[Code of Federal Regulations]

[Title 47, Volume 2]

[Revised as of October 1, 2004]

From the U.S. Government Printing Office via GPO Access

[CITE: 47CFR24.253]



[Page 243-246]

 

                       TITLE 47--TELECOMMUNICATION

 

                    CHAPTER I--FEDERAL COMMUNICATIONS

                         COMMISSION (CONTINUED)

 

PART 24_PERSONAL COMMUNICATIONS SERVICES--Table of Contents

 

                         Subpart E_Broadband PCS

 

Sec. 24.253  Termination of cost-sharing obligations.



    The cost-sharing plan will sunset for all PCS entities on April 4, 

2005, which is ten years after the date that voluntary negotiations 

commenced for A and B block PCS entities. Those PCS entities that are 

paying their portion of relocation costs on an installment basis must 

continue the payments until the obligation is satisfied.



[61 FR 29693, June 12, 1996]



  Appendix I to Subpart E of Part 24--A Procedure for Calculating PCS 

   Signal Levels at Microwave Receivers (Appendix E of the Memorandum 

                           Opinion and Order)



    The new Rules adopted in Part 24 stipulate that estimates of 

interference to fixed microwave operations from a PCS operation will be 

based on the sum of signals received at a microwave receiver from the 

PCS operation. This appendix describes a procedure for computing this 

PCS level.

    In general, the procedure involves four steps:

    1. Determine the geographical coordinates of all microwave receivers 

operating on co-



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channel and adjacent frequencies within the coordination distance of 

each base station and the characteristics of each receiver, i.e., 

adjacent channel susceptibility, antenna gain, pattern and height, and 

line and other losses.

    2. Determine an equivalent isotropically radiated power (e.i.r.p.) 

for each base station and equivalent e.i.r.p. values for the mobiles and 

portables associated with each base station. Determine the values of 

pertinent correction and weighting factors based on building heights and 

density and distribution of portables. Close-in situations, prominent 

hills, and extra tall buildings require special treatment.

    3. Based on PCS e.i.r.p. values, correction and weighting factors, 

and microwave receiving system characteristics determined above, 

calculate the total interference power at the input of each microwave 

receiver, using the Longley-Rice propagation model.

    4. Based on the interference power level computed in step 3, 

determine interference to each microwave receiver using criteria 

described in Part 24 and EIA/TIA Bulletin 10-F.

    The interference from each base station and the mobiles and 

portables associated with it is calculated as follows:



Prbi=10Log (ptbi)-Lbi-

UCi+Gmwi-Ci-BPi

Prmi=10Log (nmixptmi)-Lmi-

UCi+Gmwi-Ci

Prpsi=10Log (npsixptpsi)-

Lpsi-UCi+Gmwi-Ci

Prpbi=10Log (npbixptpbi)-

Lpbi-UCi-(BPi-BHi) 

+Gmwi-Ci

Prpri=10Log (nprixptpri)-

Lpri-(UCi-BHi)+Gmwi-

Ci



where:



P refers to Power in dBm

p refers to power in milliwatts

Prbi=Power at MW receiver from ith base station in dBm

ptbi=e.i.r.p. transmitted from ith base station in 

milliwatts, which equals average power per channel x number of channels 

x antenna gain with respect to an isotropic antenna--line loss

Lbi=Path loss between MW and base station site in dB

UCi=Urban correction factor in dB

Gmwi=Gain of MW antenna in pertinent direction (dBi)

Ci=Channel discrimination of MW system in dB

Prmi=Power at MW receiver from mobiles associated with ith 

base station

ptmi=e.i.r.p. transmitted from mobiles associated with ith 

base station

nmi=Number of mobiles associated with ith base station

Lmi=Path loss between MW and mobile transmitters in dB

Prpsi=Power at MW receiver from outdoor portables (s for 

sidewalk)

ptpsi=e.i.r.p. transmitted from outdoor portables associated 

with ith base station

npsi=Number of outdoor portables associated with ith base 

station

Lpsi=Path loss between MW and outdoor portables in dB

Prpbi=Power at MW receiver from indoor portables (b for 

building)

ptpbi=e.i.r.p. transmitted from indoor portables associated 

with ith base station

npbi=number of indoor portables associated with ith base 

station

Lpbi=Path loss in dB between MW and base station site (using 

average building height divided by 2 as effective antenna height)

Prpri=Power at MW receiver from rooftop portables (r for 

rooftop)

ptpri=e.i.r.p. transmitted from rooftop portables associated 

with ith base station

npri=Number of rooftop portables associated with ith base 

station

Lpri=Path loss in dB between MW and base station site (using 

average building height as effective antenna height)

BPi=Building penetration loss at street level in dB

BHi=Height gain for portables in buildings dB=2.5x(nf-1), 

where nf is number of floors



    Note: where Ci varies from channel-to-channel, which 

often is the case, the summation process is more complex, requiring 

summation at a channel level first.



    Finally, the total PCS interference power at a given microwave 

receiver from all the base stations in a given frequency band is found 

by summing the contributions from the individual stations. Likewise, the 

total interference power at a given microwave receiver from all mobiles 

and portables operating in a given frequency band is found by summing 

the contributions from the mobiles and portables associated with each 

cell.

[GRAPHIC] [TIFF OMITTED] TR24JN94.017





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    Base Stations. Interference from each base station to each microwave 

should normally be considered independently. A group of base stations 

having more or less (within  50 percent) the same 

height above average terrain, the same e.i.r.p., basically the same path 

to a microwave receiving site, and subtending an angle to that receiving 

site of less than 5 degrees, may be treated as a group, using the total 

power of the group and the average antenna height of the group to 

calculate path loss, L.

