meteor burst communications- value in adverse conditions. naval postgrad school thesis. mark...

8/8/2019 Meteor Burst Communications- Value in Adverse Conditions. Naval Postgrad School Thesis. Mark Gates.1992

1/75

NAVAL POSTGRADUATE SCHOOLMonterey, California

AD-A248 632

S uDTIC( RAD ;.. A 2 1992.

THESISSurvivability of Meteor BurstCommunication Under AdverseOperating Conditions

byMark A. GatesMarch 1992

Principal Advisor: Thomas A. Schwendtner

Approved for public release; distribution is unlimited

92-09851V!1 4!!r Ik!Jiil I9

Tel: Meteor Burst Communications (MBC) has unique characteristics verses other forms of wireless and wired communications with regarurity, survivability after an attack or natural catastrophe, simplicity, ease of link establishment and re-establishment, etc. This will be valuab

onwide for smart transport, energy, and other critical telemetry, voice messaging, emergency-event communications and back up to other fommunications. SkyTel plans use of nationwide MBC for full coverage (even in most remote areas) with these essential features along withsh nets for high two-way communications capacity along transport routes, cities and other areas.


2/75

UnclassifiedSECURITY CLASSIFICATION OF THIS PAGE

REPORT DOCUMENTATION PAGEla REPORT SECURITY CLASSIFICATION lb RESTRICTIVE MARKINGSUnclassified2a SECURITY CLASSIFICATION AUTHORIT't 3 DISTRIBUTION/AVAILABILITY OF REPORT

Approved for Public Release;2b DECLASSIFICATION/DOWNGRADING SCiEDULE distribution is unlimited4 PERFORMING ORGANIZATION REPORT NUMBER(S) S MONITORING ORGANIZATION REPORT NUMBER(S)

6a NAME OF PERFORMING ORGANIZATION 6b OFFICE SYMBOL 7a NAME OF MONITORING ORGANIZATIONNaval Postgraduate School (If applicable) Naval Postgraduate SchoolE(C6c ADDRESS (City, State, and ZIP Code) 7b ADDRESS (City, State, and ZIP Code)Monterey, CA, 93943-5000 Monterey,CA, 93943-5000

8a NAME OF FUNDING/SPONSORING Bb OFFICE SYMBOL 9 PROCUREMENT INSTRUMENT IDENTIFICATION NUMBERORGANIZATION (Ifapplicable)

8c ADDRESS (City, State, andZIPCode) 10 SOURCE OF FUNDING NUMBERSP,.y . . k ement No 'rOl., t N, I V'.,

11 TITLE (Include Security Classification)SURVIVABILITY OF METEOR BURST COMMUNICATION UNDER ADVERSE OPERA'rINGCONDITIONS12 PERSONALAUTHOR(S) Mark A. Gates13a TYPE OF REPORT 13b TIME COVERED 114 DATE OF REPORT (year, month, day) j15 PAGF COuNTMasters Thesis From To 1992 MARCH 716 SUPPLEMENTARY NOTATIONThe views expressed in this thesis are those of the author and do not reflect the official poili(v of ,(IItlion ofthe Department of Defense or the U.S. Government17 COSATI CODES 18 SUBJECT TERMS (continue on reverse if necessary and identify by OIo(k ,urtmbv,)

FIELD GROUP I SUBGROUP Meteor liurst Comniricationi19 ABSTRACT (continue on reverse if necessary and identify by block number)This thesis is a study of the survivability and reliability issues associated with operating netc(or burstcommunication systems under adverse conditions. Meteor burst communication relies on tht. phcbon)(' t1,un vfreflecting radio waves off the ionized trails left by meteors as they enter the atnosphere and disintegratt.The systems' rapid deployment capability, mobility, and operating characteristics make it ideil fOr dl.'astirand emergency communications Adverse conditions such as ionospheric disturbances, polar region anOt~idii..sun-spot activity, the nuclear EMI' environment and others are discussed

20 DISTRIBUTION/AVAILABILITY OF ABSTRACT 21 ABSTRACT SECuRI Y CLASSIFICATIOND ,INCiASSIII,NEMIII, [ SAMI -S HL W11 I ,., t 1T nclassified

22a NAME OF RESPONSIBLE INDIVIDUAL 22b TELEPHONE (in(ludeArea (ode) 2.. ICE SYMG,Thomas A. Schwendtner (408) 646 2535 I. SCDD FORM 1473.84 MA R H3 AIR edition may be used, until exhausted SL fl1 Y Ct A -,i ;( A%'N C'; T.HIS P,.Ci

All other editiuns are obwleie U ncla,, fivd

i


3/75

Approved for public release; distribution is unlimited.Survivability of Meteor Burst

Communication Under AdverseOperating Conditions

byMark A. Gates

Lieutenant, United States NavyB.A., Miami University, 1985

Submitted in partial fulfillmentof the requirements for the degree of

MASTER OF SCIENCE IN TELECOMMUNICATIONS SYSTEMSMANAGEMENT

from theNAVAL POSTGRADUATE SCHOOL

March, 1992Author: ,~L~


4/75

ABSTRACT

This thesis is a study of the survivability and reliability issues associated withoperating meteor burst communication systems under adverse conditions. Meteorburst communication relies on the phenomenon of reflecting radio waves off theionized trails left by meteors as they enter the atmosphere and disintegrate. Thesystem's rapid deployment capability, mobility, and operating characteristics make

it ideal for disaster and emergency communications. Adverse conditions such asionospheric disturbances, polar region anomalies, sun spot activity, the nuclear EMPenvironment, and others are discussed.

aoession ForNTIS rFA&IDTIC TABUna8nnounce FJust I ID s ibuy --WitAvntiabI~tIy Cod,

iA


5/75

TABLE OF CONTENTS

I.INTRODUCTION......................1A. PURPOSE........................1B. STRUCTURE......................1

I.METEOR BURST OVERVIEW.................3A. INTRODUCTION....................3B. SYSTEM CHARACTERISTICS...............4

1. Operating Frequency...............92. Data Rate....................93. Transmitter Power................104. Antenna Design................105. Threshold Level................14

C. EXTERNAL NOISE...................161. Galactic Noise................162. Atmospheric Noise................163. Man-rnade(artificial) Noise..........17

D. INTERNAL SYSTEM NOISE................20E. TRANSMISSION LOSSES................20

1. Scatter Loss.................202. Free-space path loss.............22

F. ADVANTAGES/DISADVANTAGES.............221. Advantages....................22

iv


6/75

2. Disadvantages................23G. APPLICATIONS...................24

1. Long-haul communication.............242. Remote monitoring................273. Position Monitoring..............28

III. SURVIVABILITY OF METEOR BURST COMMIUNICATIONS . . 30A. INTRODUCTION...................30B. THE EFFECTS OF IONOSPHERIC DISTURBANCES . . . . 31C. THE EFFECTS OF EXTREME SOLAR ACTIVITY. ...... 34

1. Sun spots...................342. Solar flares.................35

a. Sudden Ionospheric Disturbances (SIDs) 35b. Polar Cap Absorption (PCA)........36C. Ionospheric Storms............36

D. THE EFFECTS OF POLAR REGION ANOMALIES. ...... 381. Auroral activity................382. Geomagnetic activity.............39

E. THE EFFECTS OF NUCLEAR WAR............401. Radiation....................412. Blast waves...................413. Electro-magnetic pulse (EMP).........42

F. THE EFFECTS OF PEACETIME NATURAL DISASTERS . . 43

IV. INTEROPERABILITY/RECENT RESEARCH OF METEOR BURST . 44A. INTEROPERABILITY.................44

v


7/75

1. CCITT X.25 Protocol................442. Proposed Federal Standards...........44

a. Federal Standard 1055 (FS 1055) .... 44b. Federal Standard 1056 (FS 1056) .... 45C. Federal Standard 1057 (FS 1057) .... 45

3. MIL-STD-188-135..................45a. Introduction.................45b. Required functional standards. ...... 46

B. RECENT RESEARCH ON METEOR BURST .......... 481. Antenna design ................ 502. Variable data rates .............. 503. Modulation...................52

