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A.~.3 Wireless Communication Wireless communication has significant ITS applications: 1. Any vehicle-to-infrastructure communication (i.e., mobile applications) 2. Temporary communication faciiides including rapid deployment when required 3. Cations where wire or fiber are not options: a. canyon, ever, other geographic obstacles b. Business or traffic disruptions for installation are unacceptable 4. Situations where more cost effective Han wire or fiber 5. Diversity~ot-standby for reliability Wireless offers bandwidths and bit rate capabilities comparable to wire and, to a lesser extent, to fiber. Vanous wireless options are available to support virtually any llS link, including low- speed local links, high-speed backbones, and TOC-to-TOC links. Wireless communication has unique characteristics compared win wire and fiber: 1. Wireless communication requires installation of only terminal equipment. In addition, up to Me repeaterless propagation limits of We installation, has fixed (constant) cost per link regardless of distance, compared USA fiber/wire which must include approximate linear cost/un~t of distance. This comparison is depicted in Figure A.13-~. Ri~t-of-way~site acquisition costs are only incurred at terminal locations, not between as with fiber/wire. 2. Wireless requires FCC licensing for guaranteed interference-free operation or careful design/operation considerations in Be unlicensed bands. L:W~h~c2~t N~3-51e P~2F~Re~n A1-124
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r 3. Wireless propagation and coverage characteristics vary widely based on frequency, antenna heights, intervening terrain, weaker, allowable power, etc., which makes design of wireless systems more complex than wire or fiber design. Wireless, like fiber and wire, has link budget criteria for successful operations. Table A.~.3 lists typical wireless little parameters. Because wireless has different propagation modes and widely varying weaker, atmospheric, terrain, etc., lim~tabons, repeaterIess distances and achievable bit rates are highly vanable. Table A.~.3 Typical Wireless Link Budge! Parameters I Parameter T Example Transmit Power | 50,000 WaNsAM Broadcast Stat on (77 dbm) Transmission Loss* -6 dB/Octave Free Space (Octave is double the distance) -6too18dB/Octave inMultipath Receiver Sensitivity -80 to -120 dam *Actual Transmission Loss is highly variable depending on many factors as discussed In text. A.~.3.! Wireless Propagation and Coverage At Me most fi~nd~mental level, wireless propagation and coverage can be modeled by He free space transmission (i.e. Line of Sight propagation) formula (Equation A.~.3.~-~) (adapted from lakes, Microwave Mobile Communications). LW~h~2.~t NC~3-51e P0e2F~Re~n A1-126
Equation A.1.3.1-1 Pr = Pt (4 d) g&, or Pr ~ ,1 2 L = - = if_ gtgr where: L = pad loss P. = Receive Power P'= Transmit Power A = wavelength = c - 10 "meters /see d = distance between g2. = gain of transmit antenna gr = gain of recede antenna c = speed of light, f = frequency transmit Id receive antennas For an antenna that receives or transmits equally In all directions over a sphere, grge = I. This is generally referred to as an isotropic antenna Needless to say, directional antennae are frequently employed to Improve wireless system performance. Equation A.~.3.~-1 is often converted to Lab (]OSS expressed in decibel or dB) with antenna gates, gigs = I, and the loss equivalently expressed as: c Equation A.1.3.1-2 LdB = - 92.4 - 20 x log ~.O(fGNz) ~ 20 X log ~o~dk,,') In free space line-of-sight propagation, Here is a loss of 6 dB for each doubling of distance and 6 dB per doubling of frequency. Thus, propagation distance, or coverage, is less at higher frequencies (assuming all other factors are equal). Free space (or spaces) propagation is usually only consistently achieved in outer space, although many earthbound applications under favorable conditions, closely approximate free space propagation. Generally, actual propagation losses are more severe Man free space and must be modeled (usually stadshcally) accordingly. Free space propagation is typically "line-of-sight," t.:\.NCHRP`.Phase2.rp~ NCHRP 3-51 · Phase 2 Ftnal Report A1-127
but may include refraction (i.e., sometimes creating multiparty), and some diffraction over terrain or obstacles (e.g., buildings). Free space propagation occurs at all RF frequencies and is dominant at hider frequencies. Another mode of propagation is ground (or surface) wave propagation which is the dominant component at frequencies less than 2 megahertz. This is a secondary component up to He very high frequency range (30-300 MHz) and can usually be neglected at frequencies above 300 MHz. Ground waves usually combine with direct (free space) signals and other reflected signals in a manner such Hat He received signal has greater attenuation Han a free space signal; however, at very low-frequencies, ground waves dominate and therefore are used by the rnilit.ary for worldwide commun~cabon with submarines and for other cndcal missions. Propagation is very good at these low frequencies and literacy provides worldwide communication. The AM broadcast band propagates via ground waves (as wed as other modes). Skywaves, another mode of propagation, is the bending of a wave as it passes from one medium to another because of different propagation speeds in He two mediums. This bending causes radiowaves Hat would normally propagate into space to bend back toward He earn. This bending typically occurs in the ionosphere region which is approximately 30 to 260 miles above the earths surface. Depending on He frequency employed, time-of-day (night is best), plus other factors; skywave propagation can support communication link distances from 60 to over 6000 miles. Skywave propagation is the dominant mode of propagation in the 2 to 30 MHz frequency range. Figure A.~.3.~-1 illustrates these modes of propagation. Propagation characteristics are highly dependent on frequency and can be classified into frequency bands with each band having essentially similar propagation charactenstics. Table A.~.3.~-! lists the generally accepted frequency band cIassificabons, range of frequencies, propagation characteristics, and typical uses. ~;\NC~Phasc~rp ~NCHRP 3-51 · Phase 2 final }report A1-128
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In RF (wireless) system design, coverage is estimated based on propagation loss between transmitting and receiving antennae. For frequency reuse based on geographic separation, signal attenuation of a potential interfering transmitter due to propagation loss at a receiving antenna must be sufficient so that the interfering signal level is significantly less Can the desired signal. Obviously, at lower frequencies that support over-the-honzon propagation modes such as groundwave and skywave, frequency reuse distances will be great. Conversely, LOS propagation to the horizon, which is the dominant propagation mode above 30 MHz, permits much shorter frequency reuse distances and smaller direct coverage areas, but greater system capacity through frequency reuse. In addition to slywave, ground/surfacewave, and free space LOS propagation modes, over factors influence propagation: 1) In free space propagation, multipath attenuation, (where reflected and direct signals combine) can be greater or less. A typical multiparty loss profile is depicted in Figure A.~.3.~-2. Up to a distance prior to onset of multiparty, the loss profile is He typical 6 dB/km and Hereafter has a steeper loss profile greater Han 6 dB/km. Under more severe multipath conditions, multiple breakpoints may exist with successively steeper loss per unit Of distance. Multiparty is a dominant factor in mobile wireless communication (e.g., cellular, unlicensed spread spectrum). 2) Above VHF, traditional suggests theory is that propagation is limited to He LOS honzon. Experience, often He result of unexpected interference, has proven overwise. Current theory suggests that weaker produces venous select conditions Hat actually enhance propagation. These conditions include tropospheric scatter, rain scatter, dusting, radiation inversion, reflection from objects, etc. When these conditions anse, propagation can extend significantly beyond LOS. These conditions can occur virtually anywhere, but seem to be most prevalent over wann water areas such as Florida, He Gulf Coast, and California, In He U.S. These conditions also often create undesired interference; however, RF communication propagation engineers usually understand local conditions and often have mesons to address these problems and/or use to their advantage. L:~h=~.~t NC^P3^51 · P~e2F~Re ~A1-131
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Wireless propagation modeling and design is not an exact science. Many variables exist so detailed RF propagation and coverage design should be accomplished by communication engineers who have access to many models. Rough planning estimates, however, can be calculated using the free space model of Equation 1, modified as appropriate, by Me actual antenna gain. A.~.3.2 FCC Rules RF spectrum for wireless communicators is a scarce resource ~at, except for some unlicensed bands, is allocated to service providers and/or users on exclusive or shared bases, though licensing administered by the Federal Communications Commission (FCC). The mles governing licensed and unlicensed wireless operations are contained in the Code of Federal Regulations (CFEt) Title 47, Telecommunications, consisting of parts 0 Trough 101 (currently). Table A.1.3.2-1 lists Me parts of CFR 47 relevant to ITS. Their titles provide an indication of the services addressed. Table A.1.3.2-2 provides more detail on some of the Parts significant to ITS and includes services, comments, pending FCC Notices of Proposed Rule Malting (NPRM) and Reports and Orders wig ITS impact, and ITS applications. A. l.3.2. ~ FCC Licensing and Coordination FCC licensing procedures and rules are generally described in Part ~ of CRF 47. These procedures and rules are complicated, partly because of many years of evolution and upgrade. This section is not intended to be an in-depth discussion of the details of licensing and coordination, but a general overview of Me concepts of Importance to ITS. FCC licenses/au~onzations may be required in the following situations: I) Operator/station license to operate a transmitter at a given site or within a specified geographic area L~\NCHRP\Phas~p' NCHRP 3-51 · Phase 2 Final Report A1-133
