Spectrum Management is the art and science of managing the use of the radio spectrum in order to minimize interference and ensure radio spectrum is used to its most efficient extent and benefit for the public. For USDOT this is focused on supporting safe, efficient and economical transportation.
Radio spectrum is a limited resource that is rapidly approaching its limits. Demand for commercial spectrum to support broadband wireless communications has led the government to consider repurposing various radio frequencies, including the satellite communications bands next to GPS.
In the United States, the Federal Communications Commission [FCC] regulates the emission of non-Federal, private radio signals, dictating what is allowed and what it not. Most electronic devices are required by law to be tested for compliance with FCC regulations. And even with FCC compliance, electronic devices can still interfere with one another’s radio signals. While minimal radio signal interference may seem like a small annoyance, clear, unobstructed transmission of radio frequencies is crucial to the optimal functioning of critical and life-saving services such as fire, rescue, law enforcement and emergency medical services [EMS].
Many Federal agencies use radio frequency spectrum to perform vital operations. The National Telecommunications and Information Administration [NTIA] manages the Federal government's use of spectrum, ensuring that America's domestic and international spectrum needs are met while making efficient use of this limited resource. NTIA carries out this responsibility with assistance and advice from the Interdepartment Radio Advisory Committee and by... More
In 2012, the National Executive Committee for Space-Based Positioning, Navigation, and Timing decided to draft new GPS spectrum interference standards to help govern future allocation of commercial use of spectrum bands adjacent to the GPS signals. Learn More.
The goal of the U.S. Department of Transportation [DOT] Global Positioning System [GPS] Adjacent Band Compatibility Assessment is to evaluate the adjacent radiofrequency band power levels that can be tolerated by GPS and Global Navigation Satellite System [GNSS] receivers and to advance the Department’s understanding of the extent to which such power levels impact devices used for transportation safety purposes, among numerous other civil GPS/GNSS applications.
The Department of Transportation's [DOT] approach to this task is to develop power limit criteria for transmitters in the bands near GPS. DOT prepared a GPS Adjacent-Band Compatibility Assessment Plan providing a framework for the development of the criteria.
The GPS Adjacent Band Study has been the product of an extensive and transparent process to gather stakeholder views and input. DOT held a number of public workshops to discuss development of the test plan and review the draft test plan document. After the Test Plan was finalized, GPS/GNSS receiver testing was conducted at the U.S. Army Research Laboratory’s Electromagnetic Vulnerability Assessment Facility [EMVAF] at White Sands Missile Range [WSMR] in New Mexico in the spring of 2016.
Results included Interference Tolerance Masks [ITMs] based on 1 dB of C/N0 of degradation to the receiver from interference adjacent to GNSS signals.
For those that gave a clear response, time was the most often cited indicator [more than double the next cited indicator] to describe allocation type devoted to domestic and international programs; time was followed by resource allocation, department activities, and budget, respectively. The average frequency of allocation [regardless of indicator type] between domestic and international programs was 62% domestic and 38% international. However, there were a handful of respondents that made comments around the fact that they operated as a global company and didn’t make distinctions between domestic and international programs. The business activities most often performed outside of the “home country” [home country is used to denote the country in which the parent corporation resides] were:
•Services—owned or managed by the organization [70%]
•Sales and marketing [66%]
•Partners, affiliates, or wholly owned subsidiaries [57%]
•Supply chain—owned or managed by the organization [47%]
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Issues in Randomization
Pamela A. Shaw, ... Craig B. Borkowf, in Principles and Practice of Clinical Research [Fourth Edition], 2018
Monitoring
Proper implementation of established procedures for treatment allocation should be actively monitored. Monitoring of the randomization should be done by individuals not involved in the conduct of the study, such as by the data safety monitoring board [see Chapter 10] and/or an independent statistician, so that staff enrolling, following, or evaluating participants in the trial remain blinded. Frequency of allocation to treatment arm, by any stratification factors and for the study as a whole, should be routinely monitored. Evidence of differences in key baseline characteristics in allocated groups, or of frequent withdrawals once treatment is assigned, should trigger review of randomization and data collection procedures to ensure that baseline data are completely collected and all eligibility criteria are definitively determined before an assignment is made. Any software developed to generate random treatment assignments according to a desired scheme should be used to perform a randomization test prior to enrolling the first participant in a trial. Problems in implementation of the randomization procedures at best result in a suboptimal treatment allocation and at worst may invalidate the results of a trial.26 Precautions to monitor the study's randomization closely during the trial can allow for early corrections to minimize the impact of any problems should they arise.
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Headend Operation
Walter Ciciora, ... Michael Adams, in Modern Cable Television Technology [Second Edition], 2004
9.6 Summary
This chapter has dealt with a number of somewhat disconnected topics generally related to headend operation. Three general topics were covered: the standard band plan for cable television in the United States, management of outgoing optical and electrical signals in the headend, and monitoring of the quality of signals leaving the headend.
The television receiver and cable television industries have agreed on a band plan that defines the frequency versus channel number for television channels. The plan has been defined for three sets of frequency allocations: the standard plan, used in most instances today, and the HRC and IRC plans, chosen to reduce the visibility of distortion products. In the VHF band, the standard plan is identical to the off-air FCC channel assignments. In the old midband and superband regions, the plan follows traditional assignments with numerical channel designations. In the UHF band, the cable assignments are 2 MHz below the FCC plan because the FCC plan does not move from channel 13 [210–216 MHz] to channel 14 [470–476 MHz] in 6-MHz increments.
Signals in the headend must be managed in such a way that it is possible to carry different signals in different nodes but on the same frequency. This means that isolation must be maintained between unique signals bound to or from different nodes. On the other hand, certain signals are common to all nodes, and these have to be handled in common.
It is important to handle headend signals so that quality is maintained. Because the quality of signals exiting headends must be monitored, we have presented some fundamental ways to do so. Books have been written to cover the topic in detail.
We now move out of the headend and into the distribution plant. The next several chapters deal with the technology of distributing signals outside the headend.