VI. SUMMARY AND CONCLUSIONS...............53A. SUMM4ARY.......................53B. CONCLUSIONS......................54

APPENDIX A........................56

APPENDIX B..........................58

APPENDIX C........................59

LIST OF REFERENCES.....................60

BIBLIOGRAPHY.......................63

vi


8/75

INITIAL DISTRIBUTION LIST.................65

vii


9/75


10/75

LIST OF FIGURES

Figure 1. Meteor Burst Overview ..... ........... 4Figure 2. Trail densities ....... .............. 5Figure 3. Diurnal Variation ....... ............. 6Figure 4. Diurnal Cause ........ ............... 7Figure 5. Seasonal Variation ...... ............. 8Figure 6. Yagi-Uda Antenna .... .............. . 11Figure 7. Antenna Radiation .... ............. . 12Figure 8. Antenna Beam Width .... ............. . 12Figure 9. Antenna size versus gain ... .......... .. 13Figure 10. Take-off Angle .... .............. . 14Figure 11. Artificial Noise ... ............. . 18Figure 12. Loss versus Range .... ............. . 21Figure 13. Solar Features and Solar Wind ........ .. 32Figure 14. Ionospheric Layers ... ............ . 33Figure 15. Solar Flare Activity ... ........... . 36Figure 16. Auroral Zones .... ............... . 39Figure 17. Variable data rates .... ............ . 51Figure 18. Dynarate Computer Algorithm .. ........ .. 52

ix


11/75

I. INTRODUCTION

A. PURPOSEMeteor burst technology is now emerging from research anddevelopment into widespread applications throughout the world.It can benefit communication facilities in remote areas byproviding a low power, long range communication capability; itcan provide battle commanders with positioning data; it canadvance sensor/data collection methods; it can providesurvivable alternative mediums; and it can provide supportthroughout the Joint War Fighting Arena.

The intent of this thesis is to inform communicationmanagers of the capabilities and limitations of meteor burstcommunication and to provide an understanding of how variousoperating conditions affect performance. Also, the thesiswill present the advantages and disadvantages of meteor burstover other forms of communication.

B. STRUCTUREThis thesis will afford an individual with no previous

meteor burst communication experience a basic understanding ofthe phenomenon. Chapter II provides the background informationand basic technical understanding of the system. Chapter IIIdiscusses the issues of survivability of meteor burstcommunication under the various adverse operating conditions.


12/75

Chapter IV discusses interoperability and the advances inmeteor burst technology. The last chapter provides a summaryof the paper's findings and conclusions.

2


13/75

II. METEOR BURST OVERVIEW

A. INTRODUCTIONBillions of dust-sized meteors enter our atmosphere each

day. Meteor burst communication relies on the phenomenon ofreflezting radio waves off the ionized trails left by thesedust-sized meteors as they enter the atmosphere anddisintegrate [Ref 1: p. 3].

The principles of operation are as follows: a masterstation transmits a continuous, coded signal, usually in the40 to 50 MHZ band [Ref 1: p. 3]. The coded signal is reflectedoff an ionized trail to a remote receiving station [Ref 1: p.3].

The remote station decodes the signal, turns on itstransmitter and reflects a signal back along the same pathto the Master Station. Information can be sent in eitherdirection until diffusion reduces the electron density ofthe meteor's trail to a value too low to sustainreflection. [Ref 1: p. 3]

Since the typical meteor trail has a useful duration of a fewhundred milliseconds, the sensing of the meteor trail andsending of the message traffic is done in short bursts. Hencethe name meteor burst communications.

3


14/75

B. SYSTEM CHARACTERISTICSMeteor burst communications (MBC) depends on th' presence

of meteors, their ionized trails and the density of theionized trails. The meteor region occurs at altitudes of 85to 120 kilometers. Radio line of sight (LOS) up and LOS downcombine with the curvature of the Earth to limit single linkranges to approximately 2,000 km. [Ref 2: p. 4] Figure 1illustrates this geometry [Ref 2: p. 5].

93--

Figure 1. Meteor Burst OverviewWe think of meteors as being very large, but in MBC this

is not the case. MBC utilizes meteors as small as dust sizedparticles, on the order of ix10 7 grams [Ref 2: p. 7]. It hasbeen estimated that there arc approximately Ixl012 meteors of

4


15/75

varying sizes entering our atmosphere daily. Every meteor hasan ionized trail, but not every trail has the same density.A trail is classified as overdense if its electron linedensity is greater than 1 x 1014 electrons per meter orunderdense if its electron line density is less than 1 x 1014electrons per meter [Ref 2: p. 71. While MBC can use eitheroverdense or underdense trails, best communications areachieved with underdense trails(70% of meteor trails are ofthis type) [Ref 3: p. 660]. Figure 2 shows signal amplitudeversus time for each type of meteor trail [Ref 2: p. 9].

zIa

MII

~j OVDFENSE

i4 024 OEad Sxods 'rim

Figure 2. Trail densitiesWe have said that there are a great many of these meteors

entering our atmosphere daily and it would seem that this

5


16/75

would provide a constant propagation mode, but in realitythere are often short periods of time between suitable meteortrails. This time delay is referred to as wait time and canrange from milliseconds to m.Lnutes depending on sun spotactivity, system design parameters, and the availability ofacceptable meteor trails which are themselves dependent upondiurnal and seasonal variations.

Figure 3 shows the diurnal variation of the meteor rate

Diurnal Variation of Meteor Rate01AO.

IiI0

*0"S1MO O 4. 11. 16.0 20. 24.0

Local TimeFigure 3. Diurnal Variation

[Ref 2: p. 121. We see that the highest rate occurs in theearly morning hours at approximately 0600 local and the lowest

6


17/75

rate occurs in the evening hours at about 1800 local[Ref 2: p. il]. A brief pictorial explanation can be seen inFigure 4 [Ref 2: p. 12].

4 A PMfiart MOOOKAroaad son Cai

.OPMato" Snp Eby

Figure 4. Diurnal CauseFigure 5 shows the seasonal variation of the meteor rate

[Ref 4: p. 1]. We see that the lowest seasonal rate occurs inthe winter month of February, and the highest seasonal rateoccurs in the summer month of July.

The seasonal variation in the meteor rate can beattributed to two factors. First, the distribution ofsporadic meteors along the Earth's orbit is not uniform.The density is higher at those parts of the orbitcorresponding to the seasonal peak activity in June, July,and August. [Ref 2: p. 10]

7


18/75

The second factor is the declination of the Earth's axis.The 22.5 degree tilt of the Earth's polar axis, which isthe cause of the seasons in the hemispheres, alsocontributes to the seasonal variation in the meteor rates.(Ref 2: p. 10]

SEASONAL VARIATION OF METEOR RATES

poolI

em -

UU

SPU WA AMR WAY JAJUY AMG WET OCT NOV OW

Figure 5. Seasonal Variation

The wait time required to transfer a message between twostations at a specified reliability determines the systemperformance. The primary system parameters that willinfluence this wait time are operating frequency, data rate,transmitter power, antenna design, and threshold level. (Ref3: p. 666]

8


19/75

1. Operating FrequencyMeteor burst communication operates in the VHF band of

frequencies (30 to 300 MHZ), but is limited to the effectivefrequency range between 30 to 50 MHZ [Ref 2: p. 2]. The lowerlimit is determined by the desire to avoid ionospheric scatterand the effects of galactic and artificial noise which arepredominant at the lower frequencies [Ref 2: p. 15].

The upper limit is determined by receiver sensitivitylimitations, since received signal power at higher frequenciesis weaker than at lower frequencies. This is in accordancewith the relationship of frequency to signal strength whichstates that, for MBC, the amplitude of a signal isproportional to 1/f 3. [Ref 5: p. 1591] Also, for MBC, thetime duration of a signal is proportional to 1/f2 which meansthat the wait time between messages increases as frequencyincreases [Ref 2: p. 13]. Also above 50 MHZ, radio andtelevision allocations in many countries preclude meteor burstoperation [Ref 2: p. 15].

2. Data RateData rate is termed "throughput" in MBC. Due to the

intermittent nature of the medium, throughput is measured asan average value of the entire transmission process. This isnecessary because there are two distinct phases. Phase oneinvolves the transmission of data when a suitable meteor trail

9


20/75

exists; phase two involves the wait time between meteors whenno data is transmitted. [Ref 2: p. 14] This average throughputincorporates a myriad of factors to provide an importantmeasure of system performance. Average throughputs of up toseveral hundred words per minute can be achieved withrelatively simple equipment [Ref 1: p. 4].