Table A.~.3.2-1 Code of Federal Regulation (CFR) 47 ~ Telecommunications Parts Relevant to ITS FCC Part (partial list of Communication Organization relevant parts) Part 1 Practice and Procedures Part 2 Frequency Allocations and radio treaty matters; general rules and regulations Part 5 Experimental radio service (other than broadcast) Part 13 Commercial radio operator Part 15 Radio Frequency devices Part 17 Construction, marking, and lighting of antenna structures Part 18 Industrial, scientific, and medical, devices (ISM) Part 21 Domestic public fixed radio services Part 22 Public mobile services Part 23 International fixed public radio communications see/ices . _ Part 25 Satellite communications Part 68 Connections of terminal equipment to the telephone network Part 73 Radio broadcast services Part 74 Experimental, auxiliary, and special broadcast and program distributional services Part 76 Cable television services . Part 79 Cable television relay service Part 80 Stations in the maritime services Part 87 Aviation services Part 90 Private land mobile radio services Part 94 Private operational-fixed microwave services Part 95 Personal Radio services Part 97 Amateur radio services .. Part 99 ~ Part 100 Direct broadcast satellite service . . . . Part 101 Terrestrial Microwave Fixed Radio Services (will replace Part 94 and Parts of Part 21) L:\NCHRP\Phase2~pt NCHRP 3-51 ~ Phase 2 Fmal Report A1-134
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2) Type of approval by Me FCC of wireless equipment certifies that the manufacturer has satisfactorily demonstrated to He FCC Cat Be equipment complies win appropriate FCC technical standards. 3) Certain operationslmaintenance personnel may require licenses for particular functions regarding the uncalibrabon, maintenance, etc., of Be equipment. Licensing requirements vary and exact requirements are typically defined in specific rules of Be service of operation (see Table A.~.3.2-2 for list of services). Within a CF~ Part, one or more of Be following may be defined for transmitters: Transmitter power, Types of emission and bandwidths allowed, Antenna heights, Antenna gain, Pu~poses/organizabons eligible for licenses, Frequencies of operation and frequency coordination requirements for application, Location or area of transmitter operation, Requirements for type cer~ficadon of equnpment employed, Ground rules for use (exclusive, shared, etc.), arid Licensing requirements for venous functions, i.e., equipment adjustment, maintenance, etc. . . . . . Licensing by Be FCC provides a memos for users to gain exclusive, interference-free use of RF spectrum at a geographic location or within an area; or, in some services, control sharM use with defined rules. Interference-free operation is achieved by geographic separation of transmitters on Be same frequency (co-channel) or, potentially interfering adjacent frequencies (adjacent- channel) sufficient to reasonably ensure attenuation below interfering levels. Required separation distances vary according to: · Transmitter power, · Antenna gain, defectivity, and height, · Frequency of signal, · Intervening terrain or obstacles, ~:\NC~RP\Phase~rp: NCHRP 3-51 · Phase 2 Final Report A1-137
· Receiver sensitivity, and · Modulation formats employed. The analysis of available frequencies to determine if interference-free operation of planned and existing users is achievable, is referred to as frequency coordination (or coordination). Frequency coordination is an engineering analysis, perhaps including field measurements, that involves: 1) Database of existing licenses, geographic location of transmitter, power levels, antenna type, frequencies, etc. Source data win this information is available from Me FCC; 2) Map data of the terrain, obstacles, etc., for the anneals) of operation; 3) Propagation models for frequency bands of intended operation including effects of terrain, obstacles, etc.; and 4) Selection of allowable, unused, frequencies that meet interference criteria. Frequency coordination usually requires a frequency coordination sentence company or consultant with appropriate computenzed database of FCC license data and geographic map data. Although Me exact requirements vary win service (or Part), Me FCC: typically requires applicants to submit frequency coordination data win Me applications. Certain frequency bands are licensed, but require no coordination. These bands provide Me availability of an FCC database of licenses, frequencies employed, exact or approximate location, equipment/operation parameters, etc., but provide no current or future guarantee of interference-free operation. An example is Me 31 GHz microwave band. A.~.3.2.2 Unlicensed Operation - Part 15 Unlicensed operation refers to operation of a transmitter, or any radiator, without Me requirement of obtaining an operator's license, although regulations generally do require type c:~NCHRP~Phase:~p ~NCHRP 3-51 · Phase 2 final Report A1-138
certification of equipment by the manufacturers. Most of Me rules pertaining to unlicensed operations are contained in Part 15, '`Radio Frequency Devices." Part 15 has 3 subparts: Subpart A: General - contains technical specifications, administrative requirements, etc., relating to marketing of Part 15 devices. Subpart B: Unintentional Radiators - contains regulations concerning incidental radiators such as TVs, radios, any receiver, etc., that define limits of unintentional radiation capable of causing interference. Certification of compliance andJor equipment marking is required for many devices. Subpart C: Intentional Radiators - contains Me rules for unlicensed operations of intentional transmitters (or radiators) for communication, perimeter protection systems, field disturbance systems, cable locating, tunnel radio, cordless phones, power line radios, garage door openers, alarms, etc. ITS practitioners should generally be aware that Subparts A and B contain rules and regulations that require compliance for all electronic equipment, and ensure that procurements address these requirements. Subpart C addresses many unlicensed communication options of importance to ITS including: I) Unlicensed operations in the AM and FM broadcast bands; 2) Unlicensed spread spectrum operation in what is generally referred to as the Industrial, Scientific, and Medical aSM) bands; and 3) Over operations in Me ISM bands such as Automatic Vehicle Identification Systems (AVIS), RF/toll tags, etc. :\NCHRP`Phasc2.rp ~NCHRP 3-51 · Phase 2 Fmal Report A1-139
Unlicensed Part 15 operation generally involves restrictions to low-power operation and thus limited distancefcoverage areas. The Part 15 power restrictions are expressed in two essentially equivalent ways: I) Transmitter power often with restrictions on allowable antenna gain (an electrical measurement at the antenna terminal of the radio), and 2) Field strength in volts/meter (an RF measurement of the signal strength of the propagating electromagnetic signal). Figure A.~.3.2.2-1 illustrates the concept of how an antenna converts an electrical signal to a radio wave ~ at an antenna. The radio wave propagates with an attenuating loss of signal (or field) strength, typically measured in microvolts/meter. The Part 15 regulation typically specifies that field strength measurements, when specified, be measured at a specified distance from Me transmitter antenna. Obviously, an increase or decrease in the transmit power will increase the field strength at any distance, but the field strength unroll also be determined by the antenna type, antenna gain, frequency, cabling/connector losses, etc., that are fixed once installed. Figure A.~.3.2.2-2 furler illustrates the concept for an isotropic antenna which converts the electrical signal into an electromagnetic signal Mat propagates equally in all directions. At any distance (r) from the antenna, the power density, P. is approximately the transmitter power, Pt. (minus any cabling/connector losses) divided by Me area of Me surface of an imaginary sphere (4= ray. Although an exact relationship between transmitter power (Pt), and power density (P) involves many factors, a frequently used approximation is shown in Figure A.~.3.2.2-2 wed the following definitions: 1) P transmitter powerin wafts 2) G antenna gain, where G = ~ for an isotropic antenna 3) r distance from Me antenna 4) V field strength in volts per meter (usually m~crovolts [pV] per meter) L;\NCHRP\Ph~rpt NCHRP3-51. Phase2FmalReport A1-140
