A STATISTICAL ANALYSIS OF THE FCC DATABASE FOR THE PCS BAND OF 1850-1990 MHz

INTRODUCTION

This paper presents statistics about the Private Operation-Fixed Microwave Service (POFMS) microwaves in the licensed Personal Communications System (PCS) band of 1850-1990 MHz. These statistics were derived using the Federal Communications Commission (FCC) database, which was posted on the Internet for the first time in July 1994 and revised in February 1995.

The characteristics of the FCC database for the 1850-1990 MHz band are important for PCS-POFMS coordination/relocation. The statistics presented in this paper help spotlight where the focus of coordination efforts will be and provide a feel for the "typical" microwave radio. PCS licensees are required to protect incumbent microwaves in this band from interference. To do so, they must follow the protection criteria outlined in the Telecommunication Industry Association (TIA) Telecommunications Systems Bulletin (TSB) 10-F. Specifically, Annex A of TIA Bulletin 10-F addresses interference into analog frequency division multiplexing/frequency modulation (FDM-FM) microwave receivers. As shown in the next section of this paper, 80 percent of microwave radios in the 1850-1990 MHz band are analog.

The FCC database can be obtained by contacting the FCC or via the Internet by anonymous ftp at fcc.gov in the directories x940701 and x950207 under /pub/Bureaus/Engineering_Technology/Databases/EMELF.

The next section of this paper briefly reviews general statistics on microwaves in the FCC database whose frequencies are co- and adjacent channel to the PCS band. This is followed by a detailed look at the statistics for analog microwave radio, and a brief discussion of those for digital microwave radio.

GENERAL STATISTICS

The statistics presented in this section characterize the microwaves found in the FCC database that have frequencies co-channel and adjacent channel to the PCS band of 1850-1990 MHz.

The FCC database contains data for three types of microwave radios: analog, digital, and hybrid (Note: The FCC database contains records for microwave emitters (or radios). These radios are typically paired according to a standard channeling plan to form a bidirectional microwave link). The chart below shows the proportion of each represented in the FCC database. Analog radio is clearly dominant at 80 percent, with the digital and hybrid types representing 12 and 8 percent, respectively.

Annex A to TIA Bulletin 10-F, mentioned above, contains methods for computing the interference objectives of analog microwave radios. Since 80 percent of the microwave radios in the 1850-1990 frequency range are analog, it is critical that these methods be implemented correctly. Otherwise, the PCS-POFMS interference analysis will be severely distorted.

Microwave Radio Modulation Statistics

Microwave Modulation	Count	Percentage
Analog	7173	80
Digital	1057	12
Hybrid	724	8

ANALOG MICROWAVE RADIO

The statistics in this section characterize analog microwave radios in terms of four factors: baseload, bandwidth, bandwidth as a function of baseload, and emphasis filtering.

Analog Baseload (Number of Channels)

The analog baseload is needed to compute the C/I objective curves following the technique described in Annex A to TIA Bulletin 10-F (see also the section on "Analog Microwave Emphasis Filtering"). As shown in the histogram below, the single most dominant baseload range is 133-300 channels, which characterizes 37 percent of the analog radios. The histogram also shows that only 10 percent of the analog radios operate with 301-600 channels.

Analog Baseload Statistics

Baseload (Number of Channels)	Count	Percentage
1-24	641	10
25-48	627	10
49-72	600	9
73-96	373	6
97-120	988	15
121-132	172	3
133-300	2427	37
301-480	346	5
481-600	344	5

Analog Bandwidth

The histogram below classifies analog radios in terms of their bandwidth. It shows that 66 percent of these radios have a 10 MHz bandwidth, 27 percent have an 8 MHz bandwidth, and only 6 percent have a 5 MHz or less bandwidth. The large number of analog radios with 8 and 10 MHz bandwidth indicates that these radios may be underutilized.

Analog Bandwidth Statistics

Bandwidth(MHz)	Count	Percentage
1	3	<1
2	20	<1
3	79	1
4	0	0
5	364	5
6	2	<1
7	12	<1
8	1956	27
9	8	<1
10	4716	66

Analog Bandwidth as a Function of Baseload

The chart below shows the relative frequency of bandwidth as a function of baseload (number of channels) for analog radios. As can be expected for the 1.9 GHz POFMS, every baseload range has most of the radios proportioned among the 5, 8, and 10 MHz bandwidths. Of the analog microwave radios in the 133-300 channel range, 80 percent have a 10 MHz bandwidth; most of the 300-channel analog radios are licensed in the 10 MHz channel bandwidth.

Analog Bandwidth/Baseload Statistics

Baseload (Number of Channels)	Bandwidth (MHz)
Baseload (Number of Channels)	1	2	3	4	5	6	7	8	9	10
1-24	2	9	37	0	72	2	2	361	2	151
25-48	0	1	8	0	79	0	0	302	1	236
49-72	0	6	6	0	20	0	0	243	0	325
73-96	0	2	0	0	20	0	9	166	5	171
97-120	0	1	11	0	85	0	0	237	0	654
121-132	0	0	0	0	9	0	0	41	0	122
133-300	1	0	0	0	9	0	1	470	0	1946
301-480	0	0	0	0	0	0	0	13	0	333
481-600	0	0	0	0	0	0	0	3	0	341

Analog Microwave Emphasis Filtering

Emphasis filtering is used in the analog FDM-FM radio to make efficient use of the allocated frequency band. The chart below shows the proportion of emphasized and unemphasized analog microwave radios. As shown in the chart, the radios are almost equally apportioned. One of the controlling factors used to determine the allowable level of interference into an analog receiver(the C/I objective) is a function of emphasis filtering (see Annex A to TIA Bulletin 10-F).

DIGITAL MICROWAVE RADIO

The histogram below classifies digital microwave radios in terms of their bandwidth. It shows a fairly proportional distribution of paths among the 3, 5, and 10 MHz bandwidths. Only 2 percent of the digital radios have an FCC-licensed bandwidth of 8 MHz.

Digital Bandwidth Statistics

Bandwidth(MHz)	Count	Percentage
3	364	35
5	287	27
8	22	2
10	384	36

SUMMARY

This paper presented statistics about the POFMS microwaves in the licensed PCS band of 1850-1990 MHz. These statistics were derived using the FCC database, which can easily be obtained via the FCC or the Internet. The statistics showed that 80 percent of the microwave radios in this PCS band are analog; thus it is critical that the methods for computing the interference objectives of analog radios contained in Annex A to TIA Bulletin 10-F be implemented correctly.

The analog microwave radio statistics showed that the single most dominant baseload range is 133-300 channels, which characterizes 37 percent of the analog radios. In terms of bandwidth, a large number of analog radios have 8 and 10 MHz bandwidth, indicating that these radios may be underutilized.

Finally, the digital microwave radio statistics showed that the digital radios are fairly equally distributed among the 3, 5, and 10 MHz bandwidths.