Editorial Technical report to help system designers and frequency coordinators
Have you heard that there are two new technologies moving into the 800MHz public safety radio frequency bands? One is frequency-division multiple access (FDMA), and the other is time-division multiple access (TDMA). A way of looking at it is that one uses several narrowband digital channels, and the other uses one wideband digital channel, in a given bandwidth.
The Associated Public-Safety Communications Officials (APCO), which serves as a trade association and a frequency coordinating company for public safety agencies, has been working in conjunction with the Telecommunications Industry Association (TIA) to develop a public safety digital radio standard. As it became apparent that more than one type of digital radio system would be occupying public safety frequencies, TIA began to develop methods to assist in the frequency assignment, design and operation of both types of system so that each one could avoid interfering with the reception of the other.
Spectrum refarming Then, along came spectrum refarming for the private land mobile radio frequencies below 512MHz, affecting both public safety and non-public safety systems. Spectrum refarming means revised regulations that modify existing technical standards and operating conditions. The idea is to make it possible for increasing numbers of transmitters to be used without creating too much interference. The result is going to be a mixture of modulation technologies and bandwidths on frequencies that used to be occupied on 25kHz or 30kHz channel centers by frequency-modulated (FM) radio. What once was fairly simple now becomes quite complex.
The Industrial Telecommunications Association, among other trade associations and frequency coordinating companies, realized that new guidelines would be required to assign frequencies among various narrowband and wideband digital and analog facilities. When ITA started talking with TIA about such guidelines, TIA’s years of experience in working on the public safety digital radio standard were applied and expanded in helping to create a blueprint for coordinating frequencies in the spectrum refarming environment.
Joint TIA-IEEE project Working together with the Institute of Electrical and Electronics Engineers’ (IEEE) Vehicular Technology Society (VTS) propagation committee, among other participants, the TIA’s working group on technology compatibility (designated WG 8.8) set about to create a document that frequency coordinators, system designers and manufacturers could use to place new radio communications systems within the radio spectrum and within geographic areas for the best results. Actually, the document will serve as a basis for writing computer software to automate the processing of license applications using system specifications and terrain data in ways that pre-computer methods could not.
Are you ready for the name of the document? “A Report on Technology-independent Methodology for the Modeling, Simulation and Empirical Verification of Wireless Communications System Performance in Noise- and Interference-limited Systems Operating on Frequencies Between 30 and 1,500 MHz.” Whew. “For decades, the wireless industry has been in need of an objective, accurate means of assuring wireless systems are properly designed, tested and validated,” said Gregory M. Stone, Ph.D. E.E., a co-chairman of WG 8.8 and chairman of the IEEE VTS propagation committee. “In addition, there has been a critical need for a fair and objective empirical method of resolving interference disputes. The efforts of the TIA and IEEE have appeared to pay off with the newly released report.”
Reactions ITA seems to be pleased with the document. “It will lead to better use of the spectrum compared to previous engineering methods,” said Sharpe Smith, ITA manager of communications and public affairs. “We support the development of these guidelines. We not only support, but we have proactively attempted to bring the process into the refarming realm. We’re not just giving it lip service, we’re showing up at the meetings, and we’re providing input. We think it important to the success of the post-refarming environment to have these guidelines.”
APCO’s executive director Ronnie Rand said that although it appears that some of the document may be complex for frequency advisers, “It appears to be a useful document. We view it as something that can be helpful in the coordination process. It is obvious that the people who worked on it took their task very seriously.” Rand also said that the suggestion that perhaps the FCC should publish the document and ask for public comment has been discussed.
Stone said that the joint TIA-IEEE effort enjoyed widespread land mobile industry and user community support. In addition to contributions made by APCO and ITA, he cited Ericsson, Motorola and the U.S. Immigration and Naturalization Service (INS). An acknowledgment published in the report says that the genesis of the document is the brainchild of Carl B. “Bernie” Olson, director of resource development engineering for Motorola’s National Engineering Services. It credits the following with substantive contributions: Harry Anderson, Ph.D., EDX Engineering; Dominic Acuri, Ericsson; John Oblak, E.F. Johnson; Brad Hiben, Tom Rubinstein, Casey Hill and Al Wieczorek, Motorola; and Judith F. Furie, INS. The INS provided additional staff and resources to produce the document.
Results Congress and the FCC pass their laws and regulations. Manufacturers create their equipment specifications. Operators for proposed communications systems design their facilities. Frequency coordination companies recommend or select radio channel assignments. Along the way, engineers and technicians have the responsibility to make communications systems function within the framework created by regulation, frequency coordination and available equipment.
We hope the TIA document will result in software development, frequency coordination procedures and regulatory policies that will help spectrum refarming to provide the improved services and expansion of the number of users that are expected. Our congratulations to the participants who drafted the document. –Don Bishop