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Equation ~ in Figure A.~.3.2.2-2 is generally referred to as the free space propagation model. The 120~c on He right hand side is the characteristic impedance of free space in ohms. Equation 2 in Figure A.~.3.2.2-2 provides a memos for converting transmitter power to/from field strength. Field strength measurements can be employed by the FCC to test for verification/compliance with the Part 15 regulations. Parts 15.31 and 15.33 define standards for measuring field strength: 1) American National Standards Institute PANSY C63.4-1994, entitled "Methods of Measurement of Radio-Noise Emissions from Low-Voltage Electrical and Electronic Equipment in the Range of a kHz to 40 GHz," published by the IEEE as SH 151180. 2) Publication 16 of He International Special Committee on Radio Interference (CISPR) of He Electrotechnical Commission. Both inband and out-of-band emission limits are specified. These techniques may also be used for field measurement of interference from ex~sdug users at a proposed or existing troublesome site. Part 15.209 defines general requirements for radiation emission limits for intentional radiators. These are extracted and summarized in Table A.13.2.2-~. The emission limits are very low and will only support communication over very short distances. It should also be noted Hat Part 15.205, "Restncted Bands of Operation," lists frequency bands where only spurious emissions are permitted (as opposed to fundamental or intended emissions) which include harmonics, residual out-of-band, etc. emissions. Parts 15.211 through 15.251 provide emission limits for specific bands that in some cases exceed general requirements and in over cases are less. We win be discussing specific bands of interest in ITS. Unlicensed Part 15 operation users should also be aware of He following: The antenna employed shad be supplied by He responsible parer (typically He manufacturer) and He equipment shall have unique connector/coupling to promote compliance. Certain exceptions exist which include leaky cables, tunnel radio, and some medium frequency ~) or lower band operations such as the AM broadcast band. ~;\NCH~Phasc:.rp: NCHRP 3-51 · Phase 2 Final Report A1-143
Table A.~.3.2.2-1 CFR 47, Part 15.209 General Requirements for Radiation Emission Limits for Intentional Radiators Frequency (MHz) | Field Strength | Measurement distance (microvolts/meter) (meters) 0.009 - 0.490 2400/F (kHz) 300 0.490- 1.705 24000/F (kHz) 30 1.705 - 30.0 30 30 30 - 88 100 3 _ 88 - 216 150 3 216 - 960 200 3 Above 960 500 3 (summarized, consult regulations for details) 2) Part 15.5, "General Conditions of Operation" states that: a) no vested right to continued operation exists; b) such equipment must cause no Hannibal interference to others licensed in a particular band; and, c) must cease operation (unti! corrected) if notified by Me commission of harness! interference to others. In essence, Part 15 users can cause no interference and have no protection from interference based on current or future use by others win higher priority licenses. 3) Part 2, Subpart J contains Me rules of equipment type certification and testing. Part 15 unlicensed operations in He AM (525-1705 kHz) and FM (~-108 MHz) are authonzed at low power: 1) Part 15.219 defines rules for Part 15, AM band operations and at no more Man 100 milliwatts of power and provided that He total length of transmission line, antenna, and ground (if used) not exceed 3 meters. L:\NCHR~Phasc2-rpt NCHRP3-51 e Phase2FinalRepoIt A1-144
2) Part 15.221 defines rules for Part 15, AM band operation using a leaky coaxial cable. This has been used for HAR applications. 3) Part 15.239 defines rules for FM band operation aBowing a field strength of 250 microvolts/meter at a distance of 3 meters from He antenna. Assuming an isotropic antenna (i.e., omnidirectional or Gain = D, this is approximately equal to IS x lob watts (or 47 dBm) of transmitter power and wiN provide short range coverage from 50 feet to optimistically, 300 to 400 feet depending on the site. In addidon to He unlicensed Part 15 operation, Highway Advisory Radio (MAR) (referred to as Traveler Information Systems [IIS] by He FCC) is Bronzed at higher power levels in Part 90 and win be discussed elsewhere. Part 15.251 covers provisions for operation of Automatic Vehicle Idendficabon Systems (AVIS). The frequency bands of operation are 2.9-3.26 GHz, 3.267-3.332 GHz, 3.339-3.458 GHz, and 3.358-3.6 GHz. These bands have been authorized for approximately 20 years, but do not appear to be used. Of significance to ITS are operations in what is generally referred to as He "industrial, Scientific, and Medical Band" PRISM). ISM rules, as defined In Part I8, cover He generation or use of RF energy for non-telecommunication applications suggested in He title. ~ 1985, He Part 15 rules were modified to permit telecommun~cabon applications in certain ISM bands using spread spectrum: Band Bandwidth 902-928 MHz* 26 MHz 2.435-2.465 G Hz* 100 MHz 5.785-5.815 G Hz* 150 MHz 24.075-24.175 GHz 250 MHz Spread spectrum operations at higher power authorized L:\NCHRP\Phase2.rpt NCHRP 3-51 · Phase 2 Final Report A1-145
The Part 15 rules regarding intentional radiation in these ISM bands are: I) Part 15.245 covering field disturbance sensors. 1 2) Part 15.247 covering spread spectrum and allowing 1 watt of transmit power which greatly increases range. 3) Part 15.249 covers non-spread-spectrum operation that has substantially lower power limits and much shorter coverage range. RF/toll tags operate under this part. The regulations allow field strengths of 50 millivolts per meter (mv/m) at 3 meters if for the 900 Adz, 2.4 GHz, and 5.7 GHz bands, and 250 my/m for the 24 GHz band. For comparison win He ~ watt (~30 dBm) spread spectrum authorization, 50 my/m approximately equivalent to .75 milliwatt transmit power or -~.2 dBm. Assuming all else is equal, this increase in power would increase range over 20 miles assuming hypothetical free space and to a lesser, but significant, distance why typical installations. We win address range capabilities in our discussion of spread spectrum. A.~.3.3 Microwave Pointdo-Point Wireless Microwave is a wireless technology that has He following charactenshcs: 1. Point-to-point operation (near line-of-sight) between fixed sites. 2. Frequency of operation from above approximately 1 GHz to above 50 GHz. 3. Typically uses highly directional (0.5-2.5° beam widen, high gain (3045 dB), antennas. 4. Supports bit rates from low speed to over 600 Mbps. 5. In bands below 10 GHz, with antennas on towers at heights of 50 to 100 meters, average paw lengths of about 40 km (25 miles) are achievable. At higher frequencies, attenuation due to rain and oxygen shortens paw lengths considerably. L:~h~c2~t NCHRP3-51a P0e2F~Re~n A1-146
6. 99.999% availability is easily achievable with proper system design. Worldwide Were has been a trend over We last 10-20 years in telecommunications toward establishing an integrated digital network Tat has included bow switching and transmission. Thus, digital microwave channel Dlans (i e cam or .~n~cinsS Anti h~n~lwirithN hoop horn the aa~^ ~ ~ ~ ~ ~ _ _,= __ c~ ~,~ ,,~, _ Add, id,_ ~.~- as analog to facilitate analog and digital coexistence on We same routes and have been conceived to efficiently support We TDMA structure of He digital hierarchy, and more recently, SONET. The standards organizations Hat establish worldwide network starboards include rrU-R (formerly CCIR) and 1TU-T (fonnerly CCIl]) internationally, and He FCC in He U.S. The key issues in these standards are: I) bit rates; 2) channelization; and 3) out-of-band emissions and interference. He U.S., He FCC regulations for microwave in CF~ 47 are in the following parts: I. Part 21-Domestic public fixed radio services (common camera); Subpart ~ point-to-point · .. . microwave raalo services. 2. Part 94 Private operational fixed microwave service. This defines the rules for private use (i.e., not for sale to the public). 3. Part 101 (Rule-making in progress) To consolidate He above two rule parts into a single consistent set of technical rules for bow private and commercial common carrier operations. 4. Part 15, Unlicensed operation (discussed in Section A.~.3.2.2~. The frequency spectrum allocated for microwave is above 932 MHz. Table A.~.3.3-1 is a summarized list of He applicable microwave bands. As a result of He FCC's PCS nobles, He 2 GHz band is no longer available for new microwave operations under Parts 21 and 94. Thus, L:~h~2.~: N=RP3-51e P~e2F~Re ~Al-147
Table A.~.3.3~1 Microwave Frequency Bands' Microwave Bands, MHz2 | Max Bandwidth Authorized | Supportable Bit Rate Capacities3 _ 928-929 12.5,25 kHz N/A 932-932.5 / 941 -941.5 12.5 kHz Very low 932.5-9351941.5-944 1 200 kHz 1 Verylow 952-960 200 kHz N/A 1850-1990 1 5 or 10 MHz 1 Secondary Status 2110-2130 / 2160-2180 3.5 MHz Secondary Status L 2130-2150 / 2180-2200 1 800 or 1600 kHz 1 Secondary Status 2150-2160 10 MHz 2450-2483.5 625 KHz ~ A 2483.5-2500 800 or 600 KHz N/A _ 3700-42004 20 MHz Medium 5925-6425 30 MHz Low/Medium/High 6425-6525 25 MHz N/A 6525-6875 10 MHz Low/lVledium . 10555-10680 5 MHz Low _ 10700-11700 40 MHz Low/Medium/Hi h 9 12200-12700 20 MHz Secondary Status 13200-13250 25 MHz NtA 17700-18140 / 19260-19700 220 MHz 18140-18142 2 I\AHz N1A 18142-18580 6 MHz Video 8580-18820/ 18920-19160 1 20 MHz 1 Low/Medium 18820-18920 10 Mbiz Point to Multipoint 19160-19260 10 MHz Point to Multipoint 21200-23600 1 up to 100 MHz ~Low/Medium/High 27500-29500 220 MHz Band under revision 31000-31300 25 or 50 MHz Lows . 38600-40000 up to 50 MHz Low/Medium/High6 Above 40000' TBD TBD (~) At 6 GHz and above, He proposed Part 101 bands are He same as He current Part 94 and Part 21 bands. (2) Future FCC licenses will predominately be in the 6 GHz (starting at 5.925 GHz) and above bands due to allocation of 2 GHz Bands to PCS and other applications. (3) Supportable Bit rates: Very low: below ~ Mbps; Low: below 45 Mbps; Medium: 45 - 135 Mbps; High: Above 135 Mbps. L:~2.~t NC~3-51e Ph~2F~Re~n A1-148
