Frequency Planning Concepts CHAPTER 4 EXTERNAL INTERFERENCE 4.1 INTRODUCTION Microwave telecommunications radio relay systems all over the world have frequencies greater than 1 GHz. Many factors must be con­ sidered in the proper choice and utilization of the various frequency bands. Each band has advantages as well as limitations. An appropriate segregation of various bands for various users is useful for optimum frequency utilization. It is assumed that various bands will be set aside for similar telecommunications users. This is necessary to allow simplifying assumptions to be made regarding transmit powers, interfering spectrums, and receiver susceptibility. It is difficult to coordinate the use of low- and high-power terrestrial mi­ Excerpt from: Kizer, G. M., Microwave Communication, crowave equipment in the same band and geographic region. Ames: Iowa State University Press, 1990. Once the telecommunications bands have been decided upon, a choice must be made as to the use of that band for digital or analog traffic and whether that traffic will be low- (less than 600 channels) or high-density transmission. In general, low- and high-capacity systems should not be allowed into the same band. One system will soon use up frequencies that are needed by the other. As a matter of principle, it must be assumed that any given band will eventually become fully ex­ panded. Band splitting and avoiding certain frequencies are undesira­ ble. If two systems operate in the same band and same geographical area, interference is minimized by having them on the same plan. Tables 4-1 through 4-6 list typical microwave terrestrial and satellite transmission bands. A microwave network that is very dense, with many branching points and crossings, can take advantage of a low- to medium-density frequency plan. A microwave route with few branching points is gen­ erally most economical using a high-density plan. The guiding principle of channel assignment planning is to use as few frequencies within a band as is necessary. Those frequencies are then repeated as often as possible to retain the maximum growth potential. In this regard, designating two groups of frequencies within a band for use in a highllow pattern is called a 2-frequency plan. This is because only two sets of frequencies are used anywhere on the route. Ifanother two sets of frequencies are used (eg, main and interleaved together), the fre­ quency grouping is called a 4-frequency plan. -113 Table 4-1. lTV terrestrial band allocations (l to 25 GHz). Table 4-2. CCIR terrestrial band allocations (cont,). Center Frequency Center Frequency Band (GHz) Region 1 Region 2 Region 3 Band (GHz) Use CCIR (GHz) (GHz) (Europe, Africa, (North America, (Far East, Rec. USSR, Thrkey, South America) Australia) Analog Digital Analog Mongolia) Telephony Television 1.375 1.350 - 1.400 • 3.800 3.400 - 4.200 • 635 1.481 1.427 - 1. 535 • • • 3.950 3.700 - 4.200 • • 382-4 1.67525 1.6605 - 1.690 • • • 4.0035 • 3.8035 - 4.2035 • • • 382-4 1.695 1.690 - 1.700 • 6.175 5.925 6.425 • • - 383-3 2.196 1. 700 - 2.690 • • • 6.770 6.430 7.110 • • 384-4 3.350 3.300 - 3.400 - • 7.275 · 7.125 - 7.425 • 385-3 3.800 3.400 - 4.200 • • • 7.400 7.250 - 7.550 • 385-3 4.700 4.400 • 5.000 • • • 7.575 7.425 - 7.725 • 385-3 7.175 5.850 - 8.500 • • • 7.700 · 7.550 - 7.850 • - 385-3 10.225 10.000 -10.450 • - • 8.000 7.725 - 8.275 • 386-3 10.590 10.500 - 10.680 •• • 8.350 8.200 8.500 • 11.600 10.700 - 12.500 • • • 11.200 386-3 10.700 - 11.700 • • 387-4 12.625 12.500 - 12.750 • • 13.000 • 12.750 - 13.250 • • • 497-2 13.000 12.750 - 13.250 • • • 14.875 14.400 - 15.350 - • 14.350 14.300 - 14.400 • • 14.925 · 636 - 14.500 - 15.350 • 636 14.600 14.400 - 14.800 •• • 18.700 - 17.700 - 19.700 • · 595 18.700 17.700 -19.700 • • • 22.400 21.200 - 23.600 • • 22.400 21.200 - 23.600 • •• • 637 SOURCE; CCIR Recommendations (Green Books), Volume IX-I, 1982. SOURCE: ITU Radio Regulations, 1982, Volume I, Part A, Chapter III, Article 8, Sections I and IV. Table 4-2. CCIR terrestrial band allocatioll8 . Table 4-3. USA terrestrial band allocations (l to 25 GHz). Center Frequency Center Frequency Band (GHz) Use CCIR Band (GHz) Use (GHz) Notes (GHz) Rec. Analog Digital Analog Govt. Common Private Television Telephony Television Carrier Fixed Relay 1.740 1.800 1. 