3. Transmitter PowerTransmitter power varies from equipment to equipment

but an average value for master stations is 1 kw. The effectof transmitter power on wait time is inversely proportional:the higher the transmitter power, the shorter the wait time.[Ref 3: p. 667] Unfortunately, care must be taken to ensurethat transmitter power is not so high that it blanks out aweak incoming signal. Also, it may be possible for noisesidebands on the transmitted signal to be stronger than thereceived signal. Filters of significant size are necessary inthis type of situation. It may be better to operate at lowerpower levels so that filters can be incorporated in the samerack as the power amplifier. [Ref 2: p. 31]

4. Antenna DesignA variety of antennas are suitable for use in meteor

burst communication systems. For any given meteor burstsystem, certain antennas will have characteristics making thema better choice than others. The choice usually narrows down

10


21/75

to one or two possibilities,with the predominant typebeing Yagi-Uda. (Figure 6)[Ref 2:p. 62] The significantantenna characteristics thatshould be considered includedirectional pattern, gain,feedpoint impedance,polarization, and physicalsize. Only Yagi-Uda will beconsidered here since it isthe predominant type.

Figure 6. Yagi-Uda Antenna

The Yagi-Uda antenna is an array of dipoles arranged alonga central supporting boom. One dipole is fed with powerwhile the others are excited by mutual coupling. When thelengths and spacing are properly chosen, the radiationpattern of a Yagi will be essentially unidirectional,beaming radiated power in one preferred direction. [Ref2:D. 62-63]Figures 7 and 8 illustrate this point [Ref 2: p. 61] [Ref 8:p. 69].

The gain depends on the number of elements in the array.Meteor burst Yagis may have anywhere from 3 to 10 elementsproducing gains on the order of 7 to 15 db respectively.As more elements are used, the physical length of the boomincreases, often imposing practical mechanical or spacelimitations on the obtainable gain. [Ref 2: p. 63]11


22/75

xFigure 7. Antenna Radiation

8EAFMWIOfl4 Cp TRANSMITTING ANTrENNA SIAMIoTH OF RtECEIVIN4GAIENA

RECEIVING STATIONTRAN4SMITTING STATION

Figure 8. Antenna Beam Width

12


23/75

Figure 9 shows the relationship between the number ofelements, length in wavelengths, and the obtainable gain of

Surnber of elementsYagi-Uda Parameters

, 3. P.16.00

4,0 1.0

2.0 4.0 6. 0 ,0.0 12.0Figure 9. Antenna size versus gain

the antenna [Ref 2: p. 64].Yagis are usually mounted with the plane ofthe antenna parallel to the surface of theearth, which results in horizontalpolarization. However, the antenna can berotated 900 in the elevation angle directionfor vertical polarization. [Ref 2: p. 64]Figure 10 shows optimum take-off angle for the Yagi

antenna [Ref 2: p. 66], while Table I provides a summary ofthe various antenna types and their uses [Ref 2: p. 70).

13


24/75

5. Threshold LevelThreshold is a function of the type of modulation

0 80-

60

S4030-0 2010--1

E.- 0 I ] I I I0 400 00 1200 1600 2000

Distance - knFigure 10. Take-off Angle

used, bandwidth, and the receiver noise. Meteor burst systemsgenerally employ forms of PSK modulation. The primaryadvantage of PSK is a theoretical 3 db signal-to-noise ratioadvantage over conventional FSK [Ref 3: p. 6651. This can bevery significant in meteor burst where there is always a

battle to obtain usable data from marginal threshold-levelsignals. Bit error rates (BER) of 3x104 or better are

14


25/75

Table I. ANTENNA SUMMARY

ANTENNA SUMMARY TABLE" Use horizontally mounted (and polarized) Yagi antennasunless there are specific reasons for doing otherwise." For communication ranges less than 500 km , the possibilityof tilting Yagi antennas for better high-angle radiationshould be considered." For very short ranges an omnidirectional, horizontallypolarized antenna mounted close to the ground to enhancehigh-angle radiation would be a first choice.* If omnidirectional coverage is needed, a vertical dipole orground plane antenna for vertical polarization or aturnstile antenna of full-wave loop for horizontalpolarization should be used." For mobile use, the horizontally polarized halo or thevertically polarized vertical whip antenna are the obviouschoices.

" If the central station in a network uses verticalpolarization, all stations should use vertical polarization.If outlying stations communicate in only one geographicdirection, system performance can be enhanced if they usedirective beam antennas, such as Yagi.

15


26/75

normally desired [Ref 6: p. 2]. The lower the threshold level,the lower the wait time, and the greater the performance [Ref3: p. 667-669].C. EXTERNAL NOISE

1. Galactic NoiseGalactic noise is a function of frequency and can be

calculated from the following formula [Ref 2: p. 411:Ng(dbm) = -124.5 - 22*log(fmHz) + 10*log(Bz)

where f is the frequency in Mhz and B is the bandwidth in Hz.This value is then compared with other noise power levels andthe desired signal level to evaluate the system design. In alocation free of artificial noise, galactic noise may be largeenough to be the limiting factor in meteor burst reception.[Ref 2: p. 41-42]

2. Atmospheric NoiseAtmospheric noise levels fall off very rapidly with

increasing frequency and will not generally be significantabove 30 MHZ and therefore will not enter into the link budget[Ref 3: p. 596]. If lower frequencies around 20 MHZ weredesired for meteor burst then atmospheric noise might becomea factor and would have to be taken into account.

16


27/75

3. Man-made(artificial) NoiseArtificial noise is the dominant noise source in

meteor burst communication. This noise is a function oflocation and frequency which can be determined by thefollowing formulas and are illustrated in Figure 11:

Business NB(dbm) = -97.2 - 27.7*log(fm z )+ 10*log (BH)

Residential : Ns(dbm) = -101.5 - 27.7*log(fmH )+ 10*log(BH)

Rural: NR(dbm) = -106.8 - 27.7*log(fmz)+ 10*log(BHZ) [Ref 2: P. 40]

It should be noted that these are median values usedfor the link budget, and considerat'>J. should be given to thevariation of the noise lex,-is about their median values whenconducting in-depth cnalysic. If favorable results areobtained from the use of the median values, recalculation withmore liberal noise estimates incorporating the variabilityshould be made. [Ref 2: p. 45]

This variation is a measure of how much thenoise level can be expected to deviate fromthe median value within any one-hour period.There is also a location variability which isa measure of how much the median noise levelcan be expected to vary from location tolocation within the same noise category. [Ref2: p. 44]

17


28/75

Galactic, atmospheric, and man-made noise are allforms of broadband noise. Another external factor whichshould be taken into account when evaluating system design is

.90-10 0 --------------------..... -- - - ------ -- -- - -

- - - Noise Power in a 1 Hz Bandwidth _-------

E -140 ----------------------------0 -1 0 .... .... .....--. ... .....--. . . ....-. . ..-- - - -----

0 -6

1kTB --74-dBm ..--- ---

10 20 40 60 80 100FREQUENCY - MHz

Figure 11. Artificial Noiseinterference. Interference is a form of nL.rrow band noisewhich comes from electronic devices operating in the samefrequency range as the meteor burst system [Ref 2: p. 46].There are four main causes of interference; the first is low-power communication devices such as cordless phones, childmonitors, alarm systems, walkie-talkies, and remote controltoys [Ref 2: p. 461.

18


29/75

The second source of noise is from two-way mobile radios.Even if there are no mobile radios with the same frequency inthe immediate area of a meteor burst site, the RF ground waveof the mobile radio's signal may interfere at the meteor burstsite [Ref 2: p. 47].

The third source of noise involves the second harmonic ofan HF transmitter operating between 15 to 25 MHZ and the thirdharmonic of an HF transmitter operating between 10 to 16.67MHZ. The nature of harmonic interference can be highlyintermittent. [Ref 2: p. 48]

The fourth and final source of noise involves the use ofpersonal computers (PCs). Pcs constitute one of the singlemost predominant contributors to man-made noise. PCs are sonoisy that the FCC must regulate their noise output. [Ref 2:p. 48] Class A devices which operate in the 30 to 88 MHZ rangecan radiate interference levels up to 3000 microvolts permeter at a distance of 3 meters. [Ref 2: p. 48] This is highlysignificant when compared with the fact that usable burstsignals are often at a level of less than 1 microvolt at thereceiver. [Ref 2: p. 48] Based on field strength theory, thismeans that a class A device can produce a 1 microvolt permeter level of interference to a meteor burst receiver site ata listance of 9 km from the PC creating the interference! [Ref2: p. 49-50]

19


30/75

D. INTERNAL SYSTEM NOISEEquivalent input noise power is the value of input noise

power that would produce the same receiver output noise poweras the actual receiver in an ideal, noiseless receiver. Theusefulness of equivalent input noise power of the receiver isthat it can be directly compared to the levels of input noisepower due to external sources and the input signal power. Thegoal, of course, is that the input signal power be greaterthan the largest of the various input noise power levels by anadequate margin. The equivalent input noise power for anideal noiseless receiver with a 1 Hz bandwidth can bedetermined by:

Ni=k*To*B,where k= Boltzman's constant, T, = 290 k, and B= bandwidth inHz. [Ref 2: p. 51-53]

E. TRANSMISSION LOSSESThe last section that needs to be addressed is signal

transmission loss, the sum of scatter loss and free-space pathloss(FSPL). Figure 12 shows transmission loss versus range[Ref 3: p. 675].