(4) Practical use of this band is dependent on the grown of satellite services at 4 GHz. (5) Licensed, but uncoordinated (i.e., no interference protection) band (6) Band subject to a wide area licensing policy where you basically "own" a 50 MHz paired block in a given geographical zone. This band has filled up rapidly in the last year and the creation of a new 37 GHz band is under discussion. (7) A 50 and a 55 GHz band have been proposed. wad He exception of the small 900 MHz bands, new microwave operations will be in the bands above 5.9 GHz where the old Parts 21 and 94 allocations are essentially He same as the proposed Part 101 avocations. This table includes: 1. The Tower and upper limits of the frequency band In MHz. 2. The maximum channel banded for each band. 3. Practical bit rate capabilities by frequency band. Table A.~.3.3-2 summarizes microwave channels by nominal bandw~d~s: I) The bit rate supportable at 6 bits~second/Hertz, 2) The minimum bit rate (i.e., payload) required by FCC rules for operation below 12 GHz, and 3) Typical utilization in terms of He digital operation and typical utilization in terms of He digital hierarchy or SONET. The FCC may not Argonne (i.e., license) the maximum bandwidth if a lesser bandwidth is sufficient for an application. L::WCH]Whase2.rpt NCHRP 3-51 · Phase 2 knot Report A1-149
Table A.~.3.3~2 Table of Microwave Nominal Bandwidths, Bit Rates, and Utilization (~1 GHz and below) ; Nominal Channel ~ Max. Bit rate at ~ ~ inimum bit rate per FCC ~ Typical Utilizat I; Bandwidth (MHz) 6 Bits/Sec /Hz rules below 11 GHz 0.4 2.4 Mbps 1.54 Mbps 1 DS-1 0\8 4.8 Mbps 3.08 Mbps 2 D6-1 1.25 7.5 Mbps 3.08 Mbps 2 DS-1 1.60 9.6 Mbps 6.17 Mbps 4 DS-1 2.5 MHz 15.0 Mbos 6.17 Mbos 4 DS-1 . . 3.75 MHz 22.5 Mbps 12.3 Mbps 8 Do 1 5.0 MHz 30.0 Mbps 18.5 Mbps 12 DS-1 / 16 DS-1 10.0 MHz 60.0 Mbps 44.7 Mbps 1 DS-3 / STS-1 20.0 MHz 120.0 Mbos 89.4 Mbos 2 DS-3 / STS-1 . . 30.0 MHz (11 GHz 180.0 Mbps 89.4 Mbps 2 DS-3 / STS-1 Band) . 30.0 MHz (6 GHz 180.0 Mbps 134.1 Mbps 3 DS-3 / STS-1 Band) _ 40.0 MHz 240.0 Mbps 134.1 Mbps 3 DS-3/STS-1 Table A.1.3.3-3 lists frequency availability by service In Me proposed Part 101 and cross references We over FCC parts and services mat share spectrum web Part 101 services. Table A.~.3.3-3 Proposed Part 101 Frequency Availability by Service . . . Frequency Bands, Radio Service MHz Common Carrier Private Radio Broadcast {Part 101) (Part 101) Auxiliary (Part 74) _ 928-929 MAS 932-932.5 MAS MAS 932.5-935 CC OFS 941 -941.5 MAS 941.5-944 CC OFS Aural BAS 952-960 OFS, MAS 1850-1990 OFS 2110-2130 CC 2130-2150 OFS 2150-2160 OFS Other (Part 15,21, 24,25,75,78, & 100) PCS ET Er MDS L;\NCHRP\Phase2.'p' NCHRP3-51e Phase2FmalRepoIt Al-150
Frequency Bands' Radio Service MHz Common Carrier Private Radio (Part 101) (Part 101) 2160-2180 CC 2180-2200 OFS 2450-2500 OFS 2650-2690 OFS 3700-4200 CC, LTTS OFS 5925-6425 CC, L1lS OFS 6425-6525 LTTS OFS 6525-6875 CC OFS __ 10555-10680 CC, DEMS OFS, DEMS 10700-11700 CC OFS 11700-12200 LTTS OFS 12200-12700 OFS 12700-13200 CC, LTTS OFS 13200-13250 CC, LTTS OFS . . 14200-14400 LTTS _ 17700-18550 CC OFS 18580-18820 CC OFS 18820-18920 DEMS OFS 18920-19160 CC OFS 19160-19260 DEMS OFS 19260-19700 CC OFS 21200-23600 CC, LTTS OFS 27500-29500 CC . 31000-31300 CC, LTTS OFS . 38600-40000 CC OFS Above 40000 TBD TBD Broadcast Aux~liary (Part 74) TV BAS Other (Part 15,21, 24,25,75,78, & 100) ET ET ISM MDS, ITFS SAT SAT TV BAS CAR SAT SAT DBS :WT TV BAS CARS _ SAT SAT TV BAS Aural BAS . Aural BAS SAT . _ . SAT SAT SAT TV BAS TV BAS TBD BAS: Broadcast Aux~liary Service (Part 74) CARS: Cable Television Relay Service (Part 78) CAR, SAT SAT CARS TBD L:\NCHRP\Pha=.rpt NCHRP3-51 a Phase2FmalReport A1-151
cc DBS: ET: ISM: Industnal, Scientific, and Medical (Part ~ 8) L INS: Instructional Television Fixed Service (Part 74) L=S: Local Television Transmission Service (Part 101, Subpart I) MAS: Multipoint Address System (Part 101) MDS: Multipoint Distribution Service (Part 21) OFS: Private Operational Fixed Point-to-Point Microwave Servicef Part 101, Subpart C and H) PCS: Personal Communication Service (Part 24) SAT: Fixed Satellite Service (Part 25) Common Camer Fixed Point-to-Point Microwave Service (Part 101, Subparts C & I) Direct Broadcast Service (Past 100) Emerging Technologies (per ET Docket ~ 92-9, not yet assigned) Design of microwave systems is very complex with many considerations. Two significant factors concerning the RF link are propagation fading and interference. Microwave systems are characterized by free space, Jine-of-sight, propagation; however, below 12 GHz the microwave radio beam is subject to refraction, or bending, as depicted in Figure A.~.3.3-~. As He figure shows, multiple rays from the transmit antenna can be refracted to amve at a receiver antenna so Hat the receiver sees a weighted sum of varying time delay of replica of He transmit waveform. When this multiparty phenomena occurs, He receiver can see a signal that is amplified or attenuated, amplitude distorted by frequency, or time delay distorted by frequency. When attenuated, fading occurs Hat increases paw loss. As far as He propagation path characteristics are concerned, the multipath phenomena described above predominates at frequencies below 12 GHz and rain attenuation predominates at frequencies above 17 GHz. For this reason, digital radio-relay systems should be mainly designed in terms of unavailability at frequencies above 17 GHz and error performance at frequencies below about 12 GHz, while in He range of 12-17 GHz bow objectives should be considered. While Here is generally a low probability of He occurrence of heavy precipitation Hat causes these events, He unavailability time it causes may differ from year to year. Statistics- based methods are available to predict He Impact of rain attenuation. c:\NCH~Whase:.rpr NCHRP 3-51 · Phase 2 Final Report A1-152
These fading conditions are variable and depend on meteorological conditions such as unusual temperature and humidity profiles. Fortunately, most of the time at most locations, conditions are normal so that only a single direct ray exists; however, to achieve 99.999% reliability, microwave links are designed with link budgets that include extra margin for fading that can range from 10 to 60 dB or more, depending on frequency, terrain, system design, weather, etc. Fade margin essentially increases allowable link loss so Tat the receive signal win be above receiver sensitivity threshold no less Wan the desired availability as illustrated in Figure A.~.3.3-2. Fading attention has been extensively studied and measured and can be modeled through statistical analysis. It can be accommodated in design by communication professionals. The U.S. standard for interference calculations is Telecommunications Industry Association (IIA), Telecommunication System Bulletin TSB-IO-F, entitled 'interference Cr~tena for Microwave Systems." Applications to the FCC for new licenses must include frequency coordination data demonstrating that the new system win not interfere with existing systems and can operate win anticipated interference from existing systems. In fact, new applicants must notify existing system operators and provide an opportunity for comments concerning Me new instaBation.~ Microwave can be employed for venally any ITS link, similar to wire or fiber, as it can support bits rates from the low speed RS 232 bit rates of 1200 to 19,200 BPS to SONET OC-3 rates (155 Mbps) and higher. Figure A.~.33-3 illustrates Me concept for a single hop (i.e., repeaterIess) link. The figure (symbolically only) depicts a terminal or multiplexer interfacing to a RF transceiver or fiber transceiver. The fiber and RF interfaces are different to accommodate different physical and link layer protocol requirements. Often in the higher speed (and higher cost) multiplexed links such as DS-l, DS-3, and SONET, microwave equipment manufacturers will use essentially Me same tenninal/mulEplexing equipment but integrated win Me RF equipment. As mentioned before, the 31 GHz band is uncoordinated. As for holders of wide area 38 GHz licenses, they need not Worry about the traditional coordinating process, as long as they remain within their allocated frequency blocL L;\NCHRmPbase2.rp ~NCHRP 3-51 · Phase 2 Final Report A1-154
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- ~ Microwave operation at low bit rates, below DS-1 (1.54 Mbps), are typically provided In Tree frequency bands: I) He unlicensed, Part 15, ISM bands (at 902 MHz, 2.4 GHz, and 5.8 GHz) using spread spectrum win directional antennae; 2) He 932.5-935 / 941.5-944 MHz band which is licensed; and 3) die 31 GHz band which is licensed, but not coordinated (i.e., no interference protection). The 31 GHz band capabilities and rules of operation for 31 GHz equipment is contained in Table A.~.3.3~. Table A.~.3.3~ 31 GHz Microwave Equipment .. _ Parameter CommenINalue Frequency band 31 0 - 31.3 GHz . . Maximum bandwidth 25 or 50 MHz _ Supportable bit rates - Standard RS 232 rates and up to 4 DS-1 (4 x 1.544 Mbps) Frequency pairs (for full duplex operation 6 at 25 MHz bandwidth 3 at 50 MHz bandwidth Maximum allowable power 50 M ~ ~ Minimum antenna pain 38.2 dB e ~ hence beams _ ~ ~ Typical maximum repeaterless range Approximately 2 miles Licensing Simple licensing, but no coordination ~0 The selection of microwave, wire, or fiber for a link involves many factors. The generic cost mode] for the trade-off was depicted in Figure A.13-~. Generally, wire or fiber is more cost effective for shorter links as might occur win closely-spaced equipment cabinets. Then, microwave is more cost effective up to He repeateriess link distance where more evaluation is required. At very high bit rates (above 600 Mbps) fiber solutions usually become more cost- effective than microwave ones. More exact cost data will be presented in He chapter on cost estimating. Economic comparisons of fiber and microwave generally involve He components in Table A.~.3.3-5. L.:`NCHRP`Phase2.rp' NCHRP3-51e Phase2FmalReport A1-157
