible under the current earth station procedures. The Commission has determined that satellite facilities provide a competitive platform for delivery of broadband services, which is especially well suited for extending these services to rural and unserved areas. In other words, satellite services employ cost-effective technology to serve communities with low penetration rates, especially those in remote areas. In addition, the threat of competition from satellite-based broadband Internet access and other alternatives will stimulate deployment of broadband infrastructure, including more advanced infrastructure such as fiber to the home. Moreover, the number of consumers who receive their broadband connection through satellite or other wireless technologies will continue to increase as new satellite services are launched.

  Specifically, the order adopts an off-axis equivalent isotropically radiated power (EIRP) envelope approach as one method for applicants to apply for Fixed Satellite Service (FSS) earth station licenses in the conventional C-band and Ku-band. The Commission proposed off-axis EIRP envelopes for FSS earth stations based on recommendations from satellite industry commenters in an earlier phase of the proceeding.

  This off-axis EIRP approach gives earth station applicants the flexibility to reduce their power levels to compensate for a small antenna diameter. Using these envelopes as criteria for licensing should enable applicants to license more earth station applications routinely, without increasing the likelihood of harmful interference to adjacent satellite operators or to terrestrial wireless operators. http://hraunfoss.fcc.gov/edocs_public/attachmatch/FCC-08-246A1.doc

Comsearch launches www.3650search.com, a free online tool for performing 3650 MHz searches
www.3650search.com is designed to help licensees efficiently manage their spectrum usage while protecting incumbent users in the band. The tool leverages the FCC’s 3650 MHz ULS data and is augmented by our own databases to provide critical information about:

• nearby licensed 3650 MHz systems,
• co-channel and adjacent channel earth stations,
• federal radio location stations and,
• Government radar systems.

Comsearch to launch the next generation of iQ·link®
iQ·link is Comsearch’s flagship fixed network design and management software tool for microwave point-to-point and point-to-multipoint backhaul. As networks continue to expand and add capacity, and wireless microwave continues to be a popular, cost-effective choice for operators, we decided that it was time to breathe new life into our 18 year old spectrum manager. Building on a proven foundation, Comsearch has energized iQ·link for the future with iQ·link®XG 9.0, which represents a complete re-architecture of the product.

  iQ·linkXG key improvements include:

• A true cross-platform framework. iQ·linkXG is now a fully cross-platform product and will be offered and supported for Windows in addition to the stable, proven SUN Solaris UNIX platform.
• A modern, attractive User Interface. An always technically-comprehensive user interface is now presented in a modern, pleasing way with an appropriate use of color, group boxes and tabs.
• Improved user experience with enhanced screen layouts and functionality. We listened carefully to the industry and the needs and requests of our customer base and focused our efforts on exceeding expectations. We also took great care to make sure the product remained familiar to existing users, while appearing fresh and modern to all users.
• Powerful GIS engine. The engineer’s ability to view and analyze the network graphically has been significantly enhanced with the development of a powerful, new GIS engine.
• Integrated online help text. On-line help text is available through the use of tool tips that appear as your mouse moves over certain fields and through “What’s—This?” text that is displayed when invoked by the user.
• Improved ability to add new, more advanced features. iQ·linkXG’s new cross-platform architecture completely separates the User Interface from the back-end engineering code. This significantly increases our ability to bring new, advanced features to market quicker than ever before. It also allows user interface designers to concentrate on the user interface and experienced programmers to focus on the engineering code.

SpectrumView^SM
Comsearch, a CommScope Company, brings you SpectrumView^SM—a simple, yet comprehensive look at spectrum holdings for any wireless carrier in any wireless market nationwide. In the last two auctions alone, over 200 licensees acquired close to 2000 licenses for AWS and 700 MHz spectrum. Combine that with spectrum holdings for other services such as Cellular, PCS, and WCS, and the spectrumscape is extraordinarily complicated. SpectrumView cuts through the clutter to give you a clearer picture of who has what spectrum where.

  SpectrumView identifies potential partnerships and competitors for wireless telecom licensees. County boundaries are the basis for all FCC license areas, so we identify each carrier at the county level or partial county level, then aggregate that back up to the appropriate market area. We also sum up the amount of spectrum per carrier as well as population covered by each license. For partial counties, we calculate the percentage of geographic area and percentage of population covered by the license. We take into account leases recorded with the FCC, ownership changes, frequency disaggregation, and market partitioning. Detailed research is performed on each licensee name to determine the true operating company.

  For more information on Comsearch's SpectrumView, please click here or call 1-800-318-1234.

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