1. Scatter LossScatter loss is also referred to as additional path

loss, and is the result of reflecting the signal off the

20


31/75

meteor trail. It involves several factors, but for ourpurposes, the details of reflection mechanisms are notimportant. To know that a reflection takes place and to beable to calculate the loss that the signal incurs in theprocess is sufficient. For a detailed analysis of this lossfactor see Telecommunications Transmission Handbook, Chapter9, by Freeman [Ref 3].

ills15r- --lOSS

2g0 401 $i0 lo0 1ogo 12O0 141901 1 0l 20log

Figure 12. Loss versus RangeA highly condensed summary yields the following

values: 51.4 db (average), 31.4 db (minimum) and 57.0 db(maximum) [Ref 2: p. 131]. These values assume a midpointreflection from an underdense meteor trail and they also do

21

1 5 5-- -II-- -


32/75

not take the time varying aspects of reflection into account.By adding the maximum value to the free-space path loss for afrequency of 40 MHZ gives the curve for trails at right anglesto the plane of propagation as seen in Figure 12 [Ref 3: p.675].

2. Free-space path lossThis is the signal loss associated with the signal's

propagation through the atmosphere and is based on frequencyand distance. It is given by the following formula:LP= 32.45 + 20*log(fmz) + 20*log(dk) [Ref 3: p. 210-211]F. ADVANTAGES/DISADVANTAGES

1. Advantages.

" Signal path between transmitter and receiver is highlydirectional providing a small footprint. A smallfootprint decreases probability of intercept andunintentional interference and increases the jammingmargin. [Ref 7: p. 125]* Conservation of frequency spectrum is achieved sincefootprints of various users rarely overlap in space ortime. This allows for multiple access via spatial andtemporal diversity. [Ref 7: p. 125]* Hardware requires smaller antennas and less complexequipment than traditional HF and is therefore reasonablein cost. Off-the-shelf VHF equipment can be used andhighly directional antennas are unnecessary. [Ref 7: p.132-134]

22


33/75

" Highly skilled operators are not needed and unmannedstations can readily be arranged for automatic operationin relay nets thus further reducing the cost of a system.[Ref 2: p. 4]* High power is neither necessary nor economic--station

equipment can be compact, mobile, and cost effective. [Ref2: P. 29-37]" Intrinsic degree of randomness makes MBC highly suitablefor non-real time communications. [Ref 7: P. 126]" Meteoric burst phenomena are fairly well understood andcan be considered a consistently present act of nature.The medium is reasonably predictable and thereforeconsidered stable. [Ref 8: P. 62]" A meteor burst communication system transmits for only afraction of a second. Because of that, it would be very

difficult for an enemy to determine a transmitter locationusing direction finding techniques. [Ref 7: P. 126]* The nuclear survivability of the meteor burst medium issuperior to other media. Meteors will continue to enterour atmosphere regardless of nuclear blasts and they willproduce usable trails. Additionally, because thetransmit/receive equipment is small and requires onlymodest amounts of power, the equipment can be installed inhardened shelters easily. [Ref 2: p. 17-19]2. Disadvantages

" Low data rate is unsuitable for voice communications, andthe intrinsic degree of randomness associated with themeteor trails makes MBC unsuitable for real timecommunications at this time. [Ref 2: p. 4]" Reliance on meteors which are by nature sporadically timedand have trails of inconsistent density lends an elementof uncertainty to meteor burst communications. Wait timeis the most affected factor. [Ref 2: p. 4]" MBC are sensitive to sun spots and, during increased solaractivity, reliability may go down and wait time may go up.[Ref 9: p. 16]

23


34/75

G. APPLICATIONSMeteor burst communications is gaining acceptance

worldwide as a viable means of data transmission. There arethree general categories of application: long-haulcommunication, remote monitoring, and position monitoring.

1. Long-haul communicationThere are three modes of operation for data

communications: point-to-point, network, and broadcast. Todate most meteor burst systems have been designed for point-to-point applications. Point-to-point communication is astraightforward application. The only requisite for effectivesystem control is the ability of the transmitting terminal todetermine the beginning and end of a useful burst. If atransmission begins too late or ends too soon burst time willbe wasted. If the transmission extends past the usefulportion of the burst, a high error rate will result. Also inpoint-to-point, a feedback path is available. [Ref 5: P. 1593]

A network system is formed by connecting multiplemaster stations and remote stations together. One suchnetwork is the Western Union hardware currently installed forthe Department of Agriculture. This system consists of 511remote sites that communicate with two master stations.Another network system is the NORAD-SAC network that runs fromFlorida to Alaska. The network provides full duplex

24


35/75

communications with multiple point-to-point links of theNORAD-SAC network between various sites. Table II explainsthe modes of operation [Ref 2: p. 18] . It consists of eightmaster stations and 23 remote stations [Ref 10: P. 2].Broadcast systems have received very little attentionso far. For this method the broadcast transmitter must repeatthe information enough times to ensure a high probability ofreception by the remote stations. The simplest means ofeffecting a broadcast is to repeatedly transmit the messagesthat are brief enough to occupy a single burst of moderateduration. Each repetition of the message must be preceded bya preamble that will enable the remote terminal enough time toachieve synchronization. [Ref 5: P. 1593]

Some examples of systems currently in use are:1) The Alaskan Air Command System uses thirteen 10 kwcollocated terminals to provide a cost-effective backup to theprimary satellite link that sends radar data to a regionaloperations center. The system also provides one-waysynthesized voice communication to airborne interceptors. [Ref2: p. 24]2) The Chinese Communication Network is a system that providescommunication from remote army camps to three different masterstations. This system serves as the main communication linkfor low-priority record traffic. It employs 1 kw master

25


36/75

Table II. OPERATIONAL MODES

OPFRATING MODES

FULL DUPLEXSimultaneous transmit and receive on two separate frequencies.

HALF DUPLEXAlternate transmit and receive on a two separate frequencies.

SIMPLEXAlternate transmit and receive on a single frequency.

FULL DUPLEX RELAYSimultaneous transmit and receive with station A and store data.Then. simultaneous transmit and receive with station B to forwardstored data.

BROADCASTMaster continuously transmits o* a single frequency. Remotes con-tinuously listen on same freq~eacy.

MASTER_ REMOTE

Communications is with one remote at a time. Remote unit is half-duprex./] MASTER

/ // / FORWARD STORE/ /

I MASTER OR MASTER ORREMOTE "B"R


37/75

stations and 300 W remote stations. [Ref 2: p. 24]

3) The Alaskan Meteor Burst Communication System is a civilcommunication system operated for the joint use by theNational Weather Service, Corps of Engineers, and SoilConservation Service(SCS). The system provides for bothcommunication assets and remote data acquisition. [Ref 2: p.24]

2. Remote MonitoringMeteor burst is capable of employing various sensors

at a remote station to monitor and collect environmental data.This data can then be stored for delayed transmission, ifnecessary, or dirp . transmitted back to a centrally locatedmaster station w.ch will process the information. [Ref 2: p.25]

Remote monitoring may be used for a variety ofreasons, the most common of which is water management. TheSoil Conservation Service's snowpack telemetry (SNOTEL) systemmakes use of this monitoring to aid in forecasting spring andsummer water runoff, stream flows, etc. [Ref 2: p. 25] Thesystem is capable of the following:" Snowpack monitoring* River level and rainfall monitoring

27


38/75

* Acid rain studies* Air and water pollution monitoring* Monitoring chlorine in water systems* River quality monitoring

Other reasons for remote monitoring include threatwarning [Ref 7: p. 131], pipeline management [Ref 11: p. 1-1],lighthouse monitoring [Ref 2: p. 25], alarm sensing [Ref 7: p.1321, and remote equipment activation [Ref 7: p. 132].

3. Position MonitoringThis is one of the newest applications of meteor burst

technology. The incorporation of a LORAN C navigation receiverand antenna into the meteor burst system provides for thetracking and up-to-the-minute positioning(accurate to within500m) of long haul trucks, ships, and aircraft. [Ref 2: p. 26]

Two vehicle tracking systems that are currently in useare the LOAD-TRAK and the TRANS-TRAK systems being tested byNorth American Van Lines. [Ref 2: p. 26] Besides providingpositioning data, the systems can also supply two-way messageand facsimile transmission capability. [Ref 2: p. 27] Thisallows the parent company to efficiently inform drivers ofupdated itineraries and load changes.