Table A.~.3.3-5 Cost Components of Fiber and Microwave Fiber Microwave TerminaUmultiplexing equipment ~ ~ e I= Right-of-way- Tower cost = Site real estate ~ ~~ Site building/shelters Fiber costs ~ _ I ~ Fiber installation costs Tower, antenna, waveguide installation costs Power plant costs Power plant costs ~- Microwave is ~e w~eless ophon ~at can support higher bandw~ requ~rements of backbone links, video, and TOC-to-TOC links. Table A.~.3.3-6 presents a comparison of fiber versus riicrowave links. L:\NCHRP\Phase2~pt NCHRP3-51e Phase2FmalReport A1-158
Table A.~.3.3-6 Fiber vs. High Speed Microwave Radio Links Parameter Microwave Fiber Bandwidth · 12.5 KHz to over 80 · 1000 GHz in each MHz per channel, fiber depending on licensable bandwidth _ Supportable bit rates · 155 Mb~ in Anise · 10 Gbps in practice, higher possible higher possible · Up to 622 Mbps per system Residual bit error rate 1 ~"~u ~ Do' [Nme ~ ~10 ~, Maximum repeaterless distance · 2 b 50 M As · 50 to 100 Miles · 3to80 km · 80 to 160 km Typical failures · Electronic equipment ' E mron c equ patent · Fading (design for · Fiber cable breaks/ 99.999°iO reliability) cuts (1 cuVyear/500 km) Selection tradeoffs · Often low cost option · Essentially unlimited (one hop cost bandwidth/bit rate independent of path capabilities length) · Interference-free · No r~ght-of-way operation problems · No license required, · Compatible non-shared bandwidth/bit rates operation unless · Mobile/temporary/ planned flexibility · Can be low cost requirements option (high · Licensing available bandwidth/bit rate with desired and/or short distance bandwidth requirements) · Near line-of-sight · Right-of-way available available and cost effective Note ]: Residual bit error rates of i0~~3 or better are achieved win Forward Error Correction 0;EC), now available on most recent radios. The selection of fiber, wire, or microwave Wireless for an ITS application is not a process Mat can be generically made without careful consideration of many operational, technical, and cost factors. Frequently, hybrid microwave-fiber solutions provide benefits Mat are operationally useful and cost-effective. SONET examples are presented in Figure A.~33-4. ~ :~.NC~Phase2sp ~NCHRP 3-51 · Phase 2 Few Report Al-159
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A.1.3.4 Spread Spectrum Spread Spectrum is a modulation technology that has had extensive military applications for more than 20 years. More recently, spread spectrum has found application in telecommunication applications. Spread Spectrum is a candidate technology for digital cellular CIIA IS-95 Standard) and for the merging digital PCS/PCN services. :En We m~-198Os, the FCC amended Weir Part 15 rues addressing unlicensed operation to permit greater power (and range) provided spread spectrum modulation is employed to minimize interference to others and to accept interference from others. The ITS community typically refers to Part 15, unlicensed, spread spectrum as "spread spectrum." This shortening is probably an incorrect oversimplifictibon because spread spectrum is applicable to virtually any frequency band: licensed or unlicensed. Currently, most legacy FCC regulations do not accommodate spread spectrum, although the FCC seems to be open to suggested rule changes Cat improve efficiency of spectrum utilization Cat might eventually allow wider deployment of spread spectrum. It should be noted that experts disagree on whether spread spectrum is a superior alternative to enhanced traditional modulation methods. Time and We marketplace will provide the answers; however, current Part 15 rules require the use of spread spectrum to increase the power to ~ watt and achieve the resulting additional range. There are two commonly employed versions of spread spectrum: I) frequency hopping (BLISS); and 2) direct sequence (DSSS). Frequency hopping modulates We casner signal in nonnal manner, but hops We catner frequency within We spread band (i.e., much wider than We modulated signal bandwidth) at constant rate (i.e., hops per second). The hopping pattern is according to a pseudorandom number aIgonthm ~at, when initialized and synchronized at bow transmitter and receiver, permits communication. Receivers or transmitters not synchronized do not receive or interfere except for the short random times Cat He same carrier is selected. Figure A.~.3.4-1 illustrates the FElSS concept. FHSS uses essentially standard radio electronic circuits that are modified to accommodate pseudorandom number generation and He frequency agility. The Part 15.247 rules are summanzed in He following table (Table A.~.3.4-~. :\NCHRP~Phasc:~p: NCHRP3-51~ Phase2F~nalReport A1-161
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Table A.~.3.4-1 Summary Part 15.247 Rules for Frequency Hop Spread Spectrum . . Maximum Number of Modulation Separation of Hop Hop Average Time on Band Bandwidth Frequencies Frequencies a Frequency Minimum 25 kHz or .4 second within 902-928 MHz 500 KHz limits of 20 dB 50 minimum a 20 second attenuated of period modulated bandwidth 2.4-2.4835 GHz Minimum 25 kHz or .4 second within 5.7-5.8 GHz 1 MHz limits of 20 dB 75 minimum a 30 second attenuated of period modulated bandwidth _ An important parameter of spread spectrum is processing gain, which for frequency hop, is defined as: PG = lOlog~numberoffrequencies) 10 log (50) = 17 dB in 902 MHz band 10 log (75) = 18 dB in 2.4 and 5.7 GHz bands Of course, a greater Lumber of frequencies can be employed resulting in greater processing gain Hat provides better noise/interference immunity, but usually at greater cost. Typically, modulation format supporting from less than .15 to 2 bit/second/Hertz are employed, so Hat approximate maximum data rates supportable are as shown in Table A.~.3.4-2. Table A.~.3.4-2 Part 15.247 Frequency Hop/Maximum Supportable Bit Rates Maximum ~ Modulation Maximum Bit rate Maximum Bit rate Maximum Bit rate Band Bandwidth .5 bitsiseclHz 1/bit/secondlHz 2 bit/secondlHz 902-928 MHz 500 kHz 250 MbiVsecond 500 k bibsecond 1 MbiVsecond 2.4-2.485 GHZ 1 MHz 500 k bits/second 1 MbiVsecond 2 MbiVsecond 5.7-5.8 GHz Most use substantially less modulation bandwidth supporting He typical RS 232 bit rates of 300, 1200, 2400, 4800, 8600, 19,200 bits/seconds. L:\NCH]Wbasc2arpt NCHRP3-51e Phase2FmalReport A1-163
Direct Sequence Spread Spectrum (DSSS) spreads (and continuously occupies) Me modulation bandwidth, as depicted in Figure A.1.3.4-2, by multiplying We signal by a pseudorandom sequence of binary (+1, -1) Rat is an integer multiple, higher, bit rate (see Figure A.1.3.4-3). l The ratio of the unspread bandwidth to the spread bandwidth is called processing gain. If Me transmitter and receiver employ the same pseudorandom sequence generator and Hey are synchronized, then He receiver can recover He unspread signal as illustrated in Figure A.~.3.4-3 with gain, n = 3. If He transmitter and receiver are not synchronized or Hey have different pseudorandom codes (sequences), Den He received data w~11 be furler scrambled and uninterpretable, and have noise like properties when high processing gain is used and code sequence is properly selected. Processing gain for DSSS is defined in several different ways in He literature Hat are essentially, but not exactly, equivalent: I. Ratio of spread modulation bandwidth to unspread modulation banded. 2. Ratio of modulation bandwidth (FCC definition) to data rate. 3. Ratio of pseudorandom bit rate to data bit rate (always an integer), or number of chips per bit. These ratios are typically expressed in decibels: Processing gain (PG) = 20 log (ratio) c:\NCHRP`Phasc~rp ~NCHRP3-51n Phase2F~nalReport A1-164
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Extensive research over many years has been expended to develop pseudorandom codes that are easy to generate, can be easily synchronized, are repeatable at bow transmitter and receiver, and have essentially noise charactenstics to over signals except He same synchronized code. These codes are referred to in Be literature as Pseudonoise (PN) sequence and are efficiently generated by Linear Feedback Shift Register BIER). If unique "orthogonal codes" are assigned to several (transmut/receive pairs) users, Men multiple users can share (i.e., coexists on Be same frequency band in the same geographic area. This technique can be employed to provide what is referred to as "Code Division Multiple Access" or CDMA. Commercial service examples of multiple (user) access me~ods are shod n in Be Table A.~.3.4-3 below. Table A.~.3.4~3 Alternative Multiple (User} Access Methods Name ~ Abbreviation ~ Example' (U.S.) Frequency Division l\Aultiple Access FDMA AMPS Cellular (Bellcore Standards) Time Division Multiple Access TDMA TDMA Digital Cellular (TIA, IS-54, IS-136) Code Division Multiple Access CDMA CDMA Digital Cellular (TIA IS-96) l L:\NCHRP\Phasc2.rpt NCHRP 3-51 · Phase 2 Final Report A1-167
