FCC Spectrum Management Mistakes: The “Sweet Sixteen” List – Part 2 Hear No RF Evil - See No RF Evil |  |
| FCC Spectrum Management Mistakes: The “Sweet Sixteen” List – Part 2 Posted: 27 Oct 2011 02:16 PM PDT
6. Nextel (1990s). Back when it all began they were known as "Fleetcall," but their real intention became apparent with the re-naming of the company after a few years. Their mission: to construct a new wireless dispatch/telephone-interconnect network that, to the uninitiated consumer, would appear to be "cellular telephone" service. In reality, however, Fleetcall attempted to do this using Private Land Mobile Radio (PLMR) [i.e., "two way radio"] allocations and frequencies, and for much of its history it remained a private carrier, not a (cellular) communications common carrier. Using its heavy financial and legal resources, Fleetcall overwhelmed the FCC and ran, almost unchecked, willy-nilly through the (then-thriving) PLMR radio industry. Fleetcall did not hold allocations of contiguous frequency blocks in individual markets, under single system licenses, as do the cellular/PCS licensees. Every licensing action Fleetcall took involved individual (narrowband) operating frequencies at specific locations. Thus battling Fleetcall was equivalent to fighting an entire ant farm simultaneously. And in that Fleetcall's TDMA digital operations were on frequencies that were interspersed with the analog FM frequencies of Public Safety, Land Transportation, and other private licensees, co-existence problems did frequently result. When such problems effectively shut down geographically- and frequency-proximate Public Safety wireless dispatch networks, the affected police chiefs, sheriffs, and fire chiefs "were not amused." Nor was the FCC of much help, as they did not have the staff to handle these large numbers of issues. Eventually, however, the advance of technology caught up with what was by then Nextel (later to be acquired by Sprint). Nextel's individual narrowband TDMA channels would not permit the rich feature mix that the kind of wideband technologies (CDMA, adopted by Sprint, and GSM) used by the true cellular/PCS carriers could offer. Nextel could not participate in the emerging advanced cellular markets, since the new technologies required dedicated wide-band radio channels. So Nextel decided to create its own individual wide-band channels, again in the PLRM spectrum, by "relocating" the frequencies for all the other licensees to one end of the allocated band, and keeping the (now-contiguous) other end for its exclusive use. And thus began the 800 MHz "rebanding" proceedings, which "sputtereth along unto this very day!" The relocations are very expensive, highly contentious, lack a definite FCC leadership presence and, along with various other mangled FCC initiatives, have left the private Land Mobile world (and especially the important Public Safety contingent) in shambles. Entire doctoral dissertations could (and probably should) be written on this single FCC regulatory failure. Available space here cannot do justice even to the engineering aspects. {Disclosure here: During this period, LBA provided extensive consulting services to Fleetcall and NEXTEL, and continues to provide services to Sprint.} 7. "900 MHz" (1990s). This is one most readers won't know about unless they have had specific reasons to establish operations on 900 MHz. Over the course of years the entire non-governmental 900 MHz band (from 898 to 960 MHz) was allocated out by the FCC to various kinds of services and users, without any apparent long term vision or overall plan. Ultimately there were 900 MHz high-powered licensed users, low-power licensed users, and low-powered unlicensed users, all jumbled together while trying to operate. Some of the spectrum was also co-opted by the military.  Motorola 900 MHz Paging Transmitter As examples, low-powered 900 MHz Multiple Address Systems (licensed, two-way) operated in close proximity (often both in frequency and in geographical location) to high-powered digital paging system base stations (licensed, one-way). High-powered Automatic Vehicle Location beacon transmitters (licensed, one-way) shared spectrum with low-powered licensed and unlicensed users such as consumer wireless devices and Amateur radio. Almost everyone was unhappy almost all the time. The overall spectrum management effort was so badly botched that an FCC middle level manager, sitting at his desk in M Street, admitted "We really blew managing that band!" {Disclosure here: During this period, LBA provided consulting services to hundreds of 900 MHz paging licensees.} 8. Amplitude Compandored Single Sideband [ACSB] (early 1990s). This is an interesting failure, even if not a terribly major one. At the beginning of the 1990s the FCC was worried about a growing shortage of spectrum that could be used for PLMR operations (i.e., private dispatch, Public Safety, land transportation, etc.). In major metropolitan areas almost all the available VHF/UHF operating channels had already been allocated and, in the days prior to the mass adoption of mobile telephone service, the demand for private "two-way mobile radio systems" continued to increase.  