The Navy is experimenting with position monitoring onvarious ship and aircraft platforms. It is even evaluating

28


39/75

meteor burst's potential for the tracking of buoys andicebergs [Ref 2: p. 25-27].

29


40/75

III. SURVIVABILITY OF METEOR BURST COMMUNICATIONS

A. INTRODUCTIONSurvivability is one of the most importanL factors in the

design of military communication systems. Meteor burstcommunications systems are no exception. The issue ofsurvivability involves both physical and functionalsurvivability. Physical survivability, on one hand, veryrarely provides sufficient protection to each element of asystem to render the system survivable.

Functional survivability, on the other hand, addresses theset of sufficiently redundant subsystems so that the abilityto communicate exists under adverse conditions. Thus, adequatesurvivability almost always demands a total systems approachregardless of the threat level. [Ref 12: p. 1441]

There are five sub-components of functional survivability:0 INTEROPERABILITY- the ability of systems, units, or forcesto provide services to and accept services from othersystems, units, of forces and to use the services soexchanged to operate effectively together. [Ref 13: p. 190]

* RELIABILITY- the ability of an item to perform a requiredfunction under stated conditions for a specified period oftime. [Ref 13: p. 309]

30


41/75

" FLEXIBILITY- the ability to adapt to quickly changingenvironments and a wide range of operations.

* COMPATIBILITY- the capability of two or more items orcomponents of equipment or material to exist or functionin the same system or environment without mutualinterference. [Ref 13: p. 82]

* RESPONSIVENESS- the ability to respond in an accurate andtimely manner.This chapter will illustrate the many aspects of

survivability associated with the long-haul communicationsaspect of meteor burst communications as they pertain tocertain adverse conditions. Interoperability will be discussedin Chapter IV. It should be noted that high frequency (HF)radio will be used as a comparative backdrop throughout thechapter.

B. THE EFFECTS OF IONOSPHERIC DISTURBANCESOn any given day, both the physical and functional aspects

of survivability are tested under varying conditions. InChapter II, some of the physical and functional aspects ofsurvivability were already discussed. This sub-section willfocus on the influence of solar activity on the communicationmediums themselves.

31


42/75

Figure 13 [Ref 15: p. 2583 depicts the solar features andthe solar wind which affect communications. The sun is themajor cause of variations in the propagation characteristicsof the ionosphere, which vary with time of day. [Ref 16: p. 1]During daylight hours, ultraviolet and x-rays of the sunionize the Earth's atmosphere causing the formation of the D,E, and F1 layers of the ionosphere. Figure 14 illustrates thealtitudes of these layers versus electron density. [Ref 17: p.5]

Th e Su n During prolon flaresprotons Spiralalong field linesLocations 2-of source 2 3*as Sun rotates The solar wind SMagnetic: feld line

in Wral.. r- "-. \Solar wind

" Inner Corona 2 Minimum vo"/ \ Protons from flares of \ Typical ve;ocity

10000 key. enerpy 4OD-50Okras"iiFlare velocity =4 X 10"kn " Maximum velocity11 1000 km s'ilament \ 100kmS-/ \( 9 Particle density

n/Itra Locations from Source Temperature 10'

-. $ p .. " ' I71\ Sunspots/

Sources of the solar windV Polar coronal hole /

Pion inenc The EarthThe SunFigure 13. Solar Features and Solar Wind

According to Wells in ProceedingsNaval Review 1982, "Dueto the sun-shifting of the ionospheric layers in the upper

32


43/75

atmosphere, HF f:equencies must be adjusted every few hours toachieve satisfactory communications." This is especially truearound the hours of sunrise and sunset [Ref 16: p. 1].

300- F2U y DAYTIME

1 E 200-/--

Es-- E EUVX-RAYS SOURCESOF100_- __IONIZATIOND Ly a, X-RAYS

C COSMIC RAYS

1010 1011 1012ELECTRON DENSITY (m 3Figure 14. Ionospheric Layers

The MBC transmission path is unaffected by ionosphericdisturbances which occur in the HF band for two reasons.First, MBC uses the ionization from meteor trails and not theionized layers of the atmosphere. Therefore, temporalvariations in layer heights do not impede the meteor burstpropagation medium.

Second, adaptive data rate techniques may be used toadjust to the changing conditions. [Ref 14: p. 173]

33


44/75

In HF applications, transmissions are repeated, andfrequencies are changed until a proper frequency channelis found. [Ref 14: p. 173]Meteor burst communication, on the other hand, may use atechnique called Dynarate to maintain performance and systemreliability [Ref 14: p. 173].

Using a process called Dynarate, Meteor CommunicationsCorporation(MCC) has increased throughput bydynamically varying the radio frequency(RF) data rateas a function of received signal strength. Thisprocess adapts to whatever condition is present at anytime. Small signals are used at low data rates, thusminimizing wait times for short, high precedencemessages while large signals are used at high datarates to maximize throughput.[Ref 14: p. 173-178]

C. THE EFFECTS OF EXTREME SOLAR ACTIVITYIn the last section, the effects of "day-to-day" normal

solar activity were discussed. This section will focus on theeffects of extreme solar activity on communications systems.This activity comes in two forms: sun spots and solar flares.

1. Sun spotsA sun spot may be defined as:

A relatively dark region on the disk of the sun(photosphere), with an inner "umbra" of effectiveradiation temperature about 4500 K and an outer "penumbra"of somewhat higher temperature. [Ref 18: p. 274]They appear as vortex-like disturbances moving across

the face of the sun and are associated with the production of

34


45/75

large magnetic fields which have a direct impact on theionosphere. [Ref 18: p. 274]

Sun spot activity reaches a maxima approximately everyeleven years; overall sun spot activity is measured by theWolf sunspot number [Ref 3: p. 134]. Since sun spot cycles arerelatively predictable, degradation of communications can beexpected at these times.

2. Solar flaresA solar flare may be defined as:An abrupt and totally unpredictable increasein the intensity of the electro-magneticemissions near a sunspot region. It is seen asan increased area of brightness on the sun'schromosphere.[Ref 19: p. 1767]Three different types of ionospheric disturbances

result from solar flares: sudden ionospheric disturbances(SIDS), polar cap absorption (PCA), and ionospheric storms.These are illustrated in Figure 15 [Ref 17: p. 34].

a. Sudden Ionospheric Disturbances (SIDs)SIDs occur almost immediately (within minutes)after the occurrence of a flare due to arrivalof electromagnetic radiation, primarily in theform of x-rays. They affect the entiredaylight portion of the earth and last as longas the flares.[Ref 17: p. 34-35]

35


46/75

b. Polaz Cap Absozption (PCA)Around fifteen minutes after a flare, cosmicray particles such as protons arrive at theEarth and continue from one to ten days, butnormally last about three days. Completecommunication blackouts can occur with notransmissions possible through the auroralregions (blackouts can occur elsewhere aswell). PCAs normally last for around a day.Their occurrences are rare with only aboutseven or eight per year during sunspotmaximum, and even fewer otherwise.[Ref 17: p.34-35]

0"Ii.

Ram.,OnI. CloudSId-lays Prolos

AbO ke .i - 3 ovs 24 - 48 ewI if If_ _SID PCA StCmsFigure 15. Solar Flare Activity

c. Ionospheric StormsThe last arrivals from the flare are theplasma clouds. These clouds impinge upon theionosphere creating "storms" with waves ofincreasing and decreasing electron density.They last for about 2-5 days and, as with the

36


47/75

other events, they enhance the D and Fregions, increasing absorption. [Ref 17: p.35]The most observable effect of the ionospheric storms

is the narrowing, or total elimination, of the available HFtransmission frequencies as a result of the increased D layerabsorption. This creates a lowering of the maximum useablefrequency (MUF) and the simultaneous raising of the lowestuseable frequency (LUF).[Ref 17: p. 35]

The effects on meteor burst are different from thoseon the HF spectrum. At the onset of solar activity, receiversdetect increased noise levels just as HF does. The differencecomes during the PCA and ionospheric storms. MBC performanceis usually affected three days after solar activity beginswhich coincides with the time frame of the ionospheric storm'seffects [Ref 20: p. 10] . While HF is severely, if not totally,disrupted, meteor burst still continues to operate but at aslower rate [Ref 20: p.10-11].

During the March 1989 solar activity, the SNOTELsystem in the western United States observed an increase inaverage system response time and three days later, a slightdecrease in systemwide performance, from 90% down to around78% [Ref 20: p. 11].