Table A.1.3.4-4 compares frequency hop and direct sequence spread spectrum: Table A.~.3.4~4 Characteristics of Frequency Hop and Direct Sequence Spread Spectrum . Characteristic Frequency Hop Direct Sequence Spread method Hop to different carrier Spread modulation frequencies with narrow- bandwidths and decrease modulation bandwidth spectrum amplitude in modulation bandwidths Noise/interference Depends on random hopping, Despread~ng suppress immunity otherwise similar to tradition narrowband interference and modulation noise, but not wideband thermal noise. Less interference to others. _ Time resolution, Direction Same as narrowband Wider bandwidth supports Funding (DF) better time resolution, thus beKer OF resolution Interception, - Easy to identify, but required FH Lower amplitude, wider eavesdropping immunity receiver to track. spectrum difficult to detect. Military significance. Multiple access Essentially same as narrowband. With appropriate system design and PN codes, multiple users can coexist. Comment Can be implemented with Gaining favor in cellular and essentially traditional components FHWA tests. and equipment. Thus, early favorite. While CDMA is being employed in the cellular industry, Part 15, unlicensed, spread spectrum has tended only to employ basic DSSS and not incorporate CDMA multiple access. The reasons are: I. Part 15.247 requires FHSS or DSSS to use ~ watt of transmit power essential for greater range. Spread spectrum has essentially the same range as non-spread spectrum assuming no interference or mul~pa~. 2. CDMA is more complex and usually requires a base station to assign user codes and implement power control to mitigate the near/far problem. Base stations are typically not employed in part 15 applications. u\NCHRP\Phase2`p ~NCHRP3-51 · Phase2FmalReport A1-168
3. Multiple access by FDMA or TDMA is easier to implement and control. The specific Part 15-247 are summanzed in Me following Table A.~.3.4-5. Table A.~.3.4~5 Part 15.247 Direct Sequence Spread Spectrum (DSSS) Operations Parameters Parameter Requirement Bands 902 - 928 MHz 2.4 - 2.4835 GHz 5.725 - 5.875 GHz Processing Gain (minimum) ~ ~ ' U~ ~ Power (same for FH and DS) 1 watt maximum (30 dBm) Antenna (same for FH and DS) 6 dbi* (Greater values may be used, but transmit power must be reduced, i.e., EIRP limit of 36 dBm) _ Power Density Maximum of 8 dBm over any 3 kHz band averaged over 1 second *This is a recent rule arid certain manufacturers have legacy waivers to exceed 6 dbl. It is instructive to assume free space propagation and calculate Geodetical range limits udiiz~ng Equation A.~.3.~-2. These are summanzed in Table A.~.3.~6 below. Table A.~.3.4-6 Part 15.247 Spread Spectrum Maximum Repeateriess Distances | Parameter l Band | 2.4 GHz Band 5.8 GHz Band | Transmit Power, Pt. dBm l 30 dBm | 30 dBm 30 dam l | Receiver Sensitivity, P., dBm l -90 dBm | -90 dam -90 dam Link Budget, Pb, dB l -120 dB | -120 dB -120 dB Frequency,GHz | 0.915 GHz | 2.41675 GHz 5.8 GHz Range, km, O dbi gain Antenna | 26.22 km | 9.93 km 4.14 km l Range, km, 6 dbi gain Antenna 52.31 km 19.80 km 8.25 km 1.6 km = 1 mile L;\NCHRP`Phasc2.'p ~NCHRP 3-51 · Phase 2 FmaI Report A1-169
There are reports of successful communications at distances approaching these ranges on tall structures/te~rain with clear line-of-sight; no obstructions or intervening terrain, and no interference. Range can quickly deteriorate to ~ km or less with obstacles including foliage resulting usualRy from low antenna heights. It should also be noted that no fade margin is aBowed in these calculations and that these ranges are valid for both DS and FS. The maximum supportable data rates for DS can be estimated based on the following: I. Assume minimum spreading (processing gains of 10 dB or 10 (i.e., 10~°~°~. 2. Part 15.247 has no requirement on minimum/max~mum modulation bandwidth within the bands for DS. Thus, a user may use an entire band or create multiple channels within a band. 3. Thus, using We definition Mat processing gain is modulation bandwid~/bit rate: Bit rate maximum = Bandwid~/Processing Gain We are not employing Me FCC's definition of processing gain for an easy-to-calculate approximate estimate. Thus, Me Tree ISM bands in Part 15.247 can support approximately Me following maximum bit rates as shown in Table A.~.3.4-7. Table A.~.3.4~7 Maximum Theoretical Direct Sequence Spread Spectrum {DSSS} Bit Rate Band (Bandwidth) | Maximum Bit rate 915 + 13 MHz (26 MHz) 2.6 Mbits/second z ~ GEC - (335 MHz) 8.35 Mbits/second 5.8 1.075 GHz ~ (150 MHz) 15 Mbits/second The exact available bit rates should be determined from vendors of equipment. Most vendors split Me band into channels to support multiple channels in a potentially interfering geographical area and also to support full duplex operation on non-overIapping frequency bands Mat can be ~:`NCHR~Phase2 apt NCHRP 3-51 · Phase 2 Final Report A1-170
separated in integrated transceiver/antenna equipment. Commercially, available bit rates typically include: 1. RS-232 compatible bit rates: 1200, 2400, 4800, 9600, etc. bps, full duplex. 2. T] or E! bit rates at 1.544 Mbps and 2.048 Mbps, full duplex. It should be noted Mat few standards exist for Part 15.247 equipment other Man the minimal FCC regulations. Thus, interoperability of equipment from different vendors is very unlikely. Furthermore, each vendor has complete freedom to define his own: I. Channel plans (i.e., carrier center frequencies and bandwidths, plus number of supported channels) 2. Modulation format 03PSK, QPSK, etc.) 3. Processing gain 4. Supported bit rates F Jurisdictions considering spread spectrum should carefully evaluate the current and future impact of unlicensed operations, which provides no legal protection from interference whether unintentional or malicious. Current unlicensed applications in the band include: 1. RF toll tags, 2. Cordless phones (the higher power provides greater range), 3. Wireless LANS OEEE 803. ~ ~ Standard), 4. Wireless PBXs, and 5. Many data network applications. t:WC~Phase:.rp: NCHRP 3-51 · Phase 2 Final Report A1-171
Perhaps more troublesome, Part 15.247-operation actually has secondary rights in the band to certain over services licensed in over parts of Me FCC regulations. Table A.~.3.4-S provides an overview of these licensed services. Thus, jurisdictions planning Part 15.247 spread spectrum, should carefully consider cnticality of communication in light of potential interference. Several techniques may be used to minimize interference problems. These include: I. Using higher processing gain (10 dBis minimum); 2. Using a directional antenna that greatly attenuates potential interferers not in We beam; 3. Using network protocols Tat accommodate interference; and 4. L`ocadng systems in geographic areas Tat are unlikely to have interferers. Table A.~.3.4~S Part 15 ISM Bands, Shared Service Priority List Band Service Applicable FCC Shared Priority Rules 902 - 928 MHz ISM Part 18 1 US Government Radar 2 US Gov. Fixed & Mobile Radio 3 Location Monitoring Part 90 4 Amateur Part 97 5 ~ Unlicensed ~Part 15 ~6 2.400 - 2.4835 GHz ISM Part 18 1* 1** Government Radar 2* 5** * 2.400-2.450 GHz Studio Microwave Part 74 2** Fixed Point-to-Point Microwave Part 94 2** **2.450-2.4835 GHz Land Mobile Part 90 3** Radar Systems Part 90 4** Amateur Part 97 3* Unlicensed Part t5 4* 6** 5.725 - 5.875 GHz ISM Part 18 1 Government Military Radar 2 Fixed Satellite (Above 5.850 G Hz) Part 25 3 Amateur Part 97 4 Unlicensed Part 15 5 6 L:\NCHRP\Phase2.rpt NCHRP3-51e Phase2FinalReport A1-172
(1) Each part of CFEt 47 (i.e., 15, 18, 21, 74, 90, 94, 97, etc.) only defines primary or secondary status to other parts. This table provides Sonority based on our interpretation. The FCC rules should be reviewed when precise interpretations are required. * 2.400 - 2.450 GHz ** 2.450 - 2.4835 GHz Spread spectrum is an excellent technology that helps to reduce harmful interference to others and to tolerate interference from others. Additionally, it has He following benefits: Better time resolution of w~de-band received signals and thus better range and direction resolution for location applications. · Better nape security due to hopping or direct sequence spreading Hat makes eavesdropping more difficult. The FCC regulations provide very few allocated, licensed or unlicensed, bands for spread spectrum; however, FCC policy seems to be moving toward regulations Hat are more accoInmodadng. Licensed spread spectrum bands would undoubtedly prove veer useful in many ITS applications. A.~.3.5 FCC Part 90' Private Land Mobile Radio Sen~ices Private L,and Mobile Radio (PL`MR) services rules of service are covered in Part 90 of He FCC rules, CFR 47. Most ITS wireless operations are conducted under this part. (Part 15, Unlicensed, and Part 94, Private Operational Fixed Microwave Service are over parts win significant ITS applications.) PEMR services are important to ITS for He following reasons: The allocated frequencies are in legacy bands below 512 MHz, In He 800/900 MHz bands, and to a lesser extent in hider microwave bands. The lower frequency bands can often support significantly greater repeaterless ranges by sky wave or ground wave propagation. L:\NCHm.Phasc2.rp ~- NCHRP 3-51 · Phase 2 Fmal Report A1-173
The traditional bandwidths allocated have been 25 kHz, which can support 1200 - 19,200 bits/second digital bit rates using more advanced modulation techniques. New FCC regulations win decrease the bandwidth avocations thus increasing the number of available traditional voice channels to allocate. The FCC has recently issued severe Notices of Proposed Rule Making (NPRM) or actual orders changing rules. These rules offer ITS opportunities, but require understanding and llS community consensus and outreach to achieve potential benefits. The Part 90 services are presented in Table A.~.3.5-~. The frequencies assigned in Part 90 are not devoted exclusively to Part 90 services or applications, and may be assignable to multiple Part 90 subservices, Part 94, Part 2l, Part 15, etc., applications. Manv Part 90 services are assigned frequencies on a shared. but licensed. basis. ~,, The combinations and details of these multiple and shared assignments are based on more Man 50 years of legacy evolution, especially in Me lower frequency bands below 512 MHi. Thus, it is not possible to easily present a concise listing of all frequency assignment and application. Table A.~.3.5-2 contains a summary listing of bands. Part 90 should be consulted for the details including: Frequency, channelization, and banded, Transmit power limits, Service/applicabon frequency assignments, Licensing requirements, Eligibility requirements, and Over rules. f L;\NCHRP\Phasc2.~t NC~ 3-51 · PI 2 ~ Rent A1-174