    Mobile Stations. The e.i.r.p. from mobile transmitters is weighted 

according to the number of base station channels expected to be devoted 

to mobile operation at any given time. The antenna height of mobiles 

used in calculating path loss, L, is assumed to be 2 meters.

    Portable Stations. The e.i.r.p. from the portable units associated 

with each base station is weighted according to the estimated portion of 

portables associated with that cell expected to be operated inside 

buildings at any given time and the portion which could be expected to 

be operating from elevated locations, such as balconies or building 

rooftops. For example, in the case of service intended for business use 

in an urban area, one might expect that perhaps 85 percent of the 

portables in use at any given time would be operating from within 

buildings and perhaps 5 percent might be operating from rooftops or 

balconies. The remaining 10 percent would be outside at street level.

    Calculation of an equivalent e.i.r.p. for cells in suburban areas 

will involve different weighting criteria.

    Urban Correction Factor. The urban correction factor (UC) depends on 

the height and density of buildings surrounding a base station. For the 

core area of large cities, it is assumed to be 35 dB. For medium size 

cities and fringe areas of large cities (4- to 6-story buildings with 

scattered taller buildings and lower buildings and open spaces) it is 

assumed to be 25 dB; for small cities and towns, 15 dB, and for suburban 

residential areas (one- and two-story, single family houses with 

scattered multiple-story apartment buildings, shopping centers and open 

areas), 10 dB.

    The unadjusted urban correction factor, UC, should not be applied to 

base station antenna heights that are greater than 50 percent of the 

average building height for a cell.

    Building Height and Building Penetration Factors. The building 

height correction, BH, is a function of the average building height 

within the nominal coverage area of the base station. It is used in 

conjunction with the building penetration loss, BP, to adjust the 

expected interference contribution from that portion of the portables 

transmitting from within buildings. The adjustment is given by:



BP=20 dB in urban areas

BP=10 dB in suburban areas

BH=2.5x(nf-1) dB



where nf is the average height (number of floors) of the buildings in 

the area.

    (Note that this formula implies a net gain when the average building 

height is greater than 8 floors). All buildings more than twice the 

average height should be considered individually. The contribution to BH 

from that portion of portables in the building above the average 

building height should be increased by a factor of 20Log(h) dB, where h 

is the height of the portables above the average building height in 

meters.

    Channel Discrimination Factor. A factor based on the interference 

selectivity of the microwave receiver.

    Propagation Model. The PCS to microwave path loss, L, is calculated 

using the Longley-Rice propagation model, Version 1.2.2., in the point-

to-point mode. The Longley-Rice [1] model was derived from NBS Technical 

Note 101 [2], and updated in 1982 by Hufford [3]. Version 1.2.2 

incorporated modifications described in a letter by Hufford [4] in 1985. 

Terrain elevations used as input to the model should be from the U.S. 

Geological Survey 3-second digitized terrain database.

    Special Situations. If a cell size is large compared to the distance 

between the cell and a microwave receiving site so that it subtends an 

angle greater than 5 degrees, the cell should be subdivided and 

calculations should be based on the expected distribution of mobiles and 

portables within each subdivision.

    If terrain elevations within a cell differ by more than a factor of 

two-to-one, the cell should be subdivided and microwave interference 

calculations should be based on the average terrain elevation for each 

subdivision.

    If a co-channel PCS base station lies within the main beam of a 

microwave antenna (5 degrees), there is no 

intervening terrain obstructions, and the power at the microwave 

receiver from that base station, assuming free space propagation, would 

be 3 dB or less below the interference threshold, interference will be 

assumed to exist unless the PCS licensee can demonstrate otherwise by 

specific path loss calculations based on terrain and building losses.

    If any part of a cell or cell subdivision lies within the main beam 

of a co-channel microwave antenna, there is no intervening terrain 

obstructions, and the accumulative power of 5 percent or less of the 

mobiles, assuming free space propagation would be 3 dB or less below the 

interference threshold, interference will be assumed to exist unless the 

PCS licensee can demonstrate otherwise by specific path loss 

calculations based on terrain and building losses.



[[Page 246]]



    If a building within a cell or cell subdivision lies within the main 

beam of a co-channel microwave antenna, there is no intervening terrain 

obstructions, and the cumulative power of 5 percent or fewer of the 

portables, assuming free space propagation, would be 3 dB or less below 

the interference threshold, interference will be assumed to exist unless 

the PCS licensee can demonstrate otherwise by specific path loss 

calculations based on terrain and building losses.



                               References:



    1. Longley, A.G. and Rice, P.L., ``Prediction of Tropospheric Radio 

Transmission Loss Over Irregular Terrain, A Computer Method-1968'', ESSA 

Technical Report ERL 79-ITS 67, Institute for Telecommunications 

Sciences, July 1968.

    2. Rice, P.L. Longley, A.G., Norton, K.A., Barsis, A.P., 

``Transmission Loss Predictions for Tropospheric Communications 

Circuits,'' NBS Technical Note 101 (Revised), Volumes I and II, U.S. 

Department of Commerce, 1967.

    3. Hufford, G.A., Longley, A.G. and Kissick, W.A., ``A Guide to the 

use of the ITS Irregular Terrain Model in the Area Prediction Mode'', 

NTIA Report 82-100, U.S. Department of Commerce, April 1982. Also, 

Circular letter, dated January 30, 1985, from G.A. Hufford, identifying 

modifications to the computer program.

    4. Hufford, G.A., Memorandum to Users of the ITS Irregular Terrain 

Model, Institute for Telecommunications Sciences, U.S. Department of 

Commerce, January 30, 1985.