37


48/75

D. THE EFFECTS OF POLAR REGION ANOMALIESThe polar regions have long since been a great hinderance

to commu. ations. Besides the disturbances caused by thesevere weather patterns, strong magnetic fields and disruptedzones of the ionosphere caused by auroral activity createhavoc throughout the traditional communications spectrum (HF).

1. Auroral activityAurora activity may be defined as:

A luminous phenomenon caused by electrical discharges inthe atmosphere; probably confined to the tenuous air ofhigh altitudes. It is most commonly seen in sub-arctic andsub-antarctic latitudes and is called aurora borialis oraurora austrailis respectively, according to thehemisphere in which it occurs. [Ref 20: p. G-2]

The extent of the aurora zones can be seen in Figure6 [Ref 15: p. 254]. It should be noted that during times of

extreme solar activity, auroral zones can be extended greatly.Auroras have been known to occur as far south as Florida.

The aurora can blot out HF radio communications inmuch the same manner as solar activity does, but on the otherhand, it can also be used to increase the transmission pathfor VHF radio [Ref 15: p. 260]. Meteor burst transmits in theVHF range, which normally involves a line of sight (LOS)propagation path. However, when a VHF signal encounters thelarge number of electrical particles in the magnetic fields of

38


49/75

(a) W~ "',woob P~'U

USR

- \

Figre 16. Auroral Zones

the aurora, ionospheric scattering occurs. This allows forline of sight (LOS) ranges to be extended beyond the normalradio horizon. [Ref 16: p. 201

2. Gemagnetic activityIn addition to the auroral activity, geomgnetic

activity is also the result of solar activity on the polarregions. Geomagnetic activity is an increase of electricalground potential as a result of electron bombardment, drivenby the solar winds, on the Earth's magnetic fields.

39


50/75

Ground potentials can induce loads in electricaltransmission lines and currents in long distance conduits suchas the Alaskan oil pipeline (Ref 15: p. 260] . These potentialscan cause widespread power losses as a result of excessiveelectrical currents being injected into power lines. Thisoccurred in Canada in March of 1989, and in New York in 1969and 1972 [Ref 15: p. 260].E. THE EFFECTS OF NUCLEAR WAR

A nuclear detonation can disrupt the ionosphere for hoursor days, and interrupt long range HF radio communications.[Ref 8: p. 62] Certain high-priority communications are neededimmediately following nuclear attack. These include:

" Maintenance of the strategic retaliatory capability of theUnited States.[Ref 8: p. 611" Control of continuing military operations both within andoutside of the continental United States. [Ref 8: p. 61]* Continuation of diplomatic relations with allies andneutrals plus possible negotiations with the enemy. [Ref 8:p. 61]* Actions to ensure the continuity of federal, state, andlocal governments. [Ref 8: p. 61]* Provision of civil defense, including the collection anddisseminating of radioactive fallout data. [Ref 8: p. 61]* Coordination of relief operations.[Ref 8: p. 61]

40


51/75

These objectives are not likely to be realized followinga nuclear attack if reliance is placed on radio links makinguse of the ionosphere; i.e., high frequency (HF) [Ref 8: p.61]. Meteor burst communication uses an alternative medium andis expected to continue to provide the needed connectivity.

1. RadiationNuclear radiation is primarily a physical hazard to

personnel rather than equipment, but contaminated equipmentcannot be used. Meteor burst systems are fully automated, andcan be deployed rapidly. The use of remote keying and a three-day message storage capacity [Ref 20: p. 7] eliminate the needfor exposing personnel to the harmful radiation.

2. Blast wavesBlast waves from a nuclear detonation threatens the

physical survivability of equipment. A blast wave may bedefined as:A pulse of air, propagated from an explosion, in which thepressure increases sharply at the front of a moving airmass, accompanied by strong, transient winds and thermalradiation. [Ref 22: p. 6]

While traditional HF antennas must be exposed tothese waves, and are therefore susceptible to destruction [Ref23: p. 55], meteor burst antennas can be made blast resistant.This is achieved by the use of buried antennas.

The term "buried" is misleading, because typically buriedantennas are not covered with earth, as the name implies.

41


52/75

Although located below the surface, they are exposed tothe extent that they can "see" the sky area that they mustilluminate. A radome, transparent to the frequenciesemployed, may be used to afford protection while notinterfering with operation. [Ref 2: p. 68]3. Electro-magnetic pulse (EMP)The greatest threat to communications from nuclear war

comes from the electro-magnetic energy pulse that isdischarged from a nuclear explosion.

After detonation, large portions of the ionospheren-y,_ie totally destroyed or severely damaged. It is thisionospheric disruption which interrupts high frequency (HF)communications relying on the ionosphere. [Ref 8: p. 62]

Meteor burst communication, on the other hand, doesnot rely on the use of the ionosphere, but rather utilizes thetemporary ionization produced by meteor trails. While theionosphere may be destroyed, meteors trails will continue toprovide sufficient ionization for communication via meteorburst. Therefore, " MBC recovers from the atmospheric nuclearevents more quickly than high frequency (HF). MBC involveshigher frequencies (VHF) that, not affected by ionosphericdisturbances, will be considerably less attenuated." [Ref 24:p. 56]

Another aspect of survivability is the process ofradiation hardening which "improves the ability of a device,

42


53/75

piece of equipment, or transmission link to withstand nuclearor other harmful radiation [Ref 19: p. 1549]."F. THE EFFECTS OF PEACETIME NATURAL DISASTERS

Emergency situations require that survivablecommunications be provided and that connectivity with bothcivil and government authorities be maintained.

Natural disasters such as flood, fire, and earthquake eachpresent their own special difficulties when it comes toestablishing and maintaining a communications link.

Guided media communications such as telephone, cable, andcomputer data networks, may be disabled as a result of severedpower or data lines, destroyed transmission facilities, orincapacitated personnel.

Unguided media communications such as radio prove moreuseful. Meteor burst communication equipment is designed tooperate under extreme environmental conditions. Portablesystems can be set up quickly, powered by solar cells and,when combined with LORAN C, provide position monitoring [Ref2: p. 29-35].

43


54/75

IV. INTEROPERABILITY/RECENT RESEARCH OF METEOR FURST

A. INTEROPERABILITYThis section is intended to provide a basic unrvisLanding

of the parameters required to achieve interoperability ofmeteor burst communication equipment with other communicationsystems and equipment.

1. CCITT X.25 ProtocolThe Comit6 Consultatif International de T6lphone et

T6 l6graph(CCITT) X series is concerned with data communicationnetworks, specifically the services, facilities and interfacesthat relate to wire communications [Ref 3: p. 627-630].

Because the meteor burst transmission path differssignificantly from the continuous paths typical of land-lineor satellite communications, and each equipment manufacturerhas its own special requirements, changes are needed to theX.25 protocol for it to incorporate meteor burstcommunication. [Ref 2: p. 101]

2. Proposed Federal Standardsa. Federal Standard 1055 (FS 1055)

FS 1055, "Telecommunications: InteroperabilityRequirements for Meteor Burst Radio Communications BetweenConventional Master And Remote Stations," facilitates

44


55/75

interoperability between Federal Government Meteor BurstCommunication (MBC) master and remote stations used in radiotelecommunications applications [Ref 25: p. 1].

b. Federal Standard 1056 (FS 1056)FS 1056, "Telecommunications: Interoperability

Requirements For The Encryption Of Meteor Burst RadioCommunications," facilitates interoperability between meteorburst radio communication facilities and systems of theFederal Government [Ref 26: p. 1].

c. Federal Standard 1057 (FS 1057)FS 1057, "Telecommunications: Interoperability

Requirements For Meteor Burst Radio Communications BetweenNetworks By Conventional Master Stations," facilitatesinteroperability between Federal Government Meteor BurstCommunication (MBC) internetwork gateway master stations usedin radio telecommunication applications [Ref 27: p. 11.

3. MIL-STD-188-135a. Introduction

This document, "Interoperability and PerformanceStandards For Meteor Burst Communications, InitialCapability," provides initial capability standards fortactical and long-haul equipment associated exclusively withmeteor burst communications [Ref 6: p. 1].

45


56/75

b. Required functional standardsAccording to section 4.2 of the document, "The

fulfillment of nine general functions shall be required toachieve MBC system interoperability." Each of these areoutlined below and shown in Table 1II [Ref 6: p. 7] as theyrelate to their respective equipment components.