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Tabte As~a3~5~2 Summary of Frequency Bands in Part 90 . | B an d | Au t ho rized Servi ces 70 - 1120 kHz Radio location . 530 - 1700 kHz TISIHAR (90.242) .. 610 - 1800 kHz Public safety, industrial .. 2000 - 3000 kHz Public safety, educational 3000 - 10,000 kHz Public safety, industrial | 10,000-25,000 kHz | Industrial(longdistancecircuit) 25 - 50 MHz Public safety 72 - 76 MHz 1 Radio call box (90.241) 150 - 174 M H. z ~ I n d ustrial se rvices, I an d tran s po rtatio n 216 - 200 MHz Telemetry (90.259) 220-222 MHz 1 Subpart T 421 - 430 MHz | Radio location services 450 - 470 MHz Industrial, road transportation, public safety 570 - 512 MHz | Subpart L (TV broadcast sharing) 806 - 821 M Hz | Specialized Mobi le Radio ( S M R) 851 - 866 MHz Subparts' specialized mobile radio (S VIR) 896 - 901 MHz | Subparts, specialized mobile radio (SMR) 929 - 930 MHz T Paging (90.494) 935 - 940 MHz | Subparts, specialized mobile radio (SMR) 1427 - 1435 MHz Telemetry (90.259) 2450 - 2500 MHz | Shared with ISM band 2900 - 3700 MHz | Radio location 5250 - 5650 MHz Radio location 8400 - 8500 MHz | All except industrial and radio location 10,550 - 10,680 MHz ~ All except radio location Bands above 13~400 MHz Radio location L;\NCHRP\Phase2.rpt NCHRP 3-51 ~ Phase 2 Fmal Report A1-177
A.1.3.5.1 Part90 Spectrum Refarming In 1992, Me FCC issued a "Notice of Proposed Rulemaking," PR Docket No. 92-235, Mat announced plans, and solicited inputs, for Me adoption of new rules to allow the introduction of advanced technologies to support more effective and efficient use of Me crowded "Private Land Mobile Radio" (PEMR) spectrum governed by Part 90 rules. This is referred to as "reforming bands." The onginal plan was to replace Part 90, which has many inconsistencies resulting from more than 40 years of evolution, who a new Past S8; however, in users group comments data was provided Mat estimates the PEMR spectrum supports an instaHed equipment infrastructure with aggregate value of $25B. Thus, a more evolutionary plan that upgrades but maintains the current Part 90 was presented in FCC Number 95-255 document adopted June 15, 1995. Itis the Report and Order that described these changes and time lines. The reforming rulemaking refers to PEAR services licensed under Part 90, Subparts B. C, and D (see Table A.~.3.5-~), and addresses Me 150-174 bDHz, 421-430 bDHz, 450470 ADHz,and 470- 512 MHz frequency bands. Specifically, refalming report and order defines new rules with following purpose and goals: · Adopt new narrowband channel plans, but interleave new channels between current channels, Bus allowing excising assignments to remain on channel. · Encourage transition over a ten year period by not type accepting new equipment unless it meets new minimum speck efficient standards or is multimode (i.e., current 25 Liz channel spacing and new narrower spacings). Users do not have to convert, but should find it advantageous when new equipment is purchased. · Specify new technical standards (e.g., transmitter power, emission limitations, and frequency stability) Mat can accommodate a wide range of technologies and products. · Consolidate Me current 20 radio services into fewer services (ideally less than 5) to create more efficient allocation frequency pools (e.g., currently no forestry service in NYC, but unused frequencies). ~:wcm~.~ NCHRP3-51e Ph~2Fm~Re~n A1-178
Table A.1.3.5.1-1 lists the selected amended Part 90 frequency bands including the refarm~ng bands as well as others. Included In the table are channel spacings and au~onzed channel bandwidths. As opposed to requ~nng users to upgrade, He new rules encourage upgrade over an anticipated lO-year nonnal replacement cycle by not type accepting new equipment for the refanning bands unless it meets He new rules. After August I, 1996, type acceptance win be granted only if one of He following is met: Single or multimode equipment with a maximum banded of 12.5 kHz; 25 MHz of bandwidth for multimode equipment that is also capable of operating on channels of 12.5 kHz or less; or 25 kHz bandwidth operation equipment is permitted by employing spectrum efficiency standards of at least one voice channel per 12.5 kHz of bandwidth or data channel operations supporting at least 4800 bps per 6.25 kHz of bandwidth (i.e., .768 bits/second/hertz). This will permit spectral efficient TDMA equipment to be deployed. On January 1, 2005 the spectral efficiency requirements win be reduced from 12.5 to 6.25 kHz. The refarniing order contains a Further Notice of Proposed Rulemaldug (FNPRM) to consolidate frequency coordination. Currently, the refanning bands are divided into 20 services for He purposes of frequency coordination. These current services are listed in Table A.~.3.5.~-2, as: · The number of transmitters as of December, 1994; \ The number of assigned 25 kHz channels (some channels are shared by different services in both the Vim and UHF bands); and The frequency coordinator. It should be noted that this definition of services for frequency coordination purposes is close, but not the same, as the definition of services under Subparts B. C, D, and E (see Table A.~.3.5-~. The FNPRM directs He PLUM users community to assess their needs and submit a consensus L:~h~.~t NC~3-51 · Ph~2F~Re~n A1-179
Table A.~.3.5.~-1 Amended Part 90, PROS Standard Channel Spacing/Bandwidth . Frequency Band (MHz) Channel Spacing (kHz) Authorized Bandwidth (kHz) 25 - 50 ~20 ~20 72 - 76 20 20 150 - 174 1 (25 kHz) 7.52 25/11.25/623 220 - 222 5 4 421 - 430 (25 kHz) 6.52 25/11.25/623 . 450 - 470 1 (25 kHz) 6.52 1 25/11.25/6~3 470 - 512 1 (25 kHz) 6.52 1 25/11.25/623 806 - 821/851-866 1 25 20 ._ . 821 - 824/866 - 869 1 12.5 1 20 896 - 901/935 - 940 12.5 13 0 929 - 930 1 25 1 20 proposal within Free months of He effective date of Be Report and Order on how to consolidate frequency coordination arid create a consolidated real-dine database of assigned frequencies. The FNP~M cites a goal of 24 coordination categories based on Me user proposal justifiable categones. The reasons for Me consolidation are: More efficient and effective frequency assignments among low and high use groups; Simplify interservice shanng; 2 Prior to August 16, 1995. For stations authorized on or after August 16, 1995, type acceptance of equipment after August 16, 1996 must be capable of operating on channel bandwidths of 12.5 klIz or less and support one voice channel per 12.5 kHz of bandwidth and a minimum data rate of 4800 bps per 6.25 Adz of bandwidth (i.e. about .768 b/s}Hz). 3 Multimode capable of operating on He old 25 kHz and He new channel spacing/bandwid~ can be type accepted after August 1, 1996 .~NCHRP\.Phase:.rp ~NCHRP 3-51 · Phase 2 Penal Report Al-180
Table A.~.3.5.~-2 Private Land Mobile Radio Services and Frequency Coordinators Description of Private Land Mobile Radio Services Below 470 MHz Number of Number of Frequency Transmitters Channels Coordinator (see list below) VHF UHF 3,575,223 109 289 NABER(PCIA) 1,550,394 75 86 APCO 1,382,647 80 78 APCO 843,747 815 30 ITA 826,773 38 48 IMSA 768,551 40 UTC 742,454 119 20 MR 419,436 19 74 IMSAIIAFC NABER(PCIA) 356,607 58 38 MSHTO .. 340,913 103 36 PFCC of API 335,109 43 38 MSHTO 308,227 52 48 MRFAC 182,598 56 30 ATA 137,640 10 36 TELFAC 123,864 36 24 ITLA Business: educational, religious, hospital, small business, etc. Police: protection of citizens in emergency and non-emergency situations Local Government: official functions of governmental activities Special Industrial: heavy construction (roads/bridges), farming, and mining Fire: fire protection services by state and local entities Power: electricity, natural or manufactured gas, water, and steam Railroad: rail transport of passengers and freight Special Emergency protection of life and property for emergency medical care Forestry Conservation: protection and conservation of forests and wildlife Petroleum: production, collection, and refining petroleum products by pipeline Highway construction and maintenance of highway activities Manufacturers: plants, factories, mills, and shipyards Motor Carrier: trucking (short and long haul) and public buses Telephone Maintenance: daily repair and emergency restoration Taxi Cabs: nonscheduled passenger land transportation L.\NCHR~Phasc2.rpt NCHRP 3-51 · Phase 2 Final Report A1-181
Description of Private Land Mobile Number of Number of Frequency Radio Services Below 470 MHz Transmitters Channels Coordinator (see list below) VHF ~ UHF Forest Products: logging,hauling,and ~119,428 | 106 | 50 | FIT l manufacturing of lumber products Automobile Emergency: dispatching of 35~877 23 4 MA repair trucks, tow trucks, etc. Relay Press: publication and operation of 22,017 12 4 AN PA newspaper and press Video Production: producing, 12,794 18 O AMPTP videotaping, filming of movies and television programs l l l l l Totals: 20 Radio Services (includes 553 324 EMRS) I 12,084,299 1 1 1 1 AAA Amencan Automobile Association AASHTO American Association of State Highway and Transportation Officials AAR Association of Amencan Railroads AMPTP Alliance of Modon Picture and Television Producers ANPA AmencaD Newspaper Publishers Association APCO Association of Public Safety Communications Officials - International, Inc. API Amencan Petroleum Institute FIT Forest Industries Telecommunications LAFC International Association of Fire Chiefs IMSA International Municipal Signal Association ITA Industnal Telecommunications Association, Inc. 1TLA International Taxicab and Lively Association MRFAC Manufacturers Radio Frequency Advisory Committee NABER National Association of Business and Educational Radio (merged win PCIA) PCLA PFCC Personal Communications Industry Association Petroleum Frequency Coordinadng Committee TELFAC Telephone Maintenance Frequency Advisor Committee UTC L:\NCHRP\Ph;~se2.rpt Ublides Telecommunications Committee NCHRP 3-51 ~ Phase 2 final Report A1-182