700 • 1.900 • 283-4 1. 710 - 1.770 • 1 • 1.920 1.903 1. 703 • 2.103 • 382-4 1.850 - 1.990 - . • 6 • 2.145 1.932 1.732 - 2.132 • • 382-4 2.110· 2.180 · • 2.165 2 2.0865 1.8865· 2.2865 • • 382-4 2.130 - 2.200 - - • 6 2.245 · 2.000 1.900 • 2.100 283-4 1.990 - 2.500 3 • • 2.245 • 2.101 1.901 - 2.301 • • 382-4 2.200 - 2.290 • 1 2.475 2.200 2.100 - 2.300 • • 283-4 2.450 - 2.500 - • 6 2.600 2.500 - 2.700 • 283-4 2.595 2.500 - 2.690 · • 3.950 • 6 3.700 - 4.200 - • - 2 See source at end of table. See source and notes at end of table. 114 -115 .. Table 4-4. ITU satellite band allocations (1 to 25 GHz). Table 4-3. USA terrestrial band allocations (1 to 25 GHz) (cont). Center Frequency Band (GHz) Use (GHz) Up-link Down-link Center Frequency Band (GHz) Use Notes (GHz) 1.428 1. 427 - 1. 429 Govt. Common Private Television • 1.530 1.526 - 1.636 Carrier Fixed Relay • 2.596 2.500 - 2.690 • • 3.800 3.400 - 4.200 • 4.696 4.400 - 4.990 • - - 1 4.650 4.500 - 4.800 • 6.176 5.925 - 6.426 • 2 6.400 5.725 - 7.075 • 6.700 6.626 - 6.875 · • - 619 7.500 7.250 - 7.750 • 7.000 6.875 - 7.126 · • 3 8.150 7.900 - 8.400 • 7.1876 7.126· 7.250 • - - 1 11. 725 10.700 • 12.750 • • 7.6376 7.300 - 7.976 • · - - 1 13.000 12.750 - 13.250 • 8.100 8.026 - 8.175 • - · - 1 14.400 14.000 - 14.800 • 10.616 10.550 - 10.680 - • • 2/6 17.500 17.300 - 17.700 • 11.200 10.700 - 11.700 · • · - 2 17.900 17.700 - 18.100 • • 12.460 12.200 - 12.700 - - • - 7 19.650 18.100 - 21.200 • 12.926 12.700 • 13.150 · • - 9 22.750 22.500 - 23.000 • • 12.950 12.700 - 13.200 - · · • 4 3 12.976 12.700 • 13.250 · · - • SOURCE: ITU Radio Regulations, 1982, Volume I, Part A, Chapter III, Article 8, 6 13.226 13.200 - 13.250 · - • - Section IV; and Part B, Chapter VIII, Article 27, Nos. 2509, 2610, 2 13.226 13.200 • 13.250 - • · and 2611 1 14.826 14.500 - 16.350 • - · - COORDINATION: In accordance with ITU Radio Regulations, Part A, Chapter 2131416 18.700 17.700·19.700 - • • • IV, Article 11 (RR11), Sections III, IV, and V; Article 12 2 21.600 21.200 • 22.000 - • · (RRI2), Subsection lIE and Part B, Chapter VIII; Article 27 1 22.400 21.200·23.600 • - - (&R27); Article 28 (R&28), and Appendix 28 (AP28); Resolution 8 22.500 21.800 - 23.200 · - • - 703 (RES703); and Recommendation 708 (REC708). 22.700 21.800 - 23.600 · • 6 22.800 22.000 - 23.600 - • • 2/5 Table 4-5. CCIR satellite band allocations. SOURCE: Code of Federal Regulations, Title 47 (Telecommunication), Chapter I Center Frequency Band (GHz) Use (GHz) (Federal Communications Commission), Parts 88 noted below (88 Up-link Down-link ammended through October 1986). 2.695 2.500 - 2.690 • • NOTE 1: Part 2.106 NOTE 4: Part 78.18 NOTE 7: Part 94.90 3.650 3.400 - 3.900 - • NOTE 2: Part 21.701 NOTE 6: Part 94.61 NOTE 8: Part 94.91 3.950 3.700 - 4.200 - • NOTE 3: Part 74.602 NOTE 6: Part 94.66 NOTE 9: Part 94.93 5.976 6.726· 6.225 • 6.175 6.925· 6.426 • 7.276 7.250 - 7.300 • • 8.000 7.975 - 8.026 • • 11.076 10.950 - 11.200 • 11.550 11.300 - 11.800 - • 11.676 11.450 - 11. 700 · • 11.976 11.700 - 12.250 · • 14.250 14.000 - 14.500 • 17.400 17.300 - 17.800 • SOURCE: CCIR Recommendations (Green Books), Volume IV/IX-2, 1986 COORDINATION: In accordance with CCIR Green Books, Volume IV/IX-2, Recommendations 355-3, 366-4, 357-3, 358-3, 406-5, and 558-2. 116 - 117 ,. CHAPTER ,. -118 EXTERNAL INTERFERENCE 119 Table 4-6. USA satellite band allocations (1 to 25 GHz). would appear that higher frequencies have a disadvantage. However, for a given size of antenna, gain increases with frequency. When an­ Center Frequency Band (GHz) tenna gain at both ends of the path is considered, total path loss actu­ (GHz) ally decreases as frequency is increased. This tends to be compensated for by additional transmission line loss, lower transmit power, and in­ creased receiver noise figure available at high frequencies. In general, 2.6176 2.600 - 2.635 path loss is not a factor in choice of band. Frequency of operation is 2.6725 2.665 - 2.690 3.950 3.700 - 4.200 significant in climates where intense rainfall is prevalent.