Positive Train Control – Finally, a 220 MHz Application The shortage was exacerbated in part because of the relatively large occupied bandwidths (~ 20 kHz) used by land mobile radio's analog FM emissions mode of that time, and in part because of historical FCC frequency allocation policies. In the past the FCC had permanently allocated specific operating frequencies to various different classes of users (i.e., Public Safety, Local Government, Business, Land Transportation, etc.) as part of their authorizing Rules. However if a particular frequency, allocated for example to an individual railroad, did not have an authorized user of that class or licensee in a particular location, that frequency often went unused. Repeated FCC field spectrum utilization studies documented the vacancies in the midst of general need. Prompted by equipment manufacturers, the FCC set up a new emissions mode, together with a hitherto "unused" band on which to operate: Amplitude Compandored Single Sideband (ACSB) on the new 220 MHz band. The engineering idea was to use the (low occupied bandwidth) of single sideband emissions modes (successfully used in High Frequency band voice communications), but modified for land mobile needs. The modifications included not entirely eliminating the RF carrier but rather allowing a 'vestigial" carrier to remain to serve as a synchronizing signal for the transmission, and special speech-processing for the audio to improve the S/N ratio. The "new" band was 220 – 222 MHz (purloined from the Amateurs), and the format was the traditional PLMR trunked mobile/base station/repeater system operating on duplex pairs of frequencies. The land-rush was on, with a one-time "application window" and essentially no-cost system licenses for the winners (in the era prior to "spectrum auctions"). But the technology proved unpopular with the end-user public, especially when compared to the quality of the existing analog FM systems and to the emerging cellular telephone service. Within just a few years the new initiative had largely collapsed. Later the FCC would move into other spectrum-packing techniques for the PLMR service, and eventually the loss of VHF frequencies to the Amateurs was partially compensated with access to other frequencies. {Disclosure here: During this period, LBA provided consulting services to many 220 MHz licensees, and its principals hold (and still hold) 220 MHz licenses.} 9. Broadband over Power Lines, [BPL] (early 2000s). A brilliant FCC policy initiative intended at a minimum to make some sort of beginning on the developing problem of lack of universal broadband access for the citizens of the US (see below). "Do it now, do it cheap, and regulate your way around the laws of physics" was the approach. The concept was to stuff digitally modulated RF carriers down existing public-utility service pathways into every building in the country (almost!). Unfortunately the land-line telephone network was already in use in part for data communications, and the existing water and natural gas pipes didn't seem especially promising for the communications task, so it fell to the electrical power lines to do the job. But first two minor physics constraints had to be "regulated out of existence."  BPL Deployments Ca. 2005 Power conductors and networks designed to be efficient at 60 Hz aren't particularly efficient at transporting the HF band RF carriers used by the proposed BPL systems. Line and transformer losses are high and transporting usable data signals over long distances is difficult. Second, if HF carriers can indeed be made to travel through the power distribution network, they will inevitably radiate EM fields from the (unshielded) electrical distribution lines, which are themselves multiple wavelengths-long antennas at the RF frequencies in use. That physical process is formally known as "radio," and the result of the process as "signal jamming." All proximate users of HF radio systems would be placed in jeopardy by large BPL networks as they blanketed major metropolitan regions. Ultimately this "do it cheap" expensive solution mostly died a natural death; however it has returned in a smaller, modified format as "home power line networking," a quick and dirty alternative to Wi-Fi and Ethernet home digital networks. The UK is now experiencing its first RF spectrum pollution problems from this stinker. 10. "Noise temperature" (early 2000s). This concept didn't get much publicity, and mercifully it didn't last long either. But yet, as had happened previously, it reappeared at a later time. The basic concept was that unregulated low power communications activities could be "dropped in" on top of licensed RF operations in a geographical area and could lawfully continue to operate until they began to create interference. The recollection is that this "field experiment" would occur primarily in the fixed, point-to-point microwave bands. Existing, licensed equipment would have to be modified to detect and to report interference from the unlicensed operations; such detection would establish the maximum "noise temperature" that would be tolerated. The exact reporting and administrative/enforcement provisions were not clear. Established licensees rejected this concept in droves, and it died a quick and merciful death. 11. TV White Spaces (late 2000s). But then it returned! Now the provision is that semi-regulated unlicensed operation would occur on locally-unused TV channels. Again some sort of "noise temperature" function would be defined and some sort of administrator would keep tabs of the ever-changing kaleidoscope of activity, keeping the unlicensed devices just below the boiling point. Curiously this one may die because of the FCC's own parallel initiatives with respect to broadcast television: squeezing the broadcast assignments into ever less total spectrum, thus eliminating any white spaces, and, ultimately, driving over-the-air broadcast television into extinction. In the next piece we'll plod through the third and last section of the list of dismal FCC spectrum management engineering mistakes, before advancing some engineering reform suggestions in the final part. What do you think? "Let's save the universe for RF!" The Old RF Curmudgeon Since 1963, LBA has been providing RF equipment and engineering consulting services for radio and television broadcast and wireless communications. RF safety and RF interference resolution are specialties. Contact Mike Britner at mike.britner@lbagroup.com to put LBA expertise to work for you!    |
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