Organize channel allocation to more easily use advance technology; More effectively allocate He newly created channels; and · Provide a mechanism for exclusive channel use of He expanded channel capacity. This urn also allow more efficient enlacing. If a consensus user proposal cannot be reached, the FCC says it win make a decision. Competing frequency coordination services will be allowed in each coordination category (or group). Refarming could have important ITS implications: Access to lower frequencies wad greater coverage potential. (This might be essential for rural applications.~; Substantially greater number of channels becoming available for new applications; Streamlined technical rules permitting more efficient trundling and TDMA. (Spread spectrum will be allowed, but only for police applications.~; · It promotes interoperability with 12.5 kHz equipment used by Federal Government users (e.g., FBI, DOD), and He new APCU-25 standard developed by the public safety community; It promotes upgrades of existing PEMA systems (e.g., highway maintenance). (Some will require network reconfiguration due to new technical rules reducing maximum allowable powers and lower maximum antenna heights.~; and The data rate capacity of the channels ranges from 4,800 bps (6.25 kHz bandwidth) to 19,200 bps (25 Lutz bandwidth) at BERs between i0~3 and lo-6 . The ITS community needs to actively promote its needs during He transitional period. L:\NCHTWhase2.rpt NCHRP3-51e Phase2F'nalReport A1-183
A.~.3.~.2 Transportation /nfrastruefure Radio Service {T/RSJ - AVW[MS ~ February, 1995, the FCC adopted rules (FCC 9541, February 5, 1995) for Automatic Vehicle Monitoring (AVM) under a new Subpart M stardng at Part 90.350. These new rules replace interim (1970) AVM rules in 90.239 (deleted). The title of Subpart M is "Transportation Infrastructure Radio Service" AIRS) and is intended to allow new radio-based technologies for ITS applications. The AVM name is changed to Location and Monitoring Service (LMS) and is Me first radio-based technology service under this subpart. The LMS will share spectrum in the 902-928 MHz band with over users (see Table A.~.3.4-~. The FCC 9541 Report and Order (R&O) modifies and eliminates outdated regulations that have not kept pace with technological evolution that is supportive of ITS applications. The key elements of Me R&O are as follows: Defined two general categories of EMS technologies multilateration, or w~deband Including direct sequence spread spectrum, and non-muldIateration, or narrowband. The subbands and ban dwid~s are in Table A.13.S.2~. Table A.~.3.5.2~1 EMS Frequency Subbands Subband(MHz) ~ System LicenseBandwidths tMHz) ~ Power(Watts) 902.00 - 904.00 Non-multilateration2.00 MHz 30 904.00 - 909.75 I Multilateration 5.75 MHz | 30 l 909.75 - 921.75 | Non-multilateration 12.00 MHz | 30 l 919.75 - 921.75 Both (shared equally) 2.00 MHz 30 921.75 - 927.25 1 Multilateration 5.75 MHz 1 30 927.25 - 928.00 i Multilateration (Forward links, 250 KHZ) | 300 Permit Multilateration LMS systems to locate any object (i.e., vehicle or not). · In addition to locations and monitoring information, permit LMS systems to transmit about a mobile unit, status and instructional inflation including voice and non-voice. Under ~ :\NC~Whase2.rp ~NCHRP 3-51 · Phase 2 Fmal Report Al-184
certain conditions related to public safety or special emergency radio service, L`MS systems may interconnect with the Public Switched Network (PSN). Expand EMS license eligibility to all entices eligible under Part 90 and to allow licensees, under qualifying critena, to provide commercial service to paying subscnbers. Establish exclusive license for multilateration systems in Major Trading Areas (MTAs) Trough competitive bidding, but provide a mechanism for existing operators to godfather current licenses. License non-multilateration systems on a shared basis in designated subbands. Clarify what constitutes harmful interference from Part 15 device and amateur operations as defined In Part 90.361. (Basically, indoor operations and operations with low antenna heights win not be considered hannfill interference.) Make provisions for furler testing of muldlateradon systems to ensure that interference to Me existing, widely deployed, and expanding Part 15, unlicensed operation is minimized. These rules have been defined to accommodate various EMS services from multiple vendors. The multilaterabon, or wideband, licenses will support vehicle location using a broad band signal. Technically, a w~deband signal can be received with better time resolution (Time Resolution B0tdwid~ that can employ several techniques to accurately locate a signal source, typically a vehicle. Pulse ranging techniques are typically employed. Thus, LMS services will be available for: Vehicle location within approximately 50-200 feet depending on infrastructure and interviewing te~Ta~n/obstacles; Bit rates for voice/data from 1200 bps to in excess of 400,000 bps; and ~:\NCHRP`Phase~rp ~NCHRP 3-51 · Phase 2 final Report Al-185
· If voice is not supported, packet technology can be employed and packet size can be tailored for short, efficient, location messages. Unlike GPS band location systems, these multilateration services can offer two-way and other communication and integrated fleet management, emergency, vehicle secunty, smart/probe, communication services. These EMS services should not be as susceptible as satellite to shadouang/facing in urban areas. Additionally, EMS services ability to integrate location and communication services should prove cost-effective when available. The non-multilateration cards, essentially narrowband, are intended for non-commercial applications and shared spectrum usage. Toll/RF tags are the best examples. Many of these applications can be implemented under the Part 15 unlicensed rules, but can increase power and achieve some interference protection benefits by licensing under Part 90. It should be emphasized that Part 90 EMS operations in 902-928 MHz band have primary status and Part 15, unlicensed, operation has secondary status. Thus, in Me event of interference, Part 15 applications must cease operation or change installation or configuration to eliminate interference. A. 1.3.5.3 Meteor Burst Communications the 1930s, researchers observed that ionized trails of meteors entering Me ear~'s atmosphere win reflect radio waves. In the 1940s and 1950s, much research was conducted on meteor burst propagation charactenstics. In Me 1950s and 1960s, as satellite technology emerged for '`beyond line-of-sight" communication, interest in meteor burst communication waved. Nevertheless, meteor burst communication has achieved cost effective application primarily in government sponsored remote sensor data collection. The U.S. Forestry Service has placed snow/weather sensors on remote western mountaintops to measure snow depths and melting to predict spring river~creek flow. This "SNOTEL" program uses meteor burst communication from remote mountaintop sites to communication hubs. The mutiny uses it as a backup to potentially vulnerable satellite long range links. Meteor burst technology is also employed for truck fleet management applications. ~:wCHRP`Phasc2.rps NCHRP3-51. Phase2FinaIReport A1-186
The meteor burst communication channel phenomenon is illustrated in Figure A.~.3.53-~. When a meteor trail sweeps into the earths atmosphere and is properly oriented, the transmit signal is reflected to We receiver for as long as the trait persists. The occurrence of a properly oriented trail is a statistical phenomenon in both start time, total time of occurrence, and channel characteristics. This statistical nature makes meteor burst communication unsuited for tight real- time applications. Table A.~.3.5.3-1 illustrates typical parameters for meteor burst communication channels. The ITS applications for meteor burst focus on rural locations where data sources and destinations can be sparsely located over an extended- geographical area. The specific applications include: · Automated weather stations; · VMS; Non-real-time control data such as timing plans; · Kiosk database updates (not remotely interactive); Non-real-time sensor data (monitored, but not control); and Fleet management (e.g., CVO, transit). ; L:\NCHRP\Phase2.rpt NIP 3-51 · Pee 2 Fed Reed A1-187
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Table A.~.3.5.3~1 Typical Meteor Burst Communication Parameters Parameter | Value Coverage Distance 2000 km (1250 miles - maximum) Carrier Frequency 40- 100 MHz Transmit Power 200 - 2999 Watt Bandwidth 100 kHz Typical Bit Rates 1200- 19,200 bps(intermittent) Trail Duration 0.2 - 1.0 seconds Information Duty Cycle 2.5 - 5.0 percent . Average Message Delay 10 - 80 seconds . Worst Message Delay ~ ~ em_ The FCC rules for meteor burst are in 90.250 and only authorizes operations for the state of Alaska. Coterminous U.S. operation is by FCC developmental authorization defined in Subpart Q of Part 90. L:~h~.~t NCH~ 3-51 · PI 2 Few Ream A1-189