" ANTENNA POLARIZATION. The transmitted signal shall belinearly polarized. A horizontally oriented E-field shouldbe used. Most efficient transmission is obtained by use ofhorizontal polarization. However, where there are specialconstraints vertical polarization may be used, at someloss of efficiency. Note that the polarization used at anyparticular terminal must be the same as that of theterminal with which the terminal is to communicate. [Ref6: p. 8]

" OPERATING RADIO FREQUENCY. The equipment shall have anoperating frequency range of 30.000 Mhz to 88.000 Mhz or30.000 Mhz to 54.000 MHz. The preferred frequency range is30.000 MHz to 54.000 MHz. [Ref 6: p. 8]" MODULATION. Differentially Encoded Binary Phase ShiftKeying (DEBPSK), with phase deviations of +90 and -90, andnonreturn-to-zero (NRZ) keying shall be the requiredmodulation. Coherent detection shall be provided at thereceiver. [Ref 6: p. 8-91

" BIT PROCESSING. The equipment shall be capable ofoperating at 2, 4, and 8 kbps for communication systemsand at 8 kbps for remote sensing systems. Synchronizationwill be achieved using link protocols. [Ref 6: p. 9]" ERROR CONTROL. Communication systems shall incorporate"Go-Back-N" Automatic Repeat Recrest (ARQ) technique,where all retransmissions are sent in succession. Thesystem shall operate using a negative acknowledgement

(NAK) scheme and ANSI 16 Cyclic Redundancy Check (CRC)code for error detection. [Ref 6: p. 9]

46


57/75

Table III. GENERAL FUNCTIONS

c:C

........ ..c

47


58/75

" LINK PROTOCOLS. The common mode link protocol shallsupport communications and remote sensing systems,accommodate a multinode network, and operate in half-duplex, full-duplex, broadcast, and polling modes. Theequipment shall have the capability to handle three typesof messages: point-to-point which contain no routinginformation, network messages which contain routinginformation, and broadcast messages which are messagessent from the master intended for a number of recipientsbut with no acknowledgement. [Ref 6: p. 10]* NETWORK PROTOCOLS. The network protocols are designed tosupport the transmission of messages within a single starnetwork (one master serving up to 254 remotes) or a linkedstar network (using master-to-master trunking). [Ref 6: p.311* COMSEC. Communications systems shall incorporate COMSEC to

provide end-to-end encryption. This does not apply toremote sensing systems. The COMSEC device shall encryptthe entire message before transmission. [Ref 6: p. 34]* INPUT/OUTPUT INTERFACES. Communications interface portsshall be provided on MBC terminals to support two-waymessage traffic between the MBC terminal and the KeyboardSend/Receive (KSR) terminal of host processors. The datarates at the interface shall be 300 and 1200 baud usingthe ASCII seven bit character plus one parity bit. [Ref 6:p. 36] Table IV illustrates the input/outputconfiguration. [Ref 6: p. 38]

B. RECENT RESEARCH ON METEOR BURSTAs we have seen from Chapter II, meteor burst

communication has limitations concerning throughput and noise.This chapter will discuss some of the efforts currently beingstudied to eliminate these limitations. Research is beingconducted in the areas of antenna design, variable data rates,and new modulation schemes.

48


59/75

Table IV. INPUT/OUTPUT CONFIGURATIONS

II,IIfWW3 .

,II

" II


60/75

1. Antenna designThe design enhancement of antennas for meteor burst

communications is one of the most significant factors inimproving the link margin. Not only can throughput beincreased, but man-made noise can also be reduced at the sametime by using "smart" antennas, currently being tested. [Ref28)

"Smart" antennas will provide null steering towardsareas of high noise to reduce the man-made noise level whilestill maintaining the desired directivity and trackingcapability of a desired meteor trail. [Ref 28] A region ofhigh concentration of meteors in the atmosphere is called a"hot spot". In these areas there will be a greater number ofmeteor trails to utilize which allows burst transmission ratesto approach a state of near-continuous data transmission. [Ref28]

2. Variable data ratesVariable data rates involves the sending of data at

higher rates when the received signal strength is strong andslowing the data rate as the signal strength decreases toincrease throughput efficiency [Ref 14: p. 177].

Meteor Communications Corporation (MCC) developed atechnique called "DYNARATE" in the 1980s to improve throughputvia variable data rates [Ref 14: p. 173].

50


61/75

Figure 17 [Ref 14: p. 177] shows the results of thistechnique on a large, underdense meteor signal while Figure 18[Ref 14: p. 178] presents the relationship between availablesignal-to-noise ratio and transmission data rate.

96 dlm

DETECTE

-116 On

2394 32 leRAF

et- b/, k/ k2"-b/'RATE14

Figure 17. Variable data ratesCurrently MCC is working on modifications to this technique toenhance throughput capability for purposes such as thecontinuous transmission of linear encoded voice signals, whichup to now have been a major limitation of meteor burstcommnunication. [Ref 28]

51


62/75

3. ModulationMCC is also working on methods of increasing

throughput by the use of advanced modulation schemes which

418 aAction>18 Increase data rate 4X16- 18 Increase data rate 2X13-15 No change10-12 Decrease data rate by 1/2


63/75

VI. SUMMARY AND CONCLUSIONS

A. SUMMARYChapter II began with an overview of meteor burst

communication, including the operating characteristics,noise factors, and transmission losses affecting this uniquecommunication link. Next it presented the advantages anddisadvantages of meteor burst communication; the primaryadvantage is that meteor burst does not use the ionospherefor the propagation of radio waves, the primary disadvantageis the limitation of throughput for voice communication.Then, the three areas of application-- long-rangecommunication, remote monitoring, and position monitoring--were described.

Chapter III presented the issues of meteor burstsurvivability under various adverse conditions, as comparedto traditional long range high frequency (HF) communication.Meteor burst is not affected as severely by ionosphericdisturbances as HF, can be continually operated underextreme physical conditions, and has an almost continuouspropagation medium.

In Chapter IV, the design criteria for theinteroperability of meteor burst equipment were presented,

53


64/75

along with highlights of some of the current technologicaltrends to improve performance. Meteor burst equipment isbeing designed to be compatible and interoperable with manycommunication systems and is in accordance with theCopernicus architectural guidelines that the Navy isimplementing. Trends to improve performance include the useof adaptive data rates, attempts to reduce artificial noise,the development of improved modulation techniques, and thedesign of "smart" antennas.

B. CONCLUSIONSMeteor burst communication is feasible, economical, and

highly survivable under many adverse conditions in bothpeacetime and war. There are many applications of thetechnology which are currently being used throughout theworld. As the frequency spectrum becomes more and morerestricted, it will be important to be able to sendinformation on a narrow band in a microburst.

Currently, meteor burst is delegated to secondary rolessuch as remote sensing, backup data transfer systems, andlow-priority communication nets for remote encampments.Applied research strives to improve meteor burstperformance, and once the restrictive issues of throughput,wait time, and artificial noise have been resolved, meteor

54


65/75

burst will be integrated into primary roles, such as voicecircuits, and become an integral part in Navalcommunications.

55


66/75

APPENDIX AGLOSSARY OF ABBREVIATIONS, ACRONYMS, AND TERMS

ANSI American National Standards InstituteARQ Automatic Repeat RequestB Bandwidth in HertzBER Bit Error RateCCITT Comit6 Consultatif International de T6lphoneet T616graphCOMSEC Communications SecurityCRC Cyclic Redundancy Checkd Distance in KilometersD D layer of the ionospheredB DecibeldBm Decibel-milliwattDEBPSK Differentially Encoded Binary Phase ShiftKeyingE E layer of the ionosphereEMP Electro-Magnetic Pulsef FrequencyF1 F1 layer of the ionosphereFCC Federal Communications CommissionFS Federal StandardFSK Frequency Shift KeyingFSPL Free Space Path LossHF High FrequencyHz Hertzk Boltzman's constantkbps Kilo-bits per secondKm KilometerKSR Keyboard Send and Receive terminalKw KilowattL Path losslog LogarithmLORAN Long Range Air NavigationLOS Line Of SightLUF Lowest usable frequencym MetersMBC Meteor Burst CommunicationsMCC Meteor Communications CorporationMHz Mega HertzMIL-STD Military StandardMUF Maximum usable frequencyN Noise (power)

56


67/75

NAK Negative AcKnowledgementNORAD North American Aerospace Defense CommandNRZ Non-Return to ZeroPCA Polar Cap AbsorptionPCs Personal ComputersPSK Phase Shift KeyingRF Radio FrequencySAC Strategic Air CommandSCS Soil Conservation ServiceSID Sudden Ionospheric DisturbanceSNOTEL Snow TelemetryT Temperature in Degrees KelvinVHF Very High FrequencyW Watts

57


68/75

APPENDIX B

i CO Z

- OnE 1 6

U.L) Z~O

'-0

Ix a. co

EEa

cc 0 "ZOi x- 0.a) T ,

Ir

Uo

z 0

03 * A.*- ~ oLAJ 7cc 0 0440soI

i-I - x

58


69/75

APPENDIX C

N -

Em m

I>, 0

Um I E1

59.


70/75

LIST OF REFERENCES1. "Meteor Communications Corporation," pamphlet publishedby Meteor Communications Corporation, Kent, Wa.2. Schanker, J. Z., Meteor Burst Communications, ArtechHouse, Inc., 1990.3. Freeman, R. L., Telecommunication TransmissionHandbook, 3rd ed., John Wiley & Sons, rnc., 1991.4. "U.S. CECOM DEMONSTRATION," pamphil t published byMeteor Communications Corporation, Kent, Wa.5. Oetting, J.D., "An Analysis of Meteor BurstCommunications for Military Applications," IEEETransactions on Communications, v.COM-2P, n. 9,September, 1980.6. Defense Communications Agency Center For Command AndControl And Communications Systems, Military Standard,MIL-STD-188-135, Interoperability and PerformanceStandards For Meteor Burst Communications-InitialCapability, 20 September 1988.7. Gray, G., "Meteor Burst Communications," Signal, May1982.8. Gottlieb, I., "Meteoric Bursts Could Keep Post-Attack

Communications Open," Defense Electronics, November1981.9. Schaefer, G.L., and Johnson, D.E., "Development andOperation Of The SNOTEL System In The Western UnitedSta-es, '' paper presented by the U.S. Soil ConservationService, Portland, Or., 1990.10. "Meteor Burst Communication," pamphlet published byMeteor Communications Corporation, Kent, Wa.11. Desourdis, R.I., Jr., and others, "Meteor Burst LinkPerformance Sensitivity to Antenna Pattern, Power

Margin and Range", Science Applications InternationalCorporation, 1988.

60


71/75

12. Coviello, G.J., and Lebow, I.L., "Preface, MilitaryCommunications- An Overview of the Special Issue," IEEETransactions on Communications, v. COM-28, n. 9,September 1980.13. Joint Chiefs of Staff, Department of Defense Dictionary

of Military and Associated Terms, (JCS PUB 1-02),December 1989.14. Smith, D.K., and Donich, T.G., "Maximizing ThroughputUnder Changing Channel Conditions", SIGNAL, June 1989.15. Livesey, R.J., "The Aurora," The MeteorologicalMagazine, Vol. 118, No. 1409, December 1989.16. Babcock, B.K., Electronic Communications Systems andthe Frequency Domain: An illustrated Primer for C3Students, Masters Thesis, Naval Postgraduate School,Monterey, Ca., June 1990.17. Smith, R., "Chapter 3. Ionosphere and HF propagation,"MR2419 notes, NPS, 1990.18. McIntosh, D., Meteorological Glossary, ChemicalPublishing Co., 1972.19. Parker, S., McGraw-Hill Dictionary Of Scientific AndTechnical Terms, 4th ed., McGraw-Hill, 1989.20. Schaefer, G.L., "SNOTEL- The World's First And LargestData Collection System Using Meteor Burst Technology,"paper presented at the International Symposium On The

Hydrological Basis For Water Resources Management,Beijing, China, October 23-26, 1990.21. The Office Of The Chief Of Naval Operations, NAVAIR-00-80U-24-I, Meteorology For Naval Aviators, Volume 1-Fundamentals, 1973.22. Gaynor, F. , Pocket Encyclopedia Of Atomic Energy,Jarrod and Sons, 1950.23. U.S. Atomic Energy Commission Nuclear Terms, 2nd ed.,Division of Technical Information, Washington, D.C.,1966.24. Morgan, E.J., "Meteor Burst Communications: An Update,"SIGNAL, March 1988.

61


72/75

25. National Communications System Office of Technology andStandards, "Proposed Federal Standard 1055,Telecommunications: Interoperability Requirements ForMeteor burst Radio Communications Between ConventionalMaster And Remote Stations," 17 December 1991.26. National Communications System Office of Technology andStandards, " Proposed Federal Standard 1056,Telecommunications: Interoperability Requirements ForThe Encryption of Meteoi Burst Radio Communications," 7October 1991.27. National Communications System Office of Technology andStandards, " Telecommunications: InteroperabilityRequirements For Meteor Burst Radio CommunicationsBetween Networks By Conventional Master Stations," 17December 1991.28. Telephone conversation between R. Bauman, DARPA, and

the author, 5 March 1992.29. Telephone conversation between T. Donich, MCC, and theauthor, 11 March 1992.

62


73/75

BIBLIOGRAPHYAkram, F., Sheikh, N., Javed A., and Grossi, M., "ImpulseResponse Of A MBC Channel Determined By Ray-tracingTechnology," IEEE Transactions On Communications, Vol COM-25, April 1977,Bailey, D., Bateman, R., Kirby, R., "Radio Transmission AtVHF By Scattering And Other Processes In The LowerIonosphere," Proceedings Of The IRE, Vol 43, No 10, October1955.Bartholome, P.J., and Vogt, I.M., "COMET-A New Meteor SystemIncorporating ARQ And Diversity Reception," IEEETransactions On Communication Technology, Vol COM-16, No 2,April 1968.Bartholome, P.J., and Vogt, I.M., "Design Concepts ForTransportable Ionoscatter Systems And Experimental Results,"IEEE Transactions On Communication Technology, Vol COM-15,No 6, December 1967.Bliss, W.H., Wagner, R.J., Wickizer, G.S., "Wide-bandFacsimile Transmission Over A 900-mile Path Utilizing MeteorIonization," IRE Transactions On Communications Systems, VolCS-7, No 4, December 1959.Bokhari, S.H., Javed, A., Grossi, M.D., "Data Storage ForAdaptive Meteor Scatter Communication," IEEE Transactions OnCommunication, Vol 23, No 3, March 1975.Brown, D.W., "A Physical Meteor Burst Propagation Model andSome Significant Results For Communication System Design,"IEEE Journal On Selected Areas In Communications, Vol SAC-3,September 1985.Campbell, L.L., and Hines, C.O., "Bandwidth ConsiderationsIn A JANET System," Proceedings Of The IRE, Vol 45, No 12,December 1957.Campbell, L.L., "Storage Capacity In A Burst TypeCommunication System," Proceedings Of The IRE, Vol 45, No12, December 1957.

63


74/75

Carpenter, R.J., and Ochs, G.P., "The NBS Meteor BurstCommunications System," IRE Transactions On CommunicationsSystems, Vol CS-7, No 4, December 1959.Crysdale, J.H., "Analysis Of The Performance Of TheEdmonton-Yellowknife JANET Circuit," IRE Transactions OnCommunications Systems, Vol CS-8, No 1, March 1960.Davis, G., Gladys, S., Lang, G., Luke, L., and Taylor, M.,"The Canadian JANET System," Proceedings of the IRE, Vol 45,No 12, December 1957.Eshleman, V.R., Mlodnosky, R.F., "DirectionalCharacteristics Of Meteor Propagation Derived From RadarMeasurements," Proceedings On The IRE, Vol 45, No-12,December 1957.Forsythe, P.A., Vogan, E.L., "The Principles Of JANET- AMeteor Burst Communication System," Proceedings Of The IRE,Vol 45, No-12, December 1957.JTAC, "Radio Transmission By Ionospheric And TroposphericScatter, Chapter Two," Proceedings Of The IRE, Vol 48, No 1,January 1960.Meeks, M.L., and James, J.C., "On The Influence Of Meteor-radiant Distributions In The Meteor-scatter Communication,"Proceedings Of The IRE, Vol 45, No 12, December 1957.Montgomery, G.F., and Sugar, G.R., "The Utility Of MeteorBursts For Intermittent Radio Communication," Proceedings OfThe IRE, Vol 45, No-12, December 1957.Rach, R.A., "An Investigation Of Storage Capacity RequiredFor A Meteor Burst Communication System," Proceedings Of TheIRE, Vol 45, No 12, December 1957.Vincent, W.R., Wolfram, R.T., Sifford, B.M., Jaye, W.E., andPeterson, A.M., "Analysis Of Oblique Path Meteor PropagationData From The Communications Viewpoint," Proceedings Of TheIRE, Vol 45, No-12, December 1957.

64


75/75

meteor burst communications- value in adverse conditions. naval postgrad school thesis. mark...

Documents